text: /*
   * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
   *
   * Licensed under the OpenSSL license (the "License").  You may not use
   * this file except in compliance with the License.  You can obtain a copy
   * in the file LICENSE in the source distribution or at
   * https://www.openssl.org/source/license.html
   */
  
  #include <stdio.h>
  #include <time.h>
  #include <errno.h>
  #include <limits.h>
  
  #include "internal/ctype.h"
  #include "internal/cryptlib.h"
  #include <openssl/crypto.h>
  #include <openssl/buffer.h>
  #include <openssl/evp.h>
  #include <openssl/asn1.h>
  #include <openssl/x509.h>
  #include <openssl/x509v3.h>
  #include <openssl/objects.h>
  #include "internal/dane.h"
  #include "internal/x509_int.h"
  #include "x509_lcl.h"
  
  /* CRL score values */
  
  /* No unhandled critical extensions */
  
  #define CRL_SCORE_NOCRITICAL    0x100
  
  /* certificate is within CRL scope */
  
  #define CRL_SCORE_SCOPE         0x080
  
  /* CRL times valid */
  
  #define CRL_SCORE_TIME          0x040
  
  /* Issuer name matches certificate */
  
  #define CRL_SCORE_ISSUER_NAME   0x020
  
  /* If this score or above CRL is probably valid */
  
  #define CRL_SCORE_VALID (CRL_SCORE_NOCRITICAL|CRL_SCORE_TIME|CRL_SCORE_SCOPE)
  
  /* CRL issuer is certificate issuer */
  
  #define CRL_SCORE_ISSUER_CERT   0x018
  
  /* CRL issuer is on certificate path */
  
  #define CRL_SCORE_SAME_PATH     0x008
  
  /* CRL issuer matches CRL AKID */
  
  #define CRL_SCORE_AKID          0x004
  
  /* Have a delta CRL with valid times */
  
  #define CRL_SCORE_TIME_DELTA    0x002
  
  static int build_chain(X509_STORE_CTX *ctx);
  static int verify_chain(X509_STORE_CTX *ctx);
  static int dane_verify(X509_STORE_CTX *ctx);
  static int null_callback(int ok, X509_STORE_CTX *e);
  static int check_issued(X509_STORE_CTX *ctx, X509 *x, X509 *issuer);
  static X509 *find_issuer(X509_STORE_CTX *ctx, STACK_OF(X509) *sk, X509 *x);
  static int check_chain_extensions(X509_STORE_CTX *ctx);
  static int check_name_constraints(X509_STORE_CTX *ctx);
  static int check_id(X509_STORE_CTX *ctx);
  static int check_trust(X509_STORE_CTX *ctx, int num_untrusted);
  static int check_revocation(X509_STORE_CTX *ctx);
  static int check_cert(X509_STORE_CTX *ctx);
  static int check_policy(X509_STORE_CTX *ctx);
  static int get_issuer_sk(X509 **issuer, X509_STORE_CTX *ctx, X509 *x);
  static int check_dane_issuer(X509_STORE_CTX *ctx, int depth);
  static int check_key_level(X509_STORE_CTX *ctx, X509 *cert);
  static int check_sig_level(X509_STORE_CTX *ctx, X509 *cert);
  
  static int get_crl_score(X509_STORE_CTX *ctx, X509 **pissuer,
                           unsigned int *preasons, X509_CRL *crl, X509 *x);
  static int get_crl_delta(X509_STORE_CTX *ctx,
                           X509_CRL **pcrl, X509_CRL **pdcrl, X509 *x);
  static void get_delta_sk(X509_STORE_CTX *ctx, X509_CRL **dcrl,
                           int *pcrl_score, X509_CRL *base,
                           STACK_OF(X509_CRL) *crls);
  static void crl_akid_check(X509_STORE_CTX *ctx, X509_CRL *crl, X509 **pissuer,
                             int *pcrl_score);
  static int crl_crldp_check(X509 *x, X509_CRL *crl, int crl_score,
                             unsigned int *preasons);
  static int check_crl_path(X509_STORE_CTX *ctx, X509 *x);
  static int check_crl_chain(X509_STORE_CTX *ctx,
                             STACK_OF(X509) *cert_path,
                             STACK_OF(X509) *crl_path);
  
  static int internal_verify(X509_STORE_CTX *ctx);
  
  static int null_callback(int ok, X509_STORE_CTX *e)
  {
      return ok;
  }
  
  /* Return 1 is a certificate is self signed */
  static int cert_self_signed(X509 *x)
  {
      /*
       * FIXME: x509v3_cache_extensions() needs to detect more failures and not
       * set EXFLAG_SET when that happens.  Especially, if the failures are
       * parse errors, rather than memory pressure!
       */
      X509_check_purpose(x, -1, 0);
      if (x->ex_flags & EXFLAG_SS)
          return 1;
      else
          return 0;
  }
  
  /* Given a certificate try and find an exact match in the store */
  
  static X509 *lookup_cert_match(X509_STORE_CTX *ctx, X509 *x)
  {
      STACK_OF(X509) *certs;
      X509 *xtmp = NULL;
      int i;
      /* Lookup all certs with matching subject name */
      certs = ctx->lookup_certs(ctx, X509_get_subject_name(x));
      if (certs == NULL)
          return NULL;
      /* Look for exact match */
      for (i = 0; i < sk_X509_num(certs); i++) {
          xtmp = sk_X509_value(certs, i);
          if (!X509_cmp(xtmp, x))
              break;
      }
      if (i < sk_X509_num(certs))
          X509_up_ref(xtmp);
      else
          xtmp = NULL;
      sk_X509_pop_free(certs, X509_free);
      return xtmp;
  }
  
  /*-
   * Inform the verify callback of an error.
   * If B<x> is not NULL it is the error cert, otherwise use the chain cert at
   * B<depth>.
   * If B<err> is not X509_V_OK, that's the error value, otherwise leave
   * unchanged (presumably set by the caller).
   *
   * Returns 0 to abort verification with an error, non-zero to continue.
   */
  static int verify_cb_cert(X509_STORE_CTX *ctx, X509 *x, int depth, int err)
  {
      ctx->error_depth = depth;
      ctx->current_cert = (x != NULL) ? x : sk_X509_value(ctx->chain, depth);
      if (err != X509_V_OK)
          ctx->error = err;
      return ctx->verify_cb(0, ctx);
  }
  
  /*-
   * Inform the verify callback of an error, CRL-specific variant.  Here, the
   * error depth and certificate are already set, we just specify the error
   * number.
   *
   * Returns 0 to abort verification with an error, non-zero to continue.
   */
  static int verify_cb_crl(X509_STORE_CTX *ctx, int err)
  {
      ctx->error = err;
      return ctx->verify_cb(0, ctx);
  }
  
  static int check_auth_level(X509_STORE_CTX *ctx)
  {
      int i;
      int num = sk_X509_num(ctx->chain);
  
      if (ctx->param->auth_level <= 0)
          return 1;
  
      for (i = 0; i < num; ++i) {
          X509 *cert = sk_X509_value(ctx->chain, i);
  
          /*
           * We've already checked the security of the leaf key, so here we only
           * check the security of issuer keys.
           */
          if (i > 0 && !check_key_level(ctx, cert) &&
              verify_cb_cert(ctx, cert, i, X509_V_ERR_CA_KEY_TOO_SMALL) == 0)
              return 0;
          /*
           * We also check the signature algorithm security of all certificates
           * except those of the trust anchor at index num-1.
           */
          if (i < num - 1 && !check_sig_level(ctx, cert) &&
              verify_cb_cert(ctx, cert, i, X509_V_ERR_CA_MD_TOO_WEAK) == 0)
              return 0;
      }
      return 1;
  }
  
  static int verify_chain(X509_STORE_CTX *ctx)
  {
      int err;
      int ok;
  
      /*
       * Before either returning with an error, or continuing with CRL checks,
       * instantiate chain public key parameters.
       */
      if ((ok = build_chain(ctx)) == 0 ||
          (ok = check_chain_extensions(ctx)) == 0 ||
          (ok = check_auth_level(ctx)) == 0 ||
          (ok = check_id(ctx)) == 0 || 1)
          X509_get_pubkey_parameters(NULL, ctx->chain);
      if (ok == 0 || (ok = ctx->check_revocation(ctx)) == 0)
          return ok;
  
      err = X509_chain_check_suiteb(&ctx->error_depth, NULL, ctx->chain,
                                    ctx->param->flags);
      if (err != X509_V_OK) {
          if ((ok = verify_cb_cert(ctx, NULL, ctx->error_depth, err)) == 0)
              return ok;
      }
  
      /* Verify chain signatures and expiration times */
      ok = (ctx->verify != NULL) ? ctx->verify(ctx) : internal_verify(ctx);
      if (!ok)
          return ok;
  
      if ((ok = check_name_constraints(ctx)) == 0)
          return ok;
  
  #ifndef OPENSSL_NO_RFC3779
      /* RFC 3779 path validation, now that CRL check has been done */
      if ((ok = X509v3_asid_validate_path(ctx)) == 0)
          return ok;
      if ((ok = X509v3_addr_validate_path(ctx)) == 0)
          return ok;
  #endif
  
      /* If we get this far evaluate policies */
      if (ctx->param->flags & X509_V_FLAG_POLICY_CHECK)
          ok = ctx->check_policy(ctx);
      return ok;
  }
  
  int X509_verify_cert(X509_STORE_CTX *ctx)
  {
      SSL_DANE *dane = ctx->dane;
      int ret;
  
      if (ctx->cert == NULL) {
          X509err(X509_F_X509_VERIFY_CERT, X509_R_NO_CERT_SET_FOR_US_TO_VERIFY);
          ctx->error = X509_V_ERR_INVALID_CALL;
          return -1;
      }
  
      if (ctx->chain != NULL) {
          /*
           * This X509_STORE_CTX has already been used to verify a cert. We
           * cannot do another one.
           */
          X509err(X509_F_X509_VERIFY_CERT, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
          ctx->error = X509_V_ERR_INVALID_CALL;
          return -1;
      }
  
      /*
       * first we make sure the chain we are going to build is present and that
       * the first entry is in place
       */
      if (((ctx->chain = sk_X509_new_null()) == NULL) ||
          (!sk_X509_push(ctx->chain, ctx->cert))) {
          X509err(X509_F_X509_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
          ctx->error = X509_V_ERR_OUT_OF_MEM;
          return -1;
      }
      X509_up_ref(ctx->cert);
      ctx->num_untrusted = 1;
  
      /* If the peer's public key is too weak, we can stop early. */
      if (!check_key_level(ctx, ctx->cert) &&
          !verify_cb_cert(ctx, ctx->cert, 0, X509_V_ERR_EE_KEY_TOO_SMALL))
          return 0;
  
      if (DANETLS_ENABLED(dane))
          ret = dane_verify(ctx);
      else
          ret = verify_chain(ctx);
  
      /*
       * Safety-net.  If we are returning an error, we must also set ctx->error,
       * so that the chain is not considered verified should the error be ignored
       * (e.g. TLS with SSL_VERIFY_NONE).
       */
      if (ret <= 0 && ctx->error == X509_V_OK)
          ctx->error = X509_V_ERR_UNSPECIFIED;
      return ret;
  }
  
  /*
   * Given a STACK_OF(X509) find the issuer of cert (if any)
   */
  static X509 *find_issuer(X509_STORE_CTX *ctx, STACK_OF(X509) *sk, X509 *x)
  {
      int i;
      X509 *issuer, *rv = NULL;
  
      for (i = 0; i < sk_X509_num(sk); i++) {
          issuer = sk_X509_value(sk, i);
          if (ctx->check_issued(ctx, x, issuer)) {
              rv = issuer;
              if (x509_check_cert_time(ctx, rv, -1))
                  break;
          }
      }
      return rv;
  }
  
  /* Given a possible certificate and issuer check them */
  
  static int check_issued(X509_STORE_CTX *ctx, X509 *x, X509 *issuer)
  {
      int ret;
      if (x == issuer)
          return cert_self_signed(x);
      ret = X509_check_issued(issuer, x);
      if (ret == X509_V_OK) {
          int i;
          X509 *ch;
          /* Special case: single self signed certificate */
          if (cert_self_signed(x) && sk_X509_num(ctx->chain) == 1)
              return 1;
          for (i = 0; i < sk_X509_num(ctx->chain); i++) {
              ch = sk_X509_value(ctx->chain, i);
              if (ch == issuer || !X509_cmp(ch, issuer)) {
                  ret = X509_V_ERR_PATH_LOOP;
                  break;
              }
          }
      }
  
      return (ret == X509_V_OK);
  }
  
  /* Alternative lookup method: look from a STACK stored in other_ctx */
  
  static int get_issuer_sk(X509 **issuer, X509_STORE_CTX *ctx, X509 *x)
  {
      *issuer = find_issuer(ctx, ctx->other_ctx, x);
      if (*issuer) {
          X509_up_ref(*issuer);
          return 1;
      } else
          return 0;
  }
  
  static STACK_OF(X509) *lookup_certs_sk(X509_STORE_CTX *ctx, X509_NAME *nm)
  {
      STACK_OF(X509) *sk = NULL;
      X509 *x;
      int i;
  
      for (i = 0; i < sk_X509_num(ctx->other_ctx); i++) {
          x = sk_X509_value(ctx->other_ctx, i);
          if (X509_NAME_cmp(nm, X509_get_subject_name(x)) == 0) {
              if (sk == NULL)
                  sk = sk_X509_new_null();
              if (sk == NULL || sk_X509_push(sk, x) == 0) {
                  sk_X509_pop_free(sk, X509_free);
                  X509err(X509_F_LOOKUP_CERTS_SK, ERR_R_MALLOC_FAILURE);
                  ctx->error = X509_V_ERR_OUT_OF_MEM;
                  return NULL;
              }
              X509_up_ref(x);
          }
      }
      return sk;
  }
  
  /*
   * Check EE or CA certificate purpose.  For trusted certificates explicit local
   * auxiliary trust can be used to override EKU-restrictions.
   */
  static int check_purpose(X509_STORE_CTX *ctx, X509 *x, int purpose, int depth,
                           int must_be_ca)
  {
      int tr_ok = X509_TRUST_UNTRUSTED;
  
      /*
       * For trusted certificates we want to see whether any auxiliary trust
       * settings trump the purpose constraints.
       *
       * This is complicated by the fact that the trust ordinals in
       * ctx->param->trust are entirely independent of the purpose ordinals in
       * ctx->param->purpose!
       *
       * What connects them is their mutual initialization via calls from
       * X509_STORE_CTX_set_default() into X509_VERIFY_PARAM_lookup() which sets
       * related values of both param->trust and param->purpose.  It is however
       * typically possible to infer associated trust values from a purpose value
       * via the X509_PURPOSE API.
       *
       * Therefore, we can only check for trust overrides when the purpose we're
       * checking is the same as ctx->param->purpose and ctx->param->trust is
       * also set.
       */
      if (depth >= ctx->num_untrusted && purpose == ctx->param->purpose)
          tr_ok = X509_check_trust(x, ctx->param->trust, X509_TRUST_NO_SS_COMPAT);
  
      switch (tr_ok) {
      case X509_TRUST_TRUSTED:
          return 1;
      case X509_TRUST_REJECTED:
          break;
      default:
          switch (X509_check_purpose(x, purpose, must_be_ca > 0)) {
          case 1:
              return 1;
          case 0:
              break;
          default:
              if ((ctx->param->flags & X509_V_FLAG_X509_STRICT) == 0)
                  return 1;
          }
          break;
      }
  
      return verify_cb_cert(ctx, x, depth, X509_V_ERR_INVALID_PURPOSE);
  }
  
  /*
   * Check a certificate chains extensions for consistency with the supplied
   * purpose
   */
  
  static int check_chain_extensions(X509_STORE_CTX *ctx)
  {
      int i, must_be_ca, plen = 0;
      X509 *x;
      int proxy_path_length = 0;
      int purpose;
      int allow_proxy_certs;
      int num = sk_X509_num(ctx->chain);
  
      /*-
       *  must_be_ca can have 1 of 3 values:
       * -1: we accept both CA and non-CA certificates, to allow direct
       *     use of self-signed certificates (which are marked as CA).
       * 0:  we only accept non-CA certificates.  This is currently not
       *     used, but the possibility is present for future extensions.
       * 1:  we only accept CA certificates.  This is currently used for
       *     all certificates in the chain except the leaf certificate.
       */
      must_be_ca = -1;
  
      /* CRL path validation */
      if (ctx->parent) {
          allow_proxy_certs = 0;
          purpose = X509_PURPOSE_CRL_SIGN;
      } else {
          allow_proxy_certs =
              ! !(ctx->param->flags & X509_V_FLAG_ALLOW_PROXY_CERTS);
          purpose = ctx->param->purpose;
      }
  
      for (i = 0; i < num; i++) {
          int ret;
          x = sk_X509_value(ctx->chain, i);
          if (!(ctx->param->flags & X509_V_FLAG_IGNORE_CRITICAL)
              && (x->ex_flags & EXFLAG_CRITICAL)) {
              if (!verify_cb_cert(ctx, x, i,
                                  X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION))
                  return 0;
          }
          if (!allow_proxy_certs && (x->ex_flags & EXFLAG_PROXY)) {
              if (!verify_cb_cert(ctx, x, i,
                                  X509_V_ERR_PROXY_CERTIFICATES_NOT_ALLOWED))
                  return 0;
          }
          ret = X509_check_ca(x);
          switch (must_be_ca) {
          case -1:
              if ((ctx->param->flags & X509_V_FLAG_X509_STRICT)
                  && (ret != 1) && (ret != 0)) {
                  ret = 0;
                  ctx->error = X509_V_ERR_INVALID_CA;
              } else
                  ret = 1;
              break;
          case 0:
              if (ret != 0) {
                  ret = 0;
                  ctx->error = X509_V_ERR_INVALID_NON_CA;
              } else
                  ret = 1;
              break;
          default:
              /* X509_V_FLAG_X509_STRICT is implicit for intermediate CAs */
              if ((ret == 0)
                  || ((i + 1 < num || ctx->param->flags & X509_V_FLAG_X509_STRICT)
                      && (ret != 1))) {
                  ret = 0;
                  ctx->error = X509_V_ERR_INVALID_CA;
              } else
                  ret = 1;
              break;
          }
          if (ret == 0 && !verify_cb_cert(ctx, x, i, X509_V_OK))
              return 0;
          /* check_purpose() makes the callback as needed */
          if (purpose > 0 && !check_purpose(ctx, x, purpose, i, must_be_ca))
              return 0;
          /* Check pathlen if not self issued */
          if ((i > 1) && !(x->ex_flags & EXFLAG_SI)
              && (x->ex_pathlen != -1)
              && (plen > (x->ex_pathlen + proxy_path_length + 1))) {
              if (!verify_cb_cert(ctx, x, i, X509_V_ERR_PATH_LENGTH_EXCEEDED))
                  return 0;
          }
          /* Increment path length if not self issued */
          if (!(x->ex_flags & EXFLAG_SI))
              plen++;
          /*
           * If this certificate is a proxy certificate, the next certificate
           * must be another proxy certificate or a EE certificate.  If not,
           * the next certificate must be a CA certificate.
           */
          if (x->ex_flags & EXFLAG_PROXY) {
              /*
               * RFC3820, 4.1.3 (b)(1) stipulates that if pCPathLengthConstraint
               * is less than max_path_length, the former should be copied to
               * the latter, and 4.1.4 (a) stipulates that max_path_length
               * should be verified to be larger than zero and decrement it.
               *
               * Because we're checking the certs in the reverse order, we start
               * with verifying that proxy_path_length isn't larger than pcPLC,
               * and copy the latter to the former if it is, and finally,
               * increment proxy_path_length.
               */
              if (x->ex_pcpathlen != -1) {
                  if (proxy_path_length > x->ex_pcpathlen) {
                      if (!verify_cb_cert(ctx, x, i,
                                          X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED))
                          return 0;
                  }
                  proxy_path_length = x->ex_pcpathlen;
              }
              proxy_path_length++;
              must_be_ca = 0;
          } else
              must_be_ca = 1;
      }
      return 1;
  }
  
  static int check_name_constraints(X509_STORE_CTX *ctx)
  {
      int i;
  
      /* Check name constraints for all certificates */
      for (i = sk_X509_num(ctx->chain) - 1; i >= 0; i--) {
          X509 *x = sk_X509_value(ctx->chain, i);
          int j;
  
          /* Ignore self issued certs unless last in chain */
          if (i && (x->ex_flags & EXFLAG_SI))
              continue;
  
          /*
           * Proxy certificates policy has an extra constraint, where the
           * certificate subject MUST be the issuer with a single CN entry
           * added.
           * (RFC 3820: 3.4, 4.1.3 (a)(4))
           */
          if (x->ex_flags & EXFLAG_PROXY) {
              X509_NAME *tmpsubject = X509_get_subject_name(x);
              X509_NAME *tmpissuer = X509_get_issuer_name(x);
              X509_NAME_ENTRY *tmpentry = NULL;
              int last_object_nid = 0;
              int err = X509_V_OK;
              int last_object_loc = X509_NAME_entry_count(tmpsubject) - 1;
  
              /* Check that there are at least two RDNs */
              if (last_object_loc < 1) {
                  err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;
                  goto proxy_name_done;
              }
  
              /*
               * Check that there is exactly one more RDN in subject as
               * there is in issuer.
               */
              if (X509_NAME_entry_count(tmpsubject)
                  != X509_NAME_entry_count(tmpissuer) + 1) {
                  err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;
                  goto proxy_name_done;
              }
  
              /*
               * Check that the last subject component isn't part of a
               * multivalued RDN
               */
              if (X509_NAME_ENTRY_set(X509_NAME_get_entry(tmpsubject,
                                                          last_object_loc))
                  == X509_NAME_ENTRY_set(X509_NAME_get_entry(tmpsubject,
                                                             last_object_loc - 1))) {
                  err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;
                  goto proxy_name_done;
              }
  
              /*
               * Check that the last subject RDN is a commonName, and that
               * all the previous RDNs match the issuer exactly
               */
              tmpsubject = X509_NAME_dup(tmpsubject);
              if (tmpsubject == NULL) {
                  X509err(X509_F_CHECK_NAME_CONSTRAINTS, ERR_R_MALLOC_FAILURE);
                  ctx->error = X509_V_ERR_OUT_OF_MEM;
                  return 0;
              }
  
              tmpentry =
                  X509_NAME_delete_entry(tmpsubject, last_object_loc);
              last_object_nid =
                  OBJ_obj2nid(X509_NAME_ENTRY_get_object(tmpentry));
  
              if (last_object_nid != NID_commonName
                  || X509_NAME_cmp(tmpsubject, tmpissuer) != 0) {
                  err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;
              }
  
              X509_NAME_ENTRY_free(tmpentry);
              X509_NAME_free(tmpsubject);
  
           proxy_name_done:
              if (err != X509_V_OK
                  && !verify_cb_cert(ctx, x, i, err))
                  return 0;
          }
  
          /*
           * Check against constraints for all certificates higher in chain
           * including trust anchor. Trust anchor not strictly speaking needed
           * but if it includes constraints it is to be assumed it expects them
           * to be obeyed.
           */
          for (j = sk_X509_num(ctx->chain) - 1; j > i; j--) {
              NAME_CONSTRAINTS *nc = sk_X509_value(ctx->chain, j)->nc;
  
              if (nc) {
                  int rv = NAME_CONSTRAINTS_check(x, nc);
  
                  /* If EE certificate check commonName too */
                  if (rv == X509_V_OK && i == 0)
                      rv = NAME_CONSTRAINTS_check_CN(x, nc);
  
                  switch (rv) {
                  case X509_V_OK:
                      break;
                  case X509_V_ERR_OUT_OF_MEM:
                      return 0;
                  default:
                      if (!verify_cb_cert(ctx, x, i, rv))
                          return 0;
                      break;
                  }
              }
          }
      }
      return 1;
  }
  
  static int check_id_error(X509_STORE_CTX *ctx, int errcode)
  {
      return verify_cb_cert(ctx, ctx->cert, 0, errcode);
  }
  
  static int check_hosts(X509 *x, X509_VERIFY_PARAM *vpm)
  {
      int i;
      int n = sk_OPENSSL_STRING_num(vpm->hosts);
      char *name;
  
      if (vpm->peername != NULL) {
          OPENSSL_free(vpm->peername);
          vpm->peername = NULL;
      }
      for (i = 0; i < n; ++i) {
          name = sk_OPENSSL_STRING_value(vpm->hosts, i);
          if (X509_check_host(x, name, 0, vpm->hostflags, &vpm->peername) > 0)
              return 1;
      }
      return n == 0;
  }
  
  static int check_id(X509_STORE_CTX *ctx)
  {
      X509_VERIFY_PARAM *vpm = ctx->param;
      X509 *x = ctx->cert;
      if (vpm->hosts && check_hosts(x, vpm) <= 0) {
          if (!check_id_error(ctx, X509_V_ERR_HOSTNAME_MISMATCH))
              return 0;
      }
      if (vpm->email && X509_check_email(x, vpm->email, vpm->emaillen, 0) <= 0) {
          if (!check_id_error(ctx, X509_V_ERR_EMAIL_MISMATCH))
              return 0;
      }
      if (vpm->ip && X509_check_ip(x, vpm->ip, vpm->iplen, 0) <= 0) {
          if (!check_id_error(ctx, X509_V_ERR_IP_ADDRESS_MISMATCH))
              return 0;
      }
      return 1;
  }
  
  static int check_trust(X509_STORE_CTX *ctx, int num_untrusted)
  {
      int i;
      X509 *x = NULL;
      X509 *mx;
      SSL_DANE *dane = ctx->dane;
      int num = sk_X509_num(ctx->chain);
      int trust;
  
      /*
       * Check for a DANE issuer at depth 1 or greater, if it is a DANE-TA(2)
       * match, we're done, otherwise we'll merely record the match depth.
       */
      if (DANETLS_HAS_TA(dane) && num_untrusted > 0 && num_untrusted < num) {
          switch (trust = check_dane_issuer(ctx, num_untrusted)) {
          case X509_TRUST_TRUSTED:
          case X509_TRUST_REJECTED:
              return trust;
          }
      }
  
      /*
       * Check trusted certificates in chain at depth num_untrusted and up.
       * Note, that depths 0..num_untrusted-1 may also contain trusted
       * certificates, but the caller is expected to have already checked those,
       * and wants to incrementally check just any added since.
       */
      for (i = num_untrusted; i < num; i++) {
          x = sk_X509_value(ctx->chain, i);
          trust = X509_check_trust(x, ctx->param->trust, 0);
          /* If explicitly trusted return trusted */
          if (trust == X509_TRUST_TRUSTED)
              goto trusted;
          if (trust == X509_TRUST_REJECTED)
              goto rejected;
      }
  
      /*
       * If we are looking at a trusted certificate, and accept partial chains,
       * the chain is PKIX trusted.
       */
      if (num_untrusted < num) {
          if (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN)
              goto trusted;
          return X509_TRUST_UNTRUSTED;
      }
  
      if (num_untrusted == num && ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN) {
          /*
           * Last-resort call with no new trusted certificates, check the leaf
           * for a direct trust store match.
           */
          i = 0;
          x = sk_X509_value(ctx->chain, i);
          mx = lookup_cert_match(ctx, x);
          if (!mx)
              return X509_TRUST_UNTRUSTED;
  
          /*
           * Check explicit auxiliary trust/reject settings.  If none are set,
           * we'll accept X509_TRUST_UNTRUSTED when not self-signed.
           */
          trust = X509_check_trust(mx, ctx->param->trust, 0);
          if (trust == X509_TRUST_REJECTED) {
              X509_free(mx);
              goto rejected;
          }
  
          /* Replace leaf with trusted match */
          (void) sk_X509_set(ctx->chain, 0, mx);
          X509_free(x);
          ctx->num_untrusted = 0;
          goto trusted;
      }
  
      /*
       * If no trusted certs in chain at all return untrusted and allow
       * standard (no issuer cert) etc errors to be indicated.
       */
      return X509_TRUST_UNTRUSTED;
  
   rejected:
      if (!verify_cb_cert(ctx, x, i, X509_V_ERR_CERT_REJECTED))
          return X509_TRUST_REJECTED;
      return X509_TRUST_UNTRUSTED;
  
   trusted:
      if (!DANETLS_ENABLED(dane))
          return X509_TRUST_TRUSTED;
      if (dane->pdpth < 0)
          dane->pdpth = num_untrusted;
      /* With DANE, PKIX alone is not trusted until we have both */
      if (dane->mdpth >= 0)
          return X509_TRUST_TRUSTED;
      return X509_TRUST_UNTRUSTED;
  }
  
  static int check_revocation(X509_STORE_CTX *ctx)
  {
      int i = 0, last = 0, ok = 0;
      if (!(ctx->param->flags & X509_V_FLAG_CRL_CHECK))
          return 1;
      if (ctx->param->flags & X509_V_FLAG_CRL_CHECK_ALL)
          last = sk_X509_num(ctx->chain) - 1;
      else {
          /* If checking CRL paths this isn't the EE certificate */
          if (ctx->parent)
              return 1;
          last = 0;
      }
      for (i = 0; i <= last; i++) {
          ctx->error_depth = i;
          ok = check_cert(ctx);
          if (!ok)
              return ok;
      }
      return 1;
  }
  
  static int check_cert(X509_STORE_CTX *ctx)
  {
      X509_CRL *crl = NULL, *dcrl = NULL;
      int ok = 0;
      int cnum = ctx->error_depth;
      X509 *x = sk_X509_value(ctx->chain, cnum);
  
      ctx->current_cert = x;
      ctx->current_issuer = NULL;
      ctx->current_crl_score = 0;
      ctx->current_reasons = 0;
  
      if (x->ex_flags & EXFLAG_PROXY)
          return 1;
  
      while (ctx->current_reasons != CRLDP_ALL_REASONS) {
          unsigned int last_reasons = ctx->current_reasons;
  
          /* Try to retrieve relevant CRL */
          if (ctx->get_crl)
              ok = ctx->get_crl(ctx, &crl, x);
          else
              ok = get_crl_delta(ctx, &crl, &dcrl, x);
          /*
           * If error looking up CRL, nothing we can do except notify callback
           */
          if (!ok) {
              ok = verify_cb_crl(ctx, X509_V_ERR_UNABLE_TO_GET_CRL);
              goto done;
          }
          ctx->current_crl = crl;
          ok = ctx->check_crl(ctx, crl);
          if (!ok)
              goto done;
  
          if (dcrl) {
              ok = ctx->check_crl(ctx, dcrl);
              if (!ok)
                  goto done;
              ok = ctx->cert_crl(ctx, dcrl, x);
              if (!ok)
                  goto done;
          } else
              ok = 1;
  
          /* Don't look in full CRL if delta reason is removefromCRL */
          if (ok != 2) {
              ok = ctx->cert_crl(ctx, crl, x);
              if (!ok)
                  goto done;
          }
  
          X509_CRL_free(crl);
          X509_CRL_free(dcrl);
          crl = NULL;
          dcrl = NULL;
          /*
           * If reasons not updated we won't get anywhere by another iteration,
           * so exit loop.
           */
          if (last_reasons == ctx->current_reasons) {
              ok = verify_cb_crl(ctx, X509_V_ERR_UNABLE_TO_GET_CRL);
              goto done;
          }
      }
   done:
      X509_CRL_free(crl);
      X509_CRL_free(dcrl);
  
      ctx->current_crl = NULL;
      return ok;
  }
  
  /* Check CRL times against values in X509_STORE_CTX */
  
  static int check_crl_time(X509_STORE_CTX *ctx, X509_CRL *crl, int notify)
  {
      time_t *ptime;
      int i;
  
      if (notify)
          ctx->current_crl = crl;
      if (ctx->param->flags & X509_V_FLAG_USE_CHECK_TIME)
          ptime = &ctx->param->check_time;
      else if (ctx->param->flags & X509_V_FLAG_NO_CHECK_TIME)
          return 1;
      else
          ptime = NULL;
  
      i = X509_cmp_time(X509_CRL_get0_lastUpdate(crl), ptime);
      if (i == 0) {
          if (!notify)
              return 0;
          if (!verify_cb_crl(ctx, X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD))
              return 0;
      }
  
      if (i > 0) {
          if (!notify)
              return 0;
          if (!verify_cb_crl(ctx, X509_V_ERR_CRL_NOT_YET_VALID))
              return 0;
      }
  
      if (X509_CRL_get0_nextUpdate(crl)) {
          i = X509_cmp_time(X509_CRL_get0_nextUpdate(crl), ptime);
  
          if (i == 0) {
              if (!notify)
                  return 0;
              if (!verify_cb_crl(ctx, X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD))
                  return 0;
          }
          /* Ignore expiry of base CRL is delta is valid */
          if ((i < 0) && !(ctx->current_crl_score & CRL_SCORE_TIME_DELTA)) {
              if (!notify)
                  return 0;
              if (!verify_cb_crl(ctx, X509_V_ERR_CRL_HAS_EXPIRED))
                  return 0;
          }
      }
  
      if (notify)
          ctx->current_crl = NULL;
  
      return 1;
  }
  
  static int get_crl_sk(X509_STORE_CTX *ctx, X509_CRL **pcrl, X509_CRL **pdcrl,
                        X509 **pissuer, int *pscore, unsigned int *preasons,
                        STACK_OF(X509_CRL) *crls)
  {
      int i, crl_score, best_score = *pscore;
      unsigned int reasons, best_reasons = 0;
      X509 *x = ctx->current_cert;
      X509_CRL *crl, *best_crl = NULL;
      X509 *crl_issuer = NULL, *best_crl_issuer = NULL;
  
      for (i = 0; i < sk_X509_CRL_num(crls); i++) {
          crl = sk_X509_CRL_value(crls, i);
          reasons = *preasons;
          crl_score = get_crl_score(ctx, &crl_issuer, &reasons, crl, x);
          if (crl_score < best_score || crl_score == 0)
              continue;
          /* If current CRL is equivalent use it if it is newer */
          if (crl_score == best_score && best_crl != NULL) {
              int day, sec;
              if (ASN1_TIME_diff(&day, &sec, X509_CRL_get0_lastUpdate(best_crl),
                                 X509_CRL_get0_lastUpdate(crl)) == 0)
                  continue;
              /*
               * ASN1_TIME_diff never returns inconsistent signs for |day|
               * and |sec|.
               */
              if (day <= 0 && sec <= 0)
                  continue;
          }
          best_crl = crl;
          best_crl_issuer = crl_issuer;
          best_score = crl_score;
          best_reasons = reasons;
      }
  
      if (best_crl) {
          X509_CRL_free(*pcrl);
          *pcrl = best_crl;
          *pissuer = best_crl_issuer;
          *pscore = best_score;
          *preasons = best_reasons;
          X509_CRL_up_ref(best_crl);
          X509_CRL_free(*pdcrl);
          *pdcrl = NULL;
          get_delta_sk(ctx, pdcrl, pscore, best_crl, crls);
      }
  
      if (best_score >= CRL_SCORE_VALID)
          return 1;
  
      return 0;
  }
  
  /*
   * Compare two CRL extensions for delta checking purposes. They should be
   * both present or both absent. If both present all fields must be identical.
   */
  
  static int crl_extension_match(X509_CRL *a, X509_CRL *b, int nid)
  {
      ASN1_OCTET_STRING *exta, *extb;
      int i;
      i = X509_CRL_get_ext_by_NID(a, nid, -1);
      if (i >= 0) {
          /* Can't have multiple occurrences */
          if (X509_CRL_get_ext_by_NID(a, nid, i) != -1)
              return 0;
          exta = X509_EXTENSION_get_data(X509_CRL_get_ext(a, i));
      } else
          exta = NULL;
  
      i = X509_CRL_get_ext_by_NID(b, nid, -1);
  
      if (i >= 0) {
  
          if (X509_CRL_get_ext_by_NID(b, nid, i) != -1)
              return 0;
          extb = X509_EXTENSION_get_data(X509_CRL_get_ext(b, i));
      } else
          extb = NULL;
  
      if (!exta && !extb)
          return 1;
  
      if (!exta || !extb)
          return 0;
  
      if (ASN1_OCTET_STRING_cmp(exta, extb))
          return 0;
  
      return 1;
  }
  
  /* See if a base and delta are compatible */
  
  static int check_delta_base(X509_CRL *delta, X509_CRL *base)
  {
      /* Delta CRL must be a delta */
      if (!delta->base_crl_number)
          return 0;
      /* Base must have a CRL number */
      if (!base->crl_number)
          return 0;
      /* Issuer names must match */
      if (X509_NAME_cmp(X509_CRL_get_issuer(base), X509_CRL_get_issuer(delta)))
          return 0;
      /* AKID and IDP must match */
      if (!crl_extension_match(delta, base, NID_authority_key_identifier))
          return 0;
      if (!crl_extension_match(delta, base, NID_issuing_distribution_point))
          return 0;
      /* Delta CRL base number must not exceed Full CRL number. */
      if (ASN1_INTEGER_cmp(delta->base_crl_number, base->crl_number) > 0)
          return 0;
      /* Delta CRL number must exceed full CRL number */
      if (ASN1_INTEGER_cmp(delta->crl_number, base->crl_number) > 0)
          return 1;
      return 0;
  }
  
  /*
   * For a given base CRL find a delta... maybe extend to delta scoring or
   * retrieve a chain of deltas...
   */
  
  static void get_delta_sk(X509_STORE_CTX *ctx, X509_CRL **dcrl, int *pscore,
                           X509_CRL *base, STACK_OF(X509_CRL) *crls)
  {
      X509_CRL *delta;
      int i;
      if (!(ctx->param->flags & X509_V_FLAG_USE_DELTAS))
          return;
      if (!((ctx->current_cert->ex_flags | base->flags) & EXFLAG_FRESHEST))
          return;
      for (i = 0; i < sk_X509_CRL_num(crls); i++) {
          delta = sk_X509_CRL_value(crls, i);
          if (check_delta_base(delta, base)) {
              if (check_crl_time(ctx, delta, 0))
                  *pscore |= CRL_SCORE_TIME_DELTA;
              X509_CRL_up_ref(delta);
              *dcrl = delta;
              return;
          }
      }
      *dcrl = NULL;
  }
  
  /*
   * For a given CRL return how suitable it is for the supplied certificate
   * 'x'. The return value is a mask of several criteria. If the issuer is not
   * the certificate issuer this is returned in *pissuer. The reasons mask is
   * also used to determine if the CRL is suitable: if no new reasons the CRL
   * is rejected, otherwise reasons is updated.
   */
  
  static int get_crl_score(X509_STORE_CTX *ctx, X509 **pissuer,
                           unsigned int *preasons, X509_CRL *crl, X509 *x)
  {
  
      int crl_score = 0;
      unsigned int tmp_reasons = *preasons, crl_reasons;
  
      /* First see if we can reject CRL straight away */
  
      /* Invalid IDP cannot be processed */
      if (crl->idp_flags & IDP_INVALID)
          return 0;
      /* Reason codes or indirect CRLs need extended CRL support */
      if (!(ctx->param->flags & X509_V_FLAG_EXTENDED_CRL_SUPPORT)) {
          if (crl->idp_flags & (IDP_INDIRECT | IDP_REASONS))
              return 0;
      } else if (crl->idp_flags & IDP_REASONS) {
          /* If no new reasons reject */
          if (!(crl->idp_reasons & ~tmp_reasons))
              return 0;
      }
      /* Don't process deltas at this stage */
      else if (crl->base_crl_number)
          return 0;
      /* If issuer name doesn't match certificate need indirect CRL */
      if (X509_NAME_cmp(X509_get_issuer_name(x), X509_CRL_get_issuer(crl))) {
          if (!(crl->idp_flags & IDP_INDIRECT))
              return 0;
      } else
          crl_score |= CRL_SCORE_ISSUER_NAME;
  
      if (!(crl->flags & EXFLAG_CRITICAL))
          crl_score |= CRL_SCORE_NOCRITICAL;
  
      /* Check expiry */
      if (check_crl_time(ctx, crl, 0))
          crl_score |= CRL_SCORE_TIME;
  
      /* Check authority key ID and locate certificate issuer */
      crl_akid_check(ctx, crl, pissuer, &crl_score);
  
      /* If we can't locate certificate issuer at this point forget it */
  
      if (!(crl_score & CRL_SCORE_AKID))
          return 0;
  
      /* Check cert for matching CRL distribution points */
  
      if (crl_crldp_check(x, crl, crl_score, &crl_reasons)) {
          /* If no new reasons reject */
          if (!(crl_reasons & ~tmp_reasons))
              return 0;
          tmp_reasons |= crl_reasons;
          crl_score |= CRL_SCORE_SCOPE;
      }
  
      *preasons = tmp_reasons;
  
      return crl_score;
  
  }
  
  static void crl_akid_check(X509_STORE_CTX *ctx, X509_CRL *crl,
                             X509 **pissuer, int *pcrl_score)
  {
      X509 *crl_issuer = NULL;
      X509_NAME *cnm = X509_CRL_get_issuer(crl);
      int cidx = ctx->error_depth;
      int i;
  
      if (cidx != sk_X509_num(ctx->chain) - 1)
          cidx++;
  
      crl_issuer = sk_X509_value(ctx->chain, cidx);
  
      if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
          if (*pcrl_score & CRL_SCORE_ISSUER_NAME) {
              *pcrl_score |= CRL_SCORE_AKID | CRL_SCORE_ISSUER_CERT;
              *pissuer = crl_issuer;
              return;
          }
      }
  
      for (cidx++; cidx < sk_X509_num(ctx->chain); cidx++) {
          crl_issuer = sk_X509_value(ctx->chain, cidx);
          if (X509_NAME_cmp(X509_get_subject_name(crl_issuer), cnm))
              continue;
          if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
              *pcrl_score |= CRL_SCORE_AKID | CRL_SCORE_SAME_PATH;
              *pissuer = crl_issuer;
              return;
          }
      }
  
      /* Anything else needs extended CRL support */
  
      if (!(ctx->param->flags & X509_V_FLAG_EXTENDED_CRL_SUPPORT))
          return;
  
      /*
       * Otherwise the CRL issuer is not on the path. Look for it in the set of
       * untrusted certificates.
       */
      for (i = 0; i < sk_X509_num(ctx->untrusted); i++) {
          crl_issuer = sk_X509_value(ctx->untrusted, i);
          if (X509_NAME_cmp(X509_get_subject_name(crl_issuer), cnm))
              continue;
          if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
              *pissuer = crl_issuer;
              *pcrl_score |= CRL_SCORE_AKID;
              return;
          }
      }
  }
  
  /*
   * Check the path of a CRL issuer certificate. This creates a new
   * X509_STORE_CTX and populates it with most of the parameters from the
   * parent. This could be optimised somewhat since a lot of path checking will
   * be duplicated by the parent, but this will rarely be used in practice.
   */
  
  static int check_crl_path(X509_STORE_CTX *ctx, X509 *x)
  {
      X509_STORE_CTX crl_ctx;
      int ret;
  
      /* Don't allow recursive CRL path validation */
      if (ctx->parent)
          return 0;
      if (!X509_STORE_CTX_init(&crl_ctx, ctx->ctx, x, ctx->untrusted))
          return -1;
  
      crl_ctx.crls = ctx->crls;
      /* Copy verify params across */
      X509_STORE_CTX_set0_param(&crl_ctx, ctx->param);
  
      crl_ctx.parent = ctx;
      crl_ctx.verify_cb = ctx->verify_cb;
  
      /* Verify CRL issuer */
      ret = X509_verify_cert(&crl_ctx);
      if (ret <= 0)
          goto err;
  
      /* Check chain is acceptable */
      ret = check_crl_chain(ctx, ctx->chain, crl_ctx.chain);
   err:
      X509_STORE_CTX_cleanup(&crl_ctx);
      return ret;
  }
  
  /*
   * RFC3280 says nothing about the relationship between CRL path and
   * certificate path, which could lead to situations where a certificate could
   * be revoked or validated by a CA not authorised to do so. RFC5280 is more
   * strict and states that the two paths must end in the same trust anchor,
   * though some discussions remain... until this is resolved we use the
   * RFC5280 version
   */
  
  static int check_crl_chain(X509_STORE_CTX *ctx,
                             STACK_OF(X509) *cert_path,
                             STACK_OF(X509) *crl_path)
  {
      X509 *cert_ta, *crl_ta;
      cert_ta = sk_X509_value(cert_path, sk_X509_num(cert_path) - 1);
      crl_ta = sk_X509_value(crl_path, sk_X509_num(crl_path) - 1);
      if (!X509_cmp(cert_ta, crl_ta))
          return 1;
      return 0;
  }
  
  /*-
   * Check for match between two dist point names: three separate cases.
   * 1. Both are relative names and compare X509_NAME types.
   * 2. One full, one relative. Compare X509_NAME to GENERAL_NAMES.
   * 3. Both are full names and compare two GENERAL_NAMES.
   * 4. One is NULL: automatic match.
   */
  
  static int idp_check_dp(DIST_POINT_NAME *a, DIST_POINT_NAME *b)
  {
      X509_NAME *nm = NULL;
      GENERAL_NAMES *gens = NULL;
      GENERAL_NAME *gena, *genb;
      int i, j;
      if (!a || !b)
          return 1;
      if (a->type == 1) {
          if (!a->dpname)
              return 0;
          /* Case 1: two X509_NAME */
          if (b->type == 1) {
              if (!b->dpname)
                  return 0;
              if (!X509_NAME_cmp(a->dpname, b->dpname))
                  return 1;
              else
                  return 0;
          }
          /* Case 2: set name and GENERAL_NAMES appropriately */
          nm = a->dpname;
          gens = b->name.fullname;
      } else if (b->type == 1) {
          if (!b->dpname)
              return 0;
          /* Case 2: set name and GENERAL_NAMES appropriately */
          gens = a->name.fullname;
          nm = b->dpname;
      }
  
      /* Handle case 2 with one GENERAL_NAMES and one X509_NAME */
      if (nm) {
          for (i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
              gena = sk_GENERAL_NAME_value(gens, i);
              if (gena->type != GEN_DIRNAME)
                  continue;
              if (!X509_NAME_cmp(nm, gena->d.directoryName))
                  return 1;
          }
          return 0;
      }
  
      /* Else case 3: two GENERAL_NAMES */
  
      for (i = 0; i < sk_GENERAL_NAME_num(a->name.fullname); i++) {
          gena = sk_GENERAL_NAME_value(a->name.fullname, i);
          for (j = 0; j < sk_GENERAL_NAME_num(b->name.fullname); j++) {
              genb = sk_GENERAL_NAME_value(b->name.fullname, j);
              if (!GENERAL_NAME_cmp(gena, genb))
                  return 1;
          }
      }
  
      return 0;
  
  }
  
  static int crldp_check_crlissuer(DIST_POINT *dp, X509_CRL *crl, int crl_score)
  {
      int i;
      X509_NAME *nm = X509_CRL_get_issuer(crl);
      /* If no CRLissuer return is successful iff don't need a match */
      if (!dp->CRLissuer)
          return ! !(crl_score & CRL_SCORE_ISSUER_NAME);
      for (i = 0; i < sk_GENERAL_NAME_num(dp->CRLissuer); i++) {
          GENERAL_NAME *gen = sk_GENERAL_NAME_value(dp->CRLissuer, i);
          if (gen->type != GEN_DIRNAME)
              continue;
          if (!X509_NAME_cmp(gen->d.directoryName, nm))
              return 1;
      }
      return 0;
  }
  
  /* Check CRLDP and IDP */
  
  static int crl_crldp_check(X509 *x, X509_CRL *crl, int crl_score,
                             unsigned int *preasons)
  {
      int i;
      if (crl->idp_flags & IDP_ONLYATTR)
          return 0;
      if (x->ex_flags & EXFLAG_CA) {
          if (crl->idp_flags & IDP_ONLYUSER)
              return 0;
      } else {
          if (crl->idp_flags & IDP_ONLYCA)
              return 0;
      }
      *preasons = crl->idp_reasons;
      for (i = 0; i < sk_DIST_POINT_num(x->crldp); i++) {
          DIST_POINT *dp = sk_DIST_POINT_value(x->crldp, i);
          if (crldp_check_crlissuer(dp, crl, crl_score)) {
              if (!crl->idp || idp_check_dp(dp->distpoint, crl->idp->distpoint)) {
                  *preasons &= dp->dp_reasons;
                  return 1;
              }
          }
      }
      if ((!crl->idp || !crl->idp->distpoint)
          && (crl_score & CRL_SCORE_ISSUER_NAME))
          return 1;
      return 0;
  }
  
  /*
   * Retrieve CRL corresponding to current certificate. If deltas enabled try
   * to find a delta CRL too
   */
  
  static int get_crl_delta(X509_STORE_CTX *ctx,
                           X509_CRL **pcrl, X509_CRL **pdcrl, X509 *x)
  {
      int ok;
      X509 *issuer = NULL;
      int crl_score = 0;
      unsigned int reasons;
      X509_CRL *crl = NULL, *dcrl = NULL;
      STACK_OF(X509_CRL) *skcrl;
      X509_NAME *nm = X509_get_issuer_name(x);
  
      reasons = ctx->current_reasons;
      ok = get_crl_sk(ctx, &crl, &dcrl,
                      &issuer, &crl_score, &reasons, ctx->crls);
      if (ok)
          goto done;
  
      /* Lookup CRLs from store */
  
      skcrl = ctx->lookup_crls(ctx, nm);
  
      /* If no CRLs found and a near match from get_crl_sk use that */
      if (!skcrl && crl)
          goto done;
  
      get_crl_sk(ctx, &crl, &dcrl, &issuer, &crl_score, &reasons, skcrl);
  
      sk_X509_CRL_pop_free(skcrl, X509_CRL_free);
  
   done:
      /* If we got any kind of CRL use it and return success */
      if (crl) {
          ctx->current_issuer = issuer;
          ctx->current_crl_score = crl_score;
          ctx->current_reasons = reasons;
          *pcrl = crl;
          *pdcrl = dcrl;
          return 1;
      }
      return 0;
  }
  
  /* Check CRL validity */
  static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
  {
      X509 *issuer = NULL;
      EVP_PKEY *ikey = NULL;
      int cnum = ctx->error_depth;
      int chnum = sk_X509_num(ctx->chain) - 1;
  
      /* if we have an alternative CRL issuer cert use that */
      if (ctx->current_issuer)
          issuer = ctx->current_issuer;
      /*
       * Else find CRL issuer: if not last certificate then issuer is next
       * certificate in chain.
       */
      else if (cnum < chnum)
          issuer = sk_X509_value(ctx->chain, cnum + 1);
      else {
          issuer = sk_X509_value(ctx->chain, chnum);
          /* If not self signed, can't check signature */
          if (!ctx->check_issued(ctx, issuer, issuer) &&
              !verify_cb_crl(ctx, X509_V_ERR_UNABLE_TO_GET_CRL_ISSUER))
              return 0;
      }
  
      if (issuer == NULL)
          return 1;
  
      /*
       * Skip most tests for deltas because they have already been done
       */
      if (!crl->base_crl_number) {
          /* Check for cRLSign bit if keyUsage present */
          if ((issuer->ex_flags & EXFLAG_KUSAGE) &&
              !(issuer->ex_kusage & KU_CRL_SIGN) &&
              !verify_cb_crl(ctx, X509_V_ERR_KEYUSAGE_NO_CRL_SIGN))
              return 0;
  
          if (!(ctx->current_crl_score & CRL_SCORE_SCOPE) &&
              !verify_cb_crl(ctx, X509_V_ERR_DIFFERENT_CRL_SCOPE))
              return 0;
  
          if (!(ctx->current_crl_score & CRL_SCORE_SAME_PATH) &&
              check_crl_path(ctx, ctx->current_issuer) <= 0 &&
              !verify_cb_crl(ctx, X509_V_ERR_CRL_PATH_VALIDATION_ERROR))
              return 0;
  
          if ((crl->idp_flags & IDP_INVALID) &&
              !verify_cb_crl(ctx, X509_V_ERR_INVALID_EXTENSION))
              return 0;
      }
  
      if (!(ctx->current_crl_score & CRL_SCORE_TIME) &&
          !check_crl_time(ctx, crl, 1))
          return 0;
  
      /* Attempt to get issuer certificate public key */
      ikey = X509_get0_pubkey(issuer);
  
      if (!ikey &&
          !verify_cb_crl(ctx, X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY))
          return 0;
  
      if (ikey) {
          int rv = X509_CRL_check_suiteb(crl, ikey, ctx->param->flags);
  
          if (rv != X509_V_OK && !verify_cb_crl(ctx, rv))
              return 0;
          /* Verify CRL signature */
          if (X509_CRL_verify(crl, ikey) <= 0 &&
              !verify_cb_crl(ctx, X509_V_ERR_CRL_SIGNATURE_FAILURE))
              return 0;
      }
      return 1;
  }
  
  /* Check certificate against CRL */
  static int cert_crl(X509_STORE_CTX *ctx, X509_CRL *crl, X509 *x)
  {
      X509_REVOKED *rev;
  
      /*
       * The rules changed for this... previously if a CRL contained unhandled
       * critical extensions it could still be used to indicate a certificate
       * was revoked. This has since been changed since critical extensions can
       * change the meaning of CRL entries.
       */
      if (!(ctx->param->flags & X509_V_FLAG_IGNORE_CRITICAL)
          && (crl->flags & EXFLAG_CRITICAL) &&
          !verify_cb_crl(ctx, X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION))
          return 0;
      /*
       * Look for serial number of certificate in CRL.  If found, make sure
       * reason is not removeFromCRL.
       */
      if (X509_CRL_get0_by_cert(crl, &rev, x)) {
          if (rev->reason == CRL_REASON_REMOVE_FROM_CRL)
              return 2;
          if (!verify_cb_crl(ctx, X509_V_ERR_CERT_REVOKED))
              return 0;
      }
  
      return 1;
  }
  
  static int check_policy(X509_STORE_CTX *ctx)
  {
      int ret;
  
      if (ctx->parent)
          return 1;
      /*
       * With DANE, the trust anchor might be a bare public key, not a
       * certificate!  In that case our chain does not have the trust anchor
       * certificate as a top-most element.  This comports well with RFC5280
       * chain verification, since there too, the trust anchor is not part of the
       * chain to be verified.  In particular, X509_policy_check() does not look
       * at the TA cert, but assumes that it is present as the top-most chain
       * element.  We therefore temporarily push a NULL cert onto the chain if it
       * was verified via a bare public key, and pop it off right after the
       * X509_policy_check() call.
       */
      if (ctx->bare_ta_signed && !sk_X509_push(ctx->chain, NULL)) {
          X509err(X509_F_CHECK_POLICY, ERR_R_MALLOC_FAILURE);
          ctx->error = X509_V_ERR_OUT_OF_MEM;
          return 0;
      }
      ret = X509_policy_check(&ctx->tree, &ctx->explicit_policy, ctx->chain,
                              ctx->param->policies, ctx->param->flags);
      if (ctx->bare_ta_signed)
          sk_X509_pop(ctx->chain);
  
      if (ret == X509_PCY_TREE_INTERNAL) {
          X509err(X509_F_CHECK_POLICY, ERR_R_MALLOC_FAILURE);
          ctx->error = X509_V_ERR_OUT_OF_MEM;
          return 0;
      }
      /* Invalid or inconsistent extensions */
      if (ret == X509_PCY_TREE_INVALID) {
          int i;
  
          /* Locate certificates with bad extensions and notify callback. */
          for (i = 1; i < sk_X509_num(ctx->chain); i++) {
              X509 *x = sk_X509_value(ctx->chain, i);
  
              if (!(x->ex_flags & EXFLAG_INVALID_POLICY))
                  continue;
              if (!verify_cb_cert(ctx, x, i,
                                  X509_V_ERR_INVALID_POLICY_EXTENSION))
                  return 0;
          }
          return 1;
      }
      if (ret == X509_PCY_TREE_FAILURE) {
          ctx->current_cert = NULL;
          ctx->error = X509_V_ERR_NO_EXPLICIT_POLICY;
          return ctx->verify_cb(0, ctx);
      }
      if (ret != X509_PCY_TREE_VALID) {
          X509err(X509_F_CHECK_POLICY, ERR_R_INTERNAL_ERROR);
          return 0;
      }
  
      if (ctx->param->flags & X509_V_FLAG_NOTIFY_POLICY) {
          ctx->current_cert = NULL;
          /*
           * Verification errors need to be "sticky", a callback may have allowed
           * an SSL handshake to continue despite an error, and we must then
           * remain in an error state.  Therefore, we MUST NOT clear earlier
           * verification errors by setting the error to X509_V_OK.
           */
          if (!ctx->verify_cb(2, ctx))
              return 0;
      }
  
      return 1;
  }
  
  /*-
   * Check certificate validity times.
   * If depth >= 0, invoke verification callbacks on error, otherwise just return
   * the validation status.
   *
   * Return 1 on success, 0 otherwise.
   */
  int x509_check_cert_time(X509_STORE_CTX *ctx, X509 *x, int depth)
  {
      time_t *ptime;
      int i;
  
      if (ctx->param->flags & X509_V_FLAG_USE_CHECK_TIME)
          ptime = &ctx->param->check_time;
      else if (ctx->param->flags & X509_V_FLAG_NO_CHECK_TIME)
          return 1;
      else
          ptime = NULL;
  
      i = X509_cmp_time(X509_get0_notBefore(x), ptime);
      if (i >= 0 && depth < 0)
          return 0;
      if (i == 0 && !verify_cb_cert(ctx, x, depth,
                                    X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD))
          return 0;
      if (i > 0 && !verify_cb_cert(ctx, x, depth, X509_V_ERR_CERT_NOT_YET_VALID))
          return 0;
  
      i = X509_cmp_time(X509_get0_notAfter(x), ptime);
      if (i <= 0 && depth < 0)
          return 0;
      if (i == 0 && !verify_cb_cert(ctx, x, depth,
                                    X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD))
          return 0;
      if (i < 0 && !verify_cb_cert(ctx, x, depth, X509_V_ERR_CERT_HAS_EXPIRED))
          return 0;
      return 1;
  }
  
  static int internal_verify(X509_STORE_CTX *ctx)
  {
      int n = sk_X509_num(ctx->chain) - 1;
      X509 *xi = sk_X509_value(ctx->chain, n);
      X509 *xs;
  
      /*
       * With DANE-verified bare public key TA signatures, it remains only to
       * check the timestamps of the top certificate.  We report the issuer as
       * NULL, since all we have is a bare key.
       */
      if (ctx->bare_ta_signed) {
          xs = xi;
          xi = NULL;
          goto check_cert;
      }
  
      if (ctx->check_issued(ctx, xi, xi))
          xs = xi;
      else {
          if (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN) {
              xs = xi;
              goto check_cert;
          }
          if (n <= 0)
              return verify_cb_cert(ctx, xi, 0,
                                    X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE);
          n--;
          ctx->error_depth = n;
          xs = sk_X509_value(ctx->chain, n);
      }
  
      /*
       * Do not clear ctx->error=0, it must be "sticky", only the user's callback
       * is allowed to reset errors (at its own peril).
       */
      while (n >= 0) {
          EVP_PKEY *pkey;
  
          /*
           * Skip signature check for self signed certificates unless explicitly
           * asked for.  It doesn't add any security and just wastes time.  If
           * the issuer's public key is unusable, report the issuer certificate
           * and its depth (rather than the depth of the subject).
           */
          if (xs != xi || (ctx->param->flags & X509_V_FLAG_CHECK_SS_SIGNATURE)) {
              if ((pkey = X509_get0_pubkey(xi)) == NULL) {
                  if (!verify_cb_cert(ctx, xi, xi != xs ? n+1 : n,
                          X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY))
                      return 0;
              } else if (X509_verify(xs, pkey) <= 0) {
                  if (!verify_cb_cert(ctx, xs, n,
                                      X509_V_ERR_CERT_SIGNATURE_FAILURE))
                      return 0;
              }
          }
  
   check_cert:
          /* Calls verify callback as needed */
          if (!x509_check_cert_time(ctx, xs, n))
              return 0;
  
          /*
           * Signal success at this depth.  However, the previous error (if any)
           * is retained.
           */
          ctx->current_issuer = xi;
          ctx->current_cert = xs;
          ctx->error_depth = n;
          if (!ctx->verify_cb(1, ctx))
              return 0;
  
          if (--n >= 0) {
              xi = xs;
              xs = sk_X509_value(ctx->chain, n);
          }
      }
      return 1;
  }
  
  int X509_cmp_current_time(const ASN1_TIME *ctm)
  {
      return X509_cmp_time(ctm, NULL);
  }
  
  int X509_cmp_time(const ASN1_TIME *ctm, time_t *cmp_time)
  {
      static const size_t utctime_length = sizeof("YYMMDDHHMMSSZ") - 1;
      static const size_t generalizedtime_length = sizeof("YYYYMMDDHHMMSSZ") - 1;
      ASN1_TIME *asn1_cmp_time = NULL;
      int i, day, sec, ret = 0;
  
      /*
       * Note that ASN.1 allows much more slack in the time format than RFC5280.
       * In RFC5280, the representation is fixed:
       * UTCTime: YYMMDDHHMMSSZ
       * GeneralizedTime: YYYYMMDDHHMMSSZ
       *
       * We do NOT currently enforce the following RFC 5280 requirement:
       * "CAs conforming to this profile MUST always encode certificate
       *  validity dates through the year 2049 as UTCTime; certificate validity
       *  dates in 2050 or later MUST be encoded as GeneralizedTime."
       */
      switch (ctm->type) {
      case V_ASN1_UTCTIME:
          if (ctm->length != (int)(utctime_length))
              return 0;
          break;
      case V_ASN1_GENERALIZEDTIME:
          if (ctm->length != (int)(generalizedtime_length))
              return 0;
          break;
      default:
          return 0;
      }
  
      /**
       * Verify the format: the ASN.1 functions we use below allow a more
       * flexible format than what's mandated by RFC 5280.
       * Digit and date ranges will be verified in the conversion methods.
       */
      for (i = 0; i < ctm->length - 1; i++) {
          if (!ossl_isdigit(ctm->data[i]))
              return 0;
      }
      if (ctm->data[ctm->length - 1] != 'Z')
          return 0;
  
      /*
       * There is ASN1_UTCTIME_cmp_time_t but no
       * ASN1_GENERALIZEDTIME_cmp_time_t or ASN1_TIME_cmp_time_t,
       * so we go through ASN.1
       */
      asn1_cmp_time = X509_time_adj(NULL, 0, cmp_time);
      if (asn1_cmp_time == NULL)
          goto err;
      if (!ASN1_TIME_diff(&day, &sec, ctm, asn1_cmp_time))
          goto err;
  
      /*
       * X509_cmp_time comparison is <=.
       * The return value 0 is reserved for errors.
       */
      ret = (day >= 0 && sec >= 0) ? -1 : 1;
  
   err:
      ASN1_TIME_free(asn1_cmp_time);
      return ret;
  }
  
  ASN1_TIME *X509_gmtime_adj(ASN1_TIME *s, long adj)
  {
      return X509_time_adj(s, adj, NULL);
  }
  
  ASN1_TIME *X509_time_adj(ASN1_TIME *s, long offset_sec, time_t *in_tm)
  {
      return X509_time_adj_ex(s, 0, offset_sec, in_tm);
  }
  
  ASN1_TIME *X509_time_adj_ex(ASN1_TIME *s,
                              int offset_day, long offset_sec, time_t *in_tm)
  {
      time_t t;
  
      if (in_tm)
          t = *in_tm;
      else
          time(&t);
  
      if (s && !(s->flags & ASN1_STRING_FLAG_MSTRING)) {
          if (s->type == V_ASN1_UTCTIME)
              return ASN1_UTCTIME_adj(s, t, offset_day, offset_sec);
          if (s->type == V_ASN1_GENERALIZEDTIME)
              return ASN1_GENERALIZEDTIME_adj(s, t, offset_day, offset_sec);
      }
      return ASN1_TIME_adj(s, t, offset_day, offset_sec);
  }
  
  int X509_get_pubkey_parameters(EVP_PKEY *pkey, STACK_OF(X509) *chain)
  {
      EVP_PKEY *ktmp = NULL, *ktmp2;
      int i, j;
  
      if ((pkey != NULL) && !EVP_PKEY_missing_parameters(pkey))
          return 1;
  
      for (i = 0; i < sk_X509_num(chain); i++) {
          ktmp = X509_get0_pubkey(sk_X509_value(chain, i));
          if (ktmp == NULL) {
              X509err(X509_F_X509_GET_PUBKEY_PARAMETERS,
                      X509_R_UNABLE_TO_GET_CERTS_PUBLIC_KEY);
              return 0;
          }
          if (!EVP_PKEY_missing_parameters(ktmp))
              break;
      }
      if (ktmp == NULL) {
          X509err(X509_F_X509_GET_PUBKEY_PARAMETERS,
                  X509_R_UNABLE_TO_FIND_PARAMETERS_IN_CHAIN);
          return 0;
      }
  
      /* first, populate the other certs */
      for (j = i - 1; j >= 0; j--) {
          ktmp2 = X509_get0_pubkey(sk_X509_value(chain, j));
          EVP_PKEY_copy_parameters(ktmp2, ktmp);
      }
  
      if (pkey != NULL)
          EVP_PKEY_copy_parameters(pkey, ktmp);
      return 1;
  }
  
  /* Make a delta CRL as the diff between two full CRLs */
  
  X509_CRL *X509_CRL_diff(X509_CRL *base, X509_CRL *newer,
                          EVP_PKEY *skey, const EVP_MD *md, unsigned int flags)
  {
      X509_CRL *crl = NULL;
      int i;
      STACK_OF(X509_REVOKED) *revs = NULL;
      /* CRLs can't be delta already */
      if (base->base_crl_number || newer->base_crl_number) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_CRL_ALREADY_DELTA);
          return NULL;
      }
      /* Base and new CRL must have a CRL number */
      if (!base->crl_number || !newer->crl_number) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_NO_CRL_NUMBER);
          return NULL;
      }
      /* Issuer names must match */
      if (X509_NAME_cmp(X509_CRL_get_issuer(base), X509_CRL_get_issuer(newer))) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_ISSUER_MISMATCH);
          return NULL;
      }
      /* AKID and IDP must match */
      if (!crl_extension_match(base, newer, NID_authority_key_identifier)) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_AKID_MISMATCH);
          return NULL;
      }
      if (!crl_extension_match(base, newer, NID_issuing_distribution_point)) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_IDP_MISMATCH);
          return NULL;
      }
      /* Newer CRL number must exceed full CRL number */
      if (ASN1_INTEGER_cmp(newer->crl_number, base->crl_number) <= 0) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_NEWER_CRL_NOT_NEWER);
          return NULL;
      }
      /* CRLs must verify */
      if (skey && (X509_CRL_verify(base, skey) <= 0 ||
                   X509_CRL_verify(newer, skey) <= 0)) {
          X509err(X509_F_X509_CRL_DIFF, X509_R_CRL_VERIFY_FAILURE);
          return NULL;
      }
      /* Create new CRL */
      crl = X509_CRL_new();
      if (crl == NULL || !X509_CRL_set_version(crl, 1))
          goto memerr;
      /* Set issuer name */
      if (!X509_CRL_set_issuer_name(crl, X509_CRL_get_issuer(newer)))
          goto memerr;
  
      if (!X509_CRL_set1_lastUpdate(crl, X509_CRL_get0_lastUpdate(newer)))
          goto memerr;
      if (!X509_CRL_set1_nextUpdate(crl, X509_CRL_get0_nextUpdate(newer)))
          goto memerr;
  
      /* Set base CRL number: must be critical */
  
      if (!X509_CRL_add1_ext_i2d(crl, NID_delta_crl, base->crl_number, 1, 0))
          goto memerr;
  
      /*
       * Copy extensions across from newest CRL to delta: this will set CRL
       * number to correct value too.
       */
  
      for (i = 0; i < X509_CRL_get_ext_count(newer); i++) {
          X509_EXTENSION *ext;
          ext = X509_CRL_get_ext(newer, i);
          if (!X509_CRL_add_ext(crl, ext, -1))
              goto memerr;
      }
  
      /* Go through revoked entries, copying as needed */
  
      revs = X509_CRL_get_REVOKED(newer);
  
      for (i = 0; i < sk_X509_REVOKED_num(revs); i++) {
          X509_REVOKED *rvn, *rvtmp;
          rvn = sk_X509_REVOKED_value(revs, i);
          /*
           * Add only if not also in base. TODO: need something cleverer here
           * for some more complex CRLs covering multiple CAs.
           */
          if (!X509_CRL_get0_by_serial(base, &rvtmp, &rvn->serialNumber)) {
              rvtmp = X509_REVOKED_dup(rvn);
              if (!rvtmp)
                  goto memerr;
              if (!X509_CRL_add0_revoked(crl, rvtmp)) {
                  X509_REVOKED_free(rvtmp);
                  goto memerr;
              }
          }
      }
      /* TODO: optionally prune deleted entries */
  
      if (skey && md && !X509_CRL_sign(crl, skey, md))
          goto memerr;
  
      return crl;
  
   memerr:
      X509err(X509_F_X509_CRL_DIFF, ERR_R_MALLOC_FAILURE);
      X509_CRL_free(crl);
      return NULL;
  }
  
  int X509_STORE_CTX_set_ex_data(X509_STORE_CTX *ctx, int idx, void *data)
  {
      return CRYPTO_set_ex_data(&ctx->ex_data, idx, data);
  }
  
  void *X509_STORE_CTX_get_ex_data(X509_STORE_CTX *ctx, int idx)
  {
      return CRYPTO_get_ex_data(&ctx->ex_data, idx);
  }
  
  int X509_STORE_CTX_get_error(X509_STORE_CTX *ctx)
  {
      return ctx->error;
  }
  
  void X509_STORE_CTX_set_error(X509_STORE_CTX *ctx, int err)
  {
      ctx->error = err;
  }
  
  int X509_STORE_CTX_get_error_depth(X509_STORE_CTX *ctx)
  {
      return ctx->error_depth;
  }
  
  void X509_STORE_CTX_set_error_depth(X509_STORE_CTX *ctx, int depth)
  {
      ctx->error_depth = depth;
  }
  
  X509 *X509_STORE_CTX_get_current_cert(X509_STORE_CTX *ctx)
  {
      return ctx->current_cert;
  }
  
  void X509_STORE_CTX_set_current_cert(X509_STORE_CTX *ctx, X509 *x)
  {
      ctx->current_cert = x;
  }
  
  STACK_OF(X509) *X509_STORE_CTX_get0_chain(X509_STORE_CTX *ctx)
  {
      return ctx->chain;
  }
  
  STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx)
  {
      if (!ctx->chain)
          return NULL;
      return X509_chain_up_ref(ctx->chain);
  }
  
  X509 *X509_STORE_CTX_get0_current_issuer(X509_STORE_CTX *ctx)
  {
      return ctx->current_issuer;
  }
  
  X509_CRL *X509_STORE_CTX_get0_current_crl(X509_STORE_CTX *ctx)
  {
      return ctx->current_crl;
  }
  
  X509_STORE_CTX *X509_STORE_CTX_get0_parent_ctx(X509_STORE_CTX *ctx)
  {
      return ctx->parent;
  }
  
  void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx, X509 *x)
  {
      ctx->cert = x;
  }
  
  void X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk)
  {
      ctx->crls = sk;
  }
  
  int X509_STORE_CTX_set_purpose(X509_STORE_CTX *ctx, int purpose)
  {
      /*
       * XXX: Why isn't this function always used to set the associated trust?
       * Should there even be a VPM->trust field at all?  Or should the trust
       * always be inferred from the purpose by X509_STORE_CTX_init().
       */
      return X509_STORE_CTX_purpose_inherit(ctx, 0, purpose, 0);
  }
  
  int X509_STORE_CTX_set_trust(X509_STORE_CTX *ctx, int trust)
  {
      /*
       * XXX: See above, this function would only be needed when the default
       * trust for the purpose needs an override in a corner case.
       */
      return X509_STORE_CTX_purpose_inherit(ctx, 0, 0, trust);
  }
  
  /*
   * This function is used to set the X509_STORE_CTX purpose and trust values.
   * This is intended to be used when another structure has its own trust and
   * purpose values which (if set) will be inherited by the ctx. If they aren't
   * set then we will usually have a default purpose in mind which should then
   * be used to set the trust value. An example of this is SSL use: an SSL
   * structure will have its own purpose and trust settings which the
   * application can set: if they aren't set then we use the default of SSL
   * client/server.
   */
  
  int X509_STORE_CTX_purpose_inherit(X509_STORE_CTX *ctx, int def_purpose,
                                     int purpose, int trust)
  {
      int idx;
      /* If purpose not set use default */
      if (!purpose)
          purpose = def_purpose;
      /* If we have a purpose then check it is valid */
      if (purpose) {
          X509_PURPOSE *ptmp;
          idx = X509_PURPOSE_get_by_id(purpose);
          if (idx == -1) {
              X509err(X509_F_X509_STORE_CTX_PURPOSE_INHERIT,
                      X509_R_UNKNOWN_PURPOSE_ID);
              return 0;
          }
          ptmp = X509_PURPOSE_get0(idx);
          if (ptmp->trust == X509_TRUST_DEFAULT) {
              idx = X509_PURPOSE_get_by_id(def_purpose);
              /*
               * XXX: In the two callers above def_purpose is always 0, which is
               * not a known value, so idx will always be -1.  How is the
               * X509_TRUST_DEFAULT case actually supposed to be handled?
               */
              if (idx == -1) {
                  X509err(X509_F_X509_STORE_CTX_PURPOSE_INHERIT,
                          X509_R_UNKNOWN_PURPOSE_ID);
                  return 0;
              }
              ptmp = X509_PURPOSE_get0(idx);
          }
          /* If trust not set then get from purpose default */
          if (!trust)
              trust = ptmp->trust;
      }
      if (trust) {
          idx = X509_TRUST_get_by_id(trust);
          if (idx == -1) {
              X509err(X509_F_X509_STORE_CTX_PURPOSE_INHERIT,
                      X509_R_UNKNOWN_TRUST_ID);
              return 0;
          }
      }
  
      if (purpose && !ctx->param->purpose)
          ctx->param->purpose = purpose;
      if (trust && !ctx->param->trust)
          ctx->param->trust = trust;
      return 1;
  }
  
  X509_STORE_CTX *X509_STORE_CTX_new(void)
  {
      X509_STORE_CTX *ctx = OPENSSL_zalloc(sizeof(*ctx));
  
      if (ctx == NULL) {
          X509err(X509_F_X509_STORE_CTX_NEW, ERR_R_MALLOC_FAILURE);
          return NULL;
      }
      return ctx;
  }
  
  void X509_STORE_CTX_free(X509_STORE_CTX *ctx)
  {
      if (ctx == NULL)
          return;
  
      X509_STORE_CTX_cleanup(ctx);
      OPENSSL_free(ctx);
  }
  
  int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store, X509 *x509,
                          STACK_OF(X509) *chain)
  {
      int ret = 1;
  
      ctx->ctx = store;
      ctx->cert = x509;
      ctx->untrusted = chain;
      ctx->crls = NULL;
      ctx->num_untrusted = 0;
      ctx->other_ctx = NULL;
      ctx->valid = 0;
      ctx->chain = NULL;
      ctx->error = 0;
      ctx->explicit_policy = 0;
      ctx->error_depth = 0;
      ctx->current_cert = NULL;
      ctx->current_issuer = NULL;
      ctx->current_crl = NULL;
      ctx->current_crl_score = 0;
      ctx->current_reasons = 0;
      ctx->tree = NULL;
      ctx->parent = NULL;
      ctx->dane = NULL;
      ctx->bare_ta_signed = 0;
      /* Zero ex_data to make sure we're cleanup-safe */
      memset(&ctx->ex_data, 0, sizeof(ctx->ex_data));
  
      /* store->cleanup is always 0 in OpenSSL, if set must be idempotent */
      if (store)
          ctx->cleanup = store->cleanup;
      else
          ctx->cleanup = 0;
  
      if (store && store->check_issued)
          ctx->check_issued = store->check_issued;
      else
          ctx->check_issued = check_issued;
  
      if (store && store->get_issuer)
          ctx->get_issuer = store->get_issuer;
      else
          ctx->get_issuer = X509_STORE_CTX_get1_issuer;
  
      if (store && store->verify_cb)
          ctx->verify_cb = store->verify_cb;
      else
          ctx->verify_cb = null_callback;
  
      if (store && store->verify)
          ctx->verify = store->verify;
      else
          ctx->verify = internal_verify;
  
      if (store && store->check_revocation)
          ctx->check_revocation = store->check_revocation;
      else
          ctx->check_revocation = check_revocation;
  
      if (store && store->get_crl)
          ctx->get_crl = store->get_crl;
      else
          ctx->get_crl = NULL;
  
      if (store && store->check_crl)
          ctx->check_crl = store->check_crl;
      else
          ctx->check_crl = check_crl;
  
      if (store && store->cert_crl)
          ctx->cert_crl = store->cert_crl;
      else
          ctx->cert_crl = cert_crl;
  
      if (store && store->check_policy)
          ctx->check_policy = store->check_policy;
      else
          ctx->check_policy = check_policy;
  
      if (store && store->lookup_certs)
          ctx->lookup_certs = store->lookup_certs;
      else
          ctx->lookup_certs = X509_STORE_CTX_get1_certs;
  
      if (store && store->lookup_crls)
          ctx->lookup_crls = store->lookup_crls;
      else
          ctx->lookup_crls = X509_STORE_CTX_get1_crls;
  
      ctx->param = X509_VERIFY_PARAM_new();
      if (ctx->param == NULL) {
          X509err(X509_F_X509_STORE_CTX_INIT, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      /*
       * Inherit callbacks and flags from X509_STORE if not set use defaults.
       */
      if (store)
          ret = X509_VERIFY_PARAM_inherit(ctx->param, store->param);
      else
          ctx->param->inh_flags |= X509_VP_FLAG_DEFAULT | X509_VP_FLAG_ONCE;
  
      if (ret)
          ret = X509_VERIFY_PARAM_inherit(ctx->param,
                                          X509_VERIFY_PARAM_lookup("default"));
  
      if (ret == 0) {
          X509err(X509_F_X509_STORE_CTX_INIT, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      /*
       * XXX: For now, continue to inherit trust from VPM, but infer from the
       * purpose if this still yields the default value.
       */
      if (ctx->param->trust == X509_TRUST_DEFAULT) {
          int idx = X509_PURPOSE_get_by_id(ctx->param->purpose);
          X509_PURPOSE *xp = X509_PURPOSE_get0(idx);
  
          if (xp != NULL)
              ctx->param->trust = X509_PURPOSE_get_trust(xp);
      }
  
      if (CRYPTO_new_ex_data(CRYPTO_EX_INDEX_X509_STORE_CTX, ctx,
                             &ctx->ex_data))
          return 1;
      X509err(X509_F_X509_STORE_CTX_INIT, ERR_R_MALLOC_FAILURE);
  
   err:
      /*
       * On error clean up allocated storage, if the store context was not
       * allocated with X509_STORE_CTX_new() this is our last chance to do so.
       */
      X509_STORE_CTX_cleanup(ctx);
      return 0;
  }
  
  /*
   * Set alternative lookup method: just a STACK of trusted certificates. This
   * avoids X509_STORE nastiness where it isn't needed.
   */
  void X509_STORE_CTX_set0_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk)
  {
      ctx->other_ctx = sk;
      ctx->get_issuer = get_issuer_sk;
      ctx->lookup_certs = lookup_certs_sk;
  }
  
  void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx)
  {
      /*
       * We need to be idempotent because, unfortunately, free() also calls
       * cleanup(), so the natural call sequence new(), init(), cleanup(), free()
       * calls cleanup() for the same object twice!  Thus we must zero the
       * pointers below after they're freed!
       */
      /* Seems to always be 0 in OpenSSL, do this at most once. */
      if (ctx->cleanup != NULL) {
          ctx->cleanup(ctx);
          ctx->cleanup = NULL;
      }
      if (ctx->param != NULL) {
          if (ctx->parent == NULL)
              X509_VERIFY_PARAM_free(ctx->param);
          ctx->param = NULL;
      }
      X509_policy_tree_free(ctx->tree);
      ctx->tree = NULL;
      sk_X509_pop_free(ctx->chain, X509_free);
      ctx->chain = NULL;
      CRYPTO_free_ex_data(CRYPTO_EX_INDEX_X509_STORE_CTX, ctx, &(ctx->ex_data));
      memset(&ctx->ex_data, 0, sizeof(ctx->ex_data));
  }
  
  void X509_STORE_CTX_set_depth(X509_STORE_CTX *ctx, int depth)
  {
      X509_VERIFY_PARAM_set_depth(ctx->param, depth);
  }
  
  void X509_STORE_CTX_set_flags(X509_STORE_CTX *ctx, unsigned long flags)
  {
      X509_VERIFY_PARAM_set_flags(ctx->param, flags);
  }
  
  void X509_STORE_CTX_set_time(X509_STORE_CTX *ctx, unsigned long flags,
                               time_t t)
  {
      X509_VERIFY_PARAM_set_time(ctx->param, t);
  }
  
  X509 *X509_STORE_CTX_get0_cert(X509_STORE_CTX *ctx)
  {
      return ctx->cert;
  }
  
  STACK_OF(X509) *X509_STORE_CTX_get0_untrusted(X509_STORE_CTX *ctx)
  {
      return ctx->untrusted;
  }
  
  void X509_STORE_CTX_set0_untrusted(X509_STORE_CTX *ctx, STACK_OF(X509) *sk)
  {
      ctx->untrusted = sk;
  }
  
  void X509_STORE_CTX_set0_verified_chain(X509_STORE_CTX *ctx, STACK_OF(X509) *sk)
  {
      sk_X509_pop_free(ctx->chain, X509_free);
      ctx->chain = sk;
  }
  
  void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
                                    X509_STORE_CTX_verify_cb verify_cb)
  {
      ctx->verify_cb = verify_cb;
  }
  
  X509_STORE_CTX_verify_cb X509_STORE_CTX_get_verify_cb(X509_STORE_CTX *ctx)
  {
      return ctx->verify_cb;
  }
  
  void X509_STORE_CTX_set_verify(X509_STORE_CTX *ctx,
                                 X509_STORE_CTX_verify_fn verify)
  {
      ctx->verify = verify;
  }
  
  X509_STORE_CTX_verify_fn X509_STORE_CTX_get_verify(X509_STORE_CTX *ctx)
  {
      return ctx->verify;
  }
  
  X509_STORE_CTX_get_issuer_fn X509_STORE_CTX_get_get_issuer(X509_STORE_CTX *ctx)
  {
      return ctx->get_issuer;
  }
  
  X509_STORE_CTX_check_issued_fn X509_STORE_CTX_get_check_issued(X509_STORE_CTX *ctx)
  {
      return ctx->check_issued;
  }
  
  X509_STORE_CTX_check_revocation_fn X509_STORE_CTX_get_check_revocation(X509_STORE_CTX *ctx)
  {
      return ctx->check_revocation;
  }
  
  X509_STORE_CTX_get_crl_fn X509_STORE_CTX_get_get_crl(X509_STORE_CTX *ctx)
  {
      return ctx->get_crl;
  }
  
  X509_STORE_CTX_check_crl_fn X509_STORE_CTX_get_check_crl(X509_STORE_CTX *ctx)
  {
      return ctx->check_crl;
  }
  
  X509_STORE_CTX_cert_crl_fn X509_STORE_CTX_get_cert_crl(X509_STORE_CTX *ctx)
  {
      return ctx->cert_crl;
  }
  
  X509_STORE_CTX_check_policy_fn X509_STORE_CTX_get_check_policy(X509_STORE_CTX *ctx)
  {
      return ctx->check_policy;
  }
  
  X509_STORE_CTX_lookup_certs_fn X509_STORE_CTX_get_lookup_certs(X509_STORE_CTX *ctx)
  {
      return ctx->lookup_certs;
  }
  
  X509_STORE_CTX_lookup_crls_fn X509_STORE_CTX_get_lookup_crls(X509_STORE_CTX *ctx)
  {
      return ctx->lookup_crls;
  }
  
  X509_STORE_CTX_cleanup_fn X509_STORE_CTX_get_cleanup(X509_STORE_CTX *ctx)
  {
      return ctx->cleanup;
  }
  
  X509_POLICY_TREE *X509_STORE_CTX_get0_policy_tree(X509_STORE_CTX *ctx)
  {
      return ctx->tree;
  }
  
  int X509_STORE_CTX_get_explicit_policy(X509_STORE_CTX *ctx)
  {
      return ctx->explicit_policy;
  }
  
  int X509_STORE_CTX_get_num_untrusted(X509_STORE_CTX *ctx)
  {
      return ctx->num_untrusted;
  }
  
  int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name)
  {
      const X509_VERIFY_PARAM *param;
      param = X509_VERIFY_PARAM_lookup(name);
      if (!param)
          return 0;
      return X509_VERIFY_PARAM_inherit(ctx->param, param);
  }
  
  X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(X509_STORE_CTX *ctx)
  {
      return ctx->param;
  }
  
  void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param)
  {
      X509_VERIFY_PARAM_free(ctx->param);
      ctx->param = param;
  }
  
  void X509_STORE_CTX_set0_dane(X509_STORE_CTX *ctx, SSL_DANE *dane)
  {
      ctx->dane = dane;
  }
  
  static unsigned char *dane_i2d(
      X509 *cert,
      uint8_t selector,
      unsigned int *i2dlen)
  {
      unsigned char *buf = NULL;
      int len;
  
      /*
       * Extract ASN.1 DER form of certificate or public key.
       */
      switch (selector) {
      case DANETLS_SELECTOR_CERT:
          len = i2d_X509(cert, &buf);
          break;
      case DANETLS_SELECTOR_SPKI:
          len = i2d_X509_PUBKEY(X509_get_X509_PUBKEY(cert), &buf);
          break;
      default:
          X509err(X509_F_DANE_I2D, X509_R_BAD_SELECTOR);
          return NULL;
      }
  
      if (len < 0 || buf == NULL) {
          X509err(X509_F_DANE_I2D, ERR_R_MALLOC_FAILURE);
          return NULL;
      }
  
      *i2dlen = (unsigned int)len;
      return buf;
  }
  
  #define DANETLS_NONE 256        /* impossible uint8_t */
  
  static int dane_match(X509_STORE_CTX *ctx, X509 *cert, int depth)
  {
      SSL_DANE *dane = ctx->dane;
      unsigned usage = DANETLS_NONE;
      unsigned selector = DANETLS_NONE;
      unsigned ordinal = DANETLS_NONE;
      unsigned mtype = DANETLS_NONE;
      unsigned char *i2dbuf = NULL;
      unsigned int i2dlen = 0;
      unsigned char mdbuf[EVP_MAX_MD_SIZE];
      unsigned char *cmpbuf = NULL;
      unsigned int cmplen = 0;
      int i;
      int recnum;
      int matched = 0;
      danetls_record *t = NULL;
      uint32_t mask;
  
      mask = (depth == 0) ? DANETLS_EE_MASK : DANETLS_TA_MASK;
  
      /*
       * The trust store is not applicable with DANE-TA(2)
       */
      if (depth >= ctx->num_untrusted)
          mask &= DANETLS_PKIX_MASK;
  
      /*
       * If we've previously matched a PKIX-?? record, no need to test any
       * further PKIX-?? records, it remains to just build the PKIX chain.
       * Had the match been a DANE-?? record, we'd be done already.
       */
      if (dane->mdpth >= 0)
          mask &= ~DANETLS_PKIX_MASK;
  
      /*-
       * https://tools.ietf.org/html/rfc7671#section-5.1
       * https://tools.ietf.org/html/rfc7671#section-5.2
       * https://tools.ietf.org/html/rfc7671#section-5.3
       * https://tools.ietf.org/html/rfc7671#section-5.4
       *
       * We handle DANE-EE(3) records first as they require no chain building
       * and no expiration or hostname checks.  We also process digests with
       * higher ordinals first and ignore lower priorities except Full(0) which
       * is always processed (last).  If none match, we then process PKIX-EE(1).
       *
       * NOTE: This relies on DANE usages sorting before the corresponding PKIX
       * usages in SSL_dane_tlsa_add(), and also on descending sorting of digest
       * priorities.  See twin comment in ssl/ssl_lib.c.
       *
       * We expect that most TLSA RRsets will have just a single usage, so we
       * don't go out of our way to cache multiple selector-specific i2d buffers
       * across usages, but if the selector happens to remain the same as switch
       * usages, that's OK.  Thus, a set of "3 1 1", "3 0 1", "1 1 1", "1 0 1",
       * records would result in us generating each of the certificate and public
       * key DER forms twice, but more typically we'd just see multiple "3 1 1"
       * or multiple "3 0 1" records.
       *
       * As soon as we find a match at any given depth, we stop, because either
       * we've matched a DANE-?? record and the peer is authenticated, or, after
       * exhausting all DANE-?? records, we've matched a PKIX-?? record, which is
       * sufficient for DANE, and what remains to do is ordinary PKIX validation.
       */
      recnum = (dane->umask & mask) ? sk_danetls_record_num(dane->trecs) : 0;
      for (i = 0; matched == 0 && i < recnum; ++i) {
          t = sk_danetls_record_value(dane->trecs, i);
          if ((DANETLS_USAGE_BIT(t->usage) & mask) == 0)
              continue;
          if (t->usage != usage) {
              usage = t->usage;
  
              /* Reset digest agility for each usage/selector pair */
              mtype = DANETLS_NONE;
              ordinal = dane->dctx->mdord[t->mtype];
          }
          if (t->selector != selector) {
              selector = t->selector;
  
              /* Update per-selector state */
              OPENSSL_free(i2dbuf);
              i2dbuf = dane_i2d(cert, selector, &i2dlen);
              if (i2dbuf == NULL)
                  return -1;
  
              /* Reset digest agility for each usage/selector pair */
              mtype = DANETLS_NONE;
              ordinal = dane->dctx->mdord[t->mtype];
          } else if (t->mtype != DANETLS_MATCHING_FULL) {
              /*-
               * Digest agility:
               *
               *     <https://tools.ietf.org/html/rfc7671#section-9>
               *
               * For a fixed selector, after processing all records with the
               * highest mtype ordinal, ignore all mtypes with lower ordinals
               * other than "Full".
               */
              if (dane->dctx->mdord[t->mtype] < ordinal)
                  continue;
          }
  
          /*
           * Each time we hit a (new selector or) mtype, re-compute the relevant
           * digest, more complex caching is not worth the code space.
           */
          if (t->mtype != mtype) {
              const EVP_MD *md = dane->dctx->mdevp[mtype = t->mtype];
              cmpbuf = i2dbuf;
              cmplen = i2dlen;
  
              if (md != NULL) {
                  cmpbuf = mdbuf;
                  if (!EVP_Digest(i2dbuf, i2dlen, cmpbuf, &cmplen, md, 0)) {
                      matched = -1;
                      break;
                  }
              }
          }
  
          /*
           * Squirrel away the certificate and depth if we have a match.  Any
           * DANE match is dispositive, but with PKIX we still need to build a
           * full chain.
           */
          if (cmplen == t->dlen &&
              memcmp(cmpbuf, t->data, cmplen) == 0) {
              if (DANETLS_USAGE_BIT(usage) & DANETLS_DANE_MASK)
                  matched = 1;
              if (matched || dane->mdpth < 0) {
                  dane->mdpth = depth;
                  dane->mtlsa = t;
                  OPENSSL_free(dane->mcert);
                  dane->mcert = cert;
                  X509_up_ref(cert);
              }
              break;
          }
      }
  
      /* Clear the one-element DER cache */
      OPENSSL_free(i2dbuf);
      return matched;
  }
  
  static int check_dane_issuer(X509_STORE_CTX *ctx, int depth)
  {
      SSL_DANE *dane = ctx->dane;
      int matched = 0;
      X509 *cert;
  
      if (!DANETLS_HAS_TA(dane) || depth == 0)
          return  X509_TRUST_UNTRUSTED;
  
      /*
       * Record any DANE trust-anchor matches, for the first depth to test, if
       * there's one at that depth. (This'll be false for length 1 chains looking
       * for an exact match for the leaf certificate).
       */
      cert = sk_X509_value(ctx->chain, depth);
      if (cert != NULL && (matched = dane_match(ctx, cert, depth)) < 0)
          return  X509_TRUST_REJECTED;
      if (matched > 0) {
          ctx->num_untrusted = depth - 1;
          return  X509_TRUST_TRUSTED;
      }
  
      return  X509_TRUST_UNTRUSTED;
  }
  
  static int check_dane_pkeys(X509_STORE_CTX *ctx)
  {
      SSL_DANE *dane = ctx->dane;
      danetls_record *t;
      int num = ctx->num_untrusted;
      X509 *cert = sk_X509_value(ctx->chain, num - 1);
      int recnum = sk_danetls_record_num(dane->trecs);
      int i;
  
      for (i = 0; i < recnum; ++i) {
          t = sk_danetls_record_value(dane->trecs, i);
          if (t->usage != DANETLS_USAGE_DANE_TA ||
              t->selector != DANETLS_SELECTOR_SPKI ||
              t->mtype != DANETLS_MATCHING_FULL ||
              X509_verify(cert, t->spki) <= 0)
              continue;
  
          /* Clear any PKIX-?? matches that failed to extend to a full chain */
          X509_free(dane->mcert);
          dane->mcert = NULL;
  
          /* Record match via a bare TA public key */
          ctx->bare_ta_signed = 1;
          dane->mdpth = num - 1;
          dane->mtlsa = t;
  
          /* Prune any excess chain certificates */
          num = sk_X509_num(ctx->chain);
          for (; num > ctx->num_untrusted; --num)
              X509_free(sk_X509_pop(ctx->chain));
  
          return X509_TRUST_TRUSTED;
      }
  
      return X509_TRUST_UNTRUSTED;
  }
  
  static void dane_reset(SSL_DANE *dane)
  {
      /*
       * Reset state to verify another chain, or clear after failure.
       */
      X509_free(dane->mcert);
      dane->mcert = NULL;
      dane->mtlsa = NULL;
      dane->mdpth = -1;
      dane->pdpth = -1;
  }
  
  static int check_leaf_suiteb(X509_STORE_CTX *ctx, X509 *cert)
  {
      int err = X509_chain_check_suiteb(NULL, cert, NULL, ctx->param->flags);
  
      if (err == X509_V_OK)
          return 1;
      return verify_cb_cert(ctx, cert, 0, err);
  }
  
  static int dane_verify(X509_STORE_CTX *ctx)
  {
      X509 *cert = ctx->cert;
      SSL_DANE *dane = ctx->dane;
      int matched;
      int done;
  
      dane_reset(dane);
  
      /*-
       * When testing the leaf certificate, if we match a DANE-EE(3) record,
       * dane_match() returns 1 and we're done.  If however we match a PKIX-EE(1)
       * record, the match depth and matching TLSA record are recorded, but the
       * return value is 0, because we still need to find a PKIX trust-anchor.
       * Therefore, when DANE authentication is enabled (required), we're done
       * if:
       *   + matched < 0, internal error.
       *   + matched == 1, we matched a DANE-EE(3) record
       *   + matched == 0, mdepth < 0 (no PKIX-EE match) and there are no
       *     DANE-TA(2) or PKIX-TA(0) to test.
       */
      matched = dane_match(ctx, ctx->cert, 0);
      done = matched != 0 || (!DANETLS_HAS_TA(dane) && dane->mdpth < 0);
  
      if (done)
          X509_get_pubkey_parameters(NULL, ctx->chain);
  
      if (matched > 0) {
          /* Callback invoked as needed */
          if (!check_leaf_suiteb(ctx, cert))
              return 0;
          /* Callback invoked as needed */
          if ((dane->flags & DANE_FLAG_NO_DANE_EE_NAMECHECKS) == 0 &&
              !check_id(ctx))
              return 0;
          /* Bypass internal_verify(), issue depth 0 success callback */
          ctx->error_depth = 0;
          ctx->current_cert = cert;
          return ctx->verify_cb(1, ctx);
      }
  
      if (matched < 0) {
          ctx->error_depth = 0;
          ctx->current_cert = cert;
          ctx->error = X509_V_ERR_OUT_OF_MEM;
          return -1;
      }
  
      if (done) {
          /* Fail early, TA-based success is not possible */
          if (!check_leaf_suiteb(ctx, cert))
              return 0;
          return verify_cb_cert(ctx, cert, 0, X509_V_ERR_DANE_NO_MATCH);
      }
  
      /*
       * Chain verification for usages 0/1/2.  TLSA record matching of depth > 0
       * certificates happens in-line with building the rest of the chain.
       */
      return verify_chain(ctx);
  }
  
  /* Get issuer, without duplicate suppression */
  static int get_issuer(X509 **issuer, X509_STORE_CTX *ctx, X509 *cert)
  {
      STACK_OF(X509) *saved_chain = ctx->chain;
      int ok;
  
      ctx->chain = NULL;
      ok = ctx->get_issuer(issuer, ctx, cert);
      ctx->chain = saved_chain;
  
      return ok;
  }
  
  static int build_chain(X509_STORE_CTX *ctx)
  {
      SSL_DANE *dane = ctx->dane;
      int num = sk_X509_num(ctx->chain);
      X509 *cert = sk_X509_value(ctx->chain, num - 1);
      int ss = cert_self_signed(cert);
      STACK_OF(X509) *sktmp = NULL;
      unsigned int search;
      int may_trusted = 0;
      int may_alternate = 0;
      int trust = X509_TRUST_UNTRUSTED;
      int alt_untrusted = 0;
      int depth;
      int ok = 0;
      int i;
  
      /* Our chain starts with a single untrusted element. */
      if (!ossl_assert(num == 1 && ctx->num_untrusted == num))  {
          X509err(X509_F_BUILD_CHAIN, ERR_R_INTERNAL_ERROR);
          ctx->error = X509_V_ERR_UNSPECIFIED;
          return 0;
      }
  
  #define S_DOUNTRUSTED      (1 << 0)     /* Search untrusted chain */
  #define S_DOTRUSTED        (1 << 1)     /* Search trusted store */
  #define S_DOALTERNATE      (1 << 2)     /* Retry with pruned alternate chain */
      /*
       * Set up search policy, untrusted if possible, trusted-first if enabled.
       * If we're doing DANE and not doing PKIX-TA/PKIX-EE, we never look in the
       * trust_store, otherwise we might look there first.  If not trusted-first,
       * and alternate chains are not disabled, try building an alternate chain
       * if no luck with untrusted first.
       */
      search = (ctx->untrusted != NULL) ? S_DOUNTRUSTED : 0;
      if (DANETLS_HAS_PKIX(dane) || !DANETLS_HAS_DANE(dane)) {
          if (search == 0 || ctx->param->flags & X509_V_FLAG_TRUSTED_FIRST)
              search |= S_DOTRUSTED;
          else if (!(ctx->param->flags & X509_V_FLAG_NO_ALT_CHAINS))
              may_alternate = 1;
          may_trusted = 1;
      }
  
      /*
       * Shallow-copy the stack of untrusted certificates (with TLS, this is
       * typically the content of the peer's certificate message) so can make
       * multiple passes over it, while free to remove elements as we go.
       */
      if (ctx->untrusted && (sktmp = sk_X509_dup(ctx->untrusted)) == NULL) {
          X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
          ctx->error = X509_V_ERR_OUT_OF_MEM;
          return 0;
      }
  
      /*
       * If we got any "DANE-TA(2) Cert(0) Full(0)" trust-anchors from DNS, add
       * them to our working copy of the untrusted certificate stack.  Since the
       * caller of X509_STORE_CTX_init() may have provided only a leaf cert with
       * no corresponding stack of untrusted certificates, we may need to create
       * an empty stack first.  [ At present only the ssl library provides DANE
       * support, and ssl_verify_cert_chain() always provides a non-null stack
       * containing at least the leaf certificate, but we must be prepared for
       * this to change. ]
       */
      if (DANETLS_ENABLED(dane) && dane->certs != NULL) {
          if (sktmp == NULL && (sktmp = sk_X509_new_null()) == NULL) {
              X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
              ctx->error = X509_V_ERR_OUT_OF_MEM;
              return 0;
          }
          for (i = 0; i < sk_X509_num(dane->certs); ++i) {
              if (!sk_X509_push(sktmp, sk_X509_value(dane->certs, i))) {
                  sk_X509_free(sktmp);
                  X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
                  ctx->error = X509_V_ERR_OUT_OF_MEM;
                  return 0;
              }
          }
      }
  
      /*
       * Still absurdly large, but arithmetically safe, a lower hard upper bound
       * might be reasonable.
       */
      if (ctx->param->depth > INT_MAX/2)
          ctx->param->depth = INT_MAX/2;
  
      /*
       * Try to Extend the chain until we reach an ultimately trusted issuer.
       * Build chains up to one longer the limit, later fail if we hit the limit,
       * with an X509_V_ERR_CERT_CHAIN_TOO_LONG error code.
       */
      depth = ctx->param->depth + 1;
  
      while (search != 0) {
          X509 *x;
          X509 *xtmp = NULL;
  
          /*
           * Look in the trust store if enabled for first lookup, or we've run
           * out of untrusted issuers and search here is not disabled.  When we
           * reach the depth limit, we stop extending the chain, if by that point
           * we've not found a trust-anchor, any trusted chain would be too long.
           *
           * The error reported to the application verify callback is at the
           * maximal valid depth with the current certificate equal to the last
           * not ultimately-trusted issuer.  For example, with verify_depth = 0,
           * the callback will report errors at depth=1 when the immediate issuer
           * of the leaf certificate is not a trust anchor.  No attempt will be
           * made to locate an issuer for that certificate, since such a chain
           * would be a-priori too long.
           */
          if ((search & S_DOTRUSTED) != 0) {
              i = num = sk_X509_num(ctx->chain);
              if ((search & S_DOALTERNATE) != 0) {
                  /*
                   * As high up the chain as we can, look for an alternative
                   * trusted issuer of an untrusted certificate that currently
                   * has an untrusted issuer.  We use the alt_untrusted variable
                   * to track how far up the chain we find the first match.  It
                   * is only if and when we find a match, that we prune the chain
                   * and reset ctx->num_untrusted to the reduced count of
                   * untrusted certificates.  While we're searching for such a
                   * match (which may never be found), it is neither safe nor
                   * wise to preemptively modify either the chain or
                   * ctx->num_untrusted.
                   *
                   * Note, like ctx->num_untrusted, alt_untrusted is a count of
                   * untrusted certificates, not a "depth".
                   */
                  i = alt_untrusted;
              }
              x = sk_X509_value(ctx->chain, i-1);
  
              ok = (depth < num) ? 0 : get_issuer(&xtmp, ctx, x);
  
              if (ok < 0) {
                  trust = X509_TRUST_REJECTED;
                  ctx->error = X509_V_ERR_STORE_LOOKUP;
                  search = 0;
                  continue;
              }
  
              if (ok > 0) {
                  /*
                   * Alternative trusted issuer for a mid-chain untrusted cert?
                   * Pop the untrusted cert's successors and retry.  We might now
                   * be able to complete a valid chain via the trust store.  Note
                   * that despite the current trust-store match we might still
                   * fail complete the chain to a suitable trust-anchor, in which
                   * case we may prune some more untrusted certificates and try
                   * again.  Thus the S_DOALTERNATE bit may yet be turned on
                   * again with an even shorter untrusted chain!
                   *
                   * If in the process we threw away our matching PKIX-TA trust
                   * anchor, reset DANE trust.  We might find a suitable trusted
                   * certificate among the ones from the trust store.
                   */
                  if ((search & S_DOALTERNATE) != 0) {
                      if (!ossl_assert(num > i && i > 0 && ss == 0)) {
                          X509err(X509_F_BUILD_CHAIN, ERR_R_INTERNAL_ERROR);
                          X509_free(xtmp);
                          trust = X509_TRUST_REJECTED;
                          ctx->error = X509_V_ERR_UNSPECIFIED;
                          search = 0;
                          continue;
                      }
                      search &= ~S_DOALTERNATE;
                      for (; num > i; --num)
                          X509_free(sk_X509_pop(ctx->chain));
                      ctx->num_untrusted = num;
  
                      if (DANETLS_ENABLED(dane) &&
                          dane->mdpth >= ctx->num_untrusted) {
                          dane->mdpth = -1;
                          X509_free(dane->mcert);
                          dane->mcert = NULL;
                      }
                      if (DANETLS_ENABLED(dane) &&
                          dane->pdpth >= ctx->num_untrusted)
                          dane->pdpth = -1;
                  }
  
                  /*
                   * Self-signed untrusted certificates get replaced by their
                   * trusted matching issuer.  Otherwise, grow the chain.
                   */
                  if (ss == 0) {
                      if (!sk_X509_push(ctx->chain, x = xtmp)) {
                          X509_free(xtmp);
                          X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
                          trust = X509_TRUST_REJECTED;
                          ctx->error = X509_V_ERR_OUT_OF_MEM;
                          search = 0;
                          continue;
                      }
                      ss = cert_self_signed(x);
                  } else if (num == ctx->num_untrusted) {
                      /*
                       * We have a self-signed certificate that has the same
                       * subject name (and perhaps keyid and/or serial number) as
                       * a trust-anchor.  We must have an exact match to avoid
                       * possible impersonation via key substitution etc.
                       */
                      if (X509_cmp(x, xtmp) != 0) {
                          /* Self-signed untrusted mimic. */
                          X509_free(xtmp);
                          ok = 0;
                      } else {
                          X509_free(x);
                          ctx->num_untrusted = --num;
                          (void) sk_X509_set(ctx->chain, num, x = xtmp);
                      }
                  }
  
                  /*
                   * We've added a new trusted certificate to the chain, recheck
                   * trust.  If not done, and not self-signed look deeper.
                   * Whether or not we're doing "trusted first", we no longer
                   * look for untrusted certificates from the peer's chain.
                   *
                   * At this point ctx->num_trusted and num must reflect the
                   * correct number of untrusted certificates, since the DANE
                   * logic in check_trust() depends on distinguishing CAs from
                   * "the wire" from CAs from the trust store.  In particular, the
                   * certificate at depth "num" should be the new trusted
                   * certificate with ctx->num_untrusted <= num.
                   */
                  if (ok) {
                      if (!ossl_assert(ctx->num_untrusted <= num)) {
                          X509err(X509_F_BUILD_CHAIN, ERR_R_INTERNAL_ERROR);
                          trust = X509_TRUST_REJECTED;
                          ctx->error = X509_V_ERR_UNSPECIFIED;
                          search = 0;
                          continue;
                      }
                      search &= ~S_DOUNTRUSTED;
                      switch (trust = check_trust(ctx, num)) {
                      case X509_TRUST_TRUSTED:
                      case X509_TRUST_REJECTED:
                          search = 0;
                          continue;
                      }
                      if (ss == 0)
                          continue;
                  }
              }
  
              /*
               * No dispositive decision, and either self-signed or no match, if
               * we were doing untrusted-first, and alt-chains are not disabled,
               * do that, by repeatedly losing one untrusted element at a time,
               * and trying to extend the shorted chain.
               */
              if ((search & S_DOUNTRUSTED) == 0) {
                  /* Continue search for a trusted issuer of a shorter chain? */
                  if ((search & S_DOALTERNATE) != 0 && --alt_untrusted > 0)
                      continue;
                  /* Still no luck and no fallbacks left? */
                  if (!may_alternate || (search & S_DOALTERNATE) != 0 ||
                      ctx->num_untrusted < 2)
                      break;
                  /* Search for a trusted issuer of a shorter chain */
                  search |= S_DOALTERNATE;
                  alt_untrusted = ctx->num_untrusted - 1;
                  ss = 0;
              }
          }
  
          /*
           * Extend chain with peer-provided certificates
           */
          if ((search & S_DOUNTRUSTED) != 0) {
              num = sk_X509_num(ctx->chain);
              if (!ossl_assert(num == ctx->num_untrusted)) {
                  X509err(X509_F_BUILD_CHAIN, ERR_R_INTERNAL_ERROR);
                  trust = X509_TRUST_REJECTED;
                  ctx->error = X509_V_ERR_UNSPECIFIED;
                  search = 0;
                  continue;
              }
              x = sk_X509_value(ctx->chain, num-1);
  
              /*
               * Once we run out of untrusted issuers, we stop looking for more
               * and start looking only in the trust store if enabled.
               */
              xtmp = (ss || depth < num) ? NULL : find_issuer(ctx, sktmp, x);
              if (xtmp == NULL) {
                  search &= ~S_DOUNTRUSTED;
                  if (may_trusted)
                      search |= S_DOTRUSTED;
                  continue;
              }
  
              /* Drop this issuer from future consideration */
              (void) sk_X509_delete_ptr(sktmp, xtmp);
  
              if (!sk_X509_push(ctx->chain, xtmp)) {
                  X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
                  trust = X509_TRUST_REJECTED;
                  ctx->error = X509_V_ERR_OUT_OF_MEM;
                  search = 0;
                  continue;
              }
  
              X509_up_ref(x = xtmp);
              ++ctx->num_untrusted;
              ss = cert_self_signed(xtmp);
  
              /*
               * Check for DANE-TA trust of the topmost untrusted certificate.
               */
              switch (trust = check_dane_issuer(ctx, ctx->num_untrusted - 1)) {
              case X509_TRUST_TRUSTED:
              case X509_TRUST_REJECTED:
                  search = 0;
                  continue;
              }
          }
      }
      sk_X509_free(sktmp);
  
      /*
       * Last chance to make a trusted chain, either bare DANE-TA public-key
       * signers, or else direct leaf PKIX trust.
       */
      num = sk_X509_num(ctx->chain);
      if (num <= depth) {
          if (trust == X509_TRUST_UNTRUSTED && DANETLS_HAS_DANE_TA(dane))
              trust = check_dane_pkeys(ctx);
          if (trust == X509_TRUST_UNTRUSTED && num == ctx->num_untrusted)
              trust = check_trust(ctx, num);
      }
  
      switch (trust) {
      case X509_TRUST_TRUSTED:
          return 1;
      case X509_TRUST_REJECTED:
          /* Callback already issued */
          return 0;
      case X509_TRUST_UNTRUSTED:
      default:
          num = sk_X509_num(ctx->chain);
          if (num > depth)
              return verify_cb_cert(ctx, NULL, num-1,
                                    X509_V_ERR_CERT_CHAIN_TOO_LONG);
          if (DANETLS_ENABLED(dane) &&
              (!DANETLS_HAS_PKIX(dane) || dane->pdpth >= 0))
              return verify_cb_cert(ctx, NULL, num-1, X509_V_ERR_DANE_NO_MATCH);
          if (ss && sk_X509_num(ctx->chain) == 1)
              return verify_cb_cert(ctx, NULL, num-1,
                                    X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT);
          if (ss)
              return verify_cb_cert(ctx, NULL, num-1,
                                    X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN);
          if (ctx->num_untrusted < num)
              return verify_cb_cert(ctx, NULL, num-1,
                                    X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT);
          return verify_cb_cert(ctx, NULL, num-1,
                                X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY);
      }
  }
  
  static const int minbits_table[] = { 80, 112, 128, 192, 256 };
  static const int NUM_AUTH_LEVELS = OSSL_NELEM(minbits_table);
  
  /*
   * Check whether the public key of ``cert`` meets the security level of
   * ``ctx``.
   *
   * Returns 1 on success, 0 otherwise.
   */
  static int check_key_level(X509_STORE_CTX *ctx, X509 *cert)
  {
      EVP_PKEY *pkey = X509_get0_pubkey(cert);
      int level = ctx->param->auth_level;
  
      /* Unsupported or malformed keys are not secure */
      if (pkey == NULL)
          return 0;
  
      if (level <= 0)
          return 1;
      if (level > NUM_AUTH_LEVELS)
          level = NUM_AUTH_LEVELS;
  
      return EVP_PKEY_security_bits(pkey) >= minbits_table[level - 1];
  }
  
  /*
   * Check whether the signature digest algorithm of ``cert`` meets the security
   * level of ``ctx``.  Should not be checked for trust anchors (whether
   * self-signed or otherwise).
   *
   * Returns 1 on success, 0 otherwise.
   */
  static int check_sig_level(X509_STORE_CTX *ctx, X509 *cert)
  {
      int secbits = -1;
      int level = ctx->param->auth_level;
  
      if (level <= 0)
          return 1;
      if (level > NUM_AUTH_LEVELS)
          level = NUM_AUTH_LEVELS;
  
      if (!X509_get_signature_info(cert, NULL, NULL, &secbits, NULL))
          return 0;
  
      return secbits >= minbits_table[level - 1];
  }
  