text: /*
   * Copyright 2006-2016 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 "internal/cryptlib.h"
  #include <openssl/x509.h>
  #include <openssl/ec.h>
  #include <openssl/rand.h>
  #include "internal/asn1_int.h"
  #include "internal/evp_int.h"
  #include "ec_lcl.h"
  
  #define X25519_KEYLEN        32
  #define X25519_BITS          253
  #define X25519_SECURITY_BITS 128
  
  typedef struct {
      unsigned char pubkey[X25519_KEYLEN];
      unsigned char *privkey;
  } X25519_KEY;
  
  typedef enum {
      X25519_PUBLIC,
      X25519_PRIVATE,
      X25519_KEYGEN
  } ecx_key_op_t;
  
  /* Setup EVP_PKEY using public, private or generation */
  static int ecx_key_op(EVP_PKEY *pkey, X509_ALGOR *palg,
                        const unsigned char *p, int plen, ecx_key_op_t op)
  {
      X25519_KEY *xkey;
  
      if (op != X25519_KEYGEN) {
          if (palg != NULL) {
              int ptype;
  
              /* Algorithm parameters must be absent */
              X509_ALGOR_get0(NULL, &ptype, NULL, palg);
              if (ptype != V_ASN1_UNDEF) {
                  ECerr(EC_F_ECX_KEY_OP, EC_R_INVALID_ENCODING);
                  return 0;
              }
          }
  
          if (p == NULL || plen != X25519_KEYLEN) {
              ECerr(EC_F_ECX_KEY_OP, EC_R_INVALID_ENCODING);
              return 0;
          }
      }
  
      xkey = OPENSSL_zalloc(sizeof(*xkey));
      if (xkey == NULL) {
          ECerr(EC_F_ECX_KEY_OP, ERR_R_MALLOC_FAILURE);
          return 0;
      }
  
      if (op == X25519_PUBLIC) {
          memcpy(xkey->pubkey, p, plen);
      } else {
          xkey->privkey = OPENSSL_secure_malloc(X25519_KEYLEN);
          if (xkey->privkey == NULL) {
              ECerr(EC_F_ECX_KEY_OP, ERR_R_MALLOC_FAILURE);
              OPENSSL_free(xkey);
              return 0;
          }
          if (op == X25519_KEYGEN) {
              if (RAND_bytes(xkey->privkey, X25519_KEYLEN) <= 0) {
                  OPENSSL_secure_free(xkey->privkey);
                  OPENSSL_free(xkey);
                  return 0;
              }
              xkey->privkey[0] &= 248;
              xkey->privkey[31] &= 127;
              xkey->privkey[31] |= 64;
          } else {
              memcpy(xkey->privkey, p, X25519_KEYLEN);
          }
          X25519_public_from_private(xkey->pubkey, xkey->privkey);
      }
  
      EVP_PKEY_assign(pkey, NID_X25519, xkey);
      return 1;
  }
  
  static int ecx_pub_encode(X509_PUBKEY *pk, const EVP_PKEY *pkey)
  {
      const X25519_KEY *xkey = pkey->pkey.ptr;
      unsigned char *penc;
  
      if (xkey == NULL) {
          ECerr(EC_F_ECX_PUB_ENCODE, EC_R_INVALID_KEY);
          return 0;
      }
  
      penc = OPENSSL_memdup(xkey->pubkey, X25519_KEYLEN);
      if (penc == NULL) {
          ECerr(EC_F_ECX_PUB_ENCODE, ERR_R_MALLOC_FAILURE);
          return 0;
      }
  
      if (!X509_PUBKEY_set0_param(pk, OBJ_nid2obj(NID_X25519), V_ASN1_UNDEF,
                                  NULL, penc, X25519_KEYLEN)) {
          OPENSSL_free(penc);
          ECerr(EC_F_ECX_PUB_ENCODE, ERR_R_MALLOC_FAILURE);
          return 0;
      }
      return 1;
  }
  
  static int ecx_pub_decode(EVP_PKEY *pkey, X509_PUBKEY *pubkey)
  {
      const unsigned char *p;
      int pklen;
      X509_ALGOR *palg;
  
      if (!X509_PUBKEY_get0_param(NULL, &p, &pklen, &palg, pubkey))
          return 0;
      return ecx_key_op(pkey, palg, p, pklen, X25519_PUBLIC);
  }
  
  static int ecx_pub_cmp(const EVP_PKEY *a, const EVP_PKEY *b)
  {
      const X25519_KEY *akey = a->pkey.ptr;
      const X25519_KEY *bkey = b->pkey.ptr;
  
      if (akey == NULL || bkey == NULL)
          return -2;
      return !CRYPTO_memcmp(akey->pubkey, bkey->pubkey, X25519_KEYLEN);
  }
  
  static int ecx_priv_decode(EVP_PKEY *pkey, PKCS8_PRIV_KEY_INFO *p8)
  {
      const unsigned char *p;
      int plen;
      ASN1_OCTET_STRING *oct = NULL;
      X509_ALGOR *palg;
      int rv;
  
      if (!PKCS8_pkey_get0(NULL, &p, &plen, &palg, p8))
          return 0;
  
      oct = d2i_ASN1_OCTET_STRING(NULL, &p, plen);
      if (oct == NULL) {
          p = NULL;
          plen = 0;
      } else {
          p = ASN1_STRING_data(oct);
          plen = ASN1_STRING_length(oct);
      }
  
      rv = ecx_key_op(pkey, palg, p, plen, X25519_PRIVATE);
      ASN1_OCTET_STRING_free(oct);
      return rv;
  }
  
  static int ecx_priv_encode(PKCS8_PRIV_KEY_INFO *p8, const EVP_PKEY *pkey)
  {
      const X25519_KEY *xkey = pkey->pkey.ptr;
      ASN1_OCTET_STRING oct;
      unsigned char *penc = NULL;
      int penclen;
  
      if (xkey == NULL || xkey->privkey == NULL) {
          ECerr(EC_F_ECX_PRIV_ENCODE, EC_R_INVALID_PRIVATE_KEY);
          return 0;
      }
  
      oct.data = xkey->privkey;
      oct.length = X25519_KEYLEN;
      oct.flags = 0;
  
      penclen = i2d_ASN1_OCTET_STRING(&oct, &penc);
      if (penclen < 0) {
          ECerr(EC_F_ECX_PRIV_ENCODE, ERR_R_MALLOC_FAILURE);
          return 0;
      }
  
      if (!PKCS8_pkey_set0(p8, OBJ_nid2obj(NID_X25519), 0,
                           V_ASN1_UNDEF, NULL, penc, penclen)) {
          OPENSSL_clear_free(penc, penclen);
          ECerr(EC_F_ECX_PRIV_ENCODE, ERR_R_MALLOC_FAILURE);
          return 0;
      }
  
      return 1;
  }
  
  static int ecx_size(const EVP_PKEY *pkey)
  {
      return X25519_KEYLEN;
  }
  
  static int ecx_bits(const EVP_PKEY *pkey)
  {
      return X25519_BITS;
  }
  
  static int ecx_security_bits(const EVP_PKEY *pkey)
  {
      return X25519_SECURITY_BITS;
  }
  
  static void ecx_free(EVP_PKEY *pkey)
  {
      X25519_KEY *xkey = pkey->pkey.ptr;
  
      if (xkey)
          OPENSSL_secure_free(xkey->privkey);
      OPENSSL_free(xkey);
  }
  
  /* "parameters" are always equal */
  static int ecx_cmp_parameters(const EVP_PKEY *a, const EVP_PKEY *b)
  {
      return 1;
  }
  
  static int ecx_key_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                           ASN1_PCTX *ctx, ecx_key_op_t op)
  {
      const X25519_KEY *xkey = pkey->pkey.ptr;
  
      if (op == X25519_PRIVATE) {
          if (xkey == NULL || xkey->privkey == NULL) {
              if (BIO_printf(bp, "%*s<INVALID PRIVATE KEY>\n", indent, "") <= 0)
                  return 0;
              return 1;
          }
          if (BIO_printf(bp, "%*sX25519 Private-Key:\n", indent, "") <= 0)
              return 0;
          if (BIO_printf(bp, "%*spriv:\n", indent, "") <= 0)
              return 0;
          if (ASN1_buf_print(bp, xkey->privkey, X25519_KEYLEN, indent + 4) == 0)
              return 0;
      } else {
          if (xkey == NULL) {
              if (BIO_printf(bp, "%*s<INVALID PUBLIC KEY>\n", indent, "") <= 0)
                  return 0;
              return 1;
          }
          if (BIO_printf(bp, "%*sX25519 Public-Key:\n", indent, "") <= 0)
              return 0;
      }
      if (BIO_printf(bp, "%*spub:\n", indent, "") <= 0)
          return 0;
      if (ASN1_buf_print(bp, xkey->pubkey, X25519_KEYLEN, indent + 4) == 0)
          return 0;
      return 1;
  }
  
  static int ecx_priv_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                            ASN1_PCTX *ctx)
  {
      return ecx_key_print(bp, pkey, indent, ctx, X25519_PRIVATE);
  }
  
  static int ecx_pub_print(BIO *bp, const EVP_PKEY *pkey, int indent,
                           ASN1_PCTX *ctx)
  {
      return ecx_key_print(bp, pkey, indent, ctx, X25519_PUBLIC);
  }
  
  static int ecx_ctrl(EVP_PKEY *pkey, int op, long arg1, void *arg2)
  {
      switch (op) {
  
      case ASN1_PKEY_CTRL_SET1_TLS_ENCPT:
          return ecx_key_op(pkey, NULL, arg2, arg1, X25519_PUBLIC);
  
      case ASN1_PKEY_CTRL_GET1_TLS_ENCPT:
          if (pkey->pkey.ptr != NULL) {
              const X25519_KEY *xkey = pkey->pkey.ptr;
              unsigned char **ppt = arg2;
              *ppt = OPENSSL_memdup(xkey->pubkey, X25519_KEYLEN);
              if (*ppt != NULL)
                  return X25519_KEYLEN;
          }
          return 0;
  
      case ASN1_PKEY_CTRL_DEFAULT_MD_NID:
          *(int *)arg2 = NID_sha256;
          return 2;
  
      default:
          return -2;
  
      }
  }
  
  const EVP_PKEY_ASN1_METHOD ecx25519_asn1_meth = {
      NID_X25519,
      NID_X25519,
      0,
      "X25519",
      "OpenSSL X25519 algorithm",
  
      ecx_pub_decode,
      ecx_pub_encode,
      ecx_pub_cmp,
      ecx_pub_print,
  
      ecx_priv_decode,
      ecx_priv_encode,
      ecx_priv_print,
  
      ecx_size,
      ecx_bits,
      ecx_security_bits,
  
      0, 0, 0, 0,
      ecx_cmp_parameters,
      0, 0,
  
      ecx_free,
      ecx_ctrl,
      NULL,
      NULL
  };
  
  static int pkey_ecx_keygen(EVP_PKEY_CTX *ctx, EVP_PKEY *pkey)
  {
      return ecx_key_op(pkey, NULL, NULL, 0, X25519_KEYGEN);
  }
  
  static int pkey_ecx_derive(EVP_PKEY_CTX *ctx, unsigned char *key,
                             size_t *keylen)
  {
      const X25519_KEY *pkey, *peerkey;
  
      if (ctx->pkey == NULL || ctx->peerkey == NULL) {
          ECerr(EC_F_PKEY_ECX_DERIVE, EC_R_KEYS_NOT_SET);
          return 0;
      }
      pkey = ctx->pkey->pkey.ptr;
      peerkey = ctx->peerkey->pkey.ptr;
      if (pkey == NULL || pkey->privkey == NULL) {
          ECerr(EC_F_PKEY_ECX_DERIVE, EC_R_INVALID_PRIVATE_KEY);
          return 0;
      }
      if (peerkey == NULL) {
          ECerr(EC_F_PKEY_ECX_DERIVE, EC_R_INVALID_PEER_KEY);
          return 0;
      }
      *keylen = X25519_KEYLEN;
      if (key != NULL && X25519(key, pkey->privkey, peerkey->pubkey) == 0)
          return 0;
      return 1;
  }
  
  static int pkey_ecx_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)
  {
      /* Only need to handle peer key for derivation */
      if (type == EVP_PKEY_CTRL_PEER_KEY)
          return 1;
      return -2;
  }
  
  const EVP_PKEY_METHOD ecx25519_pkey_meth = {
      NID_X25519,
      0, 0, 0, 0, 0, 0, 0,
      pkey_ecx_keygen,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      pkey_ecx_derive,
      pkey_ecx_ctrl,
      0
  };
  