text: /*
  <<<<<<< HEAD
   * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
  =======
   * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
  >>>>>>> 6e3ba20dc49ccbf12ff4c27a4d8b84dcbeb71654
   *
   * Licensed under the Apache License 2.0 (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
   */
  
  /*
   * DSA low level APIs are deprecated for public use, but still ok for
   * internal use.
   */
  #include "internal/deprecated.h"
  
  #include <stdio.h>
  #include "internal/cryptlib.h"
  #include "crypto/bn.h"
  #include <openssl/bn.h>
  #include <openssl/sha.h>
  #include "dsa_local.h"
  #include <openssl/asn1.h>
  
  static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
  static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
                                      BIGNUM **rp);
  static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
                            BIGNUM **rp, const unsigned char *dgst, int dlen);
  static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
                           DSA_SIG *sig, DSA *dsa);
  static int dsa_init(DSA *dsa);
  static int dsa_finish(DSA *dsa);
  static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
                                        BN_CTX *ctx);
  
  static DSA_METHOD openssl_dsa_meth = {
      "OpenSSL DSA method",
      dsa_do_sign,
      dsa_sign_setup_no_digest,
      dsa_do_verify,
      NULL,                       /* dsa_mod_exp, */
      NULL,                       /* dsa_bn_mod_exp, */
      dsa_init,
      dsa_finish,
      DSA_FLAG_FIPS_METHOD,
      NULL,
      NULL,
      NULL
  };
  
  static const DSA_METHOD *default_DSA_method = &openssl_dsa_meth;
  
  #ifndef FIPS_MODULE
  void DSA_set_default_method(const DSA_METHOD *meth)
  {
      default_DSA_method = meth;
  }
  #endif /* FIPS_MODULE */
  
  const DSA_METHOD *DSA_get_default_method(void)
  {
      return default_DSA_method;
  }
  
  const DSA_METHOD *DSA_OpenSSL(void)
  {
      return &openssl_dsa_meth;
  }
  
  DSA_SIG *dsa_do_sign_int(const unsigned char *dgst, int dlen, DSA *dsa)
  {
      BIGNUM *kinv = NULL;
      BIGNUM *m, *blind, *blindm, *tmp;
      BN_CTX *ctx = NULL;
      int reason = ERR_R_BN_LIB;
      DSA_SIG *ret = NULL;
      int rv = 0;
  
      if (dsa->params.p == NULL
          || dsa->params.q == NULL
          || dsa->params.g == NULL) {
          reason = DSA_R_MISSING_PARAMETERS;
          goto err;
      }
      if (dsa->priv_key == NULL) {
          reason = DSA_R_MISSING_PRIVATE_KEY;
          goto err;
      }
  
      ret = DSA_SIG_new();
      if (ret == NULL)
          goto err;
      ret->r = BN_new();
      ret->s = BN_new();
      if (ret->r == NULL || ret->s == NULL)
          goto err;
  
      ctx = BN_CTX_new_ex(dsa->libctx);
      if (ctx == NULL)
          goto err;
      m = BN_CTX_get(ctx);
      blind = BN_CTX_get(ctx);
      blindm = BN_CTX_get(ctx);
      tmp = BN_CTX_get(ctx);
      if (tmp == NULL)
          goto err;
  
   redo:
      if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
          goto err;
  
      if (dlen > BN_num_bytes(dsa->params.q))
          /*
           * if the digest length is greater than the size of q use the
           * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
           * 4.2
           */
          dlen = BN_num_bytes(dsa->params.q);
      if (BN_bin2bn(dgst, dlen, m) == NULL)
          goto err;
  
      /*
       * The normal signature calculation is:
       *
       *   s := k^-1 * (m + r * priv_key) mod q
       *
       * We will blind this to protect against side channel attacks
       *
       *   s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
       */
  
      /* Generate a blinding value */
      do {
          if (!BN_priv_rand_ex(blind, BN_num_bits(dsa->params.q) - 1,
                               BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, ctx))
              goto err;
      } while (BN_is_zero(blind));
      BN_set_flags(blind, BN_FLG_CONSTTIME);
      BN_set_flags(blindm, BN_FLG_CONSTTIME);
      BN_set_flags(tmp, BN_FLG_CONSTTIME);
  
      /* tmp := blind * priv_key * r mod q */
      if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->params.q, ctx))
          goto err;
      if (!BN_mod_mul(tmp, tmp, ret->r, dsa->params.q, ctx))
          goto err;
  
      /* blindm := blind * m mod q */
      if (!BN_mod_mul(blindm, blind, m, dsa->params.q, ctx))
          goto err;
  
      /* s : = (blind * priv_key * r) + (blind * m) mod q */
      if (!BN_mod_add_quick(ret->s, tmp, blindm, dsa->params.q))
          goto err;
  
      /* s := s * k^-1 mod q */
      if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->params.q, ctx))
          goto err;
  
      /* s:= s * blind^-1 mod q */
      if (BN_mod_inverse(blind, blind, dsa->params.q, ctx) == NULL)
          goto err;
      if (!BN_mod_mul(ret->s, ret->s, blind, dsa->params.q, ctx))
          goto err;
  
      /*
       * Redo if r or s is zero as required by FIPS 186-3: this is very
       * unlikely.
       */
      if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
          goto redo;
  
      rv = 1;
  
   err:
      if (rv == 0) {
          ERR_raise(ERR_LIB_DSA, reason);
          DSA_SIG_free(ret);
          ret = NULL;
      }
      BN_CTX_free(ctx);
      BN_clear_free(kinv);
      return ret;
  }
  
  static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
  {
      return dsa_do_sign_int(dgst, dlen, dsa);
  }
  
  static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
                                      BIGNUM **kinvp, BIGNUM **rp)
  {
      return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
  }
  
  static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
                            BIGNUM **kinvp, BIGNUM **rp,
                            const unsigned char *dgst, int dlen)
  {
      BN_CTX *ctx = NULL;
      BIGNUM *k, *kinv = NULL, *r = *rp;
      BIGNUM *l;
      int ret = 0;
      int q_bits, q_words;
  <<<<<<< HEAD
  
      if (!dsa->params.p || !dsa->params.q || !dsa->params.g) {
          ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PARAMETERS);
          return 0;
      }
  =======
  >>>>>>> 6e3ba20dc49ccbf12ff4c27a4d8b84dcbeb71654
  
      /* Reject obviously invalid parameters */
      if (BN_is_zero(dsa->params.p)
          || BN_is_zero(dsa->params.q)
          || BN_is_zero(dsa->params.g)) {
          ERR_raise(ERR_LIB_DSA, DSA_R_INVALID_PARAMETERS);
          return 0;
      }
      if (dsa->priv_key == NULL) {
          ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PRIVATE_KEY);
          return 0;
      }
  
      /* Reject obviously invalid parameters */
      if (BN_is_zero(dsa->p) || BN_is_zero(dsa->q) || BN_is_zero(dsa->g)) {
          DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_INVALID_PARAMETERS);
          return 0;
      }
      if (dsa->priv_key == NULL) {
          DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PRIVATE_KEY);
          return 0;
      }
  
      k = BN_new();
      l = BN_new();
      if (k == NULL || l == NULL)
          goto err;
  
      if (ctx_in == NULL) {
          /* if you don't pass in ctx_in you get a default libctx */
          if ((ctx = BN_CTX_new_ex(NULL)) == NULL)
              goto err;
      } else
          ctx = ctx_in;
  
      /* Preallocate space */
  <<<<<<< HEAD
      q_bits = BN_num_bits(dsa->params.q);
      q_words = bn_get_top(dsa->params.q);
  =======
      q_bits = BN_num_bits(dsa->q);
      q_words = bn_get_top(dsa->q);
  >>>>>>> 6e3ba20dc49ccbf12ff4c27a4d8b84dcbeb71654
      if (!bn_wexpand(k, q_words + 2)
          || !bn_wexpand(l, q_words + 2))
          goto err;
  
      /* Get random k */
      do {
          if (dgst != NULL) {
              /*
               * We calculate k from SHA512(private_key + H(message) + random).
               * This protects the private key from a weak PRNG.
               */
              if (!BN_generate_dsa_nonce(k, dsa->params.q, dsa->priv_key, dgst,
                                         dlen, ctx))
                  goto err;
          } else if (!BN_priv_rand_range_ex(k, dsa->params.q, ctx))
              goto err;
      } while (BN_is_zero(k));
  
      BN_set_flags(k, BN_FLG_CONSTTIME);
      BN_set_flags(l, BN_FLG_CONSTTIME);
  
      if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
          if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
                                      dsa->lock, dsa->params.p, ctx))
              goto err;
      }
  
      /* Compute r = (g^k mod p) mod q */
  
      /*
       * We do not want timing information to leak the length of k, so we
       * compute G^k using an equivalent scalar of fixed bit-length.
       *
       * We unconditionally perform both of these additions to prevent a
       * small timing information leakage.  We then choose the sum that is
       * one bit longer than the modulus.
       *
       * There are some concerns about the efficacy of doing this.  More
       * specifically refer to the discussion starting with:
       *     https://github.com/openssl/openssl/pull/7486#discussion_r228323705
       * The fix is to rework BN so these gymnastics aren't required.
       */
  <<<<<<< HEAD
      if (!BN_add(l, k, dsa->params.q)
          || !BN_add(k, l, dsa->params.q))
  =======
      if (!BN_add(l, k, dsa->q)
          || !BN_add(k, l, dsa->q))
  >>>>>>> 6e3ba20dc49ccbf12ff4c27a4d8b84dcbeb71654
          goto err;
  
      BN_consttime_swap(BN_is_bit_set(l, q_bits), k, l, q_words + 2);
  
      if ((dsa)->meth->bn_mod_exp != NULL) {
              if (!dsa->meth->bn_mod_exp(dsa, r, dsa->params.g, k, dsa->params.p,
                                         ctx, dsa->method_mont_p))
                  goto err;
      } else {
              if (!BN_mod_exp_mont(r, dsa->params.g, k, dsa->params.p, ctx,
                                   dsa->method_mont_p))
                  goto err;
      }
  
      if (!BN_mod(r, r, dsa->params.q, ctx))
          goto err;
  
      /* Compute part of 's = inv(k) (m + xr) mod q' */
  <<<<<<< HEAD
      if ((kinv = dsa_mod_inverse_fermat(k, dsa->params.q, ctx)) == NULL)
  =======
      if ((kinv = dsa_mod_inverse_fermat(k, dsa->q, ctx)) == NULL)
  >>>>>>> 6e3ba20dc49ccbf12ff4c27a4d8b84dcbeb71654
          goto err;
  
      BN_clear_free(*kinvp);
      *kinvp = kinv;
      kinv = NULL;
      ret = 1;
   err:
      if (!ret)
          ERR_raise(ERR_LIB_DSA, ERR_R_BN_LIB);
      if (ctx != ctx_in)
          BN_CTX_free(ctx);
      BN_clear_free(k);
      BN_clear_free(l);
      return ret;
  }
  
  static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
                           DSA_SIG *sig, DSA *dsa)
  {
      BN_CTX *ctx;
      BIGNUM *u1, *u2, *t1;
      BN_MONT_CTX *mont = NULL;
      const BIGNUM *r, *s;
      int ret = -1, i;
  
      if (dsa->params.p == NULL
          || dsa->params.q == NULL
          || dsa->params.g == NULL) {
          ERR_raise(ERR_LIB_DSA, DSA_R_MISSING_PARAMETERS);
          return -1;
      }
  
      i = BN_num_bits(dsa->params.q);
      /* fips 186-3 allows only different sizes for q */
      if (i != 160 && i != 224 && i != 256) {
          ERR_raise(ERR_LIB_DSA, DSA_R_BAD_Q_VALUE);
          return -1;
      }
  
      if (BN_num_bits(dsa->params.p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
          ERR_raise(ERR_LIB_DSA, DSA_R_MODULUS_TOO_LARGE);
          return -1;
      }
      u1 = BN_new();
      u2 = BN_new();
      t1 = BN_new();
      ctx = BN_CTX_new_ex(NULL); /* verify does not need a libctx */
      if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
          goto err;
  
      DSA_SIG_get0(sig, &r, &s);
  
      if (BN_is_zero(r) || BN_is_negative(r) ||
          BN_ucmp(r, dsa->params.q) >= 0) {
          ret = 0;
          goto err;
      }
      if (BN_is_zero(s) || BN_is_negative(s) ||
          BN_ucmp(s, dsa->params.q) >= 0) {
          ret = 0;
          goto err;
      }
  
      /*
       * Calculate W = inv(S) mod Q save W in u2
       */
      if ((BN_mod_inverse(u2, s, dsa->params.q, ctx)) == NULL)
          goto err;
  
      /* save M in u1 */
      if (dgst_len > (i >> 3))
          /*
           * if the digest length is greater than the size of q use the
           * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
           * 4.2
           */
          dgst_len = (i >> 3);
      if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
          goto err;
  
      /* u1 = M * w mod q */
      if (!BN_mod_mul(u1, u1, u2, dsa->params.q, ctx))
          goto err;
  
      /* u2 = r * w mod q */
      if (!BN_mod_mul(u2, r, u2, dsa->params.q, ctx))
          goto err;
  
      if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
          mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
                                        dsa->lock, dsa->params.p, ctx);
          if (!mont)
              goto err;
      }
  
      if (dsa->meth->dsa_mod_exp != NULL) {
          if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->params.g, u1, dsa->pub_key, u2,
                                      dsa->params.p, ctx, mont))
              goto err;
      } else {
          if (!BN_mod_exp2_mont(t1, dsa->params.g, u1, dsa->pub_key, u2,
                                dsa->params.p, ctx, mont))
              goto err;
      }
  
      /* let u1 = u1 mod q */
      if (!BN_mod(u1, t1, dsa->params.q, ctx))
          goto err;
  
      /*
       * V is now in u1.  If the signature is correct, it will be equal to R.
       */
      ret = (BN_ucmp(u1, r) == 0);
  
   err:
      if (ret < 0)
          ERR_raise(ERR_LIB_DSA, ERR_R_BN_LIB);
      BN_CTX_free(ctx);
      BN_free(u1);
      BN_free(u2);
      BN_free(t1);
      return ret;
  }
  
  static int dsa_init(DSA *dsa)
  {
      dsa->flags |= DSA_FLAG_CACHE_MONT_P;
      ossl_ffc_params_init(&dsa->params);
      dsa->dirty_cnt++;
      return 1;
  }
  
  static int dsa_finish(DSA *dsa)
  {
      BN_MONT_CTX_free(dsa->method_mont_p);
      return 1;
  }
  
  /*
   * Compute the inverse of k modulo q.
   * Since q is prime, Fermat's Little Theorem applies, which reduces this to
   * mod-exp operation.  Both the exponent and modulus are public information
   * so a mod-exp that doesn't leak the base is sufficient.  A newly allocated
   * BIGNUM is returned which the caller must free.
   */
  static BIGNUM *dsa_mod_inverse_fermat(const BIGNUM *k, const BIGNUM *q,
                                        BN_CTX *ctx)
  {
      BIGNUM *res = NULL;
      BIGNUM *r, *e;
  
      if ((r = BN_new()) == NULL)
          return NULL;
  
      BN_CTX_start(ctx);
      if ((e = BN_CTX_get(ctx)) != NULL
              && BN_set_word(r, 2)
              && BN_sub(e, q, r)
              && BN_mod_exp_mont(r, k, e, q, ctx, NULL))
          res = r;
      else
          BN_free(r);
      BN_CTX_end(ctx);
      return res;
  }
  