| /* |
| * Copyright 1995-2016 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/bn.h> |
| #include <openssl/sha.h> |
| #include "dsa_locl.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 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; |
| |
| void DSA_set_default_method(const DSA_METHOD *meth) |
| { |
| default_DSA_method = meth; |
| } |
| |
| const DSA_METHOD *DSA_get_default_method(void) |
| { |
| return default_DSA_method; |
| } |
| |
| const DSA_METHOD *DSA_OpenSSL(void) |
| { |
| return &openssl_dsa_meth; |
| } |
| |
| static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) |
| { |
| BIGNUM *kinv = NULL; |
| BIGNUM *m; |
| BIGNUM *xr; |
| BN_CTX *ctx = NULL; |
| int reason = ERR_R_BN_LIB; |
| DSA_SIG *ret = NULL; |
| int rv = 0; |
| |
| m = BN_new(); |
| xr = BN_new(); |
| if (m == NULL || xr == NULL) |
| goto err; |
| |
| if (!dsa->p || !dsa->q || !dsa->g) { |
| reason = DSA_R_MISSING_PARAMETERS; |
| 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(); |
| if (ctx == NULL) |
| goto err; |
| redo: |
| if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen)) |
| goto err; |
| |
| if (dlen > BN_num_bytes(dsa->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->q); |
| if (BN_bin2bn(dgst, dlen, m) == NULL) |
| goto err; |
| |
| /* Compute s = inv(k) (m + xr) mod q */ |
| if (!BN_mod_mul(xr, dsa->priv_key, ret->r, dsa->q, ctx)) |
| goto err; /* s = xr */ |
| if (!BN_add(ret->s, xr, m)) |
| goto err; /* s = m + xr */ |
| if (BN_cmp(ret->s, dsa->q) > 0) |
| if (!BN_sub(ret->s, ret->s, dsa->q)) |
| goto err; |
| if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->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) { |
| DSAerr(DSA_F_DSA_DO_SIGN, reason); |
| DSA_SIG_free(ret); |
| ret = NULL; |
| } |
| BN_CTX_free(ctx); |
| BN_clear_free(m); |
| BN_clear_free(xr); |
| BN_clear_free(kinv); |
| return ret; |
| } |
| |
| 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, *m; |
| int ret = 0; |
| int q_bits; |
| |
| if (!dsa->p || !dsa->q || !dsa->g) { |
| DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS); |
| return 0; |
| } |
| |
| k = BN_new(); |
| l = BN_new(); |
| m = BN_new(); |
| if (k == NULL || l == NULL || m == NULL) |
| goto err; |
| |
| if (ctx_in == NULL) { |
| if ((ctx = BN_CTX_new()) == NULL) |
| goto err; |
| } else |
| ctx = ctx_in; |
| |
| /* Preallocate space */ |
| q_bits = BN_num_bits(dsa->q); |
| if (!BN_set_bit(k, q_bits) |
| || !BN_set_bit(l, q_bits) |
| || !BN_set_bit(m, q_bits)) |
| 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->q, dsa->priv_key, dgst, |
| dlen, ctx)) |
| goto err; |
| } else if (!BN_priv_rand_range(k, dsa->q)) |
| goto err; |
| } while (BN_is_zero(k)); |
| |
| BN_set_flags(k, BN_FLG_CONSTTIME); |
| |
| if (dsa->flags & DSA_FLAG_CACHE_MONT_P) { |
| if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, |
| dsa->lock, dsa->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. |
| * |
| * TODO: revisit the BN_copy aiming for a memory access agnostic |
| * conditional copy. |
| */ |
| if (!BN_add(l, k, dsa->q) |
| || !BN_add(m, l, dsa->q) |
| || !BN_copy(k, BN_num_bits(l) > q_bits ? l : m)) |
| goto err; |
| |
| if ((dsa)->meth->bn_mod_exp != NULL) { |
| if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, k, dsa->p, ctx, |
| dsa->method_mont_p)) |
| goto err; |
| } else { |
| if (!BN_mod_exp_mont(r, dsa->g, k, dsa->p, ctx, dsa->method_mont_p)) |
| goto err; |
| } |
| |
| if (!BN_mod(r, r, dsa->q, ctx)) |
| goto err; |
| |
| /* Compute part of 's = inv(k) (m + xr) mod q' */ |
| if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL) |
| goto err; |
| |
| BN_clear_free(*kinvp); |
| *kinvp = kinv; |
| kinv = NULL; |
| ret = 1; |
| err: |
| if (!ret) |
| DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB); |
| if (ctx != ctx_in) |
| BN_CTX_free(ctx); |
| BN_clear_free(k); |
| BN_clear_free(l); |
| BN_clear_free(m); |
| 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->p || !dsa->q || !dsa->g) { |
| DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS); |
| return -1; |
| } |
| |
| i = BN_num_bits(dsa->q); |
| /* fips 186-3 allows only different sizes for q */ |
| if (i != 160 && i != 224 && i != 256) { |
| DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE); |
| return -1; |
| } |
| |
| if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) { |
| DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE); |
| return -1; |
| } |
| u1 = BN_new(); |
| u2 = BN_new(); |
| t1 = BN_new(); |
| ctx = BN_CTX_new(); |
| 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->q) >= 0) { |
| ret = 0; |
| goto err; |
| } |
| if (BN_is_zero(s) || BN_is_negative(s) || |
| BN_ucmp(s, dsa->q) >= 0) { |
| ret = 0; |
| goto err; |
| } |
| |
| /* |
| * Calculate W = inv(S) mod Q save W in u2 |
| */ |
| if ((BN_mod_inverse(u2, s, dsa->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->q, ctx)) |
| goto err; |
| |
| /* u2 = r * w mod q */ |
| if (!BN_mod_mul(u2, r, u2, dsa->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->p, ctx); |
| if (!mont) |
| goto err; |
| } |
| |
| if (dsa->meth->dsa_mod_exp != NULL) { |
| if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->g, u1, dsa->pub_key, u2, |
| dsa->p, ctx, mont)) |
| goto err; |
| } else { |
| if (!BN_mod_exp2_mont(t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx, |
| mont)) |
| goto err; |
| } |
| |
| /* let u1 = u1 mod q */ |
| if (!BN_mod(u1, t1, dsa->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) |
| DSAerr(DSA_F_DSA_DO_VERIFY, 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; |
| return 1; |
| } |
| |
| static int dsa_finish(DSA *dsa) |
| { |
| BN_MONT_CTX_free(dsa->method_mont_p); |
| return 1; |
| } |
