/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] * * The DSS routines are based on patches supplied by * Steven Schoch . */ #include #include #include #include #include #include #include #include #include "internal.h" #define OPENSSL_DSA_MAX_MODULUS_BITS 10000 /* Primality test according to FIPS PUB 186[-1], Appendix 2.1: 50 rounds of * Rabin-Miller */ #define DSS_prime_checks 50 static int sign_setup(const DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp, const uint8_t *digest, size_t digest_len) { BN_CTX *ctx; BIGNUM k, kq, *K, *kinv = NULL, *r = NULL; int ret = 0; if (!dsa->p || !dsa->q || !dsa->g) { OPENSSL_PUT_ERROR(DSA, sign_setup, DSA_R_MISSING_PARAMETERS); return 0; } BN_init(&k); BN_init(&kq); ctx = ctx_in; if (ctx == NULL) { ctx = BN_CTX_new(); if (ctx == NULL) { goto err; } } r = BN_new(); if (r == NULL) { goto err; } /* Get random k */ do { /* If possible, we'll include the private key and message digest in the k * generation. The |digest| argument is only empty if |DSA_sign_setup| is * being used. */ int ok; if (digest_len > 0) { ok = BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, digest, digest_len, ctx); } else { ok = BN_rand_range(&k, dsa->q); } if (!ok) { goto err; } } while (BN_is_zero(&k)); BN_set_flags(&k, BN_FLG_CONSTTIME); if (BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p, (CRYPTO_MUTEX *)&dsa->method_mont_p_lock, dsa->p, ctx) == NULL) { goto err; } /* Compute r = (g^k mod p) mod q */ if (!BN_copy(&kq, &k)) { goto err; } /* We do not want timing information to leak the length of k, * so we compute g^k using an equivalent exponent of fixed length. * * (This is a kludge that we need because the BN_mod_exp_mont() * does not let us specify the desired timing behaviour.) */ if (!BN_add(&kq, &kq, dsa->q)) { goto err; } if (BN_num_bits(&kq) <= BN_num_bits(dsa->q) && !BN_add(&kq, &kq, dsa->q)) { goto err; } K = &kq; 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' */ kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx); if (kinv == NULL) { goto err; } BN_clear_free(*kinvp); *kinvp = kinv; kinv = NULL; BN_clear_free(*rp); *rp = r; ret = 1; err: if (!ret) { OPENSSL_PUT_ERROR(DSA, sign_setup, ERR_R_BN_LIB); if (r != NULL) { BN_clear_free(r); } } if (ctx_in == NULL) { BN_CTX_free(ctx); } BN_clear_free(&k); BN_clear_free(&kq); return ret; } static DSA_SIG *sign(const uint8_t *digest, size_t digest_len, DSA *dsa) { BIGNUM *kinv = NULL, *r = NULL, *s = NULL; BIGNUM m; BIGNUM xr; BN_CTX *ctx = NULL; int reason = ERR_R_BN_LIB; DSA_SIG *ret = NULL; int noredo = 0; BN_init(&m); BN_init(&xr); if (!dsa->p || !dsa->q || !dsa->g) { reason = DSA_R_MISSING_PARAMETERS; goto err; } s = BN_new(); if (s == NULL) { goto err; } ctx = BN_CTX_new(); if (ctx == NULL) { goto err; } redo: if (dsa->kinv == NULL || dsa->r == NULL) { if (!DSA_sign_setup(dsa, ctx, &kinv, &r)) { goto err; } } else { kinv = dsa->kinv; dsa->kinv = NULL; r = dsa->r; dsa->r = NULL; noredo = 1; } if (digest_len > 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 */ digest_len = BN_num_bytes(dsa->q); } if (BN_bin2bn(digest, digest_len, &m) == NULL) { goto err; } /* Compute s = inv(k) (m + xr) mod q */ if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) { goto err; /* s = xr */ } if (!BN_add(s, &xr, &m)) { goto err; /* s = m + xr */ } if (BN_cmp(s, dsa->q) > 0) { if (!BN_sub(s, s, dsa->q)) { goto err; } } if (!BN_mod_mul(s, s, kinv, dsa->q, ctx)) { goto err; } ret = DSA_SIG_new(); if (ret == NULL) { goto err; } /* Redo if r or s is zero as required by FIPS 186-3: this is * very unlikely. */ if (BN_is_zero(r) || BN_is_zero(s)) { if (noredo) { reason = DSA_R_NEED_NEW_SETUP_VALUES; goto err; } goto redo; } ret->r = r; ret->s = s; err: if (!ret) { OPENSSL_PUT_ERROR(DSA, sign, reason); BN_free(r); BN_free(s); } BN_CTX_free(ctx); BN_clear_free(&m); BN_clear_free(&xr); BN_clear_free(kinv); return ret; } static int verify(int *out_valid, const uint8_t *dgst, size_t digest_len, DSA_SIG *sig, const DSA *dsa) { BN_CTX *ctx; BIGNUM u1, u2, t1; BN_MONT_CTX *mont = NULL; int ret = 0; unsigned i; *out_valid = 0; if (!dsa->p || !dsa->q || !dsa->g) { OPENSSL_PUT_ERROR(DSA, verify, DSA_R_MISSING_PARAMETERS); return 0; } i = BN_num_bits(dsa->q); /* fips 186-3 allows only different sizes for q */ if (i != 160 && i != 224 && i != 256) { OPENSSL_PUT_ERROR(DSA, verify, DSA_R_BAD_Q_VALUE); return 0; } if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) { OPENSSL_PUT_ERROR(DSA, verify, DSA_R_MODULUS_TOO_LARGE); return 0; } BN_init(&u1); BN_init(&u2); BN_init(&t1); ctx = BN_CTX_new(); if (ctx == NULL) { goto err; } if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || BN_ucmp(sig->r, dsa->q) >= 0) { ret = 1; goto err; } if (BN_is_zero(sig->s) || BN_is_negative(sig->s) || BN_ucmp(sig->s, dsa->q) >= 0) { ret = 1; goto err; } /* Calculate W = inv(S) mod Q * save W in u2 */ if (BN_mod_inverse(&u2, sig->s, dsa->q, ctx) == NULL) { goto err; } /* save M in u1 */ if (digest_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 */ digest_len = (i >> 3); } if (BN_bin2bn(dgst, digest_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, sig->r, &u2, dsa->q, ctx)) { goto err; } mont = BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p, (CRYPTO_MUTEX *)&dsa->method_mont_p_lock, dsa->p, ctx); if (!mont) { goto err; } if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont)) { goto err; } /* BN_copy(&u1,&t1); */ /* 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. */ *out_valid = BN_ucmp(&u1, sig->r) == 0; ret = 1; err: if (ret != 1) { OPENSSL_PUT_ERROR(DSA, verify, ERR_R_BN_LIB); } BN_CTX_free(ctx); BN_free(&u1); BN_free(&u2); BN_free(&t1); return ret; } static int keygen(DSA *dsa) { int ok = 0; BN_CTX *ctx = NULL; BIGNUM *pub_key = NULL, *priv_key = NULL; BIGNUM prk; ctx = BN_CTX_new(); if (ctx == NULL) { goto err; } priv_key = dsa->priv_key; if (priv_key == NULL) { priv_key = BN_new(); if (priv_key == NULL) { goto err; } } do { if (!BN_rand_range(priv_key, dsa->q)) { goto err; } } while (BN_is_zero(priv_key)); pub_key = dsa->pub_key; if (pub_key == NULL) { pub_key = BN_new(); if (pub_key == NULL) { goto err; } } BN_init(&prk); BN_with_flags(&prk, priv_key, BN_FLG_CONSTTIME); if (!BN_mod_exp(pub_key, dsa->g, &prk, dsa->p, ctx)) { goto err; } dsa->priv_key = priv_key; dsa->pub_key = pub_key; ok = 1; err: if (dsa->pub_key == NULL) { BN_free(pub_key); } if (dsa->priv_key == NULL) { BN_free(priv_key); } BN_CTX_free(ctx); return ok; } static int paramgen(DSA *ret, unsigned bits, const uint8_t *seed_in, size_t seed_len, int *counter_ret, unsigned long *h_ret, BN_GENCB *cb) { int ok = 0; unsigned char seed[SHA256_DIGEST_LENGTH]; unsigned char md[SHA256_DIGEST_LENGTH]; unsigned char buf[SHA256_DIGEST_LENGTH], buf2[SHA256_DIGEST_LENGTH]; BIGNUM *r0, *W, *X, *c, *test; BIGNUM *g = NULL, *q = NULL, *p = NULL; BN_MONT_CTX *mont = NULL; int k, n = 0, m = 0; unsigned i; int counter = 0; int r = 0; BN_CTX *ctx = NULL; unsigned int h = 2; unsigned qbits, qsize; const EVP_MD *evpmd; if (bits >= 2048) { qbits = 256; evpmd = EVP_sha256(); } else { qbits = 160; evpmd = EVP_sha1(); } qsize = qbits / 8; if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH && qsize != SHA256_DIGEST_LENGTH) { /* invalid q size */ return 0; } if (bits < 512) { bits = 512; } bits = (bits + 63) / 64 * 64; /* NB: seed_len == 0 is special case: copy generated seed to * seed_in if it is not NULL. */ if (seed_len && (seed_len < (size_t)qsize)) { seed_in = NULL; /* seed buffer too small -- ignore */ } if (seed_len > (size_t)qsize) { seed_len = qsize; /* App. 2.2 of FIPS PUB 186 allows larger SEED, * but our internal buffers are restricted to 160 bits*/ } if (seed_in != NULL) { memcpy(seed, seed_in, seed_len); } ctx = BN_CTX_new(); mont = BN_MONT_CTX_new(); if (ctx == NULL || mont == NULL) { goto err; } BN_CTX_start(ctx); r0 = BN_CTX_get(ctx); g = BN_CTX_get(ctx); W = BN_CTX_get(ctx); q = BN_CTX_get(ctx); X = BN_CTX_get(ctx); c = BN_CTX_get(ctx); p = BN_CTX_get(ctx); test = BN_CTX_get(ctx); if (!BN_lshift(test, BN_value_one(), bits - 1)) { goto err; } for (;;) { /* Find q. */ for (;;) { int seed_is_random; /* step 1 */ if (!BN_GENCB_call(cb, 0, m++)) { goto err; } if (!seed_len) { if (!RAND_bytes(seed, qsize)) { goto err; } seed_is_random = 1; } else { seed_is_random = 0; seed_len = 0; /* use random seed if 'seed_in' turns out to be bad*/ } memcpy(buf, seed, qsize); memcpy(buf2, seed, qsize); /* precompute "SEED + 1" for step 7: */ for (i = qsize - 1; i < qsize; i--) { buf[i]++; if (buf[i] != 0) { break; } } /* step 2 */ if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL) || !EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL)) { goto err; } for (i = 0; i < qsize; i++) { md[i] ^= buf2[i]; } /* step 3 */ md[0] |= 0x80; md[qsize - 1] |= 0x01; if (!BN_bin2bn(md, qsize, q)) { goto err; } /* step 4 */ r = BN_is_prime_fasttest_ex(q, DSS_prime_checks, ctx, seed_is_random, cb); if (r > 0) { break; } if (r != 0) { goto err; } /* do a callback call */ /* step 5 */ } if (!BN_GENCB_call(cb, 2, 0) || !BN_GENCB_call(cb, 3, 0)) { goto err; } /* step 6 */ counter = 0; /* "offset = 2" */ n = (bits - 1) / 160; for (;;) { if ((counter != 0) && !BN_GENCB_call(cb, 0, counter)) { goto err; } /* step 7 */ BN_zero(W); /* now 'buf' contains "SEED + offset - 1" */ for (k = 0; k <= n; k++) { /* obtain "SEED + offset + k" by incrementing: */ for (i = qsize - 1; i < qsize; i--) { buf[i]++; if (buf[i] != 0) { break; } } if (!EVP_Digest(buf, qsize, md, NULL, evpmd, NULL)) { goto err; } /* step 8 */ if (!BN_bin2bn(md, qsize, r0) || !BN_lshift(r0, r0, (qsize << 3) * k) || !BN_add(W, W, r0)) { goto err; } } /* more of step 8 */ if (!BN_mask_bits(W, bits - 1) || !BN_copy(X, W) || !BN_add(X, X, test)) { goto err; } /* step 9 */ if (!BN_lshift1(r0, q) || !BN_mod(c, X, r0, ctx) || !BN_sub(r0, c, BN_value_one()) || !BN_sub(p, X, r0)) { goto err; } /* step 10 */ if (BN_cmp(p, test) >= 0) { /* step 11 */ r = BN_is_prime_fasttest_ex(p, DSS_prime_checks, ctx, 1, cb); if (r > 0) { goto end; /* found it */ } if (r != 0) { goto err; } } /* step 13 */ counter++; /* "offset = offset + n + 1" */ /* step 14 */ if (counter >= 4096) { break; } } } end: if (!BN_GENCB_call(cb, 2, 1)) { goto err; } /* We now need to generate g */ /* Set r0=(p-1)/q */ if (!BN_sub(test, p, BN_value_one()) || !BN_div(r0, NULL, test, q, ctx)) { goto err; } if (!BN_set_word(test, h) || !BN_MONT_CTX_set(mont, p, ctx)) { goto err; } for (;;) { /* g=test^r0%p */ if (!BN_mod_exp_mont(g, test, r0, p, ctx, mont)) { goto err; } if (!BN_is_one(g)) { break; } if (!BN_add(test, test, BN_value_one())) { goto err; } h++; } if (!BN_GENCB_call(cb, 3, 1)) { goto err; } ok = 1; err: if (ok) { BN_free(ret->p); BN_free(ret->q); BN_free(ret->g); ret->p = BN_dup(p); ret->q = BN_dup(q); ret->g = BN_dup(g); if (ret->p == NULL || ret->q == NULL || ret->g == NULL) { ok = 0; goto err; } if (counter_ret != NULL) { *counter_ret = counter; } if (h_ret != NULL) { *h_ret = h; } } if (ctx) { BN_CTX_end(ctx); BN_CTX_free(ctx); } BN_MONT_CTX_free(mont); return ok; } static int finish(DSA *dsa) { BN_MONT_CTX_free(dsa->method_mont_p); dsa->method_mont_p = NULL; return 1; } const struct dsa_method DSA_default_method = { { 0 /* references */, 1 /* is_static */, }, NULL /* app_data */, NULL /* init */, finish /* finish */, sign, sign_setup, verify, paramgen, keygen, };