blob: e4984b4f17e7ef9d77e51fc66ecf05adbe791045 [file] [log] [blame]
/* 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 <schoch@sheba.arc.nasa.gov>. */
#include <openssl/dsa.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/digest.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include <openssl/thread.h>
#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, 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, 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, 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, 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, DSA_R_BAD_Q_VALUE);
return 0;
}
if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
OPENSSL_PUT_ERROR(DSA, 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, 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();
if (ctx == NULL) {
goto err;
}
BN_CTX_start(ctx);
mont = BN_MONT_CTX_new();
if (mont == NULL) {
goto err;
}
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 (test == NULL || !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,
};