ref: 2cdc6577ef8a251bf1740439cf5bfc47050dab41
dir: /third_party/boringssl/src/crypto/dsa/dsa.c/
/* 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/dh.h>
#include <openssl/digest.h>
#include <openssl/engine.h>
#include <openssl/err.h>
#include <openssl/ex_data.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include <openssl/thread.h>
#include "internal.h"
#include "../fipsmodule/bn/internal.h"
#include "../internal.h"
// Primality test according to FIPS PUB 186[-1], Appendix 2.1: 50 rounds of
// Miller-Rabin.
#define DSS_prime_checks 50
static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx_in, BIGNUM **out_kinv,
BIGNUM **out_r);
static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
DSA *DSA_new(void) {
DSA *dsa = OPENSSL_malloc(sizeof(DSA));
if (dsa == NULL) {
OPENSSL_PUT_ERROR(DSA, ERR_R_MALLOC_FAILURE);
return NULL;
}
OPENSSL_memset(dsa, 0, sizeof(DSA));
dsa->references = 1;
CRYPTO_MUTEX_init(&dsa->method_mont_lock);
CRYPTO_new_ex_data(&dsa->ex_data);
return dsa;
}
void DSA_free(DSA *dsa) {
if (dsa == NULL) {
return;
}
if (!CRYPTO_refcount_dec_and_test_zero(&dsa->references)) {
return;
}
CRYPTO_free_ex_data(&g_ex_data_class, dsa, &dsa->ex_data);
BN_clear_free(dsa->p);
BN_clear_free(dsa->q);
BN_clear_free(dsa->g);
BN_clear_free(dsa->pub_key);
BN_clear_free(dsa->priv_key);
BN_MONT_CTX_free(dsa->method_mont_p);
BN_MONT_CTX_free(dsa->method_mont_q);
CRYPTO_MUTEX_cleanup(&dsa->method_mont_lock);
OPENSSL_free(dsa);
}
int DSA_up_ref(DSA *dsa) {
CRYPTO_refcount_inc(&dsa->references);
return 1;
}
const BIGNUM *DSA_get0_pub_key(const DSA *dsa) { return dsa->pub_key; }
const BIGNUM *DSA_get0_priv_key(const DSA *dsa) { return dsa->priv_key; }
const BIGNUM *DSA_get0_p(const DSA *dsa) { return dsa->p; }
const BIGNUM *DSA_get0_q(const DSA *dsa) { return dsa->q; }
const BIGNUM *DSA_get0_g(const DSA *dsa) { return dsa->g; }
void DSA_get0_key(const DSA *dsa, const BIGNUM **out_pub_key,
const BIGNUM **out_priv_key) {
if (out_pub_key != NULL) {
*out_pub_key = dsa->pub_key;
}
if (out_priv_key != NULL) {
*out_priv_key = dsa->priv_key;
}
}
void DSA_get0_pqg(const DSA *dsa, const BIGNUM **out_p, const BIGNUM **out_q,
const BIGNUM **out_g) {
if (out_p != NULL) {
*out_p = dsa->p;
}
if (out_q != NULL) {
*out_q = dsa->q;
}
if (out_g != NULL) {
*out_g = dsa->g;
}
}
int DSA_set0_key(DSA *dsa, BIGNUM *pub_key, BIGNUM *priv_key) {
if (dsa->pub_key == NULL && pub_key == NULL) {
return 0;
}
if (pub_key != NULL) {
BN_free(dsa->pub_key);
dsa->pub_key = pub_key;
}
if (priv_key != NULL) {
BN_free(dsa->priv_key);
dsa->priv_key = priv_key;
}
return 1;
}
int DSA_set0_pqg(DSA *dsa, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
if ((dsa->p == NULL && p == NULL) ||
(dsa->q == NULL && q == NULL) ||
(dsa->g == NULL && g == NULL)) {
return 0;
}
if (p != NULL) {
BN_free(dsa->p);
dsa->p = p;
}
if (q != NULL) {
BN_free(dsa->q);
dsa->q = q;
}
if (g != NULL) {
BN_free(dsa->g);
dsa->g = g;
}
return 1;
}
int DSA_generate_parameters_ex(DSA *dsa, unsigned bits, const uint8_t *seed_in,
size_t seed_len, int *out_counter,
unsigned long *out_h, 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 qsize;
const EVP_MD *evpmd;
evpmd = (bits >= 2048) ? EVP_sha256() : EVP_sha1();
qsize = EVP_MD_size(evpmd);
if (bits < 512) {
bits = 512;
}
bits = (bits + 63) / 64 * 64;
if (seed_in != NULL) {
if (seed_len < (size_t)qsize) {
return 0;
}
if (seed_len > (size_t)qsize) {
// Only consume as much seed as is expected.
seed_len = qsize;
}
OPENSSL_memcpy(seed, seed_in, seed_len);
}
ctx = BN_CTX_new();
if (ctx == 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 (test == NULL || !BN_lshift(test, BN_value_one(), bits - 1)) {
goto err;
}
for (;;) {
// Find q.
for (;;) {
// step 1
if (!BN_GENCB_call(cb, BN_GENCB_GENERATED, m++)) {
goto err;
}
int use_random_seed = (seed_in == NULL);
if (use_random_seed) {
if (!RAND_bytes(seed, qsize)) {
goto err;
}
} else {
// If we come back through, use random seed next time.
seed_in = NULL;
}
OPENSSL_memcpy(buf, seed, qsize);
OPENSSL_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, use_random_seed, 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, BN_GENCB_GENERATED, 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;
}
mont = BN_MONT_CTX_new_for_modulus(p, ctx);
if (mont == NULL ||
!BN_set_word(test, h)) {
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(dsa->p);
BN_free(dsa->q);
BN_free(dsa->g);
dsa->p = BN_dup(p);
dsa->q = BN_dup(q);
dsa->g = BN_dup(g);
if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
ok = 0;
goto err;
}
if (out_counter != NULL) {
*out_counter = counter;
}
if (out_h != NULL) {
*out_h = h;
}
}
if (ctx) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
BN_MONT_CTX_free(mont);
return ok;
}
DSA *DSAparams_dup(const DSA *dsa) {
DSA *ret = DSA_new();
if (ret == NULL) {
return NULL;
}
ret->p = BN_dup(dsa->p);
ret->q = BN_dup(dsa->q);
ret->g = BN_dup(dsa->g);
if (ret->p == NULL || ret->q == NULL || ret->g == NULL) {
DSA_free(ret);
return NULL;
}
return ret;
}
int DSA_generate_key(DSA *dsa) {
int ok = 0;
BN_CTX *ctx = NULL;
BIGNUM *pub_key = NULL, *priv_key = NULL;
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;
}
}
if (!BN_rand_range_ex(priv_key, 1, dsa->q)) {
goto err;
}
pub_key = dsa->pub_key;
if (pub_key == NULL) {
pub_key = BN_new();
if (pub_key == NULL) {
goto err;
}
}
if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p, &dsa->method_mont_lock,
dsa->p, ctx) ||
!BN_mod_exp_mont_consttime(pub_key, dsa->g, priv_key, dsa->p, ctx,
dsa->method_mont_p)) {
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;
}
DSA_SIG *DSA_SIG_new(void) {
DSA_SIG *sig;
sig = OPENSSL_malloc(sizeof(DSA_SIG));
if (!sig) {
return NULL;
}
sig->r = NULL;
sig->s = NULL;
return sig;
}
void DSA_SIG_free(DSA_SIG *sig) {
if (!sig) {
return;
}
BN_free(sig->r);
BN_free(sig->s);
OPENSSL_free(sig);
}
void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **out_r,
const BIGNUM **out_s) {
if (out_r != NULL) {
*out_r = sig->r;
}
if (out_s != NULL) {
*out_s = sig->s;
}
}
int DSA_SIG_set0(DSA_SIG *sig, BIGNUM *r, BIGNUM *s) {
if (r == NULL || s == NULL) {
return 0;
}
BN_free(sig->r);
BN_free(sig->s);
sig->r = r;
sig->s = s;
return 1;
}
// mod_mul_consttime sets |r| to |a| * |b| modulo |mont->N|, treating |a| and
// |b| as secret. This function internally uses Montgomery reduction, but
// neither inputs nor outputs are in Montgomery form.
static int mod_mul_consttime(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
const BN_MONT_CTX *mont, BN_CTX *ctx) {
BN_CTX_start(ctx);
BIGNUM *tmp = BN_CTX_get(ctx);
// |BN_mod_mul_montgomery| removes a factor of R, so we cancel it with a
// single |BN_to_montgomery| which adds one factor of R.
int ok = tmp != NULL &&
BN_to_montgomery(tmp, a, mont, ctx) &&
BN_mod_mul_montgomery(r, tmp, b, mont, ctx);
BN_CTX_end(ctx);
return ok;
}
DSA_SIG *DSA_do_sign(const uint8_t *digest, size_t digest_len, const DSA *dsa) {
if (!dsa_check_parameters(dsa)) {
return NULL;
}
BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
BIGNUM m;
BIGNUM xr;
BN_CTX *ctx = NULL;
DSA_SIG *ret = NULL;
BN_init(&m);
BN_init(&xr);
s = BN_new();
if (s == NULL) {
goto err;
}
ctx = BN_CTX_new();
if (ctx == NULL) {
goto err;
}
redo:
if (!dsa_sign_setup(dsa, ctx, &kinv, &r)) {
goto err;
}
if (digest_len > BN_num_bytes(dsa->q)) {
// If the digest length is greater than the size of |dsa->q| use the
// BN_num_bits(dsa->q) leftmost bits of the digest, see FIPS 186-3, 4.2.
// Note the above check that |dsa->q| is a multiple of 8 bits.
digest_len = BN_num_bytes(dsa->q);
}
if (BN_bin2bn(digest, digest_len, &m) == NULL) {
goto err;
}
// |m| is bounded by 2^(num_bits(q)), which is slightly looser than q. This
// violates |bn_mod_add_consttime| and |mod_mul_consttime|'s preconditions.
// (The underlying algorithms could accept looser bounds, but we reduce for
// simplicity.)
size_t q_width = bn_minimal_width(dsa->q);
if (!bn_resize_words(&m, q_width) ||
!bn_resize_words(&xr, q_width)) {
goto err;
}
bn_reduce_once_in_place(m.d, 0 /* no carry word */, dsa->q->d,
xr.d /* scratch space */, q_width);
// Compute s = inv(k) (m + xr) mod q. Note |dsa->method_mont_q| is
// initialized by |dsa_sign_setup|.
if (!mod_mul_consttime(&xr, dsa->priv_key, r, dsa->method_mont_q, ctx) ||
!bn_mod_add_consttime(s, &xr, &m, dsa->q, ctx) ||
!mod_mul_consttime(s, s, kinv, dsa->method_mont_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(r) || BN_is_zero(s)) {
goto redo;
}
ret = DSA_SIG_new();
if (ret == NULL) {
goto err;
}
ret->r = r;
ret->s = s;
err:
if (ret == NULL) {
OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
BN_free(r);
BN_free(s);
}
BN_CTX_free(ctx);
BN_clear_free(&m);
BN_clear_free(&xr);
BN_clear_free(kinv);
return ret;
}
int DSA_do_verify(const uint8_t *digest, size_t digest_len, DSA_SIG *sig,
const DSA *dsa) {
int valid;
if (!DSA_do_check_signature(&valid, digest, digest_len, sig, dsa)) {
return -1;
}
return valid;
}
int DSA_do_check_signature(int *out_valid, const uint8_t *digest,
size_t digest_len, DSA_SIG *sig, const DSA *dsa) {
*out_valid = 0;
if (!dsa_check_parameters(dsa)) {
return 0;
}
int ret = 0;
BIGNUM u1, u2, t1;
BN_init(&u1);
BN_init(&u2);
BN_init(&t1);
BN_CTX *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
unsigned q_bits = BN_num_bits(dsa->q);
if (digest_len > (q_bits >> 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 = (q_bits >> 3);
}
if (BN_bin2bn(digest, 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;
}
if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
(CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
ctx)) {
goto err;
}
if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx,
dsa->method_mont_p)) {
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;
}
int DSA_sign(int type, const uint8_t *digest, size_t digest_len,
uint8_t *out_sig, unsigned int *out_siglen, const DSA *dsa) {
DSA_SIG *s;
s = DSA_do_sign(digest, digest_len, dsa);
if (s == NULL) {
*out_siglen = 0;
return 0;
}
*out_siglen = i2d_DSA_SIG(s, &out_sig);
DSA_SIG_free(s);
return 1;
}
int DSA_verify(int type, const uint8_t *digest, size_t digest_len,
const uint8_t *sig, size_t sig_len, const DSA *dsa) {
int valid;
if (!DSA_check_signature(&valid, digest, digest_len, sig, sig_len, dsa)) {
return -1;
}
return valid;
}
int DSA_check_signature(int *out_valid, const uint8_t *digest,
size_t digest_len, const uint8_t *sig, size_t sig_len,
const DSA *dsa) {
DSA_SIG *s = NULL;
int ret = 0;
uint8_t *der = NULL;
s = DSA_SIG_new();
if (s == NULL) {
goto err;
}
const uint8_t *sigp = sig;
if (d2i_DSA_SIG(&s, &sigp, sig_len) == NULL || sigp != sig + sig_len) {
goto err;
}
// Ensure that the signature uses DER and doesn't have trailing garbage.
int der_len = i2d_DSA_SIG(s, &der);
if (der_len < 0 || (size_t)der_len != sig_len ||
OPENSSL_memcmp(sig, der, sig_len)) {
goto err;
}
ret = DSA_do_check_signature(out_valid, digest, digest_len, s, dsa);
err:
OPENSSL_free(der);
DSA_SIG_free(s);
return ret;
}
// der_len_len returns the number of bytes needed to represent a length of |len|
// in DER.
static size_t der_len_len(size_t len) {
if (len < 0x80) {
return 1;
}
size_t ret = 1;
while (len > 0) {
ret++;
len >>= 8;
}
return ret;
}
int DSA_size(const DSA *dsa) {
size_t order_len = BN_num_bytes(dsa->q);
// Compute the maximum length of an |order_len| byte integer. Defensively
// assume that the leading 0x00 is included.
size_t integer_len = 1 /* tag */ + der_len_len(order_len + 1) + 1 + order_len;
if (integer_len < order_len) {
return 0;
}
// A DSA signature is two INTEGERs.
size_t value_len = 2 * integer_len;
if (value_len < integer_len) {
return 0;
}
// Add the header.
size_t ret = 1 /* tag */ + der_len_len(value_len) + value_len;
if (ret < value_len) {
return 0;
}
return ret;
}
static int dsa_sign_setup(const DSA *dsa, BN_CTX *ctx, BIGNUM **out_kinv,
BIGNUM **out_r) {
if (!dsa->p || !dsa->q || !dsa->g) {
OPENSSL_PUT_ERROR(DSA, DSA_R_MISSING_PARAMETERS);
return 0;
}
int ret = 0;
BIGNUM k;
BN_init(&k);
BIGNUM *r = BN_new();
BIGNUM *kinv = BN_new();
if (r == NULL || kinv == NULL ||
// Get random k
!BN_rand_range_ex(&k, 1, dsa->q) ||
!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
(CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->p,
ctx) ||
!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_q,
(CRYPTO_MUTEX *)&dsa->method_mont_lock, dsa->q,
ctx) ||
// Compute r = (g^k mod p) mod q
!BN_mod_exp_mont_consttime(r, dsa->g, &k, dsa->p, ctx,
dsa->method_mont_p) ||
// Note |BN_mod| below is not constant-time and may leak information about
// |r|. |dsa->p| may be significantly larger than |dsa->q|, so this is not
// easily performed in constant-time with Montgomery reduction.
//
// However, |r| at this point is g^k (mod p). It is almost the value of
// |r| revealed in the signature anyway (g^k (mod p) (mod q)), going from
// it to |k| would require computing a discrete log.
!BN_mod(r, r, dsa->q, ctx) ||
// Compute part of 's = inv(k) (m + xr) mod q' using Fermat's Little
// Theorem.
!bn_mod_inverse_prime(kinv, &k, dsa->q, ctx, dsa->method_mont_q)) {
OPENSSL_PUT_ERROR(DSA, ERR_R_BN_LIB);
goto err;
}
BN_clear_free(*out_kinv);
*out_kinv = kinv;
kinv = NULL;
BN_clear_free(*out_r);
*out_r = r;
r = NULL;
ret = 1;
err:
BN_clear_free(&k);
BN_clear_free(r);
BN_clear_free(kinv);
return ret;
}
int DSA_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) {
int index;
if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp,
free_func)) {
return -1;
}
return index;
}
int DSA_set_ex_data(DSA *dsa, int idx, void *arg) {
return CRYPTO_set_ex_data(&dsa->ex_data, idx, arg);
}
void *DSA_get_ex_data(const DSA *dsa, int idx) {
return CRYPTO_get_ex_data(&dsa->ex_data, idx);
}
DH *DSA_dup_DH(const DSA *dsa) {
if (dsa == NULL) {
return NULL;
}
DH *ret = DH_new();
if (ret == NULL) {
goto err;
}
if (dsa->q != NULL) {
ret->priv_length = BN_num_bits(dsa->q);
if ((ret->q = BN_dup(dsa->q)) == NULL) {
goto err;
}
}
if ((dsa->p != NULL && (ret->p = BN_dup(dsa->p)) == NULL) ||
(dsa->g != NULL && (ret->g = BN_dup(dsa->g)) == NULL) ||
(dsa->pub_key != NULL && (ret->pub_key = BN_dup(dsa->pub_key)) == NULL) ||
(dsa->priv_key != NULL &&
(ret->priv_key = BN_dup(dsa->priv_key)) == NULL)) {
goto err;
}
return ret;
err:
DH_free(ret);
return NULL;
}