+#include <openssl/sha.h>
+#include "dsa_local.h"
+
+int DSA_generate_parameters_ex(DSA *ret, int bits,
+ const unsigned char *seed_in, int seed_len,
+ int *counter_ret, unsigned long *h_ret,
+ BN_GENCB *cb)
+{
+ if (ret->meth->dsa_paramgen)
+ return ret->meth->dsa_paramgen(ret, bits, seed_in, seed_len,
+ counter_ret, h_ret, cb);
+ else {
+ const EVP_MD *evpmd = bits >= 2048 ? EVP_sha256() : EVP_sha1();
+ size_t qbits = EVP_MD_size(evpmd) * 8;
+
+ return dsa_builtin_paramgen(ret, bits, qbits, evpmd,
+ seed_in, seed_len, NULL, counter_ret,
+ h_ret, cb);
+ }
+}
+
+int dsa_builtin_paramgen(DSA *ret, size_t bits, size_t qbits,
+ const EVP_MD *evpmd, const unsigned char *seed_in,
+ size_t seed_len, unsigned char *seed_out,
+ 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 i, k, n = 0, m = 0, qsize = qbits >> 3;
+ int counter = 0;
+ int r = 0;
+ BN_CTX *ctx = NULL;
+ unsigned int h = 2;
+
+ if (qsize != SHA_DIGEST_LENGTH && qsize != SHA224_DIGEST_LENGTH &&
+ qsize != SHA256_DIGEST_LENGTH)
+ /* invalid q size */
+ return 0;
+
+ if (evpmd == NULL) {
+ if (qsize == SHA_DIGEST_LENGTH)
+ evpmd = EVP_sha1();
+ else if (qsize == SHA224_DIGEST_LENGTH)
+ evpmd = EVP_sha224();
+ else
+ evpmd = EVP_sha256();
+ } else {
+ 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) {
+ DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN, DSA_R_SEED_LEN_SMALL);
+ return 0;
+ }
+ if (seed_len > (size_t)qsize) {
+ /* Only consume as much seed as is expected. */
+ seed_len = qsize;
+ }
+ memcpy(seed, seed_in, seed_len);
+ }
+
+ if ((mont = BN_MONT_CTX_new()) == NULL)
+ goto err;
+
+ if ((ctx = BN_CTX_new()) == 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)
+ goto err;
+
+ if (!BN_lshift(test, BN_value_one(), bits - 1))
+ goto err;
+
+ for (;;) {
+ for (;;) { /* find q */
+ int use_random_seed = (seed_in == NULL);
+
+ /* step 1 */
+ if (!BN_GENCB_call(cb, 0, m++))
+ goto err;
+
+ if (use_random_seed) {
+ if (RAND_bytes(seed, qsize) <= 0)
+ goto err;
+ } else {
+ /* If we come back through, use random seed next time. */
+ seed_in = NULL;
+ }
+ memcpy(buf, seed, qsize);
+ memcpy(buf2, seed, qsize);
+ /* precompute "SEED + 1" for step 7: */
+ for (i = qsize - 1; i >= 0; i--) {
+ buf[i]++;
+ if (buf[i] != 0)
+ break;
+ }
+
+ /* step 2 */
+ if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL))
+ goto err;
+ if (!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_check_prime(q, ctx, cb);
+ if (r > 0)
+ break;
+ if (r != 0)
+ goto err;
+
+ /* do a callback call */
+ /* step 5 */
+ }
+
+ if (!BN_GENCB_call(cb, 2, 0))
+ goto err;
+ if (!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 >= 0; 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))
+ goto err;
+ if (!BN_lshift(r0, r0, (qsize << 3) * k))
+ goto err;
+ if (!BN_add(W, W, r0))
+ goto err;
+ }
+
+ /* more of step 8 */
+ if (!BN_mask_bits(W, bits - 1))
+ goto err;
+ if (!BN_copy(X, W))
+ goto err;
+ if (!BN_add(X, X, test))
+ goto err;
+
+ /* step 9 */
+ if (!BN_lshift1(r0, q))
+ goto err;
+ if (!BN_mod(c, X, r0, ctx))
+ goto err;
+ if (!BN_sub(r0, c, BN_value_one()))
+ goto err;
+ if (!BN_sub(p, X, r0))
+ goto err;
+
+ /* step 10 */
+ if (BN_cmp(p, test) >= 0) {
+ /* step 11 */
+ r = BN_check_prime(p, ctx, 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()))
+ goto err;
+ if (!BN_div(r0, NULL, test, q, ctx))
+ goto err;
+
+ if (!BN_set_word(test, h))
+ goto err;
+ if (!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);
+ ret->dirty_cnt++;
+ 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 (seed_out)
+ memcpy(seed_out, seed, qsize);
+ }
+ BN_CTX_end(ctx);
+ BN_CTX_free(ctx);
+ BN_MONT_CTX_free(mont);
+ return ok;
+}
+
+/*
+ * This is a parameter generation algorithm for the DSA2 algorithm as
+ * described in FIPS 186-3.
+ */