#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
+#include <openssl/sha.h>
#include <openssl/dsa.h>
#include <openssl/rand.h>
#include <openssl/asn1.h>
-#ifndef OPENSSL_NO_ENGINE
-#include <openssl/engine.h>
-#endif
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
- DSA *dsa);
+ DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
BIGNUM m;
BIGNUM xr;
BN_CTX *ctx=NULL;
- int i,reason=ERR_R_BN_LIB;
+ int reason=ERR_R_BN_LIB;
DSA_SIG *ret=NULL;
BN_init(&m);
s=BN_new();
if (s == NULL) goto err;
- i=BN_num_bytes(dsa->q); /* should be 20 */
- if ((dlen > i) || (dlen > 50))
+ /* reject a excessive digest length (currently at most
+ * dsa-with-SHA256 is supported) */
+ if (dlen > SHA256_DIGEST_LENGTH)
{
reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
goto err;
dsa->r=NULL;
}
- if (BN_bin2bn(dgst,dlen,&m) == NULL) 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,r,dsa->q,ctx)) goto err;/* s = xr */
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
{
BN_CTX *ctx;
- BIGNUM k,*kinv=NULL,*r=NULL;
+ BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
int ret=0;
if (!dsa->p || !dsa->q || !dsa->g)
}
BN_init(&k);
+ BN_init(&kq);
if (ctx_in == NULL)
{
ctx=ctx_in;
if ((r=BN_new()) == NULL) goto err;
- kinv=NULL;
/* Get random k */
do
if (!BN_rand_range(&k, dsa->q)) goto err;
while (BN_is_zero(&k));
+ if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
+ {
+ BN_set_flags(&k, BN_FLG_EXP_CONSTTIME);
+ }
- if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
+ if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
{
- if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
- if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
- dsa->p,ctx)) goto err;
+ if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
+ CRYPTO_LOCK_DSA,
+ dsa->p, ctx))
+ goto err;
}
/* Compute r = (g^k mod p) mod q */
- DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
- (BN_MONT_CTX *)dsa->method_mont_p);
+
+ if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
+ {
+ 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))
+ {
+ if (!BN_add(&kq, &kq, dsa->q)) goto err;
+ }
+
+ K = &kq;
+ }
+ else
+ {
+ K = &k;
+ }
+ DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
+ dsa->method_mont_p);
if (!BN_mod(r,r,dsa->q,ctx)) goto err;
/* Compute part of 's = inv(k) (m + xr) mod q' */
if (!ret)
{
DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
- if (kinv != NULL) BN_clear_free(kinv);
- if (r != NULL) BN_clear_free(r);
+ if (r != NULL)
+ BN_clear_free(r);
}
if (ctx_in == NULL) BN_CTX_free(ctx);
- if (kinv != NULL) BN_clear_free(kinv);
BN_clear_free(&k);
+ BN_clear_free(&kq);
return(ret);
}
static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
- DSA *dsa)
+ DSA *dsa)
{
BN_CTX *ctx;
BIGNUM u1,u2,t1;
BN_MONT_CTX *mont=NULL;
- int ret = -1;
+ 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;
+ }
+
+ /* reject a excessive digest length (currently at most
+ * dsa-with-SHA256 is supported) */
+ if (dgst_len > SHA256_DIGEST_LENGTH)
+ {
+ DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+ return -1;
+ }
+
BN_init(&u1);
BN_init(&u2);
BN_init(&t1);
if ((ctx=BN_CTX_new()) == NULL) goto err;
- if (BN_is_zero(sig->r) || BN_get_sign(sig->r) ||
+ if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
BN_ucmp(sig->r, dsa->q) >= 0)
{
ret = 0;
goto err;
}
- if (BN_is_zero(sig->s) || BN_get_sign(sig->s) ||
+ if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
BN_ucmp(sig->s, dsa->q) >= 0)
{
ret = 0;
if ((BN_mod_inverse(&u2,sig->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 */
/* u2 = r * w mod q */
if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
- if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
+
+ if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
{
- if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
- if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
- dsa->p,ctx)) goto err;
+ mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
+ CRYPTO_LOCK_DSA, dsa->p, ctx);
+ if (!mont)
+ goto err;
}
- mont=(BN_MONT_CTX *)dsa->method_mont_p;
DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
ret=(BN_ucmp(&u1, sig->r) == 0);
err:
+ /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
+ there is no error in BN. Test should be ret == -1 (Ben) */
if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
if (ctx != NULL) BN_CTX_free(ctx);
BN_free(&u1);
static int dsa_finish(DSA *dsa)
{
if(dsa->method_mont_p)
- BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p);
+ BN_MONT_CTX_free(dsa->method_mont_p);
return(1);
}
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