Add secure DSA nonce flag.
[openssl.git] / crypto / dsa / dsa_ossl.c
index dc5d4b3..d1f8060 100644 (file)
@@ -58,6 +58,8 @@
 
 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
 
+#define OPENSSL_FIPSAPI
+
 #include <stdio.h>
 #include "cryptlib.h"
 #include <openssl/bn.h>
 #include <openssl/dsa.h>
 #include <openssl/rand.h>
 #include <openssl/asn1.h>
+#ifdef OPENSSL_FIPS
+#include <openssl/fips.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_sign_setup(DSA *dsa, BN_CTX *ctx_in,
+                         BIGNUM **kinvp, BIGNUM **rp,
+                         const unsigned char *dgst, int dlen);
 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
                         DSA *dsa);
 static int dsa_init(DSA *dsa);
@@ -82,7 +89,7 @@ NULL, /* dsa_mod_exp, */
 NULL, /* dsa_bn_mod_exp, */
 dsa_init,
 dsa_finish,
-0,
+DSA_FLAG_FIPS_METHOD,
 NULL,
 NULL,
 NULL
@@ -134,8 +141,26 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, 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;
+       int noredo = 0;
+
+#ifdef OPENSSL_FIPS
+       if(FIPS_selftest_failed())
+           {
+           FIPSerr(FIPS_F_DSA_DO_SIGN,FIPS_R_FIPS_SELFTEST_FAILED);
+           return NULL;
+           }
+
+       if (FIPS_module_mode() && !(dsa->flags & DSA_FLAG_NON_FIPS_ALLOW) 
+               && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
+               {
+               DSAerr(DSA_F_DSA_DO_SIGN, DSA_R_KEY_SIZE_TOO_SMALL);
+               return NULL;
+               }
+       if (!fips_check_dsa_prng(dsa, 0, 0))
+               goto err;
+#endif
 
        BN_init(&m);
        BN_init(&xr);
@@ -148,21 +173,13 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 
        s=BN_new();
        if (s == NULL) goto err;
-
-       /* 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;
-               }
-
        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;
+               if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen))
+                       goto err;
                }
        else
                {
@@ -170,29 +187,39 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
                dsa->kinv=NULL;
                r=dsa->r;
                dsa->r=NULL;
+               noredo = 1;
                }
 
-       if (BN_bin2bn(dgst,dlen,&m) == NULL)
-               goto err;
-       i = BN_num_bytes(dsa->q);
-       if (dlen > i)
-               {
+       
+       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 */
-               if (!BN_rshift(&m, &m, (dlen - i) << 3))
-                       goto err; 
-               }
+               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 */
        if (!BN_add(s, &xr, &m)) goto err;              /* s = m + xr */
        if (BN_cmp(s,dsa->q) > 0)
-               BN_sub(s,s,dsa->q);
+               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;
        
@@ -211,7 +238,9 @@ err:
        return(ret);
        }
 
-static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
+static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
+                         BIGNUM **kinvp, BIGNUM **rp,
+                         const unsigned char *dgst, int dlen)
        {
        BN_CTX *ctx;
        BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
@@ -237,11 +266,25 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 
        /* Get random k */
        do
-               if (!BN_rand_range(&k, dsa->q)) goto err;
-       while (BN_is_zero(&k));
+               {
+#ifndef OPENSSL_NO_SHA512
+               if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
+                       {
+                       /* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from
+                        * SHA512(private_key + H(message) + random). This protects the
+                        * private key from a weak PRNG. */
+                       if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
+                                                  dlen, ctx))
+                               goto err;
+                       }
+               else
+#endif
+                       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);
+               BN_set_flags(&k, BN_FLG_CONSTTIME);
                }
 
        if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
@@ -308,7 +351,7 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
        BN_CTX *ctx;
        BIGNUM u1,u2,t1;
        BN_MONT_CTX *mont=NULL;
-       int ret = -1, i, j;
+       int ret = -1, i;
        if (!dsa->p || !dsa->q || !dsa->g)
                {
                DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
@@ -323,20 +366,26 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
                return -1;
                }
 
-       if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
+#ifdef OPENSSL_FIPS
+       if(FIPS_selftest_failed())
+           {
+           FIPSerr(FIPS_F_DSA_DO_VERIFY,FIPS_R_FIPS_SELFTEST_FAILED);
+           return -1;
+           }
+
+       if (FIPS_module_mode() && !(dsa->flags & DSA_FLAG_NON_FIPS_ALLOW) 
+               && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
                {
-               DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
+               DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_KEY_SIZE_TOO_SMALL);
                return -1;
                }
+#endif
 
-       /* reject a excessive digest length (currently at most
-        * dsa-with-SHA256 is supported) */
-       if (dgst_len > SHA256_DIGEST_LENGTH)
+       if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
                {
-               DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+               DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
                return -1;
                }
-
        BN_init(&u1);
        BN_init(&u2);
        BN_init(&t1);
@@ -361,16 +410,12 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
        if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 
        /* save M in u1 */
-       if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
-       j = dgst_len << 3;
-       if (j > i)
-               {
+       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 */
-               if (!BN_rshift(&u1, &u1, j - i))
-                       goto err; 
-               }
+               dgst_len = (i >> 3);
+       if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 
        /* u1 = M * w mod q */
        if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;