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Diffstat (limited to 'thirdparty/mbedtls/library/ecdsa.c')
-rw-r--r--thirdparty/mbedtls/library/ecdsa.c125
1 files changed, 108 insertions, 17 deletions
diff --git a/thirdparty/mbedtls/library/ecdsa.c b/thirdparty/mbedtls/library/ecdsa.c
index dc19384d61..2b4800642d 100644
--- a/thirdparty/mbedtls/library/ecdsa.c
+++ b/thirdparty/mbedtls/library/ecdsa.c
@@ -172,11 +172,11 @@ static void ecdsa_restart_det_free( mbedtls_ecdsa_restart_det_ctx *ctx )
}
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
-#define ECDSA_RS_ECP &rs_ctx->ecp
+#define ECDSA_RS_ECP ( rs_ctx == NULL ? NULL : &rs_ctx->ecp )
/* Utility macro for checking and updating ops budget */
#define ECDSA_BUDGET( ops ) \
- MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, &rs_ctx->ecp, ops ) );
+ MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, ECDSA_RS_ECP, ops ) );
/* Call this when entering a function that needs its own sub-context */
#define ECDSA_RS_ENTER( SUB ) do { \
@@ -254,6 +254,8 @@ static int ecdsa_sign_restartable( mbedtls_ecp_group *grp,
mbedtls_mpi *r, mbedtls_mpi *s,
const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+ int (*f_rng_blind)(void *, unsigned char *, size_t),
+ void *p_rng_blind,
mbedtls_ecdsa_restart_ctx *rs_ctx )
{
int ret, key_tries, sign_tries;
@@ -323,7 +325,9 @@ static int ecdsa_sign_restartable( mbedtls_ecp_group *grp,
mul:
#endif
MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &R, pk, &grp->G,
- f_rng, p_rng, ECDSA_RS_ECP ) );
+ f_rng_blind,
+ p_rng_blind,
+ ECDSA_RS_ECP ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pr, &R.X, &grp->N ) );
}
while( mbedtls_mpi_cmp_int( pr, 0 ) == 0 );
@@ -349,7 +353,8 @@ modn:
* Generate a random value to blind inv_mod in next step,
* avoiding a potential timing leak.
*/
- MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng, p_rng ) );
+ MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng_blind,
+ p_rng_blind ) );
/*
* Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
@@ -392,8 +397,9 @@ int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
ECDSA_VALIDATE_RET( f_rng != NULL );
ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
+ /* Use the same RNG for both blinding and ephemeral key generation */
return( ecdsa_sign_restartable( grp, r, s, d, buf, blen,
- f_rng, p_rng, NULL ) );
+ f_rng, p_rng, f_rng, p_rng, NULL ) );
}
#endif /* !MBEDTLS_ECDSA_SIGN_ALT */
@@ -405,6 +411,8 @@ static int ecdsa_sign_det_restartable( mbedtls_ecp_group *grp,
mbedtls_mpi *r, mbedtls_mpi *s,
const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
mbedtls_md_type_t md_alg,
+ int (*f_rng_blind)(void *, unsigned char *, size_t),
+ void *p_rng_blind,
mbedtls_ecdsa_restart_ctx *rs_ctx )
{
int ret;
@@ -451,8 +459,70 @@ sign:
ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,
mbedtls_hmac_drbg_random, p_rng );
#else
- ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,
- mbedtls_hmac_drbg_random, p_rng, rs_ctx );
+ if( f_rng_blind != NULL )
+ ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,
+ mbedtls_hmac_drbg_random, p_rng,
+ f_rng_blind, p_rng_blind, rs_ctx );
+ else
+ {
+ mbedtls_hmac_drbg_context *p_rng_blind_det;
+
+#if !defined(MBEDTLS_ECP_RESTARTABLE)
+ /*
+ * To avoid reusing rng_ctx and risking incorrect behavior we seed a
+ * second HMAC-DRBG with the same seed. We also apply a label to avoid
+ * reusing the bits of the ephemeral key for blinding and eliminate the
+ * risk that they leak this way.
+ */
+ const char* blind_label = "BLINDING CONTEXT";
+ mbedtls_hmac_drbg_context rng_ctx_blind;
+
+ mbedtls_hmac_drbg_init( &rng_ctx_blind );
+ p_rng_blind_det = &rng_ctx_blind;
+
+ mbedtls_hmac_drbg_seed_buf( p_rng_blind_det, md_info,
+ data, 2 * grp_len );
+ ret = mbedtls_hmac_drbg_update_ret( p_rng_blind_det,
+ (const unsigned char*) blind_label,
+ strlen( blind_label ) );
+ if( ret != 0 )
+ {
+ mbedtls_hmac_drbg_free( &rng_ctx_blind );
+ goto cleanup;
+ }
+#else
+ /*
+ * In the case of restartable computations we would either need to store
+ * the second RNG in the restart context too or set it up at every
+ * restart. The first option would penalize the correct application of
+ * the function and the second would defeat the purpose of the
+ * restartable feature.
+ *
+ * Therefore in this case we reuse the original RNG. This comes with the
+ * price that the resulting signature might not be a valid deterministic
+ * ECDSA signature with a very low probability (same magnitude as
+ * successfully guessing the private key). However even then it is still
+ * a valid ECDSA signature.
+ */
+ p_rng_blind_det = p_rng;
+#endif /* MBEDTLS_ECP_RESTARTABLE */
+
+ /*
+ * Since the output of the RNGs is always the same for the same key and
+ * message, this limits the efficiency of blinding and leaks information
+ * through side channels. After mbedtls_ecdsa_sign_det() is removed NULL
+ * won't be a valid value for f_rng_blind anymore. Therefore it should
+ * be checked by the caller and this branch and check can be removed.
+ */
+ ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,
+ mbedtls_hmac_drbg_random, p_rng,
+ mbedtls_hmac_drbg_random, p_rng_blind_det,
+ rs_ctx );
+
+#if !defined(MBEDTLS_ECP_RESTARTABLE)
+ mbedtls_hmac_drbg_free( &rng_ctx_blind );
+#endif
+ }
#endif /* MBEDTLS_ECDSA_SIGN_ALT */
cleanup:
@@ -465,19 +535,40 @@ cleanup:
}
/*
- * Deterministic signature wrapper
+ * Deterministic signature wrappers
*/
-int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
- const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
- mbedtls_md_type_t md_alg )
+int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r,
+ mbedtls_mpi *s, const mbedtls_mpi *d,
+ const unsigned char *buf, size_t blen,
+ mbedtls_md_type_t md_alg )
+{
+ ECDSA_VALIDATE_RET( grp != NULL );
+ ECDSA_VALIDATE_RET( r != NULL );
+ ECDSA_VALIDATE_RET( s != NULL );
+ ECDSA_VALIDATE_RET( d != NULL );
+ ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
+
+ return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg,
+ NULL, NULL, NULL ) );
+}
+
+int mbedtls_ecdsa_sign_det_ext( mbedtls_ecp_group *grp, mbedtls_mpi *r,
+ mbedtls_mpi *s, const mbedtls_mpi *d,
+ const unsigned char *buf, size_t blen,
+ mbedtls_md_type_t md_alg,
+ int (*f_rng_blind)(void *, unsigned char *,
+ size_t),
+ void *p_rng_blind )
{
ECDSA_VALIDATE_RET( grp != NULL );
ECDSA_VALIDATE_RET( r != NULL );
ECDSA_VALIDATE_RET( s != NULL );
ECDSA_VALIDATE_RET( d != NULL );
ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
+ ECDSA_VALIDATE_RET( f_rng_blind != NULL );
- return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg, NULL ) );
+ return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg,
+ f_rng_blind, p_rng_blind, NULL ) );
}
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
@@ -656,11 +747,9 @@ int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
mbedtls_mpi_init( &s );
#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
- (void) f_rng;
- (void) p_rng;
-
MBEDTLS_MPI_CHK( ecdsa_sign_det_restartable( &ctx->grp, &r, &s, &ctx->d,
- hash, hlen, md_alg, rs_ctx ) );
+ hash, hlen, md_alg, f_rng,
+ p_rng, rs_ctx ) );
#else
(void) md_alg;
@@ -668,8 +757,10 @@ int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,
hash, hlen, f_rng, p_rng ) );
#else
+ /* Use the same RNG for both blinding and ephemeral key generation */
MBEDTLS_MPI_CHK( ecdsa_sign_restartable( &ctx->grp, &r, &s, &ctx->d,
- hash, hlen, f_rng, p_rng, rs_ctx ) );
+ hash, hlen, f_rng, p_rng, f_rng,
+ p_rng, rs_ctx ) );
#endif /* MBEDTLS_ECDSA_SIGN_ALT */
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-04 19:08:17 +0000