diff options
| author | Richard Levitte <levitte@openssl.org> | 2017-01-26 11:47:36 +0100 |
|---|---|---|
| committer | Matt Caswell <matt@openssl.org> | 2017-01-26 10:56:29 +0000 |
| commit | 918d8eadb35746456fd1a9d4e219c63ff706173e (patch) | |
| tree | 643482a660cd111da3f98b8042a4a51cb2175991 | |
| parent | 760d04342a495ee86bf5adc71a91d126af64397f (diff) | |
Better check of DH parameters in TLS data
When the client reads DH parameters from the TLS stream, we only
checked that they all are non-zero. This change updates the check
as follows:
check that p is odd
check that 1 < g < p - 1
Reviewed-by: Matt Caswell <matt@openssl.org>
| -rw-r--r-- | ssl/s3_clnt.c | 44 |
1 files changed, 33 insertions, 11 deletions
diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c index 218534734d..32f2f1aeed 100644 --- a/ssl/s3_clnt.c +++ b/ssl/s3_clnt.c @@ -1710,12 +1710,6 @@ int ssl3_get_key_exchange(SSL *s) } p += i; - if (BN_is_zero(dh->p)) { - SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_P_VALUE); - goto f_err; - } - - if (2 > n - param_len) { SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_LENGTH_TOO_SHORT); goto f_err; @@ -1736,11 +1730,6 @@ int ssl3_get_key_exchange(SSL *s) } p += i; - if (BN_is_zero(dh->g)) { - SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_G_VALUE); - goto f_err; - } - if (2 > n - param_len) { SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_LENGTH_TOO_SHORT); goto f_err; @@ -1767,6 +1756,39 @@ int ssl3_get_key_exchange(SSL *s) goto f_err; } + /*- + * Check that p and g are suitable enough + * + * p is odd + * 1 < g < p - 1 + */ + { + BIGNUM *tmp = NULL; + + if (!BN_is_odd(dh->p)) { + SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_P_VALUE); + goto f_err; + } + if (BN_is_negative(dh->g) || BN_is_zero(dh->g) + || BN_is_one(dh->g)) { + SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_G_VALUE); + goto f_err; + } + if ((tmp = BN_new()) == NULL + || BN_copy(tmp, dh->p) == NULL + || !BN_sub_word(tmp, 1)) { + BN_free(tmp); + SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, ERR_R_BN_LIB); + goto err; + } + if (BN_cmp(dh->g, tmp) >= 0) { + BN_free(tmp); + SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_G_VALUE); + goto f_err; + } + BN_free(tmp); + } + # ifndef OPENSSL_NO_RSA if (alg_a & SSL_aRSA) pkey = |