diff options
| author | Bodo Möller <bodo@openssl.org> | 2003-03-19 19:20:30 +0000 |
|---|---|---|
| committer | Bodo Möller <bodo@openssl.org> | 2003-03-19 19:20:30 +0000 |
| commit | ef42d6a4eda7af66fcd8168bfb8f11f160f22913 (patch) | |
| tree | 6f5a56d0b641969fc7a2bd1bb3f1513b33509562 | |
| parent | 00223b969de93dcf7ecfd4a63fb6d151d589dc57 (diff) | |
| download | openssl-ef42d6a4eda7af66fcd8168bfb8f11f160f22913.tar.gz | |
countermeasure against new Klima-Pokorny-Rosa atack
| -rw-r--r-- | CHANGES | 6 | ||||
| -rw-r--r-- | ssl/s3_srvr.c | 24 |
2 files changed, 16 insertions, 14 deletions
@@ -4,7 +4,11 @@ Changes between 0.9.6i and 0.9.6j [xx XXX 2003] - *) + *) Countermeasure against the Klima-Pokorny-Rosa extension of + Bleichbacher's attack on PKCS #1 v1.5 padding: treat + a protocol version number mismatch like a decryption error + in ssl3_get_client_key_exchange (ssl/s3_srvr.c). + [Bodo Moeller] Changes between 0.9.6h and 0.9.6i [19 Feb 2003] diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c index 6b414cfa5c..3f4818e888 100644 --- a/ssl/s3_srvr.c +++ b/ssl/s3_srvr.c @@ -1425,7 +1425,7 @@ static int ssl3_get_client_key_exchange(SSL *s) if (i != SSL_MAX_MASTER_KEY_LENGTH) { al=SSL_AD_DECODE_ERROR; - SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_RSA_DECRYPT); + /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_RSA_DECRYPT); */ } if ((al == -1) && !((p[0] == (s->client_version>>8)) && (p[1] == (s->client_version & 0xff)))) @@ -1441,30 +1441,28 @@ static int ssl3_get_client_key_exchange(SSL *s) (p[0] == (s->version>>8)) && (p[1] == (s->version & 0xff)))) { al=SSL_AD_DECODE_ERROR; - SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER); - goto f_err; + /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER); */ + + /* The Klima-Pokorny-Rosa extension of Bleichenbacher's attack + * (http://eprint.iacr.org/2003/052/) exploits the version + * number check as a "bad version oracle" -- an alert would + * reveal that the plaintext corresponding to some ciphertext + * made up by the adversary is properly formatted except + * that the version number is wrong. To avoid such attacks, + * we should treat this just like any other decryption error. */ } } if (al != -1) { -#if 0 - goto f_err; -#else /* Some decryption failure -- use random value instead as countermeasure * against Bleichenbacher's attack on PKCS #1 v1.5 RSA padding - * (see RFC 2246, section 7.4.7.1). - * But note that due to length and protocol version checking, the - * attack is impractical anyway (see section 5 in D. Bleichenbacher: - * "Chosen Ciphertext Attacks Against Protocols Based on the RSA - * Encryption Standard PKCS #1", CRYPTO '98, LNCS 1462, pp. 1-12). - */ + * (see RFC 2246, section 7.4.7.1). */ ERR_clear_error(); i = SSL_MAX_MASTER_KEY_LENGTH; p[0] = s->client_version >> 8; p[1] = s->client_version & 0xff; RAND_pseudo_bytes(p+2, i-2); /* should be RAND_bytes, but we cannot work around a failure */ -#endif } s->session->master_key_length= |