diff options
| author | Dr. Stephen Henson <steve@openssl.org> | 2012-01-04 19:10:16 +0000 |
|---|---|---|
| committer | Dr. Stephen Henson <steve@openssl.org> | 2012-01-04 19:10:16 +0000 |
| commit | eebefe35e768ed73aa443fe84bf8db58960fac13 (patch) | |
| tree | 8ba3336b73dc59623cd38d31242ae0b72f9898da /ssl/d1_pkt.c | |
| parent | 1db0bbdc76cfd715b60a155220328c15409cf1aa (diff) | |
Submitted by: Robin Seggelmann <seggelmann@fh-muenster.de>, Michael Tuexen <tuexen@fh-muenster.de>
Reviewed by: steve
Fix for DTLS plaintext recovery attack discovered by Nadhem Alfardan and
Kenny Paterson.
Diffstat (limited to 'ssl/d1_pkt.c')
| -rw-r--r-- | ssl/d1_pkt.c | 26 |
1 files changed, 16 insertions, 10 deletions
diff --git a/ssl/d1_pkt.c b/ssl/d1_pkt.c index e4f47e98e6..83702e5309 100644 --- a/ssl/d1_pkt.c +++ b/ssl/d1_pkt.c @@ -335,6 +335,7 @@ dtls1_process_record(SSL *s) SSL3_RECORD *rr; unsigned int mac_size; unsigned char md[EVP_MAX_MD_SIZE]; + int decryption_failed_or_bad_record_mac = 0; rr= &(s->s3->rrec); @@ -369,13 +370,10 @@ dtls1_process_record(SSL *s) enc_err = s->method->ssl3_enc->enc(s,0); if (enc_err <= 0) { - /* decryption failed, silently discard message */ - if (enc_err < 0) - { - rr->length = 0; - s->packet_length = 0; - } - goto err; + /* To minimize information leaked via timing, we will always + * perform all computations before discarding the message. + */ + decryption_failed_or_bad_record_mac = 1; } #ifdef TLS_DEBUG @@ -401,7 +399,7 @@ if ( (sess == NULL) || SSLerr(SSL_F_DTLS1_PROCESS_RECORD,SSL_R_PRE_MAC_LENGTH_TOO_LONG); goto f_err; #else - goto err; + decryption_failed_or_bad_record_mac = 1; #endif } /* check the MAC for rr->input (it's in mac_size bytes at the tail) */ @@ -412,17 +410,25 @@ if ( (sess == NULL) || SSLerr(SSL_F_DTLS1_PROCESS_RECORD,SSL_R_LENGTH_TOO_SHORT); goto f_err; #else - goto err; + decryption_failed_or_bad_record_mac = 1; #endif } rr->length-=mac_size; s->method->ssl3_enc->mac(s,md,0); if (memcmp(md,&(rr->data[rr->length]),mac_size) != 0) { - goto err; + decryption_failed_or_bad_record_mac = 1; } } + if (decryption_failed_or_bad_record_mac) + { + /* decryption failed, silently discard message */ + rr->length = 0; + s->packet_length = 0; + goto err; + } + /* r->length is now just compressed */ if (s->expand != NULL) { |