diff options
| author | Emilia Kasper <emilia@openssl.org> | 2014-11-19 17:01:36 +0100 |
|---|---|---|
| committer | Emilia Kasper <emilia@openssl.org> | 2014-11-20 14:57:15 +0100 |
| commit | e94a6c0ede623960728415b68650a595e48f5a43 (patch) | |
| tree | 9ac092e0c94be7bbaeab1a766d4015dbe65896ca /ssl/d1_srvr.c | |
| parent | de2c7504ebd4ec15334ae151a31917753468f86f (diff) | |
Ensure SSL3_FLAGS_CCS_OK (or d1->change_cipher_spec_ok for DTLS) is reset
once the ChangeCipherSpec message is received. Previously, the server would
set the flag once at SSL3_ST_SR_CERT_VRFY and again at SSL3_ST_SR_FINISHED.
This would allow a second CCS to arrive and would corrupt the server state.
(Because the first CCS would latch the correct keys and subsequent CCS
messages would have to be encrypted, a MitM attacker cannot exploit this,
though.)
Thanks to Joeri de Ruiter for reporting this issue.
Reviewed-by: Matt Caswell <matt@openssl.org>
Diffstat (limited to 'ssl/d1_srvr.c')
| -rw-r--r-- | ssl/d1_srvr.c | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/ssl/d1_srvr.c b/ssl/d1_srvr.c index 1d2201de45..aef38bb754 100644 --- a/ssl/d1_srvr.c +++ b/ssl/d1_srvr.c @@ -264,6 +264,9 @@ int dtls1_accept(SSL *s) } s->init_num=0; + s->d1->change_cipher_spec_ok = 0; + /* Should have been reset by ssl3_get_finished, too. */ + s->s3->change_cipher_spec = 0; if (s->state != SSL_ST_RENEGOTIATE) { @@ -694,8 +697,14 @@ int dtls1_accept(SSL *s) case SSL3_ST_SR_CERT_VRFY_A: case SSL3_ST_SR_CERT_VRFY_B: - - s->d1->change_cipher_spec_ok = 1; + /* + * This *should* be the first time we enable CCS, but be + * extra careful about surrounding code changes. We need + * to set this here because we don't know if we're + * expecting a CertificateVerify or not. + */ + if (!s->s3->change_cipher_spec) + s->d1->change_cipher_spec_ok = 1; /* we should decide if we expected this one */ ret=ssl3_get_cert_verify(s); if (ret <= 0) goto end; @@ -711,7 +720,18 @@ int dtls1_accept(SSL *s) case SSL3_ST_SR_FINISHED_A: case SSL3_ST_SR_FINISHED_B: - s->d1->change_cipher_spec_ok = 1; + /* + * Enable CCS for resumed handshakes. + * In a full handshake, we end up here through + * SSL3_ST_SR_CERT_VRFY_B, so change_cipher_spec_ok was + * already set. Receiving a CCS clears the flag, so make + * sure not to re-enable it to ban duplicates. + * s->s3->change_cipher_spec is set when a CCS is + * processed in d1_pkt.c, and remains set until + * the client's Finished message is read. + */ + if (!s->s3->change_cipher_spec) + s->d1->change_cipher_spec_ok = 1; ret=ssl3_get_finished(s,SSL3_ST_SR_FINISHED_A, SSL3_ST_SR_FINISHED_B); if (ret <= 0) goto end; |