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DTLS/SCTP Finished Auth Bug

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PR: 2808

With DTLS/SCTP the SCTP extension SCTP-AUTH is used to protect DATA and
FORWARD-TSN chunks. The key for this extension is derived from the
master secret and changed with the next ChangeCipherSpec, whenever a new
key has been negotiated. The following Finished then already uses the
new key.  Unfortunately, the ChangeCipherSpec and Finished are part of
the same flight as the ClientKeyExchange, which is necessary for the
computation of the new secret. Hence, these messages are sent
immediately following each other, leaving the server very little time to
compute the new secret and pass it to SCTP before the finished arrives.
So the Finished is likely to be discarded by SCTP and a retransmission
becomes necessary. To prevent this issue, the Finished of the client is
still sent with the old key.
(cherry picked from commit 9fb523adce)
(cherry picked from commit b9ef52b078)
This commit is contained in:
Robin Seggelmann 2012-05-09 19:28:41 +02:00 committed by Dr. Stephen Henson
parent 44f4934bde
commit 025f7dbdd1
2 changed files with 33 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
ssl/d1_clnt.c
View File

@ -538,13 +538,6 @@ int dtls1_connect(SSL *s)
SSL3_ST_CW_CHANGE_A,SSL3_ST_CW_CHANGE_B);
if (ret <= 0) goto end;
#ifndef OPENSSL_NO_SCTP
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
#endif
s->state=SSL3_ST_CW_FINISHED_A;
s->init_num=0;
@ -571,6 +564,16 @@ int dtls1_connect(SSL *s)
goto end;
}
#ifndef OPENSSL_NO_SCTP
if (s->hit)
{
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
}
#endif
dtls1_reset_seq_numbers(s, SSL3_CC_WRITE);
break;
@ -613,6 +616,13 @@ int dtls1_connect(SSL *s)
}
else
{
#ifndef OPENSSL_NO_SCTP
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
#endif
#ifndef OPENSSL_NO_TLSEXT
/* Allow NewSessionTicket if ticket expected */
if (s->tlsext_ticket_expected)

20
ssl/d1_srvr.c
View File

@ -722,10 +722,13 @@ int dtls1_accept(SSL *s)
if (ret <= 0) goto end;
#ifndef OPENSSL_NO_SCTP
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
if (!s->hit)
{
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
}
#endif
s->state=SSL3_ST_SW_FINISHED_A;
@ -750,7 +753,16 @@ int dtls1_accept(SSL *s)
if (ret <= 0) goto end;
s->state=SSL3_ST_SW_FLUSH;
if (s->hit)
{
s->s3->tmp.next_state=SSL3_ST_SR_FINISHED_A;
#ifndef OPENSSL_NO_SCTP
/* Change to new shared key of SCTP-Auth,
* will be ignored if no SCTP used.
*/
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_NEXT_AUTH_KEY, 0, NULL);
#endif
}
else
{
s->s3->tmp.next_state=SSL_ST_OK;