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There is a bug in tcp_output()'s implementation of the TCP_SIGNATURE

Browse Source 
(RFC 2385/TCP-MD5) kernel option.

If a tcpcb has TF_NOOPT flag, then tcp_addoptions() is not called,
and to.to_signature is an uninitialized stack variable. The value
is later used as write offset, which leads to writing to random
address.

Submitted by:	rstone, jtl
Security:	SA-16:05.tcp
This commit is contained in:
Gleb Smirnoff 2016-01-14 10:22:45 +00:00
parent c8358c6e0d
commit f73d9fd2f1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=293910
1 changed files with 4 additions and 2 deletions
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6
sys/netinet/tcp_output.c
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@ -752,8 +752,8 @@ tcp_output(struct tcpcb *tp)
* segments. Options for SYN-ACK segments are handled in TCP
* syncache.
*/
to.to_flags = 0;
if ((tp->t_flags & TF_NOOPT) == 0) {
to.to_flags = 0;
/* Maximum segment size. */
if (flags & TH_SYN) {
tp->snd_nxt = tp->iss;
@ -1233,7 +1233,7 @@ tcp_output(struct tcpcb *tp)
tp->snd_up = tp->snd_una; /* drag it along */
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE) {
if (to.to_flags & TOF_SIGNATURE) {
int sigoff = to.to_signature - opt;
tcp_signature_compute(m, 0, len, optlen,
(u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
@ -1713,6 +1713,7 @@ tcp_addoptions(struct tcpopt *to, u_char *optp)
bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
optp += sizeof(to->to_tsecr);
break;
#ifdef TCP_SIGNATURE
case TOF_SIGNATURE:
{
int siglen = TCPOLEN_SIGNATURE - 2;
@ -1731,6 +1732,7 @@ tcp_addoptions(struct tcpopt *to, u_char *optp)
*optp++ = 0;
break;
}
#endif
case TOF_SACK:
{
int sackblks = 0;