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The TCP code did not do sufficient checks on whether incoming packets

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were destined for a broadcast IP address. All TCP packets with a
broadcast destination must be ignored. The system only ignored packets
that were _link-layer_ broadcasts or multicast. We need to check the
IP address too since it is quite possible for a broadcast IP address
to come in with a unicast link-layer address.

Note that the check existed prior to CSRG revision 7.35, but was
removed. This commit effectively backs out that nine-year-old change.

PR:		misc/35022
This commit is contained in:
Crist J. Clark 2002-02-25 08:29:21 +00:00
parent 10acff06b9
commit 2ca2159f22
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=91234
2 changed files with 26 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
sys/netinet/tcp_input.c
View File

@ -798,11 +798,15 @@ tcp_input(m, off0)
}
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
* in_broadcast() should never return true on a received
* packet with M_BCAST not set.
*
* Packets with a multicast source address should also
* be discarded.
*
* It is possible for a malicious (or misconfigured)
* attacker to send unicast link-layer packets with a
* broadcast IP address. Use in_broadcast() to find them.
* (This check was erroneously removed in CSRG revision
* 7.35.)
*
* Packets with a multicast source address should also
* be discarded.
*/
if (m->m_flags & (M_BCAST|M_MCAST))
goto drop;
@ -815,7 +819,8 @@ tcp_input(m, off0)
#endif
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
/*
* SYN appears to be valid; create compressed TCP state
@ -2171,7 +2176,8 @@ tcp_input(m, off0)
#endif /* INET6 */
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
/* IPv6 anycast check is done at tcp6_input() */

20
sys/netinet/tcp_reass.c
View File

@ -798,11 +798,15 @@ tcp_input(m, off0)
}
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
* in_broadcast() should never return true on a received
* packet with M_BCAST not set.
*
* Packets with a multicast source address should also
* be discarded.
*
* It is possible for a malicious (or misconfigured)
* attacker to send unicast link-layer packets with a
* broadcast IP address. Use in_broadcast() to find them.
* (This check was erroneously removed in CSRG revision
* 7.35.)
*
* Packets with a multicast source address should also
* be discarded.
*/
if (m->m_flags & (M_BCAST|M_MCAST))
goto drop;
@ -815,7 +819,8 @@ tcp_input(m, off0)
#endif
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
/*
* SYN appears to be valid; create compressed TCP state
@ -2171,7 +2176,8 @@ tcp_input(m, off0)
#endif /* INET6 */
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
/* IPv6 anycast check is done at tcp6_input() */