jimzah/freebsd-src
1
0
Fork 0
mirror of https://github.com/freebsd/freebsd-src.git synced 2024-11-26 20:12:44 +00:00
Code Issues Actions 2 Packages Projects Releases Wiki Activity

libalias: fix subtle racy problem in outside-inside forwarding

Browse Source 
sys/netinet/libalias/alias_db.c has internal static function UseLink()
that passes a link to CleanupLink() to verify if the link has expired.
If so, UseLink() may return NULL.

_FindLinkIn()'s usage of UseLink() is not quite correct.

Assume there is "redirect_port udp" configured to forward incoming
traffic for specific port to some internal address.
Such a rule creates partially specified permanent link.

After first such incoming packet libalias creates new fully specified
temporary LINK_UDP with default timeout of 60 seconds.
Also, in case of low traffic libalias may assign "timestamp"
for this new temporary link way in the past because
LibAliasTime is updated seldom and can keep old value
for tens of seconds, and it will be used for the temporary link.

It may happen that next incoming packet for redirected port
passed to _FindLinkIn() results in a call to UseLink()
that returns NULL due to detected expiration.
Immediate return of NULL results in broken translation:
either a packet is dropped (deny_incoming mode) or delivered to
original destination address instead of internal one.

Fix it with additional check for NULL to proceed with a search
for original partially specified link. In case of UDP,
it also recreates temporary fully specified link
with a call to ReLink().

Practical examples are "redirect_port udp" rules for unidirectional
SYSLOG protocol (port 514) or some low volume VPN encapsulated in UDP.

Thanks to Peter Much for initial analysis and first version of a patch.

Reported by:	Peter Much <pmc@citylink.dinoex.sub.org>
PR:		269770

(cherry picked from commit 8132e95909)
(cherry picked from commit e5b8538083)
This commit is contained in:
Eugene Grosbein 2024-08-19 10:34:37 +07:00
parent 1980b3dfa1
commit 41efd8eef3
1 changed files with 12 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
sys/netinet/libalias/alias_db.c
View File

@ -870,8 +870,18 @@ _FindLinkIn(struct libalias *la, struct in_addr dst_addr,
case 0:
LIST_FOREACH(lnk, &grp->full, all.in) {
if (lnk->dst_addr.s_addr == dst_addr.s_addr &&
lnk->dst_port == dst_port)
return (UseLink(la, lnk));
lnk->dst_port == dst_port) {
struct alias_link *found;
found = UseLink(la, lnk);
if (found != NULL)
return (found);
/* link expired */
grp = StartPointIn(la, alias_addr, alias_port, link_type, 0);
if (grp == NULL)
return (NULL);
break;
}
}
break;
case LINK_UNKNOWN_DEST_PORT: