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dix: integer overflow in GetHosts() [CVE-2014-8092 2/4] 

GetHosts() iterates over all the hosts it has in memory, and copies
them to a buffer. The buffer length is calculated by iterating over
all the hosts and adding up all of their combined length. There is a
potential integer overflow, if there are lots and lots of hosts (with
a combined length of > ~4 gig). This should be possible by repeatedly
calling ProcChangeHosts() on 64bit machines with enough memory.

This patch caps the list at 1mb, because multi-megabyte hostname
lists for X access control are insane.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit bc8e20430b)
Signed-off-by: Julien Cristau <jcristau@debian.org>
This commit is contained in:
Alan Coopersmith 2014-01-06 23:30:14 -08:00 committed by Julien Cristau
parent b022d4ef9d
commit cbfdb284c9
1 changed files with 6 additions and 0 deletions
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6
os/access.c
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@ -1323,6 +1323,10 @@ GetHosts(void **data, int *pnHosts, int *pLen, BOOL * pEnabled)
for (host = validhosts; host; host = host->next) {
nHosts++;
n += pad_to_int32(host->len) + sizeof(xHostEntry);
/* Could check for INT_MAX, but in reality having more than 1mb of
hostnames in the access list is ridiculous */
if (n >= 1048576)
break;
}
if (n) {
*data = ptr = malloc(n);
@ -1331,6 +1335,8 @@ GetHosts(void **data, int *pnHosts, int *pLen, BOOL * pEnabled)
}
for (host = validhosts; host; host = host->next) {
len = host->len;
if ((ptr + sizeof(xHostEntry) + len) > (data + n))
break;
((xHostEntry *) ptr)->family = host->family;
((xHostEntry *) ptr)->length = len;
ptr += sizeof(xHostEntry);