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[ Multiple Vendors libc/glob() GLOB_BRACE|GLOB_LIMIT memory
exhaustion ]
Author: Maksymilian Arciemowicz
http://netbsd.org/donations/
http://securityreason.com/
http://cxib.net/
Date:
CVE: CVE-2011-0418
Affected Software (verified):
Original URL:
http://securityreason.com/achievement_securityalert/97
int glob(const char *pattern, int flags,
int (*errfunc)(const char *epath, int eerrno), glob_t *pglob);
Description
This function expands a filename wildcard which is passed as pattern.
GLOB_LIMIT Limit the amount of memory used by matches to ARG_MAX.
This
option should be set for programs that can be coerced to a denial of
service attack via patterns that expand to a very large number of
matches, such as a long string of /…//…
http://www.mail-archive.com/[email protected]/msg04960.html
Any 'pattern', should be limited and controlled by GLOB LIMIT.
Algorithm
used in glob(3) is not optimal, and doesn't support functions like
realpath() to eliminate duplicates. It's not easy to predict the
greatest possible complexity. Anyway in 2010, netbsd has extended
GLOB_LIMIT for a few new limits like: stats, readdir and malloc
OpenBSD has localized some integer overflow. In glob(3) function,
exists
some malloc() allowing allocate n<INT_MAX bytes into memory.
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/gen/glob.c.diff?r1=1.34;r2=1.35;f=h
however SIZE_MAX and INT_MAX doesn't protect us before memory
exhaustion. The real problem here is uncontrolled malloc(3) call.
globextend() will be executed a lot of times and we should reduce
calls
to glob0() and globexp1(). Therefore has been created a new limit,
limiting 'braces' used in 'pattern'.
If we don't reduce this call
-globextend()/netbsd–
static int
globextend(const Char *path, glob_t *pglob, size_t *limit)
{
char **pathv;
size_t i, newsize, len;
char *copy;
const Char *p;
_DIAGASSERT(path != NULL);
_DIAGASSERT(pglob != NULL);
newsize = sizeof(*pathv) * (2 + pglob->gl_pathc +
pglob->gl_offs);
pathv = pglob->gl_pathv ? realloc(pglob->gl_pathv, newsize) :
malloc(newsize); <==== UNSECURE CALL
…
newsize = sizeof(*pathv) * (2 + pglob->gl_pathc + pglob->gl_offs);
malloc(3) try allocate (4*pglob->gl_pathc) bytes.
in result we get
Jan 19 04:49:17 127 /netbsd: UVM: pid 615 (ftpd), uid 1003 killed:
out
of swap
Many servers are still vulnerable to the above vulnerability and
CVE-2010-4754, CVE-2010-4755, CVE-2010-4756, CVE-2010-2632. Servers
like
ftp.sun.com ftp.sony.com seems still be affected.
PoC:
change 'pattern' in
http://cxib.net/stuff/glob-0day.c
— 3. Fix —
Use CVS netbsd-5 netbsd-5-1 netbsd-5-0
http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/glob.c
— 4. Greets —
Specials thanks for Christos Zoulas, spz
sp3x, Infospec
Email:
GPG:
http://netbsd.org/donations/
http://securityreason.com/
http://cxib.net/
Best Regards
pub 4096R/D6E5B530 2010-09-19
uid Maksymilian Arciemowicz (cx) <[email protected]>
sub 4096R/58BA663C 2010-09-19
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