diff options
Diffstat (limited to 'pkgs/build-support/build-fhs-userenv/chrootenv.c')
-rw-r--r-- | pkgs/build-support/build-fhs-userenv/chrootenv.c | 242 |
1 files changed, 0 insertions, 242 deletions
diff --git a/pkgs/build-support/build-fhs-userenv/chrootenv.c b/pkgs/build-support/build-fhs-userenv/chrootenv.c deleted file mode 100644 index d3b49db0e42d..000000000000 --- a/pkgs/build-support/build-fhs-userenv/chrootenv.c +++ /dev/null @@ -1,242 +0,0 @@ -#define _GNU_SOURCE - -#include <errno.h> -#include <error.h> - -#define errorf(status, fmt, ...) \ - error_at_line(status, errno, __FILE__, __LINE__, fmt, ##__VA_ARGS__) - -#include <dirent.h> -#include <ftw.h> -#include <sched.h> -#include <stdarg.h> -#include <stdbool.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include <sysexits.h> -#include <unistd.h> - -#include <sys/mount.h> -#include <sys/stat.h> -#include <sys/wait.h> - -#define LEN(x) (sizeof(x) / sizeof(*x)) - -// TODO: fill together with @abbradar when he gets better -const char *environ_blacklist[] = {}; - -void environ_blacklist_filter() { - for (size_t i = 0; i < LEN(environ_blacklist); i++) { - if (unsetenv(environ_blacklist[i]) < 0) - errorf(EX_OSERR, "unsetenv(%s)", environ_blacklist[i]); - } -} - -void bind(const char *from, const char *to) { - if (mkdir(to, 0755) < 0) - errorf(EX_IOERR, "mkdir(%s)", to); - - if (mount(from, to, "bind", MS_BIND | MS_REC, NULL) < 0) - errorf(EX_OSERR, "mount(%s, %s)", from, to); -} - -const char *bind_blacklist[] = {".", "..", "bin", "etc", "host", "usr"}; - -bool str_contains(const char *needle, const char **haystack, size_t len) { - for (size_t i = 0; i < len; i++) { - if (!strcmp(needle, haystack[i])) - return true; - } - - return false; -} - -bool is_dir(const char *path) { - struct stat buf; - - if (stat(path, &buf) < 0) - errorf(EX_IOERR, "stat(%s)", path); - - return S_ISDIR(buf.st_mode); -} - -void bind_to_cwd(const char *prefix) { - DIR *prefix_dir = opendir(prefix); - - if (prefix_dir == NULL) - errorf(EX_IOERR, "opendir(%s)", prefix); - - struct dirent *prefix_dirent; - - while (prefix_dirent = readdir(prefix_dir)) { - if (str_contains(prefix_dirent->d_name, bind_blacklist, - LEN(bind_blacklist))) - continue; - - char *prefix_dirent_path; - - if (asprintf(&prefix_dirent_path, "%s%s", prefix, prefix_dirent->d_name) < - 0) - errorf(EX_IOERR, "asprintf"); - - if (is_dir(prefix_dirent_path)) { - bind(prefix_dirent_path, prefix_dirent->d_name); - } else { - char *host_target; - - if (asprintf(&host_target, "host/%s", prefix_dirent->d_name) < 0) - errorf(EX_IOERR, "asprintf"); - - if (symlink(host_target, prefix_dirent->d_name) < 0) - errorf(EX_IOERR, "symlink(%s, %s)", host_target, prefix_dirent->d_name); - - free(host_target); - } - - free(prefix_dirent_path); - } - - bind(prefix, "host"); - - if (closedir(prefix_dir) < 0) - errorf(EX_IOERR, "closedir(%s)", prefix); -} - -void spitf(const char *path, char *fmt, ...) { - va_list args; - va_start(args, fmt); - - FILE *f = fopen(path, "w"); - - if (f == NULL) - errorf(EX_IOERR, "spitf(%s): fopen", path); - - if (vfprintf(f, fmt, args) < 0) - errorf(EX_IOERR, "spitf(%s): vfprintf", path); - - if (fclose(f) < 0) - errorf(EX_IOERR, "spitf(%s): fclose", path); -} - -int nftw_remove(const char *path, const struct stat *sb, int type, - struct FTW *ftw) { - return remove(path); -} - -char *root; - -void root_cleanup() { - if (nftw(root, nftw_remove, getdtablesize(), - FTW_DEPTH | FTW_MOUNT | FTW_PHYS) < 0) - errorf(EX_IOERR, "nftw(%s)", root); - - free(root); -} - -#define REQUIREMENTS \ - "Requires Linux version >= 3.19 built with CONFIG_USER_NS option.\n" - -int main(int argc, char *argv[]) { - const char *self = *argv++; - - if (argc < 2) { - fprintf(stderr, "Usage: %s command [arguments...]\n" REQUIREMENTS, self); - exit(EX_USAGE); - } - - if (getenv("NIX_CHROOTENV") != NULL) { - fputs("Can't create chrootenv inside chrootenv!\n", stderr); - exit(EX_USAGE); - } - - if (setenv("NIX_CHROOTENV", "1", false) < 0) - errorf(EX_OSERR, "setenv(NIX_CHROOTENV, 1)"); - - const char *temp = getenv("TMPDIR"); - - if (temp == NULL) - temp = "/tmp"; - - if (asprintf(&root, "%s/chrootenvXXXXXX", temp) < 0) - errorf(EX_IOERR, "asprintf"); - - root = mkdtemp(root); - - if (root == NULL) - errorf(EX_IOERR, "mkdtemp(%s)", root); - - atexit(root_cleanup); - - // Don't make root private so that privilege drops inside chroot are possible: - if (chmod(root, 0755) < 0) - errorf(EX_IOERR, "chmod(%s, 0755)", root); - - pid_t cpid = fork(); - - if (cpid < 0) - errorf(EX_OSERR, "fork"); - - if (cpid == 0) { - uid_t uid = getuid(); - gid_t gid = getgid(); - - // If we are root, no need to create new user namespace. - if (uid == 0) { - if (unshare(CLONE_NEWNS) < 0) { - fputs(REQUIREMENTS, stderr); - errorf(EX_OSERR, "unshare"); - } - // Mark all mounted filesystems as slave so changes - // don't propagate to the parent mount namespace. - if (mount(NULL, "/", NULL, MS_REC | MS_SLAVE, NULL) < 0) - errorf(EX_OSERR, "mount"); - } else { - // Create new mount and user namespaces. CLONE_NEWUSER - // requires a program to be non-threaded. - if (unshare(CLONE_NEWNS | CLONE_NEWUSER) < 0) { - fputs(access("/proc/sys/kernel/unprivileged_userns_clone", F_OK) - ? REQUIREMENTS - : "Run: sudo sysctl -w kernel.unprivileged_userns_clone=1\n", - stderr); - errorf(EX_OSERR, "unshare"); - } - - // Map users and groups to the parent namespace. - // setgroups is only available since Linux 3.19: - spitf("/proc/self/setgroups", "deny"); - - spitf("/proc/self/uid_map", "%d %d 1", uid, uid); - spitf("/proc/self/gid_map", "%d %d 1", gid, gid); - } - - if (chdir(root) < 0) - errorf(EX_IOERR, "chdir(%s)", root); - - bind_to_cwd("/"); - - if (chroot(root) < 0) - errorf(EX_OSERR, "chroot(%s)", root); - - if (chdir("/") < 0) - errorf(EX_IOERR, "chdir(/)"); - - environ_blacklist_filter(); - - if (execvp(*argv, argv) < 0) - errorf(EX_OSERR, "execvp(%s)", *argv); - } - - int status; - - if (waitpid(cpid, &status, 0) < 0) - errorf(EX_OSERR, "waitpid(%d)", cpid); - - if (WIFEXITED(status)) { - return WEXITSTATUS(status); - } else if (WIFSIGNALED(status)) { - kill(getpid(), WTERMSIG(status)); - } - - return EX_OSERR; -} |