4b1cf5afb8
Changes:
* doesn't handle root user separately
* doesn't chdir("/") which makes using it seamless
* only bind mounts, doesn't symlink (i.e. files)
Incidentally, fixes #33106.
It's about two times shorter than the previous version, and much
easier to read/follow through. It uses GLib quite heavily, along with
RAII (available in GCC/Clang).
140 lines
3.4 KiB
C
140 lines
3.4 KiB
C
#define _GNU_SOURCE
|
|
|
|
#include <glib.h>
|
|
#include <glib/gstdio.h>
|
|
|
|
#include <errno.h>
|
|
#include <sched.h>
|
|
#include <unistd.h>
|
|
|
|
#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
|
|
#define fail_if(expr) \
|
|
if (expr) \
|
|
fail(#expr, errno);
|
|
|
|
#include <ftw.h>
|
|
|
|
#include <sys/mount.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/types.h>
|
|
#include <sys/wait.h>
|
|
|
|
const gchar *bind_blacklist[] = {"bin", "etc", "host", "usr", NULL};
|
|
|
|
void bind_mount(const gchar *source, const gchar *target) {
|
|
fail_if(g_mkdir(target, 0755));
|
|
fail_if(mount(source, target, "bind", MS_BIND | MS_REC, NULL));
|
|
}
|
|
|
|
void bind_mount_host(const gchar *host, const gchar *guest) {
|
|
g_autofree gchar *point = g_build_filename(guest, "host", NULL);
|
|
bind_mount(host, point);
|
|
}
|
|
|
|
void bind_mount_item(const gchar *host, const gchar *guest, const gchar *name) {
|
|
g_autofree gchar *source = g_build_filename(host, name, NULL);
|
|
g_autofree gchar *target = g_build_filename(guest, name, NULL);
|
|
|
|
if (G_LIKELY(g_file_test(source, G_FILE_TEST_IS_DIR)))
|
|
bind_mount(source, target);
|
|
}
|
|
|
|
void bind(const gchar *host, const gchar *guest) {
|
|
g_autoptr(GError) err = NULL;
|
|
g_autoptr(GDir) dir = g_dir_open(host, 0, &err);
|
|
|
|
if (err != NULL)
|
|
fail("g_dir_open", errno);
|
|
|
|
const gchar *item;
|
|
|
|
while (item = g_dir_read_name(dir))
|
|
if (!g_strv_contains(bind_blacklist, item))
|
|
bind_mount_item(host, guest, item);
|
|
|
|
bind_mount_host(host, guest);
|
|
}
|
|
|
|
void spit(const char *path, char *fmt, ...) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
|
|
FILE *f = g_fopen(path, "w");
|
|
|
|
if (f == NULL)
|
|
fail("g_fopen", errno);
|
|
|
|
g_vfprintf(f, fmt, args);
|
|
fclose(f);
|
|
}
|
|
|
|
int nftw_remove(const char *path, const struct stat *sb, int type,
|
|
struct FTW *ftw) {
|
|
return remove(path);
|
|
}
|
|
|
|
int main(gint argc, gchar **argv) {
|
|
const gchar *self = *argv++;
|
|
|
|
if (argc < 2) {
|
|
g_message("%s command [arguments...]", self);
|
|
return 1;
|
|
}
|
|
|
|
if (g_getenv("NIX_CHROOTENV"))
|
|
g_warning("chrootenv doesn't stack!");
|
|
else
|
|
g_setenv("NIX_CHROOTENV", "", TRUE);
|
|
|
|
g_autofree gchar *prefix =
|
|
g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
|
|
|
|
fail_if(!g_mkdtemp_full(prefix, 0755));
|
|
|
|
pid_t cpid = fork();
|
|
|
|
if (cpid < 0)
|
|
fail("fork", errno);
|
|
|
|
else if (cpid == 0) {
|
|
uid_t uid = getuid();
|
|
gid_t gid = getgid();
|
|
|
|
if (unshare(CLONE_NEWNS | CLONE_NEWUSER) < 0) {
|
|
int unshare_errno = errno;
|
|
|
|
g_message("Requires Linux version >= 3.19 built with CONFIG_USER_NS");
|
|
if (g_file_test("/proc/sys/kernel/unprivileged_userns_clone",
|
|
G_FILE_TEST_EXISTS))
|
|
g_message("Run: sudo sysctl -w kernel.unprivileged_userns_clone=1");
|
|
|
|
fail("unshare", unshare_errno);
|
|
}
|
|
|
|
spit("/proc/self/setgroups", "deny");
|
|
spit("/proc/self/uid_map", "%d %d 1", uid, uid);
|
|
spit("/proc/self/gid_map", "%d %d 1", gid, gid);
|
|
|
|
bind("/", prefix);
|
|
|
|
fail_if(chroot(prefix));
|
|
fail_if(execvp(*argv, argv));
|
|
}
|
|
|
|
else {
|
|
int status;
|
|
|
|
fail_if(waitpid(cpid, &status, 0) != cpid);
|
|
fail_if(nftw(prefix, nftw_remove, getdtablesize(),
|
|
FTW_DEPTH | FTW_MOUNT | FTW_PHYS));
|
|
|
|
if (WIFEXITED(status))
|
|
return WEXITSTATUS(status);
|
|
|
|
else if (WIFSIGNALED(status))
|
|
kill(getpid(), WTERMSIG(status));
|
|
|
|
return 1;
|
|
}
|
|
}
|