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8ec90bfd1a
Add tests for the new 'nosymfollow' mount option. We test to make sure that symlink traversal fails with ELOOP when 'nosymfollow' is set, but that readlink(2) and realpath(3) still work as expected. We also verify that statfs(2) correctly returns ST_NOSYMFOLLOW when we are mounted with the 'nosymfollow' option. Signed-off-by: Ross Zwisler <zwisler@google.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
219 lines
4.4 KiB
C
219 lines
4.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define _GNU_SOURCE
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <sched.h>
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#include <stdarg.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/vfs.h>
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#include <unistd.h>
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#ifndef MS_NOSYMFOLLOW
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# define MS_NOSYMFOLLOW 256 /* Do not follow symlinks */
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#endif
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#ifndef ST_NOSYMFOLLOW
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# define ST_NOSYMFOLLOW 0x2000 /* Do not follow symlinks */
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#endif
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#define DATA "/tmp/data"
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#define LINK "/tmp/symlink"
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#define TMP "/tmp"
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static void die(char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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vfprintf(stderr, fmt, ap);
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va_end(ap);
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exit(EXIT_FAILURE);
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}
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static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt,
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va_list ap)
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{
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ssize_t written;
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char buf[4096];
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int buf_len;
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int fd;
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buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
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if (buf_len < 0)
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die("vsnprintf failed: %s\n", strerror(errno));
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if (buf_len >= sizeof(buf))
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die("vsnprintf output truncated\n");
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fd = open(filename, O_WRONLY);
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if (fd < 0) {
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if ((errno == ENOENT) && enoent_ok)
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return;
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die("open of %s failed: %s\n", filename, strerror(errno));
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}
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written = write(fd, buf, buf_len);
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if (written != buf_len) {
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if (written >= 0) {
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die("short write to %s\n", filename);
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} else {
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die("write to %s failed: %s\n",
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filename, strerror(errno));
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}
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}
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if (close(fd) != 0)
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die("close of %s failed: %s\n", filename, strerror(errno));
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}
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static void maybe_write_file(char *filename, char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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vmaybe_write_file(true, filename, fmt, ap);
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va_end(ap);
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}
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static void write_file(char *filename, char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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vmaybe_write_file(false, filename, fmt, ap);
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va_end(ap);
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}
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static void create_and_enter_ns(void)
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{
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uid_t uid = getuid();
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gid_t gid = getgid();
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if (unshare(CLONE_NEWUSER) != 0)
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die("unshare(CLONE_NEWUSER) failed: %s\n", strerror(errno));
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maybe_write_file("/proc/self/setgroups", "deny");
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write_file("/proc/self/uid_map", "0 %d 1", uid);
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write_file("/proc/self/gid_map", "0 %d 1", gid);
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if (setgid(0) != 0)
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die("setgid(0) failed %s\n", strerror(errno));
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if (setuid(0) != 0)
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die("setuid(0) failed %s\n", strerror(errno));
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if (unshare(CLONE_NEWNS) != 0)
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die("unshare(CLONE_NEWNS) failed: %s\n", strerror(errno));
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}
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static void setup_symlink(void)
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{
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int data, err;
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data = creat(DATA, O_RDWR);
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if (data < 0)
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die("creat failed: %s\n", strerror(errno));
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err = symlink(DATA, LINK);
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if (err < 0)
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die("symlink failed: %s\n", strerror(errno));
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if (close(data) != 0)
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die("close of %s failed: %s\n", DATA, strerror(errno));
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}
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static void test_link_traversal(bool nosymfollow)
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{
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int link;
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link = open(LINK, 0, O_RDWR);
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if (nosymfollow) {
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if ((link != -1 || errno != ELOOP)) {
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die("link traversal unexpected result: %d, %s\n",
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link, strerror(errno));
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}
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} else {
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if (link < 0)
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die("link traversal failed: %s\n", strerror(errno));
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if (close(link) != 0)
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die("close of link failed: %s\n", strerror(errno));
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}
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}
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static void test_readlink(void)
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{
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char buf[4096];
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ssize_t ret;
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bzero(buf, sizeof(buf));
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ret = readlink(LINK, buf, sizeof(buf));
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if (ret < 0)
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die("readlink failed: %s\n", strerror(errno));
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if (strcmp(buf, DATA) != 0)
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die("readlink strcmp failed: '%s' '%s'\n", buf, DATA);
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}
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static void test_realpath(void)
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{
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char *path = realpath(LINK, NULL);
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if (!path)
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die("realpath failed: %s\n", strerror(errno));
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if (strcmp(path, DATA) != 0)
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die("realpath strcmp failed\n");
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free(path);
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}
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static void test_statfs(bool nosymfollow)
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{
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struct statfs buf;
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int ret;
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ret = statfs(TMP, &buf);
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if (ret)
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die("statfs failed: %s\n", strerror(errno));
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if (nosymfollow) {
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if ((buf.f_flags & ST_NOSYMFOLLOW) == 0)
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die("ST_NOSYMFOLLOW not set on %s\n", TMP);
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} else {
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if ((buf.f_flags & ST_NOSYMFOLLOW) != 0)
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die("ST_NOSYMFOLLOW set on %s\n", TMP);
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}
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}
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static void run_tests(bool nosymfollow)
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{
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test_link_traversal(nosymfollow);
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test_readlink();
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test_realpath();
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test_statfs(nosymfollow);
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}
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int main(int argc, char **argv)
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{
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create_and_enter_ns();
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if (mount("testing", TMP, "ramfs", 0, NULL) != 0)
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die("mount failed: %s\n", strerror(errno));
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setup_symlink();
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run_tests(false);
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if (mount("testing", TMP, "ramfs", MS_REMOUNT|MS_NOSYMFOLLOW, NULL) != 0)
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die("remount failed: %s\n", strerror(errno));
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run_tests(true);
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return EXIT_SUCCESS;
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}
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