Test all of the various resolveat(2) flags, as well as how file
descriptor re-opening works. A small stress-test of a symlink-rename
attack is included to show that the protections against ".."-based
attacks are sufficient.
Signed-off-by: Aleksa Sarai <cyphar@xxxxxxxxxx>
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/resolveat/.gitignore | 1 +
tools/testing/selftests/resolveat/Makefile | 6 +
tools/testing/selftests/resolveat/helpers.h | 195 +++++++++
.../selftests/resolveat/linkmode_test.c | 306 ++++++++++++++
.../selftests/resolveat/resolveat_test.c | 400 ++++++++++++++++++
6 files changed, 909 insertions(+)
create mode 100644 tools/testing/selftests/resolveat/.gitignore
create mode 100644 tools/testing/selftests/resolveat/Makefile
create mode 100644 tools/testing/selftests/resolveat/helpers.h
create mode 100644 tools/testing/selftests/resolveat/linkmode_test.c
create mode 100644 tools/testing/selftests/resolveat/resolveat_test.c
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 971fc8428117..f558d6f21c4b 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -37,6 +37,7 @@ TARGETS += powerpc
TARGETS += proc
TARGETS += pstore
TARGETS += ptrace
+TARGETS += resolveat
TARGETS += rseq
TARGETS += rtc
TARGETS += seccomp
diff --git a/tools/testing/selftests/resolveat/.gitignore b/tools/testing/selftests/resolveat/.gitignore
new file mode 100644
index 000000000000..bd68f6c3fd07
--- /dev/null
+++ b/tools/testing/selftests/resolveat/.gitignore
@@ -0,0 +1 @@
+/*_test
diff --git a/tools/testing/selftests/resolveat/Makefile b/tools/testing/selftests/resolveat/Makefile
new file mode 100644
index 000000000000..375eaf4a55e7
--- /dev/null
+++ b/tools/testing/selftests/resolveat/Makefile
@@ -0,0 +1,6 @@
+CFLAGS += -g -I../../../../usr/include/
+
+TEST_GEN_PROGS := linkmode_test resolveat_test
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/resolveat/helpers.h b/tools/testing/selftests/resolveat/helpers.h
new file mode 100644
index 000000000000..c765f606cdbc
--- /dev/null
+++ b/tools/testing/selftests/resolveat/helpers.h
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@xxxxxxxxxx>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#ifndef __RESOLVEAT_H__
+#define __RESOLVEAT_H__
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <syscall.h>
+#include <limits.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+
+#define ARRAY_LEN(X) (sizeof (X) / sizeof (*(X)))
+
+#ifndef __NR_resolveat
+#define __NR_resolveat 435
+#define RESOLVE_UPGRADE_NOWRITE 0x002 /* Disallow re-opening for write. */
+#define RESOLVE_UPGRADE_NOREAD 0x004 /* Disallow re-opening for read. */
+#define RESOLVE_NO_FOLLOW 0x008 /* Don't follow trailing symlinks. */
+#define RESOLVE_BENEATH 0x010 /* Block "lexical" trickery like "..", symlinks, absolute paths, etc. */
+#define RESOLVE_XDEV 0x020 /* Block mount-point crossings (includes bind-mounts). */
+#define RESOLVE_NO_MAGICLINKS 0x040 /* Block procfs-style "magic" symlinks. */
+#define RESOLVE_NO_SYMLINKS 0x080 /* Block all symlinks (implies AT_NO_MAGICLINKS). */
+#define RESOLVE_IN_ROOT 0x100 /* Scope ".." and "/" resolution to dirfd (like chroot(2)). */
+#endif /* __NR_resolveat */
+
+#ifndef O_EMPTYPATH
+#define O_EMPTYPATH 040000000
+#endif /* O_EMPTYPATH */
+
+#define E_func(func, ...) \
+ do { \
+ if (func(__VA_ARGS__) < 0) \
+ ksft_exit_fail_msg("%s:%d %s failed\n", \
+ __FILE__, __LINE__, #func);\
+ } while (0)
+
+#define E_mkdirat(...) E_func(mkdirat, __VA_ARGS__)
+#define E_symlinkat(...) E_func(symlinkat, __VA_ARGS__)
+#define E_touchat(...) E_func(touchat, __VA_ARGS__)
+#define E_readlink(...) E_func(readlink, __VA_ARGS__)
+#define E_fstatat(...) E_func(fstatat, __VA_ARGS__)
+#define E_asprintf(...) E_func(asprintf, __VA_ARGS__)
+#define E_fchdir(...) E_func(fchdir, __VA_ARGS__)
+#define E_mount(...) E_func(mount, __VA_ARGS__)
+#define E_unshare(...) E_func(unshare, __VA_ARGS__)
+#define E_setresuid(...) E_func(setresuid, __VA_ARGS__)
+#define E_chmod(...) E_func(chmod, __VA_ARGS__)
+
+#define E_assert(expr, msg, ...) \
+ do { \
+ if (!(expr)) \
+ ksft_exit_fail_msg("ASSERT(%s:%d) failed (%s): " msg "\n", \
+ __FILE__, __LINE__, #expr, ##__VA_ARGS__); \
+ } while (0)
+
+typedef int (*openfunc_t)(int dfd, const char *path, unsigned int flags);
+
+static int sys_resolveat(int dfd, const char *path, unsigned int flags)
+{
+ int ret = syscall(__NR_resolveat, dfd, path, flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+static int sys_openat(int dfd, const char *path, unsigned int flags)
+{
+ int ret = openat(dfd, path, flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+static int sys_execveat(int dfd, const char *path,
+ char *const argv[], char *const envp[], int flags)
+{
+ int ret = syscall(SYS_execveat, dfd, path, argv, envp, flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+static char *resolveat_flags(unsigned int flags)
+{
+ char *flagset, *p;
+
+ E_asprintf(&flagset, "%s%s%s%s%s%s%s%s0",
+ (flags & RESOLVE_UPGRADE_NOWRITE) ? "RESOLVE_UPGRADE_NOWRITE|" : "",
+ (flags & RESOLVE_UPGRADE_NOREAD) ? "RESOLVE_UPGRADE_NOREAD|" : "",
+ (flags & RESOLVE_NO_FOLLOW) ? "RESOLVE_NO_FOLLOW|" : "",
+ (flags & RESOLVE_BENEATH) ? "RESOLVE_BENEATH|" : "",
+ (flags & RESOLVE_XDEV) ? "RESOLVE_XDEV|" : "",
+ (flags & RESOLVE_NO_MAGICLINKS) ? "RESOLVE_NO_MAGICLINKS|" : "",
+ (flags & RESOLVE_NO_SYMLINKS) ? "RESOLVE_NO_SYMLINKS|" : "",
+ (flags & RESOLVE_IN_ROOT) ? "RESOLVE_IN_ROOT|" : "");
+
+ /* Fix up the trailing |0. */
+ p = strstr(flagset, "|0");
+ if (p)
+ *p = '\0';
+ return flagset;
+}
+
+static char *openat_flags(unsigned int flags)
+{
+ char *flagset;
+ const char *modeflag = "(none)";
+
+ /* Handle the peculiarity of the ACC_MODE flags. */
+ switch (flags & 0x03) {
+ case O_RDWR:
+ modeflag = "O_RDWR";
+ break;
+ case O_RDONLY:
+ modeflag = "O_RDONLY";
+ break;
+ case O_WRONLY:
+ modeflag = "O_WRONLY";
+ break;
+ }
+
+ /* TODO: Add more open flags. */
+ E_asprintf(&flagset, "%s", modeflag);
+ return flagset;
+}
+
+static int touchat(int dfd, const char *path)
+{
+ int fd = openat(dfd, path, O_CREAT);
+ if (fd >= 0)
+ close(fd);
+ return fd;
+}
+
+static char *fdreadlink(int fd)
+{
+ char *target, *tmp;
+
+ E_asprintf(&tmp, "/proc/self/fd/%d", fd);
+
+ target = malloc(PATH_MAX);
+ if (!target)
+ ksft_exit_fail_msg("fdreadlink: malloc failed\n");
+ memset(target, 0, PATH_MAX);
+
+ E_readlink(tmp, target, PATH_MAX);
+ free(tmp);
+ return target;
+}
+
+static bool fdequal(int fd, int dfd, const char *path)
+{
+ char *fdpath, *dfdpath, *other;
+ bool cmp;
+
+ fdpath = fdreadlink(fd);
+ dfdpath = fdreadlink(dfd);
+
+ if (!path)
+ E_asprintf(&other, "%s", dfdpath);
+ else if (*path == '/')
+ E_asprintf(&other, "%s", path);
+ else
+ E_asprintf(&other, "%s/%s", dfdpath, path);
+
+ cmp = !strcmp(fdpath, other);
+ if (!cmp)
+ ksft_print_msg("fdequal: expected '%s' but got '%s'\n", other, fdpath);
+
+ free(fdpath);
+ free(dfdpath);
+ free(other);
+ return cmp;
+}
+
+static void test_resolveat_supported(void)
+{
+ int fd = sys_resolveat(AT_FDCWD, ".", 0);
+ if (fd == -ENOSYS)
+ ksft_exit_skip("resolveat(2) unsupported on this kernel\n");
+ if (fd < 0)
+ ksft_exit_fail_msg("resolveat(2) supported check failed: %s\n", strerror(-fd));
+ close(fd);
+}
+
+#endif /* __RESOLVEAT_H__ */
diff --git a/tools/testing/selftests/resolveat/linkmode_test.c b/tools/testing/selftests/resolveat/linkmode_test.c
new file mode 100644
index 000000000000..b60375099494
--- /dev/null
+++ b/tools/testing/selftests/resolveat/linkmode_test.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@xxxxxxxxxx>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <libgen.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <syscall.h>
+#include <limits.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+#include "helpers.h"
+
+static mode_t fdmode(int fd)
+{
+ char *fdpath;
+ struct stat statbuf;
+ mode_t mode;
+
+ E_asprintf(&fdpath, "/proc/self/fd/%d", fd);
+ E_fstatat(AT_FDCWD, fdpath, &statbuf, AT_SYMLINK_NOFOLLOW);
+ mode = (statbuf.st_mode & ~S_IFMT);
+ free(fdpath);
+
+ return mode;
+}
+
+static int reopen_proc(int fd, unsigned int flags)
+{
+ int ret, saved_errno;
+ char *fdpath;
+
+ E_asprintf(&fdpath, "/proc/self/fd/%d", fd);
+ ret = open(fdpath, flags);
+ saved_errno = errno;
+ free(fdpath);
+
+ return ret >= 0 ? ret : -saved_errno;
+}
+
+static int reopen_oemptypath(int fd, unsigned int flags)
+{
+ int ret = openat(fd, "", O_EMPTYPATH | flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+struct reopen_test {
+ openfunc_t open;
+ mode_t chmod_mode;
+ struct {
+ unsigned int flags;
+ mode_t mode;
+ int err;
+ } orig, new;
+};
+
+static bool reopen(int fd, struct reopen_test *test)
+{
+ int newfd;
+ mode_t proc_mode;
+ bool failed = false;
+
+ /* Check that the proc mode is correct. */
+ proc_mode = fdmode(fd);
+ if (proc_mode != test->orig.mode) {
+ ksft_print_msg("incorrect fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->orig.mode);
+ failed = true;
+ }
+
+ /* Re-open through /proc. */
+ newfd = reopen_proc(fd, test->new.flags);
+ if (newfd != test->new.err && (newfd < 0 || test->new.err < 0)) {
+ ksft_print_msg("/proc failure (%d != %d [%s])\n",
+ newfd, test->new.err, strerror(-test->new.err));
+ failed = true;
+ }
+ if (newfd >= 0) {
+ proc_mode = fdmode(newfd);
+ if (proc_mode != test->new.mode) {
+ ksft_print_msg("/proc wrong fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->new.mode);
+ failed = true;
+ }
+ close(newfd);
+ }
+
+ /* Re-open with O_EMPTYPATH. */
+ newfd = reopen_oemptypath(fd, test->new.flags);
+ if (newfd != test->new.err && (newfd < 0 || test->new.err < 0)) {
+ ksft_print_msg("O_EMPTYPATH failure (%d != %d [%s])\n",
+ newfd, test->new.err, strerror(-test->new.err));
+ failed = true;
+ }
+ if (newfd >= 0) {
+ proc_mode = fdmode(newfd);
+ if (proc_mode != test->new.mode) {
+ ksft_print_msg("O_EMPTYPATH wrong fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->new.mode);
+ failed = true;
+ }
+ close(newfd);
+ }
+
+ return failed;
+}
+
+void test_reopen_ordinary(bool privileged)
+{
+ int fd;
+ int err_access = privileged ? 0 : -EACCES;
+ char tmpfile[] = "/tmp/reopen-testfile.XXXXXX";
+
+ fd = mkstemp(tmpfile);
+ E_assert(fd >= 0, "mkstemp failed: %m\n");
+ close(fd);
+
+ struct reopen_test tests[] = {
+ /* Re-opening with the same mode should succeed. */
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.flags = O_RDONLY, .orig.mode = privileged ? 0777 : 0555,
+ .new.flags = O_RDONLY, .new.mode = privileged ? 0777 : 0555},
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.flags = O_WRONLY, .orig.mode = privileged ? 0777 : 0333,
+ .new.flags = O_WRONLY, .new.mode = privileged ? 0777 : 0333 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_RDWR, .orig.mode = 0777,
+ .new.flags = O_RDWR, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_RDWR, .orig.mode = 0777,
+ .new.flags = O_RDONLY, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_RDWR, .orig.mode = 0777,
+ .new.flags = O_WRONLY, .new.mode = 0777 },
+
+ /*
+ * Upgrading the mode of a normal file works if the user had the
+ * required access at original-open time.
+ */
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_RDONLY, .orig.mode = 0777,
+ .new.flags = O_WRONLY, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_WRONLY, .orig.mode = 0777,
+ .new.flags = O_RDONLY, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_RDONLY, .orig.mode = 0777,
+ .new.flags = O_RDWR, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.flags = O_WRONLY, .orig.mode = 0777,
+ .new.flags = O_RDWR, .new.mode = 0777 },
+
+ /* However, re-open will be blocked given insufficient permissions. */
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.flags = O_RDONLY, .orig.mode = privileged ? 0777 : 0555,
+ .new.flags = O_WRONLY, .new.mode = 0777, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.flags = O_WRONLY, .orig.mode = privileged ? 0777 : 0333,
+ .new.flags = O_RDONLY, .new.mode = 0777, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.flags = O_RDONLY, .orig.mode = privileged ? 0777 : 0555,
+ .new.flags = O_RDWR, .new.mode = 0777, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.flags = O_WRONLY, .orig.mode = privileged ? 0777 : 0333,
+ .new.flags = O_RDWR, .new.mode = 0777, .new.err = err_access },
+
+ /* O_PATH re-opens (of ordinary files) will always work. */
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.flags = O_PATH, .orig.mode = 0777,
+ .new.flags = O_WRONLY, .new.mode = 0777 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = 0, .orig.mode = 0777,
+ .new.flags = O_WRONLY, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.flags = O_PATH, .orig.mode = 0777,
+ .new.flags = O_RDONLY, .new.mode = 0777 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = 0, .orig.mode = 0777,
+ .new.flags = O_RDONLY, .new.mode = 0777 },
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.flags = O_PATH, .orig.mode = 0777,
+ .new.flags = O_RDWR, .new.mode = 0777 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = 0, .orig.mode = 0777,
+ .new.flags = O_RDWR, .new.mode = 0777 },
+
+ /*
+ * resolveat(2) RESOLVE_UPGRADE_NO* flags. In the privileged case, the
+ * re-open will work but the mode will still be scoped to the mode
+ * (or'd with the open acc_mode).
+ */
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOREAD | RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0111,
+ .new.flags = O_RDONLY, .new.mode = 0555, .new.err = err_access },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOREAD | RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0111,
+ .new.flags = O_WRONLY, .new.mode = 0333, .new.err = err_access },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOREAD | RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0111,
+ .new.flags = O_RDWR, .new.mode = 0777, .new.err = err_access },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0555,
+ .new.flags = O_RDONLY, .new.mode = 0555 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOREAD,
+ .orig.mode = 0333,
+ .new.flags = O_WRONLY, .new.mode = 0333 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0555,
+ .new.flags = O_RDONLY, .new.mode = 0555 },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOREAD,
+ .orig.mode = 0333,
+ .new.flags = O_RDONLY, .new.mode = 0777, .new.err = err_access },
+ { .open = sys_resolveat, .chmod_mode = 0000,
+ .orig.flags = RESOLVE_UPGRADE_NOWRITE,
+ .orig.mode = 0555,
+ .new.flags = O_WRONLY, .new.mode = 0777, .new.err = err_access },
+ };
+
+ for (int i = 0; i < ARRAY_LEN(tests); i++) {
+ int fd;
+ char *orig_flagset, *new_flagset;
+ struct reopen_test *test = &tests[i];
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+
+ E_chmod(tmpfile, test->chmod_mode);
+
+ fd = test->open(AT_FDCWD, tmpfile, test->orig.flags);
+ E_assert(fd >= 0, "open '%s' failed: %m\n", tmpfile);
+
+ /* Make sure that any EACCES we see is not from inode permissions. */
+ E_chmod(tmpfile, 0777);
+
+ if (reopen(fd, test))
+ resultfn = ksft_test_result_fail;
+
+ close(fd);
+
+ new_flagset = openat_flags(test->new.flags);
+ if (test->open == sys_openat)
+ orig_flagset = openat_flags(test->orig.flags);
+ else if (test->open == sys_resolveat)
+ orig_flagset = resolveat_flags(test->orig.flags);
+ else
+ ksft_exit_fail_msg("unknown test->open\n");
+
+ resultfn("%sordinary reopen of (orig[%s]=%s, new=%s) chmod=%.3o %s\n",
+ privileged ? "privileged " : "",
+ test->open == sys_openat ? "openat" : "resolveat",
+ orig_flagset, new_flagset, test->chmod_mode,
+ test->new.err < 0 ? strerror(-test->new.err) : "works");
+
+ free(new_flagset);
+ free(orig_flagset);
+ }
+
+ unlink(tmpfile);
+}
+
+
+int main(int argc, char **argv)
+{
+ bool privileged;
+
+ ksft_print_header();
+ test_resolveat_supported();
+
+ /*
+ * Technically we should be checking CAP_DAC_OVERRIDE, but it's easier to
+ * just assume that euid=0 has the full capability set.
+ */
+ privileged = (geteuid() == 0);
+ if (!privileged)
+ ksft_test_result_skip("privileged tests require euid == 0\n");
+ else {
+ test_reopen_ordinary(privileged);
+
+ E_setresuid(65534, 65534, 65534);
+ privileged = (geteuid() == 0);
+ }
+
+ test_reopen_ordinary(privileged);
+
+ if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+ ksft_exit_fail();
+ else
+ ksft_exit_pass();
+}
diff --git a/tools/testing/selftests/resolveat/resolveat_test.c b/tools/testing/selftests/resolveat/resolveat_test.c
new file mode 100644
index 000000000000..72f2e8c5dfe0
--- /dev/null
+++ b/tools/testing/selftests/resolveat/resolveat_test.c
@@ -0,0 +1,400 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@xxxxxxxxxx>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <libgen.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/mman.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <syscall.h>
+#include <limits.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+#include "helpers.h"
+
+/*
+ * Construct a test directory with the following structure:
+ *
+ * root/
+ * |-- procexe -> /proc/self/exe
+ * |-- procroot -> /proc/self/root
+ * |-- root/
+ * |-- mnt/ [mountpoint]
+ * | |-- self -> ../mnt/
+ * | `-- absself -> /mnt/
+ * |-- etc/
+ * | `-- passwd
+ * |-- relsym -> etc/passwd
+ * |-- abssym -> /etc/passwd
+ * |-- abscheeky -> /cheeky
+ * |-- abscheeky -> /cheeky
+ * `-- cheeky/
+ * |-- absself -> /
+ * |-- self -> ../../root/
+ * |-- garbageself -> /../../root/
+ * |-- passwd -> ../cheeky/../cheeky/../etc/../etc/passwd
+ * |-- abspasswd -> /../cheeky/../cheeky/../etc/../etc/passwd
+ * |-- dotdotlink -> ../../../../../../../../../../../../../../etc/passwd
+ * `-- garbagelink -> /../../../../../../../../../../../../../../etc/passwd
+ */
+int setup_testdir(void)
+{
+ int dfd, tmpfd;
+ char dirname[] = "/tmp/resolveat-testdir.XXXXXX";
+
+ /* Unshare and make /tmp a new directory. */
+ E_unshare(CLONE_NEWNS);
+ E_mount("", "/tmp", "", MS_PRIVATE, "");
+
+ /* Make the top-level directory. */
+ if (!mkdtemp(dirname))
+ ksft_exit_fail_msg("setup_testdir: failed to create tmpdir\n");
+ dfd = open(dirname, O_PATH | O_DIRECTORY);
+ if (dfd < 0)
+ ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+
+ /* A sub-directory which is actually used for tests. */
+ E_mkdirat(dfd, "root", 0755);
+ tmpfd = openat(dfd, "root", O_PATH | O_DIRECTORY);
+ if (tmpfd < 0)
+ ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+ close(dfd);
+ dfd = tmpfd;
+
+ E_symlinkat("/proc/self/exe", dfd, "procexe");
+ E_symlinkat("/proc/self/root", dfd, "procroot");
+ E_mkdirat(dfd, "root", 0755);
+
+ /* There is no mountat(2), so use chdir. */
+ E_mkdirat(dfd, "mnt", 0755);
+ E_fchdir(dfd);
+ E_mount("tmpfs", "./mnt", "tmpfs", MS_NOSUID | MS_NODEV, "");
+ E_symlinkat("../mnt/", dfd, "mnt/self");
+ E_symlinkat("/mnt/", dfd, "mnt/absself");
+
+ E_mkdirat(dfd, "etc", 0755);
+ E_touchat(dfd, "etc/passwd");
+
+ E_symlinkat("etc/passwd", dfd, "relsym");
+ E_symlinkat("/etc/passwd", dfd, "abssym");
+ E_symlinkat("/cheeky", dfd, "abscheeky");
+
+ E_mkdirat(dfd, "cheeky", 0755);
+
+ E_symlinkat("/", dfd, "cheeky/absself");
+ E_symlinkat("../../root/", dfd, "cheeky/self");
+ E_symlinkat("/../../root/", dfd, "cheeky/garbageself");
+
+ E_symlinkat("../cheeky/../etc/../etc/passwd", dfd, "cheeky/passwd");
+ E_symlinkat("/../cheeky/../etc/../etc/passwd", dfd, "cheeky/abspasswd");
+
+ E_symlinkat("../../../../../../../../../../../../../../etc/passwd",
+ dfd, "cheeky/dotdotlink");
+ E_symlinkat("/../../../../../../../../../../../../../../etc/passwd",
+ dfd, "cheeky/garbagelink");
+
+ return dfd;
+}
+
+struct basic_test {
+ const char *dir;
+ const char *path;
+ unsigned int flags;
+ bool pass;
+ union {
+ int err;
+ const char *path;
+ } out;
+};
+
+void test_resolveat_basic_tests(void)
+{
+ int rootfd;
+ char *procselfexe;
+
+ E_asprintf(&procselfexe, "/proc/%d/exe", getpid());
+ rootfd = setup_testdir();
+
+ struct basic_test tests[] = {
+ /** RESOLVE_BENEATH **/
+ /* Attempts to cross dirfd should be blocked. */
+ { .path = "/", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/absself", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/absself", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "..", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "../root/", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/self", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/self", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/garbageself", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/garbageself", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ /* Only relative paths that stay inside dirfd should work. */
+ { .path = "root", .flags = RESOLVE_BENEATH,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .flags = RESOLVE_BENEATH,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .flags = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "relsym", .flags = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/passwd", .flags = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/passwd", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abssym", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "/etc/passwd", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/abspasswd", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/abspasswd", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ /* Tricky paths should fail. */
+ { .path = "cheeky/dotdotlink", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/dotdotlink", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/garbagelink", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/garbagelink", .flags = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+
+ /** RESOLVE_IN_ROOT **/
+ /* All attempts to cross the dirfd will be scoped-to-root. */
+ { .path = "/", .flags = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "cheeky/absself", .flags = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "abscheeky/absself", .flags = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "..", .flags = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "../root/", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "../root/", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "cheeky/self", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "cheeky/garbageself", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "abscheeky/garbageself", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "root", .flags = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "relsym", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/passwd", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/passwd", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abssym", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/etc/passwd", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/abspasswd", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/abspasswd",.flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/dotdotlink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/dotdotlink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/../../../../abscheeky/dotdotlink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/garbagelink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/garbagelink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/../../../../abscheeky/garbagelink", .flags = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+
+ /** RESOLVE_XDEV **/
+ /* Crossing *down* into a mountpoint is disallowed. */
+ { .path = "mnt", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "mnt/", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "mnt/.", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ /* Crossing *up* out of a mountpoint is disallowed. */
+ { .dir = "mnt", .path = ".", .flags = RESOLVE_XDEV,
+ .out.path = "mnt", .pass = true },
+ { .dir = "mnt", .path = "..", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "../mnt", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "self", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "absself", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ /* Jumping to "/" is ok, but later components cannot cross. */
+ { .dir = "mnt", .path = "/", .flags = RESOLVE_XDEV,
+ .out.path = "/", .pass = true },
+ { .dir = "/", .path = "/", .flags = RESOLVE_XDEV,
+ .out.path = "/", .pass = true },
+ { .path = "/proc/1", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "/tmp", .flags = RESOLVE_XDEV,
+ .out.err = -EXDEV, .pass = false },
+
+ /** RESOLVE_NO_MAGICLINKS **/
+ /* Regular symlinks should work. */
+ { .path = "relsym", .flags = RESOLVE_NO_MAGICLINKS,
+ .out.path = "etc/passwd", .pass = true },
+ /* Magic-links should not work. */
+ { .path = "procexe", .flags = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/exe", .flags = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "procroot/etc", .flags = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/root/etc", .flags = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/root/etc", .flags = RESOLVE_NO_MAGICLINKS | RESOLVE_NO_FOLLOW,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/exe", .flags = RESOLVE_NO_MAGICLINKS | RESOLVE_NO_FOLLOW,
+ .out.path = procselfexe, .pass = true },
+
+ /** RESOLVE_NO_SYMLINKS **/
+ /* Normal paths should work. */
+ { .path = ".", .flags = RESOLVE_NO_SYMLINKS,
+ .out.path = NULL, .pass = true },
+ { .path = "root", .flags = RESOLVE_NO_SYMLINKS,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .flags = RESOLVE_NO_SYMLINKS,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .flags = RESOLVE_NO_SYMLINKS,
+ .out.path = "etc/passwd", .pass = true },
+ /* Regular symlinks are blocked. */
+ { .path = "relsym", .flags = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abssym", .flags = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "cheeky/garbagelink", .flags = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/garbagelink", .flags = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/absself", .flags = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ /* Trailing symlinks with NO_FOLLOW. */
+ { .path = "relsym", .flags = RESOLVE_NO_SYMLINKS | RESOLVE_NO_FOLLOW,
+ .out.path = "relsym", .pass = true },
+ { .path = "abssym", .flags = RESOLVE_NO_SYMLINKS | RESOLVE_NO_FOLLOW,
+ .out.path = "abssym", .pass = true },
+ { .path = "cheeky/garbagelink", .flags = RESOLVE_NO_SYMLINKS | RESOLVE_NO_FOLLOW,
+ .out.path = "cheeky/garbagelink", .pass = true },
+ { .path = "abscheeky/garbagelink", .flags = RESOLVE_NO_SYMLINKS | RESOLVE_NO_FOLLOW,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/absself", .flags = RESOLVE_NO_SYMLINKS | RESOLVE_NO_FOLLOW,
+ .out.err = -ELOOP, .pass = false },
+ };
+
+ for (int i = 0; i < ARRAY_LEN(tests); i++) {
+ int dfd, fd;
+ bool failed;
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+
+ struct basic_test *test = &tests[i];
+ char *flagstr = resolveat_flags(test->flags);
+
+ if (test->dir)
+ dfd = openat(rootfd, test->dir, O_PATH | O_DIRECTORY);
+ else
+ dfd = dup(rootfd);
+ if (dfd < 0) {
+ resultfn = ksft_test_result_error;
+ goto next;
+ }
+
+ fd = sys_resolveat(dfd, test->path, test->flags);
+ if (test->pass)
+ failed = (fd < 0 || !fdequal(fd, rootfd, test->out.path));
+ else
+ failed = (fd != test->out.err);
+ if (fd >= 0)
+ close(fd);
+ close(dfd);
+
+ if (failed)
+ resultfn = ksft_test_result_fail;
+
+next:
+ if (test->pass)
+ resultfn("resolveat(root[%s], %s, %s) ==> %s\n",
+ test->dir ?: ".", test->path, flagstr,
+ test->out.path ?: ".");
+ else
+ resultfn("resolveat(root[%s], %s, %s) ==> %d (%s)\n",
+ test->dir ?: ".", test->path, flagstr,
+ test->out.err, strerror(-test->out.err));
+ free(flagstr);
+ }
+
+ free(procselfexe);
+ close(rootfd);
+}
+
+
+static int proc_exec(int fd)
+{
+ int err, saved_errno;
+ char *procpath;
+ char *argv[] = {"foo", NULL};
+ char *envp[] = {"bar", NULL};
+
+ E_asprintf(&procpath, "/proc/self/fd/%d", fd);
+ err = execve(procpath, argv, envp);
+ saved_errno = errno;
+ free(procpath);
+
+ return err >= 0 ? err : -saved_errno;
+}
+
+static int fd_exec(int fd)
+{
+ char *argv[] = {"foo", NULL};
+ char *envp[] = {"bar", NULL};
+
+ return sys_execveat(fd, "", argv, envp, AT_EMPTY_PATH);
+}
+
+int main(int argc, char **argv)
+{
+ ksft_print_header();
+ test_resolveat_supported();
+
+ /* NOTE: We should be checking for CAP_SYS_ADMIN here... */
+ if (geteuid() != 0)
+ ksft_exit_skip("resolveat(2) tests require euid == 0\n");
+
+ test_resolveat_basic_tests();
+
+ if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+ ksft_exit_fail();
+ else
+ ksft_exit_pass();
+}
--
2.21.0
