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 <[email protected]> --- 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 <[email protected]> + * 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 <[email protected]> + * 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 <[email protected]> + * 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
