From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> Test that checks performed by trusted_for(2) on file descriptors are consistent with noexec mount points and file execute permissions, according to the policy configured with the fs.trust_policy sysctl. Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> Reviewed-by: Thibaut Sautereau <thibaut.sautereau@xxxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20211012192410.2356090-4-mic@xxxxxxxxxxx --- Changes since v14: * Add Reviewed-by Kees Cook. Changes since v13: * Move -I to CFLAGS (suggested by Kees Cook). * Update sysctl name. Changes since v12: * Fix Makefile's license. Changes since v10: * Update selftest Makefile. Changes since v9: * Rename the syscall and the sysctl. * Update tests for enum trusted_for_usage Changes since v8: * Update with the dedicated syscall introspect_access(2) and the renamed fs.introspection_policy sysctl. * Remove check symlink which can't be use as is anymore. * Use socketpair(2) to test UNIX socket. Changes since v7: * Update tests with faccessat2/AT_INTERPRETED, including new ones to check that setting R_OK or W_OK returns EINVAL. * Add tests for memfd, pipefs and nsfs. * Rename and move back tests to a standalone directory. Changes since v6: * Add full combination tests for all file types, including block devices, character devices, fifos, sockets and symlinks. * Properly save and restore initial sysctl value for all tests. Changes since v5: * Refactor with FIXTURE_VARIANT, which make the tests much more easy to read and maintain. * Save and restore initial sysctl value (suggested by Kees Cook). * Test with a sysctl value of 0. * Check errno in sysctl_access_write test. * Update tests for the CAP_SYS_ADMIN switch. * Update tests to check -EISDIR (replacing -EACCES). * Replace FIXTURE_DATA() with FIXTURE() (spotted by Kees Cook). * Use global const strings. Changes since v3: * Replace RESOLVE_MAYEXEC with O_MAYEXEC. * Add tests to check that O_MAYEXEC is ignored by open(2) and openat(2). Changes since v2: * Move tests from exec/ to openat2/ . * Replace O_MAYEXEC with RESOLVE_MAYEXEC from openat2(2). * Cleanup tests. Changes since v1: * Move tests from yama/ to exec/ . * Fix _GNU_SOURCE in kselftest_harness.h . * Add a new test sysctl_access_write to check if CAP_MAC_ADMIN is taken into account. * Test directory execution which is always forbidden since commit 73601ea5b7b1 ("fs/open.c: allow opening only regular files during execve()"), and also check that even the root user can not bypass file execution checks. * Make sure delete_workspace() always as enough right to succeed. * Cosmetic cleanup. --- tools/testing/selftests/Makefile | 1 + .../testing/selftests/interpreter/.gitignore | 2 + tools/testing/selftests/interpreter/Makefile | 21 + tools/testing/selftests/interpreter/config | 1 + .../selftests/interpreter/trust_policy_test.c | 362 ++++++++++++++++++ 5 files changed, 387 insertions(+) create mode 100644 tools/testing/selftests/interpreter/.gitignore create mode 100644 tools/testing/selftests/interpreter/Makefile create mode 100644 tools/testing/selftests/interpreter/config create mode 100644 tools/testing/selftests/interpreter/trust_policy_test.c diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile index c852eb40c4f7..3a032a545f74 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -20,6 +20,7 @@ TARGETS += ftrace TARGETS += futex TARGETS += gpio TARGETS += intel_pstate +TARGETS += interpreter TARGETS += ipc TARGETS += ir TARGETS += kcmp diff --git a/tools/testing/selftests/interpreter/.gitignore b/tools/testing/selftests/interpreter/.gitignore new file mode 100644 index 000000000000..82a4846cbc4b --- /dev/null +++ b/tools/testing/selftests/interpreter/.gitignore @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +/*_test diff --git a/tools/testing/selftests/interpreter/Makefile b/tools/testing/selftests/interpreter/Makefile new file mode 100644 index 000000000000..7402fdb6533f --- /dev/null +++ b/tools/testing/selftests/interpreter/Makefile @@ -0,0 +1,21 @@ +# SPDX-License-Identifier: GPL-2.0 + +CFLAGS += -Wall -O2 -I$(khdr_dir) +LDLIBS += -lcap + +src_test := $(wildcard *_test.c) +TEST_GEN_PROGS := $(src_test:.c=) + +KSFT_KHDR_INSTALL := 1 +include ../lib.mk + +khdr_dir = $(top_srcdir)/usr/include + +$(khdr_dir)/asm-generic/unistd.h: khdr + @: + +$(khdr_dir)/linux/trusted-for.h: khdr + @: + +$(OUTPUT)/%_test: %_test.c $(khdr_dir)/asm-generic/unistd.h $(khdr_dir)/linux/trusted-for.h ../kselftest_harness.h + $(LINK.c) $< $(LDLIBS) -o $@ diff --git a/tools/testing/selftests/interpreter/config b/tools/testing/selftests/interpreter/config new file mode 100644 index 000000000000..dd53c266bf52 --- /dev/null +++ b/tools/testing/selftests/interpreter/config @@ -0,0 +1 @@ +CONFIG_SYSCTL=y diff --git a/tools/testing/selftests/interpreter/trust_policy_test.c b/tools/testing/selftests/interpreter/trust_policy_test.c new file mode 100644 index 000000000000..b59f07f537ad --- /dev/null +++ b/tools/testing/selftests/interpreter/trust_policy_test.c @@ -0,0 +1,362 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test trusted_for(2) with fs.trusted_for_policy sysctl + * + * Copyright © 2018-2020 ANSSI + * + * Author: Mickaël Salaün <mic@xxxxxxxxxxx> + */ + +#define _GNU_SOURCE +#include <asm-generic/unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <linux/trusted-for.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/capability.h> +#include <sys/mman.h> +#include <sys/mount.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/syscall.h> +#include <sys/sysmacros.h> +#include <sys/types.h> +#include <unistd.h> + +#include "../kselftest_harness.h" + +#ifndef trusted_for +static int trusted_for(const int fd, const enum trusted_for_usage usage, + const __u32 flags) +{ + errno = 0; + return syscall(__NR_trusted_for, fd, usage, flags); +} +#endif + +static const char sysctl_path[] = "/proc/sys/fs/trusted_for_policy"; + +static const char workdir_path[] = "./test-mount"; +static const char reg_file_path[] = "./test-mount/regular_file"; +static const char dir_path[] = "./test-mount/directory"; +static const char block_dev_path[] = "./test-mount/block_device"; +static const char char_dev_path[] = "./test-mount/character_device"; +static const char fifo_path[] = "./test-mount/fifo"; + +static void ignore_dac(struct __test_metadata *_metadata, int override) +{ + cap_t caps; + const cap_value_t cap_val[2] = { + CAP_DAC_OVERRIDE, + CAP_DAC_READ_SEARCH, + }; + + caps = cap_get_proc(); + ASSERT_NE(NULL, caps); + ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_val, + override ? CAP_SET : CAP_CLEAR)); + ASSERT_EQ(0, cap_set_proc(caps)); + EXPECT_EQ(0, cap_free(caps)); +} + +static void ignore_sys_admin(struct __test_metadata *_metadata, int override) +{ + cap_t caps; + const cap_value_t cap_val[1] = { + CAP_SYS_ADMIN, + }; + + caps = cap_get_proc(); + ASSERT_NE(NULL, caps); + ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_val, + override ? CAP_SET : CAP_CLEAR)); + ASSERT_EQ(0, cap_set_proc(caps)); + EXPECT_EQ(0, cap_free(caps)); +} + +static void test_omx(struct __test_metadata *_metadata, + const char *const path, const int err_access) +{ + int flags = O_RDONLY | O_CLOEXEC; + int fd, access_ret, access_errno; + + /* Do not block on pipes. */ + if (path == fifo_path) + flags |= O_NONBLOCK; + + fd = open(path, flags); + ASSERT_LE(0, fd) { + TH_LOG("Failed to open %s: %s", path, strerror(errno)); + } + access_ret = trusted_for(fd, TRUSTED_FOR_EXECUTION, 0); + access_errno = errno; + if (err_access) { + ASSERT_EQ(err_access, access_errno) { + TH_LOG("Wrong error for trusted_for(2) with %s: %s", + path, strerror(access_errno)); + } + ASSERT_EQ(-1, access_ret); + } else { + ASSERT_EQ(0, access_ret) { + TH_LOG("Access denied for %s: %s", path, strerror(access_errno)); + } + } + + /* Tests unsupported trusted usage. */ + access_ret = trusted_for(fd, 0, 0); + ASSERT_EQ(-1, access_ret); + ASSERT_EQ(EINVAL, errno); + + access_ret = trusted_for(fd, 2, 0); + ASSERT_EQ(-1, access_ret); + ASSERT_EQ(EINVAL, errno); + + EXPECT_EQ(0, close(fd)); +} + +static void test_policy_fd(struct __test_metadata *_metadata, const int fd, + const bool has_policy) +{ + const int ret = trusted_for(fd, TRUSTED_FOR_EXECUTION, 0); + + if (has_policy) { + ASSERT_EQ(-1, ret); + ASSERT_EQ(EACCES, errno) { + TH_LOG("Wrong error for trusted_for(2) with FD: %s", strerror(errno)); + } + } else { + ASSERT_EQ(0, ret) { + TH_LOG("Access denied for FD: %s", strerror(errno)); + } + } +} + +FIXTURE(access) { + char initial_sysctl_value; + int memfd, pipefd; + int pipe_fds[2], socket_fds[2]; +}; + +static void test_file_types(struct __test_metadata *_metadata, FIXTURE_DATA(access) *self, + const int err_code, const bool has_policy) +{ + /* Tests are performed on a tmpfs mount point. */ + test_omx(_metadata, reg_file_path, err_code); + test_omx(_metadata, dir_path, has_policy ? EACCES : 0); + test_omx(_metadata, block_dev_path, has_policy ? EACCES : 0); + test_omx(_metadata, char_dev_path, has_policy ? EACCES : 0); + test_omx(_metadata, fifo_path, has_policy ? EACCES : 0); + + /* Checks that exec is denied for any socket FD. */ + test_policy_fd(_metadata, self->socket_fds[0], has_policy); + + /* Checks that exec is denied for any memfd. */ + test_policy_fd(_metadata, self->memfd, has_policy); + + /* Checks that exec is denied for any pipefs FD. */ + test_policy_fd(_metadata, self->pipefd, has_policy); +} + +static void test_files(struct __test_metadata *_metadata, FIXTURE_DATA(access) *self, + const int err_code, const bool has_policy) +{ + /* Tests as root. */ + ignore_dac(_metadata, 1); + test_file_types(_metadata, self, err_code, has_policy); + + /* Tests without bypass. */ + ignore_dac(_metadata, 0); + test_file_types(_metadata, self, err_code, has_policy); +} + +static void sysctl_write_char(struct __test_metadata *_metadata, const char value) +{ + int fd; + + fd = open(sysctl_path, O_WRONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ASSERT_EQ(1, write(fd, &value, 1)); + EXPECT_EQ(0, close(fd)); +} + +static char sysctl_read_char(struct __test_metadata *_metadata) +{ + int fd; + char sysctl_value; + + fd = open(sysctl_path, O_RDONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ASSERT_EQ(1, read(fd, &sysctl_value, 1)); + EXPECT_EQ(0, close(fd)); + return sysctl_value; +} + +FIXTURE_VARIANT(access) { + const bool mount_exec; + const bool file_exec; + const int sysctl_err_code[3]; +}; + +FIXTURE_VARIANT_ADD(access, mount_exec_file_exec) { + .mount_exec = true, + .file_exec = true, + .sysctl_err_code = {0, 0, 0}, +}; + +FIXTURE_VARIANT_ADD(access, mount_exec_file_noexec) +{ + .mount_exec = true, + .file_exec = false, + .sysctl_err_code = {0, EACCES, EACCES}, +}; + +FIXTURE_VARIANT_ADD(access, mount_noexec_file_exec) +{ + .mount_exec = false, + .file_exec = true, + .sysctl_err_code = {EACCES, 0, EACCES}, +}; + +FIXTURE_VARIANT_ADD(access, mount_noexec_file_noexec) +{ + .mount_exec = false, + .file_exec = false, + .sysctl_err_code = {EACCES, EACCES, EACCES}, +}; + +FIXTURE_SETUP(access) +{ + int procfd_path_size; + static const char path_template[] = "/proc/self/fd/%d"; + char procfd_path[sizeof(path_template) + 10]; + + /* + * Cleans previous workspace if any error previously happened (don't + * check errors). + */ + umount(workdir_path); + rmdir(workdir_path); + + /* Creates a clean mount point. */ + ASSERT_EQ(0, mkdir(workdir_path, 00700)); + ASSERT_EQ(0, mount("test", workdir_path, "tmpfs", MS_MGC_VAL | + (variant->mount_exec ? 0 : MS_NOEXEC), + "mode=0700,size=4k")); + + /* Creates a regular file. */ + ASSERT_EQ(0, mknod(reg_file_path, S_IFREG | (variant->file_exec ? 0500 : 0400), 0)); + /* Creates a directory. */ + ASSERT_EQ(0, mkdir(dir_path, variant->file_exec ? 0500 : 0400)); + /* Creates a character device: /dev/null. */ + ASSERT_EQ(0, mknod(char_dev_path, S_IFCHR | 0400, makedev(1, 3))); + /* Creates a block device: /dev/loop0 */ + ASSERT_EQ(0, mknod(block_dev_path, S_IFBLK | 0400, makedev(7, 0))); + /* Creates a fifo. */ + ASSERT_EQ(0, mknod(fifo_path, S_IFIFO | 0400, 0)); + + /* Creates a regular file without user mount point. */ + self->memfd = memfd_create("test-interpreted", MFD_CLOEXEC); + ASSERT_LE(0, self->memfd); + /* Sets mode, which must be ignored by the exec check. */ + ASSERT_EQ(0, fchmod(self->memfd, variant->file_exec ? 0500 : 0400)); + + /* Creates a pipefs file descriptor. */ + ASSERT_EQ(0, pipe(self->pipe_fds)); + procfd_path_size = snprintf(procfd_path, sizeof(procfd_path), + path_template, self->pipe_fds[0]); + ASSERT_LT(procfd_path_size, sizeof(procfd_path)); + self->pipefd = open(procfd_path, O_RDONLY | O_CLOEXEC); + ASSERT_LE(0, self->pipefd); + ASSERT_EQ(0, fchmod(self->pipefd, variant->file_exec ? 0500 : 0400)); + + /* Creates a socket file descriptor. */ + ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0, self->socket_fds)); + + /* Saves initial sysctl value. */ + self->initial_sysctl_value = sysctl_read_char(_metadata); + + /* Prepares for sysctl writes. */ + ignore_sys_admin(_metadata, 1); +} + +FIXTURE_TEARDOWN(access) +{ + EXPECT_EQ(0, close(self->memfd)); + EXPECT_EQ(0, close(self->pipefd)); + EXPECT_EQ(0, close(self->pipe_fds[0])); + EXPECT_EQ(0, close(self->pipe_fds[1])); + EXPECT_EQ(0, close(self->socket_fds[0])); + EXPECT_EQ(0, close(self->socket_fds[1])); + + /* Restores initial sysctl value. */ + sysctl_write_char(_metadata, self->initial_sysctl_value); + + /* There is no need to unlink the test files. */ + ASSERT_EQ(0, umount(workdir_path)); + ASSERT_EQ(0, rmdir(workdir_path)); +} + +TEST_F(access, sysctl_0) +{ + /* Do not enforce anything. */ + sysctl_write_char(_metadata, '0'); + test_files(_metadata, self, 0, false); +} + +TEST_F(access, sysctl_1) +{ + /* Enforces mount exec check. */ + sysctl_write_char(_metadata, '1'); + test_files(_metadata, self, variant->sysctl_err_code[0], true); +} + +TEST_F(access, sysctl_2) +{ + /* Enforces file exec check. */ + sysctl_write_char(_metadata, '2'); + test_files(_metadata, self, variant->sysctl_err_code[1], true); +} + +TEST_F(access, sysctl_3) +{ + /* Enforces mount and file exec check. */ + sysctl_write_char(_metadata, '3'); + test_files(_metadata, self, variant->sysctl_err_code[2], true); +} + +FIXTURE(cleanup) { + char initial_sysctl_value; +}; + +FIXTURE_SETUP(cleanup) +{ + /* Saves initial sysctl value. */ + self->initial_sysctl_value = sysctl_read_char(_metadata); +} + +FIXTURE_TEARDOWN(cleanup) +{ + /* Restores initial sysctl value. */ + ignore_sys_admin(_metadata, 1); + sysctl_write_char(_metadata, self->initial_sysctl_value); +} + +TEST_F(cleanup, sysctl_access_write) +{ + int fd; + ssize_t ret; + + ignore_sys_admin(_metadata, 1); + sysctl_write_char(_metadata, '0'); + + ignore_sys_admin(_metadata, 0); + fd = open(sysctl_path, O_WRONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ret = write(fd, "0", 1); + ASSERT_EQ(-1, ret); + ASSERT_EQ(EPERM, errno); + EXPECT_EQ(0, close(fd)); +} + +TEST_HARNESS_MAIN -- 2.32.0
