From: Mickaël Salaün Date: Wed, 8 Jan 2025 15:43:30 +0000 (+0100) Subject: selftests/landlock: Add layout1.umount_sandboxer tests X-Git-Tag: v6.14-rc1~138^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2a794ee613617b5d8fd978b7ef08d64aa07ff2e6;p=thirdparty%2Flinux.git selftests/landlock: Add layout1.umount_sandboxer tests Check that a domain is not tied to the executable file that created it. For instance, that could happen if a Landlock domain took a reference to a struct path. Move global path names to common.h and replace copy_binary() with a more generic copy_file() helper. Test coverage for security/landlock is 92.7% of 1133 lines according to gcc/gcov-14. Cc: Günther Noack Link: https://lore.kernel.org/r/20250108154338.1129069-23-mic@digikod.net [mic: Update date and add test coverage] Signed-off-by: Mickaël Salaün --- diff --git a/tools/testing/selftests/landlock/Makefile b/tools/testing/selftests/landlock/Makefile index 480f13e77fcc4..5cb0828f05141 100644 --- a/tools/testing/selftests/landlock/Makefile +++ b/tools/testing/selftests/landlock/Makefile @@ -10,7 +10,7 @@ src_test := $(wildcard *_test.c) TEST_GEN_PROGS := $(src_test:.c=) -TEST_GEN_PROGS_EXTENDED := true +TEST_GEN_PROGS_EXTENDED := true sandbox-and-launch wait-pipe # Short targets: $(TEST_GEN_PROGS): LDLIBS += -lcap -lpthread diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h index 8391ab574f641..a604ea5d8297c 100644 --- a/tools/testing/selftests/landlock/common.h +++ b/tools/testing/selftests/landlock/common.h @@ -28,6 +28,9 @@ /* TEST_F_FORK() should not be used for new tests. */ #define TEST_F_FORK(fixture_name, test_name) TEST_F(fixture_name, test_name) +static const char bin_sandbox_and_launch[] = "./sandbox-and-launch"; +static const char bin_wait_pipe[] = "./wait-pipe"; + static void _init_caps(struct __test_metadata *const _metadata, bool drop_all) { cap_t cap_p; diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index a359c0d3107f2..8ac9aaf38eaa8 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -59,7 +59,7 @@ int open_tree(int dfd, const char *filename, unsigned int flags) #define RENAME_EXCHANGE (1 << 1) #endif -#define BINARY_PATH "./true" +static const char bin_true[] = "./true"; /* Paths (sibling number and depth) */ static const char dir_s1d1[] = TMP_DIR "/s1d1"; @@ -1965,8 +1965,8 @@ TEST_F_FORK(layout1, relative_chroot_chdir) test_relative_path(_metadata, REL_CHROOT_CHDIR); } -static void copy_binary(struct __test_metadata *const _metadata, - const char *const dst_path) +static void copy_file(struct __test_metadata *const _metadata, + const char *const src_path, const char *const dst_path) { int dst_fd, src_fd; struct stat statbuf; @@ -1976,11 +1976,10 @@ static void copy_binary(struct __test_metadata *const _metadata, { TH_LOG("Failed to open \"%s\": %s", dst_path, strerror(errno)); } - src_fd = open(BINARY_PATH, O_RDONLY | O_CLOEXEC); + src_fd = open(src_path, O_RDONLY | O_CLOEXEC); ASSERT_LE(0, src_fd) { - TH_LOG("Failed to open \"" BINARY_PATH "\": %s", - strerror(errno)); + TH_LOG("Failed to open \"%s\": %s", src_path, strerror(errno)); } ASSERT_EQ(0, fstat(src_fd, &statbuf)); ASSERT_EQ(statbuf.st_size, @@ -2028,9 +2027,9 @@ TEST_F_FORK(layout1, execute) create_ruleset(_metadata, rules[0].access, rules); ASSERT_LE(0, ruleset_fd); - copy_binary(_metadata, file1_s1d1); - copy_binary(_metadata, file1_s1d2); - copy_binary(_metadata, file1_s1d3); + copy_file(_metadata, bin_true, file1_s1d1); + copy_file(_metadata, bin_true, file1_s1d2); + copy_file(_metadata, bin_true, file1_s1d3); enforce_ruleset(_metadata, ruleset_fd); ASSERT_EQ(0, close(ruleset_fd)); @@ -2048,6 +2047,83 @@ TEST_F_FORK(layout1, execute) test_execute(_metadata, 0, file1_s1d3); } +TEST_F_FORK(layout1, umount_sandboxer) +{ + int pipe_child[2], pipe_parent[2]; + char buf_parent; + pid_t child; + int status; + + copy_file(_metadata, bin_sandbox_and_launch, file1_s3d3); + ASSERT_EQ(0, pipe2(pipe_child, 0)); + ASSERT_EQ(0, pipe2(pipe_parent, 0)); + + child = fork(); + ASSERT_LE(0, child); + if (child == 0) { + char pipe_child_str[12], pipe_parent_str[12]; + char *const argv[] = { (char *)file1_s3d3, + (char *)bin_wait_pipe, pipe_child_str, + pipe_parent_str, NULL }; + + /* Passes the pipe FDs to the executed binary and its child. */ + EXPECT_EQ(0, close(pipe_child[0])); + EXPECT_EQ(0, close(pipe_parent[1])); + snprintf(pipe_child_str, sizeof(pipe_child_str), "%d", + pipe_child[1]); + snprintf(pipe_parent_str, sizeof(pipe_parent_str), "%d", + pipe_parent[0]); + + /* + * We need bin_sandbox_and_launch (copied inside the mount as + * file1_s3d3) to execute bin_wait_pipe (outside the mount) to + * make sure the mount point will not be EBUSY because of + * file1_s3d3 being in use. This avoids a potential race + * condition between the following read() and umount() calls. + */ + ASSERT_EQ(0, execve(argv[0], argv, NULL)) + { + TH_LOG("Failed to execute \"%s\": %s", argv[0], + strerror(errno)); + }; + _exit(1); + return; + } + + EXPECT_EQ(0, close(pipe_child[1])); + EXPECT_EQ(0, close(pipe_parent[0])); + + /* Waits for the child to sandbox itself. */ + EXPECT_EQ(1, read(pipe_child[0], &buf_parent, 1)); + + /* Tests that the sandboxer is tied to its mount point. */ + set_cap(_metadata, CAP_SYS_ADMIN); + EXPECT_EQ(-1, umount(dir_s3d2)); + EXPECT_EQ(EBUSY, errno); + clear_cap(_metadata, CAP_SYS_ADMIN); + + /* Signals the child to launch a grandchild. */ + EXPECT_EQ(1, write(pipe_parent[1], ".", 1)); + + /* Waits for the grandchild. */ + EXPECT_EQ(1, read(pipe_child[0], &buf_parent, 1)); + + /* Tests that the domain's sandboxer is not tied to its mount point. */ + set_cap(_metadata, CAP_SYS_ADMIN); + EXPECT_EQ(0, umount(dir_s3d2)) + { + TH_LOG("Failed to umount \"%s\": %s", dir_s3d2, + strerror(errno)); + }; + clear_cap(_metadata, CAP_SYS_ADMIN); + + /* Signals the grandchild to terminate. */ + EXPECT_EQ(1, write(pipe_parent[1], ".", 1)); + ASSERT_EQ(child, waitpid(child, &status, 0)); + ASSERT_EQ(1, WIFEXITED(status)); + ASSERT_EQ(0, WEXITSTATUS(status)); +} + TEST_F_FORK(layout1, link) { const struct rule layer1[] = { diff --git a/tools/testing/selftests/landlock/sandbox-and-launch.c b/tools/testing/selftests/landlock/sandbox-and-launch.c new file mode 100644 index 0000000000000..3e32e1a51ac53 --- /dev/null +++ b/tools/testing/selftests/landlock/sandbox-and-launch.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Sandbox itself and execute another program (in a different mount point). + * + * Used by layout1.umount_sandboxer from fs_test.c + * + * Copyright © 2024-2025 Microsoft Corporation + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include + +#include "wrappers.h" + +int main(int argc, char *argv[]) +{ + struct landlock_ruleset_attr ruleset_attr = { + .scoped = LANDLOCK_SCOPE_SIGNAL, + }; + int pipe_child, pipe_parent, ruleset_fd; + char buf; + + /* + * The first argument must be the file descriptor number of a pipe. + * The second argument must be the program to execute. + */ + if (argc != 4) { + fprintf(stderr, "Wrong number of arguments (not three)\n"); + return 1; + } + + pipe_child = atoi(argv[2]); + pipe_parent = atoi(argv[3]); + + ruleset_fd = + landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); + if (ruleset_fd < 0) { + perror("Failed to create ruleset"); + return 1; + } + + if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { + perror("Failed to call prctl()"); + return 1; + } + + if (landlock_restrict_self(ruleset_fd, 0)) { + perror("Failed to restrict self"); + return 1; + } + + if (close(ruleset_fd)) { + perror("Failed to close ruleset"); + return 1; + } + + /* Signals that we are sandboxed. */ + errno = 0; + if (write(pipe_child, ".", 1) != 1) { + perror("Failed to write to the second argument"); + return 1; + } + + /* Waits for the parent to try to umount. */ + if (read(pipe_parent, &buf, 1) != 1) { + perror("Failed to write to the third argument"); + return 1; + } + + /* Shifts arguments. */ + argv[0] = argv[1]; + argv[1] = argv[2]; + argv[2] = argv[3]; + argv[3] = NULL; + execve(argv[0], argv, NULL); + perror("Failed to execute the provided binary"); + return 1; +} diff --git a/tools/testing/selftests/landlock/wait-pipe.c b/tools/testing/selftests/landlock/wait-pipe.c new file mode 100644 index 0000000000000..0dbcd260a0faf --- /dev/null +++ b/tools/testing/selftests/landlock/wait-pipe.c @@ -0,0 +1,42 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Write in a pipe and wait. + * + * Used by layout1.umount_sandboxer from fs_test.c + * + * Copyright © 2024-2025 Microsoft Corporation + */ + +#define _GNU_SOURCE +#include +#include +#include + +int main(int argc, char *argv[]) +{ + int pipe_child, pipe_parent; + char buf; + + /* The first argument must be the file descriptor number of a pipe. */ + if (argc != 3) { + fprintf(stderr, "Wrong number of arguments (not two)\n"); + return 1; + } + + pipe_child = atoi(argv[1]); + pipe_parent = atoi(argv[2]); + + /* Signals that we are waiting. */ + if (write(pipe_child, ".", 1) != 1) { + perror("Failed to write to first argument"); + return 1; + } + + /* Waits for the parent do its test. */ + if (read(pipe_parent, &buf, 1) != 1) { + perror("Failed to write to the second argument"); + return 1; + } + + return 0; +}