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Message-ID: <20240807.WieGae7wahh6@digikod.net>
Date: Wed, 7 Aug 2024 17:08:40 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Tahera Fahimi <fahimitahera@...il.com>
Cc: outreachy@...ts.linux.dev, gnoack@...gle.com, paul@...l-moore.com,
jmorris@...ei.org, serge@...lyn.com, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, bjorn3_gh@...tonmail.com, jannh@...gle.com,
netdev@...r.kernel.org
Subject: Re: [PATCH v8 2/4] selftests/landlock: Abstract unix socket
restriction tests
On Thu, Aug 01, 2024 at 10:02:34PM -0600, Tahera Fahimi wrote:
> The patch introduces Landlock ABI version 6 and has four types of tests:
> 1) unix_socket: base tests of the abstract socket scoping mechanism for a
> landlocked process, same as the ptrace test.
> 2) optional_scoping: generates three processes with different domains and
> tests if a process with a non-scoped domain can connect to other
> processes.
> 3) unix_sock_special_cases: since the socket's creator credentials are used
> for scoping sockets, this test examines the cases where the socket's
> credentials are different from the process using it.
> 4) pathname_address_sockets: ensures that Unix sockets bound to a
> null-terminated filesystem can still connect to a socket outside of
> their scoped domain. This means that even if the domain is scoped with
> LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET, the socket can connect to a socket
> outside the scoped domain.
>
> Signed-off-by: Tahera Fahimi <fahimitahera@...il.com>
> ---
> Changes in versions:
> V8:
> - Move tests to scoped_abstract_unix_test.c file.
> - To avoid potential conflicts among Unix socket names in different tests,
> set_unix_address is added to common.h to set different sun_path for Unix sockets.
> - protocol_variant and service_fixture structures are also moved to common.h
> - Adding pathname_address_sockets to cover all types of address formats
> for unix sockets, and moving remove_path() to common.h to reuse in this test.
> V7:
> - Introducing landlock ABI version 6.
> - Adding some edge test cases to optional_scoping test.
> - Using `enum` for different domains in optional_scoping tests.
> - Extend unix_sock_special_cases test cases for connected(SOCK_STREAM) sockets.
> - Modifying inline comments.
> V6:
> - Introducing optional_scoping test which ensures a sandboxed process with a
> non-scoped domain can still connect to another abstract unix socket(either
> sandboxed or non-sandboxed).
> - Introducing unix_sock_special_cases test which tests examines scenarios where
> the connecting sockets have different domain than the process using them.
> V4:
> - Introducing unix_socket to evaluate the basic scoping mechanism for abstract
> unix sockets.
> ---
> tools/testing/selftests/landlock/base_test.c | 2 +-
> tools/testing/selftests/landlock/common.h | 72 ++
> tools/testing/selftests/landlock/fs_test.c | 34 -
> tools/testing/selftests/landlock/net_test.c | 31 +-
> .../landlock/scoped_abstract_unix_test.c | 1136 +++++++++++++++++
> 5 files changed, 1210 insertions(+), 65 deletions(-)
> create mode 100644 tools/testing/selftests/landlock/scoped_abstract_unix_test.c
> diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
> index 3c1e9f35b531..52b00472a487 100644
> --- a/tools/testing/selftests/landlock/base_test.c
> +++ b/tools/testing/selftests/landlock/base_test.c
> @@ -75,7 +75,7 @@ TEST(abi_version)
> const struct landlock_ruleset_attr ruleset_attr = {
> .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
> };
> - ASSERT_EQ(5, landlock_create_ruleset(NULL, 0,
> + ASSERT_EQ(6, landlock_create_ruleset(NULL, 0,
> LANDLOCK_CREATE_RULESET_VERSION));
>
> ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
> diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h
> index 7e2b431b9f90..a0c8126d94b4 100644
> --- a/tools/testing/selftests/landlock/common.h
> +++ b/tools/testing/selftests/landlock/common.h
> @@ -16,8 +16,11 @@
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <unistd.h>
> +#include <sys/un.h>
> +#include <arpa/inet.h>
>
> #include "../kselftest_harness.h"
> +#define TMP_DIR "tmp"
>
> #ifndef __maybe_unused
> #define __maybe_unused __attribute__((__unused__))
> @@ -226,3 +229,72 @@ enforce_ruleset(struct __test_metadata *const _metadata, const int ruleset_fd)
> TH_LOG("Failed to enforce ruleset: %s", strerror(errno));
> }
> }
> +
> +struct protocol_variant {
> + int domain;
> + int type;
> +};
> +
> +struct service_fixture {
> + struct protocol_variant protocol;
> + /* port is also stored in ipv4_addr.sin_port or ipv6_addr.sin6_port */
> + unsigned short port;
> + union {
> + struct sockaddr_in ipv4_addr;
> + struct sockaddr_in6 ipv6_addr;
> + struct {
> + struct sockaddr_un unix_addr;
> + socklen_t unix_addr_len;
> + };
> + };
> +};
> +
> +static pid_t __maybe_unused sys_gettid(void)
> +{
> + return syscall(__NR_gettid);
> +}
> +
> +static void __maybe_unused set_unix_address(struct service_fixture *const srv,
> + const unsigned short index)
> +{
> + srv->unix_addr.sun_family = AF_UNIX;
> + sprintf(srv->unix_addr.sun_path,
> + "_selftests-landlock-abstract-unix-tid%d-index%d", sys_gettid(),
> + index);
> + srv->unix_addr_len = SUN_LEN(&srv->unix_addr);
> + srv->unix_addr.sun_path[0] = '\0';
> +}
> +
> +static int __maybe_unused remove_path(const char *const path)
We don't need to import remove_path() for these simple filesystem
actions.
> +{
> + char *walker;
> + int i, ret, err = 0;
> +
> + walker = strdup(path);
> + if (!walker) {
> + err = ENOMEM;
> + goto out;
> + }
> + if (unlink(path) && rmdir(path)) {
> + if (errno != ENOENT && errno != ENOTDIR)
> + err = errno;
> + goto out;
> + }
> + for (i = strlen(walker); i > 0; i--) {
> + if (walker[i] != '/')
> + continue;
> + walker[i] = '\0';
> + ret = rmdir(walker);
> + if (ret) {
> + if (errno != ENOTEMPTY && errno != EBUSY)
> + err = errno;
> + goto out;
> + }
> + if (strcmp(walker, TMP_DIR) == 0)
> + goto out;
> + }
> +
> +out:
> + free(walker);
> + return err;
> +}
> diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
> index 7d063c652be1..fc74cab6dfb8 100644
> --- a/tools/testing/selftests/landlock/fs_test.c
> +++ b/tools/testing/selftests/landlock/fs_test.c
> @@ -221,40 +221,6 @@ static void create_file(struct __test_metadata *const _metadata,
> }
> }
>
> -static int remove_path(const char *const path)
> -{
> - char *walker;
> - int i, ret, err = 0;
> -
> - walker = strdup(path);
> - if (!walker) {
> - err = ENOMEM;
> - goto out;
> - }
> - if (unlink(path) && rmdir(path)) {
> - if (errno != ENOENT && errno != ENOTDIR)
> - err = errno;
> - goto out;
> - }
> - for (i = strlen(walker); i > 0; i--) {
> - if (walker[i] != '/')
> - continue;
> - walker[i] = '\0';
> - ret = rmdir(walker);
> - if (ret) {
> - if (errno != ENOTEMPTY && errno != EBUSY)
> - err = errno;
> - goto out;
> - }
> - if (strcmp(walker, TMP_DIR) == 0)
> - goto out;
> - }
> -
> -out:
> - free(walker);
> - return err;
> -}
> -
> struct mnt_opt {
> const char *const source;
> const char *const type;
> diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
> index f21cfbbc3638..4e0aeb53b225 100644
> --- a/tools/testing/selftests/landlock/net_test.c
> +++ b/tools/testing/selftests/landlock/net_test.c
> @@ -36,30 +36,6 @@ enum sandbox_type {
> TCP_SANDBOX,
> };
>
> -struct protocol_variant {
> - int domain;
> - int type;
> -};
> -
> -struct service_fixture {
> - struct protocol_variant protocol;
> - /* port is also stored in ipv4_addr.sin_port or ipv6_addr.sin6_port */
> - unsigned short port;
> - union {
> - struct sockaddr_in ipv4_addr;
> - struct sockaddr_in6 ipv6_addr;
> - struct {
> - struct sockaddr_un unix_addr;
> - socklen_t unix_addr_len;
> - };
> - };
> -};
> -
> -static pid_t sys_gettid(void)
> -{
> - return syscall(__NR_gettid);
> -}
> -
> static int set_service(struct service_fixture *const srv,
> const struct protocol_variant prot,
> const unsigned short index)
> @@ -92,12 +68,7 @@ static int set_service(struct service_fixture *const srv,
> return 0;
>
> case AF_UNIX:
> - srv->unix_addr.sun_family = prot.domain;
> - sprintf(srv->unix_addr.sun_path,
> - "_selftests-landlock-net-tid%d-index%d", sys_gettid(),
> - index);
> - srv->unix_addr_len = SUN_LEN(&srv->unix_addr);
> - srv->unix_addr.sun_path[0] = '\0';
> + set_unix_address(srv, index);
Please create a standalone patch for existing code refactoring, and then
another patch for the new tests.
> return 0;
> }
> return 1;
> diff --git a/tools/testing/selftests/landlock/scoped_abstract_unix_test.c b/tools/testing/selftests/landlock/scoped_abstract_unix_test.c
> new file mode 100644
> index 000000000000..ffa1f01dbbce
> --- /dev/null
> +++ b/tools/testing/selftests/landlock/scoped_abstract_unix_test.c
> +TEST_F(unix_socket, abstract_unix_socket)
> +{
> + int status;
> + pid_t child;
> + bool can_connect_to_parent, can_connect_to_child;
> + int err, err_dgram;
> + int pipe_child[2], pipe_parent[2];
> + char buf_parent;
> +
> + /*
> + * can_connect_to_child is true if a parent process can connect to its
> + * child process. The parent process is not isolated from the child
> + * with a dedicated Landlock domain.
> + */
> + can_connect_to_child = !variant->domain_parent;
> + /*
> + * can_connect_to_parent is true if a child process can connect to its
> + * parent process. This depends on the child process is not isolated from
> + * the parent with a dedicated Landlock domain.
> + */
> + can_connect_to_parent = !variant->domain_child;
> +
> + ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
> + ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
> + if (variant->domain_both) {
> + create_unix_domain(_metadata);
> + if (!__test_passed(_metadata))
> + return;
> + }
> +
> + child = fork();
> + ASSERT_LE(0, child);
> + if (child == 0) {
> + char buf_child;
> +
> + ASSERT_EQ(0, close(pipe_parent[1]));
> + ASSERT_EQ(0, close(pipe_child[0]));
> + if (variant->domain_child)
> + create_unix_domain(_metadata);
> +
> + /* Waits for the parent to be in a domain, if any. */
> + ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
> +
> + if (variant->connect_to_parent) {
> + self->client = socket(AF_UNIX, SOCK_STREAM, 0);
> + self->dgram_client = socket(AF_UNIX, SOCK_DGRAM, 0);
> +
> + ASSERT_NE(-1, self->client);
> + ASSERT_NE(-1, self->dgram_client);
> + ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
> +
> + err = connect(self->client,
> + &self->stream_address.unix_addr,
> + (self->stream_address).unix_addr_len);
> + err_dgram =
> + connect(self->dgram_client,
> + &self->dgram_address.unix_addr,
> + (self->dgram_address).unix_addr_len);
> +
> + if (can_connect_to_parent) {
> + EXPECT_EQ(0, err);
> + EXPECT_EQ(0, err_dgram);
> + } else {
> + EXPECT_EQ(-1, err);
> + EXPECT_EQ(-1, err_dgram);
> + EXPECT_EQ(EPERM, errno);
> + }
> + } else {
> + self->server = socket(AF_UNIX, SOCK_STREAM, 0);
> + self->dgram_server = socket(AF_UNIX, SOCK_DGRAM, 0);
> + ASSERT_NE(-1, self->server);
> + ASSERT_NE(-1, self->dgram_server);
> +
> + ASSERT_EQ(0,
> + bind(self->server,
> + &self->stream_address.unix_addr,
> + (self->stream_address).unix_addr_len));
> + ASSERT_EQ(0, bind(self->dgram_server,
> + &self->dgram_address.unix_addr,
> + (self->dgram_address).unix_addr_len));
> + ASSERT_EQ(0, listen(self->server, 32));
Please, avoid the use of hardcoded values (e.g. in all listen calls).
You can create a global backlog variable like in net_test.c (just copy
it, no need to include it in common.h).
> +
> + /* signal to parent that child is listening */
> + ASSERT_EQ(1, write(pipe_child[1], ".", 1));
> + /* wait to connect */
> + ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
> + }
> + _exit(_metadata->exit_code);
> + return;
> + }
> +
> + ASSERT_EQ(0, close(pipe_child[1]));
> + ASSERT_EQ(0, close(pipe_parent[0]));
> +
> + if (variant->domain_parent)
> + create_unix_domain(_metadata);
> +
> + /* Signals that the parent is in a domain, if any. */
> + ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
> +
> + if (!variant->connect_to_parent) {
> + self->client = socket(AF_UNIX, SOCK_STREAM, 0);
> + self->dgram_client = socket(AF_UNIX, SOCK_DGRAM, 0);
> +
> + ASSERT_NE(-1, self->client);
> + ASSERT_NE(-1, self->dgram_client);
> +
> + /* Waits for the child to listen */
> + ASSERT_EQ(1, read(pipe_child[0], &buf_parent, 1));
> + err = connect(self->client, &self->stream_address.unix_addr,
> + (self->stream_address).unix_addr_len);
> + err_dgram = connect(self->dgram_client,
> + &self->dgram_address.unix_addr,
> + (self->dgram_address).unix_addr_len);
> +
> + if (can_connect_to_child) {
> + EXPECT_EQ(0, err);
> + EXPECT_EQ(0, err_dgram);
> + } else {
> + EXPECT_EQ(-1, err);
> + EXPECT_EQ(-1, err_dgram);
> + EXPECT_EQ(EPERM, errno);
> + }
> + ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
> + } else {
> + self->server = socket(AF_UNIX, SOCK_STREAM, 0);
> + self->dgram_server = socket(AF_UNIX, SOCK_DGRAM, 0);
> + ASSERT_NE(-1, self->server);
> + ASSERT_NE(-1, self->dgram_server);
> + ASSERT_EQ(0, bind(self->server, &self->stream_address.unix_addr,
> + (self->stream_address).unix_addr_len));
> + ASSERT_EQ(0, bind(self->dgram_server,
> + &self->dgram_address.unix_addr,
> + (self->dgram_address).unix_addr_len));
> + ASSERT_EQ(0, listen(self->server, 32));
> +
> + /* signal to child that parent is listening */
> + ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
> + }
> +
> + ASSERT_EQ(child, waitpid(child, &status, 0));
> +
> + if (WIFSIGNALED(status) || !WIFEXITED(status) ||
> + WEXITSTATUS(status) != EXIT_SUCCESS)
> + _metadata->exit_code = KSFT_FAIL;
> +}
> +
> +enum sandbox_type {
> + NO_SANDBOX,
> + SCOPE_SANDBOX,
> + /* Any other type of sandboxing domain */
> + OTHER_SANDBOX,
> +};
> +
> +/* clang-format off */
> +FIXTURE(optional_scoping)
> +{
> + struct service_fixture parent_address, child_address;
> + int parent_server, child_server, client;
The variables should be local ones.
> +};
> +
> +/* clang-format on */
> +FIXTURE_VARIANT(optional_scoping)
> +{
> + const int domain_all;
> + const int domain_parent;
> + const int domain_children;
> + const int domain_child;
> + const int domain_grand_child;
domain_grand_child is always NO_SANDBOX in the variants.
> + const int type;
> +};
> +
> +FIXTURE_SETUP(optional_scoping)
s/optional_scoping/scoping/ ?
> +{
> + memset(&self->parent_address, 0, sizeof(self->parent_address));
> + memset(&self->child_address, 0, sizeof(self->child_address));
> +
> + set_unix_address(&self->parent_address, 0);
> + set_unix_address(&self->child_address, 1);
> +}
> +TEST_F(optional_scoping, unix_scoping)
> +{
> + pid_t child;
> + int status;
> + bool can_connect_to_parent, can_connect_to_child;
> + int pipe_parent[2];
> +
> + if (variant->domain_grand_child == SCOPE_SANDBOX)
> + can_connect_to_child = false;
We never go through this case.
> + else
> + can_connect_to_child = true;
> +
> + if (!can_connect_to_child || variant->domain_children == SCOPE_SANDBOX)
> + can_connect_to_parent = false;
> + else
> + can_connect_to_parent = true;
We never go through this case.
> +
> + ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
> +
> + if (variant->domain_all == OTHER_SANDBOX)
> + create_fs_domain(_metadata);
> + else if (variant->domain_all == SCOPE_SANDBOX)
> + create_unix_domain(_metadata);
> +
> + child = fork();
> + ASSERT_LE(0, child);
> + if (child == 0) {
> + int pipe_child[2];
> +
> + ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
> + pid_t grand_child;
> +
> + if (variant->domain_children == OTHER_SANDBOX)
> + create_fs_domain(_metadata);
> + else if (variant->domain_children == SCOPE_SANDBOX)
> + create_unix_domain(_metadata);
> +
> + grand_child = fork();
> + ASSERT_LE(0, grand_child);
> + if (grand_child == 0) {
> + ASSERT_EQ(0, close(pipe_parent[1]));
> + ASSERT_EQ(0, close(pipe_child[1]));
> +
> + char buf1, buf2;
> + int err;
> +
> + if (variant->domain_grand_child == OTHER_SANDBOX)
> + create_fs_domain(_metadata);
> + else if (variant->domain_grand_child == SCOPE_SANDBOX)
> + create_unix_domain(_metadata);
> +
> + self->client = socket(AF_UNIX, variant->type, 0);
> + ASSERT_NE(-1, self->client);
> +
> + ASSERT_EQ(1, read(pipe_child[0], &buf2, 1));
> + err = connect(self->client,
> + &self->child_address.unix_addr,
> + (self->child_address).unix_addr_len);
No need for these extra parenthesis.
> + if (can_connect_to_child) {
> + EXPECT_EQ(0, err);
> + } else {
> + EXPECT_EQ(-1, err);
> + EXPECT_EQ(EPERM, errno);
> + }
> +
> + if (variant->type == SOCK_STREAM) {
> + EXPECT_EQ(0, close(self->client));
> + self->client =
> + socket(AF_UNIX, variant->type, 0);
> + ASSERT_NE(-1, self->client);
> + }
> +
> + ASSERT_EQ(1, read(pipe_parent[0], &buf1, 1));
> + err = connect(self->client,
> + &self->parent_address.unix_addr,
> + (self->parent_address).unix_addr_len);
> + if (can_connect_to_parent) {
> + EXPECT_EQ(0, err);
> + } else {
> + EXPECT_EQ(-1, err);
> + EXPECT_EQ(EPERM, errno);
> + }
> + EXPECT_EQ(0, close(self->client));
> +
> + _exit(_metadata->exit_code);
> + return;
> + }
> +
> + ASSERT_EQ(0, close(pipe_child[0]));
> + if (variant->domain_child == OTHER_SANDBOX)
> + create_fs_domain(_metadata);
> + else if (variant->domain_child == SCOPE_SANDBOX)
> + create_unix_domain(_metadata);
> +
> + self->child_server = socket(AF_UNIX, variant->type, 0);
> + ASSERT_NE(-1, self->child_server);
> + ASSERT_EQ(0, bind(self->child_server,
> + &self->child_address.unix_addr,
> + (self->child_address).unix_addr_len));
> + if (variant->type == SOCK_STREAM)
> + ASSERT_EQ(0, listen(self->child_server, 32));
> +
> + ASSERT_EQ(1, write(pipe_child[1], ".", 1));
> + ASSERT_EQ(grand_child, waitpid(grand_child, &status, 0));
> + return;
> + }
> + ASSERT_EQ(0, close(pipe_parent[0]));
> +
> + if (variant->domain_parent == OTHER_SANDBOX)
> + create_fs_domain(_metadata);
> + else if (variant->domain_parent == SCOPE_SANDBOX)
> + create_unix_domain(_metadata);
> +
> + self->parent_server = socket(AF_UNIX, variant->type, 0);
> + ASSERT_NE(-1, self->parent_server);
> + ASSERT_EQ(0, bind(self->parent_server, &self->parent_address.unix_addr,
> + (self->parent_address).unix_addr_len));
> +
> + if (variant->type == SOCK_STREAM)
> + ASSERT_EQ(0, listen(self->parent_server, 32));
> +
> + ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
> + ASSERT_EQ(child, waitpid(child, &status, 0));
> + if (WIFSIGNALED(status) || !WIFEXITED(status) ||
> + WEXITSTATUS(status) != EXIT_SUCCESS)
> + _metadata->exit_code = KSFT_FAIL;
> +}
> +FIXTURE_SETUP(pathname_address_sockets)
> +{
> + /* setup abstract addresses */
> + memset(&self->stream_address, 0, sizeof(self->stream_address));
> + set_unix_address(&self->stream_address, 0);
> +
> + memset(&self->dgram_address, 0, sizeof(self->dgram_address));
> + set_unix_address(&self->dgram_address, 0);
> +
> + const char *s_path = variant->stream_path;
> + const char *dg_path = variant->dgram_path;
> +
> + disable_caps(_metadata);
> + umask(0077);
> + ASSERT_EQ(0, mkdir(TMP_DIR, 0700));
> +
> + ASSERT_EQ(0, mknod(s_path, S_IFREG | 0700, 0))
> + {
> + TH_LOG("Failed to create file \"%s\": %s", s_path,
> + strerror(errno));
> + remove_path(TMP_DIR);
Just use rmdir() instead of remove_path() everywhere.
> + }
> + ASSERT_EQ(0, mknod(dg_path, S_IFREG | 0700, 0))
> + {
> + TH_LOG("Failed to create file \"%s\": %s", dg_path,
> + strerror(errno));
> + remove_path(TMP_DIR);
> + }
> +}
> +
> +FIXTURE_TEARDOWN(pathname_address_sockets)
> +{
> + const char *s_path = variant->stream_path;
> + const char *dg_path = variant->dgram_path;
> +
> + ASSERT_EQ(0, remove_path(dg_path));
Just use unlink() and rmdir().
> + ASSERT_EQ(0, remove_path(s_path));
> + ASSERT_EQ(0, remove_path(TMP_DIR));
> +}
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