[PATCH v8 7/9] selftests/landlock: Test FD passing from a Landlock-restricted to an unrestricted process
Günther Noack
gnoack3000 at gmail.com
Sat Oct 1 15:49:06 UTC 2022
A file descriptor created in a restricted process carries Landlock
restrictions with it which will apply even if the same opened file is
used from an unrestricted process.
This change extracts suitable FD-passing helpers from base_test.c and
moves them to common.h. We use the fixture variants from the ftruncate
fixture to exercise the same scenarios as in the open_and_ftruncate
test, but doing the Landlock restriction and open() in a different
process than the ftruncate() call.
Signed-off-by: Günther Noack <gnoack3000 at gmail.com>
---
tools/testing/selftests/landlock/base_test.c | 36 +----------
tools/testing/selftests/landlock/common.h | 67 ++++++++++++++++++++
tools/testing/selftests/landlock/fs_test.c | 62 ++++++++++++++++++
3 files changed, 132 insertions(+), 33 deletions(-)
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 72cdae277b02..6d1b6eedb432 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -263,23 +263,6 @@ TEST(ruleset_fd_transfer)
.allowed_access = LANDLOCK_ACCESS_FS_READ_DIR,
};
int ruleset_fd_tx, dir_fd;
- union {
- /* Aligned ancillary data buffer. */
- char buf[CMSG_SPACE(sizeof(ruleset_fd_tx))];
- struct cmsghdr _align;
- } cmsg_tx = {};
- char data_tx = '.';
- struct iovec io = {
- .iov_base = &data_tx,
- .iov_len = sizeof(data_tx),
- };
- struct msghdr msg = {
- .msg_iov = &io,
- .msg_iovlen = 1,
- .msg_control = &cmsg_tx.buf,
- .msg_controllen = sizeof(cmsg_tx.buf),
- };
- struct cmsghdr *cmsg;
int socket_fds[2];
pid_t child;
int status;
@@ -298,33 +281,20 @@ TEST(ruleset_fd_transfer)
&path_beneath_attr, 0));
ASSERT_EQ(0, close(path_beneath_attr.parent_fd));
- cmsg = CMSG_FIRSTHDR(&msg);
- ASSERT_NE(NULL, cmsg);
- cmsg->cmsg_len = CMSG_LEN(sizeof(ruleset_fd_tx));
- cmsg->cmsg_level = SOL_SOCKET;
- cmsg->cmsg_type = SCM_RIGHTS;
- memcpy(CMSG_DATA(cmsg), &ruleset_fd_tx, sizeof(ruleset_fd_tx));
-
/* Sends the ruleset FD over a socketpair and then close it. */
ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
socket_fds));
- ASSERT_EQ(sizeof(data_tx), sendmsg(socket_fds[0], &msg, 0));
+ ASSERT_EQ(0, send_fd(socket_fds[0], ruleset_fd_tx));
ASSERT_EQ(0, close(socket_fds[0]));
ASSERT_EQ(0, close(ruleset_fd_tx));
child = fork();
ASSERT_LE(0, child);
if (child == 0) {
- int ruleset_fd_rx;
+ int ruleset_fd_rx = recv_fd(socket_fds[1]);
- *(char *)msg.msg_iov->iov_base = '\0';
- ASSERT_EQ(sizeof(data_tx),
- recvmsg(socket_fds[1], &msg, MSG_CMSG_CLOEXEC));
- ASSERT_EQ('.', *(char *)msg.msg_iov->iov_base);
+ ASSERT_LE(0, ruleset_fd_rx);
ASSERT_EQ(0, close(socket_fds[1]));
- cmsg = CMSG_FIRSTHDR(&msg);
- ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(ruleset_fd_tx)));
- memcpy(&ruleset_fd_rx, CMSG_DATA(cmsg), sizeof(ruleset_fd_tx));
/* Enforces the received ruleset on the child. */
ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h
index 7d34592471db..15149d34e43b 100644
--- a/tools/testing/selftests/landlock/common.h
+++ b/tools/testing/selftests/landlock/common.h
@@ -10,6 +10,7 @@
#include <errno.h>
#include <linux/landlock.h>
#include <sys/capability.h>
+#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
@@ -189,3 +190,69 @@ static void __maybe_unused clear_cap(struct __test_metadata *const _metadata,
{
_effective_cap(_metadata, caps, CAP_CLEAR);
}
+
+/* Receives an FD from a UNIX socket. Returns the received FD, -1 on error. */
+static int __maybe_unused recv_fd(int usock)
+{
+ int fd_rx;
+ union {
+ /* Aligned ancillary data buffer. */
+ char buf[CMSG_SPACE(sizeof(fd_rx))];
+ struct cmsghdr _align;
+ } cmsg_rx = {};
+ char data = '\0';
+ struct iovec io = {
+ .iov_base = &data,
+ .iov_len = sizeof(data),
+ };
+ struct msghdr msg = {
+ .msg_iov = &io,
+ .msg_iovlen = 1,
+ .msg_control = &cmsg_rx.buf,
+ .msg_controllen = sizeof(cmsg_rx.buf),
+ };
+ struct cmsghdr *cmsg;
+ int res;
+
+ res = recvmsg(usock, &msg, MSG_CMSG_CLOEXEC);
+ if (res < 0)
+ return -1;
+
+ cmsg = CMSG_FIRSTHDR(&msg);
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof(fd_rx)))
+ return -1;
+
+ memcpy(&fd_rx, CMSG_DATA(cmsg), sizeof(fd_rx));
+ return fd_rx;
+}
+
+/* Sends an FD on a UNIX socket. Returns 0 on success or -1 on error. */
+static int __maybe_unused send_fd(int usock, int fd_tx)
+{
+ union {
+ /* Aligned ancillary data buffer. */
+ char buf[CMSG_SPACE(sizeof(fd_tx))];
+ struct cmsghdr _align;
+ } cmsg_tx = {};
+ char data_tx = '.';
+ struct iovec io = {
+ .iov_base = &data_tx,
+ .iov_len = sizeof(data_tx),
+ };
+ struct msghdr msg = {
+ .msg_iov = &io,
+ .msg_iovlen = 1,
+ .msg_control = &cmsg_tx.buf,
+ .msg_controllen = sizeof(cmsg_tx.buf),
+ };
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+
+ cmsg->cmsg_len = CMSG_LEN(sizeof(fd_tx));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ memcpy(CMSG_DATA(cmsg), &fd_tx, sizeof(fd_tx));
+
+ if (sendmsg(usock, &msg, 0) < 0)
+ return -1;
+ return 0;
+}
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 308f6f36e8c0..93ed80a25a74 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3541,6 +3541,68 @@ TEST_F_FORK(ftruncate, open_and_ftruncate)
}
}
+TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes)
+{
+ int child, fd, status;
+ int socket_fds[2];
+
+ ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
+ socket_fds));
+
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ /*
+ * Enable Landlock in the child process, open a file descriptor
+ * where truncation is forbidden and send it to the
+ * non-landlocked parent process.
+ */
+ const char *const path = file1_s1d1;
+ const struct rule rules[] = {
+ {
+ .path = path,
+ .access = variant->permitted,
+ },
+ {},
+ };
+ int fd, ruleset_fd;
+
+ /* Enable Landlock. */
+ ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ fd = open(path, O_WRONLY);
+ ASSERT_EQ(variant->expected_open_result, (fd < 0 ? errno : 0));
+
+ if (fd >= 0) {
+ ASSERT_EQ(0, send_fd(socket_fds[0], fd));
+ ASSERT_EQ(0, close(fd));
+ }
+
+ ASSERT_EQ(0, close(socket_fds[0]));
+
+ _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
+ }
+
+ if (variant->expected_open_result == 0) {
+ fd = recv_fd(socket_fds[1]);
+ ASSERT_LE(0, fd);
+
+ EXPECT_EQ(variant->expected_ftruncate_result,
+ test_ftruncate(fd));
+ ASSERT_EQ(0, close(fd));
+ }
+
+ ASSERT_EQ(child, waitpid(child, &status, 0));
+ ASSERT_EQ(1, WIFEXITED(status));
+ ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+
+ ASSERT_EQ(0, close(socket_fds[0]));
+ ASSERT_EQ(0, close(socket_fds[1]));
+}
+
/* clang-format off */
FIXTURE(layout1_bind) {};
/* clang-format on */
--
2.37.3
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