| Message ID | 20220930160144.141504-6-gnoack3000@gmail.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | landlock: truncate support | expand |
On Fri, Sep 30, 2022 at 06:01:42PM +0200, Günther Noack wrote: > 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@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 7ba18eb23783..8ec8971e9580 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> > @@ -187,3 +188,69 @@ clear_cap(struct __test_metadata *const _metadata, const cap_value_t caps) > { > _effective_cap(_metadata, caps, CAP_CLEAR); > } > + > +/* Receives an FD from a UNIX socket. Returns the received FD, -1 on error. */ > +__maybe_unused static int recv_fd(int usock) Ah bummer, the definition of "__maybe_unused" is not visible here (last minute change before sending it off...). Will fix it. > +{ > + 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. */ > +__maybe_unused static int 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 > --
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 7ba18eb23783..8ec8971e9580 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> @@ -187,3 +188,69 @@ clear_cap(struct __test_metadata *const _metadata, const cap_value_t caps) { _effective_cap(_metadata, caps, CAP_CLEAR); } + +/* Receives an FD from a UNIX socket. Returns the received FD, -1 on error. */ +__maybe_unused static int 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. */ +__maybe_unused static int 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 */
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@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(-)