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Diffstat (limited to '')
| -rw-r--r-- | src/nsresourced/test-userns-restrict.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/src/nsresourced/test-userns-restrict.c b/src/nsresourced/test-userns-restrict.c new file mode 100644 index 0000000..f509321 --- /dev/null +++ b/src/nsresourced/test-userns-restrict.c @@ -0,0 +1,182 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <sys/eventfd.h> + +#include "fd-util.h" +#include "main-func.h" +#include "missing_mount.h" +#include "missing_syscall.h" +#include "namespace-util.h" +#include "process-util.h" +#include "rm-rf.h" +#include "tmpfile-util.h" +#include "userns-restrict.h" + +static int make_tmpfs_fsmount(void) { + _cleanup_close_ int fsfd = -EBADF, mntfd = -EBADF; + + fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC); + assert_se(fsfd >= 0); + assert_se(fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) >= 0); + + mntfd = fsmount(fsfd, FSMOUNT_CLOEXEC, 0); + assert_se(mntfd >= 0); + + return TAKE_FD(mntfd); +} + +static void test_works_reg(int parent_fd, const char *fname) { + _cleanup_close_ int fd = -EBADF; + + fd = openat(parent_fd, fname, O_RDWR|O_CREAT|O_CLOEXEC, 0666); + assert_se(fd >= 0); +} + +static void test_fails_reg(int parent_fd, const char *fname) { + errno = 0; + assert_se(openat(parent_fd, fname, O_RDWR|O_CREAT|O_CLOEXEC, 0666) < 0); + assert_se(errno == EPERM); +} + +static void test_works_dir(int parent_fd, const char *fname) { + assert_se(mkdirat(parent_fd, fname, 0666) >= 0); +} + +static void test_fails_dir(int parent_fd, const char *fname) { + errno = 0; + assert_se(mkdirat(parent_fd, fname, 0666) < 0); + assert_se(errno == EPERM); +} + +static int run(int argc, char *argv[]) { + _cleanup_(userns_restrict_bpf_freep) struct userns_restrict_bpf *obj = NULL; + _cleanup_close_ int userns_fd = -EBADF, host_fd1 = -EBADF, host_tmpfs = -EBADF, afd = -EBADF, bfd = -EBADF; + _cleanup_(rm_rf_physical_and_freep) char *t = NULL; + _cleanup_(sigkill_waitp) pid_t pid = 0; + int r; + + log_set_max_level(LOG_DEBUG); + log_setup(); + + r = userns_restrict_install(/* pin= */ false, &obj); + if (ERRNO_IS_NOT_SUPPORTED(r)) { + log_notice("Skipping test, LSM-BPF logic not supported."); + return EXIT_TEST_SKIP; + } + if (ERRNO_IS_PRIVILEGE(r)) { + log_notice("Skipping test, lacking privileges."); + return EXIT_TEST_SKIP; + } + if (r < 0) + return r; + + assert_se(mkdtemp_malloc(NULL, &t) >= 0); + + host_fd1 = open(t, O_DIRECTORY|O_CLOEXEC); + assert_se(host_fd1 >= 0); + + host_tmpfs = make_tmpfs_fsmount(); + assert_se(host_tmpfs >= 0); + + userns_fd = userns_acquire("0 0 1", "0 0 1"); + if (userns_fd < 0) + return log_error_errno(userns_fd, "Failed to make user namespace: %m"); + + r = userns_restrict_put_by_fd( + obj, + userns_fd, + /* replace= */ true, + /* mount_fds= */ NULL, + /* n_mount_fds= */ 0); + if (r < 0) + return log_error_errno(r, "Failed to restrict user namespace: %m"); + + afd = eventfd(0, EFD_CLOEXEC); + bfd = eventfd(0, EFD_CLOEXEC); + + assert_se(afd >= 0 && bfd >= 0); + + r = safe_fork("(test)", FORK_DEATHSIG_SIGKILL, &pid); + assert_se(r >= 0); + if (r == 0) { + _cleanup_close_ int private_tmpfs = -EBADF; + + assert_se(setns(userns_fd, CLONE_NEWUSER) >= 0); + assert_se(unshare(CLONE_NEWNS) >= 0); + + /* Allocate tmpfs locally */ + private_tmpfs = make_tmpfs_fsmount(); + + /* These two host mounts should be inaccessible */ + test_fails_reg(host_fd1, "test"); + test_fails_reg(host_tmpfs, "xxx"); + test_fails_dir(host_fd1, "test2"); + test_fails_dir(host_tmpfs, "xxx2"); + + /* But this mount created locally should be fine */ + test_works_reg(private_tmpfs, "yyy"); + test_works_dir(private_tmpfs, "yyy2"); + + /* Let's sync with the parent, so that it allowlists more stuff for us */ + assert_se(eventfd_write(afd, 1) >= 0); + uint64_t x; + assert_se(eventfd_read(bfd, &x) >= 0); + + /* And now we should also have access to the host tmpfs */ + test_works_reg(host_tmpfs, "zzz"); + test_works_reg(private_tmpfs, "aaa"); + test_works_dir(host_tmpfs, "zzz2"); + test_works_dir(private_tmpfs, "aaa2"); + + /* But this one should still fail */ + test_fails_reg(host_fd1, "bbb"); + test_fails_dir(host_fd1, "bbb2"); + + /* Sync again, to get more stuff allowlisted */ + assert_se(eventfd_write(afd, 1) >= 0); + assert_se(eventfd_read(bfd, &x) >= 0); + + /* Everything should now be allowed */ + test_works_reg(host_tmpfs, "ccc"); + test_works_reg(host_fd1, "ddd"); + test_works_reg(private_tmpfs, "eee"); + test_works_dir(host_tmpfs, "ccc2"); + test_works_reg(host_fd1, "ddd2"); + test_works_dir(private_tmpfs, "eee2"); + + _exit(EXIT_SUCCESS); + } + + uint64_t x; + assert_se(eventfd_read(afd, &x) >= 0); + + r = userns_restrict_put_by_fd( + obj, + userns_fd, + /* replace= */ false, + &host_tmpfs, + 1); + if (r < 0) + return log_error_errno(r, "Failed to loosen user namespace: %m"); + + assert_se(eventfd_write(bfd, 1) >= 0); + + assert_se(eventfd_read(afd, &x) >= 0); + + r = userns_restrict_put_by_fd( + obj, + userns_fd, + /* replace= */ false, + &host_fd1, + 1); + if (r < 0) + return log_error_errno(r, "Failed to loosen user namespace: %m"); + + assert_se(eventfd_write(bfd, 1) >= 0); + + assert_se(wait_for_terminate_and_check("(test)", pid, WAIT_LOG) >= 0); + + return 0; +} + +DEFINE_MAIN_FUNCTION(run); 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