From cc374782b6ca0fd634482391da977542443d3368 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
Date: Wed, 24 Jul 2024 16:54:26 +0200
Subject: [PATCH] selftests/landlock: Add cred_transfer test
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Check that keyctl(KEYCTL_SESSION_TO_PARENT) preserves the parent's
restrictions.
Fixes: e1199815b47b ("selftests/landlock: Add user space tests")
Co-developed-by: Jann Horn <jannh@google.com>
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20240724.Ood5aige9she@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
tools/testing/selftests/landlock/base_test.c | 74 ++++++++++++++++++++
tools/testing/selftests/landlock/config | 1 +
2 files changed, 75 insertions(+)
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 3c1e9f35b5312..3b26bf3cf5b9a 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -9,6 +9,7 @@
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
+#include <linux/keyctl.h>
#include <linux/landlock.h>
#include <string.h>
#include <sys/prctl.h>
@@ -326,4 +327,77 @@ TEST(ruleset_fd_transfer)
ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
}
+TEST(cred_transfer)
+{
+ struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_fs = LANDLOCK_ACCESS_FS_READ_DIR,
+ };
+ int ruleset_fd, dir_fd;
+ pid_t child;
+ int status;
+
+ drop_caps(_metadata);
+
+ dir_fd = open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+ EXPECT_LE(0, dir_fd);
+ EXPECT_EQ(0, close(dir_fd));
+
+ /* Denies opening directories. */
+ ruleset_fd =
+ landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ EXPECT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+ ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+ EXPECT_EQ(0, close(ruleset_fd));
+
+ /* Checks ruleset enforcement. */
+ EXPECT_EQ(-1, open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+ EXPECT_EQ(EACCES, errno);
+
+ /* Needed for KEYCTL_SESSION_TO_PARENT permission checks */
+ EXPECT_NE(-1, syscall(__NR_keyctl, KEYCTL_JOIN_SESSION_KEYRING, NULL, 0,
+ 0, 0))
+ {
+ TH_LOG("Failed to join session keyring: %s", strerror(errno));
+ }
+
+ child = fork();
+ ASSERT_LE(0, child);
+ if (child == 0) {
+ /* Checks ruleset enforcement. */
+ EXPECT_EQ(-1, open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+ EXPECT_EQ(EACCES, errno);
+
+ /*
+ * KEYCTL_SESSION_TO_PARENT is a no-op unless we have a
+ * different session keyring in the child, so make that happen.
+ */
+ EXPECT_NE(-1, syscall(__NR_keyctl, KEYCTL_JOIN_SESSION_KEYRING,
+ NULL, 0, 0, 0));
+
+ /*
+ * KEYCTL_SESSION_TO_PARENT installs credentials on the parent
+ * that never go through the cred_prepare hook, this path uses
+ * cred_transfer instead.
+ */
+ EXPECT_EQ(0, syscall(__NR_keyctl, KEYCTL_SESSION_TO_PARENT, 0,
+ 0, 0, 0));
+
+ /* Re-checks ruleset enforcement. */
+ EXPECT_EQ(-1, open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+ EXPECT_EQ(EACCES, errno);
+
+ _exit(_metadata->exit_code);
+ return;
+ }
+
+ EXPECT_EQ(child, waitpid(child, &status, 0));
+ EXPECT_EQ(1, WIFEXITED(status));
+ EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
+
+ /* Re-checks ruleset enforcement. */
+ EXPECT_EQ(-1, open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+ EXPECT_EQ(EACCES, errno);
+}
+
TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/landlock/config b/tools/testing/selftests/landlock/config
index 0086efaa7b681..29af19c4e9f98 100644
--- a/tools/testing/selftests/landlock/config
+++ b/tools/testing/selftests/landlock/config
@@ -2,6 +2,7 @@ CONFIG_CGROUPS=y
CONFIG_CGROUP_SCHED=y
CONFIG_INET=y
CONFIG_IPV6=y
+CONFIG_KEYS=y
CONFIG_NET=y
CONFIG_NET_NS=y
CONFIG_OVERLAY_FS=y
--
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