bpf: Add a selftest for bpf_ima_inode_hash

The test does the following:

- Mounts a loopback filesystem and appends the IMA policy to measure
  executions only on this file-system. Restricting the IMA policy to
  a particular filesystem prevents a system-wide IMA policy change.
- Executes an executable copied to this loopback filesystem.
- Calls the bpf_ima_inode_hash in the bprm_committed_creds hook and
  checks if the call succeeded and checks if a hash was calculated.

The test shells out to the added ima_setup.sh script as the setup is
better handled in a shell script and is more complicated to do in the
test program or even shelling out individual commands from C.

The list of required configs (i.e. IMA, SECURITYFS,
IMA_{WRITE,READ}_POLICY) for running this test are also updated.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com> (limit policy rule to loopback mount)
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201124151210.1081188-4-kpsingh@chromium.org

1 files changed, 74 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
new file mode 100644
index 000000000000..61fca681d524
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <test_progs.h>
+
+#include "ima.skel.h"
+
+static int run_measured_process(const char *measured_dir, u32 *monitored_pid)
+{
+	int child_pid, child_status;
+
+	child_pid = fork();
+	if (child_pid == 0) {
+		*monitored_pid = getpid();
+		execlp("./ima_setup.sh", "./ima_setup.sh", "run", measured_dir,
+		       NULL);
+		exit(errno);
+
+	} else if (child_pid > 0) {
+		waitpid(child_pid, &child_status, 0);
+		return WEXITSTATUS(child_status);
+	}
+
+	return -EINVAL;
+}
+
+void test_test_ima(void)
+{
+	char measured_dir_template[] = "/tmp/ima_measuredXXXXXX";
+	const char *measured_dir;
+	char cmd[256];
+
+	int err, duration = 0;
+	struct ima *skel = NULL;
+
+	skel = ima__open_and_load();
+	if (CHECK(!skel, "skel_load", "skeleton failed\n"))
+		goto close_prog;
+
+	err = ima__attach(skel);
+	if (CHECK(err, "attach", "attach failed: %d\n", err))
+		goto close_prog;
+
+	measured_dir = mkdtemp(measured_dir_template);
+	if (CHECK(measured_dir == NULL, "mkdtemp", "err %d\n", errno))
+		goto close_prog;
+
+	snprintf(cmd, sizeof(cmd), "./ima_setup.sh setup %s", measured_dir);
+	if (CHECK_FAIL(system(cmd)))
+		goto close_clean;
+
+	err = run_measured_process(measured_dir, &skel->bss->monitored_pid);
+	if (CHECK(err, "run_measured_process", "err = %d\n", err))
+		goto close_clean;
+
+	CHECK(skel->data->ima_hash_ret < 0, "ima_hash_ret",
+	      "ima_hash_ret = %ld\n", skel->data->ima_hash_ret);
+
+	CHECK(skel->bss->ima_hash == 0, "ima_hash",
+	      "ima_hash = %lu\n", skel->bss->ima_hash);
+
+close_clean:
+	snprintf(cmd, sizeof(cmd), "./ima_setup.sh cleanup %s", measured_dir);
+	CHECK_FAIL(system(cmd));
+close_prog:
+	ima__destroy(skel);
+}