[PATCH bpf-next v5 7/7] bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM

[KP Singh]

From: KP Singh <kpsingh at google.com>

* Load/attach a BPF program to the file_mprotect (int) and
  bprm_committed_creds (void) LSM hooks.
* Perform an action that triggers the hook.
* Verify if the audit event was received using a shared global
  result variable.

Signed-off-by: KP Singh <kpsingh at google.com>
Reviewed-by: Brendan Jackman <jackmanb at google.com>
Reviewed-by: Florent Revest <revest at google.com>
Reviewed-by: Thomas Garnier <thgarnie at google.com>
---
 tools/testing/selftests/bpf/lsm_helpers.h     |  19 +++
 .../selftests/bpf/prog_tests/lsm_test.c       | 112 ++++++++++++++++++
 .../selftests/bpf/progs/lsm_int_hook.c        |  54 +++++++++
 .../selftests/bpf/progs/lsm_void_hook.c       |  41 +++++++
 4 files changed, 226 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/lsm_helpers.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/lsm_test.c
 create mode 100644 tools/testing/selftests/bpf/progs/lsm_int_hook.c
 create mode 100644 tools/testing/selftests/bpf/progs/lsm_void_hook.c

diff --git a/tools/testing/selftests/bpf/lsm_helpers.h b/tools/testing/selftests/bpf/lsm_helpers.h
new file mode 100644
index 000000000000..3de230df93db
--- /dev/null
+++ b/tools/testing/selftests/bpf/lsm_helpers.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+#ifndef _LSM_HELPERS_H
+#define _LSM_HELPERS_H
+
+struct lsm_prog_result {
+	/* This ensures that the LSM Hook only monitors the PID requested
+	 * by the loader
+	 */
+	__u32 monitored_pid;
+	/* The number of calls to the prog for the monitored PID.
+	 */
+	__u32 count;
+};
+
+#endif /* _LSM_HELPERS_H */
diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_test.c b/tools/testing/selftests/bpf/prog_tests/lsm_test.c
new file mode 100644
index 000000000000..5fd6b8f569f7
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/lsm_test.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+
+#include <test_progs.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <malloc.h>
+#include <stdlib.h>
+
+#include "lsm_helpers.h"
+#include "lsm_void_hook.skel.h"
+#include "lsm_int_hook.skel.h"
+
+char *LS_ARGS[] = {"true", NULL};
+
+int heap_mprotect(void)
+{
+	void *buf;
+	long sz;
+
+	sz = sysconf(_SC_PAGESIZE);
+	if (sz < 0)
+		return sz;
+
+	buf = memalign(sz, 2 * sz);
+	if (buf == NULL)
+		return -ENOMEM;
+
+	return mprotect(buf, sz, PROT_READ | PROT_EXEC);
+}
+
+int exec_ls(struct lsm_prog_result *result)
+{
+	int child_pid;
+
+	child_pid = fork();
+	if (child_pid == 0) {
+		result->monitored_pid = getpid();
+		execvp(LS_ARGS[0], LS_ARGS);
+		return -EINVAL;
+	} else if (child_pid > 0)
+		return wait(NULL);
+
+	return -EINVAL;
+}
+
+void test_lsm_void_hook(void)
+{
+	struct lsm_prog_result *result;
+	struct lsm_void_hook *skel = NULL;
+	int err, duration = 0;
+
+	skel = lsm_void_hook__open_and_load();
+	if (CHECK(!skel, "skel_load", "lsm_void_hook skeleton failed\n"))
+		goto close_prog;
+
+	err = lsm_void_hook__attach(skel);
+	if (CHECK(err, "attach", "lsm_void_hook attach failed: %d\n", err))
+		goto close_prog;
+
+	result = &skel->bss->result;
+
+	err = exec_ls(result);
+	if (CHECK(err < 0, "exec_ls", "err %d errno %d\n", err, errno))
+		goto close_prog;
+
+	if (CHECK(result->count != 1, "count", "count = %d", result->count))
+		goto close_prog;
+
+	CHECK_FAIL(result->count != 1);
+
+close_prog:
+	lsm_void_hook__destroy(skel);
+}
+
+void test_lsm_int_hook(void)
+{
+	struct lsm_prog_result *result;
+	struct lsm_int_hook *skel = NULL;
+	int err, duration = 0;
+
+	skel = lsm_int_hook__open_and_load();
+	if (CHECK(!skel, "skel_load", "lsm_int_hook skeleton failed\n"))
+		goto close_prog;
+
+	err = lsm_int_hook__attach(skel);
+	if (CHECK(err, "attach", "lsm_int_hook attach failed: %d\n", err))
+		goto close_prog;
+
+	result = &skel->bss->result;
+	result->monitored_pid = getpid();
+
+	err = heap_mprotect();
+	if (CHECK(errno != EPERM, "heap_mprotect", "want errno=EPERM, got %d\n",
+		  errno))
+		goto close_prog;
+
+	CHECK_FAIL(result->count != 1);
+
+close_prog:
+	lsm_int_hook__destroy(skel);
+}
+
+void test_lsm_test(void)
+{
+	test_lsm_void_hook();
+	test_lsm_int_hook();
+}
diff --git a/tools/testing/selftests/bpf/progs/lsm_int_hook.c b/tools/testing/selftests/bpf/progs/lsm_int_hook.c
new file mode 100644
index 000000000000..1c5028ddca61
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/lsm_int_hook.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <linux/bpf.h>
+#include <stdbool.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include  <errno.h>
+#include "lsm_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct lsm_prog_result result = {
+	.monitored_pid = 0,
+	.count = 0,
+};
+
+/*
+ * Define some of the structs used in the BPF program.
+ * Only the field names and their sizes need to be the
+ * same as the kernel type, the order is irrelevant.
+ */
+struct mm_struct {
+	unsigned long start_brk, brk;
+} __attribute__((preserve_access_index));
+
+struct vm_area_struct {
+	unsigned long vm_start, vm_end;
+	struct mm_struct *vm_mm;
+} __attribute__((preserve_access_index));
+
+SEC("lsm/file_mprotect")
+int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
+	     unsigned long reqprot, unsigned long prot, int ret)
+{
+	if (ret != 0)
+		return ret;
+
+	__u32 pid = bpf_get_current_pid_tgid();
+	int is_heap = 0;
+
+	is_heap = (vma->vm_start >= vma->vm_mm->start_brk &&
+		   vma->vm_end <= vma->vm_mm->brk);
+
+	if (is_heap && result.monitored_pid == pid) {
+		result.count++;
+		ret = -EPERM;
+	}
+
+	return ret;
+}
diff --git a/tools/testing/selftests/bpf/progs/lsm_void_hook.c b/tools/testing/selftests/bpf/progs/lsm_void_hook.c
new file mode 100644
index 000000000000..4d01a8536413
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/lsm_void_hook.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+
+#include <linux/bpf.h>
+#include <stdbool.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include  <errno.h>
+#include "lsm_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct lsm_prog_result result = {
+	.monitored_pid = 0,
+	.count = 0,
+};
+
+/*
+ * Define some of the structs used in the BPF program.
+ * Only the field names and their sizes need to be the
+ * same as the kernel type, the order is irrelevant.
+ */
+struct linux_binprm {
+	const char *filename;
+} __attribute__((preserve_access_index));
+
+SEC("lsm/bprm_committed_creds")
+int BPF_PROG(test_void_hook, struct linux_binprm *bprm)
+{
+	__u32 pid = bpf_get_current_pid_tgid();
+	char fmt[] = "lsm(bprm_committed_creds): process executed %s\n";
+
+	bpf_trace_printk(fmt, sizeof(fmt), bprm->filename);
+	if (result.monitored_pid == pid)
+		result.count++;
+
+	return 0;
+}
-- 
2.20.1