[PATCH bpf-next v6 7/8] bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM

KP Singh
2020-03-25T15:27:02Z

From: KP Singh <kpsingh@google.com>

* Load/attach a BPF program that hooks to file_mprotect (int)
and bprm_committed_creds (void).
* Perform an action that triggers the hook.
* Verify if the audit event was received using the shared global
variables for the process executed.
* Verify if the mprotect returns a -EPERM.

Signed-off-by: KP Singh <kpsingh@google.com>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
---
tools/testing/selftests/bpf/config | 2 +
.../selftests/bpf/prog_tests/test_lsm.c | 84 +++++++++++++++++++
tools/testing/selftests/bpf/progs/lsm.c | 48 +++++++++++
3 files changed, 134 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/test_lsm.c
create mode 100644 tools/testing/selftests/bpf/progs/lsm.c

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 5dc109f4c097..60e3ae5d4e48 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -35,3 +35,5 @@ CONFIG_MPLS_ROUTING=m
CONFIG_MPLS_IPTUNNEL=m
CONFIG_IPV6_SIT=m
CONFIG_BPF_JIT=y
+CONFIG_BPF_LSM=y
+CONFIG_SECURITY=y
diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
new file mode 100644
index 000000000000..eb5f5a017500
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
@@ -0,0 +1,84 @@
+// 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.skel.h"
+
+char *CMD_ARGS[] = {"true", NULL};
+
+int heap_mprotect(void)
+{
+ void *buf;
+ long sz;
+ int ret;
+
+ sz = sysconf(_SC_PAGESIZE);
+ if (sz < 0)
+ return sz;
+
+ buf = memalign(sz, 2 * sz);
+ if (buf == NULL)
+ return -ENOMEM;
+
+ ret = mprotect(buf, sz, PROT_READ | PROT_EXEC);
+ free(buf);
+ return ret;
+}
+
+int exec_cmd(int *monitored_pid)
+{
+ int child_pid;
+
+ child_pid = fork();
+ if (child_pid == 0) {
+ *monitored_pid = getpid();
+ execvp(CMD_ARGS[0], CMD_ARGS);
+ return -EINVAL;
+ } else if (child_pid > 0)
+ return wait(NULL);
+
+ return -EINVAL;
+}
+
+void test_test_lsm(void)
+{
+ struct lsm *skel = NULL;
+ int err, duration = 0;
+
+ skel = lsm__open_and_load();
+ if (CHECK(!skel, "skel_load", "lsm skeleton failed\n"))
+ goto close_prog;
+
+ err = lsm__attach(skel);
+ if (CHECK(err, "attach", "lsm attach failed: %d\n", err))
+ goto close_prog;
+
+ err = exec_cmd(&skel->bss->monitored_pid);
+ if (CHECK(err < 0, "exec_cmd", "err %d errno %d\n", err, errno))
+ goto close_prog;
+
+ CHECK(skel->bss->bprm_count != 1, "bprm_count", "bprm_count = %d",
+ skel->bss->bprm_count);
+
+ skel->bss->monitored_pid = getpid();
+
+ err = heap_mprotect();
+ if (CHECK(errno != EPERM, "heap_mprotect", "want errno=EPERM, got %d\n",
+ errno))
+ goto close_prog;
+
+ CHECK(skel->bss->mprotect_count != 1, "mprotect_count",
+ "mprotect_count = %d", skel->bss->mprotect_count);
+
+close_prog:
+ lsm__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c
new file mode 100644
index 000000000000..a4e3c223028d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/lsm.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+int monitored_pid = 0;
+int mprotect_count = 0;
+int bprm_count = 0;
+
+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() >> 32;
+ int is_heap = 0;
+
+ is_heap = (vma->vm_start >= vma->vm_mm->start_brk &&
+ vma->vm_end <= vma->vm_mm->brk);
+
+ if (is_heap && monitored_pid == pid) {
+ mprotect_count++;
+ ret = -EPERM;
+ }
+
+ return ret;
+}
+
+SEC("lsm/bprm_committed_creds")
+int BPF_PROG(test_void_hook, struct linux_binprm *bprm)
+{
+ __u32 pid = bpf_get_current_pid_tgid() >> 32;
+
+ if (monitored_pid == pid)
+ bprm_count++;
+
+ return 0;
+}
--
2.20.1