[PATCH v3 9/9] selftests/bpf: Check that bpf_kernel_read_file() denies reading IMA policy
From: Roberto Sassu <roberto.sassu@huawei.com>
Date: 2022-03-02 11:18:43
Also in:
bpf, linux-integrity, linux-kselftest, linux-security-module, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
Check that bpf_kernel_read_file() denies the reading of an IMA policy, by ensuring that ima_setup.sh exits with an error. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- .../selftests/bpf/prog_tests/test_ima.c | 17 +++++++++++++++++ tools/testing/selftests/bpf/progs/ima.c | 18 ++++++++++++++++++ 2 files changed, 35 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
index b13a141c4220..b13feceb38f1 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_ima.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c@@ -59,6 +59,7 @@ static void test_init(struct ima__bss *bss) bss->use_ima_file_hash = false; bss->enable_bprm_creds_for_exec = false; bss->enable_kernel_read_file = false; + bss->test_deny = false; } void test_test_ima(void)
@@ -200,6 +201,22 @@ void test_test_ima(void) ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash"); ASSERT_NEQ(ima_hash_from_bpf[1], 0, "ima_hash"); + /* + * Test #6 + * - Goal: ensure that the kernel_read_file hook denies an operation + * - Expected result: 0 samples + */ + test_init(skel->bss); + skel->bss->enable_kernel_read_file = true; + skel->bss->test_deny = true; + err = _run_measured_process(measured_dir, &skel->bss->monitored_pid, + "load-policy"); + if (CHECK(!err, "run_measured_process #6", "err = %d\n", err)) + goto close_clean; + + err = ring_buffer__consume(ringbuf); + ASSERT_EQ(err, 0, "num_samples_or_err"); + close_clean: snprintf(cmd, sizeof(cmd), "./ima_setup.sh cleanup %s", measured_dir); err = system(cmd);
diff --git a/tools/testing/selftests/bpf/progs/ima.c b/tools/testing/selftests/bpf/progs/ima.c
index e3ce943c5c3d..e16a2c208481 100644
--- a/tools/testing/selftests/bpf/progs/ima.c
+++ b/tools/testing/selftests/bpf/progs/ima.c@@ -21,6 +21,7 @@ char _license[] SEC("license") = "GPL"; bool use_ima_file_hash; bool enable_bprm_creds_for_exec; bool enable_kernel_read_file; +bool test_deny; static void ima_test_common(struct file *file) {
@@ -51,6 +52,17 @@ static void ima_test_common(struct file *file) return; } +static int ima_test_deny(void) +{ + u32 pid; + + pid = bpf_get_current_pid_tgid() >> 32; + if (pid == monitored_pid && test_deny) + return -EPERM; + + return 0; +} + SEC("lsm.s/bprm_committed_creds") void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm) {
@@ -71,6 +83,8 @@ SEC("lsm.s/kernel_read_file") int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id, bool contents) { + int ret; + if (!enable_kernel_read_file) return 0;
@@ -80,6 +94,10 @@ int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id, if (id != READING_POLICY) return 0; + ret = ima_test_deny(); + if (ret < 0) + return ret; + ima_test_common(file); return 0; }
--
2.32.0