Verify that bpf_ima_inode_hash() returns a non-fresh digest after a file write, and that bpf_ima_file_hash() returns a fresh digest. Verification is done by requesting the digest from the bprm_creds_for_exec hook, called before ima_bprm_check().
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/testing/selftests/bpf/ima_setup.sh | 24 ++++++- .../selftests/bpf/prog_tests/test_ima.c | 72 ++++++++++++++++++- tools/testing/selftests/bpf/progs/ima.c | 11 +++ 3 files changed, 103 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/bpf/ima_setup.sh b/tools/testing/selftests/bpf/ima_setup.sh index 8e62581113a3..a3de1cd43ba0 100755 --- a/tools/testing/selftests/bpf/ima_setup.sh +++ b/tools/testing/selftests/bpf/ima_setup.sh @@ -12,7 +12,7 @@ LOG_FILE="$(mktemp /tmp/ima_setup.XXXX.log)"
usage() { - echo "Usage: $0 <setup|cleanup|run> <existing_tmp_dir>" + echo "Usage: $0 <setup|cleanup|run|modify-bin|restore-bin> <existing_tmp_dir>" exit 1 }
@@ -77,6 +77,24 @@ run() exec "${copied_bin_path}" }
+modify_bin() +{ + local tmp_dir="$1" + local mount_dir="${tmp_dir}/mnt" + local copied_bin_path="${mount_dir}/$(basename ${TEST_BINARY})" + + echo "mod" >> "${copied_bin_path}" +} + +restore_bin() +{ + local tmp_dir="$1" + local mount_dir="${tmp_dir}/mnt" + local copied_bin_path="${mount_dir}/$(basename ${TEST_BINARY})" + + truncate -s -4 "${copied_bin_path}" +} + catch() { local exit_code="$1" @@ -105,6 +123,10 @@ main() cleanup "${tmp_dir}" elif [[ "${action}" == "run" ]]; then run "${tmp_dir}" + elif [[ "${action}" == "modify-bin" ]]; then + modify_bin "${tmp_dir}" + elif [[ "${action}" == "restore-bin" ]]; then + restore_bin "${tmp_dir}" else echo "Unknown action: ${action}" exit 1 diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c index acc911ba63fd..a0cfba0b4273 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_ima.c +++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c @@ -13,16 +13,17 @@
#include "ima.skel.h"
-#define MAX_SAMPLES 2 +#define MAX_SAMPLES 4
-static int run_measured_process(const char *measured_dir, u32 *monitored_pid) +static int _run_measured_process(const char *measured_dir, u32 *monitored_pid, + const char *cmd) { 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, + execlp("./ima_setup.sh", "./ima_setup.sh", cmd, measured_dir, NULL); exit(errno);
@@ -34,6 +35,11 @@ static int run_measured_process(const char *measured_dir, u32 *monitored_pid) return -EINVAL; }
+static int run_measured_process(const char *measured_dir, u32 *monitored_pid) +{ + return _run_measured_process(measured_dir, monitored_pid, "run"); +} + static u64 ima_hash_from_bpf[MAX_SAMPLES]; static int ima_hash_from_bpf_idx;
@@ -51,6 +57,7 @@ static void test_init(struct ima__bss *bss) ima_hash_from_bpf_idx = 0;
bss->use_ima_file_hash = false; + bss->enable_bprm_creds_for_exec = false; }
void test_test_ima(void) @@ -58,6 +65,7 @@ void test_test_ima(void) char measured_dir_template[] = "/tmp/ima_measuredXXXXXX"; struct ring_buffer *ringbuf = NULL; const char *measured_dir; + u64 bin_true_sample; char cmd[256];
int err, duration = 0; @@ -114,6 +122,64 @@ void test_test_ima(void) ASSERT_EQ(err, 2, "num_samples_or_err"); ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash"); ASSERT_NEQ(ima_hash_from_bpf[1], 0, "ima_hash"); + bin_true_sample = ima_hash_from_bpf[1]; + + /* + * Test #3 + * - Goal: confirm that bpf_ima_inode_hash() returns a non-fresh digest + * - Expected result: 2 samples (/bin/true: non-fresh, fresh) + */ + test_init(skel->bss); + + err = _run_measured_process(measured_dir, &skel->bss->monitored_pid, + "modify-bin"); + if (CHECK(err, "modify-bin #3", "err = %d\n", err)) + goto close_clean; + + skel->bss->enable_bprm_creds_for_exec = true; + err = run_measured_process(measured_dir, &skel->bss->monitored_pid); + if (CHECK(err, "run_measured_process #3", "err = %d\n", err)) + goto close_clean; + + err = ring_buffer__consume(ringbuf); + ASSERT_EQ(err, 2, "num_samples_or_err"); + ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash"); + ASSERT_NEQ(ima_hash_from_bpf[1], 0, "ima_hash"); + ASSERT_EQ(ima_hash_from_bpf[0], bin_true_sample, "sample_equal_or_err"); + /* IMA refreshed the digest. */ + ASSERT_NEQ(ima_hash_from_bpf[1], bin_true_sample, + "sample_different_or_err"); + + /* + * Test #4 + * - Goal: verify that bpf_ima_file_hash() returns a fresh digest + * - Expected result: 4 samples (./ima_setup.sh: fresh, fresh; + * /bin/true: fresh, fresh) + */ + test_init(skel->bss); + skel->bss->use_ima_file_hash = true; + skel->bss->enable_bprm_creds_for_exec = true; + err = run_measured_process(measured_dir, &skel->bss->monitored_pid); + if (CHECK(err, "run_measured_process #4", "err = %d\n", err)) + goto close_clean; + + err = ring_buffer__consume(ringbuf); + ASSERT_EQ(err, 4, "num_samples_or_err"); + ASSERT_NEQ(ima_hash_from_bpf[0], 0, "ima_hash"); + ASSERT_NEQ(ima_hash_from_bpf[1], 0, "ima_hash"); + ASSERT_NEQ(ima_hash_from_bpf[2], 0, "ima_hash"); + ASSERT_NEQ(ima_hash_from_bpf[3], 0, "ima_hash"); + ASSERT_NEQ(ima_hash_from_bpf[2], bin_true_sample, + "sample_different_or_err"); + ASSERT_EQ(ima_hash_from_bpf[3], ima_hash_from_bpf[2], + "sample_equal_or_err"); + + skel->bss->use_ima_file_hash = false; + skel->bss->enable_bprm_creds_for_exec = false; + err = _run_measured_process(measured_dir, &skel->bss->monitored_pid, + "restore-bin"); + if (CHECK(err, "restore-bin #3", "err = %d\n", err)) + goto close_clean;
close_clean: snprintf(cmd, sizeof(cmd), "./ima_setup.sh cleanup %s", measured_dir); diff --git a/tools/testing/selftests/bpf/progs/ima.c b/tools/testing/selftests/bpf/progs/ima.c index e0b073dcfb5d..9633e5f2453d 100644 --- a/tools/testing/selftests/bpf/progs/ima.c +++ b/tools/testing/selftests/bpf/progs/ima.c @@ -19,6 +19,7 @@ struct { char _license[] SEC("license") = "GPL";
bool use_ima_file_hash; +bool enable_bprm_creds_for_exec;
static void ima_test_common(struct file *file) { @@ -54,3 +55,13 @@ void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm) { ima_test_common(bprm->file); } + +SEC("lsm.s/bprm_creds_for_exec") +int BPF_PROG(bprm_creds_for_exec, struct linux_binprm *bprm) +{ + if (!enable_bprm_creds_for_exec) + return 0; + + ima_test_common(bprm->file); + return 0; +}