Re: [PATCH v2 4/6] selftests/bpf: Add test for bpf_ima_file_hash()

[Shuah Khan]

On 2/15/22 5:40 AM, Roberto Sassu wrote:
> Modify the existing IMA test to call bpf_ima_file_hash() and update the
> expected result accordingly.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
>   .../selftests/bpf/prog_tests/test_ima.c       | 29 ++++++++++++++++---
>   tools/testing/selftests/bpf/progs/ima.c       | 10 +++++--
>   2 files changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
> index 97d8a6f84f4a..62bf0e830453 100644
> --- a/tools/testing/selftests/bpf/prog_tests/test_ima.c
> +++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c
> @@ -13,9 +13,10 @@
>   
>   #include "ima.skel.h"
>   
> -static int run_measured_process(const char *measured_dir, u32 *monitored_pid)
> +static int run_measured_process(const char *measured_dir, u32 *monitored_pid,
> +				bool *use_ima_file_hash)
>   {
> -	int child_pid, child_status;
> +	int err, child_pid, child_status;
>   
>   	child_pid = fork();
>   	if (child_pid == 0) {
> @@ -24,6 +25,21 @@ static int run_measured_process(const char *measured_dir, u32 *monitored_pid)
>   		       NULL);
>   		exit(errno);
>   
> +	} else if (child_pid > 0) {
> +		waitpid(child_pid, &child_status, 0);
> +		err = WEXITSTATUS(child_status);
> +		if (err)
> +			return err;
> +	}
> +
> +	child_pid = fork();
> +	if (child_pid == 0) {
> +		*monitored_pid = getpid();
> +		*use_ima_file_hash = true;
> +		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);
> @@ -72,12 +88,17 @@ void test_test_ima(void)
>   	if (CHECK(err, "failed to run command", "%s, errno = %d\n", cmd, errno))
>   		goto close_clean;
>   
> -	err = run_measured_process(measured_dir, &skel->bss->monitored_pid);
> +	err = run_measured_process(measured_dir, &skel->bss->monitored_pid,
> +				   &skel->bss->use_ima_file_hash);
>   	if (CHECK(err, "run_measured_process", "err = %d\n", err))
>   		goto close_clean;
>   
>   	err = ring_buffer__consume(ringbuf);
> -	ASSERT_EQ(err, 1, "num_samples_or_err");
> +	/*
> +	 * 1 sample with use_ima_file_hash = false
> +	 * 2 samples with use_ima_file_hash = true (./ima_setup.sh, /bin/true)
> +	 */
> +	ASSERT_EQ(err, 3, "num_samples_or_err");
>   	ASSERT_NEQ(ima_hash_from_bpf, 0, "ima_hash");
>   
>   close_clean:
> diff --git a/tools/testing/selftests/bpf/progs/ima.c b/tools/testing/selftests/bpf/progs/ima.c
> index 96060ff4ffc6..9bb63f96cfc0 100644
> --- a/tools/testing/selftests/bpf/progs/ima.c
> +++ b/tools/testing/selftests/bpf/progs/ima.c
> @@ -18,6 +18,8 @@ struct {
>   
>   char _license[] SEC("license") = "GPL";
>   
> +bool use_ima_file_hash;
> +

This can be statis.

>   SEC("lsm.s/bprm_committed_creds")
>   void BPF_PROG(ima, struct linux_binprm *bprm)
>   {
> @@ -28,8 +30,12 @@ void BPF_PROG(ima, struct linux_binprm *bprm)
>   
>   	pid = bpf_get_current_pid_tgid() >> 32;
>   	if (pid == monitored_pid) {

I also noticed monitored_pid is defined in several bpf. Potentially
could be made static. This isn't introduced in this patch though.

> -		ret = bpf_ima_inode_hash(bprm->file->f_inode, &ima_hash,
> -					 sizeof(ima_hash));
> +		if (!use_ima_file_hash)
> +			ret = bpf_ima_inode_hash(bprm->file->f_inode, &ima_hash,
> +						 sizeof(ima_hash));
> +		else
> +			ret = bpf_ima_file_hash(bprm->file, &ima_hash,
> +						sizeof(ima_hash));
>   		if (ret < 0 || ima_hash == 0)
>   			return;
>   

thanks,
-- Shuah