[v3,bpf-next,14/14] selftests/bpf: add BPF token-enabled BPF_PROG_LOAD tests

Commit Message

Andrii Nakryiko June 21, 2023, 11:38 p.m. UTC

Add a test validating that BPF token can be used to load privileged BPF
program using privileged BPF helpers through delegated BPF token created
by privileged process.

Signed-off-by: Andrii Nakryiko <[e-mail]>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 113cd4786a70..415d49eacd4f 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -4,6 +4,7 @@ 
 #include <test_progs.h>
 #include <bpf/btf.h>
 #include "cap_helpers.h"
+#include <linux/filter.h>
 
 static int drop_priv_caps(__u64 *old_caps)
 {
@@ -200,6 +201,69 @@  static void subtest_btf_token(void)
 		ASSERT_OK(restore_priv_caps(old_caps), "restore_caps");
 }
 
+static void subtest_prog_token(void)
+{
+	LIBBPF_OPTS(bpf_token_create_opts, token_opts);
+	LIBBPF_OPTS(bpf_prog_load_opts, prog_opts);
+	int token_fd = 0, prog_fd = 0, err;
+	__u64 old_caps = 0;
+	struct bpf_insn insns[] = {
+		/* bpf_jiffies64() requires CAP_BPF */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_jiffies64),
+		/* bpf_get_current_task() requires CAP_PERFMON */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_current_task),
+		/* r0 = 0; exit; */
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	size_t insn_cnt = ARRAY_SIZE(insns);
+
+	/* create BPF token allowing BPF_PROG_LOAD command */
+	token_opts.allowed_cmds = 1ULL << BPF_PROG_LOAD;
+	token_opts.allowed_prog_types = 1ULL << BPF_PROG_TYPE_XDP;
+	token_opts.allowed_attach_types = 1ULL << BPF_XDP;
+	err = bpf_token_create(-EBADF, TOKEN_PATH, &token_opts);
+	if (!ASSERT_OK(err, "token_create"))
+		return;
+
+	/* drop privileges to test token_fd passing */
+	if (!ASSERT_OK(drop_priv_caps(&old_caps), "drop_caps"))
+		goto cleanup;
+
+	token_fd = bpf_obj_get(TOKEN_PATH);
+	if (!ASSERT_GT(token_fd, 0, "token_get"))
+		goto cleanup;
+
+	/* validate we can successfully load BPF program with token; this
+	 * being XDP program (CAP_NET_ADMIN) using bpf_jiffies64() (CAP_BPF)
+	 * and bpf_get_current_task() (CAP_PERFMON) helpers validates we have
+	 * BPF token wired properly in a bunch of places in the kernel
+	 */
+	prog_opts.token_fd = token_fd;
+	prog_opts.expected_attach_type = BPF_XDP;
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_XDP, "token_prog", "GPL",
+				insns, insn_cnt, &prog_opts);
+	if (!ASSERT_GT(prog_fd, 0, "prog_fd"))
+		goto cleanup;
+	close(prog_fd);
+
+	/* now validate that we *cannot* load BPF program without token */
+	prog_opts.token_fd = 0;
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_XDP, "token_prog", "GPL",
+				insns, insn_cnt, &prog_opts);
+	if (!ASSERT_EQ(prog_fd, -EPERM, "prog_fd_eperm"))
+		goto cleanup;
+
+cleanup:
+	if (prog_fd > 0)
+		close(prog_fd);
+	if (token_fd)
+		close(token_fd);
+	unlink(TOKEN_PATH);
+	if (old_caps)
+		ASSERT_OK(restore_priv_caps(old_caps), "restore_caps");
+}
+
 void test_token(void)
 {
 	if (test__start_subtest("token_create"))
@@ -208,4 +272,6 @@  void test_token(void)
 		subtest_map_token();
 	if (test__start_subtest("btf_token"))
 		subtest_btf_token();
+	if (test__start_subtest("prog_token"))
+		subtest_prog_token();
 }