[PATCH v3 bpf-next 03/14] selftests/bpf: add BPF_TOKEN_CREATE test

[Andrii Nakryiko]

Add a subtest validating BPF_TOKEN_CREATE command, pinning/getting BPF
token in/from BPF FS, and creating derived BPF tokens using token_fd
parameter.

Signed-off-by: Andrii Nakryiko <andrii at kernel.org>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 96 +++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/token.c

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
new file mode 100644
index 000000000000..153c4e26ef6b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+#include "linux/bpf.h"
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "cap_helpers.h"
+
+static int drop_priv_caps(__u64 *old_caps)
+{
+	return cap_disable_effective((1ULL << CAP_BPF) |
+				     (1ULL << CAP_PERFMON) |
+				     (1ULL << CAP_NET_ADMIN) |
+				     (1ULL << CAP_SYS_ADMIN), old_caps);
+}
+
+static int restore_priv_caps(__u64 old_caps)
+{
+	return cap_enable_effective(old_caps, NULL);
+}
+
+#define BPFFS_PATH "/sys/fs/bpf"
+#define TOKEN_PATH BPFFS_PATH "/test_token"
+
+static void subtest_token_create(void)
+{
+	LIBBPF_OPTS(bpf_token_create_opts, opts);
+	int token_fd = 0, limited_token_fd = 0, err;
+	__u64 old_caps = 0;
+
+	/* check that any current and future cmd can be specified */
+	opts.allowed_cmds = ~0ULL;
+	err = bpf_token_create(-EBADF, TOKEN_PATH, &opts);
+	if (!ASSERT_OK(err, "token_create_future_proof"))
+		return;
+	unlink(TOKEN_PATH);
+
+	/* create BPF token which allows creating derived BPF tokens */
+	opts.allowed_cmds = 1ULL << BPF_TOKEN_CREATE;
+	err = bpf_token_create(-EBADF, TOKEN_PATH, &opts);
+	if (!ASSERT_OK(err, "token_create"))
+		return;
+
+	token_fd = bpf_obj_get(TOKEN_PATH);
+	if (!ASSERT_GT(token_fd, 0, "token_get"))
+		goto cleanup;
+	unlink(TOKEN_PATH);
+
+	/* validate pinning and getting works as expected */
+	err = bpf_obj_pin(token_fd, TOKEN_PATH);
+	if (!ASSERT_ERR(err, "token_pin_unexpected_success"))
+		goto cleanup;
+
+
+	/* drop privileges to test token_fd passing */
+	if (!ASSERT_OK(drop_priv_caps(&old_caps), "drop_caps"))
+		goto cleanup;
+
+	/* unprivileged BPF_TOKEN_CREATE should fail */
+	err = bpf_token_create(-EBADF, TOKEN_PATH, NULL);
+	if (!ASSERT_ERR(err, "token_create_unpriv_fail"))
+		goto cleanup;
+
+	/* unprivileged BPF_TOKEN_CREATE using granted BPF token succeeds */
+	opts.allowed_cmds = 0; /* ask for BPF token which doesn't allow new tokens */
+	opts.token_fd = token_fd;
+	err = bpf_token_create(-EBADF, TOKEN_PATH, &opts);
+	if (!ASSERT_OK(limited_token_fd, "token_create_limited"))
+		goto cleanup;
+
+	limited_token_fd = bpf_obj_get(TOKEN_PATH);
+	if (!ASSERT_GT(limited_token_fd, 0, "token_get_limited"))
+		goto cleanup;
+	unlink(TOKEN_PATH);
+
+	/* creating yet another token using "limited" BPF token should fail */
+	opts.allowed_cmds = 0;
+	opts.token_fd = limited_token_fd;
+	err = bpf_token_create(-EBADF, TOKEN_PATH,  &opts);
+	if (!ASSERT_ERR(err, "token_create_from_lim_fail"))
+		goto cleanup;
+
+cleanup:
+	if (token_fd)
+		close(token_fd);
+	if (limited_token_fd)
+		close(limited_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"))
+		subtest_token_create();
+}
-- 
2.34.1