Ensure that signature verification is performed successfully from an eBPF
program, with the new bpf_verify_signature() helper.
Generate a testing signature key and copy sign-file from scripts/ to the
eBPF selftests directory (if exists), so that the test is selfcontained.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 11 +-
tools/testing/selftests/bpf/config | 1 +
.../selftests/bpf/prog_tests/verify_sig.c | 200 ++++++++++++++++++
.../selftests/bpf/progs/test_verify_sig.c | 160 ++++++++++++++
.../testing/selftests/bpf/verify_sig_setup.sh | 100 +++++++++
5 files changed, 469 insertions(+), 3 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/verify_sig.c
create mode 100644 tools/testing/selftests/bpf/progs/test_verify_sig.c
create mode 100755 tools/testing/selftests/bpf/verify_sig_setup.sh
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 2d3c8c8f558a..238911b4e4b4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -75,7 +75,7 @@ TEST_PROGS := test_kmod.sh \
test_xsk.sh
TEST_PROGS_EXTENDED := with_addr.sh \
- with_tunnels.sh ima_setup.sh \
+ with_tunnels.sh ima_setup.sh verify_sig_setup.sh \
test_xdp_vlan.sh test_bpftool.py
# Compile but not part of 'make run_tests'
@@ -84,7 +84,7 @@ TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
test_lirc_mode2_user xdping test_cpp runqslower bench bpf_testmod.ko \
xdpxceiver xdp_redirect_multi
-TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
+TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read $(OUTPUT)/sign-file
# Emit succinct information message describing current building step
# $1 - generic step name (e.g., CC, LINK, etc);
@@ -180,6 +180,10 @@ $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_r
liburandom_read.so $(LDLIBS) \
-Wl,-rpath=. -Wl,--build-id=sha1 -o $@
+$(OUTPUT)/sign-file: ../../../../scripts/sign-file
+ $(call msg,SIGN-FILE,,$@)
+ $(Q)$(shell [ -f $< ] && cp -a $< $@)
+
$(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
$(call msg,MOD,,$@)
$(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
@@ -502,7 +506,8 @@ TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c \
cap_helpers.c
TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read $(OUTPUT)/bpf_testmod.ko \
$(OUTPUT)/liburandom_read.so \
- ima_setup.sh \
+ $(OUTPUT)/sign-file \
+ ima_setup.sh verify_sig_setup.sh \
$(wildcard progs/btf_dump_test_case_*.c)
TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
TRUNNER_BPF_CFLAGS := $(BPF_CFLAGS) $(CLANG_CFLAGS) -DENABLE_ATOMICS_TESTS
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 3b3edc0fc8a6..64b0957d7742 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -57,3 +57,4 @@ CONFIG_FPROBE=y
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_MPTCP=y
+CONFIG_MODULE_SIG=y
diff --git a/tools/testing/selftests/bpf/prog_tests/verify_sig.c b/tools/testing/selftests/bpf/prog_tests/verify_sig.c
new file mode 100644
index 000000000000..165ab1a8ad98
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/verify_sig.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <endian.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <test_progs.h>
+
+#include "test_verify_sig.skel.h"
+
+#define MAX_DATA_SIZE 4096
+
+struct data {
+ u8 payload[MAX_DATA_SIZE];
+};
+
+static int _run_setup_process(const char *setup_dir, const char *cmd)
+{
+ int child_pid, child_status;
+
+ child_pid = fork();
+ if (child_pid == 0) {
+ execlp("./verify_sig_setup.sh", "./verify_sig_setup.sh", cmd,
+ setup_dir, NULL);
+ exit(errno);
+
+ } else if (child_pid > 0) {
+ waitpid(child_pid, &child_status, 0);
+ return WEXITSTATUS(child_status);
+ }
+
+ return -EINVAL;
+}
+
+static int populate_data_item(const char *tmp_dir, struct data *data_item)
+{
+ struct stat st;
+ char signed_file_template[] = "/tmp/signed_fileXXXXXX";
+ char path[PATH_MAX];
+ int ret, fd, child_status, child_pid;
+
+ fd = mkstemp(signed_file_template);
+ if (fd == -1)
+ return -errno;
+
+ ret = write(fd, "test", 4);
+
+ close(fd);
+
+ if (ret != 4) {
+ ret = -EIO;
+ goto out;
+ }
+
+ child_pid = fork();
+
+ if (child_pid == -1) {
+ ret = -errno;
+ goto out;
+ }
+
+ if (child_pid == 0) {
+ snprintf(path, sizeof(path), "%s/signing_key.pem", tmp_dir);
+
+ return execlp("./sign-file", "./sign-file", "sha256",
+ path, path, signed_file_template, NULL);
+ }
+
+ waitpid(child_pid, &child_status, 0);
+
+ ret = WEXITSTATUS(child_status);
+ if (ret)
+ goto out;
+
+ ret = stat(signed_file_template, &st);
+ if (ret == -1) {
+ ret = -errno;
+ goto out;
+ }
+
+ if (st.st_size > sizeof(data_item->payload) - sizeof(u32)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ *(u32 *)data_item->payload = __cpu_to_be32(st.st_size);
+
+ fd = open(signed_file_template, O_RDONLY);
+ if (fd == -1) {
+ ret = -errno;
+ goto out;
+ }
+
+ ret = read(fd, data_item->payload + sizeof(u32), st.st_size);
+
+ close(fd);
+
+ if (ret != st.st_size) {
+ ret = -EIO;
+ goto out;
+ }
+
+ ret = 0;
+out:
+ unlink(signed_file_template);
+ return ret;
+}
+
+void test_verify_sig(void)
+{
+ char tmp_dir_template[] = "/tmp/verify_sigXXXXXX";
+ char *tmp_dir;
+ struct test_verify_sig *skel = NULL;
+ struct bpf_map *map;
+ struct data data;
+ struct stat st;
+ u32 saved_len;
+ int ret, zero = 0;
+
+ if (libbpf_probe_bpf_helper(BPF_PROG_TYPE_KPROBE,
+ BPF_FUNC_verify_signature, NULL) == -EOPNOTSUPP) {
+ printf("%s:SKIP:bpf_verify_signature() helper not supported\n",
+ __func__);
+ test__skip();
+ return;
+ }
+
+ if (stat("./sign-file", &st) == -1) {
+ printf("%s:SKIP:kernel modules are not signed\n", __func__);
+ test__skip();
+ return;
+ }
+
+ tmp_dir = mkdtemp(tmp_dir_template);
+ if (!ASSERT_OK_PTR(tmp_dir, "mkdtemp"))
+ return;
+
+ ret = _run_setup_process(tmp_dir, "setup");
+ if (!ASSERT_OK(ret, "_run_setup_process"))
+ goto close_prog;
+
+ skel = test_verify_sig__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_verify_sig__open_and_load"))
+ goto close_prog;
+
+ ret = test_verify_sig__attach(skel);
+ if (!ASSERT_OK(ret, "test_verify_sig__attach\n"))
+ goto close_prog;
+
+ map = bpf_object__find_map_by_name(skel->obj, "data_input");
+ if (!ASSERT_OK_PTR(map, "data_input not found"))
+ goto close_prog;
+
+ ret = populate_data_item(tmp_dir, &data);
+ if (!ASSERT_OK(ret, "populate_data_item\n"))
+ goto close_prog;
+
+ skel->bss->monitored_pid = getpid();
+ skel->bss->keyring_id = 0xffff;
+
+ ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
+ if (!ASSERT_OK(ret, "bpf_map_update_elem\n"))
+ goto close_prog;
+
+ skel->bss->monitored_pid = getpid();
+ /* Search the verification key in the primary keyring (should fail). */
+ skel->bss->keyring_id = 0;
+
+ ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
+ if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input\n"))
+ goto close_prog;
+
+ saved_len = *(__u32 *)data.payload;
+ *(__u32 *)data.payload = sizeof(data.payload);
+ ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
+ if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input\n"))
+ goto close_prog;
+
+ *(__u32 *)data.payload = saved_len;
+ data.payload[sizeof(__u32)] = 'a';
+ ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
+ ASSERT_LT(ret, 0, "bpf_map_update_elem data_input\n");
+close_prog:
+ _run_setup_process(tmp_dir, "cleanup");
+
+ if (!skel)
+ return;
+
+ skel->bss->monitored_pid = 0;
+ test_verify_sig__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_verify_sig.c b/tools/testing/selftests/bpf/progs/test_verify_sig.c
new file mode 100644
index 000000000000..1c60c9b5c991
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_verify_sig.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+#define MAX_DATA_SIZE 4096
+
+#ifdef __BIG_ENDIAN__
+#define be32_to_cpu(x) (x)
+#else
+#define be32_to_cpu(x) ___bpf_swab32(x)
+#endif
+
+#define VERIFY_USE_SECONDARY_KEYRING (1UL)
+
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIG_STRING "~Module signature appended~\n"
+
+typedef __u8 u8;
+typedef __u16 u16;
+typedef __u32 u32;
+typedef __u64 u64;
+
+enum pkey_id_type {
+ PKEY_ID_PGP, /* OpenPGP generated key ID */
+ PKEY_ID_X509, /* X.509 arbitrary subjectKeyIdentifier */
+ PKEY_ID_PKCS7, /* Signature in PKCS#7 message */
+};
+
+/*
+ * Module signature information block.
+ *
+ * The constituents of the signature section are, in order:
+ *
+ * - Signer's name
+ * - Key identifier
+ * - Signature data
+ * - Information block
+ */
+struct module_signature {
+ u8 algo; /* Public-key crypto algorithm [0] */
+ u8 hash; /* Digest algorithm [0] */
+ u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */
+ u8 signer_len; /* Length of signer's name [0] */
+ u8 key_id_len; /* Length of key identifier [0] */
+ u8 __pad[3];
+ __be32 sig_len; /* Length of signature data */
+};
+
+u32 monitored_pid;
+u32 keyring_id;
+
+struct data {
+ u8 payload[MAX_DATA_SIZE];
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, struct data);
+} data_input SEC(".maps");
+
+char _license[] SEC("license") = "GPL";
+
+static int mod_check_sig(const struct module_signature *ms, size_t file_len)
+{
+ if (!ms)
+ return -ENOENT;
+
+ if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
+ return -EBADMSG;
+
+ if (ms->id_type != PKEY_ID_PKCS7)
+ return -ENOPKG;
+
+ if (ms->algo != 0 ||
+ ms->hash != 0 ||
+ ms->signer_len != 0 ||
+ ms->key_id_len != 0 ||
+ ms->__pad[0] != 0 ||
+ ms->__pad[1] != 0 ||
+ ms->__pad[2] != 0)
+ return -EBADMSG;
+
+ return 0;
+}
+
+SEC("lsm.s/bpf")
+int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
+{
+ const size_t marker_len = sizeof(MODULE_SIG_STRING) - 1;
+ char marker[sizeof(MODULE_SIG_STRING) - 1];
+ struct module_signature ms;
+ struct data *data_ptr;
+ u32 modlen;
+ u32 sig_len;
+ u64 value;
+ u8 *mod;
+ u32 pid;
+ int ret, zero = 0;
+
+ pid = bpf_get_current_pid_tgid() >> 32;
+ if (pid != monitored_pid)
+ return 0;
+
+ data_ptr = bpf_map_lookup_elem(&data_input, &zero);
+ if (!data_ptr)
+ return 0;
+
+ bpf_probe_read(&value, sizeof(value), &attr->value);
+
+ bpf_copy_from_user(data_ptr, sizeof(struct data),
+ (void *)(unsigned long)value);
+
+ modlen = be32_to_cpu(*(u32 *)data_ptr->payload);
+ mod = data_ptr->payload + sizeof(u32);
+
+ if (modlen > sizeof(struct data) - sizeof(u32))
+ return -EINVAL;
+
+ if (modlen <= marker_len)
+ return -ENOENT;
+
+ modlen &= sizeof(struct data) - 1;
+ bpf_probe_read(marker, marker_len, (char *)mod + modlen - marker_len);
+
+ if (bpf_strncmp(marker, marker_len, MODULE_SIG_STRING))
+ return -ENOENT;
+
+ modlen -= marker_len;
+
+ if (modlen <= sizeof(ms))
+ return -EBADMSG;
+
+ bpf_probe_read(&ms, sizeof(ms), (char *)mod + (modlen - sizeof(ms)));
+
+ ret = mod_check_sig(&ms, modlen);
+ if (ret)
+ return ret;
+
+ sig_len = be32_to_cpu(ms.sig_len);
+ modlen -= sig_len + sizeof(ms);
+
+ modlen &= 0x3ff;
+ sig_len &= 0x3ff;
+
+ return bpf_verify_signature(mod, modlen, mod + modlen, sig_len,
+ keyring_id + (PKEY_ID_PKCS7 << 16));
+}
diff --git a/tools/testing/selftests/bpf/verify_sig_setup.sh b/tools/testing/selftests/bpf/verify_sig_setup.sh
new file mode 100755
index 000000000000..48cb55abc4a4
--- /dev/null
+++ b/tools/testing/selftests/bpf/verify_sig_setup.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+set -u
+set -o pipefail
+
+VERBOSE="${SELFTESTS_VERBOSE:=0}"
+LOG_FILE="$(mktemp /tmp/verify_sig_setup.XXXX.log)"
+
+x509_genkey_content="\
+[ req ]
+default_bits = 2048
+distinguished_name = req_distinguished_name
+prompt = no
+string_mask = utf8only
+x509_extensions = myexts
+
+[ req_distinguished_name ]
+CN = eBPF Signature Verification Testing Key
+
+[ myexts ]
+basicConstraints=critical,CA:FALSE
+keyUsage=digitalSignature
+subjectKeyIdentifier=hash
+authorityKeyIdentifier=keyid
+"
+
+usage()
+{
+ echo "Usage: $0 <setup|cleanup <existing_tmp_dir>"
+ exit 1
+}
+
+setup()
+{
+ local tmp_dir="$1"
+
+ echo "${x509_genkey_content}" > ${tmp_dir}/x509.genkey
+
+ openssl req -new -nodes -utf8 -sha256 -days 36500 \
+ -batch -x509 -config ${tmp_dir}/x509.genkey \
+ -outform PEM -out ${tmp_dir}/signing_key.pem \
+ -keyout ${tmp_dir}/signing_key.pem 2>&1
+
+ openssl x509 -in ${tmp_dir}/signing_key.pem -out \
+ ${tmp_dir}/signing_key.der -outform der
+
+ cat ${tmp_dir}/signing_key.der | keyctl padd asymmetric ebpf_testing_key @s
+}
+
+cleanup() {
+ local tmp_dir="$1"
+
+ keyctl unlink $(keyctl search @s asymmetric ebpf_testing_key) @s
+ rm -rf ${tmp_dir}
+}
+
+catch()
+{
+ local exit_code="$1"
+ local log_file="$2"
+
+ if [[ "${exit_code}" -ne 0 ]]; then
+ cat "${log_file}" >&3
+ fi
+
+ rm -f "${log_file}"
+ exit ${exit_code}
+}
+
+main()
+{
+ [[ $# -ne 2 ]] && usage
+
+ local action="$1"
+ local tmp_dir="$2"
+
+ [[ ! -d "${tmp_dir}" ]] && echo "Directory ${tmp_dir} doesn't exist" && exit 1
+
+ if [[ "${action}" == "setup" ]]; then
+ setup "${tmp_dir}"
+ elif [[ "${action}" == "cleanup" ]]; then
+ cleanup "${tmp_dir}"
+ else
+ echo "Unknown action: ${action}"
+ exit 1
+ fi
+}
+
+trap 'catch "$?" "${LOG_FILE}"' EXIT
+
+if [[ "${VERBOSE}" -eq 0 ]]; then
+ # Save the stderr to 3 so that we can output back to
+ # it incase of an error.
+ exec 3>&2 1>"${LOG_FILE}" 2>&1
+fi
+
+main "$@"
+rm -f "${LOG_FILE}"
--
2.25.1
