// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
*
* Author: Roberto Sassu <[email protected]>
*/
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <endian.h>
#include <limits.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <linux/keyctl.h>
#include <sys/xattr.h>
#include <linux/fsverity.h>
#include <test_progs.h>
#include "test_verify_pkcs7_sig.skel.h"
#include "test_sig_in_xattr.skel.h"
#define MAX_DATA_SIZE (1024 * 1024)
#define MAX_SIG_SIZE 1024
#define VERIFY_USE_SECONDARY_KEYRING (1UL)
#define VERIFY_USE_PLATFORM_KEYRING (2UL)
#ifndef SHA256_DIGEST_SIZE
#define SHA256_DIGEST_SIZE 32
#endif
/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
#define MODULE_SIG_STRING "~Module signature appended~\n"
/*
* 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 */
};
struct data {
__u8 data[MAX_DATA_SIZE];
__u32 data_len;
__u8 sig[MAX_SIG_SIZE];
__u32 sig_len;
};
static bool kfunc_not_supported;
static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt,
va_list args)
{
if (level == LIBBPF_WARN)
vprintf(fmt, args);
if (strcmp(fmt, "libbpf: extern (func ksym) '%s': not found in kernel or module BTFs\n"))
return 0;
if (strcmp(va_arg(args, char *), "bpf_verify_pkcs7_signature"))
return 0;
kfunc_not_supported = true;
return 0;
}
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_str(const char *tmp_dir, struct data *data_item)
{
struct stat st;
char data_template[] = "/tmp/dataXXXXXX";
char path[PATH_MAX];
int ret, fd, child_status, child_pid;
data_item->data_len = 4;
memcpy(data_item->data, "test", data_item->data_len);
fd = mkstemp(data_template);
if (fd == -1)
return -errno;
ret = write(fd, data_item->data, data_item->data_len);
close(fd);
if (ret != data_item->data_len) {
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", "-d", "sha256",
path, path, data_template, NULL);
}
waitpid(child_pid, &child_status, 0);
ret = WEXITSTATUS(child_status);
if (ret)
goto out;
snprintf(path, sizeof(path), "%s.p7s", data_template);
ret = stat(path, &st);
if (ret == -1) {
ret = -errno;
goto out;
}
if (st.st_size > sizeof(data_item->sig)) {
ret = -EINVAL;
goto out_sig;
}
data_item->sig_len = st.st_size;
fd = open(path, O_RDONLY);
if (fd == -1) {
ret = -errno;
goto out_sig;
}
ret = read(fd, data_item->sig, data_item->sig_len);
close(fd);
if (ret != data_item->sig_len) {
ret = -EIO;
goto out_sig;
}
ret = 0;
out_sig:
unlink(path);
out:
unlink(data_template);
return ret;
}
static int populate_data_item_mod(struct data *data_item)
{
char mod_path[PATH_MAX], *mod_path_ptr;
struct stat st;
void *mod;
FILE *fp;
struct module_signature ms;
int ret, fd, modlen, marker_len, sig_len;
data_item->data_len = 0;
if (stat("/lib/modules", &st) == -1)
return 0;
/* Requires CONFIG_TCP_CONG_BIC=m. */
fp = popen("find /lib/modules/$(uname -r) -name tcp_bic.ko", "r");
if (!fp)
return 0;
mod_path_ptr = fgets(mod_path, sizeof(mod_path), fp);
pclose(fp);
if (!mod_path_ptr)
return 0;
mod_path_ptr = strchr(mod_path, '\n');
if (!mod_path_ptr)
return 0;
*mod_path_ptr = '\0';
if (stat(mod_path, &st) == -1)
return 0;
modlen = st.st_size;
marker_len = sizeof(MODULE_SIG_STRING) - 1;
fd = open(mod_path, O_RDONLY);
if (fd == -1)
return -errno;
mod = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
if (mod == MAP_FAILED)
return -errno;
if (strncmp(mod + modlen - marker_len, MODULE_SIG_STRING, marker_len)) {
ret = -EINVAL;
goto out;
}
modlen -= marker_len;
memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
sig_len = __be32_to_cpu(ms.sig_len);
modlen -= sig_len + sizeof(ms);
if (modlen > sizeof(data_item->data)) {
ret = -E2BIG;
goto out;
}
memcpy(data_item->data, mod, modlen);
data_item->data_len = modlen;
if (sig_len > sizeof(data_item->sig)) {
ret = -E2BIG;
goto out;
}
memcpy(data_item->sig, mod + modlen, sig_len);
data_item->sig_len = sig_len;
ret = 0;
out:
munmap(mod, st.st_size);
return ret;
}
static void test_verify_pkcs7_sig_from_map(void)
{
libbpf_print_fn_t old_print_cb;
char tmp_dir_template[] = "/tmp/verify_sigXXXXXX";
char *tmp_dir;
struct test_verify_pkcs7_sig *skel = NULL;
struct bpf_map *map;
struct data data;
int ret, zero = 0;
/* Trigger creation of session keyring. */
syscall(__NR_request_key, "keyring", "_uid.0", NULL,
KEY_SPEC_SESSION_KEYRING);
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_pkcs7_sig__open();
if (!ASSERT_OK_PTR(skel, "test_verify_pkcs7_sig__open"))
goto close_prog;
old_print_cb = libbpf_set_print(libbpf_print_cb);
ret = test_verify_pkcs7_sig__load(skel);
libbpf_set_print(old_print_cb);
if (ret < 0 && kfunc_not_supported) {
printf(
"%s:SKIP:bpf_verify_pkcs7_signature() kfunc not supported\n",
__func__);
test__skip();
goto close_prog;
}
if (!ASSERT_OK(ret, "test_verify_pkcs7_sig__load"))
goto close_prog;
ret = test_verify_pkcs7_sig__attach(skel);
if (!ASSERT_OK(ret, "test_verify_pkcs7_sig__attach"))
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;
skel->bss->monitored_pid = getpid();
/* Test without data and signature. */
skel->bss->user_keyring_serial = KEY_SPEC_SESSION_KEYRING;
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input"))
goto close_prog;
/* Test successful signature verification with session keyring. */
ret = populate_data_item_str(tmp_dir, &data);
if (!ASSERT_OK(ret, "populate_data_item_str"))
goto close_prog;
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_OK(ret, "bpf_map_update_elem data_input"))
goto close_prog;
/* Test successful signature verification with testing keyring. */
skel->bss->user_keyring_serial = syscall(__NR_request_key, "keyring",
"ebpf_testing_keyring", NULL,
KEY_SPEC_SESSION_KEYRING);
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_OK(ret, "bpf_map_update_elem data_input"))
goto close_prog;
/*
* Ensure key_task_permission() is called and rejects the keyring
* (no Search permission).
*/
syscall(__NR_keyctl, KEYCTL_SETPERM, skel->bss->user_keyring_serial,
0x37373737);
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input"))
goto close_prog;
syscall(__NR_keyctl, KEYCTL_SETPERM, skel->bss->user_keyring_serial,
0x3f3f3f3f);
/*
* Ensure key_validate() is called and rejects the keyring (key expired)
*/
syscall(__NR_keyctl, KEYCTL_SET_TIMEOUT,
skel->bss->user_keyring_serial, 1);
sleep(1);
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input"))
goto close_prog;
skel->bss->user_keyring_serial = KEY_SPEC_SESSION_KEYRING;
/* Test with corrupted data (signature verification should fail). */
data.data[0] = 'a';
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data, BPF_ANY);
if (!ASSERT_LT(ret, 0, "bpf_map_update_elem data_input"))
goto close_prog;
ret = populate_data_item_mod(&data);
if (!ASSERT_OK(ret, "populate_data_item_mod"))
goto close_prog;
/* Test signature verification with system keyrings. */
if (data.data_len) {
skel->bss->user_keyring_serial = 0;
skel->bss->system_keyring_id = 0;
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data,
BPF_ANY);
if (!ASSERT_OK(ret, "bpf_map_update_elem data_input"))
goto close_prog;
skel->bss->system_keyring_id = VERIFY_USE_SECONDARY_KEYRING;
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data,
BPF_ANY);
if (!ASSERT_OK(ret, "bpf_map_update_elem data_input"))
goto close_prog;
skel->bss->system_keyring_id = VERIFY_USE_PLATFORM_KEYRING;
ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &data,
BPF_ANY);
ASSERT_LT(ret, 0, "bpf_map_update_elem data_input");
}
close_prog:
_run_setup_process(tmp_dir, "cleanup");
if (!skel)
return;
skel->bss->monitored_pid = 0;
test_verify_pkcs7_sig__destroy(skel);
}
static int get_signature_size(const char *sig_path)
{
struct stat st;
if (stat(sig_path, &st) == -1)
return -1;
return st.st_size;
}
static int add_signature_to_xattr(const char *data_path, const char *sig_path)
{
char sig[MAX_SIG_SIZE] = {0};
int fd, size, ret;
if (sig_path) {
fd = open(sig_path, O_RDONLY);
if (fd < 0)
return -1;
size = read(fd, sig, MAX_SIG_SIZE);
close(fd);
if (size <= 0)
return -1;
} else {
/* no sig_path, just write 32 bytes of zeros */
size = 32;
}
ret = setxattr(data_path, "user.sig", sig, size, 0);
if (!ASSERT_OK(ret, "setxattr"))
return -1;
return 0;
}
static int test_open_file(struct test_sig_in_xattr *skel, char *data_path,
pid_t pid, bool should_success, char *name)
{
int ret;
skel->bss->monitored_pid = pid;
ret = open(data_path, O_RDONLY);
close(ret);
skel->bss->monitored_pid = 0;
if (should_success) {
if (!ASSERT_GE(ret, 0, name))
return -1;
} else {
if (!ASSERT_LT(ret, 0, name))
return -1;
}
return 0;
}
static void test_pkcs7_sig_fsverity(void)
{
char data_path[PATH_MAX];
char sig_path[PATH_MAX];
char tmp_dir_template[] = "/tmp/verify_sigXXXXXX";
char *tmp_dir;
struct test_sig_in_xattr *skel = NULL;
pid_t pid;
int ret;
tmp_dir = mkdtemp(tmp_dir_template);
if (!ASSERT_OK_PTR(tmp_dir, "mkdtemp"))
return;
snprintf(data_path, PATH_MAX, "%s/data-file", tmp_dir);
snprintf(sig_path, PATH_MAX, "%s/sig-file", tmp_dir);
ret = _run_setup_process(tmp_dir, "setup");
if (!ASSERT_OK(ret, "_run_setup_process"))
goto out;
ret = _run_setup_process(tmp_dir, "fsverity-create-sign");
if (ret) {
printf("%s: SKIP: fsverity [sign|enable] doesn't work.\n"
"To run this test, try enable CONFIG_FS_VERITY and enable FSVerity for the filesystem.\n",
__func__);
test__skip();
goto out;
}
skel = test_sig_in_xattr__open();
if (!ASSERT_OK_PTR(skel, "test_sig_in_xattr__open"))
goto out;
ret = get_signature_size(sig_path);
if (!ASSERT_GT(ret, 0, "get_signature_size"))
goto out;
skel->bss->sig_size = ret;
skel->bss->user_keyring_serial = syscall(__NR_request_key, "keyring",
"ebpf_testing_keyring", NULL,
KEY_SPEC_SESSION_KEYRING);
memcpy(skel->bss->digest, "FSVerity", 8);
ret = test_sig_in_xattr__load(skel);
if (!ASSERT_OK(ret, "test_sig_in_xattr__load"))
goto out;
ret = test_sig_in_xattr__attach(skel);
if (!ASSERT_OK(ret, "test_sig_in_xattr__attach"))
goto out;
pid = getpid();
/* Case 1: fsverity is not enabled, open should succeed */
if (test_open_file(skel, data_path, pid, true, "open_1"))
goto out;
/* Case 2: fsverity is enabled, xattr is missing, open should
* fail
*/
ret = _run_setup_process(tmp_dir, "fsverity-enable");
if (!ASSERT_OK(ret, "fsverity-enable"))
goto out;
if (test_open_file(skel, data_path, pid, false, "open_2"))
goto out;
/* Case 3: fsverity is enabled, xattr has valid signature, open
* should succeed
*/
ret = add_signature_to_xattr(data_path, sig_path);
if (!ASSERT_OK(ret, "add_signature_to_xattr_1"))
goto out;
if (test_open_file(skel, data_path, pid, true, "open_3"))
goto out;
/* Case 4: fsverity is enabled, xattr has invalid signature, open
* should fail
*/
ret = add_signature_to_xattr(data_path, NULL);
if (!ASSERT_OK(ret, "add_signature_to_xattr_2"))
goto out;
test_open_file(skel, data_path, pid, false, "open_4");
out:
_run_setup_process(tmp_dir, "cleanup");
if (!skel)
return;
skel->bss->monitored_pid = 0;
test_sig_in_xattr__destroy(skel);
}
void test_verify_pkcs7_sig(void)
{
if (test__start_subtest("pkcs7_sig_from_map"))
test_verify_pkcs7_sig_from_map();
if (test__start_subtest("pkcs7_sig_fsverity"))
test_pkcs7_sig_fsverity();
}
Codebase Browser
linux