// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2020 ARM Limited
#define _GNU_SOURCE
#include <sys/auxv.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <setjmp.h>
#include <sched.h>
#include "../../kselftest_harness.h"
#include "helper.h"
#define PAC_COLLISION_ATTEMPTS 10
/*
* The kernel sets TBID by default. So bits 55 and above should remain
* untouched no matter what.
* The VA space size is 48 bits. Bigger is opt-in.
*/
#define PAC_MASK (~0xff80ffffffffffff)
#define ARBITRARY_VALUE (0x1234)
#define ASSERT_PAUTH_ENABLED() \
do { \
unsigned long hwcaps = getauxval(AT_HWCAP); \
/* data key instructions are not in NOP space. This prevents a SIGILL */ \
if (!(hwcaps & HWCAP_PACA)) \
SKIP(return, "PAUTH not enabled"); \
} while (0)
#define ASSERT_GENERIC_PAUTH_ENABLED() \
do { \
unsigned long hwcaps = getauxval(AT_HWCAP); \
/* generic key instructions are not in NOP space. This prevents a SIGILL */ \
if (!(hwcaps & HWCAP_PACG)) \
SKIP(return, "Generic PAUTH not enabled"); \
} while (0)
void sign_specific(struct signatures *sign, size_t val)
{
sign->keyia = keyia_sign(val);
sign->keyib = keyib_sign(val);
sign->keyda = keyda_sign(val);
sign->keydb = keydb_sign(val);
}
void sign_all(struct signatures *sign, size_t val)
{
sign->keyia = keyia_sign(val);
sign->keyib = keyib_sign(val);
sign->keyda = keyda_sign(val);
sign->keydb = keydb_sign(val);
sign->keyg = keyg_sign(val);
}
int n_same(struct signatures *old, struct signatures *new, int nkeys)
{
int res = 0;
res += old->keyia == new->keyia;
res += old->keyib == new->keyib;
res += old->keyda == new->keyda;
res += old->keydb == new->keydb;
if (nkeys == NKEYS)
res += old->keyg == new->keyg;
return res;
}
int n_same_single_set(struct signatures *sign, int nkeys)
{
size_t vals[nkeys];
int same = 0;
vals[0] = sign->keyia & PAC_MASK;
vals[1] = sign->keyib & PAC_MASK;
vals[2] = sign->keyda & PAC_MASK;
vals[3] = sign->keydb & PAC_MASK;
if (nkeys >= 4)
vals[4] = sign->keyg & PAC_MASK;
for (int i = 0; i < nkeys - 1; i++) {
for (int j = i + 1; j < nkeys; j++) {
if (vals[i] == vals[j])
same += 1;
}
}
return same;
}
int exec_sign_all(struct signatures *signed_vals, size_t val)
{
int new_stdin[2];
int new_stdout[2];
int status;
int i;
ssize_t ret;
pid_t pid;
cpu_set_t mask;
ret = pipe(new_stdin);
if (ret == -1) {
perror("pipe returned error");
return -1;
}
ret = pipe(new_stdout);
if (ret == -1) {
perror("pipe returned error");
return -1;
}
/*
* pin this process and all its children to a single CPU, so it can also
* guarantee a context switch with its child
*/
sched_getaffinity(0, sizeof(mask), &mask);
for (i = 0; i < sizeof(cpu_set_t); i++)
if (CPU_ISSET(i, &mask))
break;
CPU_ZERO(&mask);
CPU_SET(i, &mask);
sched_setaffinity(0, sizeof(mask), &mask);
pid = fork();
// child
if (pid == 0) {
dup2(new_stdin[0], STDIN_FILENO);
if (ret == -1) {
perror("dup2 returned error");
exit(1);
}
dup2(new_stdout[1], STDOUT_FILENO);
if (ret == -1) {
perror("dup2 returned error");
exit(1);
}
close(new_stdin[0]);
close(new_stdin[1]);
close(new_stdout[0]);
close(new_stdout[1]);
ret = execl("exec_target", "exec_target", (char *)NULL);
if (ret == -1) {
perror("exec returned error");
exit(1);
}
}
close(new_stdin[0]);
close(new_stdout[1]);
ret = write(new_stdin[1], &val, sizeof(size_t));
if (ret == -1) {
perror("write returned error");
return -1;
}
/*
* wait for the worker to finish, so that read() reads all data
* will also context switch with worker so that this function can be used
* for context switch tests
*/
waitpid(pid, &status, 0);
if (WIFEXITED(status) == 0) {
fprintf(stderr, "worker exited unexpectedly\n");
return -1;
}
if (WEXITSTATUS(status) != 0) {
fprintf(stderr, "worker exited with error\n");
return -1;
}
ret = read(new_stdout[0], signed_vals, sizeof(struct signatures));
if (ret == -1) {
perror("read returned error");
return -1;
}
return 0;
}
sigjmp_buf jmpbuf;
void pac_signal_handler(int signum, siginfo_t *si, void *uc)
{
if (signum == SIGSEGV || signum == SIGILL)
siglongjmp(jmpbuf, 1);
}
/* check that a corrupted PAC results in SIGSEGV or SIGILL */
TEST(corrupt_pac)
{
struct sigaction sa;
ASSERT_PAUTH_ENABLED();
if (sigsetjmp(jmpbuf, 1) == 0) {
sa.sa_sigaction = pac_signal_handler;
sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
sigemptyset(&sa.sa_mask);
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGILL, &sa, NULL);
pac_corruptor();
ASSERT_TRUE(0) TH_LOG("SIGSEGV/SIGILL signal did not occur");
}
}
/*
* There are no separate pac* and aut* controls so checking only the pac*
* instructions is sufficient
*/
TEST(pac_instructions_not_nop)
{
size_t keyia = 0;
size_t keyib = 0;
size_t keyda = 0;
size_t keydb = 0;
ASSERT_PAUTH_ENABLED();
for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
keyia |= keyia_sign(i) & PAC_MASK;
keyib |= keyib_sign(i) & PAC_MASK;
keyda |= keyda_sign(i) & PAC_MASK;
keydb |= keydb_sign(i) & PAC_MASK;
}
ASSERT_NE(0, keyia) TH_LOG("keyia instructions did nothing");
ASSERT_NE(0, keyib) TH_LOG("keyib instructions did nothing");
ASSERT_NE(0, keyda) TH_LOG("keyda instructions did nothing");
ASSERT_NE(0, keydb) TH_LOG("keydb instructions did nothing");
}
TEST(pac_instructions_not_nop_generic)
{
size_t keyg = 0;
ASSERT_GENERIC_PAUTH_ENABLED();
for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++)
keyg |= keyg_sign(i) & PAC_MASK;
ASSERT_NE(0, keyg) TH_LOG("keyg instructions did nothing");
}
TEST(single_thread_different_keys)
{
int same = 10;
int nkeys = NKEYS;
int tmp;
struct signatures signed_vals;
unsigned long hwcaps = getauxval(AT_HWCAP);
/* generic and data key instructions are not in NOP space. This prevents a SIGILL */
ASSERT_PAUTH_ENABLED();
if (!(hwcaps & HWCAP_PACG)) {
TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
nkeys = NKEYS - 1;
}
/*
* In Linux the PAC field can be up to 7 bits wide. Even if keys are
* different, there is about 5% chance for PACs to collide with
* different addresses. This chance rapidly increases with fewer bits
* allocated for the PAC (e.g. wider address). A comparison of the keys
* directly will be more reliable.
* All signed values need to be different at least once out of n
* attempts to be certain that the keys are different
*/
for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
if (nkeys == NKEYS)
sign_all(&signed_vals, i);
else
sign_specific(&signed_vals, i);
tmp = n_same_single_set(&signed_vals, nkeys);
if (tmp < same)
same = tmp;
}
ASSERT_EQ(0, same) TH_LOG("%d keys clashed every time", same);
}
/*
* fork() does not change keys. Only exec() does so call a worker program.
* Its only job is to sign a value and report back the resutls
*/
TEST(exec_changed_keys)
{
struct signatures new_keys;
struct signatures old_keys;
int ret;
int same = 10;
int nkeys = NKEYS;
unsigned long hwcaps = getauxval(AT_HWCAP);
/* generic and data key instructions are not in NOP space. This prevents a SIGILL */
ASSERT_PAUTH_ENABLED();
if (!(hwcaps & HWCAP_PACG)) {
TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
nkeys = NKEYS - 1;
}
for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
ret = exec_sign_all(&new_keys, i);
ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
if (nkeys == NKEYS)
sign_all(&old_keys, i);
else
sign_specific(&old_keys, i);
ret = n_same(&old_keys, &new_keys, nkeys);
if (ret < same)
same = ret;
}
ASSERT_EQ(0, same) TH_LOG("exec() did not change %d keys", same);
}
TEST(context_switch_keep_keys)
{
int ret;
struct signatures trash;
struct signatures before;
struct signatures after;
ASSERT_PAUTH_ENABLED();
sign_specific(&before, ARBITRARY_VALUE);
/* will context switch with a process with different keys at least once */
ret = exec_sign_all(&trash, ARBITRARY_VALUE);
ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
sign_specific(&after, ARBITRARY_VALUE);
ASSERT_EQ(before.keyia, after.keyia) TH_LOG("keyia changed after context switching");
ASSERT_EQ(before.keyib, after.keyib) TH_LOG("keyib changed after context switching");
ASSERT_EQ(before.keyda, after.keyda) TH_LOG("keyda changed after context switching");
ASSERT_EQ(before.keydb, after.keydb) TH_LOG("keydb changed after context switching");
}
TEST(context_switch_keep_keys_generic)
{
int ret;
struct signatures trash;
size_t before;
size_t after;
ASSERT_GENERIC_PAUTH_ENABLED();
before = keyg_sign(ARBITRARY_VALUE);
/* will context switch with a process with different keys at least once */
ret = exec_sign_all(&trash, ARBITRARY_VALUE);
ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
after = keyg_sign(ARBITRARY_VALUE);
ASSERT_EQ(before, after) TH_LOG("keyg changed after context switching");
}
TEST_HARNESS_MAIN
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