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