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/*
* Copyright (c) 2022 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
/*
* Test program to exercise seccomp(2) and ptrace(2) intercept code.
*
* Usage: test_ptrace [-d 1-3] [command]
*/
/* Ignore architecture restrictions and define this unilaterally. */
#define HAVE_PTRACE_INTERCEPT
#include "exec_ptrace.c"
static sig_atomic_t got_sigchld;
static int debug;
int sudo_debug_instance = SUDO_DEBUG_INSTANCE_INITIALIZER;
sudo_dso_public int main(int argc, char *argv[]);
static void
handler(int signo)
{
if (signo == SIGCHLD)
got_sigchld = 1;
}
void
intercept_closure_reset(struct intercept_closure *closure)
{
memset(closure, 0, sizeof(*closure));
}
bool
intercept_check_policy(const char *command, int argc, char **argv, int envc,
char **envp, const char *runcwd, int *oldcwd, void *v)
{
struct intercept_closure *closure = v;
struct stat sb1, sb2;
bool is_denied;
debug_decl(intercept_check_policy, SUDO_DEBUG_EXEC);
/* Fake policy decisions. */
is_denied = stat(command, &sb1) == 0 && stat("/usr/bin/who", &sb2) == 0 &&
sb1.st_ino == sb2.st_ino && sb1.st_dev == sb2.st_dev;
if (is_denied) {
sudo_debug_printf(SUDO_DEBUG_DIAG, "denied %s", command);
closure->state = POLICY_REJECT;
} else {
sudo_debug_printf(SUDO_DEBUG_DIAG, "allowed %s", command);
closure->state = POLICY_TEST;
}
*oldcwd = -1;
debug_return_bool(true);
}
static void
init_debug_files(struct sudo_conf_debug_file_list *file_list,
struct sudo_debug_file *file)
{
debug_decl(init_debug_files, SUDO_DEBUG_EXEC);
TAILQ_INIT(file_list);
switch (debug) {
case 0:
debug_return;
case 1:
file->debug_flags = (char *)"exec@diag";
break;
case 2:
file->debug_flags = (char *)"exec@info";
break;
default:
file->debug_flags = (char *)"exec@debug";
break;
}
file->debug_file = (char *)"/dev/stderr";
TAILQ_INSERT_HEAD(file_list, file, entries);
debug_return;
}
int
sudo_sigaction(int signo, struct sigaction *sa, struct sigaction *osa)
{
return sigaction(signo, sa, osa);
}
int
main(int argc, char *argv[])
{
struct sudo_conf_debug_file_list debug_files;
struct sudo_debug_file debug_file;
const char *base, *shell = _PATH_SUDO_BSHELL;
struct intercept_closure closure = { 0 };
const char *errstr;
sigset_t blocked, empty;
struct sigaction sa;
pid_t child, my_pid, pid, my_pgrp;
int ch, status;
debug_decl_vars(main, SUDO_DEBUG_MAIN);
initprogname(argc > 0 ? argv[0] : "test_ptrace");
if (!have_seccomp_action("trap"))
sudo_fatalx("SECCOMP_MODE_FILTER not available in this kernel");
while ((ch = getopt(argc, argv, "d:")) != -1) {
switch (ch) {
case 'd':
debug = sudo_strtonum(optarg, 1, INT_MAX, &errstr);
if (errstr != NULL)
sudo_fatalx(U_("%s: %s"), optarg, U_(errstr));
break;
default:
fprintf(stderr, "usage: %s [-d 1-3] [command]\n", getprogname());
return EXIT_FAILURE;
}
}
argc -= optind;
argv += optind;
if (argc > 0)
shell = argv[0];
base = strrchr(shell, '/');
base = base ? base + 1 : shell;
/* Set debug level based on the debug flag. */
init_debug_files(&debug_files, &debug_file);
sudo_debug_instance = sudo_debug_register(getprogname(),
NULL, NULL, &debug_files, -1);
if (sudo_debug_instance == SUDO_DEBUG_INSTANCE_ERROR)
return EXIT_FAILURE;
/* Block SIGCHLD and SIGUSR during critical section. */
sigemptyset(&empty);
sigemptyset(&blocked);
sigaddset(&blocked, SIGCHLD);
sigaddset(&blocked, SIGUSR1);
sigprocmask(SIG_BLOCK, &blocked, NULL);
/* Signal handler sets a flag for SIGCHLD, nothing for SIGUSR1. */
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = handler;
sigaction(SIGCHLD, &sa, NULL);
sigaction(SIGUSR1, &sa, NULL);
/* Fork a shell. */
my_pid = getpid();
my_pgrp = getpgrp();
child = fork();
switch (child) {
case -1:
sudo_fatal("fork");
case 0:
/* child */
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
sudo_fatal("%s", "unable to set no_new_privs bit");
if (!set_exec_filter())
_exit(EXIT_FAILURE);
/* Suspend child until tracer seizes control and sends SIGUSR1. */
sigsuspend(&empty);
execl(shell, base, NULL);
sudo_fatal("execl");
default:
/* Parent attaches to child and allows it to continue. */
if (exec_ptrace_seize(child) == -1)
return EXIT_FAILURE;
break;
}
/* Wait for SIGCHLD. */
for (;;) {
sigsuspend(&empty);
if (!got_sigchld)
continue;
got_sigchld = 0;
for (;;) {
do {
pid = waitpid(-1, &status, __WALL|WNOHANG);
} while (pid == -1 && errno == EINTR);
if (pid <= 0) {
if (pid == -1 && errno != ECHILD)
sudo_fatal("waitpid");
/* No child to wait for. */
break;
}
if (WIFEXITED(status)) {
sudo_debug_printf(SUDO_DEBUG_DIAG, "%d: exited %d",
(int)pid, WEXITSTATUS(status));
if (pid == child)
return WEXITSTATUS(status);
} else if (WIFSIGNALED(status)) {
sudo_debug_printf(SUDO_DEBUG_DIAG, "%d: killed by signal %d",
(int)pid, WTERMSIG(status));
if (pid == child)
return WTERMSIG(status) | 128;
} else if (WIFSTOPPED(status)) {
if (exec_ptrace_stopped(pid, status, &closure)) {
if (pid == child) {
sudo_suspend_parent(WSTOPSIG(status), my_pid,
my_pgrp, child, NULL, NULL);
if (kill(child, SIGCONT) != 0)
sudo_warn("kill(%d, SIGCONT)", (int)child);
}
}
} else {
sudo_fatalx("%d: unknown status 0x%x", (int)pid, status);
}
}
}
}
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