// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2014 Google, Inc.
 *
 * Selftests for execveat(2).
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE  /* to get O_PATH, AT_EMPTY_PATH */
#endif
#include <sys/sendfile.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "kselftest.h"

#define TESTS_EXPECTED 54
#define TEST_NAME_LEN (PATH_MAX * 4)

#define CHECK_COMM "CHECK_COMM"

static char longpath[2 * PATH_MAX] = "";
static char *envp[] = { "IN_TEST=yes", NULL, NULL };
static char *argv[] = { "execveat", "99", NULL };

static int execveat_(int fd, const char *path, char **argv, char **envp,
                     int flags)
{
#ifdef __NR_execveat
        return syscall(__NR_execveat, fd, path, argv, envp, flags);
#else
        errno = ENOSYS;
        return -1;
#endif
}

#define check_execveat_fail(fd, path, flags, errno)     \
        _check_execveat_fail(fd, path, flags, errno, #errno)
static int _check_execveat_fail(int fd, const char *path, int flags,
                                int expected_errno, const char *errno_str)
{
        char test_name[TEST_NAME_LEN];
        int rc;

        errno = 0;
        snprintf(test_name, sizeof(test_name),
                 "Check failure of execveat(%d, '%s', %d) with %s",
                 fd, path?:"(null)", flags, errno_str);
        rc = execveat_(fd, path, argv, envp, flags);

        if (rc > 0) {
                ksft_print_msg("unexpected success from execveat(2)\n");
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        if (errno != expected_errno) {
                ksft_print_msg("expected errno %d (%s) not %d (%s)\n",
                               expected_errno, strerror(expected_errno),
                               errno, strerror(errno));
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        ksft_test_result_pass("%s\n", test_name);
        return 0;
}

static int check_execveat_invoked_rc(int fd, const char *path, int flags,
                                     int expected_rc, int expected_rc2)
{
        char test_name[TEST_NAME_LEN];
        int status;
        int rc;
        pid_t child;
        int pathlen = path ? strlen(path) : 0;

        if (pathlen > 40)
                snprintf(test_name, sizeof(test_name),
                         "Check success of execveat(%d, '%.20s...%s', %d)... ",
                         fd, path, (path + pathlen - 20), flags);
        else
                snprintf(test_name, sizeof(test_name),
                         "Check success of execveat(%d, '%s', %d)... ",
                         fd, path?:"(null)", flags);

        child = fork();
        if (child < 0) {
                ksft_perror("fork() failed");
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        if (child == 0) {
                /* Child: do execveat(). */
                rc = execveat_(fd, path, argv, envp, flags);
                ksft_print_msg("child execveat() failed, rc=%d errno=%d (%s)\n",
                               rc, errno, strerror(errno));
                exit(errno);
        }
        /* Parent: wait for & check child's exit status. */
        rc = waitpid(child, &status, 0);
        if (rc != child) {
                ksft_print_msg("waitpid(%d,...) returned %d\n", child, rc);
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        if (!WIFEXITED(status)) {
                ksft_print_msg("child %d did not exit cleanly, status=%08x\n",
                               child, status);
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        if ((WEXITSTATUS(status) != expected_rc) &&
            (WEXITSTATUS(status) != expected_rc2)) {
                ksft_print_msg("child %d exited with %d neither %d nor %d\n",
                               child, WEXITSTATUS(status), expected_rc,
                               expected_rc2);
                ksft_test_result_fail("%s\n", test_name);
                return 1;
        }
        ksft_test_result_pass("%s\n", test_name);
        return 0;
}

static int check_execveat(int fd, const char *path, int flags)
{
        return check_execveat_invoked_rc(fd, path, flags, 99, 99);
}

static char *concat(const char *left, const char *right)
{
        char *result = malloc(strlen(left) + strlen(right) + 1);

        strcpy(result, left);
        strcat(result, right);
        return result;
}

static int open_or_die(const char *filename, int flags)
{
        int fd = open(filename, flags);

        if (fd < 0)
                ksft_exit_fail_msg("Failed to open '%s'; "
                        "check prerequisites are available\n", filename);
        return fd;
}

static void exe_cp(const char *src, const char *dest)
{
        int in_fd = open_or_die(src, O_RDONLY);
        int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);
        struct stat info;

        fstat(in_fd, &info);
        sendfile(out_fd, in_fd, NULL, info.st_size);
        close(in_fd);
        close(out_fd);
}

#define XX_DIR_LEN 200
static int check_execveat_pathmax(int root_dfd, const char *src, int is_script)
{
        int fail = 0;
        int ii, count, len;
        char longname[XX_DIR_LEN + 1];
        int fd;

        if (*longpath == '\0') {
                /* Create a filename close to PATH_MAX in length */
                char *cwd = getcwd(NULL, 0);

                if (!cwd) {
                        ksft_perror("Failed to getcwd()");
                        return 2;
                }
                strcpy(longpath, cwd);
                strcat(longpath, "/");
                memset(longname, 'x', XX_DIR_LEN - 1);
                longname[XX_DIR_LEN - 1] = '/';
                longname[XX_DIR_LEN] = '\0';
                count = (PATH_MAX - 3 - strlen(cwd)) / XX_DIR_LEN;
                for (ii = 0; ii < count; ii++) {
                        strcat(longpath, longname);
                        mkdir(longpath, 0755);
                }
                len = (PATH_MAX - 3 - strlen(cwd)) - (count * XX_DIR_LEN);
                if (len <= 0)
                        len = 1;
                memset(longname, 'y', len);
                longname[len] = '\0';
                strcat(longpath, longname);
                free(cwd);
        }
        exe_cp(src, longpath);

        /*
         * Execute as a pre-opened file descriptor, which works whether this is
         * a script or not (because the interpreter sees a filename like
         * "/dev/fd/20").
         */
        fd = open(longpath, O_RDONLY);
        if (fd > 0) {
                ksft_print_msg("Invoke copy of '%s' via filename of length %zu:\n",
                               src, strlen(longpath));
                fail += check_execveat(fd, "", AT_EMPTY_PATH);
        } else {
                ksft_print_msg("Failed to open length %zu filename, errno=%d (%s)\n",
                               strlen(longpath), errno, strerror(errno));
                fail++;
        }

        /*
         * Execute as a long pathname relative to "/".  If this is a script,
         * the interpreter will launch but fail to open the script because its
         * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.
         *
         * The failure code is usually 127 (POSIX: "If a command is not found,
         * the exit status shall be 127."), but some systems give 126 (POSIX:
         * "If the command name is found, but it is not an executable utility,
         * the exit status shall be 126."), so allow either.
         */
        if (is_script) {
                ksft_print_msg("Invoke script via root_dfd and relative filename\n");
                fail += check_execveat_invoked_rc(root_dfd, longpath + 1, 0,
                                                  127, 126);
        } else {
                ksft_print_msg("Invoke exec via root_dfd and relative filename\n");
                fail += check_execveat(root_dfd, longpath + 1, 0);
        }

        return fail;
}

static int check_execveat_comm(int fd, char *argv0, char *expected)
{
        char buf[128], *old_env, *old_argv0;
        int ret;

        snprintf(buf, sizeof(buf), CHECK_COMM "=%s", expected);

        old_env = envp[1];
        envp[1] = buf;

        old_argv0 = argv[0];
        argv[0] = argv0;

        ksft_print_msg("Check execveat(AT_EMPTY_PATH)'s comm is %s\n",
                       expected);
        ret = check_execveat_invoked_rc(fd, "", AT_EMPTY_PATH, 0, 0);

        envp[1] = old_env;
        argv[0] = old_argv0;

        return ret;
}

static int run_tests(void)
{
        int fail = 0;
        char *fullname = realpath("execveat", NULL);
        char *fullname_script = realpath("script", NULL);
        char *fullname_symlink = concat(fullname, ".symlink");
        int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);
        int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",
                                               O_DIRECTORY|O_RDONLY);
        int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);
        int root_dfd = open_or_die("/", O_DIRECTORY|O_RDONLY);
        int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);
        int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
        int fd = open_or_die("execveat", O_RDONLY);
        int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);
        int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);
        int fd_denatured = open_or_die("execveat.denatured", O_RDONLY);
        int fd_denatured_path = open_or_die("execveat.denatured",
                                            O_RDONLY|O_PATH);
        int fd_script = open_or_die("script", O_RDONLY);
        int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
        int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",
                                            O_RDONLY|O_PATH);
        int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
        int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
        int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);

        /* Check if we have execveat at all, and bail early if not */
        errno = 0;
        execveat_(-1, NULL, NULL, NULL, 0);
        if (errno == ENOSYS) {
                ksft_exit_skip(
                        "ENOSYS calling execveat - no kernel support?\n");
        }

        /* Change file position to confirm it doesn't affect anything */
        lseek(fd, 10, SEEK_SET);

        /* Normal executable file: */
        /*   dfd + path */
        fail += check_execveat(subdir_dfd, "../execveat", 0);
        fail += check_execveat(dot_dfd, "execveat", 0);
        fail += check_execveat(dot_dfd_path, "execveat", 0);
        /*   absolute path */
        fail += check_execveat(AT_FDCWD, fullname, 0);
        /*   absolute path with nonsense dfd */
        fail += check_execveat(99, fullname, 0);
        /*   fd + no path */
        fail += check_execveat(fd, "", AT_EMPTY_PATH);
        /*   O_CLOEXEC fd + no path */
        fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);
        /*   O_PATH fd */
        fail += check_execveat(fd_path, "", AT_EMPTY_PATH);

        /* Mess with executable file that's already open: */
        /*   fd + no path to a file that's been renamed */
        rename("execveat.ephemeral", "execveat.moved");
        fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
        /*   fd + no path to a file that's been deleted */
        unlink("execveat.moved"); /* remove the file now fd open */
        fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);

        /* Mess with executable file that's already open with O_PATH */
        /*   fd + no path to a file that's been deleted */
        unlink("execveat.path.ephemeral");
        fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);

        /* Invalid argument failures */
        fail += check_execveat_fail(fd, "", 0, ENOENT);
        fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);

        /* Symlink to executable file: */
        /*   dfd + path */
        fail += check_execveat(dot_dfd, "execveat.symlink", 0);
        fail += check_execveat(dot_dfd_path, "execveat.symlink", 0);
        /*   absolute path */
        fail += check_execveat(AT_FDCWD, fullname_symlink, 0);
        /*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */
        fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH);
        fail += check_execveat(fd_symlink, "",
                               AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);

        /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */
        /*   dfd + path */
        fail += check_execveat_fail(dot_dfd, "execveat.symlink",
                                    AT_SYMLINK_NOFOLLOW, ELOOP);
        fail += check_execveat_fail(dot_dfd_path, "execveat.symlink",
                                    AT_SYMLINK_NOFOLLOW, ELOOP);
        /*   absolute path */
        fail += check_execveat_fail(AT_FDCWD, fullname_symlink,
                                    AT_SYMLINK_NOFOLLOW, ELOOP);

        /*  Non-regular file failure */
        fail += check_execveat_fail(dot_dfd, "pipe", 0, EACCES);
        unlink("pipe");

        /* Shell script wrapping executable file: */
        /*   dfd + path */
        fail += check_execveat(subdir_dfd, "../script", 0);
        fail += check_execveat(dot_dfd, "script", 0);
        fail += check_execveat(dot_dfd_path, "script", 0);
        /*   absolute path */
        fail += check_execveat(AT_FDCWD, fullname_script, 0);
        /*   fd + no path */
        fail += check_execveat(fd_script, "", AT_EMPTY_PATH);
        fail += check_execveat(fd_script, "",
                               AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
        /*   O_CLOEXEC fd fails for a script (as script file inaccessible) */
        fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,
                                    ENOENT);
        fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);

        /* Mess with script file that's already open: */
        /*   fd + no path to a file that's been renamed */
        rename("script.ephemeral", "script.moved");
        fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
        /*   fd + no path to a file that's been deleted */
        unlink("script.moved"); /* remove the file while fd open */
        fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);

        /* Rename a subdirectory in the path: */
        rename("subdir.ephemeral", "subdir.moved");
        fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
        fail += check_execveat(subdir_dfd_ephemeral, "script", 0);
        /* Remove the subdir and its contents */
        unlink("subdir.moved/script");
        unlink("subdir.moved");
        /* Shell loads via deleted subdir OK because name starts with .. */
        fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
        fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);

        /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */
        fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);
        /* Invalid path => ENOENT */
        fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);
        fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);
        fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);
        /* Attempt to execute directory => EACCES */
        fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);
        /* Attempt to execute non-executable => EACCES */
        fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
        fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
        fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
                                    EACCES);
        /* Attempt to execute nonsense FD => EBADF */
        fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF);
        fail += check_execveat_fail(99, "execveat", 0, EBADF);
        /* Attempt to execute relative to non-directory => ENOTDIR */
        fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR);

        fail += check_execveat_pathmax(root_dfd, "execveat", 0);
        fail += check_execveat_pathmax(root_dfd, "script", 1);

        /* /proc/pid/comm gives filename by default */
        fail += check_execveat_comm(fd, "sentinel", "execveat");
        /* /proc/pid/comm gives argv[0] when invoked via link */
        fail += check_execveat_comm(fd_symlink, "sentinel", "execveat");
        /* /proc/pid/comm gives filename if NULL is passed */
        fail += check_execveat_comm(fd, NULL, "execveat");

        return fail;
}

static void prerequisites(void)
{
        int fd;
        const char *script = "#!/bin/bash\nexit $*\n";

        /* Create ephemeral copies of files */
        exe_cp("execveat", "execveat.ephemeral");
        exe_cp("execveat", "execveat.path.ephemeral");
        exe_cp("script", "script.ephemeral");
        mkdir("subdir.ephemeral", 0755);

        fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);
        write(fd, script, strlen(script));
        close(fd);

        mkfifo("pipe", 0755);
}

int main(int argc, char **argv)
{
        int ii;
        int rc;
        const char *verbose = getenv("VERBOSE");
        const char *check_comm = getenv(CHECK_COMM);

        if (argc >= 2 || check_comm) {
                /*
                 * If we are invoked with an argument, or no arguments but a
                 * command to check, don't run tests.
                 */
                const char *in_test = getenv("IN_TEST");

                if (verbose) {
                        ksft_print_msg("invoked with:\n");
                        for (ii = 0; ii < argc; ii++)
                                ksft_print_msg("\t[%d]='%s\n'", ii, argv[ii]);
                }

                /* If the tests wanted us to check the command, do so. */
                if (check_comm) {
                        /* TASK_COMM_LEN == 16 */
                        char buf[32];
                        int fd, ret;

                        fd = open("/proc/self/comm", O_RDONLY);
                        if (fd < 0) {
                                ksft_perror("open() comm failed");
                                exit(1);
                        }

                        ret = read(fd, buf, sizeof(buf));
                        if (ret < 0) {
                                ksft_perror("read() comm failed");
                                close(fd);
                                exit(1);
                        }
                        close(fd);

                        // trim off the \n
                        buf[ret-1] = 0;

                        if (strcmp(buf, check_comm)) {
                                ksft_print_msg("bad comm, got: %s expected: %s\n",
                                               buf, check_comm);
                                exit(1);
                        }

                        exit(0);
                }

                /* Check expected environment transferred. */
                if (!in_test || strcmp(in_test, "yes") != 0) {
                        ksft_print_msg("no IN_TEST=yes in env\n");
                        return 1;
                }

                /* Use the final argument as an exit code. */
                rc = atoi(argv[argc - 1]);
                exit(rc);
        } else {
                ksft_print_header();
                ksft_set_plan(TESTS_EXPECTED);
                prerequisites();
                if (verbose)
                        envp[1] = "VERBOSE=1";
                rc = run_tests();
                if (rc > 0)
                        printf("%d tests failed\n", rc);
                ksft_finished();
        }

        return rc;
}