1/*-
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/types.h>
31#include <sys/uio.h>
32
33#include <errno.h>
34#include <limits.h>
35#include <paths.h>
36#include <stdarg.h>
37#include <stdio.h>
38#include <stdlib.h>
39#include <string.h>
40#include <unistd.h>
41
42#include "private/FdPath.h"
43
44extern "C" char** environ;
45
46enum ExecVariant { kIsExecL, kIsExecLE, kIsExecLP };
47
48static int __execl(const char* name, const char* argv0, ExecVariant variant, va_list ap) {
49  // Count the arguments.
50  va_list count_ap;
51  va_copy(count_ap, ap);
52  size_t n = 1;
53  while (va_arg(count_ap, char*) != nullptr) {
54    ++n;
55  }
56  va_end(count_ap);
57
58  // Construct the new argv.
59  char* argv[n + 1];
60  argv[0] = const_cast<char*>(argv0);
61  n = 1;
62  while ((argv[n] = va_arg(ap, char*)) != nullptr) {
63    ++n;
64  }
65
66  // Collect the argp too.
67  char** argp = (variant == kIsExecLE) ? va_arg(ap, char**) : environ;
68
69  va_end(ap);
70
71  return (variant == kIsExecLP) ? execvp(name, argv) : execve(name, argv, argp);
72}
73
74int execl(const char* name, const char* arg, ...) {
75  va_list ap;
76  va_start(ap, arg);
77  int result = __execl(name, arg, kIsExecL, ap);
78  va_end(ap);
79  return result;
80}
81
82int execle(const char* name, const char* arg, ...) {
83  va_list ap;
84  va_start(ap, arg);
85  int result = __execl(name, arg, kIsExecLE, ap);
86  va_end(ap);
87  return result;
88}
89
90int execlp(const char* name, const char* arg, ...) {
91  va_list ap;
92  va_start(ap, arg);
93  int result = __execl(name, arg, kIsExecLP, ap);
94  va_end(ap);
95  return result;
96}
97
98int execv(const char* name, char* const* argv) {
99  return execve(name, argv, environ);
100}
101
102int execvp(const char* name, char* const* argv) {
103  return execvpe(name, argv, environ);
104}
105
106static int __exec_as_script(const char* buf, char* const* argv, char* const* envp) {
107  size_t arg_count = 1;
108  while (argv[arg_count] != nullptr) ++arg_count;
109
110  const char* script_argv[arg_count + 2];
111  script_argv[0] = "sh";
112  script_argv[1] = buf;
113  memcpy(script_argv + 2, argv + 1, arg_count * sizeof(char*));
114  return execve(_PATH_BSHELL, const_cast<char**>(script_argv), envp);
115}
116
117int execvpe(const char* name, char* const* argv, char* const* envp) {
118  // Do not allow null name.
119  if (name == nullptr || *name == '\0') {
120    errno = ENOENT;
121    return -1;
122  }
123
124  // If it's an absolute or relative path name, it's easy.
125  if (strchr(name, '/') && execve(name, argv, envp) == -1) {
126    if (errno == ENOEXEC) return __exec_as_script(name, argv, envp);
127    return -1;
128  }
129
130  // Get the path we're searching.
131  const char* path = getenv("PATH");
132  if (path == nullptr) path = _PATH_DEFPATH;
133
134  // Make a writable copy.
135  size_t len = strlen(path) + 1;
136  char writable_path[len];
137  memcpy(writable_path, path, len);
138
139  bool saw_EACCES = false;
140
141  // Try each element of $PATH in turn...
142  char* strsep_buf = writable_path;
143  const char* dir;
144  while ((dir = strsep(&strsep_buf, ":"))) {
145    // It's a shell path: double, leading and trailing colons
146    // mean the current directory.
147    if (*dir == '\0') dir = const_cast<char*>(".");
148
149    size_t dir_len = strlen(dir);
150    size_t name_len = strlen(name);
151
152    char buf[dir_len + 1 + name_len + 1];
153    mempcpy(mempcpy(mempcpy(buf, dir, dir_len), "/", 1), name, name_len + 1);
154
155    execve(buf, argv, envp);
156    switch (errno) {
157    case EISDIR:
158    case ELOOP:
159    case ENAMETOOLONG:
160    case ENOENT:
161    case ENOTDIR:
162      break;
163    case ENOEXEC:
164      return __exec_as_script(buf, argv, envp);
165    case EACCES:
166      saw_EACCES = true;
167      break;
168    default:
169      return -1;
170    }
171  }
172  if (saw_EACCES) errno = EACCES;
173  return -1;
174}
175
176int fexecve(int fd, char* const* argv, char* const* envp) {
177  // execveat with AT_EMPTY_PATH (>= 3.19) seems to offer no advantages.
178  execve(FdPath(fd).c_str(), argv, envp);
179  if (errno == ENOENT) errno = EBADF;
180  return -1;
181}
182