1/* Copyright (C) 1991-2018 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
17
18#include <unistd.h>
19#include <stdarg.h>
20#include <stdbool.h>
21#include <stdlib.h>
22#include <string.h>
23#include <errno.h>
24#include <paths.h>
25#include <confstr.h>
26#include <sys/param.h>
27
28#ifndef PATH_MAX
29# ifdef MAXPATHLEN
30# define PATH_MAX MAXPATHLEN
31# else
32# define PATH_MAX 1024
33# endif
34#endif
35
36/* The file is accessible but it is not an executable file. Invoke
37 the shell to interpret it as a script. */
38static void
39maybe_script_execute (const char *file, char *const argv[], char *const envp[])
40{
41 ptrdiff_t argc;
42 for (argc = 0; argv[argc] != NULL; argc++)
43 {
44 if (argc == INT_MAX - 1)
45 {
46 errno = E2BIG;
47 return;
48 }
49 }
50
51 /* Construct an argument list for the shell based on original arguments:
52 1. Empty list (argv = { NULL }, argc = 1 }: new argv will contain 3
53 arguments - default shell, script to execute, and ending NULL.
54 2. Non empty argument list (argc = { ..., NULL }, argc > 1}: new argv
55 will contain also the default shell and the script to execute. It
56 will also skip the script name in arguments and only copy script
57 arguments. */
58 char *new_argv[argc > 1 ? 2 + argc : 3];
59 new_argv[0] = (char *) _PATH_BSHELL;
60 new_argv[1] = (char *) file;
61 if (argc > 1)
62 memcpy (new_argv + 2, argv + 1, argc * sizeof(char *));
63 else
64 new_argv[2] = NULL;
65
66 /* Execute the shell. */
67 __execve (new_argv[0], new_argv, envp);
68}
69
70
71/* Execute FILE, searching in the `PATH' environment variable if it contains
72 no slashes, with arguments ARGV and environment from ENVP. */
73int
74__execvpe (const char *file, char *const argv[], char *const envp[])
75{
76 /* We check the simple case first. */
77 if (*file == '\0')
78 {
79 __set_errno (ENOENT);
80 return -1;
81 }
82
83 /* Don't search when it contains a slash. */
84 if (strchr (file, '/') != NULL)
85 {
86 __execve (file, argv, envp);
87
88 if (errno == ENOEXEC)
89 maybe_script_execute (file, argv, envp);
90
91 return -1;
92 }
93
94 const char *path = getenv ("PATH");
95 if (!path)
96 path = CS_PATH;
97 /* Although GLIBC does not enforce NAME_MAX, we set it as the maximum
98 size to avoid unbounded stack allocation. Same applies for
99 PATH_MAX. */
100 size_t file_len = __strnlen (file, NAME_MAX) + 1;
101 size_t path_len = __strnlen (path, PATH_MAX - 1) + 1;
102
103 /* NAME_MAX does not include the terminating null character. */
104 if ((file_len - 1 > NAME_MAX)
105 || !__libc_alloca_cutoff (path_len + file_len + 1))
106 {
107 errno = ENAMETOOLONG;
108 return -1;
109 }
110
111 const char *subp;
112 bool got_eacces = false;
113 /* The resulting string maximum size would be potentially a entry
114 in PATH plus '/' (path_len + 1) and then the the resulting file name
115 plus '\0' (file_len since it already accounts for the '\0'). */
116 char buffer[path_len + file_len + 1];
117 for (const char *p = path; ; p = subp)
118 {
119 subp = __strchrnul (p, ':');
120
121 /* PATH is larger than PATH_MAX and thus potentially larger than
122 the stack allocation. */
123 if (subp - p >= path_len)
124 {
125 /* If there is only one path, bail out. */
126 if (*subp == '\0')
127 break;
128 /* Otherwise skip to next one. */
129 continue;
130 }
131
132 /* Use the current path entry, plus a '/' if nonempty, plus the file to
133 execute. */
134 char *pend = mempcpy (buffer, p, subp - p);
135 *pend = '/';
136 memcpy (pend + (p < subp), file, file_len);
137
138 __execve (buffer, argv, envp);
139
140 if (errno == ENOEXEC)
141 /* This has O(P*C) behavior, where P is the length of the path and C
142 is the argument count. A better strategy would be allocate the
143 substitute argv and reuse it each time through the loop (so it
144 behaves as O(P+C) instead. */
145 maybe_script_execute (buffer, argv, envp);
146
147 switch (errno)
148 {
149 case EACCES:
150 /* Record that we got a 'Permission denied' error. If we end
151 up finding no executable we can use, we want to diagnose
152 that we did find one but were denied access. */
153 got_eacces = true;
154 case ENOENT:
155 case ESTALE:
156 case ENOTDIR:
157 /* Those errors indicate the file is missing or not executable
158 by us, in which case we want to just try the next path
159 directory. */
160 case ENODEV:
161 case ETIMEDOUT:
162 /* Some strange filesystems like AFS return even
163 stranger error numbers. They cannot reasonably mean
164 anything else so ignore those, too. */
165 break;
166
167 default:
168 /* Some other error means we found an executable file, but
169 something went wrong executing it; return the error to our
170 caller. */
171 return -1;
172 }
173
174 if (*subp++ == '\0')
175 break;
176 }
177
178 /* We tried every element and none of them worked. */
179 if (got_eacces)
180 /* At least one failure was due to permissions, so report that
181 error. */
182 __set_errno (EACCES);
183
184 return -1;
185}
186
187weak_alias (__execvpe, execvpe)
188