1 /* Auxiliary functions for the creation of subprocesses. Native Windows API.
2 Copyright (C) 2001, 2003-2012 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2003.
4
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
17
18 /* Get declarations of the native Windows API functions. */
19 #define WIN32_LEAN_AND_MEAN
20 #include <windows.h>
21
22 /* Get _open_osfhandle(). */
23 #include <io.h>
24
25 #include <stdbool.h>
26 #include <string.h>
27 #include <unistd.h>
28 #include <errno.h>
29
30 /* Get _get_osfhandle(). */
31 #include "msvc-nothrow.h"
32
33 #include "cloexec.h"
34 #include "xalloc.h"
35
36 /* Duplicates a file handle, making the copy uninheritable.
37 Returns -1 for a file handle that is equivalent to closed. */
38 static int
dup_noinherit(int fd)39 dup_noinherit (int fd)
40 {
41 fd = dup_cloexec (fd);
42 if (fd < 0 && errno == EMFILE)
43 error (EXIT_FAILURE, errno, _("_open_osfhandle failed"));
44
45 return fd;
46 }
47
48 /* Returns a file descriptor equivalent to FD, except that the resulting file
49 descriptor is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
50 FD must be open and non-inheritable. The result will be non-inheritable as
51 well.
52 If FD < 0, FD itself is returned. */
53 static int
fd_safer_noinherit(int fd)54 fd_safer_noinherit (int fd)
55 {
56 if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
57 {
58 /* The recursion depth is at most 3. */
59 int nfd = fd_safer_noinherit (dup_noinherit (fd));
60 int saved_errno = errno;
61 close (fd);
62 errno = saved_errno;
63 return nfd;
64 }
65 return fd;
66 }
67
68 /* Duplicates a file handle, making the copy uninheritable and ensuring the
69 result is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
70 Returns -1 for a file handle that is equivalent to closed. */
71 static int
dup_safer_noinherit(int fd)72 dup_safer_noinherit (int fd)
73 {
74 return fd_safer_noinherit (dup_noinherit (fd));
75 }
76
77 /* Undoes the effect of TEMPFD = dup_safer_noinherit (ORIGFD); */
78 static void
undup_safer_noinherit(int tempfd,int origfd)79 undup_safer_noinherit (int tempfd, int origfd)
80 {
81 if (tempfd >= 0)
82 {
83 if (dup2 (tempfd, origfd) < 0)
84 error (EXIT_FAILURE, errno, _("cannot restore fd %d: dup2 failed"),
85 origfd);
86 close (tempfd);
87 }
88 else
89 {
90 /* origfd was closed or open to no handle at all. Set it to a closed
91 state. This is (nearly) equivalent to the original state. */
92 close (origfd);
93 }
94 }
95
96 /* Prepares an argument vector before calling spawn().
97 Note that spawn() does not by itself call the command interpreter
98 (getenv ("COMSPEC") != NULL ? getenv ("COMSPEC") :
99 ({ OSVERSIONINFO v; v.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
100 GetVersionEx(&v);
101 v.dwPlatformId == VER_PLATFORM_WIN32_NT;
102 }) ? "cmd.exe" : "command.com").
103 Instead it simply concatenates the arguments, separated by ' ', and calls
104 CreateProcess(). We must quote the arguments since Windows CreateProcess()
105 interprets characters like ' ', '\t', '\\', '"' (but not '<' and '>') in a
106 special way:
107 - Space and tab are interpreted as delimiters. They are not treated as
108 delimiters if they are surrounded by double quotes: "...".
109 - Unescaped double quotes are removed from the input. Their only effect is
110 that within double quotes, space and tab are treated like normal
111 characters.
112 - Backslashes not followed by double quotes are not special.
113 - But 2*n+1 backslashes followed by a double quote become
114 n backslashes followed by a double quote (n >= 0):
115 \" -> "
116 \\\" -> \"
117 \\\\\" -> \\"
118 - '*', '?' characters may get expanded through wildcard expansion in the
119 callee: By default, in the callee, the initialization code before main()
120 takes the result of GetCommandLine(), wildcard-expands it, and passes it
121 to main(). The exceptions to this rule are:
122 - programs that inspect GetCommandLine() and ignore argv,
123 - mingw programs that have a global variable 'int _CRT_glob = 0;',
124 - Cygwin programs, when invoked from a Cygwin program.
125 */
126 #define SHELL_SPECIAL_CHARS "\"\\ \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037*?"
127 #define SHELL_SPACE_CHARS " \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037"
128 static char **
prepare_spawn(char ** argv)129 prepare_spawn (char **argv)
130 {
131 size_t argc;
132 char **new_argv;
133 size_t i;
134
135 /* Count number of arguments. */
136 for (argc = 0; argv[argc] != NULL; argc++)
137 ;
138
139 /* Allocate new argument vector. */
140 new_argv = XNMALLOC (1 + argc + 1, char *);
141
142 /* Add an element upfront that can be used when argv[0] turns out to be a
143 script, not a program.
144 On Unix, this would be "/bin/sh". On native Windows, "sh" is actually
145 "sh.exe". We have to omit the directory part and rely on the search in
146 PATH, because the mingw "mount points" are not visible inside Windows
147 CreateProcess(). */
148 *new_argv++ = "sh.exe";
149
150 /* Put quoted arguments into the new argument vector. */
151 for (i = 0; i < argc; i++)
152 {
153 const char *string = argv[i];
154
155 if (string[0] == '\0')
156 new_argv[i] = xstrdup ("\"\"");
157 else if (strpbrk (string, SHELL_SPECIAL_CHARS) != NULL)
158 {
159 bool quote_around = (strpbrk (string, SHELL_SPACE_CHARS) != NULL);
160 size_t length;
161 unsigned int backslashes;
162 const char *s;
163 char *quoted_string;
164 char *p;
165
166 length = 0;
167 backslashes = 0;
168 if (quote_around)
169 length++;
170 for (s = string; *s != '\0'; s++)
171 {
172 char c = *s;
173 if (c == '"')
174 length += backslashes + 1;
175 length++;
176 if (c == '\\')
177 backslashes++;
178 else
179 backslashes = 0;
180 }
181 if (quote_around)
182 length += backslashes + 1;
183
184 quoted_string = (char *) xmalloc (length + 1);
185
186 p = quoted_string;
187 backslashes = 0;
188 if (quote_around)
189 *p++ = '"';
190 for (s = string; *s != '\0'; s++)
191 {
192 char c = *s;
193 if (c == '"')
194 {
195 unsigned int j;
196 for (j = backslashes + 1; j > 0; j--)
197 *p++ = '\\';
198 }
199 *p++ = c;
200 if (c == '\\')
201 backslashes++;
202 else
203 backslashes = 0;
204 }
205 if (quote_around)
206 {
207 unsigned int j;
208 for (j = backslashes; j > 0; j--)
209 *p++ = '\\';
210 *p++ = '"';
211 }
212 *p = '\0';
213
214 new_argv[i] = quoted_string;
215 }
216 else
217 new_argv[i] = (char *) string;
218 }
219 new_argv[argc] = NULL;
220
221 return new_argv;
222 }
223