1 /* Auxiliary functions for the creation of subprocesses. Native Windows API.
2 Copyright (C) 2001, 2003-2020 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 <https://www.gnu.org/licenses/>. */
17
18 #ifndef __KLIBC__
19 /* Get declarations of the native Windows API functions. */
20 # define WIN32_LEAN_AND_MEAN
21 # include <windows.h>
22 #endif
23
24 /* Get _open_osfhandle(). */
25 #include <io.h>
26
27 #include <stdbool.h>
28 #include <string.h>
29 #include <unistd.h>
30 #include <errno.h>
31
32 /* Get _get_osfhandle(). */
33 # if GNULIB_MSVC_NOTHROW
34 # include "msvc-nothrow.h"
35 # else
36 # include <io.h>
37 # endif
38
39 #include "cloexec.h"
40 #include "xalloc.h"
41
42 /* Duplicates a file handle, making the copy uninheritable.
43 Returns -1 for a file handle that is equivalent to closed. */
44 static int
dup_noinherit(int fd)45 dup_noinherit (int fd)
46 {
47 fd = dup_cloexec (fd);
48 if (fd < 0 && errno == EMFILE)
49 error (EXIT_FAILURE, errno, _("_open_osfhandle failed"));
50
51 return fd;
52 }
53
54 /* Returns a file descriptor equivalent to FD, except that the resulting file
55 descriptor is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
56 FD must be open and non-inheritable. The result will be non-inheritable as
57 well.
58 If FD < 0, FD itself is returned. */
59 static int
fd_safer_noinherit(int fd)60 fd_safer_noinherit (int fd)
61 {
62 if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
63 {
64 /* The recursion depth is at most 3. */
65 int nfd = fd_safer_noinherit (dup_noinherit (fd));
66 int saved_errno = errno;
67 close (fd);
68 errno = saved_errno;
69 return nfd;
70 }
71 return fd;
72 }
73
74 /* Duplicates a file handle, making the copy uninheritable and ensuring the
75 result is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
76 Returns -1 for a file handle that is equivalent to closed. */
77 static int
dup_safer_noinherit(int fd)78 dup_safer_noinherit (int fd)
79 {
80 return fd_safer_noinherit (dup_noinherit (fd));
81 }
82
83 /* Undoes the effect of TEMPFD = dup_safer_noinherit (ORIGFD); */
84 static void
undup_safer_noinherit(int tempfd,int origfd)85 undup_safer_noinherit (int tempfd, int origfd)
86 {
87 if (tempfd >= 0)
88 {
89 if (dup2 (tempfd, origfd) < 0)
90 error (EXIT_FAILURE, errno, _("cannot restore fd %d: dup2 failed"),
91 origfd);
92 close (tempfd);
93 }
94 else
95 {
96 /* origfd was closed or open to no handle at all. Set it to a closed
97 state. This is (nearly) equivalent to the original state. */
98 close (origfd);
99 }
100 }
101
102 /* Prepares an argument vector before calling spawn().
103 Note that spawn() does not by itself call the command interpreter
104 (getenv ("COMSPEC") != NULL ? getenv ("COMSPEC") :
105 ({ OSVERSIONINFO v; v.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
106 GetVersionEx(&v);
107 v.dwPlatformId == VER_PLATFORM_WIN32_NT;
108 }) ? "cmd.exe" : "command.com").
109 Instead it simply concatenates the arguments, separated by ' ', and calls
110 CreateProcess(). We must quote the arguments since Windows CreateProcess()
111 interprets characters like ' ', '\t', '\\', '"' (but not '<' and '>') in a
112 special way:
113 - Space and tab are interpreted as delimiters. They are not treated as
114 delimiters if they are surrounded by double quotes: "...".
115 - Unescaped double quotes are removed from the input. Their only effect is
116 that within double quotes, space and tab are treated like normal
117 characters.
118 - Backslashes not followed by double quotes are not special.
119 - But 2*n+1 backslashes followed by a double quote become
120 n backslashes followed by a double quote (n >= 0):
121 \" -> "
122 \\\" -> \"
123 \\\\\" -> \\"
124 - '*', '?' characters may get expanded through wildcard expansion in the
125 callee: By default, in the callee, the initialization code before main()
126 takes the result of GetCommandLine(), wildcard-expands it, and passes it
127 to main(). The exceptions to this rule are:
128 - programs that inspect GetCommandLine() and ignore argv,
129 - mingw programs that have a global variable 'int _CRT_glob = 0;',
130 - Cygwin programs, when invoked from a Cygwin program.
131 */
132 #ifndef __KLIBC__
133 # 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*?"
134 # 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"
135 #else
136 # define SHELL_SPECIAL_CHARS ""
137 # define SHELL_SPACE_CHARS ""
138 #endif
139 static char **
prepare_spawn(char ** argv)140 prepare_spawn (char **argv)
141 {
142 size_t argc;
143 char **new_argv;
144 size_t i;
145
146 /* Count number of arguments. */
147 for (argc = 0; argv[argc] != NULL; argc++)
148 ;
149
150 /* Allocate new argument vector. */
151 new_argv = XNMALLOC (1 + argc + 1, char *);
152
153 /* Add an element upfront that can be used when argv[0] turns out to be a
154 script, not a program.
155 On Unix, this would be "/bin/sh". On native Windows, "sh" is actually
156 "sh.exe". We have to omit the directory part and rely on the search in
157 PATH, because the mingw "mount points" are not visible inside Windows
158 CreateProcess(). */
159 *new_argv++ = "sh.exe";
160
161 /* Put quoted arguments into the new argument vector. */
162 for (i = 0; i < argc; i++)
163 {
164 const char *string = argv[i];
165
166 if (string[0] == '\0')
167 new_argv[i] = xstrdup ("\"\"");
168 else if (strpbrk (string, SHELL_SPECIAL_CHARS) != NULL)
169 {
170 bool quote_around = (strpbrk (string, SHELL_SPACE_CHARS) != NULL);
171 size_t length;
172 unsigned int backslashes;
173 const char *s;
174 char *quoted_string;
175 char *p;
176
177 length = 0;
178 backslashes = 0;
179 if (quote_around)
180 length++;
181 for (s = string; *s != '\0'; s++)
182 {
183 char c = *s;
184 if (c == '"')
185 length += backslashes + 1;
186 length++;
187 if (c == '\\')
188 backslashes++;
189 else
190 backslashes = 0;
191 }
192 if (quote_around)
193 length += backslashes + 1;
194
195 quoted_string = (char *) xmalloc (length + 1);
196
197 p = quoted_string;
198 backslashes = 0;
199 if (quote_around)
200 *p++ = '"';
201 for (s = string; *s != '\0'; s++)
202 {
203 char c = *s;
204 if (c == '"')
205 {
206 unsigned int j;
207 for (j = backslashes + 1; j > 0; j--)
208 *p++ = '\\';
209 }
210 *p++ = c;
211 if (c == '\\')
212 backslashes++;
213 else
214 backslashes = 0;
215 }
216 if (quote_around)
217 {
218 unsigned int j;
219 for (j = backslashes; j > 0; j--)
220 *p++ = '\\';
221 *p++ = '"';
222 }
223 *p = '\0';
224
225 new_argv[i] = quoted_string;
226 }
227 else
228 new_argv[i] = (char *) string;
229 }
230 new_argv[argc] = NULL;
231
232 return new_argv;
233 }
234