lib/w32spawn.h

   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
  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
  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
  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
  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 **
 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 }