common/utils/utils.c

   1 /* nbdkit
   2  * Copyright (C) 2018-2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <fcntl.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <sys/socket.h>
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42 #include <unistd.h>
  43
  44 #include <nbdkit-plugin.h>
  45
  46 /* Print str to fp, shell quoting if necessary.  This comes from
  47  * libguestfs, but was written by me so I'm relicensing it to a BSD
  48  * license for nbdkit.
  49  */
  50 void
  51 shell_quote (const char *str, FILE *fp)
  52 {
  53   /* Note possible bug in this list (XXX):
  54    * https://www.redhat.com/archives/libguestfs/2019-February/msg00036.html
  55    */
  56   const char *safe_chars =
  57     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.-_=,:/";
  58   size_t i, len;
  59
  60   /* If the string consists only of safe characters, output it as-is. */
  61   len = strlen (str);
  62   if (len > 0 && len == strspn (str, safe_chars)) {
  63     fputs (str, fp);
  64     return;
  65   }
  66
  67   /* Double-quote the string. */
  68   fputc ('"', fp);
  69   for (i = 0; i < len; ++i) {
  70     switch (str[i]) {
  71     case '$': case '`': case '\\': case '"':
  72       fputc ('\\', fp);
  73       /*FALLTHROUGH*/
  74     default:
  75       fputc (str[i], fp);
  76     }
  77   }
  78   fputc ('"', fp);
  79 }
  80
  81 /* Print str to fp, URI quoting if necessary.
  82  * The resulting string is safe for use in a URI path or query component,
  83  * and can be passed through the shell without further quoting.
  84  */
  85 void
  86 uri_quote (const char *str, FILE *fp)
  87 {
  88   /* safe_chars contains the RFC 3986 unreserved characters plus '/'. */
  89   const char *safe_chars =
  90     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.-_~/";
  91   size_t i, len;
  92
  93   /* If the string consists only of safe characters, output it as-is. */
  94   len = strlen (str);
  95   if (len == strspn (str, safe_chars)) {
  96     fputs (str, fp);
  97     return;
  98   }
  99
 100   for (i = 0; i < len; ++i) {
 101     if (strchr (safe_chars, str[i]))
 102       fputc (str[i], fp);
 103     else
 104       fprintf (fp, "%%%02X", str[i] & 0xff);
 105   }
 106 }
 107
 108 /* Convert exit status to nbd_error.  If the exit status was nonzero
 109  * or another failure then -1 is returned.
 110  */
 111 int
 112 exit_status_to_nbd_error (int status, const char *cmd)
 113 {
 114   if (WIFEXITED (status) && WEXITSTATUS (status) != 0) {
 115     nbdkit_error ("%s: command failed with exit code %d",
 116                   cmd, WEXITSTATUS (status));
 117     return -1;
 118   }
 119   else if (WIFSIGNALED (status)) {
 120     nbdkit_error ("%s: command was killed by signal %d",
 121                   cmd, WTERMSIG (status));
 122     return -1;
 123   }
 124   else if (WIFSTOPPED (status)) {
 125     nbdkit_error ("%s: command was stopped by signal %d",
 126                   cmd, WSTOPSIG (status));
 127     return -1;
 128   }
 129
 130   return 0;
 131 }
 132
 133 /* Set the FD_CLOEXEC flag on the given fd, if it is non-negative.
 134  * On failure, close fd and return -1; on success, return fd.
 135  *
 136  * Note that this function should ONLY be used on platforms that lack
 137  * atomic CLOEXEC support during fd creation (such as Haiku in 2019);
 138  * when using it as a fallback path, you must also consider how to
 139  * prevent fd leaks to plugins that want to fork().
 140  */
 141 int
 142 set_cloexec (int fd) {
 143 #if defined SOCK_CLOEXEC && defined HAVE_MKOSTEMP
 144   nbdkit_error ("prefer creating fds with CLOEXEC atomically set");
 145   close (fd);
 146   errno = EBADF;
 147   return -1;
 148 #else
 149 # if defined SOCK_CLOEXEC || defined HAVE_MKOSTEMP
 150 # error "Unexpected: your system has incomplete atomic CLOEXEC support"
 151 # endif
 152   int f;
 153   int err;
 154
 155   if (fd == -1)
 156     return -1;
 157
 158   f = fcntl (fd, F_GETFD);
 159   if (f == -1 || fcntl (fd, F_SETFD, f | FD_CLOEXEC) == -1) {
 160     err = errno;
 161     nbdkit_error ("fcntl: %m");
 162     close (fd);
 163     errno = err;
 164     return -1;
 165   }
 166   return fd;
 167 #endif
 168 }
 169
 170 /* Set the O_NONBLOCK flag on the given fd, if it is non-negative.
 171  * On failure, close fd and return -1; on success, return fd.
 172  */
 173 int
 174 set_nonblock (int fd) {
 175   int f;
 176   int err;
 177
 178   if (fd == -1)
 179     return -1;
 180
 181   f = fcntl (fd, F_GETFL);
 182   if (f == -1 || fcntl (fd, F_SETFL, f | O_NONBLOCK) == -1) {
 183     err = errno;
 184     nbdkit_error ("fcntl: %m");
 185     close (fd);
 186     errno = err;
 187     return -1;
 188   }
 189   return fd;
 190 }