plugins/sh/sh.c

   1 /* nbdkit
   2  * Copyright Red Hat
   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 <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdbool.h>
  38 #include <inttypes.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41 #include <errno.h>
  42 #include <sys/stat.h>
  43
  44 #define NBDKIT_API_VERSION 2
  45
  46 #include <nbdkit-plugin.h>
  47
  48 #include "cleanup.h"
  49
  50 #include "call.h"
  51 #include "methods.h"
  52
  53 static char *script;
  54 static char *magic_config_key;
  55
  56 /* This is called back by methods.c to get the current script name (if
  57  * set).  The method parameter is ignored by nbdkit-sh-plugin.
  58  */
  59 const char *
  60 get_script (const char *method)
  61 {
  62   return script;
  63 }
  64
  65 static void
  66 sh_load (void)
  67 {
  68   call_load ();
  69 }
  70
  71 static void
  72 sh_unload (void)
  73 {
  74   const char *method = "unload";
  75
  76   /* Run the unload method.  Ignore all errors. */
  77   if (script) {
  78     const char *args[] = { script, method, NULL };
  79
  80     call (args);
  81   }
  82
  83   call_unload ();
  84   free (script);
  85   free (magic_config_key);
  86 }
  87
  88 /* This implements the "inline script" feature.  Read stdin into a
  89  * temporary file and return the name of the file which the caller
  90  * must free.  For convenience we put the temporary file into tmpdir
  91  * but that's an implementation detail.
  92  */
  93 static char *
  94 inline_script (void)
  95 {
  96   const char scriptname[] = "inline-script.sh";
  97   char *filename = NULL;
  98   CLEANUP_FREE char *cmd = NULL;
  99
 100   if (!nbdkit_stdio_safe ()) {
 101     nbdkit_error ("inline script is incompatible with -s");
 102     return NULL;
 103   }
 104
 105   if (asprintf (&filename, "%s/%s", tmpdir, scriptname) == -1) {
 106     nbdkit_error ("asprintf: %m");
 107     goto err;
 108   }
 109
 110   /* Safe because both the tmpdir and script name are controlled by us
 111    * and don't contain characters that need quoting.
 112    */
 113   if (asprintf (&cmd, "cat > %s", filename) == -1) {
 114     nbdkit_error ("asprintf: %m");
 115     goto err;
 116   }
 117
 118   if (system (cmd) != 0) {
 119     nbdkit_error ("sh: failed to copy inline script to temporary file");
 120     goto err;
 121   }
 122
 123   if (chmod (filename, 0500) == -1) {
 124     nbdkit_error ("chmod: %s: %m", filename);
 125     goto err;
 126   }
 127
 128   return filename;
 129
 130  err:
 131   free (filename);
 132   return NULL;
 133 }
 134
 135 static int
 136 sh_config (const char *key, const char *value)
 137 {
 138   if (!script) {
 139     /* The first parameter MUST be "script". */
 140     if (strcmp (key, "script") != 0) {
 141       nbdkit_error ("the first parameter must be script=/path/to/script");
 142       return -1;
 143     }
 144
 145     /* If the script name is not "-" then it's expected to be a
 146      * filename, otherwise it's an inline script which must be read
 147      * into a temporary file.  Either way we want an absolute path.
 148      */
 149     if (strcmp (value, "-") != 0)
 150       script = nbdkit_realpath (value);
 151     else
 152       script = inline_script ();
 153     if (script == NULL)
 154       return -1;
 155
 156     /* Call the load method. */
 157     const char *args[] = { script, "load", NULL };
 158     switch (call (args)) {
 159     case OK:
 160     case MISSING:
 161       break;
 162
 163     case ERROR:
 164       return -1;
 165
 166     case RET_FALSE:
 167       nbdkit_error ("%s: %s method returned unexpected code (3/false)",
 168                     script, "load");
 169       errno = EIO;
 170       return -1;
 171
 172     default: abort ();
 173     }
 174
 175     /* Call the magic_config_key method if it exists. */
 176     const char *args2[] = { script, "magic_config_key", NULL };
 177     CLEANUP_FREE_STRING string s = empty_vector;
 178     switch (call_read (&s, args2)) {
 179     case OK:
 180       if (s.len > 0 && s.ptr[s.len-1] == '\n')
 181         s.ptr[s.len-1] = '\0';
 182       magic_config_key = strdup (s.ptr);
 183       if (magic_config_key == NULL) {
 184         nbdkit_error ("strdup: %m");
 185         return -1;
 186       }
 187       break;
 188
 189     case MISSING:
 190       break;
 191
 192     case ERROR:
 193       return -1;
 194
 195     case RET_FALSE:
 196       nbdkit_error ("%s: %s method returned unexpected code (3/false)",
 197                     script, "magic_config_key");
 198       errno = EIO;
 199       return -1;
 200
 201     default: abort ();
 202     }
 203   }
 204   else {
 205     /* If the script sets a magic_config_key then it's possible that
 206      * we will be called here with key == "script" (which is the
 207      * plugin.magic_config_key).  If that happens then swap in the
 208      * script magic_config_key as the key.  However if the script
 209      * didn't define a magic_config_key then it's an error, emulating
 210      * the behaviour of the core server.
 211      */
 212     if (strcmp (key, "script") == 0) {
 213       if (magic_config_key)
 214         key = magic_config_key;
 215       else {
 216         nbdkit_error ("%s: expecting key=value on the command line but got: "
 217                       "%s\n",
 218                       script, value);
 219         return -1;
 220       }
 221     }
 222
 223     const char *args[] = { script, "config", key, value, NULL };
 224     switch (call (args)) {
 225     case OK:
 226       return 0;
 227
 228     case MISSING:
 229       /* Emulate what core nbdkit does if a config callback is NULL. */
 230       nbdkit_error ("%s: this plugin does not need command line configuration",
 231                     script);
 232       return -1;
 233
 234     case ERROR:
 235       return -1;
 236
 237     case RET_FALSE:
 238       nbdkit_error ("%s: %s method returned unexpected code (3/false)",
 239                     script, "config");
 240       errno = EIO;
 241       return -1;
 242
 243     default: abort ();
 244     }
 245   }
 246
 247   return 0;
 248 }
 249
 250 static int
 251 sh_config_complete (void)
 252 {
 253   const char *args[] = { script, "config_complete", NULL };
 254
 255   if (!script) {
 256     nbdkit_error ("missing script parameter");
 257     return -1;
 258   }
 259
 260   switch (call (args)) {
 261   case OK:
 262   case MISSING:
 263     return 0;
 264
 265   case ERROR:
 266     return -1;
 267
 268   case RET_FALSE:
 269     nbdkit_error ("%s: %s method returned unexpected code (3/false)",
 270                   script, "config_complete");
 271     errno = EIO;
 272     return -1;
 273
 274   default: abort ();
 275   }
 276 }
 277
 278 #define sh_config_help \
 279   "script=<FILENAME>     (required) The shell script to run.\n" \
 280   "[other arguments may be used by the plugin that you load]"
 281
 282 /* See also the comments in call.c:call3() */
 283 #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
 284
 285 static struct nbdkit_plugin plugin = {
 286   .name               = "sh",
 287   .version            = PACKAGE_VERSION,
 288   .load               = sh_load,
 289   .unload             = sh_unload,
 290
 291   .dump_plugin        = sh_dump_plugin,
 292
 293   .config             = sh_config,
 294   .config_complete    = sh_config_complete,
 295   .config_help        = sh_config_help,
 296   .magic_config_key   = "script",
 297   .thread_model       = sh_thread_model,
 298   .get_ready          = sh_get_ready,
 299   .after_fork         = sh_after_fork,
 300
 301   .preconnect         = sh_preconnect,
 302   .list_exports       = sh_list_exports,
 303   .default_export     = sh_default_export,
 304   .open               = sh_open,
 305   .close              = sh_close,
 306
 307   .export_description = sh_export_description,
 308   .get_size           = sh_get_size,
 309   .block_size         = sh_block_size,
 310   .can_write          = sh_can_write,
 311   .can_flush          = sh_can_flush,
 312   .is_rotational      = sh_is_rotational,
 313   .can_trim           = sh_can_trim,
 314   .can_zero           = sh_can_zero,
 315   .can_extents        = sh_can_extents,
 316   .can_fua            = sh_can_fua,
 317   .can_multi_conn     = sh_can_multi_conn,
 318   .can_cache          = sh_can_cache,
 319   .can_fast_zero      = sh_can_fast_zero,
 320
 321   .pread              = sh_pread,
 322   .pwrite             = sh_pwrite,
 323   .flush              = sh_flush,
 324   .trim               = sh_trim,
 325   .zero               = sh_zero,
 326   .extents            = sh_extents,
 327   .cache              = sh_cache,
 328
 329   .errno_is_preserved = 1,
 330 };
 331
 332 NBDKIT_REGISTER_PLUGIN (plugin)