plugins/cdi/cdi.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 <string.h>
  38 #include <unistd.h>
  39 #include <fcntl.h>
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42
  43 #include <nbdkit-plugin.h>
  44
  45 #include "cleanup.h"
  46 #include "utils.h"
  47
  48 /* Parameters. */
  49 static const char *name;    /* Name or URI of container image. */
  50 static int layer = 0;       /* Layer (may be negative to count from end). */
  51
  52 /* The script that we run to pull and unpack the image. */
  53 static const char script[] =
  54   /* Exit on errors. */
  55   "set -e\n"
  56   /* Avoid stdin/stdout leaking (because of nbdkit -s).
  57    * XXX Capture errors to a temporary file.
  58    */
  59   "exec </dev/null >/dev/null\n"
  60   /* Create a temporary directory to extract the image to. */
  61   "d=\"$tmpfile.d\"\n"
  62   "podman pull \"$name\"\n"
  63   "podman save --format oci-dir -o \"$d\" \"$name\"\n"
  64   "f=\"$d/$( jq -r \".layers[$layer].digest\" < \"$d/manifest.json\" |\n"
  65   "          cut -d: -f2 )\"\n"
  66   "if ! test -f \"$f\"; then\n"
  67   "    echo \"cdi: could not extract layer\"\n"
  68   "    rm -rf \"$d\"\n"
  69   "    exit 1\n"
  70   "fi\n"
  71   "mv \"$f\" \"$tmpfile\"\n"
  72   "rm -rf \"$d\"\n";
  73
  74 /* The temporary file. */
  75 static int fd = -1;
  76
  77 /* Construct the temporary file. */
  78 static int
  79 make_layer (void)
  80 {
  81   const char *tmpdir;
  82   CLEANUP_FREE char *template = NULL;
  83   CLEANUP_FREE char *command = NULL;
  84   size_t command_len = 0;
  85   FILE *fp;
  86   int r;
  87
  88   /* Path for temporary file. */
  89   tmpdir = getenv ("TMPDIR");
  90   if (tmpdir == NULL)
  91     tmpdir = LARGE_TMPDIR;
  92   if (asprintf (&template, "%s/imageXXXXXX", tmpdir) == -1) {
  93     nbdkit_error ("asprintf: %m");
  94     return -1;
  95   }
  96
  97   fd = mkstemp (template);
  98   if (fd == -1) {
  99     nbdkit_error ("mkstemp: %s: %m", template);
 100     return -1;
 101   }
 102
 103   /* Construct the podman script. */
 104   fp = open_memstream (&command, &command_len);
 105   if (fp == NULL) {
 106     nbdkit_error ("open_memstream: %m");
 107     return -1;
 108   }
 109   fprintf (fp, "name="); shell_quote (name, fp); putc ('\n', fp);
 110   fprintf (fp, "layer=%d\n", layer);
 111   fprintf (fp, "tmpfile="); shell_quote (template, fp); putc ('\n', fp);
 112   fprintf (fp, "\n");
 113   fprintf (fp, "%s", script);
 114   if (fclose (fp) == EOF) {
 115     nbdkit_error ("memstream failed: %m");
 116     return -1;
 117   }
 118
 119   /* Run the command. */
 120   nbdkit_debug ("%s", command);
 121   r = system (command);
 122   if (exit_status_to_nbd_error (r, "podman") == -1)
 123     return -1;
 124
 125   /* Expect that the script creates 'template'. */
 126   if (access (template, F_OK) != 0) {
 127     nbdkit_error ("internal error: expected %s to be created", template);
 128     return -1;
 129   }
 130
 131   /* Since the script likely overwrites the file, we need to reopen it. */
 132   close (fd);
 133   fd = open (template, O_RDONLY|O_CLOEXEC);
 134   if (fd == -1) {
 135     nbdkit_error ("open: %s: %m", template);
 136     unlink (template);
 137     return -1;
 138   }
 139
 140   /* Since we've opened the file, we can unlink it. */
 141   unlink (template);
 142
 143   return 0;
 144 }
 145
 146 static void
 147 cdi_unload (void)
 148 {
 149   if (fd >= 0)
 150     close (fd);
 151 }
 152
 153 static int
 154 cdi_config (const char *key, const char *value)
 155 {
 156   if (strcmp (key, "name") == 0)
 157     name = value;
 158   else if (strcmp (key, "layer") == 0) {
 159     if (nbdkit_parse_int ("layer", value, &layer) == -1)
 160       return -1;
 161   }
 162   else {
 163     nbdkit_error ("unknown parameter '%s'", key);
 164     return -1;
 165   }
 166
 167   return 0;
 168 }
 169
 170 static int
 171 cdi_config_complete (void)
 172 {
 173   if (name == NULL) {
 174     nbdkit_error ("you must supply the 'name' parameter "
 175                   "after the plugin name on the command line");
 176     return -1;
 177   }
 178
 179   return 0;
 180 }
 181
 182 #define cdi_config_help \
 183   "name=NAME[:TAG|@DIGEST] (required) Name or URI of container image.\n" \
 184   "layer=<N>                          Layer of image to export."
 185
 186 static int
 187 cdi_get_ready (void)
 188 {
 189   return make_layer ();
 190 }
 191
 192 static void *
 193 cdi_open (int readonly)
 194 {
 195   return NBDKIT_HANDLE_NOT_NEEDED;
 196 }
 197
 198 #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
 199
 200 /* Get the file size. */
 201 static int64_t
 202 cdi_get_size (void *handle)
 203 {
 204   struct stat statbuf;
 205
 206   if (fstat (fd, &statbuf) == -1) {
 207     nbdkit_error ("fstat: %m");
 208     return -1;
 209   }
 210
 211   return statbuf.st_size;
 212 }
 213
 214 /* Serves the same data over multiple connections. */
 215 static int
 216 cdi_can_multi_conn (void *handle)
 217 {
 218   return 1;
 219 }
 220
 221 static int
 222 cdi_can_cache (void *handle)
 223 {
 224   /* Let nbdkit call pread to populate the file system cache. */
 225   return NBDKIT_CACHE_EMULATE;
 226 }
 227
 228 /* Read data from the file. */
 229 static int
 230 cdi_pread (void *handle, void *buf, uint32_t count, uint64_t offset)
 231 {
 232   while (count > 0) {
 233     ssize_t r = pread (fd, buf, count, offset);
 234     if (r == -1) {
 235       nbdkit_error ("pread: %m");
 236       return -1;
 237     }
 238     if (r == 0) {
 239       nbdkit_error ("pread: unexpected end of file");
 240       return -1;
 241     }
 242     buf += r;
 243     count -= r;
 244     offset += r;
 245   }
 246
 247   return 0;
 248 }
 249
 250 static struct nbdkit_plugin plugin = {
 251   .name              = "cdi",
 252   .longname          = "nbdkit containerized data importer plugin",
 253   .version           = PACKAGE_VERSION,
 254   .unload            = cdi_unload,
 255   .config            = cdi_config,
 256   .config_complete   = cdi_config_complete,
 257   .config_help       = cdi_config_help,
 258   .magic_config_key  = "name",
 259   .get_ready         = cdi_get_ready,
 260   .open              = cdi_open,
 261   .get_size          = cdi_get_size,
 262   .can_multi_conn    = cdi_can_multi_conn,
 263   .can_cache         = cdi_can_cache,
 264   .pread             = cdi_pread,
 265   .errno_is_preserved = 1,
 266 };
 267
 268 NBDKIT_REGISTER_PLUGIN (plugin)