src/libsystemd-network/dhcp-option.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 /***
   3   Copyright © 2013 Intel Corporation. All rights reserved.
   4 ***/
   5
   6 #include <errno.h>
   7 #include <stdint.h>
   8 #include <stdio.h>
   9
  10 #include "alloc-util.h"
  11 #include "dhcp-internal.h"
  12 #include "dhcp-server-internal.h"
  13 #include "memory-util.h"
  14 #include "strv.h"
  15 #include "utf8.h"
  16
  17 /* Append type-length value structure to the options buffer */
  18 static int dhcp_option_append_tlv(uint8_t options[], size_t size, size_t *offset, uint8_t code, size_t optlen, const void *optval) {
  19         assert(options);
  20         assert(size > 0);
  21         assert(offset);
  22         assert(optlen <= UINT8_MAX);
  23         assert(*offset < size);
  24
  25         if (*offset + 2 + optlen > size)
  26                 return -ENOBUFS;
  27
  28         options[*offset] = code;
  29         options[*offset + 1] = optlen;
  30
  31         memcpy_safe(&options[*offset + 2], optval, optlen);
  32         *offset += 2 + optlen;
  33         return 0;
  34 }
  35
  36 static int option_append(uint8_t options[], size_t size, size_t *offset,
  37                          uint8_t code, size_t optlen, const void *optval) {
  38         assert(options);
  39         assert(size > 0);
  40         assert(offset);
  41
  42         int r;
  43
  44         if (code != SD_DHCP_OPTION_END)
  45                 /* always make sure there is space for an END option */
  46                 size--;
  47
  48         switch (code) {
  49
  50         case SD_DHCP_OPTION_PAD:
  51         case SD_DHCP_OPTION_END:
  52                 if (*offset + 1 > size)
  53                         return -ENOBUFS;
  54
  55                 options[*offset] = code;
  56                 *offset += 1;
  57                 break;
  58
  59         case SD_DHCP_OPTION_USER_CLASS: {
  60                 size_t total = 0;
  61                 char **s;
  62
  63                 if (strv_isempty((char **) optval))
  64                         return -EINVAL;
  65
  66                 STRV_FOREACH(s, (char **) optval) {
  67                         size_t len = strlen(*s);
  68
  69                         if (len > 255 || len == 0)
  70                                 return -EINVAL;
  71
  72                         total += 1 + len;
  73                 }
  74
  75                 if (*offset + 2 + total > size)
  76                         return -ENOBUFS;
  77
  78                 options[*offset] = code;
  79                 options[*offset + 1] = total;
  80                 *offset += 2;
  81
  82                 STRV_FOREACH(s, (char **) optval) {
  83                         size_t len = strlen(*s);
  84
  85                         options[*offset] = len;
  86                         memcpy(&options[*offset + 1], *s, len);
  87                         *offset += 1 + len;
  88                 }
  89
  90                 break;
  91         }
  92         case SD_DHCP_OPTION_SIP_SERVER:
  93                 if (*offset + 3 + optlen > size)
  94                         return -ENOBUFS;
  95
  96                 options[*offset] = code;
  97                 options[*offset + 1] = optlen + 1;
  98                 options[*offset + 2] = 1;
  99
 100                 memcpy_safe(&options[*offset + 3], optval, optlen);
 101                 *offset += 3 + optlen;
 102
 103                 break;
 104         case SD_DHCP_OPTION_VENDOR_SPECIFIC: {
 105                 OrderedSet *s = (OrderedSet *) optval;
 106                 struct sd_dhcp_option *p;
 107                 size_t l = 0;
 108
 109                 ORDERED_SET_FOREACH(p, s)
 110                         l += p->length + 2;
 111
 112                 if (*offset + l + 2 > size)
 113                         return -ENOBUFS;
 114
 115                 options[*offset] = code;
 116                 options[*offset + 1] = l;
 117                 *offset += 2;
 118
 119                 ORDERED_SET_FOREACH(p, s) {
 120                         r = dhcp_option_append_tlv(options, size, offset, p->option, p->length, p->data);
 121                         if (r < 0)
 122                                 return r;
 123                 }
 124                 break;
 125         }
 126         case SD_DHCP_OPTION_RELAY_AGENT_INFORMATION: {
 127                 sd_dhcp_server *server = (sd_dhcp_server *) optval;
 128                 size_t current_offset = *offset + 2;
 129
 130                 if (server->agent_circuit_id) {
 131                         r = dhcp_option_append_tlv(options, size, &current_offset, SD_DHCP_RELAY_AGENT_CIRCUIT_ID,
 132                                                    strlen(server->agent_circuit_id), server->agent_circuit_id);
 133                         if (r < 0)
 134                                 return r;
 135                 }
 136                 if (server->agent_remote_id) {
 137                         r = dhcp_option_append_tlv(options, size, &current_offset, SD_DHCP_RELAY_AGENT_REMOTE_ID,
 138                                                    strlen(server->agent_remote_id), server->agent_remote_id);
 139                         if (r < 0)
 140                                 return r;
 141                 }
 142
 143                 options[*offset] = code;
 144                 options[*offset + 1] = current_offset - *offset - 2;
 145                 assert(current_offset - *offset - 2 <= UINT8_MAX);
 146                 *offset = current_offset;
 147                 break;
 148         }
 149         default:
 150                 return dhcp_option_append_tlv(options, size, offset, code, optlen, optval);
 151         }
 152         return 0;
 153 }
 154
 155 static int option_length(uint8_t *options, size_t length, size_t offset) {
 156         assert(options);
 157         assert(offset < length);
 158
 159         if (IN_SET(options[offset], SD_DHCP_OPTION_PAD, SD_DHCP_OPTION_END))
 160                 return 1;
 161         if (length < offset + 2)
 162                 return -ENOBUFS;
 163
 164         /* validating that buffer is long enough */
 165         if (length < offset + 2 + options[offset + 1])
 166                 return -ENOBUFS;
 167
 168         return options[offset + 1] + 2;
 169 }
 170
 171 int dhcp_option_find_option(uint8_t *options, size_t length, uint8_t code, size_t *ret_offset) {
 172         int r;
 173
 174         assert(options);
 175         assert(ret_offset);
 176
 177         for (size_t offset = 0; offset < length; offset += r) {
 178                 r = option_length(options, length, offset);
 179                 if (r < 0)
 180                         return r;
 181
 182                 if (code == options[offset]) {
 183                         *ret_offset = offset;
 184                         return r;
 185                 }
 186         }
 187         return -ENOENT;
 188 }
 189
 190 int dhcp_option_remove_option(uint8_t *options, size_t length, uint8_t option_code) {
 191         int r;
 192         size_t offset;
 193
 194         assert(options);
 195
 196         r = dhcp_option_find_option(options, length, option_code, &offset);
 197         if (r < 0)
 198                 return r;
 199
 200         memmove(options + offset, options + offset + r, length - offset - r);
 201         return length - r;
 202 }
 203
 204 int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
 205                        uint8_t overload,
 206                        uint8_t code, size_t optlen, const void *optval) {
 207         const bool use_file = overload & DHCP_OVERLOAD_FILE;
 208         const bool use_sname = overload & DHCP_OVERLOAD_SNAME;
 209         int r;
 210
 211         assert(message);
 212         assert(offset);
 213
 214         /* If *offset is in range [0, size), we are writing to ->options,
 215          * if *offset is in range [size, size + sizeof(message->file)) and use_file, we are writing to ->file,
 216          * if *offset is in range [size + use_file*sizeof(message->file), size + use_file*sizeof(message->file) + sizeof(message->sname))
 217          * and use_sname, we are writing to ->sname.
 218          */
 219
 220         if (*offset < size) {
 221                 /* still space in the options array */
 222                 r = option_append(message->options, size, offset, code, optlen, optval);
 223                 if (r >= 0)
 224                         return 0;
 225                 else if (r == -ENOBUFS && (use_file || use_sname)) {
 226                         /* did not fit, but we have more buffers to try
 227                            close the options array and move the offset to its end */
 228                         r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 229                         if (r < 0)
 230                                 return r;
 231
 232                         *offset = size;
 233                 } else
 234                         return r;
 235         }
 236
 237         if (use_file) {
 238                 size_t file_offset = *offset - size;
 239
 240                 if (file_offset < sizeof(message->file)) {
 241                         /* still space in the 'file' array */
 242                         r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
 243                         if (r >= 0) {
 244                                 *offset = size + file_offset;
 245                                 return 0;
 246                         } else if (r == -ENOBUFS && use_sname) {
 247                                 /* did not fit, but we have more buffers to try
 248                                    close the file array and move the offset to its end */
 249                                 r = option_append(message->file, sizeof(message->file), &file_offset, SD_DHCP_OPTION_END, 0, NULL);
 250                                 if (r < 0)
 251                                         return r;
 252
 253                                 *offset = size + sizeof(message->file);
 254                         } else
 255                                 return r;
 256                 }
 257         }
 258
 259         if (use_sname) {
 260                 size_t sname_offset = *offset - size - use_file*sizeof(message->file);
 261
 262                 if (sname_offset < sizeof(message->sname)) {
 263                         /* still space in the 'sname' array */
 264                         r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
 265                         if (r >= 0) {
 266                                 *offset = size + use_file*sizeof(message->file) + sname_offset;
 267                                 return 0;
 268                         } else
 269                                 /* no space, or other error, give up */
 270                                 return r;
 271                 }
 272         }
 273
 274         return -ENOBUFS;
 275 }
 276
 277 static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
 278                          uint8_t *message_type, char **error_message, dhcp_option_callback_t cb,
 279                          void *userdata) {
 280         uint8_t code, len;
 281         const uint8_t *option;
 282         size_t offset = 0;
 283
 284         while (offset < buflen) {
 285                 code = options[offset ++];
 286
 287                 switch (code) {
 288                 case SD_DHCP_OPTION_PAD:
 289                         continue;
 290
 291                 case SD_DHCP_OPTION_END:
 292                         return 0;
 293                 }
 294
 295                 if (buflen < offset + 1)
 296                         return -ENOBUFS;
 297
 298                 len = options[offset ++];
 299
 300                 if (buflen < offset + len)
 301                         return -EINVAL;
 302
 303                 option = &options[offset];
 304
 305                 switch (code) {
 306                 case SD_DHCP_OPTION_MESSAGE_TYPE:
 307                         if (len != 1)
 308                                 return -EINVAL;
 309
 310                         if (message_type)
 311                                 *message_type = *option;
 312
 313                         break;
 314
 315                 case SD_DHCP_OPTION_ERROR_MESSAGE:
 316                         if (len == 0)
 317                                 return -EINVAL;
 318
 319                         if (error_message) {
 320                                 _cleanup_free_ char *string = NULL;
 321
 322                                 /* Accept a trailing NUL byte */
 323                                 if (memchr(option, 0, len - 1))
 324                                         return -EINVAL;
 325
 326                                 string = memdup_suffix0((const char *) option, len);
 327                                 if (!string)
 328                                         return -ENOMEM;
 329
 330                                 if (!ascii_is_valid(string))
 331                                         return -EINVAL;
 332
 333                                 free_and_replace(*error_message, string);
 334                         }
 335
 336                         break;
 337                 case SD_DHCP_OPTION_OVERLOAD:
 338                         if (len != 1)
 339                                 return -EINVAL;
 340
 341                         if (overload)
 342                                 *overload = *option;
 343
 344                         break;
 345
 346                 default:
 347                         if (cb)
 348                                 cb(code, len, option, userdata);
 349
 350                         break;
 351                 }
 352
 353                 offset += len;
 354         }
 355
 356         if (offset < buflen)
 357                 return -EINVAL;
 358
 359         return 0;
 360 }
 361
 362 int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t cb, void *userdata, char **_error_message) {
 363         _cleanup_free_ char *error_message = NULL;
 364         uint8_t overload = 0;
 365         uint8_t message_type = 0;
 366         int r;
 367
 368         if (!message)
 369                 return -EINVAL;
 370
 371         if (len < sizeof(DHCPMessage))
 372                 return -EINVAL;
 373
 374         len -= sizeof(DHCPMessage);
 375
 376         r = parse_options(message->options, len, &overload, &message_type, &error_message, cb, userdata);
 377         if (r < 0)
 378                 return r;
 379
 380         if (overload & DHCP_OVERLOAD_FILE) {
 381                 r = parse_options(message->file, sizeof(message->file), NULL, &message_type, &error_message, cb, userdata);
 382                 if (r < 0)
 383                         return r;
 384         }
 385
 386         if (overload & DHCP_OVERLOAD_SNAME) {
 387                 r = parse_options(message->sname, sizeof(message->sname), NULL, &message_type, &error_message, cb, userdata);
 388                 if (r < 0)
 389                         return r;
 390         }
 391
 392         if (message_type == 0)
 393                 return -ENOMSG;
 394
 395         if (_error_message && IN_SET(message_type, DHCP_NAK, DHCP_DECLINE))
 396                 *_error_message = TAKE_PTR(error_message);
 397
 398         return message_type;
 399 }
 400
 401 static sd_dhcp_option* dhcp_option_free(sd_dhcp_option *i) {
 402         if (!i)
 403                 return NULL;
 404
 405         free(i->data);
 406         return mfree(i);
 407 }
 408
 409 int sd_dhcp_option_new(uint8_t option, const void *data, size_t length, sd_dhcp_option **ret) {
 410         assert_return(ret, -EINVAL);
 411         assert_return(length == 0 || data, -EINVAL);
 412
 413         _cleanup_free_ void *q = memdup(data, length);
 414         if (!q)
 415                 return -ENOMEM;
 416
 417         sd_dhcp_option *p = new(sd_dhcp_option, 1);
 418         if (!p)
 419                 return -ENOMEM;
 420
 421         *p = (sd_dhcp_option) {
 422                 .n_ref = 1,
 423                 .option = option,
 424                 .length = length,
 425                 .data = TAKE_PTR(q),
 426         };
 427
 428         *ret = TAKE_PTR(p);
 429         return 0;
 430 }
 431
 432 DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_option, sd_dhcp_option, dhcp_option_free);
 433 DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
 434                 dhcp_option_hash_ops,
 435                 void,
 436                 trivial_hash_func,
 437                 trivial_compare_func,
 438                 sd_dhcp_option,
 439                 sd_dhcp_option_unref);