src/libsystemd-network/dhcp-option.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   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 static int option_append(uint8_t options[], size_t size, size_t *offset,
  18                          uint8_t code, size_t optlen, const void *optval) {
  19         assert(options);
  20         assert(offset);
  21
  22         if (code != SD_DHCP_OPTION_END)
  23                 /* always make sure there is space for an END option */
  24                 size--;
  25
  26         switch (code) {
  27
  28         case SD_DHCP_OPTION_PAD:
  29         case SD_DHCP_OPTION_END:
  30                 if (*offset + 1 > size)
  31                         return -ENOBUFS;
  32
  33                 options[*offset] = code;
  34                 *offset += 1;
  35                 break;
  36
  37         case SD_DHCP_OPTION_USER_CLASS: {
  38                 size_t total = 0;
  39                 char **s;
  40
  41                 STRV_FOREACH(s, (char **) optval) {
  42                         size_t len = strlen(*s);
  43
  44                         if (len > 255)
  45                                 return -ENAMETOOLONG;
  46
  47                         total += 1 + len;
  48                 }
  49
  50                 if (*offset + 2 + total > size)
  51                         return -ENOBUFS;
  52
  53                 options[*offset] = code;
  54                 options[*offset + 1] =  total;
  55                 *offset += 2;
  56
  57                 STRV_FOREACH(s, (char **) optval) {
  58                         size_t len = strlen(*s);
  59
  60                         options[*offset] = len;
  61
  62                         memcpy(&options[*offset + 1], *s, len);
  63                         *offset += 1 + len;
  64                 }
  65
  66                 break;
  67         }
  68         case SD_DHCP_OPTION_SIP_SERVER:
  69                 if (*offset + 3 + optlen > size)
  70                         return -ENOBUFS;
  71
  72                 options[*offset] = code;
  73                 options[*offset + 1] = optlen + 1;
  74                 options[*offset + 2] = 1;
  75
  76                 memcpy_safe(&options[*offset + 3], optval, optlen);
  77                 *offset += 3 + optlen;
  78
  79                 break;
  80         case SD_DHCP_OPTION_VENDOR_SPECIFIC: {
  81                 OrderedHashmap *s = (OrderedHashmap *) optval;
  82                 struct sd_dhcp_raw_option *p;
  83                 size_t l = 0;
  84                 Iterator i;
  85
  86                 ORDERED_HASHMAP_FOREACH(p, s, i)
  87                         l += p->length + 2;
  88
  89                 if (*offset + l + 2 > size)
  90                         return -ENOBUFS;
  91
  92                 options[*offset] = code;
  93                 options[*offset + 1] = l;
  94
  95                 *offset += 2;
  96
  97                 ORDERED_HASHMAP_FOREACH(p, s, i) {
  98                         options[*offset] = p->type;
  99                         options[*offset + 1] = p->length;
 100                         memcpy(&options[*offset + 2], p->data, p->length);
 101                         *offset += 2 + p->length;
 102                 }
 103
 104                 break;
 105         }
 106         default:
 107                 if (*offset + 2 + optlen > size)
 108                         return -ENOBUFS;
 109
 110                 options[*offset] = code;
 111                 options[*offset + 1] = optlen;
 112
 113                 memcpy_safe(&options[*offset + 2], optval, optlen);
 114                 *offset += 2 + optlen;
 115
 116                 break;
 117         }
 118
 119         return 0;
 120 }
 121
 122 int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
 123                        uint8_t overload,
 124                        uint8_t code, size_t optlen, const void *optval) {
 125         const bool use_file = overload & DHCP_OVERLOAD_FILE;
 126         const bool use_sname = overload & DHCP_OVERLOAD_SNAME;
 127         int r;
 128
 129         assert(message);
 130         assert(offset);
 131
 132         /* If *offset is in range [0, size), we are writing to ->options,
 133          * if *offset is in range [size, size + sizeof(message->file)) and use_file, we are writing to ->file,
 134          * if *offset is in range [size + use_file*sizeof(message->file), size + use_file*sizeof(message->file) + sizeof(message->sname))
 135          * and use_sname, we are writing to ->sname.
 136          */
 137
 138         if (*offset < size) {
 139                 /* still space in the options array */
 140                 r = option_append(message->options, size, offset, code, optlen, optval);
 141                 if (r >= 0)
 142                         return 0;
 143                 else if (r == -ENOBUFS && (use_file || use_sname)) {
 144                         /* did not fit, but we have more buffers to try
 145                            close the options array and move the offset to its end */
 146                         r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 147                         if (r < 0)
 148                                 return r;
 149
 150                         *offset = size;
 151                 } else
 152                         return r;
 153         }
 154
 155         if (use_file) {
 156                 size_t file_offset = *offset - size;
 157
 158                 if (file_offset < sizeof(message->file)) {
 159                         /* still space in the 'file' array */
 160                         r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
 161                         if (r >= 0) {
 162                                 *offset = size + file_offset;
 163                                 return 0;
 164                         } else if (r == -ENOBUFS && use_sname) {
 165                                 /* did not fit, but we have more buffers to try
 166                                    close the file array and move the offset to its end */
 167                                 r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 168                                 if (r < 0)
 169                                         return r;
 170
 171                                 *offset = size + sizeof(message->file);
 172                         } else
 173                                 return r;
 174                 }
 175         }
 176
 177         if (use_sname) {
 178                 size_t sname_offset = *offset - size - use_file*sizeof(message->file);
 179
 180                 if (sname_offset < sizeof(message->sname)) {
 181                         /* still space in the 'sname' array */
 182                         r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
 183                         if (r >= 0) {
 184                                 *offset = size + use_file*sizeof(message->file) + sname_offset;
 185                                 return 0;
 186                         } else
 187                                 /* no space, or other error, give up */
 188                                 return r;
 189                 }
 190         }
 191
 192         return -ENOBUFS;
 193 }
 194
 195 static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
 196                          uint8_t *message_type, char **error_message, dhcp_option_callback_t cb,
 197                          void *userdata) {
 198         uint8_t code, len;
 199         const uint8_t *option;
 200         size_t offset = 0;
 201
 202         while (offset < buflen) {
 203                 code = options[offset ++];
 204
 205                 switch (code) {
 206                 case SD_DHCP_OPTION_PAD:
 207                         continue;
 208
 209                 case SD_DHCP_OPTION_END:
 210                         return 0;
 211                 }
 212
 213                 if (buflen < offset + 1)
 214                         return -ENOBUFS;
 215
 216                 len = options[offset ++];
 217
 218                 if (buflen < offset + len)
 219                         return -EINVAL;
 220
 221                 option = &options[offset];
 222
 223                 switch (code) {
 224                 case SD_DHCP_OPTION_MESSAGE_TYPE:
 225                         if (len != 1)
 226                                 return -EINVAL;
 227
 228                         if (message_type)
 229                                 *message_type = *option;
 230
 231                         break;
 232
 233                 case SD_DHCP_OPTION_ERROR_MESSAGE:
 234                         if (len == 0)
 235                                 return -EINVAL;
 236
 237                         if (error_message) {
 238                                 _cleanup_free_ char *string = NULL;
 239
 240                                 /* Accept a trailing NUL byte */
 241                                 if (memchr(option, 0, len - 1))
 242                                         return -EINVAL;
 243
 244                                 string = memdup_suffix0((const char *) option, len);
 245                                 if (!string)
 246                                         return -ENOMEM;
 247
 248                                 if (!ascii_is_valid(string))
 249                                         return -EINVAL;
 250
 251                                 free_and_replace(*error_message, string);
 252                         }
 253
 254                         break;
 255                 case SD_DHCP_OPTION_OVERLOAD:
 256                         if (len != 1)
 257                                 return -EINVAL;
 258
 259                         if (overload)
 260                                 *overload = *option;
 261
 262                         break;
 263
 264                 default:
 265                         if (cb)
 266                                 cb(code, len, option, userdata);
 267
 268                         break;
 269                 }
 270
 271                 offset += len;
 272         }
 273
 274         if (offset < buflen)
 275                 return -EINVAL;
 276
 277         return 0;
 278 }
 279
 280 int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t cb, void *userdata, char **_error_message) {
 281         _cleanup_free_ char *error_message = NULL;
 282         uint8_t overload = 0;
 283         uint8_t message_type = 0;
 284         int r;
 285
 286         if (!message)
 287                 return -EINVAL;
 288
 289         if (len < sizeof(DHCPMessage))
 290                 return -EINVAL;
 291
 292         len -= sizeof(DHCPMessage);
 293
 294         r = parse_options(message->options, len, &overload, &message_type, &error_message, cb, userdata);
 295         if (r < 0)
 296                 return r;
 297
 298         if (overload & DHCP_OVERLOAD_FILE) {
 299                 r = parse_options(message->file, sizeof(message->file), NULL, &message_type, &error_message, cb, userdata);
 300                 if (r < 0)
 301                         return r;
 302         }
 303
 304         if (overload & DHCP_OVERLOAD_SNAME) {
 305                 r = parse_options(message->sname, sizeof(message->sname), NULL, &message_type, &error_message, cb, userdata);
 306                 if (r < 0)
 307                         return r;
 308         }
 309
 310         if (message_type == 0)
 311                 return -ENOMSG;
 312
 313         if (_error_message && IN_SET(message_type, DHCP_NAK, DHCP_DECLINE))
 314                 *_error_message = TAKE_PTR(error_message);
 315
 316         return message_type;
 317 }