src/libsystemd-network/dhcp-option.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2013 Intel Corporation. All rights reserved.
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <stdint.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24
  25 #include "alloc-util.h"
  26 #include "utf8.h"
  27
  28 #include "dhcp-internal.h"
  29
  30 static int option_append(uint8_t options[], size_t size, size_t *offset,
  31                          uint8_t code, size_t optlen, const void *optval) {
  32         assert(options);
  33         assert(offset);
  34
  35         if (code != SD_DHCP_OPTION_END)
  36                 /* always make sure there is space for an END option */
  37                 size --;
  38
  39         switch (code) {
  40
  41         case SD_DHCP_OPTION_PAD:
  42         case SD_DHCP_OPTION_END:
  43                 if (size < *offset + 1)
  44                         return -ENOBUFS;
  45
  46                 options[*offset] = code;
  47                 *offset += 1;
  48                 break;
  49
  50         default:
  51                 if (size < *offset + optlen + 2)
  52                         return -ENOBUFS;
  53
  54                 options[*offset] = code;
  55                 options[*offset + 1] = optlen;
  56
  57                 memcpy_safe(&options[*offset + 2], optval, optlen);
  58                 *offset += optlen + 2;
  59
  60                 break;
  61         }
  62
  63         return 0;
  64 }
  65
  66 int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
  67                        uint8_t overload,
  68                        uint8_t code, size_t optlen, const void *optval) {
  69         size_t file_offset = 0, sname_offset =0;
  70         bool file, sname;
  71         int r;
  72
  73         assert(message);
  74         assert(offset);
  75
  76         file = overload & DHCP_OVERLOAD_FILE;
  77         sname = overload & DHCP_OVERLOAD_SNAME;
  78
  79         if (*offset < size) {
  80                 /* still space in the options array */
  81                 r = option_append(message->options, size, offset, code, optlen, optval);
  82                 if (r >= 0)
  83                         return 0;
  84                 else if (r == -ENOBUFS && (file || sname)) {
  85                         /* did not fit, but we have more buffers to try
  86                            close the options array and move the offset to its end */
  87                         r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
  88                         if (r < 0)
  89                                 return r;
  90
  91                         *offset = size;
  92                 } else
  93                         return r;
  94         }
  95
  96         if (overload & DHCP_OVERLOAD_FILE) {
  97                 file_offset = *offset - size;
  98
  99                 if (file_offset < sizeof(message->file)) {
 100                         /* still space in the 'file' array */
 101                         r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
 102                         if (r >= 0) {
 103                                 *offset = size + file_offset;
 104                                 return 0;
 105                         } else if (r == -ENOBUFS && sname) {
 106                                 /* did not fit, but we have more buffers to try
 107                                    close the file array and move the offset to its end */
 108                                 r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 109                                 if (r < 0)
 110                                         return r;
 111
 112                                 *offset = size + sizeof(message->file);
 113                         } else
 114                                 return r;
 115                 }
 116         }
 117
 118         if (overload & DHCP_OVERLOAD_SNAME) {
 119                 sname_offset = *offset - size - (file ? sizeof(message->file) : 0);
 120
 121                 if (sname_offset < sizeof(message->sname)) {
 122                         /* still space in the 'sname' array */
 123                         r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
 124                         if (r >= 0) {
 125                                 *offset = size + (file ? sizeof(message->file) : 0) + sname_offset;
 126                                 return 0;
 127                         } else {
 128                                 /* no space, or other error, give up */
 129                                 return r;
 130                         }
 131                 }
 132         }
 133
 134         return -ENOBUFS;
 135 }
 136
 137 static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
 138                          uint8_t *message_type, char **error_message, dhcp_option_cb_t cb,
 139                          void *userdata) {
 140         uint8_t code, len;
 141         const uint8_t *option;
 142         size_t offset = 0;
 143
 144         while (offset < buflen) {
 145                 code = options[offset ++];
 146
 147                 switch (code) {
 148                 case SD_DHCP_OPTION_PAD:
 149                         continue;
 150
 151                 case SD_DHCP_OPTION_END:
 152                         return 0;
 153                 }
 154
 155                 if (buflen < offset + 1)
 156                         return -ENOBUFS;
 157
 158                 len = options[offset ++];
 159
 160                 if (buflen < offset + len)
 161                         return -EINVAL;
 162
 163                 option = &options[offset];
 164
 165                 switch (code) {
 166                 case SD_DHCP_OPTION_MESSAGE_TYPE:
 167                         if (len != 1)
 168                                 return -EINVAL;
 169
 170                         if (message_type)
 171                                 *message_type = *option;
 172
 173                         break;
 174
 175                 case SD_DHCP_OPTION_ERROR_MESSAGE:
 176                         if (len == 0)
 177                                 return -EINVAL;
 178
 179                         if (error_message) {
 180                                 _cleanup_free_ char *string = NULL;
 181
 182                                 /* Accept a trailing NUL byte */
 183                                 if (memchr(option, 0, len - 1))
 184                                         return -EINVAL;
 185
 186                                 string = strndup((const char *) option, len);
 187                                 if (!string)
 188                                         return -ENOMEM;
 189
 190                                 if (!ascii_is_valid(string))
 191                                         return -EINVAL;
 192
 193                                 free(*error_message);
 194                                 *error_message = string;
 195                                 string = NULL;
 196                         }
 197
 198                         break;
 199                 case SD_DHCP_OPTION_OVERLOAD:
 200                         if (len != 1)
 201                                 return -EINVAL;
 202
 203                         if (overload)
 204                                 *overload = *option;
 205
 206                         break;
 207
 208                 default:
 209                         if (cb)
 210                                 cb(code, len, option, userdata);
 211
 212                         break;
 213                 }
 214
 215                 offset += len;
 216         }
 217
 218         if (offset < buflen)
 219                 return -EINVAL;
 220
 221         return 0;
 222 }
 223
 224 int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_cb_t cb, void *userdata, char **_error_message) {
 225         _cleanup_free_ char *error_message = NULL;
 226         uint8_t overload = 0;
 227         uint8_t message_type = 0;
 228         int r;
 229
 230         if (!message)
 231                 return -EINVAL;
 232
 233         if (len < sizeof(DHCPMessage))
 234                 return -EINVAL;
 235
 236         len -= sizeof(DHCPMessage);
 237
 238         r = parse_options(message->options, len, &overload, &message_type, &error_message, cb, userdata);
 239         if (r < 0)
 240                 return r;
 241
 242         if (overload & DHCP_OVERLOAD_FILE) {
 243                 r = parse_options(message->file, sizeof(message->file), NULL, &message_type, &error_message, cb, userdata);
 244                 if (r < 0)
 245                         return r;
 246         }
 247
 248         if (overload & DHCP_OVERLOAD_SNAME) {
 249                 r = parse_options(message->sname, sizeof(message->sname), NULL, &message_type, &error_message, cb, userdata);
 250                 if (r < 0)
 251                         return r;
 252         }
 253
 254         if (message_type == 0)
 255                 return -ENOMSG;
 256
 257         if (_error_message && IN_SET(message_type, DHCP_NAK, DHCP_DECLINE)) {
 258                 *_error_message = error_message;
 259                 error_message = NULL;
 260         }
 261
 262         return message_type;
 263 }