src/libsystemd-network/dhcp-option.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright (C) 2013 Intel Corporation. All rights reserved.
   6 ***/
   7
   8 #include <errno.h>
   9 #include <stdint.h>
  10 #include <stdio.h>
  11 #include <string.h>
  12
  13 #include "alloc-util.h"
  14 #include "utf8.h"
  15 #include "strv.h"
  16
  17 #include "dhcp-internal.h"
  18
  19 static int option_append(uint8_t options[], size_t size, size_t *offset,
  20                          uint8_t code, size_t optlen, const void *optval) {
  21         assert(options);
  22         assert(offset);
  23
  24         if (code != SD_DHCP_OPTION_END)
  25                 /* always make sure there is space for an END option */
  26                 size--;
  27
  28         switch (code) {
  29
  30         case SD_DHCP_OPTION_PAD:
  31         case SD_DHCP_OPTION_END:
  32                 if (size < *offset + 1)
  33                         return -ENOBUFS;
  34
  35                 options[*offset] = code;
  36                 *offset += 1;
  37                 break;
  38
  39         case SD_DHCP_OPTION_USER_CLASS: {
  40                 size_t len = 0;
  41                 char **s;
  42
  43                 STRV_FOREACH(s, (char **) optval)
  44                         len += strlen(*s) + 1;
  45
  46                 if (size < *offset + len + 2)
  47                         return -ENOBUFS;
  48
  49                 options[*offset] = code;
  50                 options[*offset + 1] =  len;
  51                 *offset += 2;
  52
  53                 STRV_FOREACH(s, (char **) optval) {
  54                         len = strlen(*s);
  55
  56                         if (len > 255)
  57                                 return -ENAMETOOLONG;
  58
  59                         options[*offset] = len;
  60
  61                         memcpy_safe(&options[*offset + 1], *s, len);
  62                         *offset += len + 1;
  63                 }
  64
  65                 break;
  66         }
  67         default:
  68                 if (size < *offset + optlen + 2)
  69                         return -ENOBUFS;
  70
  71                 options[*offset] = code;
  72                 options[*offset + 1] = optlen;
  73
  74                 memcpy_safe(&options[*offset + 2], optval, optlen);
  75                 *offset += optlen + 2;
  76
  77                 break;
  78         }
  79
  80         return 0;
  81 }
  82
  83 int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
  84                        uint8_t overload,
  85                        uint8_t code, size_t optlen, const void *optval) {
  86         size_t file_offset = 0, sname_offset =0;
  87         bool file, sname;
  88         int r;
  89
  90         assert(message);
  91         assert(offset);
  92
  93         file = overload & DHCP_OVERLOAD_FILE;
  94         sname = overload & DHCP_OVERLOAD_SNAME;
  95
  96         if (*offset < size) {
  97                 /* still space in the options array */
  98                 r = option_append(message->options, size, offset, code, optlen, optval);
  99                 if (r >= 0)
 100                         return 0;
 101                 else if (r == -ENOBUFS && (file || sname)) {
 102                         /* did not fit, but we have more buffers to try
 103                            close the options array and move the offset to its end */
 104                         r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 105                         if (r < 0)
 106                                 return r;
 107
 108                         *offset = size;
 109                 } else
 110                         return r;
 111         }
 112
 113         if (overload & DHCP_OVERLOAD_FILE) {
 114                 file_offset = *offset - size;
 115
 116                 if (file_offset < sizeof(message->file)) {
 117                         /* still space in the 'file' array */
 118                         r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
 119                         if (r >= 0) {
 120                                 *offset = size + file_offset;
 121                                 return 0;
 122                         } else if (r == -ENOBUFS && sname) {
 123                                 /* did not fit, but we have more buffers to try
 124                                    close the file array and move the offset to its end */
 125                                 r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
 126                                 if (r < 0)
 127                                         return r;
 128
 129                                 *offset = size + sizeof(message->file);
 130                         } else
 131                                 return r;
 132                 }
 133         }
 134
 135         if (overload & DHCP_OVERLOAD_SNAME) {
 136                 sname_offset = *offset - size - (file ? sizeof(message->file) : 0);
 137
 138                 if (sname_offset < sizeof(message->sname)) {
 139                         /* still space in the 'sname' array */
 140                         r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
 141                         if (r >= 0) {
 142                                 *offset = size + (file ? sizeof(message->file) : 0) + sname_offset;
 143                                 return 0;
 144                         } else {
 145                                 /* no space, or other error, give up */
 146                                 return r;
 147                         }
 148                 }
 149         }
 150
 151         return -ENOBUFS;
 152 }
 153
 154 static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
 155                          uint8_t *message_type, char **error_message, dhcp_option_callback_t cb,
 156                          void *userdata) {
 157         uint8_t code, len;
 158         const uint8_t *option;
 159         size_t offset = 0;
 160
 161         while (offset < buflen) {
 162                 code = options[offset ++];
 163
 164                 switch (code) {
 165                 case SD_DHCP_OPTION_PAD:
 166                         continue;
 167
 168                 case SD_DHCP_OPTION_END:
 169                         return 0;
 170                 }
 171
 172                 if (buflen < offset + 1)
 173                         return -ENOBUFS;
 174
 175                 len = options[offset ++];
 176
 177                 if (buflen < offset + len)
 178                         return -EINVAL;
 179
 180                 option = &options[offset];
 181
 182                 switch (code) {
 183                 case SD_DHCP_OPTION_MESSAGE_TYPE:
 184                         if (len != 1)
 185                                 return -EINVAL;
 186
 187                         if (message_type)
 188                                 *message_type = *option;
 189
 190                         break;
 191
 192                 case SD_DHCP_OPTION_ERROR_MESSAGE:
 193                         if (len == 0)
 194                                 return -EINVAL;
 195
 196                         if (error_message) {
 197                                 _cleanup_free_ char *string = NULL;
 198
 199                                 /* Accept a trailing NUL byte */
 200                                 if (memchr(option, 0, len - 1))
 201                                         return -EINVAL;
 202
 203                                 string = strndup((const char *) option, len);
 204                                 if (!string)
 205                                         return -ENOMEM;
 206
 207                                 if (!ascii_is_valid(string))
 208                                         return -EINVAL;
 209
 210                                 free_and_replace(*error_message, string);
 211                         }
 212
 213                         break;
 214                 case SD_DHCP_OPTION_OVERLOAD:
 215                         if (len != 1)
 216                                 return -EINVAL;
 217
 218                         if (overload)
 219                                 *overload = *option;
 220
 221                         break;
 222
 223                 default:
 224                         if (cb)
 225                                 cb(code, len, option, userdata);
 226
 227                         break;
 228                 }
 229
 230                 offset += len;
 231         }
 232
 233         if (offset < buflen)
 234                 return -EINVAL;
 235
 236         return 0;
 237 }
 238
 239 int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t cb, void *userdata, char **_error_message) {
 240         _cleanup_free_ char *error_message = NULL;
 241         uint8_t overload = 0;
 242         uint8_t message_type = 0;
 243         int r;
 244
 245         if (!message)
 246                 return -EINVAL;
 247
 248         if (len < sizeof(DHCPMessage))
 249                 return -EINVAL;
 250
 251         len -= sizeof(DHCPMessage);
 252
 253         r = parse_options(message->options, len, &overload, &message_type, &error_message, cb, userdata);
 254         if (r < 0)
 255                 return r;
 256
 257         if (overload & DHCP_OVERLOAD_FILE) {
 258                 r = parse_options(message->file, sizeof(message->file), NULL, &message_type, &error_message, cb, userdata);
 259                 if (r < 0)
 260                         return r;
 261         }
 262
 263         if (overload & DHCP_OVERLOAD_SNAME) {
 264                 r = parse_options(message->sname, sizeof(message->sname), NULL, &message_type, &error_message, cb, userdata);
 265                 if (r < 0)
 266                         return r;
 267         }
 268
 269         if (message_type == 0)
 270                 return -ENOMSG;
 271
 272         if (_error_message && IN_SET(message_type, DHCP_NAK, DHCP_DECLINE))
 273                 *_error_message = TAKE_PTR(error_message);
 274
 275         return message_type;
 276 }