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