src/libsystemd-network/dhcp-option.c

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