networking/udhcp/options.c

   1 /*
   2  * options.c -- DHCP server option packet tools
   3  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   4  */
   5
   6 #include <stdlib.h>
   7 #include <string.h>
   8
   9 #include "dhcpd.h"
  10 #include "files.h"
  11 #include "options.h"
  12 #include "common.h"
  13
  14
  15 /* supported options are easily added here */
  16 struct dhcp_option options[] = {
  17         /* name[10]     flags                                   code */
  18         {"subnet",      OPTION_IP | OPTION_REQ,                 0x01},
  19         {"timezone",    OPTION_S32,                             0x02},
  20         {"router",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x03},
  21         {"timesvr",     OPTION_IP | OPTION_LIST,                0x04},
  22         {"namesvr",     OPTION_IP | OPTION_LIST,                0x05},
  23         {"dns",         OPTION_IP | OPTION_LIST | OPTION_REQ,   0x06},
  24         {"logsvr",      OPTION_IP | OPTION_LIST,                0x07},
  25         {"cookiesvr",   OPTION_IP | OPTION_LIST,                0x08},
  26         {"lprsvr",      OPTION_IP | OPTION_LIST,                0x09},
  27         {"hostname",    OPTION_STRING | OPTION_REQ,             0x0c},
  28         {"bootsize",    OPTION_U16,                             0x0d},
  29         {"domain",      OPTION_STRING | OPTION_REQ,             0x0f},
  30         {"swapsvr",     OPTION_IP,                              0x10},
  31         {"rootpath",    OPTION_STRING,                          0x11},
  32         {"ipttl",       OPTION_U8,                              0x17},
  33         {"mtu",         OPTION_U16,                             0x1a},
  34         {"broadcast",   OPTION_IP | OPTION_REQ,                 0x1c},
  35         {"ntpsrv",      OPTION_IP | OPTION_LIST,                0x2a},
  36         {"wins",        OPTION_IP | OPTION_LIST,                0x2c},
  37         {"requestip",   OPTION_IP,                              0x32},
  38         {"lease",       OPTION_U32,                             0x33},
  39         {"dhcptype",    OPTION_U8,                              0x35},
  40         {"serverid",    OPTION_IP,                              0x36},
  41         {"message",     OPTION_STRING,                          0x38},
  42         {"tftp",        OPTION_STRING,                          0x42},
  43         {"bootfile",    OPTION_STRING,                          0x43},
  44         {"",            0x00,                           0x00}
  45 };
  46
  47 /* Lengths of the different option types */
  48 int option_lengths[] = {
  49         [OPTION_IP] =           4,
  50         [OPTION_IP_PAIR] =      8,
  51         [OPTION_BOOLEAN] =      1,
  52         [OPTION_STRING] =       1,
  53         [OPTION_U8] =           1,
  54         [OPTION_U16] =          2,
  55         [OPTION_S16] =          2,
  56         [OPTION_U32] =          4,
  57         [OPTION_S32] =          4
  58 };
  59
  60
  61 /* get an option with bounds checking (warning, not aligned). */
  62 unsigned char *get_option(struct dhcpMessage *packet, int code)
  63 {
  64         int i, length;
  65         unsigned char *optionptr;
  66         int over = 0, done = 0, curr = OPTION_FIELD;
  67
  68         optionptr = packet->options;
  69         i = 0;
  70         length = 308;
  71         while (!done) {
  72                 if (i >= length) {
  73                         LOG(LOG_WARNING, "bogus packet, option fields too long.");
  74                         return NULL;
  75                 }
  76                 if (optionptr[i + OPT_CODE] == code) {
  77                         if (i + 1 + optionptr[i + OPT_LEN] >= length) {
  78                                 LOG(LOG_WARNING, "bogus packet, option fields too long.");
  79                                 return NULL;
  80                         }
  81                         return optionptr + i + 2;
  82                 }
  83                 switch (optionptr[i + OPT_CODE]) {
  84                 case DHCP_PADDING:
  85                         i++;
  86                         break;
  87                 case DHCP_OPTION_OVER:
  88                         if (i + 1 + optionptr[i + OPT_LEN] >= length) {
  89                                 LOG(LOG_WARNING, "bogus packet, option fields too long.");
  90                                 return NULL;
  91                         }
  92                         over = optionptr[i + 3];
  93                         i += optionptr[OPT_LEN] + 2;
  94                         break;
  95                 case DHCP_END:
  96                         if (curr == OPTION_FIELD && over & FILE_FIELD) {
  97                                 optionptr = packet->file;
  98                                 i = 0;
  99                                 length = 128;
 100                                 curr = FILE_FIELD;
 101                         } else if (curr == FILE_FIELD && over & SNAME_FIELD) {
 102                                 optionptr = packet->sname;
 103                                 i = 0;
 104                                 length = 64;
 105                                 curr = SNAME_FIELD;
 106                         } else done = 1;
 107                         break;
 108                 default:
 109                         i += optionptr[OPT_LEN + i] + 2;
 110                 }
 111         }
 112         return NULL;
 113 }
 114
 115
 116 /* return the position of the 'end' option (no bounds checking) */
 117 int end_option(unsigned char *optionptr)
 118 {
 119         int i = 0;
 120
 121         while (optionptr[i] != DHCP_END) {
 122                 if (optionptr[i] == DHCP_PADDING) i++;
 123                 else i += optionptr[i + OPT_LEN] + 2;
 124         }
 125         return i;
 126 }
 127
 128
 129 /* add an option string to the options (an option string contains an option code,
 130  * length, then data) */
 131 int add_option_string(unsigned char *optionptr, unsigned char *string)
 132 {
 133         int end = end_option(optionptr);
 134
 135         /* end position + string length + option code/length + end option */
 136         if (end + string[OPT_LEN] + 2 + 1 >= 308) {
 137                 LOG(LOG_ERR, "Option 0x%02x did not fit into the packet!", string[OPT_CODE]);
 138                 return 0;
 139         }
 140         DEBUG(LOG_INFO, "adding option 0x%02x", string[OPT_CODE]);
 141         memcpy(optionptr + end, string, string[OPT_LEN] + 2);
 142         optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
 143         return string[OPT_LEN] + 2;
 144 }
 145
 146
 147 /* add a one to four byte option to a packet */
 148 int add_simple_option(unsigned char *optionptr, unsigned char code, u_int32_t data)
 149 {
 150         char length = 0;
 151         int i;
 152         unsigned char option[2 + 4];
 153         unsigned char *u8;
 154         u_int16_t *u16;
 155         u_int32_t *u32;
 156         u_int32_t aligned;
 157         u8 = (unsigned char *) &aligned;
 158         u16 = (u_int16_t *) &aligned;
 159         u32 = &aligned;
 160
 161         for (i = 0; options[i].code; i++)
 162                 if (options[i].code == code) {
 163                         length = option_lengths[options[i].flags & TYPE_MASK];
 164                 }
 165
 166         if (!length) {
 167                 DEBUG(LOG_ERR, "Could not add option 0x%02x", code);
 168                 return 0;
 169         }
 170
 171         option[OPT_CODE] = code;
 172         option[OPT_LEN] = length;
 173
 174         switch (length) {
 175                 case 1: *u8 =  data; break;
 176                 case 2: *u16 = data; break;
 177                 case 4: *u32 = data; break;
 178         }
 179         memcpy(option + 2, &aligned, length);
 180         return add_option_string(optionptr, option);
 181 }
 182
 183
 184 /* find option 'code' in opt_list */
 185 struct option_set *find_option(struct option_set *opt_list, char code)
 186 {
 187         while (opt_list && opt_list->data[OPT_CODE] < code)
 188                 opt_list = opt_list->next;
 189
 190         if (opt_list && opt_list->data[OPT_CODE] == code) return opt_list;
 191         else return NULL;
 192 }
 193
 194
 195 /* add an option to the opt_list */
 196 void attach_option(struct option_set **opt_list, struct dhcp_option *option, char *buffer, int length)
 197 {
 198         struct option_set *existing, *new, **curr;
 199
 200         /* add it to an existing option */
 201         if ((existing = find_option(*opt_list, option->code))) {
 202                 DEBUG(LOG_INFO, "Attaching option %s to existing member of list", option->name);
 203                 if (option->flags & OPTION_LIST) {
 204                         if (existing->data[OPT_LEN] + length <= 255) {
 205                                 existing->data = realloc(existing->data,
 206                                                 existing->data[OPT_LEN] + length + 2);
 207                                 memcpy(existing->data + existing->data[OPT_LEN] + 2, buffer, length);
 208                                 existing->data[OPT_LEN] += length;
 209                         } /* else, ignore the data, we could put this in a second option in the future */
 210                 } /* else, ignore the new data */
 211         } else {
 212                 DEBUG(LOG_INFO, "Attaching option %s to list", option->name);
 213
 214                 /* make a new option */
 215                 new = xmalloc(sizeof(struct option_set));
 216                 new->data = xmalloc(length + 2);
 217                 new->data[OPT_CODE] = option->code;
 218                 new->data[OPT_LEN] = length;
 219                 memcpy(new->data + 2, buffer, length);
 220
 221                 curr = opt_list;
 222                 while (*curr && (*curr)->data[OPT_CODE] < option->code)
 223                         curr = &(*curr)->next;
 224
 225                 new->next = *curr;
 226                 *curr = new;
 227         }
 228 }