networking/udhcp/options.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * options.c -- DHCP server option packet tools
   4  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   5  *
   6  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   7  */
   8
   9 #include "common.h"
  10 #include "dhcpd.h"
  11 #include "options.h"
  12
  13
  14 /* Supported options are easily added here */
  15 const struct dhcp_option dhcp_options[] = {
  16         /* flags                                    code */
  17         { OPTION_IP                   | OPTION_REQ, 0x01 }, /* DHCP_SUBNET        */
  18         { OPTION_S32                              , 0x02 }, /* DHCP_TIME_OFFSET   */
  19         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x03 }, /* DHCP_ROUTER        */
  20         { OPTION_IP | OPTION_LIST                 , 0x04 }, /* DHCP_TIME_SERVER   */
  21         { OPTION_IP | OPTION_LIST                 , 0x05 }, /* DHCP_NAME_SERVER   */
  22         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x06 }, /* DHCP_DNS_SERVER    */
  23         { OPTION_IP | OPTION_LIST                 , 0x07 }, /* DHCP_LOG_SERVER    */
  24         { OPTION_IP | OPTION_LIST                 , 0x08 }, /* DHCP_COOKIE_SERVER */
  25         { OPTION_IP | OPTION_LIST                 , 0x09 }, /* DHCP_LPR_SERVER    */
  26         { OPTION_STRING               | OPTION_REQ, 0x0c }, /* DHCP_HOST_NAME     */
  27         { OPTION_U16                              , 0x0d }, /* DHCP_BOOT_SIZE     */
  28         { OPTION_STRING | OPTION_LIST | OPTION_REQ, 0x0f }, /* DHCP_DOMAIN_NAME   */
  29         { OPTION_IP                               , 0x10 }, /* DHCP_SWAP_SERVER   */
  30         { OPTION_STRING                           , 0x11 }, /* DHCP_ROOT_PATH     */
  31         { OPTION_U8                               , 0x17 }, /* DHCP_IP_TTL        */
  32         { OPTION_U16                              , 0x1a }, /* DHCP_MTU           */
  33         { OPTION_IP                   | OPTION_REQ, 0x1c }, /* DHCP_BROADCAST     */
  34         { OPTION_STRING                           , 0x28 }, /* nisdomain          */
  35         { OPTION_IP | OPTION_LIST                 , 0x29 }, /* nissrv             */
  36         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x2a }, /* DHCP_NTP_SERVER    */
  37         { OPTION_IP | OPTION_LIST                 , 0x2c }, /* DHCP_WINS_SERVER   */
  38         { OPTION_IP                               , 0x32 }, /* DHCP_REQUESTED_IP  */
  39         { OPTION_U32                              , 0x33 }, /* DHCP_LEASE_TIME    */
  40         { OPTION_U8                               , 0x35 }, /* dhcptype           */
  41         { OPTION_IP                               , 0x36 }, /* DHCP_SERVER_ID     */
  42         { OPTION_STRING                           , 0x38 }, /* DHCP_MESSAGE       */
  43         { OPTION_STRING                           , 0x3C }, /* DHCP_VENDOR        */
  44         { OPTION_STRING                           , 0x3D }, /* DHCP_CLIENT_ID     */
  45         { OPTION_STRING                           , 0x42 }, /* tftp               */
  46         { OPTION_STRING                           , 0x43 }, /* bootfile           */
  47         { OPTION_STRING                           , 0x4D }, /* userclass          */
  48 #if ENABLE_FEATURE_UDHCP_RFC3397
  49         { OPTION_STR1035 | OPTION_LIST            , 0x77 }, /* search             */
  50 #endif
  51         /* MSIE's "Web Proxy Autodiscovery Protocol" support */
  52         { OPTION_STRING                           , 0xfc }, /* wpad               */
  53
  54         /* Options below have no match in dhcp_option_strings[],
  55          * are not passed to dhcpc scripts, and cannot be specified
  56          * with "option XXX YYY" syntax in dhcpd config file. */
  57
  58         { OPTION_U16                              , 0x39 }, /* DHCP_MAX_SIZE      */
  59         { } /* zeroed terminating entry */
  60 };
  61
  62 /* Used for converting options from incoming packets to env variables
  63  * for udhcpc stript */
  64 /* Must match dhcp_options[] order */
  65 const char dhcp_option_strings[] ALIGN1 =
  66         "subnet" "\0"      /* DHCP_SUBNET         */
  67         "timezone" "\0"    /* DHCP_TIME_OFFSET    */
  68         "router" "\0"      /* DHCP_ROUTER         */
  69         "timesrv" "\0"     /* DHCP_TIME_SERVER    */
  70         "namesrv" "\0"     /* DHCP_NAME_SERVER    */
  71         "dns" "\0"         /* DHCP_DNS_SERVER     */
  72         "logsrv" "\0"      /* DHCP_LOG_SERVER     */
  73         "cookiesrv" "\0"   /* DHCP_COOKIE_SERVER  */
  74         "lprsrv" "\0"      /* DHCP_LPR_SERVER     */
  75         "hostname" "\0"    /* DHCP_HOST_NAME      */
  76         "bootsize" "\0"    /* DHCP_BOOT_SIZE      */
  77         "domain" "\0"      /* DHCP_DOMAIN_NAME    */
  78         "swapsrv" "\0"     /* DHCP_SWAP_SERVER    */
  79         "rootpath" "\0"    /* DHCP_ROOT_PATH      */
  80         "ipttl" "\0"       /* DHCP_IP_TTL         */
  81         "mtu" "\0"         /* DHCP_MTU            */
  82         "broadcast" "\0"   /* DHCP_BROADCAST      */
  83         "nisdomain" "\0"   /*                     */
  84         "nissrv" "\0"      /*                     */
  85         "ntpsrv" "\0"      /* DHCP_NTP_SERVER     */
  86         "wins" "\0"        /* DHCP_WINS_SERVER    */
  87         "requestip" "\0"   /* DHCP_REQUESTED_IP   */
  88         "lease" "\0"       /* DHCP_LEASE_TIME     */
  89         "dhcptype" "\0"    /*                     */
  90         "serverid" "\0"    /* DHCP_SERVER_ID      */
  91         "message" "\0"     /* DHCP_MESSAGE        */
  92         "vendorclass" "\0" /* DHCP_VENDOR         */
  93         "clientid" "\0"    /* DHCP_CLIENT_ID      */
  94         "tftp" "\0"
  95         "bootfile" "\0"
  96         "userclass" "\0"
  97 #if ENABLE_FEATURE_UDHCP_RFC3397
  98         "search" "\0"
  99 #endif
 100         /* MSIE's "Web Proxy Autodiscovery Protocol" support */
 101         "wpad" "\0"
 102         ;
 103
 104
 105 /* Lengths of the different option types */
 106 const uint8_t dhcp_option_lengths[] ALIGN1 = {
 107         [OPTION_IP] =      4,
 108         [OPTION_IP_PAIR] = 8,
 109         [OPTION_BOOLEAN] = 1,
 110         [OPTION_STRING] =  1,
 111 #if ENABLE_FEATURE_UDHCP_RFC3397
 112         [OPTION_STR1035] = 1,
 113 #endif
 114         [OPTION_U8] =      1,
 115         [OPTION_U16] =     2,
 116         [OPTION_S16] =     2,
 117         [OPTION_U32] =     4,
 118         [OPTION_S32] =     4
 119 };
 120
 121
 122 /* get an option with bounds checking (warning, result is not aligned). */
 123 uint8_t* FAST_FUNC get_option(struct dhcpMessage *packet, int code)
 124 {
 125         uint8_t *optionptr;
 126         int len;
 127         int rem;
 128         int overload = 0;
 129         enum {
 130                 FILE_FIELD101  = FILE_FIELD  * 0x101,
 131                 SNAME_FIELD101 = SNAME_FIELD * 0x101,
 132         };
 133
 134         /* option bytes: [code][len][data1][data2]..[dataLEN] */
 135         optionptr = packet->options;
 136         rem = sizeof(packet->options);
 137         while (1) {
 138                 if (rem <= 0) {
 139                         bb_error_msg("bogus packet, malformed option field");
 140                         return NULL;
 141                 }
 142                 if (optionptr[OPT_CODE] == DHCP_PADDING) {
 143                         rem--;
 144                         optionptr++;
 145                         continue;
 146                 }
 147                 if (optionptr[OPT_CODE] == DHCP_END) {
 148                         if ((overload & FILE_FIELD101) == FILE_FIELD) {
 149                                 /* can use packet->file, and didn't look at it yet */
 150                                 overload |= FILE_FIELD101; /* "we looked at it" */
 151                                 optionptr = packet->file;
 152                                 rem = sizeof(packet->file);
 153                                 continue;
 154                         }
 155                         if ((overload & SNAME_FIELD101) == SNAME_FIELD) {
 156                                 /* can use packet->sname, and didn't look at it yet */
 157                                 overload |= SNAME_FIELD101; /* "we looked at it" */
 158                                 optionptr = packet->sname;
 159                                 rem = sizeof(packet->sname);
 160                                 continue;
 161                         }
 162                         return NULL;
 163                 }
 164                 len = 2 + optionptr[OPT_LEN];
 165                 rem -= len;
 166                 if (rem < 0)
 167                         continue; /* complain and return NULL */
 168
 169                 if (optionptr[OPT_CODE] == code)
 170                         return optionptr + OPT_DATA;
 171
 172                 if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD) {
 173                         overload |= optionptr[OPT_DATA];
 174                         /* fall through */
 175                 }
 176                 optionptr += len;
 177         }
 178         return NULL;
 179 }
 180
 181
 182 /* return the position of the 'end' option (no bounds checking) */
 183 int FAST_FUNC end_option(uint8_t *optionptr)
 184 {
 185         int i = 0;
 186
 187         while (optionptr[i] != DHCP_END) {
 188                 if (optionptr[i] != DHCP_PADDING)
 189                         i += optionptr[i + OPT_LEN] + 1;
 190                 i++;
 191         }
 192         return i;
 193 }
 194
 195
 196 /* add an option string to the options */
 197 /* option bytes: [code][len][data1][data2]..[dataLEN] */
 198 int FAST_FUNC add_option_string(uint8_t *optionptr, uint8_t *string)
 199 {
 200         int end = end_option(optionptr);
 201
 202         /* end position + string length + option code/length + end option */
 203         if (end + string[OPT_LEN] + 2 + 1 >= DHCP_OPTIONS_BUFSIZE) {
 204                 bb_error_msg("option 0x%02x did not fit into the packet",
 205                                 string[OPT_CODE]);
 206                 return 0;
 207         }
 208         DEBUG("adding option 0x%02x", string[OPT_CODE]);
 209         memcpy(optionptr + end, string, string[OPT_LEN] + 2);
 210         optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
 211         return string[OPT_LEN] + 2;
 212 }
 213
 214
 215 /* add a one to four byte option to a packet */
 216 int FAST_FUNC add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
 217 {
 218         const struct dhcp_option *dh;
 219
 220         for (dh = dhcp_options; dh->code; dh++) {
 221                 if (dh->code == code) {
 222                         uint8_t option[6], len;
 223
 224                         option[OPT_CODE] = code;
 225                         len = dhcp_option_lengths[dh->flags & TYPE_MASK];
 226                         option[OPT_LEN] = len;
 227                         if (BB_BIG_ENDIAN)
 228                                 data <<= 8 * (4 - len);
 229                         /* Assignment is unaligned! */
 230                         move_to_unaligned32(&option[OPT_DATA], data);
 231                         return add_option_string(optionptr, option);
 232                 }
 233         }
 234
 235         bb_error_msg("cannot add option 0x%02x", code);
 236         return 0;
 237 }