ServiceRegistration/srp-simple.c

   1 /* srp-simple.c
   2  *
   3  * Copyright (c) 2018 Apple Computer, Inc. All rights reserved.
   4  *
   5  * Licensed under the Apache License, Version 2.0 (the "License");
   6  * you may not use this file except in compliance with the License.
   7  * You may obtain a copy of the License at
   8  *
   9  *     http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  *
  17  * Simple Service Registration Protocol Client
  18  *
  19  * This is intended for the constrained node solution for SRP.   It's intended to be flexible and
  20  * understandable while linking in the minimum possible support code to reduce code size.  It does
  21  * no mallocs, does not put anything big on the stack, and doesn't require an event loop.
  22  */
  23
  24 #include <stdio.h>
  25 #include <arpa/inet.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28
  29 #include "srp.h"
  30 #include "dns-msg.h"
  31 #include "srp-crypto.h"
  32
  33 static void
  34 dns_response_callback(dns_transaction_t *txn)
  35 {
  36 }
  37
  38 int
  39 main(int argc, char **argv)
  40 {
  41     const char *host_name = "thread-demo";
  42     const char *zone_name = "default.service.arpa";
  43     const char *host_fqdn = "thread-demo.default.service.arpa";
  44     const char *service_type = "_ipps._tcp";
  45     const char *a_record = "127.0.0.1";
  46     const char *aaaa_record = "::1";
  47     const char *txt_record = "0";
  48     const char *anycast_address = "127.0.0.1";
  49 //    const char *anycast_address = "73.186.137.119"; // cer.fugue.com
  50     const char *keyfile_name = "srp-simple.key";
  51     int port = 9992;
  52     srp_key_t *key;
  53     dns_wire_t message, response;
  54     uint16_t key_tag;
  55     static dns_transaction_t txn;
  56     dns_towire_state_t *towire = &txn.towire;
  57     dns_name_pointer_t p_host_name;
  58     dns_name_pointer_t p_zone_name;
  59     dns_name_pointer_t p_service_name;
  60     dns_name_pointer_t p_service_instance_name;
  61     int line;
  62
  63     key = srp_load_keypair(keyfile_name);
  64     if (key == NULL) {
  65         key = srp_generate_key();
  66         if (key == NULL) {
  67             printf("Unable to load or generate a key.");
  68             exit(1);
  69         }
  70         if (!srp_write_key_to_file(keyfile_name, key)) {
  71             printf("Unable to safe generated key.");
  72             exit(1);
  73         }
  74     }
  75
  76 #define CH if (towire->error) { line = __LINE__; goto fail; }
  77
  78     // Generate a random UUID.
  79 #ifdef NOTYET
  80     message.id = srp_random16();
  81 #else
  82     srandomdev();
  83     message.id = (uint32_t)(random()) & 65535;
  84 #endif
  85     message.bitfield = 0;
  86     dns_qr_set(&message, dns_qr_query);
  87     dns_opcode_set(&message, dns_opcode_update);
  88
  89     // Message data...
  90     memset(&txn, 0, sizeof txn);
  91     towire->p = &message.data[0];  // We start storing RR data here.
  92     towire->lim = &message.data[DNS_DATA_SIZE]; // This is the limit to how much we can store.
  93     towire->message = &message;
  94     txn.response = &response;
  95     txn.response_length = (int)(sizeof response);
  96
  97     message.qdcount = htons(1); // ZOCOUNT = 1
  98     // Copy in Zone name (and save pointer)
  99     // ZTYPE = SOA
 100     // ZCLASS = IN
 101     dns_full_name_to_wire(&p_zone_name, towire, zone_name); CH;
 102     dns_u16_to_wire(towire, dns_rrtype_soa); CH;
 103     dns_u16_to_wire(towire, dns_qclass_in); CH;
 104
 105     message.ancount = 0;
 106     // PRCOUNT = 0
 107
 108     message.nscount = 0;
 109     // UPCOUNT = ...
 110
 111     // Host Description:
 112     //  * Delete all RRsets from <hostname>; remember the pointer to hostname
 113     //      NAME = hostname label followed by pointer to SOA name.
 114     //      TYPE = ANY
 115     //      CLASS = ANY
 116     //      TTL = 0
 117     //      RDLENGTH = 0
 118     dns_name_to_wire(&p_host_name, towire, host_name); CH;
 119     dns_pointer_to_wire(&p_host_name, towire, &p_zone_name); CH;
 120     dns_u16_to_wire(towire, dns_rrtype_any); CH;
 121     dns_u16_to_wire(towire, dns_qclass_any); CH;
 122     dns_ttl_to_wire(towire, 0); CH;
 123     dns_u16_to_wire(towire, 0); CH;
 124     message.nscount++;
 125     //  * Add either or both of an A or AAAA RRset, each of which contains one
 126     //    or more A or AAAA RRs.
 127     //      NAME = pointer to hostname from Delete (above)
 128     //      TYPE = A or AAAA
 129     //      CLASS = IN
 130     //      TTL = 3600 ?
 131     //      RDLENGTH = number of RRs * RR length (4 or 16)
 132     //      RDATA = <the data>
 133     dns_pointer_to_wire(NULL, towire, &p_host_name); CH;
 134     dns_u16_to_wire(towire, dns_rrtype_a); CH;
 135     dns_u16_to_wire(towire, dns_qclass_in); CH;
 136     dns_ttl_to_wire(towire, 3600); CH;
 137     dns_rdlength_begin(towire); CH;
 138     dns_rdata_a_to_wire(towire, a_record); CH;
 139     dns_rdlength_end(towire); CH;
 140     message.nscount++;
 141
 142     dns_pointer_to_wire(NULL, towire, &p_host_name); CH;
 143     dns_u16_to_wire(towire, dns_rrtype_aaaa); CH;
 144     dns_u16_to_wire(towire, dns_qclass_in); CH;
 145     dns_ttl_to_wire(towire, 3600); CH;
 146     dns_rdlength_begin(towire); CH;
 147     dns_rdata_aaaa_to_wire(towire, aaaa_record); CH;
 148     dns_rdlength_end(towire); CH;
 149     message.nscount++;
 150
 151     //  * Exactly one KEY RR:
 152     //      NAME = pointer to hostname from Delete (above)
 153     //      TYPE = KEY
 154     //      CLASS = IN
 155     //      TTL = 3600
 156     //      RDLENGTH = length of key + 4 (32 bits)
 157     //      RDATA = <flags(16) = 0000 0010 0000 0001, protocol(8) = 3, algorithm(8) = 8?, public key(variable)>
 158     dns_pointer_to_wire(NULL, towire, &p_host_name); CH;
 159     dns_u16_to_wire(towire, dns_rrtype_key); CH;
 160     dns_u16_to_wire(towire, dns_qclass_in); CH;
 161     dns_ttl_to_wire(towire, 3600); CH;
 162     dns_rdlength_begin(towire); CH;
 163     key_tag = dns_rdata_key_to_wire(towire, 0, 2, 1, key); CH;
 164     dns_rdlength_end(towire); CH;
 165     message.nscount++;
 166
 167     // Service Discovery:
 168     //   * Update PTR RR
 169     //     NAME = service name (_a._b.service.arpa)
 170     //     TYPE = PTR
 171     //     CLASS = IN
 172     //     TTL = 3600
 173     //     RDLENGTH = 2
 174     //     RDATA = service instance name
 175     dns_name_to_wire(&p_service_name, towire, service_type); CH;
 176     dns_pointer_to_wire(&p_service_name, towire, &p_zone_name); CH;
 177     dns_u16_to_wire(towire, dns_rrtype_ptr); CH;
 178     dns_u16_to_wire(towire, dns_qclass_in); CH;
 179     dns_ttl_to_wire(towire, 3600); CH;
 180     dns_rdlength_begin(towire); CH;
 181     dns_name_to_wire(&p_service_instance_name, towire, host_name); CH;
 182     dns_pointer_to_wire(&p_service_instance_name, towire, &p_service_name); CH;
 183     dns_rdlength_end(towire); CH;
 184     message.nscount++;
 185
 186     // Service Description:
 187     //   * Delete all RRsets from service instance name
 188     //      NAME = service instance name (save pointer to service name, which is the second label)
 189     //      TYPE = ANY
 190     //      CLASS = ANY
 191     //      TTL = 0
 192     //      RDLENGTH = 0
 193     dns_pointer_to_wire(NULL, towire, &p_service_instance_name); CH;
 194     dns_u16_to_wire(towire, dns_rrtype_any); CH;
 195     dns_u16_to_wire(towire, dns_qclass_any); CH;
 196     dns_ttl_to_wire(towire, 0); CH;
 197     dns_u16_to_wire(towire, 0); CH;
 198     message.nscount++;
 199
 200     //   * Add one SRV RRset pointing to Host Description
 201     //      NAME = pointer to service instance name from above
 202     //      TYPE = SRV
 203     //      CLASS = IN
 204     //      TTL = 3600
 205     //      RDLENGTH = 8
 206     //      RDATA = <priority(16) = 0, weight(16) = 0, port(16) = service port, target = pointer to hostname>
 207     dns_pointer_to_wire(NULL, towire, &p_service_instance_name); CH;
 208     dns_u16_to_wire(towire, dns_rrtype_srv); CH;
 209     dns_u16_to_wire(towire, dns_qclass_in); CH;
 210     dns_ttl_to_wire(towire, 3600); CH;
 211     dns_rdlength_begin(towire); CH;
 212     dns_u16_to_wire(towire, 0); // priority CH;
 213     dns_u16_to_wire(towire, 0); // weight CH;
 214     dns_u16_to_wire(towire, port); // port CH;
 215     dns_pointer_to_wire(NULL, towire, &p_host_name); CH;
 216     dns_rdlength_end(towire); CH;
 217     message.nscount++;
 218
 219     //   * Add one or more TXT records
 220     //      NAME = pointer to service instance name from above
 221     //      TYPE = TXT
 222     //      CLASS = IN
 223     //      TTL = 3600
 224     //      RDLENGTH = <length of text>
 225     //      RDATA = <text>
 226     dns_pointer_to_wire(NULL, towire, &p_service_instance_name); CH;
 227     dns_u16_to_wire(towire, dns_rrtype_txt); CH;
 228     dns_u16_to_wire(towire, dns_qclass_in); CH;
 229     dns_ttl_to_wire(towire, 3600); CH;
 230     dns_rdlength_begin(towire); CH;
 231     dns_rdata_txt_to_wire(towire, txt_record); CH;
 232     dns_rdlength_end(towire); CH;
 233     message.nscount++;
 234     message.nscount = htons(message.nscount);
 235
 236     // What about services with more than one name?   Are these multiple service descriptions?
 237
 238     // ARCOUNT = 2
 239     //   EDNS(0) options
 240     //     ...
 241     //   SIG(0)
 242
 243     message.arcount = htons(1);
 244     dns_edns0_header_to_wire(towire, DNS_MAX_UDP_PAYLOAD, 0, 0, 1); CH;   // XRCODE = 0; VERSION = 0; DO=1
 245     dns_rdlength_begin(towire); CH;
 246     dns_u16_to_wire(towire, dns_opt_update_lease); CH;  // OPTION-CODE
 247     dns_edns0_option_begin(towire); CH;                 // OPTION-LENGTH
 248     dns_u32_to_wire(towire, 3600); CH;                  // LEASE (1 hour)
 249     dns_u32_to_wire(towire, 604800); CH;                // KEY-LEASE (7 days)
 250     dns_edns0_option_end(towire); CH;                   // Now we know OPTION-LENGTH
 251     dns_rdlength_end(towire); CH;
 252
 253     dns_sig0_signature_to_wire(towire, key, key_tag, &p_host_name, host_fqdn); CH;
 254     // The signature is computed before counting the signature RR in the header counts.
 255     message.arcount = htons(ntohs(message.arcount) + 1);
 256
 257     // Send the update
 258     if (dns_send_to_server(&txn, anycast_address, 53, dns_response_callback) < 0) {
 259         line = __LINE__;
 260     fail:
 261         printf("dns_send_to_server failed: %s at line %d\n", strerror(towire->error), line);
 262     }
 263 }
 264
 265 // Local Variables:
 266 // mode: C
 267 // tab-width: 4
 268 // c-file-style: "bsd"
 269 // c-basic-offset: 4
 270 // fill-column: 108
 271 // indent-tabs-mode: nil
 272 // End: