src/protocol.c

   1 /*
   2     protocol.c -- handle the meta-protocol, basic functions
   3     Copyright (C) 1999-2005 Ivo Timmermans,
   4                   2000-2016 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "conf.h"
  24 #include "connection.h"
  25 #include "logger.h"
  26 #include "meta.h"
  27 #include "protocol.h"
  28 #include "utils.h"
  29 #include "xalloc.h"
  30
  31 bool tunnelserver = false;
  32 bool strictsubnets = false;
  33
  34 /* Jumptable for the request handlers */
  35
  36 static bool (*request_handlers[])(connection_t *) = {
  37         id_h, metakey_h, challenge_h, chal_reply_h, ack_h,
  38         NULL, NULL, NULL,
  39         ping_h, pong_h,
  40         add_subnet_h, del_subnet_h,
  41         add_edge_h, del_edge_h,
  42         key_changed_h, req_key_h, ans_key_h, tcppacket_h,
  43 };
  44
  45 /* Request names */
  46
  47 static char (*request_name[]) = {
  48         "ID", "METAKEY", "CHALLENGE", "CHAL_REPLY", "ACK",
  49         "STATUS", "ERROR", "TERMREQ",
  50         "PING", "PONG",
  51         "ADD_SUBNET", "DEL_SUBNET",
  52         "ADD_EDGE", "DEL_EDGE", "KEY_CHANGED", "REQ_KEY", "ANS_KEY", "PACKET",
  53 };
  54
  55 static avl_tree_t *past_request_tree;
  56
  57 bool check_id(const char *id) {
  58         for(; *id; id++)
  59                 if(!isalnum(*id) && *id != '_') {
  60                         return false;
  61                 }
  62
  63         return true;
  64 }
  65
  66 /* Generic request routines - takes care of logging and error
  67    detection as well */
  68
  69 bool send_request(connection_t *c, const char *format, ...) {
  70         va_list args;
  71         char buffer[MAXBUFSIZE];
  72         int len, request = 0;
  73
  74         /* Use vsnprintf instead of vxasprintf: faster, no memory
  75            fragmentation, cleanup is automatic, and there is a limit on the
  76            input buffer anyway */
  77
  78         va_start(args, format);
  79         len = vsnprintf(buffer, sizeof(buffer), format, args);
  80         buffer[sizeof(buffer) - 1] = 0;
  81         va_end(args);
  82
  83         if(len < 0 || (size_t)len > sizeof(buffer) - 1) {
  84                 logger(LOG_ERR, "Output buffer overflow while sending request to %s (%s)",
  85                        c->name, c->hostname);
  86                 return false;
  87         }
  88
  89         ifdebug(PROTOCOL) {
  90                 sscanf(buffer, "%d", &request);
  91                 ifdebug(META)
  92                 logger(LOG_DEBUG, "Sending %s to %s (%s): %s",
  93                        request_name[request], c->name, c->hostname, buffer);
  94                 else
  95                         logger(LOG_DEBUG, "Sending %s to %s (%s)", request_name[request],
  96                                c->name, c->hostname);
  97         }
  98
  99         buffer[len++] = '\n';
 100
 101         if(c == everyone) {
 102                 broadcast_meta(NULL, buffer, len);
 103                 return true;
 104         } else {
 105                 return send_meta(c, buffer, len);
 106         }
 107 }
 108
 109 void forward_request(connection_t *from) {
 110         int request;
 111
 112         ifdebug(PROTOCOL) {
 113                 sscanf(from->buffer, "%d", &request);
 114                 ifdebug(META)
 115                 logger(LOG_DEBUG, "Forwarding %s from %s (%s): %s",
 116                        request_name[request], from->name, from->hostname,
 117                        from->buffer);
 118                 else
 119                         logger(LOG_DEBUG, "Forwarding %s from %s (%s)",
 120                                request_name[request], from->name, from->hostname);
 121         }
 122
 123         from->buffer[from->reqlen - 1] = '\n';
 124
 125         broadcast_meta(from, from->buffer, from->reqlen);
 126 }
 127
 128 bool receive_request(connection_t *c) {
 129         int request;
 130
 131         if(sscanf(c->buffer, "%d", &request) == 1) {
 132                 if((request < 0) || (request >= LAST) || !request_handlers[request]) {
 133                         ifdebug(META)
 134                         logger(LOG_DEBUG, "Unknown request from %s (%s): %s",
 135                                c->name, c->hostname, c->buffer);
 136                         else
 137                                 logger(LOG_ERR, "Unknown request from %s (%s)",
 138                                        c->name, c->hostname);
 139
 140                         return false;
 141                 } else {
 142                         ifdebug(PROTOCOL) {
 143                                 ifdebug(META)
 144                                 logger(LOG_DEBUG, "Got %s from %s (%s): %s",
 145                                        request_name[request], c->name, c->hostname,
 146                                        c->buffer);
 147                                 else
 148                                         logger(LOG_DEBUG, "Got %s from %s (%s)",
 149                                                request_name[request], c->name, c->hostname);
 150                         }
 151                 }
 152
 153                 if((c->allow_request != ALL) && (c->allow_request != request)) {
 154                         logger(LOG_ERR, "Unauthorized request from %s (%s)", c->name,
 155                                c->hostname);
 156                         return false;
 157                 }
 158
 159                 if(!request_handlers[request](c)) {
 160                         /* Something went wrong. Probably scriptkiddies. Terminate. */
 161
 162                         logger(LOG_ERR, "Error while processing %s from %s (%s)",
 163                                request_name[request], c->name, c->hostname);
 164                         return false;
 165                 }
 166         } else {
 167                 logger(LOG_ERR, "Bogus data received from %s (%s)",
 168                        c->name, c->hostname);
 169                 return false;
 170         }
 171
 172         return true;
 173 }
 174
 175 static int past_request_compare(const past_request_t *a, const past_request_t *b) {
 176         return strcmp(a->request, b->request);
 177 }
 178
 179 static void free_past_request(past_request_t *r) {
 180         if(r->request) {
 181                 free(r->request);
 182         }
 183
 184         free(r);
 185 }
 186
 187 void init_requests(void) {
 188         past_request_tree = avl_alloc_tree((avl_compare_t) past_request_compare, (avl_action_t) free_past_request);
 189 }
 190
 191 void exit_requests(void) {
 192         avl_delete_tree(past_request_tree);
 193 }
 194
 195 bool seen_request(char *request) {
 196         past_request_t *new, p = {};
 197
 198         p.request = request;
 199
 200         if(avl_search(past_request_tree, &p)) {
 201                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Already seen request");
 202                 return true;
 203         } else {
 204                 new = xmalloc(sizeof(*new));
 205                 new->request = xstrdup(request);
 206                 new->firstseen = now;
 207                 avl_insert(past_request_tree, new);
 208                 return false;
 209         }
 210 }
 211
 212 void age_past_requests(void) {
 213         avl_node_t *node, *next;
 214         past_request_t *p;
 215         int left = 0, deleted = 0;
 216
 217         for(node = past_request_tree->head; node; node = next) {
 218                 next = node->next;
 219                 p = node->data;
 220
 221                 if(p->firstseen + pinginterval <= now) {
 222                         avl_delete_node(past_request_tree, node), deleted++;
 223                 } else {
 224                         left++;
 225                 }
 226         }
 227
 228         if(left || deleted)
 229                 ifdebug(SCARY_THINGS) logger(LOG_DEBUG, "Aging past requests: deleted %d, left %d",
 230                                              deleted, left);
 231 }