The Tcpdump Group git mirrors - libpcap/blob - rpcap-protocol.c

   1 /*
   2  * Copyright (c) 2002 - 2005 NetGroup, Politecnico di Torino (Italy)
   3  * Copyright (c) 2005 - 2008 CACE Technologies, Davis (California)
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  * notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  * notice, this list of conditions and the following disclaimer in the
  14  * documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the Politecnico di Torino, CACE Technologies
  16  * nor the names of its contributors may be used to endorse or promote
  17  * products derived from this software without specific prior written
  18  * permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  21  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  23  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  24  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  25  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  26  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  30  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  *
  32  */
  33
  34 #ifdef HAVE_CONFIG_H
  35 #include <config.h>
  36 #endif
  37
  38 #include <string.h>             /* for strlen(), ... */
  39 #include <stdlib.h>             /* for malloc(), free(), ... */
  40 #include <stdarg.h>             /* for functions with variable number of arguments */
  41 #include <errno.h>              /* for the errno variable */
  42 #include "sockutils.h"
  43 #include "portability.h"
  44 #include "rpcap-protocol.h"
  45 #include <pcap/pcap.h>
  46
  47 /*
  48  * This file contains functions used both by the rpcap client and the
  49  * rpcap daemon.
  50  */
  51
  52 /*
  53  * This function checks whether the version contained into the message is
  54  * compatible with the one handled by this implementation.
  55  *
  56  * Right now, this function does not have any sophisticated task: if the
  57  * versions are different, it returns -1 and it discards the message.
  58  * If new versions of the protocol are created, there will need to be
  59  * a negotiation phase early in the process of connecting to our peer,
  60  * so that the highest version supported by both sides can be used.
  61  *
  62  * \param sock: the socket that has to be used to receive data. This
  63  * function can read data from socket in case the version contained into
  64  * the message is not compatible with ours. In that case, all the message
  65  * is purged from the socket, so that the following recv() calls will
  66  * return a new (clean) message.
  67  *
  68  * \param header: a pointer to and 'rpcap_header' structure that keeps
  69  * the data received from the network (still in network byte order) and
  70  * that has to be checked.
  71  *
  72  * \param errbuf: a pointer to a user-allocated buffer (of size
  73  * PCAP_ERRBUF_SIZE) that will contain the error message (in case there
  74  * is one). The error message is "incompatible version".
  75  *
  76  * \return '0' if everything is fine, '-1' if some errors occurred. The
  77  * error message is returned in the 'errbuf' variable.
  78  */
  79 int
  80 rpcap_checkver(SOCKET sock, struct rpcap_header *header, char *errbuf)
  81 {
  82         /*
  83          * This is a sample function.
  84          *
  85          * In the real world, you have to check the type code,
  86          * and decide accordingly.
  87          */
  88         if (header->ver != RPCAP_VERSION)
  89         {
  90                 pcap_snprintf(errbuf, PCAP_ERRBUF_SIZE, "Incompatible version number: message discarded.");
  91
  92                 /* we already have an error, so please discard this one */
  93                 sock_discard(sock, ntohl(header->plen), NULL, 0);
  94                 return -1;
  95         }
  96
  97         return 0;
  98 }
  99
 100 /*
 101  * This function sends a RPCAP error to our peer.
 102  *
 103  * It has to be called when the main program detects an error.
 104  * It will send to our peer the 'buffer' specified by the user.
 105  * This function *does not* request a RPCAP CLOSE connection. A CLOSE
 106  * command must be sent explicitly by the program, since we do not know
 107  * whether the error can be recovered in some way or if it is a
 108  * non-recoverable one.
 109  *
 110  * \param sock: the socket we are currently using.
 111  *
 112  * \param error: an user-allocated (and '0' terminated) buffer that contains
 113  * the error description that has to be transmitted to our peer. The
 114  * error message cannot be longer than PCAP_ERRBUF_SIZE.
 115  *
 116  * \param errcode: a integer which tells the other party the type of error
 117  * we had; currently is is not too much used.
 118  *
 119  * \param errbuf: a pointer to a user-allocated buffer (of size
 120  * PCAP_ERRBUF_SIZE) that will contain the error message (in case there
 121  * is one). It could be network problem.
 122  *
 123  * \return '0' if everything is fine, '-1' if some errors occurred. The
 124  * error message is returned in the 'errbuf' variable.
 125  */
 126 int
 127 rpcap_senderror(SOCKET sock, char *error, unsigned short errcode, char *errbuf)
 128 {
 129         char sendbuf[RPCAP_NETBUF_SIZE];        /* temporary buffer in which data to be sent is buffered */
 130         int sendbufidx = 0;                     /* index which keeps the number of bytes currently buffered */
 131         uint16 length;
 132
 133         length = (uint16)strlen(error);
 134
 135         if (length > PCAP_ERRBUF_SIZE)
 136                 length = PCAP_ERRBUF_SIZE;
 137
 138         rpcap_createhdr((struct rpcap_header *) sendbuf, RPCAP_MSG_ERROR, errcode, length);
 139
 140         if (sock_bufferize(NULL, sizeof(struct rpcap_header), NULL, &sendbufidx,
 141                 RPCAP_NETBUF_SIZE, SOCKBUF_CHECKONLY, errbuf, PCAP_ERRBUF_SIZE))
 142                 return -1;
 143
 144         if (sock_bufferize(error, length, sendbuf, &sendbufidx,
 145                 RPCAP_NETBUF_SIZE, SOCKBUF_BUFFERIZE, errbuf, PCAP_ERRBUF_SIZE))
 146                 return -1;
 147
 148         if (sock_send(sock, sendbuf, sendbufidx, errbuf, PCAP_ERRBUF_SIZE))
 149                 return -1;
 150
 151         return 0;
 152 }
 153
 154 /*
 155  * This function fills in a structure of type rpcap_header.
 156  *
 157  * It is provided just because the creation of an rpcap header is a common
 158  * task. It accepts all the values that appears into an rpcap_header, and
 159  * it puts them in place using the proper hton() calls.
 160  *
 161  * \param header: a pointer to a user-allocated buffer which will contain
 162  * the serialized header, ready to be sent on the network.
 163  *
 164  * \param type: a value (in the host by order) which will be placed into the
 165  * header.type field and that represents the type of the current message.
 166  *
 167  * \param value: a value (in the host by order) which will be placed into
 168  * the header.value field and that has a message-dependent meaning.
 169  *
 170  * \param length: a value (in the host by order) which will be placed into
 171  * the header.length field, representing the payload length of the message.
 172  *
 173  * \return Nothing. The serialized header is returned into the 'header'
 174  * variable.
 175  */
 176 void
 177 rpcap_createhdr(struct rpcap_header *header, uint8 type, uint16 value, uint32 length)
 178 {
 179         memset(header, 0, sizeof(struct rpcap_header));
 180
 181         header->ver = RPCAP_VERSION;
 182         header->type = type;
 183         header->value = htons(value);
 184         header->plen = htonl(length);
 185 }
 186
 187 /*
 188  * This function checks whether the header of the received message is correct.
 189  *
 190  * It is a way to easily check if the message received, in a certain state
 191  * of the RPCAP protocol Finite State Machine, is valid. This function accepts,
 192  * as a parameter, the list of message types that are allowed in a certain
 193  * situation, and it returns the one that occurs.
 194  *
 195  * \param errbuf: a pointer to a user-allocated buffer (of size
 196  * PCAP_ERRBUF_SIZE) that will contain the error message (in case there
 197  * is one). It could either be a problem that occurred inside this function
 198  * (e.g. a network problem in case it tries to send an error to our peer
 199  * and the send() call fails), an error message thathas been sent to us
 200  * from the other party, or a version error (the message received has a
 201  * version number that is incompatible with ours).
 202  *
 203  * \param sock: the socket that has to be used to receive data. This
 204  * function can read data from socket in case the version contained into
 205  * the message is not compatible with ours. In that case, all the message
 206  * is purged from the socket, so that the following recv() calls will
 207  * return a new message.
 208  *
 209  * \param header: a pointer to and 'rpcap_header' structure that keeps
 210  * the data received from the network (still in network byte order) and
 211  * that has to be checked.
 212  *
 213  * \param first: this function has a variable number of parameters. From
 214  * this point on, all the messages that are valid in this context must be
 215  * passed as parameters.  The message type list must be terminated with a
 216  * '0' value, the null message type, which means 'no more types to check'.
 217  * The RPCAP protocol does not define anything with message type equal to
 218  * zero, so there is no ambiguity in using this value as a list terminator.
 219  *
 220  * \return The message type of the message that has been detected. In case
 221  * of errors (e.g. the header contains a type that is not listed among the
 222  * allowed types), this function will return the following codes:
 223  * - (-1) if the version is incompatible.
 224  * - (-2) if the code is not among the one listed into the parameters list
 225  * - (-3) if a network error (connection reset, ...)
 226  * - RPCAP_MSG_ERROR if the message is an error message (it follows that
 227  * the RPCAP_MSG_ERROR could not be present in the allowed message-types
 228  * list, because this function checks for errors anyway)
 229  *
 230  * In case either the version is incompatible or nothing matches (i.e. it
 231  * returns '-1' or '-2'), it discards the message body (i.e. it reads the
 232  * remaining part of the message from the network and it discards it) so
 233  * that the application is ready to receive a new message.
 234  */
 235 int
 236 rpcap_checkmsg(char *errbuf, SOCKET sock, struct rpcap_header *header, uint8 first, ...)
 237 {
 238         va_list ap;
 239         uint8 type;
 240         int32 len;
 241
 242         va_start(ap, first);
 243
 244         /* Check if the present version of the protocol can handle this message */
 245         if (rpcap_checkver(sock, header, errbuf))
 246         {
 247                 SOCK_ASSERT(errbuf, 1);
 248
 249                 va_end(ap);
 250                 return -1;
 251         }
 252
 253         type = first;
 254
 255         while (type != 0)
 256         {
 257                 /*
 258                  * The message matches with one of the types listed
 259                  * There is no need of conversions since both values are uint8
 260                  *
 261                  * Check if the other side reported an error.
 262                  * If yes, it retrieves it and it returns it back to the caller
 263                  */
 264                 if (header->type == RPCAP_MSG_ERROR)
 265                 {
 266                         len = ntohl(header->plen);
 267
 268                         if (len >= PCAP_ERRBUF_SIZE)
 269                         {
 270                                 if (sock_recv(sock, errbuf, PCAP_ERRBUF_SIZE - 1, SOCK_RECEIVEALL_YES, errbuf, PCAP_ERRBUF_SIZE))
 271                                         return -3;
 272
 273                                 sock_discard(sock, len - (PCAP_ERRBUF_SIZE - 1), NULL, 0);
 274
 275                                 /* Put '\0' at the end of the string */
 276                                 errbuf[PCAP_ERRBUF_SIZE - 1] = 0;
 277                         }
 278                         else
 279                         {
 280                                 if (sock_recv(sock, errbuf, len, SOCK_RECEIVEALL_YES, errbuf, PCAP_ERRBUF_SIZE) == -1)
 281                                         return -3;
 282
 283                                 /* Put '\0' at the end of the string */
 284                                 errbuf[len] = 0;
 285                         }
 286
 287                         va_end(ap);
 288                         return header->type;
 289                 }
 290
 291                 if (header->type == type)
 292                 {
 293                         va_end(ap);
 294                         return header->type;
 295                 }
 296
 297                 /* get next argument */
 298                 type = va_arg(ap, int);
 299         }
 300
 301         /* we already have an error, so please discard this one */
 302         sock_discard(sock, ntohl(header->plen), NULL, 0);
 303
 304         pcap_snprintf(errbuf, PCAP_ERRBUF_SIZE, "The other endpoint sent a message that is not allowed here.");
 305         SOCK_ASSERT(errbuf, 1);
 306
 307         va_end(ap);
 308         return -2;
 309 }