5 Author: Pekka Riikonen <priikone@silcnet.org>
7 Copyright (C) 1997 - 2001 Pekka Riikonen
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
21 /****h* silccore/SilcPacketAPI
25 * Implementation of the packet routines for sending and receiving
26 * SILC Packets. These includes the data sending routines and data
27 * reading routines, encrypting and decrypting routines, packet assembling
28 * and packet parsing routines.
35 /* Default byte size of the packet. */
36 #define SILC_PACKET_DEFAULT_SIZE SILC_SOCKET_BUF_SIZE
38 /* Header length without source and destination ID's. */
39 #define SILC_PACKET_HEADER_LEN 8 + 2
41 /* Minimum length of SILC Packet Header. This much is decrypted always
42 when packet is received to be able to get all the relevant data out
44 #define SILC_PACKET_MIN_HEADER_LEN 16 + 2
46 /* Maximum padding length */
47 #define SILC_PACKET_MAX_PADLEN 16
49 /* Minimum packet length */
50 #define SILC_PACKET_MIN_LEN (SILC_PACKET_HEADER_LEN + 1)
52 /* Maximum length of ID */
53 #define SILC_PACKET_MAX_ID_LEN 16
55 /****d* silccore/SilcPacketAPI/SilcPacketType
59 * typedef unsigned char SilcPacketType;
63 * SILC packet type definition and all the packet types.
67 typedef unsigned char SilcPacketType;
69 /* SILC Packet types. */
70 #define SILC_PACKET_NONE 0 /* NULL, never sent */
71 #define SILC_PACKET_DISCONNECT 1 /* Disconnection */
72 #define SILC_PACKET_SUCCESS 2 /* Success */
73 #define SILC_PACKET_FAILURE 3 /* Failure */
74 #define SILC_PACKET_REJECT 4 /* Rejected */
75 #define SILC_PACKET_NOTIFY 5 /* Notify message */
76 #define SILC_PACKET_ERROR 6 /* Error message */
77 #define SILC_PACKET_CHANNEL_MESSAGE 7 /* Message for channel */
78 #define SILC_PACKET_CHANNEL_KEY 8 /* Key of the channel */
79 #define SILC_PACKET_PRIVATE_MESSAGE 9 /* Private message */
80 #define SILC_PACKET_PRIVATE_MESSAGE_KEY 10 /* Private message key*/
81 #define SILC_PACKET_COMMAND 11 /* Command */
82 #define SILC_PACKET_COMMAND_REPLY 12 /* Reply to a command */
83 #define SILC_PACKET_KEY_EXCHANGE 13 /* Start of KE */
84 #define SILC_PACKET_KEY_EXCHANGE_1 14 /* KE1 */
85 #define SILC_PACKET_KEY_EXCHANGE_2 15 /* KE2 */
86 #define SILC_PACKET_CONNECTION_AUTH_REQUEST 16 /* Request of auth meth */
87 #define SILC_PACKET_CONNECTION_AUTH 17 /* Connectinon auth */
88 #define SILC_PACKET_NEW_ID 18 /* Sending new ID */
89 #define SILC_PACKET_NEW_CLIENT 19 /* Client registering */
90 #define SILC_PACKET_NEW_SERVER 20 /* Server registering */
91 #define SILC_PACKET_NEW_CHANNEL 21 /* Channel registering */
92 #define SILC_PACKET_REKEY 22 /* Re-key start */
93 #define SILC_PACKET_REKEY_DONE 23 /* Re-key done */
94 #define SILC_PACKET_HEARTBEAT 24 /* Heartbeat */
95 #define SILC_PACKET_KEY_AGREEMENT 25 /* Key Agreement request */
96 #define SILC_PACKET_RESUME_ROUTER 26 /* Backup router resume */
97 #define SILC_PACKET_FTP 27 /* File Transfer */
99 #define SILC_PACKET_PRIVATE 200 /* Private range start */
100 #define SILC_PACKET_MAX 255 /* RESERVED */
103 /****d* silccore/SilcPacketAPI/SilcPacketVersion
107 * typedef unsigned char SilcPacketVersion;
111 * SILC packet version type definition.
114 typedef unsigned char SilcPacketVersion;
116 /****d* silccore/SilcPacketAPI/SilcPacketFlags
120 * typedef unsigned char SilcPacketFlags;
124 * SILC packet flags type definition and all the packet flags.
128 typedef unsigned char SilcPacketFlags;
130 /* All defined packet flags */
131 #define SILC_PACKET_FLAG_NONE 0x00 /* No flags */
132 #define SILC_PACKET_FLAG_PRIVMSG_KEY 0x01 /* Private message key */
133 #define SILC_PACKET_FLAG_LIST 0x02 /* Packet is a list */
134 #define SILC_PACKET_FLAG_BROADCAST 0x04 /* Packet is a broadcast */
137 /* Rest of flags still available
138 #define SILC_PACKET_FLAG_XXX 0x08
139 #define SILC_PACKET_FLAG_XXX 0x10
140 #define SILC_PACKET_FLAG_XXX 0x20
141 #define SILC_PACKET_FLAG_XXX 0x40
142 #define SILC_PACKET_FLAG_XXX 0x80
145 /****s* silccore/SilcPacketAPI/SilcPacketContext
149 * typedef struct { ... } SilcPacketContext;
153 * In packet sending this is filled and sent to silc_packet_assemble
154 * which then uses it to assemble new packet. In packet reception pointer
155 * to this context is sent to silc_packet_parse which parses the packet
156 * and returns the relevant information to this structure. On packet
157 * reception returned ID's are always the hash values of the ID's from
160 * Short description of the fields following:
166 * SilcPacketType type
168 * Type of the packet. Types are defined below.
170 * SilcPacketFlags flags
172 * Packet flags. Flags are defined above.
174 * unsigned char *src_id
176 * unsigned char src_id_type
178 * Source ID, its length and type. On packet reception retuned ID's
179 * are always the hash values of the ID's from the packet.
181 * unsigned char *dst_id;
183 * unsigned char src_id_type;
185 * Destination ID, its length and type. On packet reception retuned
186 * ID's are always the hash values of the ID's from the packet.
191 * The true lenght of the packet and the padded length of the packet.
192 * These may be set by the caller before calling any of the
193 * silc_packet_* routines. If not provided the library will calculate
198 * Reference counter for this context. The context is freed only
199 * after the reference counter hits zero. The counter is added
200 * calling silc_packet_context_dup and decreased by calling the
201 * silc_packet_context_free.
205 * Packet sequence number.
211 SilcPacketFlags flags;
213 unsigned char *src_id;
215 unsigned char src_id_type;
217 unsigned char *dst_id;
219 unsigned char dst_id_type;
226 SilcSocketConnection sock;
233 /****s* silccore/SilcPacketAPI/SilcPacketParserContext
237 * typedef struct { ... } SilcPacketParserContext;
241 * This context is used in packet reception when silc_packet_receive_process
242 * function calls parser callback that performs the actual packet decryption
243 * and parsing. This context is sent as argument to the parser function.
244 * This context must be free'd by the parser callback function.
246 * Following description of the fields:
248 * SilcPacketContext *packet
250 * The actual packet received from the network. In this phase the
251 * context is not parsed, only the packet->buffer is allocated and
252 * it includes the raw packet data, which is encrypted.
254 * SilcSocketConnection sock
256 * The associated connection.
260 * User context that is sent to the silc_packet_receive_process
261 * function. This usually includes application and connection specific
266 SilcPacketContext *packet;
267 SilcSocketConnection sock;
269 } SilcPacketParserContext;
271 /****f* silccore/SilcPacketAPI/SilcPacketParserCallback
275 * typedef void (*SilcPacketParserCallback)(SilcPacketParserContext
280 * This callback is given to the silc_packet_receive_process function.
281 * The callback is called by the library every time a packet is
282 * received from the network. After the packet has been decrypted
283 * and at least partially parsed it is passed to the application
284 * for further parsing using this callback and the SilcPacketParserContext
285 * context. The application receiving the SilcPacketParserContext
289 typedef void (*SilcPacketParserCallback)(SilcPacketParserContext
292 /****f* silccore/SilcPacketAPI/SilcPacketCheckDecrypt
296 * typedef int (*SilcPacketCheckDecrypt)(SilcPacketType packet_type,
298 * SilcPacketContext *packet,
303 * This callback function relates to the checking whether the packet is
304 * normal packet or special packet and how it should be processed. If
305 * the callback returns TRUE the packet is normal and FALSE if the packet
306 * is special and requires special procesing. Some of the packets in
307 * SILC are special (like channel message packets that are encrypted
308 * using channel specific keys) and requires special processing. That
309 * is the reason for this callback function.
311 * The library will call this function if provided for the
312 * silc_packet_decrypt function. The `packet_type' is the type of
313 * packet received (this is also actually the first time application
314 * receives information of the received packet, next time it receives
315 * it is when the SilcPacketParserCallback function is called),
316 * the `buffer' is the raw packet data the `packet' the allocated
317 * SilcPacketContext that is filled when parsing the packet and `context'
318 * is application specific user context.
321 typedef int (*SilcPacketCheckDecrypt)(SilcPacketType packet_type,
323 SilcPacketContext *packet,
328 /****d* silccore/SilcPacketAPI/SILC_PACKET_LENGTH
332 * #define SILC_PACKET_LENGTH ...
336 * Returns true length of the packet and padded length of the packet.
337 * This is primarily used by the libary in packet parsing phase but
338 * the application may use it as well if needed.
342 #define SILC_PACKET_LENGTH(__packet, __ret_truelen, __ret_padlen) \
344 SILC_GET16_MSB((__ret_truelen), (__packet)->data); \
345 (__ret_padlen) = (((__ret_truelen) - 2) + \
346 SILC_PACKET_MAX_PADLEN) & ~(SILC_PACKET_MAX_PADLEN - 1); \
350 /****d* silccore/SilcPacketAPI/SILC_PACKET_PADLEN
354 * #define SILC_PACKET_PADLEN ...
358 * Returns the length of the padding in the packet. This is used
359 * by various library routines to determine needed padding length.
363 #define SILC_PACKET_PADLEN(__packetlen) \
364 SILC_PACKET_MAX_PADLEN - ((__packetlen) - 2) % SILC_PACKET_MAX_PADLEN;
369 /****f* silccore/SilcPacketAPI/silc_packet_send
373 * int silc_packet_send(SilcSocketConnection sock, int force_send);
377 * Actually sends the packet. This flushes the connections outgoing data
378 * buffer. If data is sent directly to the network this returns the bytes
379 * written, if error occured this returns -1 and if the data could not
380 * be written directly to the network at this time this returns -2, in
381 * which case the data should be queued by the caller and sent at some
382 * later time. If `force_send' is TRUE this attempts to write the data
383 * directly to the network, if FALSE, this returns -2.
386 int silc_packet_send(SilcSocketConnection sock, int force_send);
388 /****f* silccore/SilcPacketAPI/silc_packet_encrypt
392 * void silc_packet_encrypt(SilcCipher cipher, SilcHmac hmac,
393 * SilcBuffer buffer, uint32 len);
397 * Encrypts a packet. This also creates HMAC of the packet before
398 * encryption and adds the HMAC at the end of the buffer. This assumes
399 * that there is enough free space at the end of the buffer to add the
400 * computed HMAC. This is the normal way of encrypting packets, if some
401 * other process of HMAC computing and encryption is needed this function
405 void silc_packet_encrypt(SilcCipher cipher, SilcHmac hmac,
406 SilcBuffer buffer, uint32 len);
408 /****f* silccore/SilcPacketAPI/silc_packet_assemble
412 * void silc_packet_assemble(SilcPacketContext *ctx);
416 * Assembles a new packet to be ready for send out. The buffer sent as
417 * argument must include the data to be sent and it must not be encrypted.
418 * The packet also must have enough free space so that the SILC header
419 * and padding maybe added to the packet. The packet is encrypted after
420 * this function has returned.
422 * The buffer sent as argument should be something like following:
424 * --------------------------------------------
425 * | head | data | tail |
426 * --------------------------------------------
430 * So that the SILC header and 1 - 16 bytes of padding can fit to
431 * the buffer. After assembly the buffer might look like this:
433 * --------------------------------------------
435 * --------------------------------------------
437 * Start of assembled packet
439 * Packet construct is as follows (* = won't be encrypted):
441 * n bytes SILC Header
442 * 2 bytes Payload length (*)
445 * 2 bytes Source ID Length
446 * 2 bytes Destination ID Length
447 * 1 byte Source ID Type
449 * 1 byte Destination ID Type
450 * n bytes Destination ID
452 * 1 - 16 bytes Padding
454 * n bytes Data payload
456 * All fields in the packet will be authenticated by MAC. The MAC is
457 * not computed here, it must be computed separately before encrypting
461 void silc_packet_assemble(SilcPacketContext *ctx);
463 /****f* silccore/SilcPacketAPI/silc_packet_send_prepare
467 * void silc_packet_send_prepare(SilcSocketConnection sock,
474 * Prepare outgoing data buffer for packet sending. This moves the data
475 * area so that new packet may be added into it. If needed this allocates
476 * more space to the buffer. This handles directly the connection's
477 * outgoing buffer in SilcSocketConnection object.
480 void silc_packet_send_prepare(SilcSocketConnection sock,
485 /****f* silccore/SilcPacketAPI/silc_packet_receive
489 * int silc_packet_receive(SilcSocketConnection sock);
493 * Receives packet from network and reads the data into connection's
494 * incoming data buffer. If the data was read directly this returns the
495 * read bytes, if error occured this returns -1, if the data could not
496 * be read directly at this time this returns -2 in which case the data
497 * should be read again at some later time, or If EOF occured this returns
501 int silc_packet_receive(SilcSocketConnection sock);
503 /****f* silccore/SilcPacketAPI/silc_packet_decrypt
507 * int silc_packet_decrypt(SilcCipher cipher, SilcHmac hmac,
508 * SilcBuffer buffer, SilcPacketContext *packet,
509 * SilcPacketCheckDecrypt check_packet,
514 * Decrypts a packet. This assumes that typical SILC packet is the
515 * packet to be decrypted and thus checks for normal and special SILC
516 * packets and can handle both of them. This also computes and checks
517 * the HMAC of the packet. If any other special or customized decryption
518 * processing is required this function cannot be used. This returns
519 * -1 on error, 0 when packet is normal packet and 1 when the packet
520 * is special and requires special processing.
522 * The `check_packet' is a callback funtion that this function will
523 * call. The callback relates to the checking whether the packet is
524 * normal packet or special packet and how it should be processed. If
525 * the callback return TRUE the packet is normal and FALSE if the packet
526 * is special and requires special procesing.
529 int silc_packet_decrypt(SilcCipher cipher, SilcHmac hmac,
530 SilcBuffer buffer, SilcPacketContext *packet,
531 SilcPacketCheckDecrypt check_packet,
534 /****f* silccore/SilcPacketAPI/silc_packet_receive_process
538 * void silc_packet_receive_process(SilcSocketConnection sock,
539 * SilcCipher cipher, SilcHmac hmac,
540 * SilcPacketParserCallback parser,
545 * Processes the received data. This checks the received data and
546 * calls parser callback that handles the actual packet decryption
547 * and parsing. If more than one packet was received this calls the
548 * parser multiple times. The parser callback will get context
549 * SilcPacketParserContext that includes the packet and the `context'
550 * sent to this function.
553 void silc_packet_receive_process(SilcSocketConnection sock,
554 SilcCipher cipher, SilcHmac hmac,
555 SilcPacketParserCallback parser,
558 /****f* silccore/SilcPacketAPI/silc_packet_parse
562 * SilcPacketType silc_packet_parse(SilcPacketContext *ctx);
566 * Parses the packet. This is called when a whole packet is ready to be
567 * parsed. The buffer sent must be already decrypted before calling this
568 * function. The len argument must be the true length of the packet. This
569 * function returns the type of the packet. The data section of the
570 * buffer is parsed, not head or tail sections.
573 SilcPacketType silc_packet_parse(SilcPacketContext *ctx);
575 /****f* silccore/SilcPacketAPI/silc_packet_parse_special
579 * SilcPacketType silc_packet_parse_special(SilcPacketContext *ctx);
583 * Perform special SILC Packet header parsing. This is required to some
584 * packet types that have the data payload encrypted with different key
585 * than the header area plus padding of the packet. Hence, this parses
586 * the header in a way that it does not take the data area into account
587 * and parses the header and padding area only.
590 SilcPacketType silc_packet_parse_special(SilcPacketContext *ctx);
592 /****f* silccore/SilcPacketAPI/silc_packet_context_alloc
596 * SilcPacketContext *silc_packet_context_alloc();
600 * Allocates a packet context. Packet contexts are used when
601 * packets are assembled and parsed. The context is freed by the
602 * silc_packet_context_free function.
605 SilcPacketContext *silc_packet_context_alloc(void);
607 /****f* silccore/SilcPacketAPI/silc_packet_context_dup
611 * SilcPacketContext *silc_packet_context_dup(SilcPacketContext *ctx);
615 * Duplicates the packet context. It actually does not duplicate
616 * any data, instead a reference counter is increased.
619 SilcPacketContext *silc_packet_context_dup(SilcPacketContext *ctx);
621 /****f* silccore/SilcPacketAPI/silc_packet_context_free
625 * void silc_packet_context_free(SilcPacketContext *ctx);
629 * Frees the packet context. The context is actually freed when the
630 * reference counter hits zero.
633 void silc_packet_context_free(SilcPacketContext *ctx);