5 Author: Pekka Riikonen <priikone@silcnet.org>
7 Copyright (C) 2000 - 2006 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; version 2 of the License.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
20 /****h* silcske/SILC SKE Interface
24 * The SILC Key Exchange (SKE) protocol interface. The SKE protocol
25 * is used to negotiate secret key material between two parties, to be used
26 * as session key or some other key. For example, when client connects to
27 * server SKE is performed to exchange public keys, and to generate the key
28 * that is then used as session key. Two clients can execute SKE as well
29 * two create secret key material for securing for example file transfer
30 * stream. This SKE implementation provides easy interface for application
31 * that wants to use SKE.
38 /* Forward declarations */
39 typedef struct SilcSKECallbacksStruct *SilcSKECallbacks;
40 typedef struct SilcSKEStruct *SilcSKE;
42 /****d* silcske/SilcSKEAPI/SilcSKEStatus
46 * typedef enum { ... } SilcSKEStatus;
50 * Status types returned in SKE callbacks. This tell the status of
51 * the SKE session, and if an error occurred. Application can map the
52 * status to human readable string with silc_ske_map_status function.
57 /* These are defined by the protocol */
58 SILC_SKE_STATUS_OK = 0, /* No error */
59 SILC_SKE_STATUS_ERROR = 1, /* Unknown error */
60 SILC_SKE_STATUS_BAD_PAYLOAD = 2, /* Malformed payload */
61 SILC_SKE_STATUS_UNKNOWN_GROUP = 3, /* Unsupported DH group */
62 SILC_SKE_STATUS_UNKNOWN_CIPHER = 4, /* Unsupported cipher */
63 SILC_SKE_STATUS_UNKNOWN_PKCS = 5, /* Unsupported PKCS algorithm */
64 SILC_SKE_STATUS_UNKNOWN_HASH_FUNCTION = 6, /* Unsupported hash function */
65 SILC_SKE_STATUS_UNKNOWN_HMAC = 7, /* Unsupported HMAC */
66 SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY = 8, /* Unsupported/not trusted PK */
67 SILC_SKE_STATUS_INCORRECT_SIGNATURE = 9, /* Incorrect signature */
68 SILC_SKE_STATUS_BAD_VERSION = 10, /* Unsupported version */
69 SILC_SKE_STATUS_INVALID_COOKIE = 11, /* Cookie was modified */
71 /* Implementation specific status types */
72 SILC_SKE_STATUS_PUBLIC_KEY_NOT_PROVIDED, /* Remote did not send PK */
73 SILC_SKE_STATUS_BAD_RESERVED_FIELD, /* Reserved field was not 0 */
74 SILC_SKE_STATUS_BAD_PAYLOAD_LENGTH, /* Payload includes garbage */
75 SILC_SKE_STATUS_SIGNATURE_ERROR, /* Error computing signature */
76 SILC_SKE_STATUS_OUT_OF_MEMORY, /* System out of memory */
80 #include "silcske_groups.h"
81 #include "silcske_payload.h"
83 /****d* silcske/SilcSKEAPI/SilcSKESecurityPropertyFlag
87 * typedef enum { ... } SilcSKESecurityPropertyFlag
91 * SKE security property flags as defined by the SK protocol.
96 SILC_SKE_SP_FLAG_NONE = 0x00, /* No flags */
97 SILC_SKE_SP_FLAG_IV_INCLUDED = 0x01, /* IV included in packet */
98 SILC_SKE_SP_FLAG_PFS = 0x02, /* Perfect Forward Secrecy */
99 SILC_SKE_SP_FLAG_MUTUAL = 0x04, /* Mutual authentication */
100 } SilcSKESecurityPropertyFlag;
103 /****s* silcske/SilcSKEAPI/SilcSKESecurityProperties
107 * typedef struct { ... } *SilcSKESecurityProperties;
111 * Security Properties negotiated between key exchange parties. This
112 * structure is filled from the Key Exchange Start Payload which is used
113 * to negotiate what security properties must be used in the
119 SilcSKESecurityPropertyFlag flags; /* Flags */
120 SilcSKEDiffieHellmanGroup group; /* Selected Diffie Hellman group */
121 SilcCipher cipher; /* Selected cipher */
122 SilcHmac hmac; /* Selected HMAC */
123 SilcHash hash; /* Selected hash algorithm */
124 SilcPublicKey public_key; /* Remote public key */
125 SilcUInt16 remote_port; /* Remote port, set when IV Included
126 set and using UDP/IP */
127 } *SilcSKESecurityProperties;
130 /****s* silcske/SilcSKEAPI/SilcSKEKeyMaterial
134 * typedef struct { ... } *SilcSKEKeyMaterial;
138 * This is the key material structure, and is passed as argument by the
139 * application to silc_ske_process_key_material_data function. It includes
140 * the processed key material which can be used as SILC session keys.
145 unsigned char *send_iv;
146 unsigned char *receive_iv;
148 unsigned char *send_enc_key;
149 unsigned char *receive_enc_key;
150 SilcUInt32 enc_key_len;
151 unsigned char *send_hmac_key;
152 unsigned char *receive_hmac_key;
153 SilcUInt32 hmac_key_len;
154 } *SilcSKEKeyMaterial;
157 /****s* silcske/SilcSKEAPI/SilcSKERekeyMaterial
161 * typedef struct { ... } *SilcSKERekeyMaterial;
165 * This context is returned after key exchange protocol to application
166 * in the completion callback. Application may save it and use it later
167 * to perform the rekey with silc_ske_rekey_initiator_start and/or
168 * silc_ske_rekey_responder_start functions. If application does not
169 * need the context, it may free it with silc_free function.
171 * Application may save application specific data to `user_context'.
176 void *user_context; /* Application specific data */
177 unsigned char *send_enc_key;
178 unsigned int enc_key_len : 23;
179 unsigned int ske_group : 8;
180 unsigned int pfs : 1;
181 } *SilcSKERekeyMaterial;
184 /****s* silcske/SilcSKEAPI/SilcSKEParams
188 * typedef struct { ... } *SilcSKEParams, SilcSKEParamsStruct;
192 * SKE parameters structure. This structure is given as argument to
193 * silc_ske_initiator and silc_ske_responder functions.
198 /* The SKE version string that is sent to the remote end. This field
199 must be set. Caller must free the pointer. */
202 /* Security property flags. When initiator sets these it requests them
203 from the responder. Responder may set here the flags it supports
204 and wants to enforce for the initiator. */
205 SilcSKESecurityPropertyFlag flags;
207 /* SILC Session port when using UDP/IP and SILC_SKE_SP_FLAG_IV_INCLUDED
208 flag. It is the port the remote will use as SILC session port after
209 the key exchange protocol. Ignored without SILC_SKE_SP_FLAG_IV_INCLUDED
211 SilcUInt16 session_port;
212 } *SilcSKEParams, SilcSKEParamsStruct;
215 /****d* silcske/SilcSKEAPI/SilcSKEPKType
219 * typedef enum { ... } SilcSKEPKType;
223 * Public key and certificate types defined by the SKE protocol.
228 SILC_SKE_PK_TYPE_SILC = 1, /* SILC Public Key, mandatory */
229 SILC_SKE_PK_TYPE_SSH2 = 2, /* SSH2 Public key, not supported */
230 SILC_SKE_PK_TYPE_X509V3 = 3, /* X.509v3 certificate, not supported */
231 SILC_SKE_PK_TYPE_OPENPGP = 4, /* OpenPGP certificate, not supported */
232 SILC_SKE_PK_TYPE_SPKI = 5 /* SPKI certificate, not supported */
236 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCbCompletion
240 * typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
241 * SilcSKEStatus status,
246 * Completion callback that will be called when the public key
247 * has been verified. The `status' will indicate whether the public
248 * key were trusted or not.
251 typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
252 SilcSKEStatus status,
255 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCb
259 * typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
260 * SilcPublicKey public_key,
262 * SilcSKEVerifyCbCompletion completion,
263 * void *completion_context);
267 * Callback function used to verify the received public key or certificate.
268 * The verification process is most likely asynchronous. That's why the
269 * application must call the `completion' callback when the verification
270 * process has been completed. The `context' is the context given as
271 * arugment to silc_ske_set_callbacks. See silc_ske_set_callbacks for
274 * If the key repository was provided in silc_ske_alloc this callback
275 * is called only if the public key was not found from the repository.
278 typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
279 SilcPublicKey public_key,
281 SilcSKEVerifyCbCompletion completion,
282 void *completion_context);
284 /****f* silcske/SilcSKEAPI/SilcSKECompletionCb
288 * typedef void (*SilcSKECompletionCb)(SilcSKE ske,
289 * SilcSKEStatus status,
290 * SilcSKESecurityProperties prop,
291 * SilcSKEKeyMaterial keymat,
292 * SilcSKERekeyMaterial rekey,
297 * Completion callback. This is called after the key exchange protocol
298 * has been completed. It delivers the status of the protocol, and if
299 * successful the security properties `prop' that was negotiated in the
300 * protocol and the key material `keymat' that can be set into use by
301 * calling silc_ske_set_keys, and the rekey key material `rekey' which
302 * can be used later to start rekey protocol. The `prop' will remain
303 * valid as long as `ske' is valid. After `ske' is freed `prop' will
307 typedef void (*SilcSKECompletionCb)(SilcSKE ske,
308 SilcSKEStatus status,
309 SilcSKESecurityProperties prop,
310 SilcSKEKeyMaterial keymat,
311 SilcSKERekeyMaterial rekey,
316 /****f* silcske/SilcSKEAPI/silc_ske_alloc
320 * SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
321 * SilcSKR repository, SilcPublicKey public_key,
322 * SilcPrivateKey private_key, void *context);
326 * Allocates the SKE session context and returns it. The `rng' is
327 * the random number generator the SKE is going to use when it needs
328 * random number generation during the SKE session. The `context' is
329 * user context that the libary will not touch. Application can get the
330 * context by calling the fuction silc_ske_get_context function. The
331 * application is responsible of freeing the `context'. After the
332 * SKE session context is allocated application must call the
333 * silc_ske_set_callbacks.
335 * If the `repository' is non-NULL then the remote's public key will be
336 * verified from the repository. If it is not provided then the
337 * SilcSKEVerifyCb callback must be set, and it will be called to
338 * verify the key. If both `repository' and the callback is provided the
339 * callback is called only if the key is not found from the repository.
341 * The `public_key' and `private_key' is the caller's identity used
342 * during the key exchange. Giving `private_key' is optional if the
343 * SILC_SKE_SP_FLAG_MUTUAL is not set and you are initiator. For
344 * responder both `public_key' and `private_key' must be set.
348 * // Initiator example
349 * params.version = version;
350 * params.flags = SILC_SKE_SP_FLAG_PFS | SILC_SKE_SP_FLAG_MUTUAL;
351 * ske = silc_ske_alloc(rng, scheduler, NULL, pk, prv, app);
352 * silc_ske_set_callbacks(ske, verify_public_key, completion, app);
353 * silc_ske_initiator_start(ske, stream, ¶ms, NULL);
356 SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
357 SilcSKR repository, SilcPublicKey public_key,
358 SilcPrivateKey private_key, void *context);
360 /****f* silcske/SilcSKEAPI/silc_ske_free
364 * void silc_ske_free(SilcSKE ske);
368 * Frees the SKE session context and all allocated resources.
371 void silc_ske_free(SilcSKE ske);
373 /****f* silcske/SilcSKEAPI/silc_ske_get_context
377 * void *silc_ske_get_context(SilcSKE ske);
381 * Returns the context that was given as argument to silc_ske_alloc.
384 void *silc_ske_get_context(SilcSKE ske);
386 /****f* silcske/SilcSKEAPI/silc_ske_set_callbacks
390 * void silc_ske_set_callbacks(SilcSKE ske,
391 * SilcSKEVerifyCb verify_key,
392 * SilcSKECompletion completed,
397 * Sets the callback functions for the SKE session.
399 * The `verify_key' callback is called to verify the received public key
400 * or certificate. The verification process is most likely asynchronous.
401 * That is why the application must call the completion callback when the
402 * verification process has been completed. If this SKE session context
403 * is used to perform rekey, this callback usually is not provided as
404 * argument since sending public key in rekey is not mandatory. Setting
405 * this callback implies that remote end MUST send its public key.
407 * The `completed' callback will be called once the protocol has completed,
408 * either successfully or with an error. The status of the protocol is
409 * delivered to application with the callback.
411 * The `context' is passed as argument to all of the above callback
415 void silc_ske_set_callbacks(SilcSKE ske,
416 SilcSKEVerifyCb verify_key,
417 SilcSKECompletionCb completed,
420 /****f* silcske/SilcSKEAPI/silc_ske_initiator_start
425 * silc_ske_initiator(SilcSKE ske,
426 * SilcPacketStream stream,
427 * SilcSKEParams params,
428 SilcSKEStartPayload start_payload);
432 * Starts the SILC Key Exchange protocol as initiator. The completion
433 * callback that was set in silc_ske_set_callbacks will be called once
434 * the protocol has completed. The `stream' is the network connection
435 * to the remote host. The SKE library will handle all key exchange
436 * packets sent and received in the `stream' connection. The library will
437 * also set the remote host's ID automatically to the `stream'. The
438 * `params' include SKE parameters, and it must be provided.
440 * If the `start_payload' is NULL the library will generate it
441 * automatically. Caller may provide it if it wants to send its own
442 * security properties instead of using the default ones library
443 * generates. If caller provides it, it must not free it once it has
444 * been given as argument to this function.
446 * This function returns SilcAsyncOperation operation context which can
447 * be used to control the protocol from the application. Application may
448 * for example safely abort the protocol at any point, if needed. Returns
453 silc_ske_initiator(SilcSKE ske,
454 SilcPacketStream stream,
455 SilcSKEParams params,
456 SilcSKEStartPayload start_payload);
458 /****f* silcske/SilcSKEAPI/silc_ske_responder_start
463 * silc_ske_responder(SilcSKE ske,
464 * SilcPacketStream stream,
465 * SilcSKEParams params);
469 * Starts SILC Key Exchange protocol as responder. The completion
470 * callback that was set in silc_ske_set_callbacks will be called once
471 * the protocol has completed. The `stream' is the network connection
472 * to the remote host. The SKE library will handle all key exchange
473 * packets sent and received in the `stream' connection. The `params'
474 * include SKE parameters, and must be provided.
476 * This function returns SilcAsyncOperation operation context which can
477 * be used to control the protocol from the application. Application may
478 * for example safely abort the protocol at any point, if needed. Returns
483 silc_ske_responder(SilcSKE ske,
484 SilcPacketStream stream,
485 SilcSKEParams params);
488 silc_ske_rekey_initiator(SilcSKE ske,
489 SilcPacketStream stream,
490 SilcSKERekeyMaterial rekey);
493 silc_ske_rekey_responder(SilcSKE ske,
494 SilcPacketStream stream,
495 SilcBuffer ke_payload,
496 SilcSKERekeyMaterial rekey);
498 /****f* silcske/SilcSKEAPI/silc_ske_set_keys
502 * SilcBool silc_ske_set_keys(SilcSKE ske,
503 * SilcSKEKeyMaterial keymat,
504 * SilcSKESecurityProperties prop,
505 * SilcCipher *ret_send_key,
506 * SilcCipher *ret_receive_key,
507 * SilcHmac *ret_hmac_send,
508 * SilcHmac *ret_hmac_receive,
509 * SilcHash *ret_hash);
513 * This function can be used after successful key exchange to take the
514 * key material `keymat' with security properties `prop' into use.
515 * This will allocate send and receive ciphers, HMACs and hash for the
516 * application. Caller must free the returned contexts. This is an
520 SilcBool silc_ske_set_keys(SilcSKE ske,
521 SilcSKEKeyMaterial keymat,
522 SilcSKESecurityProperties prop,
523 SilcCipher *ret_send_key,
524 SilcCipher *ret_receive_key,
525 SilcHmac *ret_hmac_send,
526 SilcHmac *ret_hmac_receive,
529 /****f* silcske/SilcSKEAPI/silc_ske_parse_version
533 * SilcBool silc_ske_parse_version(SilcSKE ske,
534 * SilcUInt32 *protocol_version,
535 * char **protocol_version_string,
536 * SilcUInt32 *software_version,
537 * char **software_version_string,
538 * char **vendor_version);
542 * Utility function to parse the remote host's version string. This can
543 * be called after the key exchange has been completed.
546 SilcBool silc_ske_parse_version(SilcSKE ske,
547 SilcUInt32 *protocol_version,
548 char **protocol_version_string,
549 SilcUInt32 *software_version,
550 char **software_version_string,
551 char **vendor_version);
553 /****f* silcske/SilcSKEAPI/silc_ske_get_security_properties
557 * SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
561 * Returns negotiated security properties from the `ske' or NULL if they
562 * have not yet been negotiated. This may be called to retrieve the
563 * security properties after the SilcSKECompletionCb has been called.
566 SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
568 /****f* silcske/SilcSKEAPI/silc_ske_process_key_material_data
572 * const char *silc_ske_map_status(SilcSKEStatus status);
576 * Utility function to process key data `data' in the way specified
577 * by the SILC Key Exchange protocol. This returns the processed key
578 * material or NULL on error. Caller must free the returned key
579 * material context by calling silc_ske_free_key_material.
583 silc_ske_process_key_material_data(unsigned char *data,
585 SilcUInt32 req_iv_len,
586 SilcUInt32 req_enc_key_len,
587 SilcUInt32 req_hmac_key_len,
590 /****f* silcske/SilcSKEAPI/silc_ske_free_key_material
594 * void silc_ske_free_key_material(SilcSKEKeyMaterial key)
598 * Utility function to free the key material created by calling
599 * silc_ske_process_key_material_data.
602 void silc_ske_free_key_material(SilcSKEKeyMaterial key);
604 /****f* silcske/SilcSKEAPI/silc_ske_map_status
608 * const char *silc_ske_map_status(SilcSKEStatus status);
612 * Utility function to map the `status' into human readable message.
615 const char *silc_ske_map_status(SilcSKEStatus status);
617 #include "silcske_i.h"
619 #endif /* !SILCSKE_H */