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 */
77 SILC_SKE_STATUS_TIMEOUT, /* Timeout */
81 #include "silcske_groups.h"
82 #include "silcske_payload.h"
84 /****d* silcske/SilcSKEAPI/SilcSKESecurityPropertyFlag
88 * typedef enum { ... } SilcSKESecurityPropertyFlag
92 * SKE security property flags as defined by the SK protocol.
97 SILC_SKE_SP_FLAG_NONE = 0x00, /* No flags */
98 SILC_SKE_SP_FLAG_IV_INCLUDED = 0x01, /* IV included in packet */
99 SILC_SKE_SP_FLAG_PFS = 0x02, /* Perfect Forward Secrecy */
100 SILC_SKE_SP_FLAG_MUTUAL = 0x04, /* Mutual authentication */
101 } SilcSKESecurityPropertyFlag;
104 /****s* silcske/SilcSKEAPI/SilcSKESecurityProperties
108 * typedef struct { ... } *SilcSKESecurityProperties;
112 * Security Properties negotiated between key exchange parties. This
113 * structure is filled from the Key Exchange Start Payload which is used
114 * to negotiate what security properties must be used in the
120 SilcSKESecurityPropertyFlag flags; /* Flags */
121 SilcSKEDiffieHellmanGroup group; /* Selected Diffie Hellman group */
122 SilcCipher cipher; /* Selected cipher */
123 SilcHmac hmac; /* Selected HMAC */
124 SilcHash hash; /* Selected hash algorithm */
125 SilcPublicKey public_key; /* Remote public key */
126 SilcUInt16 remote_port; /* Remote port, set when IV Included
127 set and using UDP/IP */
128 } *SilcSKESecurityProperties;
131 /****s* silcske/SilcSKEAPI/SilcSKEKeyMaterial
135 * typedef struct { ... } *SilcSKEKeyMaterial;
139 * This is the key material structure, and is passed as argument by the
140 * application to silc_ske_process_key_material_data function. It includes
141 * the processed key material which can be used as SILC session keys.
146 unsigned char *send_iv;
147 unsigned char *receive_iv;
149 unsigned char *send_enc_key;
150 unsigned char *receive_enc_key;
151 SilcUInt32 enc_key_len;
152 unsigned char *send_hmac_key;
153 unsigned char *receive_hmac_key;
154 SilcUInt32 hmac_key_len;
155 } *SilcSKEKeyMaterial;
158 /****s* silcske/SilcSKEAPI/SilcSKERekeyMaterial
162 * typedef struct { ... } *SilcSKERekeyMaterial;
166 * This context is returned after key exchange protocol to application
167 * in the completion callback. Application may save it and use it later
168 * to perform the rekey with silc_ske_rekey_initiator and/or
169 * silc_ske_rekey_responder functions. If application does not
170 * need the context, it may free it with silc_ske_free_rekey_material
175 unsigned char *send_enc_key;
177 unsigned int enc_key_len : 23;
178 unsigned int ske_group : 8;
179 unsigned int pfs : 1;
180 } *SilcSKERekeyMaterial;
182 /****s* silcske/SilcSKEAPI/SilcSKEParams
186 * typedef struct { ... } *SilcSKEParams, SilcSKEParamsStruct;
190 * SKE parameters structure. This structure is given as argument to
191 * silc_ske_initiator and silc_ske_responder functions.
196 /* The SKE version string that is sent to the remote end. This field
197 must be set. Caller must free the pointer. */
200 /* Security property flags. When initiator sets these it requests them
201 from the responder. Responder may set here the flags it supports
202 and wants to enforce for the initiator. */
203 SilcSKESecurityPropertyFlag flags;
205 /* SILC Session port when using UDP/IP and SILC_SKE_SP_FLAG_IV_INCLUDED
206 flag. It is the port the remote will use as SILC session port after
207 the key exchange protocol. Ignored without SILC_SKE_SP_FLAG_IV_INCLUDED
209 SilcUInt16 session_port;
210 } *SilcSKEParams, SilcSKEParamsStruct;
213 /****d* silcske/SilcSKEAPI/SilcSKEPKType
217 * typedef enum { ... } SilcSKEPKType;
221 * Public key and certificate types defined by the SKE protocol.
226 SILC_SKE_PK_TYPE_SILC = 1, /* SILC Public Key, mandatory */
227 SILC_SKE_PK_TYPE_SSH2 = 2, /* SSH2 Public key, not supported */
228 SILC_SKE_PK_TYPE_X509V3 = 3, /* X.509v3 certificate, not supported */
229 SILC_SKE_PK_TYPE_OPENPGP = 4, /* OpenPGP certificate, not supported */
230 SILC_SKE_PK_TYPE_SPKI = 5 /* SPKI certificate, not supported */
234 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCbCompletion
238 * typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
239 * SilcSKEStatus status,
244 * Completion callback that will be called when the public key
245 * has been verified. The `status' will indicate whether the public
246 * key were trusted or not.
249 typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
250 SilcSKEStatus status,
253 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCb
257 * typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
258 * SilcPublicKey public_key,
260 * SilcSKEVerifyCbCompletion completion,
261 * void *completion_context);
265 * Callback function used to verify the received public key or certificate.
266 * The verification process is most likely asynchronous. That's why the
267 * application must call the `completion' callback when the verification
268 * process has been completed. The `context' is the context given as
269 * arugment to silc_ske_set_callbacks. See silc_ske_set_callbacks for
272 * If the key repository was provided in silc_ske_alloc this callback
273 * is called only if the public key was not found from the repository.
276 typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
277 SilcPublicKey public_key,
279 SilcSKEVerifyCbCompletion completion,
280 void *completion_context);
282 /****f* silcske/SilcSKEAPI/SilcSKECompletionCb
286 * typedef void (*SilcSKECompletionCb)(SilcSKE ske,
287 * SilcSKEStatus status,
288 * const SilcSKESecurityProperties prop,
289 * const SilcSKEKeyMaterial keymat,
290 * SilcSKERekeyMaterial rekey,
295 * Completion callback. This is called after the key exchange protocol
296 * has been completed. It delivers the status of the protocol, and if
297 * successful the security properties `prop' that was negotiated in the
298 * protocol and the key material `keymat' that can be set into use by
299 * calling silc_ske_set_keys, and the rekey key material `rekey' which
300 * can be used later to start rekey protocol. The `prop' and `keymat'
301 * will remain valid as long as `ske' is valid. The `rekey' will remain
302 * valid until silc_ske_free_rekey_material is called. The application
303 * must call it to free the `rekey'.
305 * When doing rekey, this completion callback delivers the `keymat' and
306 * new `rekey'. The `prop' is ignored. The `keymat' has already been set
307 * to the packet stream associated with the `ske'. Thus, after this
308 * is called the new keys are in use.
311 typedef void (*SilcSKECompletionCb)(SilcSKE ske,
312 SilcSKEStatus status,
313 const SilcSKESecurityProperties prop,
314 const SilcSKEKeyMaterial keymat,
315 SilcSKERekeyMaterial rekey,
320 /****f* silcske/SilcSKEAPI/silc_ske_alloc
324 * SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
325 * SilcSKR repository, SilcPublicKey public_key,
326 * SilcPrivateKey private_key, void *context);
330 * Allocates the SKE session context and returns it. The `rng' is
331 * the random number generator the SKE is going to use when it needs
332 * random number generation during the SKE session. The `context' is
333 * user context that the libary will not touch. Application can get the
334 * context by calling the fuction silc_ske_get_context function. The
335 * application is responsible of freeing the `context'. After the
336 * SKE session context is allocated application must call the
337 * silc_ske_set_callbacks.
339 * If the `repository' is non-NULL then the remote's public key will be
340 * verified from the repository. If it is not provided then the
341 * SilcSKEVerifyCb callback must be set, and it will be called to
342 * verify the key. If both `repository' and the callback is provided the
343 * callback is called only if the key is not found from the repository.
345 * The `public_key' and `private_key' is the caller's identity used
346 * during the key exchange. Giving `private_key' is optional if the
347 * SILC_SKE_SP_FLAG_MUTUAL is not set and you are initiator. For
348 * responder both `public_key' and `private_key' must be set.
352 * // Initiator example
353 * params.version = version;
354 * params.flags = SILC_SKE_SP_FLAG_PFS | SILC_SKE_SP_FLAG_MUTUAL;
355 * ske = silc_ske_alloc(rng, scheduler, NULL, pk, prv, app);
356 * silc_ske_set_callbacks(ske, verify_public_key, completion, app);
357 * silc_ske_initiator_start(ske, stream, ¶ms, NULL);
360 SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
361 SilcSKR repository, SilcPublicKey public_key,
362 SilcPrivateKey private_key, void *context);
364 /****f* silcske/SilcSKEAPI/silc_ske_free
368 * void silc_ske_free(SilcSKE ske);
372 * Frees the SKE session context and all allocated resources.
375 void silc_ske_free(SilcSKE ske);
377 /****f* silcske/SilcSKEAPI/silc_ske_get_context
381 * void *silc_ske_get_context(SilcSKE ske);
385 * Returns the context that was given as argument to silc_ske_alloc.
388 void *silc_ske_get_context(SilcSKE ske);
390 /****f* silcske/SilcSKEAPI/silc_ske_set_callbacks
394 * void silc_ske_set_callbacks(SilcSKE ske,
395 * SilcSKEVerifyCb verify_key,
396 * SilcSKECompletion completed,
401 * Sets the callback functions for the SKE session.
403 * The `verify_key' callback is called to verify the received public key
404 * or certificate. The verification process is most likely asynchronous.
405 * That is why the application must call the completion callback when the
406 * verification process has been completed. If this SKE session context
407 * is used to perform rekey, this callback usually is not provided as
408 * argument since sending public key in rekey is not mandatory. Setting
409 * this callback implies that remote end MUST send its public key.
411 * The `completed' callback will be called once the protocol has completed,
412 * either successfully or with an error. The status of the protocol is
413 * delivered to application with the callback.
415 * The `context' is passed as argument to all of the above callback
419 void silc_ske_set_callbacks(SilcSKE ske,
420 SilcSKEVerifyCb verify_key,
421 SilcSKECompletionCb completed,
424 /****f* silcske/SilcSKEAPI/silc_ske_initiator_start
429 * silc_ske_initiator(SilcSKE ske,
430 * SilcPacketStream stream,
431 * SilcSKEParams params,
432 SilcSKEStartPayload start_payload);
436 * Starts the SILC Key Exchange protocol as initiator. The completion
437 * callback that was set in silc_ske_set_callbacks will be called once
438 * the protocol has completed. The `stream' is the network connection
439 * to the remote host. The SKE library will handle all key exchange
440 * packets sent and received in the `stream' connection. The library will
441 * also set the remote host's ID automatically to the `stream'. The
442 * `params' include SKE parameters, and it must be provided.
444 * If the `start_payload' is NULL the library will generate it
445 * automatically. Caller may provide it if it wants to send its own
446 * security properties instead of using the default ones library
447 * generates. If caller provides it, it must not free it once it has
448 * been given as argument to this function.
450 * This function returns SilcAsyncOperation operation context which can
451 * be used to control the protocol from the application. Application may
452 * for example safely abort the protocol at any point, if needed. Returns
457 silc_ske_initiator(SilcSKE ske,
458 SilcPacketStream stream,
459 SilcSKEParams params,
460 SilcSKEStartPayload start_payload);
462 /****f* silcske/SilcSKEAPI/silc_ske_responder
467 * silc_ske_responder(SilcSKE ske,
468 * SilcPacketStream stream,
469 * SilcSKEParams params);
473 * Starts SILC Key Exchange protocol as responder. The completion
474 * callback that was set in silc_ske_set_callbacks will be called once
475 * the protocol has completed. The `stream' is the network connection
476 * to the remote host. The SKE library will handle all key exchange
477 * packets sent and received in the `stream' connection. The `params'
478 * include SKE parameters, and must be provided.
480 * This function returns SilcAsyncOperation operation context which can
481 * be used to control the protocol from the application. Application may
482 * for example safely abort the protocol at any point, if needed. Returns
487 silc_ske_responder(SilcSKE ske,
488 SilcPacketStream stream,
489 SilcSKEParams params);
492 silc_ske_rekey_initiator(SilcSKE ske,
493 SilcPacketStream stream,
494 SilcSKERekeyMaterial rekey);
497 silc_ske_rekey_responder(SilcSKE ske,
498 SilcPacketStream stream,
499 SilcSKERekeyMaterial rekey);
501 /****f* silcske/SilcSKEAPI/silc_ske_set_keys
505 * SilcBool silc_ske_set_keys(SilcSKE ske,
506 * SilcSKEKeyMaterial keymat,
507 * SilcSKESecurityProperties prop,
508 * SilcCipher *ret_send_key,
509 * SilcCipher *ret_receive_key,
510 * SilcHmac *ret_hmac_send,
511 * SilcHmac *ret_hmac_receive,
512 * SilcHash *ret_hash);
516 * This function can be used after successful key exchange to take the
517 * key material `keymat' with security properties `prop' into use.
518 * This will allocate send and receive ciphers, HMACs and hash for the
519 * application. Caller must free the returned contexts. This is an
523 SilcBool silc_ske_set_keys(SilcSKE ske,
524 SilcSKEKeyMaterial keymat,
525 SilcSKESecurityProperties prop,
526 SilcCipher *ret_send_key,
527 SilcCipher *ret_receive_key,
528 SilcHmac *ret_hmac_send,
529 SilcHmac *ret_hmac_receive,
532 /****f* silcske/SilcSKEAPI/silc_ske_parse_version
536 * SilcBool silc_ske_parse_version(SilcSKE ske,
537 * SilcUInt32 *protocol_version,
538 * char **protocol_version_string,
539 * SilcUInt32 *software_version,
540 * char **software_version_string,
541 * char **vendor_version);
545 * Utility function to parse the remote host's version string. This can
546 * be called after the key exchange has been completed.
549 SilcBool silc_ske_parse_version(SilcSKE ske,
550 SilcUInt32 *protocol_version,
551 char **protocol_version_string,
552 SilcUInt32 *software_version,
553 char **software_version_string,
554 char **vendor_version);
556 /****f* silcske/SilcSKEAPI/silc_ske_get_security_properties
560 * SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
564 * Returns negotiated security properties from the `ske' or NULL if they
565 * have not yet been negotiated. This may be called to retrieve the
566 * security properties after the SilcSKECompletionCb has been called.
569 SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
571 /****f* silcske/SilcSKEAPI/silc_ske_get_key_material
575 * SilcSKEKeyMaterial silc_ske_get_key_material(SilcSKE ske);
579 * Returns the negotiated key material from the `ske' or NULL if the
580 * key material does not exist. The caller must not free the returned
584 SilcSKEKeyMaterial silc_ske_get_key_material(SilcSKE ske);
586 /****f* silcske/SilcSKEAPI/silc_ske_process_key_material_data
590 * const char *silc_ske_map_status(SilcSKEStatus status);
594 * Utility function to process key data `data' in the way specified
595 * by the SILC Key Exchange protocol. This returns the processed key
596 * material or NULL on error. Caller must free the returned key
597 * material context by calling silc_ske_free_key_material.
601 silc_ske_process_key_material_data(unsigned char *data,
603 SilcUInt32 req_iv_len,
604 SilcUInt32 req_enc_key_len,
605 SilcUInt32 req_hmac_key_len,
608 /****f* silcske/SilcSKEAPI/silc_ske_free_key_material
612 * void silc_ske_free_key_material(SilcSKEKeyMaterial key)
616 * Utility function to free the key material created by calling
617 * silc_ske_process_key_material_data.
620 void silc_ske_free_key_material(SilcSKEKeyMaterial key);
622 /****f* silcske/SilcSKEAPI/silc_ske_free_key_material
626 * void silc_ske_free_rekey_material(SilcSKERekeyMaterial rekey);
630 * Utility function to free the rekey material returned in the
631 * SilcSKECompletionCb callback.
634 void silc_ske_free_rekey_material(SilcSKERekeyMaterial rekey);
636 /****f* silcske/SilcSKEAPI/silc_ske_map_status
640 * const char *silc_ske_map_status(SilcSKEStatus status);
644 * Utility function to map the `status' into human readable message.
647 const char *silc_ske_map_status(SilcSKEStatus status);
649 #include "silcske_i.h"
651 #endif /* !SILCSKE_H */