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_start and/or
169 * silc_ske_rekey_responder functions. If application does not
170 * need the context, it may free it with silc_free function.
172 * Application may save application specific data to `user_context'.
177 void *user_context; /* Application specific data */
178 unsigned char *send_enc_key;
179 unsigned int enc_key_len : 23;
180 unsigned int ske_group : 8;
181 unsigned int pfs : 1;
182 } *SilcSKERekeyMaterial;
185 /****s* silcske/SilcSKEAPI/SilcSKEParams
189 * typedef struct { ... } *SilcSKEParams, SilcSKEParamsStruct;
193 * SKE parameters structure. This structure is given as argument to
194 * silc_ske_initiator and silc_ske_responder functions.
199 /* The SKE version string that is sent to the remote end. This field
200 must be set. Caller must free the pointer. */
203 /* Security property flags. When initiator sets these it requests them
204 from the responder. Responder may set here the flags it supports
205 and wants to enforce for the initiator. */
206 SilcSKESecurityPropertyFlag flags;
208 /* SILC Session port when using UDP/IP and SILC_SKE_SP_FLAG_IV_INCLUDED
209 flag. It is the port the remote will use as SILC session port after
210 the key exchange protocol. Ignored without SILC_SKE_SP_FLAG_IV_INCLUDED
212 SilcUInt16 session_port;
213 } *SilcSKEParams, SilcSKEParamsStruct;
216 /****d* silcske/SilcSKEAPI/SilcSKEPKType
220 * typedef enum { ... } SilcSKEPKType;
224 * Public key and certificate types defined by the SKE protocol.
229 SILC_SKE_PK_TYPE_SILC = 1, /* SILC Public Key, mandatory */
230 SILC_SKE_PK_TYPE_SSH2 = 2, /* SSH2 Public key, not supported */
231 SILC_SKE_PK_TYPE_X509V3 = 3, /* X.509v3 certificate, not supported */
232 SILC_SKE_PK_TYPE_OPENPGP = 4, /* OpenPGP certificate, not supported */
233 SILC_SKE_PK_TYPE_SPKI = 5 /* SPKI certificate, not supported */
237 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCbCompletion
241 * typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
242 * SilcSKEStatus status,
247 * Completion callback that will be called when the public key
248 * has been verified. The `status' will indicate whether the public
249 * key were trusted or not.
252 typedef void (*SilcSKEVerifyCbCompletion)(SilcSKE ske,
253 SilcSKEStatus status,
256 /****f* silcske/SilcSKEAPI/SilcSKEVerifyCb
260 * typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
261 * SilcPublicKey public_key,
263 * SilcSKEVerifyCbCompletion completion,
264 * void *completion_context);
268 * Callback function used to verify the received public key or certificate.
269 * The verification process is most likely asynchronous. That's why the
270 * application must call the `completion' callback when the verification
271 * process has been completed. The `context' is the context given as
272 * arugment to silc_ske_set_callbacks. See silc_ske_set_callbacks for
275 * If the key repository was provided in silc_ske_alloc this callback
276 * is called only if the public key was not found from the repository.
279 typedef void (*SilcSKEVerifyCb)(SilcSKE ske,
280 SilcPublicKey public_key,
282 SilcSKEVerifyCbCompletion completion,
283 void *completion_context);
285 /****f* silcske/SilcSKEAPI/SilcSKECompletionCb
289 * typedef void (*SilcSKECompletionCb)(SilcSKE ske,
290 * SilcSKEStatus status,
291 * SilcSKESecurityProperties prop,
292 * SilcSKEKeyMaterial keymat,
293 * SilcSKERekeyMaterial rekey,
298 * Completion callback. This is called after the key exchange protocol
299 * has been completed. It delivers the status of the protocol, and if
300 * successful the security properties `prop' that was negotiated in the
301 * protocol and the key material `keymat' that can be set into use by
302 * calling silc_ske_set_keys, and the rekey key material `rekey' which
303 * can be used later to start rekey protocol. The `prop' will remain
304 * valid as long as `ske' is valid. After `ske' is freed `prop' will
308 typedef void (*SilcSKECompletionCb)(SilcSKE ske,
309 SilcSKEStatus status,
310 SilcSKESecurityProperties prop,
311 SilcSKEKeyMaterial keymat,
312 SilcSKERekeyMaterial rekey,
317 /****f* silcske/SilcSKEAPI/silc_ske_alloc
321 * SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
322 * SilcSKR repository, SilcPublicKey public_key,
323 * SilcPrivateKey private_key, void *context);
327 * Allocates the SKE session context and returns it. The `rng' is
328 * the random number generator the SKE is going to use when it needs
329 * random number generation during the SKE session. The `context' is
330 * user context that the libary will not touch. Application can get the
331 * context by calling the fuction silc_ske_get_context function. The
332 * application is responsible of freeing the `context'. After the
333 * SKE session context is allocated application must call the
334 * silc_ske_set_callbacks.
336 * If the `repository' is non-NULL then the remote's public key will be
337 * verified from the repository. If it is not provided then the
338 * SilcSKEVerifyCb callback must be set, and it will be called to
339 * verify the key. If both `repository' and the callback is provided the
340 * callback is called only if the key is not found from the repository.
342 * The `public_key' and `private_key' is the caller's identity used
343 * during the key exchange. Giving `private_key' is optional if the
344 * SILC_SKE_SP_FLAG_MUTUAL is not set and you are initiator. For
345 * responder both `public_key' and `private_key' must be set.
349 * // Initiator example
350 * params.version = version;
351 * params.flags = SILC_SKE_SP_FLAG_PFS | SILC_SKE_SP_FLAG_MUTUAL;
352 * ske = silc_ske_alloc(rng, scheduler, NULL, pk, prv, app);
353 * silc_ske_set_callbacks(ske, verify_public_key, completion, app);
354 * silc_ske_initiator_start(ske, stream, ¶ms, NULL);
357 SilcSKE silc_ske_alloc(SilcRng rng, SilcSchedule schedule,
358 SilcSKR repository, SilcPublicKey public_key,
359 SilcPrivateKey private_key, void *context);
361 /****f* silcske/SilcSKEAPI/silc_ske_free
365 * void silc_ske_free(SilcSKE ske);
369 * Frees the SKE session context and all allocated resources.
372 void silc_ske_free(SilcSKE ske);
374 /****f* silcske/SilcSKEAPI/silc_ske_get_context
378 * void *silc_ske_get_context(SilcSKE ske);
382 * Returns the context that was given as argument to silc_ske_alloc.
385 void *silc_ske_get_context(SilcSKE ske);
387 /****f* silcske/SilcSKEAPI/silc_ske_set_callbacks
391 * void silc_ske_set_callbacks(SilcSKE ske,
392 * SilcSKEVerifyCb verify_key,
393 * SilcSKECompletion completed,
398 * Sets the callback functions for the SKE session.
400 * The `verify_key' callback is called to verify the received public key
401 * or certificate. The verification process is most likely asynchronous.
402 * That is why the application must call the completion callback when the
403 * verification process has been completed. If this SKE session context
404 * is used to perform rekey, this callback usually is not provided as
405 * argument since sending public key in rekey is not mandatory. Setting
406 * this callback implies that remote end MUST send its public key.
408 * The `completed' callback will be called once the protocol has completed,
409 * either successfully or with an error. The status of the protocol is
410 * delivered to application with the callback.
412 * The `context' is passed as argument to all of the above callback
416 void silc_ske_set_callbacks(SilcSKE ske,
417 SilcSKEVerifyCb verify_key,
418 SilcSKECompletionCb completed,
421 /****f* silcske/SilcSKEAPI/silc_ske_initiator_start
426 * silc_ske_initiator(SilcSKE ske,
427 * SilcPacketStream stream,
428 * SilcSKEParams params,
429 SilcSKEStartPayload start_payload);
433 * Starts the SILC Key Exchange protocol as initiator. The completion
434 * callback that was set in silc_ske_set_callbacks will be called once
435 * the protocol has completed. The `stream' is the network connection
436 * to the remote host. The SKE library will handle all key exchange
437 * packets sent and received in the `stream' connection. The library will
438 * also set the remote host's ID automatically to the `stream'. The
439 * `params' include SKE parameters, and it must be provided.
441 * If the `start_payload' is NULL the library will generate it
442 * automatically. Caller may provide it if it wants to send its own
443 * security properties instead of using the default ones library
444 * generates. If caller provides it, it must not free it once it has
445 * been given as argument to this function.
447 * This function returns SilcAsyncOperation operation context which can
448 * be used to control the protocol from the application. Application may
449 * for example safely abort the protocol at any point, if needed. Returns
454 silc_ske_initiator(SilcSKE ske,
455 SilcPacketStream stream,
456 SilcSKEParams params,
457 SilcSKEStartPayload start_payload);
459 /****f* silcske/SilcSKEAPI/silc_ske_responder
464 * silc_ske_responder(SilcSKE ske,
465 * SilcPacketStream stream,
466 * SilcSKEParams params);
470 * Starts SILC Key Exchange protocol as responder. The completion
471 * callback that was set in silc_ske_set_callbacks will be called once
472 * the protocol has completed. The `stream' is the network connection
473 * to the remote host. The SKE library will handle all key exchange
474 * packets sent and received in the `stream' connection. The `params'
475 * include SKE parameters, and must be provided.
477 * This function returns SilcAsyncOperation operation context which can
478 * be used to control the protocol from the application. Application may
479 * for example safely abort the protocol at any point, if needed. Returns
484 silc_ske_responder(SilcSKE ske,
485 SilcPacketStream stream,
486 SilcSKEParams params);
489 silc_ske_rekey_initiator(SilcSKE ske,
490 SilcPacketStream stream,
491 SilcSKERekeyMaterial rekey);
494 silc_ske_rekey_responder(SilcSKE ske,
495 SilcPacketStream stream,
496 SilcBuffer ke_payload,
497 SilcSKERekeyMaterial rekey);
499 /****f* silcske/SilcSKEAPI/silc_ske_set_keys
503 * SilcBool silc_ske_set_keys(SilcSKE ske,
504 * SilcSKEKeyMaterial keymat,
505 * SilcSKESecurityProperties prop,
506 * SilcCipher *ret_send_key,
507 * SilcCipher *ret_receive_key,
508 * SilcHmac *ret_hmac_send,
509 * SilcHmac *ret_hmac_receive,
510 * SilcHash *ret_hash);
514 * This function can be used after successful key exchange to take the
515 * key material `keymat' with security properties `prop' into use.
516 * This will allocate send and receive ciphers, HMACs and hash for the
517 * application. Caller must free the returned contexts. This is an
521 SilcBool silc_ske_set_keys(SilcSKE ske,
522 SilcSKEKeyMaterial keymat,
523 SilcSKESecurityProperties prop,
524 SilcCipher *ret_send_key,
525 SilcCipher *ret_receive_key,
526 SilcHmac *ret_hmac_send,
527 SilcHmac *ret_hmac_receive,
530 /****f* silcske/SilcSKEAPI/silc_ske_parse_version
534 * SilcBool silc_ske_parse_version(SilcSKE ske,
535 * SilcUInt32 *protocol_version,
536 * char **protocol_version_string,
537 * SilcUInt32 *software_version,
538 * char **software_version_string,
539 * char **vendor_version);
543 * Utility function to parse the remote host's version string. This can
544 * be called after the key exchange has been completed.
547 SilcBool silc_ske_parse_version(SilcSKE ske,
548 SilcUInt32 *protocol_version,
549 char **protocol_version_string,
550 SilcUInt32 *software_version,
551 char **software_version_string,
552 char **vendor_version);
554 /****f* silcske/SilcSKEAPI/silc_ske_get_security_properties
558 * SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
562 * Returns negotiated security properties from the `ske' or NULL if they
563 * have not yet been negotiated. This may be called to retrieve the
564 * security properties after the SilcSKECompletionCb has been called.
567 SilcSKESecurityProperties silc_ske_get_security_properties(SilcSKE ske);
569 /****f* silcske/SilcSKEAPI/silc_ske_get_key_material
573 * SilcSKEKeyMaterial silc_ske_get_key_material(SilcSKE ske);
577 * Returns the negotiated key material from the `ske' or NULL if the
578 * key material does not exist. The caller must not free the returned
582 SilcSKEKeyMaterial silc_ske_get_key_material(SilcSKE ske);
584 /****f* silcske/SilcSKEAPI/silc_ske_process_key_material_data
588 * const char *silc_ske_map_status(SilcSKEStatus status);
592 * Utility function to process key data `data' in the way specified
593 * by the SILC Key Exchange protocol. This returns the processed key
594 * material or NULL on error. Caller must free the returned key
595 * material context by calling silc_ske_free_key_material.
599 silc_ske_process_key_material_data(unsigned char *data,
601 SilcUInt32 req_iv_len,
602 SilcUInt32 req_enc_key_len,
603 SilcUInt32 req_hmac_key_len,
606 /****f* silcske/SilcSKEAPI/silc_ske_free_key_material
610 * void silc_ske_free_key_material(SilcSKEKeyMaterial key)
614 * Utility function to free the key material created by calling
615 * silc_ske_process_key_material_data.
618 void silc_ske_free_key_material(SilcSKEKeyMaterial key);
620 /****f* silcske/SilcSKEAPI/silc_ske_map_status
624 * const char *silc_ske_map_status(SilcSKEStatus status);
628 * Utility function to map the `status' into human readable message.
631 const char *silc_ske_map_status(SilcSKEStatus status);
633 #include "silcske_i.h"
635 #endif /* !SILCSKE_H */