Merged from silc_1_0_branch.
[silc.git] / lib / silcske / silcske.c
index e95c57e225761a7ef090da41d409a36f1fd241fd..2fd4e0107ea646bea7f2fe87dabc7d29830a80a6 100644 (file)
@@ -1,16 +1,15 @@
 /*
 
-  silcske.c
+  silcske.c 
 
-  Author: Pekka Riikonen <priikone@poseidon.pspt.fi>
+  Author: Pekka Riikonen <priikone@silcnet.org>
 
-  Copyright (C) 2000 - 2001 Pekka Riikonen
+  Copyright (C) 2000 - 2002 Pekka Riikonen
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
-  (at your option) any later version.
-  
+  the Free Software Foundation; version 2 of the License.
+
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 /* $Id$ */
 
 #include "silcincludes.h"
-#include "payload_internal.h"
+#include "silcske.h"
 #include "groups_internal.h"
 
+/* Static functions */
+static SilcSKEStatus silc_ske_create_rnd(SilcSKE ske, SilcMPInt *n, 
+                                        SilcUInt32 len, 
+                                        SilcMPInt *rnd);
+static SilcSKEStatus silc_ske_make_hash(SilcSKE ske, 
+                                       unsigned char *return_hash,
+                                       SilcUInt32 *return_hash_len,
+                                       int initiator);
+
+/* Structure to hold all SKE callbacks. */
+struct SilcSKECallbacksStruct {
+  SilcSKESendPacketCb send_packet;
+  SilcSKECb payload_receive;
+  SilcSKEVerifyCb verify_key;
+  SilcSKECb proto_continue;
+  SilcSKECheckVersion check_version;
+  void *context;
+};
+
 /* Allocates new SKE object. */
 
-SilcSKE silc_ske_alloc()
+SilcSKE silc_ske_alloc(SilcRng rng, void *context)
 {
   SilcSKE ske;
 
   SILC_LOG_DEBUG(("Allocating new Key Exchange object"));
 
   ske = silc_calloc(1, sizeof(*ske));
+  if (!ske)
+    return NULL;
   ske->status = SILC_SKE_STATUS_OK;
+  ske->rng = rng;
+  ske->user_data = context;
+  ske->users = 1;
 
   return ske;
 }
@@ -41,6 +64,13 @@ SilcSKE silc_ske_alloc()
 
 void silc_ske_free(SilcSKE ske)
 {
+  ske->users--;
+  if (ske->users > 0) {
+    SILC_LOG_DEBUG(("Key Exchange set to FREED status"));
+    ske->status = SILC_SKE_STATUS_FREED;
+    return;
+  }
+
   SILC_LOG_DEBUG(("Freeing Key Exchange object"));
 
   if (ske) {
@@ -51,11 +81,14 @@ void silc_ske_free(SilcSKE ske)
     /* Free KE payload */
     if (ske->ke1_payload)
       silc_ske_payload_ke_free(ske->ke1_payload);
+    if (ske->ke2_payload)
+      silc_ske_payload_ke_free(ske->ke2_payload);
+    silc_free(ske->remote_version);
 
     /* Free rest */
     if (ske->prop) {
       if (ske->prop->group)
-       silc_free(ske->prop->group);
+       silc_ske_group_free(ske->prop->group);
       if (ske->prop->pkcs)
        silc_pkcs_free(ske->prop->pkcs);
       if (ske->prop->cipher)
@@ -68,39 +101,92 @@ void silc_ske_free(SilcSKE ske)
     }
     if (ske->start_payload_copy)
       silc_buffer_free(ske->start_payload_copy);
-    if (ske->pk)
-      silc_free(ske->pk);
     if (ske->x) {
-      silc_mp_clear(ske->x);
+      silc_mp_uninit(ske->x);
       silc_free(ske->x);
     }
     if (ske->KEY) {
-      silc_mp_clear(ske->KEY);
+      silc_mp_uninit(ske->KEY);
       silc_free(ske->KEY);
     }
-    if (ske->hash)
-      silc_free(ske->hash);
+    silc_free(ske->hash);
+    silc_free(ske->callbacks);
+
+    memset(ske, 'F', sizeof(*ske));
     silc_free(ske);
   }
 }
 
+/* Sets the callback functions for the SKE session. 
+
+   The `send_packet' callback is a function that sends the packet to
+   network. The SKE library will call it at any time packet needs to
+   be sent to the remote host. 
+
+   The `payload_receive' callback is called when the remote host's Key
+   Exchange Start Payload has been processed.  The payload is saved
+   to ske->start_payload if the application would need it.  The application
+   must also provide the payload to the next state of the SKE.
+
+   The `verify_key' callback is called to verify the received public key
+   or certificate.  The verification process is most likely asynchronous.
+   That is why the application must call the completion callback when the
+   verification process has been completed. The library then calls the user
+   callback (`proto_continue'), if it is provided to indicate that the SKE
+   protocol may continue. 
+   
+   The `proto_continue' callback is called to indicate that it is
+   safe to continue the execution of the SKE protocol after executing
+   an asynchronous operation, such as calling the `verify_key' callback
+   function, which is asynchronous. The application should check the
+   ske->status in this function to check whether it is Ok to continue
+   the execution of the protocol.
+
+   The `check_version' callback is called to verify the remote host's
+   version. The application may check its own version against the remote
+   host's version and determine whether supporting the remote host
+   is possible. 
+
+   The `context' is passed as argument to all of the above callback
+   functions. */
+
+void silc_ske_set_callbacks(SilcSKE ske,
+                           SilcSKESendPacketCb send_packet,
+                           SilcSKECb payload_receive,
+                           SilcSKEVerifyCb verify_key,
+                           SilcSKECb proto_continue,
+                           SilcSKECheckVersion check_version,
+                           void *context)
+{
+  if (ske->callbacks)
+    silc_free(ske->callbacks);
+  ske->callbacks = silc_calloc(1, sizeof(*ske->callbacks));
+  if (!ske->callbacks)
+    return;
+  ske->callbacks->send_packet = send_packet;
+  ske->callbacks->payload_receive = payload_receive;
+  ske->callbacks->verify_key = verify_key;
+  ske->callbacks->proto_continue = proto_continue;
+  ske->callbacks->check_version = check_version;
+  ske->callbacks->context = context;
+}
+
 /* Starts the SILC Key Exchange protocol for initiator. The connection
    to the remote end must be established before calling this function
    and the connecting socket must be sent as argument. This function
-   creates the Key Exchange Start Paload which includes all our
+   creates the Key Exchange Start Payload which includes all our
    configured security properties. This payload is then sent to the
    remote end for further processing. This payload must be sent as
    argument to the function, however, it must not be encoded
-   already, it is done by this function.
+   already, it is done by this function. The caller must not free
+   the `start_payload' since the SKE library will save it.
 
    The packet sending is done by calling a callback function. Caller
    must provide a routine to send the packet. */
 
 SilcSKEStatus silc_ske_initiator_start(SilcSKE ske, SilcRng rng,
                                       SilcSocketConnection sock,
-                                      SilcSKEStartPayload *start_payload,
-                                      SilcSKESendPacketCb send_packet,
-                                      void *context)
+                                      SilcSKEStartPayload *start_payload)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcBuffer payload_buf;
@@ -118,10 +204,12 @@ SilcSKEStatus silc_ske_initiator_start(SilcSKE ske, SilcRng rng,
   /* Take a copy of the payload buffer for future use. It is used to
      compute the HASH value. */
   ske->start_payload_copy = silc_buffer_copy(payload_buf);
+  ske->start_payload = start_payload;
 
   /* Send the packet. */
-  if (send_packet)
-    (*send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE, 
+                                  ske->callbacks->context);
 
   silc_buffer_free(payload_buf);
 
@@ -134,9 +222,7 @@ SilcSKEStatus silc_ske_initiator_start(SilcSKE ske, SilcRng rng,
    sent in the silc_ske_initiator_start function. */
 
 SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske, 
-                                        SilcBuffer start_payload,
-                                        SilcSKECb callback,
-                                        void *context)
+                                        SilcBuffer start_payload)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcSKEStartPayload *payload;
@@ -149,16 +235,43 @@ SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske,
   status = silc_ske_payload_start_decode(ske, start_payload, &payload);
   if (status != SILC_SKE_STATUS_OK) {
     ske->status = status;
+    silc_ske_payload_start_free(ske->start_payload);
+    return status;
+  }
+
+  /* Check that the cookie is returned unmodified */
+  if (memcmp(ske->start_payload->cookie, payload->cookie,
+            ske->start_payload->cookie_len)) {
+    SILC_LOG_ERROR(("Responder modified our cookie and it must not do it"));
+    ske->status = SILC_SKE_STATUS_INVALID_COOKIE;
+    silc_ske_payload_start_free(ske->start_payload);
     return status;
   }
 
+  /* Check version string */
+  if (ske->callbacks->check_version) {
+    status = ske->callbacks->check_version(ske, payload->version, 
+                                          payload->version_len,
+                                          ske->callbacks->context);
+    if (status != SILC_SKE_STATUS_OK) {
+      ske->status = status;
+      silc_ske_payload_start_free(ske->start_payload);
+      return status;
+    }
+  }
+
+  /* Free our KE Start Payload context, we don't need it anymore. */
+  silc_ske_payload_start_free(ske->start_payload);
+
   /* Take the selected security properties into use while doing
      the key exchange. This is used only while doing the key 
      exchange. The same data is returned to upper levels by calling
      the callback function. */
   ske->prop = prop = silc_calloc(1, sizeof(*prop));
+  if (!ske->prop)
+    goto err;
   prop->flags = payload->flags;
-  status = silc_ske_get_group_by_name(payload->ke_grp_list, &group);
+  status = silc_ske_group_get_by_name(payload->ke_grp_list, &group);
   if (status != SILC_SKE_STATUS_OK)
     goto err;
 
@@ -184,11 +297,12 @@ SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske,
     goto err;
   }
 
+  /* Save remote's KE Start Payload */
   ske->start_payload = payload;
 
   /* Return the received payload by calling the callback function. */
-  if (callback)
-    (*callback)(ske, context);
+  if (ske->callbacks->payload_receive)
+    (*ske->callbacks->payload_receive)(ske, ske->callbacks->context);
 
   return status;
 
@@ -196,7 +310,7 @@ SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske,
   if (payload)
     silc_ske_payload_start_free(payload);
 
-  silc_free(group);
+  silc_ske_group_free(group);
 
   if (prop->pkcs)
     silc_pkcs_free(prop->pkcs);
@@ -223,64 +337,72 @@ SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske,
 SilcSKEStatus silc_ske_initiator_phase_2(SilcSKE ske,
                                         SilcPublicKey public_key,
                                         SilcPrivateKey private_key,
-                                        SilcSKESendPacketCb send_packet,
-                                        void *context)
+                                        SilcSKEPKType pk_type)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcBuffer payload_buf;
-  SilcInt *x, e;
+  SilcMPInt *x;
   SilcSKEKEPayload *payload;
-  uint32 pk_len;
+  SilcUInt32 pk_len;
 
   SILC_LOG_DEBUG(("Start"));
 
   /* Create the random number x, 1 < x < q. */
   x = silc_calloc(1, sizeof(*x));
+  if (!x){
+    ske->status = SILC_SKE_STATUS_OUT_OF_MEMORY;
+    return ske->status;
+  }
   silc_mp_init(x);
   status = 
-    silc_ske_create_rnd(ske, ske->prop->group->group_order,
+    silc_ske_create_rnd(ske, &ske->prop->group->group_order,
                        silc_mp_sizeinbase(&ske->prop->group->group_order, 2),
                        x);
   if (status != SILC_SKE_STATUS_OK) {
-    silc_mp_clear(x);
+    silc_mp_uninit(x);
     silc_free(x);
     ske->status = status;
     return status;
   }
 
-  SILC_LOG_DEBUG(("Computing e = g ^ x mod p"));
-
-  /* Do the Diffie Hellman computation, e = g ^ x mod p */
-  silc_mp_init(&e);
-  silc_mp_powm(&e, &ske->prop->group->generator, x, 
-              &ske->prop->group->group);
-
   /* Encode the result to Key Exchange Payload. */
 
   payload = silc_calloc(1, sizeof(*payload));
+  if (!payload) {
+    silc_mp_uninit(x);
+    silc_free(x);
+    ske->status = SILC_SKE_STATUS_OUT_OF_MEMORY;
+    return ske->status;
+  }
   ske->ke1_payload = payload;
 
-  payload->x = e;
+  SILC_LOG_DEBUG(("Computing e = g ^ x mod p"));
+
+  /* Do the Diffie Hellman computation, e = g ^ x mod p */
+  silc_mp_init(&payload->x);
+  silc_mp_pow_mod(&payload->x, &ske->prop->group->generator, x, 
+                 &ske->prop->group->group);
 
   /* Get public key */
   if (public_key) {
     payload->pk_data = silc_pkcs_public_key_encode(public_key, &pk_len);
     if (!payload->pk_data) {
-      silc_mp_clear(x);
+      silc_mp_uninit(x);
       silc_free(x);
-      silc_mp_clear(&e);
+      silc_mp_uninit(&payload->x);
       silc_free(payload);
+      ske->ke1_payload = NULL;
       ske->status = SILC_SKE_STATUS_OK;
       return ske->status;
     }
     payload->pk_len = pk_len;
   }
-  payload->pk_type = SILC_SKE_PK_TYPE_SILC;
+  payload->pk_type = pk_type;
 
   /* Compute signature data if we are doing mutual authentication */
   if (private_key && ske->start_payload->flags & SILC_SKE_SP_FLAG_MUTUAL) {
-    unsigned char hash[32], sign[1024];
-    uint32 hash_len, sign_len;
+    unsigned char hash[32], sign[2048 + 1];
+    SilcUInt32 hash_len, sign_len;
 
     SILC_LOG_DEBUG(("We are doing mutual authentication"));
     SILC_LOG_DEBUG(("Computing HASH_i value"));
@@ -294,7 +416,17 @@ SilcSKEStatus silc_ske_initiator_phase_2(SilcSKE ske,
     /* Sign the hash value */
     silc_pkcs_private_key_data_set(ske->prop->pkcs, private_key->prv, 
                                   private_key->prv_len);
-    silc_pkcs_sign(ske->prop->pkcs, hash, hash_len, sign, &sign_len);
+    if (silc_pkcs_get_key_len(ske->prop->pkcs) / 8 > sizeof(sign) - 1 ||
+       !silc_pkcs_sign(ske->prop->pkcs, hash, hash_len, sign, &sign_len)) {
+      silc_mp_uninit(x);
+      silc_free(x);
+      silc_mp_uninit(&payload->x);
+      silc_free(payload->pk_data);
+      silc_free(payload);
+      ske->ke1_payload = NULL;
+      ske->status = SILC_SKE_STATUS_SIGNATURE_ERROR;
+      return ske->status;
+    }
     payload->sign_data = silc_calloc(sign_len, sizeof(unsigned char));
     memcpy(payload->sign_data, sign, sign_len);
     memset(sign, 0, sizeof(sign));
@@ -303,11 +435,13 @@ SilcSKEStatus silc_ske_initiator_phase_2(SilcSKE ske,
 
   status = silc_ske_payload_ke_encode(ske, payload, &payload_buf);
   if (status != SILC_SKE_STATUS_OK) {
-    silc_mp_clear(x);
+    silc_mp_uninit(x);
     silc_free(x);
-    silc_mp_clear(&e);
+    silc_mp_uninit(&payload->x);
     silc_free(payload->pk_data);
+    silc_free(payload->sign_data);
     silc_free(payload);
+    ske->ke1_payload = NULL;
     ske->status = status;
     return status;
   }
@@ -315,8 +449,10 @@ SilcSKEStatus silc_ske_initiator_phase_2(SilcSKE ske,
   ske->x = x;
 
   /* Send the packet. */
-  if (send_packet)
-    (*send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE_1, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, payload_buf, 
+                                  SILC_PACKET_KEY_EXCHANGE_1, 
+                                  ske->callbacks->context);
 
   silc_buffer_free(payload_buf);
 
@@ -326,34 +462,37 @@ SilcSKEStatus silc_ske_initiator_phase_2(SilcSKE ske,
 /* An initiator finish final callback that is called to indicate that
    the SKE protocol may continue. */
 
-typedef struct {
-  SilcSKECb callback;
-  void *context;
-} *SKEInitiatorFinish;
-
 static void silc_ske_initiator_finish_final(SilcSKE ske,
                                            SilcSKEStatus status,
                                            void *context)
 {
-  SKEInitiatorFinish finish = (SKEInitiatorFinish)context;
-  SilcSKEKEPayload *payload = ske->ke2_payload;
+  SilcSKEKEPayload *payload;
   unsigned char hash[32];
-  uint32 hash_len;
+  SilcUInt32 hash_len;
   SilcPublicKey public_key = NULL;
 
+  /* If the SKE was freed during the async call then free it really now,
+     otherwise just decrement the reference counter. */
+  if (ske->status == SILC_SKE_STATUS_FREED) {
+    silc_ske_free(ske);
+    return;
+  }
+
   /* If the caller returns PENDING status SKE library will assume that
      the caller will re-call this callback when it is not anymore in
      PENDING status. */
   if (status == SILC_SKE_STATUS_PENDING)
     return;
 
+  ske->users--;
+  payload = ske->ke2_payload;
+
   /* If the status is an error then the public key that was verified
      by the caller is not authentic. */
   if (status != SILC_SKE_STATUS_OK) {
     ske->status = status;
-    if (finish->callback)
-      finish->callback(ske, finish->context);
-    silc_free(finish);
+    if (ske->callbacks->proto_continue)
+      ske->callbacks->proto_continue(ske, ske->callbacks->context);
     return;
   }
 
@@ -362,9 +501,9 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
     if (!silc_pkcs_public_key_decode(payload->pk_data, payload->pk_len, 
                                     &public_key)) {
       status = SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY;
-      if (finish->callback)
-       finish->callback(ske, finish->context);
-      silc_free(finish);
+      SILC_LOG_ERROR(("Unsupported/malformed public key received"));
+      if (ske->callbacks->proto_continue)
+       ske->callbacks->proto_continue(ske, ske->callbacks->context);
       return;
     }
 
@@ -382,13 +521,10 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
     SILC_LOG_DEBUG(("Verifying signature (HASH)"));
 
     /* Verify signature */
-    silc_pkcs_public_key_data_set(ske->prop->pkcs, public_key->pk, 
-                                 public_key->pk_len);
+    silc_pkcs_public_key_set(ske->prop->pkcs, public_key);
     if (silc_pkcs_verify(ske->prop->pkcs, payload->sign_data, 
                         payload->sign_len, hash, hash_len) == FALSE) {
-      
-      SILC_LOG_DEBUG(("Signature don't match"));
-      
+      SILC_LOG_ERROR(("Signature verification failed, incorrect signature"));
       status = SILC_SKE_STATUS_INCORRECT_SIGNATURE;
       goto err;
     }
@@ -402,10 +538,9 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
   ske->status = SILC_SKE_STATUS_OK;
 
   /* Call the callback. The caller may now continue the SKE protocol. */
-  if (finish->callback)
-    finish->callback(ske, finish->context);
+  if (ske->callbacks->proto_continue)
+    ske->callbacks->proto_continue(ske, ske->callbacks->context);
 
-  silc_free(finish);
   return;
 
  err:
@@ -413,7 +548,7 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
   silc_ske_payload_ke_free(payload);
   ske->ke2_payload = NULL;
 
-  silc_mp_clear(ske->KEY);
+  silc_mp_uninit(ske->KEY);
   silc_free(ske->KEY);
   ske->KEY = NULL;
 
@@ -432,16 +567,15 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
   ske->status = status;
 
   /* Call the callback. */
-  if (finish->callback)
-    finish->callback(ske, finish->context);
-  silc_free(finish);
+  if (ske->callbacks->proto_continue)
+    ske->callbacks->proto_continue(ske, ske->callbacks->context);
 }
 
 /* Receives Key Exchange Payload from responder consisting responders
    public key, f, and signature. This function verifies the public key,
    computes the secret shared key and verifies the signature. 
 
-   The `callback' will be called to indicate that the caller may
+   The `proto_continue' will be called to indicate that the caller may
    continue with the SKE protocol.  The caller must not continue
    before the SKE libary has called that callback.  If this function
    returns an error the callback will not be called.  It is called
@@ -457,16 +591,11 @@ static void silc_ske_initiator_finish_final(SilcSKE ske,
    required for the remote to send its public key. */
 
 SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
-                                       SilcBuffer ke_payload,
-                                       SilcSKEVerifyCb verify_key,
-                                       void *verify_context,
-                                       SilcSKECb callback,
-                                       void *context)
+                                       SilcBuffer ke_payload)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcSKEKEPayload *payload;
-  SilcInt *KEY;
-  SKEInitiatorFinish finish;
+  SilcMPInt *KEY;
 
   SILC_LOG_DEBUG(("Start"));
 
@@ -478,7 +607,7 @@ SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
   }
   ske->ke2_payload = payload;
 
-  if (!payload->pk_data && verify_key) {
+  if (!payload->pk_data && ske->callbacks->verify_key) {
     SILC_LOG_DEBUG(("Remote end did not send its public key (or certificate), "
                    "even though we require it"));
     ske->status = SILC_SKE_STATUS_PUBLIC_KEY_NOT_PROVIDED;
@@ -490,19 +619,16 @@ SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
   /* Compute the shared secret key */
   KEY = silc_calloc(1, sizeof(*KEY));
   silc_mp_init(KEY);
-  silc_mp_powm(KEY, &payload->x, ske->x, &ske->prop->group->group);
+  silc_mp_pow_mod(KEY, &payload->x, ske->x, &ske->prop->group->group);
   ske->KEY = KEY;
 
-  finish = silc_calloc(1, sizeof(*finish));
-  finish->callback = callback;
-  finish->context = context;
-
-  if (payload->pk_data && verify_key) {
+  if (payload->pk_data && ske->callbacks->verify_key) {
     SILC_LOG_DEBUG(("Verifying public key"));
     
-    (*verify_key)(ske, payload->pk_data, payload->pk_len,
-                 payload->pk_type, verify_context,
-                 silc_ske_initiator_finish_final, finish);
+    ske->users++;
+    (*ske->callbacks->verify_key)(ske, payload->pk_data, payload->pk_len,
+                                payload->pk_type, ske->callbacks->context,
+                                silc_ske_initiator_finish_final, NULL);
     
     /* We will continue to the final state after the public key has
        been verified by the caller. */
@@ -510,7 +636,8 @@ SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
   }
 
   /* Continue to final state */
-  silc_ske_initiator_finish_final(ske, SILC_SKE_STATUS_OK, finish);
+  ske->users++;
+  silc_ske_initiator_finish_final(ske, SILC_SKE_STATUS_OK, NULL);
 
   return SILC_SKE_STATUS_OK;
 
@@ -518,7 +645,7 @@ SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
   silc_ske_payload_ke_free(payload);
   ske->ke2_payload = NULL;
 
-  silc_mp_clear(ske->KEY);
+  silc_mp_uninit(ske->KEY);
   silc_free(ske->KEY);
   ske->KEY = NULL;
 
@@ -537,11 +664,9 @@ SilcSKEStatus silc_ske_initiator_finish(SilcSKE ske,
 
 SilcSKEStatus silc_ske_responder_start(SilcSKE ske, SilcRng rng,
                                       SilcSocketConnection sock,
-                                      char *version,
+                                      const char *version,
                                       SilcBuffer start_payload,
-                                      int mutual_auth,
-                                      SilcSKECb callback,
-                                      void *context)
+                                      SilcSKESecurityPropertyFlag flags)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcSKEStartPayload *remote_payload = NULL, *payload = NULL;
@@ -563,11 +688,24 @@ SilcSKEStatus silc_ske_responder_start(SilcSKE ske, SilcRng rng,
   ske->start_payload_copy = silc_buffer_copy(start_payload);
 
   /* Force the mutual authentication flag if we want to do it. */
-  if (mutual_auth) {
+  if (flags & SILC_SKE_SP_FLAG_MUTUAL) {
     SILC_LOG_DEBUG(("Force mutual authentication"));
     remote_payload->flags |= SILC_SKE_SP_FLAG_MUTUAL;
   }
 
+  /* Force PFS flag if we require it */
+  if (flags & SILC_SKE_SP_FLAG_PFS) {
+    SILC_LOG_DEBUG(("Force PFS"));
+    remote_payload->flags |= SILC_SKE_SP_FLAG_PFS;
+  }
+
+  /* Disable IV Included flag if requested */
+  if (remote_payload->flags & SILC_SKE_SP_FLAG_IV_INCLUDED &&
+      !(flags & SILC_SKE_SP_FLAG_IV_INCLUDED)) {
+    SILC_LOG_DEBUG(("We do not support IV Included flag"));
+    remote_payload->flags &= ~SILC_SKE_SP_FLAG_IV_INCLUDED;
+  }
+
   /* Parse and select the security properties from the payload */
   payload = silc_calloc(1, sizeof(*payload));
   status = silc_ske_select_security_properties(ske, version,
@@ -578,8 +716,10 @@ SilcSKEStatus silc_ske_responder_start(SilcSKE ske, SilcRng rng,
   ske->start_payload = payload;
 
   /* Call the callback function. */
-  if (callback)
-    (*callback)(ske, context);
+  if (ske->callbacks->payload_receive)
+    (*ske->callbacks->payload_receive)(ske, ske->callbacks->context);
+
+  silc_ske_payload_start_free(remote_payload);
 
   return status;
 
@@ -599,10 +739,7 @@ SilcSKEStatus silc_ske_responder_start(SilcSKE ske, SilcRng rng,
 /* The selected security properties from the initiator payload is now 
    encoded into Key Exchange Start Payload and sent to the initiator. */
 
-SilcSKEStatus silc_ske_responder_phase_1(SilcSKE ske, 
-                                        SilcSKEStartPayload *start_payload,
-                                        SilcSKESendPacketCb send_packet,
-                                        void *context)
+SilcSKEStatus silc_ske_responder_phase_1(SilcSKE ske)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcBuffer payload_buf;
@@ -614,45 +751,47 @@ SilcSKEStatus silc_ske_responder_phase_1(SilcSKE ske,
   /* Allocate security properties from the payload. These are allocated
      only for this negotiation and will be free'd after KE is over. */
   ske->prop = prop = silc_calloc(1, sizeof(*prop));
-  prop->flags = start_payload->flags;
-  status = silc_ske_get_group_by_name(start_payload->ke_grp_list, &group);
+  prop->flags = ske->start_payload->flags;
+  status = silc_ske_group_get_by_name(ske->start_payload->ke_grp_list, &group);
   if (status != SILC_SKE_STATUS_OK)
     goto err;
 
   prop->group = group;
 
-  if (silc_pkcs_alloc(start_payload->pkcs_alg_list, 
+  if (silc_pkcs_alloc(ske->start_payload->pkcs_alg_list, 
                      &prop->pkcs) == FALSE) {
     status = SILC_SKE_STATUS_UNKNOWN_PKCS;
     goto err;
   }
 
-  if (silc_cipher_alloc(start_payload->enc_alg_list, 
+  if (silc_cipher_alloc(ske->start_payload->enc_alg_list, 
                        &prop->cipher) == FALSE) {
     status = SILC_SKE_STATUS_UNKNOWN_CIPHER;
     goto err;
   }
 
-  if (silc_hash_alloc(start_payload->hash_alg_list,
+  if (silc_hash_alloc(ske->start_payload->hash_alg_list,
                      &prop->hash) == FALSE) {
     status = SILC_SKE_STATUS_UNKNOWN_HASH_FUNCTION;
     goto err;
   }
 
-  if (silc_hmac_alloc(start_payload->hmac_alg_list, NULL,
+  if (silc_hmac_alloc(ske->start_payload->hmac_alg_list, NULL,
                      &prop->hmac) == FALSE) {
     status = SILC_SKE_STATUS_UNKNOWN_HMAC;
     goto err;
   }
 
   /* Encode the payload */
-  status = silc_ske_payload_start_encode(ske, start_payload, &payload_buf);
+  status = silc_ske_payload_start_encode(ske, ske->start_payload, 
+                                        &payload_buf);
   if (status != SILC_SKE_STATUS_OK)
     goto err;
 
   /* Send the packet. */
-  if (send_packet)
-    (*send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE, 
+                                  ske->callbacks->context);
 
   silc_buffer_free(payload_buf);
 
@@ -660,7 +799,7 @@ SilcSKEStatus silc_ske_responder_phase_1(SilcSKE ske,
 
  err:
   if (group)
-    silc_free(group);
+    silc_ske_group_free(group);
 
   if (prop->pkcs)
     silc_pkcs_free(prop->pkcs);
@@ -683,20 +822,19 @@ SilcSKEStatus silc_ske_responder_phase_1(SilcSKE ske,
 /* An responder phase 2 final callback that is called to indicate that
    the SKE protocol may continue. */
 
-typedef struct {
-  SilcSKECb callback;
-  void *context;
-} *SKEResponderPhaseII;
-
 static void silc_ske_responder_phase2_final(SilcSKE ske,
                                            SilcSKEStatus status,
                                            void *context)
 {
-  SKEResponderPhaseII finish = (SKEResponderPhaseII)context;
   SilcSKEKEPayload *recv_payload, *send_payload;
-  SilcInt *x, f;
+  SilcMPInt *x;
 
-  recv_payload = ske->ke1_payload;
+  /* If the SKE was freed during the async call then free it really now,
+     otherwise just decrement the reference counter. */
+  if (ske->status == SILC_SKE_STATUS_FREED) {
+    silc_ske_free(ske);
+    return;
+  }
 
   /* If the caller returns PENDING status SKE library will assume that
      the caller will re-call this callback when it is not anymore in
@@ -704,13 +842,15 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
   if (status == SILC_SKE_STATUS_PENDING)
     return;
 
+  ske->users--;
+  recv_payload = ske->ke1_payload;
+
   /* If the status is an error then the public key that was verified
      by the caller is not authentic. */
   if (status != SILC_SKE_STATUS_OK) {
     ske->status = status;
-    if (finish->callback)
-      finish->callback(ske, finish->context);
-    silc_free(finish);
+    if (ske->callbacks->proto_continue)
+      ske->callbacks->proto_continue(ske, ske->callbacks->context);
     return;
   }
 
@@ -720,16 +860,16 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
       ske->start_payload->flags & SILC_SKE_SP_FLAG_MUTUAL) {
     SilcPublicKey public_key = NULL;
     unsigned char hash[32];
-    uint32 hash_len;
+    SilcUInt32 hash_len;
 
     /* Decode the public key */
     if (!silc_pkcs_public_key_decode(recv_payload->pk_data, 
                                     recv_payload->pk_len, 
                                     &public_key)) {
       ske->status = SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY;
-      if (finish->callback)
-       finish->callback(ske, finish->context);
-      silc_free(finish);
+      SILC_LOG_ERROR(("Unsupported/malformed public key received"));
+      if (ske->callbacks->proto_continue)
+       ske->callbacks->proto_continue(ske, ske->callbacks->context);
       return;
     }
 
@@ -739,26 +879,21 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
     status = silc_ske_make_hash(ske, hash, &hash_len, TRUE);
     if (status != SILC_SKE_STATUS_OK) {
       ske->status = status;
-      if (finish->callback)
-       finish->callback(ske, finish->context);
-      silc_free(finish);
+      if (ske->callbacks->proto_continue)
+       ske->callbacks->proto_continue(ske, ske->callbacks->context);
       return;
     }
 
     SILC_LOG_DEBUG(("Verifying signature (HASH_i)"));
     
     /* Verify signature */
-    silc_pkcs_public_key_data_set(ske->prop->pkcs, public_key->pk, 
-                                 public_key->pk_len);
+    silc_pkcs_public_key_set(ske->prop->pkcs, public_key);
     if (silc_pkcs_verify(ske->prop->pkcs, recv_payload->sign_data, 
                         recv_payload->sign_len, hash, hash_len) == FALSE) {
-      
-      SILC_LOG_DEBUG(("Signature don't match"));
-      
+      SILC_LOG_ERROR(("Signature verification failed, incorrect signature"));
       ske->status = SILC_SKE_STATUS_INCORRECT_SIGNATURE;
-      if (finish->callback)
-       finish->callback(ske, finish->context);
-      silc_free(finish);
+      if (ske->callbacks->proto_continue)
+       ske->callbacks->proto_continue(ske, ske->callbacks->context);
       return;
     }
     
@@ -772,37 +907,34 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
   x = silc_calloc(1, sizeof(*x));
   silc_mp_init(x);
   status = 
-    silc_ske_create_rnd(ske, ske->prop->group->group_order,
+    silc_ske_create_rnd(ske, &ske->prop->group->group_order,
                        silc_mp_sizeinbase(&ske->prop->group->group_order, 2),
                        x);
   if (status != SILC_SKE_STATUS_OK) {
-    silc_mp_clear(x);
+    silc_mp_uninit(x);
     silc_free(x);
     ske->status = status;
-    if (finish->callback)
-      finish->callback(ske, finish->context);
-    silc_free(finish);
+    if (ske->callbacks->proto_continue)
+      ske->callbacks->proto_continue(ske, ske->callbacks->context);
     return;
   }
 
-  SILC_LOG_DEBUG(("Computing f = g ^ x mod p"));
-
-  /* Do the Diffie Hellman computation, f = g ^ x mod p */
-  silc_mp_init(&f);
-  silc_mp_powm(&f, &ske->prop->group->generator, x, 
-              &ske->prop->group->group);
-  
   /* Save the results for later processing */
   send_payload = silc_calloc(1, sizeof(*send_payload));
-  send_payload->x = f;
   ske->x = x;
   ske->ke2_payload = send_payload;
 
+  SILC_LOG_DEBUG(("Computing f = g ^ x mod p"));
+
+  /* Do the Diffie Hellman computation, f = g ^ x mod p */
+  silc_mp_init(&send_payload->x);
+  silc_mp_pow_mod(&send_payload->x, &ske->prop->group->generator, x, 
+                 &ske->prop->group->group);
+  
   /* Call the callback. The caller may now continue with the SKE protocol. */
   ske->status = SILC_SKE_STATUS_OK;
-  if (finish->callback)
-    finish->callback(ske, finish->context);
-  silc_free(finish);
+  if (ske->callbacks->proto_continue)
+    ske->callbacks->proto_continue(ske, ske->callbacks->context);
 }
 
 /* This function receives the Key Exchange Payload from the initiator.
@@ -811,7 +943,7 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
    and computes f = g ^ x mod p. This then puts the result f to a Key
    Exchange Payload. 
 
-   The `callback' will be called to indicate that the caller may
+   The `proto_continue' will be called to indicate that the caller may
    continue with the SKE protocol.  The caller must not continue
    before the SKE libary has called that callback.  If this function
    returns an error the callback will not be called.  It is called
@@ -825,15 +957,10 @@ static void silc_ske_responder_phase2_final(SilcSKE ske,
    is considered to be an error if remote does not send its public key. */
 
 SilcSKEStatus silc_ske_responder_phase_2(SilcSKE ske,
-                                        SilcBuffer ke_payload,
-                                        SilcSKEVerifyCb verify_key,
-                                        void *verify_context,
-                                        SilcSKECb callback,
-                                        void *context)
+                                        SilcBuffer ke_payload)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcSKEKEPayload *recv_payload;
-  SKEResponderPhaseII finish;
 
   SILC_LOG_DEBUG(("Start"));
 
@@ -846,10 +973,6 @@ SilcSKEStatus silc_ske_responder_phase_2(SilcSKE ske,
 
   ske->ke1_payload = recv_payload;
 
-  finish = silc_calloc(1, sizeof(*finish));
-  finish->callback = callback;
-  finish->context = context;
-
   /* Verify the received public key and verify the signature if we are
      doing mutual authentication. */
   if (ske->start_payload && 
@@ -857,19 +980,22 @@ SilcSKEStatus silc_ske_responder_phase_2(SilcSKE ske,
 
     SILC_LOG_DEBUG(("We are doing mutual authentication"));
     
-    if (!recv_payload->pk_data && verify_key) {
-      SILC_LOG_DEBUG(("Remote end did not send its public key (or "
+    if (!recv_payload->pk_data && ske->callbacks->verify_key) {
+      SILC_LOG_ERROR(("Remote end did not send its public key (or "
                      "certificate), even though we require it"));
       ske->status = SILC_SKE_STATUS_PUBLIC_KEY_NOT_PROVIDED;
       return status;
     }
 
-    if (recv_payload->pk_data && verify_key) {
+    if (recv_payload->pk_data && ske->callbacks->verify_key) {
       SILC_LOG_DEBUG(("Verifying public key"));
 
-      (*verify_key)(ske, recv_payload->pk_data, recv_payload->pk_len,
-                   recv_payload->pk_type, verify_context,
-                   silc_ske_responder_phase2_final, finish);
+      ske->users++;
+      (*ske->callbacks->verify_key)(ske, recv_payload->pk_data, 
+                                   recv_payload->pk_len,
+                                   recv_payload->pk_type, 
+                                   ske->callbacks->context,
+                                   silc_ske_responder_phase2_final, NULL);
 
       /* We will continue to the final state after the public key has
         been verified by the caller. */
@@ -878,7 +1004,8 @@ SilcSKEStatus silc_ske_responder_phase_2(SilcSKE ske,
   }
 
   /* Continue to final state */
-  silc_ske_responder_phase2_final(ske, SILC_SKE_STATUS_OK, finish);
+  ske->users++;
+  silc_ske_responder_phase2_final(ske, SILC_SKE_STATUS_OK, NULL);
 
   return SILC_SKE_STATUS_OK;
 }
@@ -890,15 +1017,13 @@ SilcSKEStatus silc_ske_responder_phase_2(SilcSKE ske,
 SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
                                        SilcPublicKey public_key,
                                        SilcPrivateKey private_key,
-                                       SilcSKEPKType pk_type,
-                                       SilcSKESendPacketCb send_packet,
-                                       void *context)
+                                       SilcSKEPKType pk_type)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcBuffer payload_buf;
-  SilcInt *KEY;
-  unsigned char hash[32], sign[1024], *pk;
-  uint32 hash_len, sign_len, pk_len;
+  SilcMPInt *KEY;
+  unsigned char hash[32], sign[2048 + 1], *pk;
+  SilcUInt32 hash_len, sign_len, pk_len;
 
   SILC_LOG_DEBUG(("Start"));
 
@@ -907,8 +1032,8 @@ SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
   /* Compute the shared secret key */
   KEY = silc_calloc(1, sizeof(*KEY));
   silc_mp_init(KEY);
-  silc_mp_powm(KEY, &ske->ke1_payload->x, ske->x, 
-              &ske->prop->group->group);
+  silc_mp_pow_mod(KEY, &ske->ke1_payload->x, ske->x, 
+                 &ske->prop->group->group);
   ske->KEY = KEY;
 
   if (public_key && private_key) {
@@ -917,7 +1042,7 @@ SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
     /* Get the public key */
     pk = silc_pkcs_public_key_encode(public_key, &pk_len);
     if (!pk) {
-      status = SILC_SKE_STATUS_ERROR;
+      status = SILC_SKE_STATUS_OUT_OF_MEMORY;
       goto err;
     }
     ske->ke2_payload->pk_data = pk;
@@ -940,7 +1065,11 @@ SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
     /* Sign the hash value */
     silc_pkcs_private_key_data_set(ske->prop->pkcs, private_key->prv, 
                                   private_key->prv_len);
-    silc_pkcs_sign(ske->prop->pkcs, hash, hash_len, sign, &sign_len);
+    if (silc_pkcs_get_key_len(ske->prop->pkcs) / 8 > sizeof(sign) - 1 ||
+       !silc_pkcs_sign(ske->prop->pkcs, hash, hash_len, sign, &sign_len)) {
+      status = SILC_SKE_STATUS_SIGNATURE_ERROR;
+      goto err;
+    }
     ske->ke2_payload->sign_data = silc_calloc(sign_len, sizeof(unsigned char));
     memcpy(ske->ke2_payload->sign_data, sign, sign_len);
     memset(sign, 0, sizeof(sign));
@@ -955,15 +1084,17 @@ SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
     goto err;
 
   /* Send the packet. */
-  if (send_packet)
-    (*send_packet)(ske, payload_buf, SILC_PACKET_KEY_EXCHANGE_2, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, payload_buf, 
+                                  SILC_PACKET_KEY_EXCHANGE_2,
+                                  ske->callbacks->context);
 
   silc_buffer_free(payload_buf);
 
   return status;
 
  err:
-  silc_mp_clear(ske->KEY);
+  silc_mp_uninit(ske->KEY);
   silc_free(ske->KEY);
   ske->KEY = NULL;
   silc_ske_payload_ke_free(ske->ke2_payload);
@@ -979,22 +1110,22 @@ SilcSKEStatus silc_ske_responder_finish(SilcSKE ske,
    must not be called until the keys are processed like the protocol
    defines. This function is for both initiator and responder. */
 
-SilcSKEStatus silc_ske_end(SilcSKE ske,
-                          SilcSKESendPacketCb send_packet,
-                          void *context)
+SilcSKEStatus silc_ske_end(SilcSKE ske)
 {
   SilcBuffer packet;
 
   SILC_LOG_DEBUG(("Start"));
 
-  packet = silc_buffer_alloc(4);
-  silc_buffer_pull_tail(packet, SILC_BUFFER_END(packet));
+  packet = silc_buffer_alloc_size(4);
+  if (!packet)
+    return SILC_SKE_STATUS_OUT_OF_MEMORY;
   silc_buffer_format(packet,
-                    SILC_STR_UI_INT((uint32)SILC_SKE_STATUS_OK),
+                    SILC_STR_UI_INT((SilcUInt32)SILC_SKE_STATUS_OK),
                     SILC_STR_END);
 
-  if (send_packet)
-    (*send_packet)(ske, packet, SILC_PACKET_SUCCESS, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, packet, SILC_PACKET_SUCCESS, 
+                                  ske->callbacks->context);
 
   silc_buffer_free(packet);
 
@@ -1005,22 +1136,25 @@ SilcSKEStatus silc_ske_end(SilcSKE ske,
    while performing the protocol. The status argument is the error
    status and it is sent to the remote end. */
 
-SilcSKEStatus silc_ske_abort(SilcSKE ske, SilcSKEStatus status,
-                            SilcSKESendPacketCb send_packet,
-                            void *context)
+SilcSKEStatus silc_ske_abort(SilcSKE ske, SilcSKEStatus status)
 {
   SilcBuffer packet;
 
   SILC_LOG_DEBUG(("Start"));
 
-  packet = silc_buffer_alloc(4);
-  silc_buffer_pull_tail(packet, SILC_BUFFER_END(packet));
+  if (status > SILC_SKE_STATUS_INVALID_COOKIE)
+    status = SILC_SKE_STATUS_BAD_PAYLOAD;
+
+  packet = silc_buffer_alloc_size(4);
+  if (!packet)
+    return SILC_SKE_STATUS_OUT_OF_MEMORY;
   silc_buffer_format(packet,
-                    SILC_STR_UI_INT((uint32)status),
+                    SILC_STR_UI_INT((SilcUInt32)status),
                     SILC_STR_END);
 
-  if (send_packet)
-    (*send_packet)(ske, packet, SILC_PACKET_FAILURE, context);
+  if (ske->callbacks->send_packet)
+    (*ske->callbacks->send_packet)(ske, packet, SILC_PACKET_FAILURE, 
+                                  ske->callbacks->context);
 
   silc_buffer_free(packet);
 
@@ -1036,8 +1170,8 @@ SilcSKEStatus silc_ske_abort(SilcSKE ske, SilcSKEStatus status,
 
 SilcSKEStatus 
 silc_ske_assemble_security_properties(SilcSKE ske,
-                                     unsigned char flags,
-                                     char *version,
+                                     SilcSKESecurityPropertyFlag flags,
+                                     const char *version,
                                      SilcSKEStartPayload **return_payload)
 {
   SilcSKEStartPayload *rp;
@@ -1048,12 +1182,12 @@ silc_ske_assemble_security_properties(SilcSKE ske,
   rp = silc_calloc(1, sizeof(*rp));
 
   /* Set flags */
-  rp->flags = flags;
+  rp->flags = (unsigned char)flags;
 
   /* Set random cookie */
   rp->cookie = silc_calloc(SILC_SKE_COOKIE_LEN, sizeof(*rp->cookie));
   for (i = 0; i < SILC_SKE_COOKIE_LEN; i++)
-    rp->cookie[i] = silc_rng_get_byte(ske->rng);
+    rp->cookie[i] = silc_rng_get_byte_fast(ske->rng);
   rp->cookie_len = SILC_SKE_COOKIE_LEN;
 
   /* Put version */
@@ -1082,8 +1216,8 @@ silc_ske_assemble_security_properties(SilcSKE ske,
 
   /* XXX */
   /* Get supported compression algorithms */
-  rp->comp_alg_list = "";
-  rp->comp_alg_len = 0;
+  rp->comp_alg_list = strdup("none");
+  rp->comp_alg_len = strlen("none");
 
   rp->len = 1 + 1 + 2 + SILC_SKE_COOKIE_LEN + 
     2 + rp->version_len +
@@ -1101,7 +1235,7 @@ silc_ske_assemble_security_properties(SilcSKE ske,
 
 SilcSKEStatus 
 silc_ske_select_security_properties(SilcSKE ske,
-                                   char *version,
+                                   const char *version,
                                    SilcSKEStartPayload *payload,
                                    SilcSKEStartPayload *remote_payload)
 {
@@ -1115,16 +1249,22 @@ silc_ske_select_security_properties(SilcSKE ske,
   rp = remote_payload;
 
   /* Check version string */
-  status = silc_ske_check_version(ske, rp->version, rp->version_len);
-  if (status != SILC_SKE_STATUS_OK) {
-    ske->status = status;
-    return status;
+  if (ske->callbacks->check_version) {
+    status = ske->callbacks->check_version(ske, rp->version, 
+                                          rp->version_len,
+                                          ske->callbacks->context);
+    if (status != SILC_SKE_STATUS_OK) {
+      ske->status = status;
+      return status;
+    }
   }
 
+  ske->remote_version = silc_memdup(rp->version, rp->version_len);
+
   /* Flags are returned unchanged. */
   payload->flags = rp->flags;
 
-  /* Take cookie */
+  /* Take cookie, we must return it to sender unmodified. */
   payload->cookie = silc_calloc(SILC_SKE_COOKIE_LEN, sizeof(unsigned char));
   payload->cookie_len = SILC_SKE_COOKIE_LEN;
   memcpy(payload->cookie, rp->cookie, SILC_SKE_COOKIE_LEN);
@@ -1145,7 +1285,7 @@ silc_ske_select_security_properties(SilcSKE ske,
 
       SILC_LOG_DEBUG(("Proposed KE group `%s'", item));
 
-      if (silc_ske_get_group_by_name(item, NULL) == SILC_SKE_STATUS_OK) {
+      if (silc_ske_group_get_by_name(item, NULL) == SILC_SKE_STATUS_OK) {
        SILC_LOG_DEBUG(("Found KE group `%s'", item));
 
        payload->ke_grp_len = len;
@@ -1403,9 +1543,8 @@ silc_ske_select_security_properties(SilcSKE ske,
     payload->hmac_alg_list = strdup(rp->hmac_alg_list);
   }
 
-#if 0
   /* Get supported compression algorithms */
-  cp = rp->hash_alg_list;
+  cp = rp->comp_alg_list;
   if (cp && strchr(cp, ',')) {
     while(cp) {
       char *item;
@@ -1414,15 +1553,23 @@ silc_ske_select_security_properties(SilcSKE ske,
       item = silc_calloc(len + 1, sizeof(char));
       memcpy(item, cp, len);
 
-      SILC_LOG_DEBUG(("Proposed hash alg `%s'", item));
-
-      if (silc_hash_is_supported(item) == TRUE) {
-       SILC_LOG_DEBUG(("Found hash alg `%s'", item));
+      SILC_LOG_DEBUG(("Proposed Compression `%s'", item));
 
-       payload->hash_alg_len = len;
-       payload->hash_alg_list = item;
+#if 1
+      if (!strcmp(item, "none")) {
+       SILC_LOG_DEBUG(("Found Compression `%s'", item));
+       payload->comp_alg_len = len;
+       payload->comp_alg_list = item;
        break;
       }
+#else
+      if (silc_hmac_is_supported(item) == TRUE) {
+       SILC_LOG_DEBUG(("Found Compression `%s'", item));
+       payload->comp_alg_len = len;
+       payload->comp_alg_list = item;
+       break;
+      }
+#endif
 
       cp += len;
       if (strlen(cp) == 0)
@@ -1433,20 +1580,7 @@ silc_ske_select_security_properties(SilcSKE ske,
       if (item)
        silc_free(item);
     }
-
-    if (!payload->hash_alg_len && !payload->hash_alg_list) {
-      SILC_LOG_DEBUG(("Could not find supported hash alg"));
-      silc_ske_abort(ske, SILC_SKE_STATUS_UNKNOWN_HASH_FUNCTION);
-      silc_free(payload->ke_grp_list);
-      silc_free(payload->pkcs_alg_list);
-      silc_free(payload->enc_alg_list);
-      silc_free(payload);
-      return;
-    }
-  } else {
-
   }
-#endif
 
   payload->len = 1 + 1 + 2 + SILC_SKE_COOKIE_LEN + 
     2 + payload->version_len + 
@@ -1460,32 +1594,37 @@ silc_ske_select_security_properties(SilcSKE ske,
 /* Creates random number such that 1 < rnd < n and at most length
    of len bits. The rnd sent as argument must be initialized. */
 
-SilcSKEStatus silc_ske_create_rnd(SilcSKE ske, SilcInt n, 
-                                 uint32 len, 
-                                 SilcInt *rnd)
+static SilcSKEStatus silc_ske_create_rnd(SilcSKE ske, SilcMPInt *n, 
+                                        SilcUInt32 len, 
+                                        SilcMPInt *rnd)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   unsigned char *string;
+  SilcUInt32 l;
+
+  if (!len)
+    return SILC_SKE_STATUS_ERROR;
 
   SILC_LOG_DEBUG(("Creating random number"));
 
+  l = ((len - 1) / 8);
+
   /* Get the random number as string */
-  string = silc_rng_get_rn_data(ske->rng, (len / 8));
+  string = silc_rng_get_rn_data(ske->rng, l);
   if (!string)
-    return SILC_SKE_STATUS_ERROR;
+    return SILC_SKE_STATUS_OUT_OF_MEMORY;
 
   /* Decode the string into a MP integer */
-  silc_mp_bin2mp(string, (len / 8), rnd);
+  silc_mp_bin2mp(string, l, rnd);
   silc_mp_mod_2exp(rnd, rnd, len);
 
   /* Checks */
   if (silc_mp_cmp_ui(rnd, 1) < 0)
     status = SILC_SKE_STATUS_ERROR;
-
-  if (silc_mp_cmp(rnd, &n) >= 0)
+  if (silc_mp_cmp(rnd, n) >= 0)
     status = SILC_SKE_STATUS_ERROR;
 
-  memset(string, 'F', (len / 8));
+  memset(string, 'F', l);
   silc_free(string);
 
   return status;
@@ -1496,15 +1635,15 @@ SilcSKEStatus silc_ske_create_rnd(SilcSKE ske, SilcInt n,
    hash value defined in the protocol. If it is FALSE then this is used
    to create the HASH value defined by the protocol. */
 
-SilcSKEStatus silc_ske_make_hash(SilcSKE ske, 
-                                unsigned char *return_hash,
-                                uint32 *return_hash_len,
-                                int initiator)
+static SilcSKEStatus silc_ske_make_hash(SilcSKE ske, 
+                                       unsigned char *return_hash,
+                                       SilcUInt32 *return_hash_len,
+                                       int initiator)
 {
   SilcSKEStatus status = SILC_SKE_STATUS_OK;
   SilcBuffer buf;
   unsigned char *e, *f, *KEY;
-  uint32 e_len, f_len, KEY_len;
+  SilcUInt32 e_len, f_len, KEY_len;
   int ret;
 
   SILC_LOG_DEBUG(("Start"));
@@ -1514,20 +1653,44 @@ SilcSKEStatus silc_ske_make_hash(SilcSKE ske,
     f = silc_mp_mp2bin(&ske->ke2_payload->x, 0, &f_len);
     KEY = silc_mp_mp2bin(ske->KEY, 0, &KEY_len);
     
-    buf = silc_buffer_alloc(ske->start_payload_copy->len + 
-                           ske->pk_len + e_len + f_len + KEY_len);
-    silc_buffer_pull_tail(buf, SILC_BUFFER_END(buf));
-    
     /* Format the buffer used to compute the hash value */
-    ret = 
-      silc_buffer_format(buf,
-                        SILC_STR_UI_XNSTRING(ske->start_payload_copy->data,
-                                             ske->start_payload_copy->len),
-                        SILC_STR_UI_XNSTRING(ske->pk, ske->pk_len),
-                        SILC_STR_UI_XNSTRING(e, e_len),
-                        SILC_STR_UI_XNSTRING(f, f_len),
-                        SILC_STR_UI_XNSTRING(KEY, KEY_len),
-                        SILC_STR_END);
+    buf = silc_buffer_alloc_size(ske->start_payload_copy->len + 
+                                ske->ke2_payload->pk_len + 
+                                ske->ke1_payload->pk_len + 
+                                e_len + f_len + KEY_len);
+    if (!buf)
+      return SILC_SKE_STATUS_OUT_OF_MEMORY;
+
+    /* Initiator is not required to send its public key */
+    if (!ske->ke1_payload->pk_data) {
+      ret = 
+       silc_buffer_format(buf,
+                          SILC_STR_UI_XNSTRING(ske->start_payload_copy->
+                                               data,
+                                               ske->start_payload_copy->
+                                               len),
+                          SILC_STR_UI_XNSTRING(ske->ke2_payload->pk_data, 
+                                               ske->ke2_payload->pk_len),
+                          SILC_STR_UI_XNSTRING(e, e_len),
+                          SILC_STR_UI_XNSTRING(f, f_len),
+                          SILC_STR_UI_XNSTRING(KEY, KEY_len),
+                          SILC_STR_END);
+    } else {
+      ret = 
+       silc_buffer_format(buf,
+                          SILC_STR_UI_XNSTRING(ske->start_payload_copy->
+                                               data,
+                                               ske->start_payload_copy->
+                                               len),
+                          SILC_STR_UI_XNSTRING(ske->ke2_payload->pk_data, 
+                                               ske->ke2_payload->pk_len),
+                          SILC_STR_UI_XNSTRING(ske->ke1_payload->pk_data, 
+                                               ske->ke1_payload->pk_len),
+                          SILC_STR_UI_XNSTRING(e, e_len),
+                          SILC_STR_UI_XNSTRING(f, f_len),
+                          SILC_STR_UI_XNSTRING(KEY, KEY_len),
+                          SILC_STR_END);
+    }
     if (ret == -1) {
       silc_buffer_free(buf);
       memset(e, 0, e_len);
@@ -1548,16 +1711,18 @@ SilcSKEStatus silc_ske_make_hash(SilcSKE ske,
   } else {
     e = silc_mp_mp2bin(&ske->ke1_payload->x, 0, &e_len);
 
-    buf = silc_buffer_alloc(ske->start_payload_copy->len + 
-                           ske->pk_len + e_len);
-    silc_buffer_pull_tail(buf, SILC_BUFFER_END(buf));
+    buf = silc_buffer_alloc_size(ske->start_payload_copy->len + 
+                                 ske->ke1_payload->pk_len + e_len);
+    if (!buf)
+      return SILC_SKE_STATUS_OUT_OF_MEMORY;
     
     /* Format the buffer used to compute the hash value */
     ret = 
       silc_buffer_format(buf,
                         SILC_STR_UI_XNSTRING(ske->start_payload_copy->data,
                                              ske->start_payload_copy->len),
-                        SILC_STR_UI_XNSTRING(ske->pk, ske->pk_len),
+                        SILC_STR_UI_XNSTRING(ske->ke1_payload->pk_data, 
+                                             ske->ke1_payload->pk_len),
                         SILC_STR_UI_XNSTRING(e, e_len),
                         SILC_STR_END);
     if (ret == -1) {
@@ -1573,7 +1738,7 @@ SilcSKEStatus silc_ske_make_hash(SilcSKE ske,
 
   /* Make the hash */
   silc_hash_make(ske->prop->hash, buf->data, buf->len, return_hash);
-  *return_hash_len = ske->prop->hash->hash->hash_len;
+  *return_hash_len = silc_hash_len(ske->prop->hash);
 
   if (initiator == FALSE) {
     SILC_LOG_HEXDUMP(("HASH"), return_hash, *return_hash_len);
@@ -1587,29 +1752,30 @@ SilcSKEStatus silc_ske_make_hash(SilcSKE ske,
 }
 
 /* Processes the provided key material `data' as the SILC protocol 
-   specification specifies. */
+   specification defines. */
 
 SilcSKEStatus 
 silc_ske_process_key_material_data(unsigned char *data,
-                                  uint32 data_len,
-                                  uint32 req_iv_len,
-                                  uint32 req_enc_key_len,
-                                  uint32 req_hmac_key_len,
+                                  SilcUInt32 data_len,
+                                  SilcUInt32 req_iv_len,
+                                  SilcUInt32 req_enc_key_len,
+                                  SilcUInt32 req_hmac_key_len,
                                   SilcHash hash,
                                   SilcSKEKeyMaterial *key)
 {
   SilcBuffer buf;
   unsigned char hashd[32];
-  uint32 hash_len = req_hmac_key_len;
-  uint32 enc_key_len = req_enc_key_len / 8;
+  SilcUInt32 hash_len = req_hmac_key_len;
+  SilcUInt32 enc_key_len = req_enc_key_len / 8;
 
   SILC_LOG_DEBUG(("Start"));
 
   if (!req_iv_len || !req_enc_key_len || !req_hmac_key_len)
     return SILC_SKE_STATUS_ERROR;
 
-  buf = silc_buffer_alloc(1 + data_len);
-  silc_buffer_pull_tail(buf, SILC_BUFFER_END(buf));
+  buf = silc_buffer_alloc_size(1 + data_len);
+  if (!buf)
+    return SILC_SKE_STATUS_OUT_OF_MEMORY;
   silc_buffer_format(buf,
                     SILC_STR_UI_CHAR(0),
                     SILC_STR_UI_XNSTRING(data, data_len),
@@ -1646,15 +1812,16 @@ silc_ske_process_key_material_data(unsigned char *data,
     silc_hash_make(hash, buf->data, buf->len, k1);
     
     /* Take second round */
-    dist = silc_buffer_alloc(data_len + hash_len);
-    silc_buffer_pull_tail(dist, SILC_BUFFER_END(dist));
+    dist = silc_buffer_alloc_size(data_len + hash_len);
+    if (!dist)
+      return SILC_SKE_STATUS_OUT_OF_MEMORY;
     silc_buffer_format(dist,
                       SILC_STR_UI_XNSTRING(data, data_len),
                       SILC_STR_UI_XNSTRING(k1, hash_len),
                       SILC_STR_END);
     memset(k2, 0, sizeof(k2));
     silc_hash_make(hash, dist->data, dist->len, k2);
-    
+
     /* Take third round */
     dist = silc_buffer_realloc(dist, data_len + hash_len + hash_len);
     silc_buffer_pull_tail(dist, hash_len);
@@ -1670,7 +1837,7 @@ silc_ske_process_key_material_data(unsigned char *data,
     dtmp = silc_calloc((3 * hash_len), sizeof(unsigned char));
     memcpy(dtmp, k1, hash_len);
     memcpy(dtmp + hash_len, k2, hash_len);
-    memcpy(dtmp + hash_len, k3, hash_len);
+    memcpy(dtmp + hash_len + hash_len, k3, hash_len);
 
     key->send_enc_key = silc_calloc(enc_key_len, sizeof(unsigned char));
     memcpy(key->send_enc_key, dtmp, enc_key_len);
@@ -1681,6 +1848,7 @@ silc_ske_process_key_material_data(unsigned char *data,
     memset(k2, 0, sizeof(k2));
     memset(k3, 0, sizeof(k3));
     silc_free(dtmp);
+    silc_buffer_clear(dist);
     silc_buffer_free(dist);
   } else {
     /* Take normal hash as key */
@@ -1706,8 +1874,9 @@ silc_ske_process_key_material_data(unsigned char *data,
     silc_hash_make(hash, buf->data, buf->len, k1);
     
     /* Take second round */
-    dist = silc_buffer_alloc(data_len + hash_len);
-    silc_buffer_pull_tail(dist, SILC_BUFFER_END(dist));
+    dist = silc_buffer_alloc_size(data_len + hash_len);
+    if (!dist)
+      return SILC_SKE_STATUS_OUT_OF_MEMORY;
     silc_buffer_format(dist,
                       SILC_STR_UI_XNSTRING(data, data_len),
                       SILC_STR_UI_XNSTRING(k1, hash_len),
@@ -1730,7 +1899,7 @@ silc_ske_process_key_material_data(unsigned char *data,
     dtmp = silc_calloc((3 * hash_len), sizeof(unsigned char));
     memcpy(dtmp, k1, hash_len);
     memcpy(dtmp + hash_len, k2, hash_len);
-    memcpy(dtmp + hash_len, k3, hash_len);
+    memcpy(dtmp + hash_len + hash_len, k3, hash_len);
 
     key->receive_enc_key = silc_calloc(enc_key_len, sizeof(unsigned char));
     memcpy(key->receive_enc_key, dtmp, enc_key_len);
@@ -1741,6 +1910,7 @@ silc_ske_process_key_material_data(unsigned char *data,
     memset(k2, 0, sizeof(k2));
     memset(k3, 0, sizeof(k3));
     silc_free(dtmp);
+    silc_buffer_clear(dist);
     silc_buffer_free(dist);
   } else {
     /* Take normal hash as key */
@@ -1751,14 +1921,21 @@ silc_ske_process_key_material_data(unsigned char *data,
     key->enc_key_len = req_enc_key_len;
   }
 
-  /* Take HMAC key */
+  /* Take HMAC keys */
   memset(hashd, 0, sizeof(hashd));
   buf->data[0] = 4;
   silc_hash_make(hash, buf->data, buf->len, hashd);
-  key->hmac_key = silc_calloc(req_hmac_key_len, sizeof(unsigned char));
-  memcpy(key->hmac_key, hashd, req_hmac_key_len);
+  key->send_hmac_key = silc_calloc(req_hmac_key_len, sizeof(unsigned char));
+  memcpy(key->send_hmac_key, hashd, req_hmac_key_len);
+  memset(hashd, 0, sizeof(hashd));
+  buf->data[0] = 5;
+  silc_hash_make(hash, buf->data, buf->len, hashd);
+  key->receive_hmac_key = silc_calloc(req_hmac_key_len, sizeof(unsigned char));
+  memcpy(key->receive_hmac_key, hashd, req_hmac_key_len);
   key->hmac_key_len = req_hmac_key_len;
+  memset(hashd, 0, sizeof(hashd));
 
+  silc_buffer_clear(buf);
   silc_buffer_free(buf);
 
   return SILC_SKE_STATUS_OK;
@@ -1768,21 +1945,22 @@ silc_ske_process_key_material_data(unsigned char *data,
    the actual keys to be used in the SILC. */
 
 SilcSKEStatus silc_ske_process_key_material(SilcSKE ske, 
-                                           uint32 req_iv_len,
-                                           uint32 req_enc_key_len,
-                                           uint32 req_hmac_key_len,
+                                           SilcUInt32 req_iv_len,
+                                           SilcUInt32 req_enc_key_len,
+                                           SilcUInt32 req_hmac_key_len,
                                            SilcSKEKeyMaterial *key)
 {
   SilcSKEStatus status;
   SilcBuffer buf;
   unsigned char *tmpbuf;
-  uint32 klen;
+  SilcUInt32 klen;
 
   /* Encode KEY to binary data */
   tmpbuf = silc_mp_mp2bin(ske->KEY, 0, &klen);
 
-  buf = silc_buffer_alloc(klen + ske->hash_len);
-  silc_buffer_pull_tail(buf, SILC_BUFFER_END(buf));
+  buf = silc_buffer_alloc_size(klen + ske->hash_len);
+  if (!buf)
+    return SILC_SKE_STATUS_OUT_OF_MEMORY;
   silc_buffer_format(buf,
                     SILC_STR_UI_XNSTRING(tmpbuf, klen),
                     SILC_STR_UI_XNSTRING(ske->hash, ske->hash_len),
@@ -1796,6 +1974,7 @@ SilcSKEStatus silc_ske_process_key_material(SilcSKE ske,
 
   memset(tmpbuf, 0, klen);
   silc_free(tmpbuf);
+  silc_buffer_clear(buf);
   silc_buffer_free(buf);
 
   return status;
@@ -1820,9 +1999,72 @@ void silc_ske_free_key_material(SilcSKEKeyMaterial *key)
     memset(key->receive_enc_key, 0, key->enc_key_len / 8);
     silc_free(key->receive_enc_key);
   }
-  if (key->hmac_key) {
-    memset(key->hmac_key, 0, key->hmac_key_len);
-    silc_free(key->hmac_key);
+  if (key->send_hmac_key) {
+    memset(key->send_hmac_key, 0, key->hmac_key_len);
+    silc_free(key->send_hmac_key);
+  }
+  if (key->receive_hmac_key) {
+    memset(key->receive_hmac_key, 0, key->hmac_key_len);
+    silc_free(key->receive_hmac_key);
   }
   silc_free(key);
 }
+
+const char *silc_ske_status_string[] = 
+{
+  /* Official */
+  "Ok",
+  "Unkown error occurred",
+  "Bad payload in packet",
+  "Unsupported group",
+  "Unsupported cipher",
+  "Unsupported PKCS",
+  "Unsupported hash function",
+  "Unsupported HMAC",
+  "Unsupported public key (or certificate)",
+  "Incorrect signature",
+  "Bad or unsupported version",
+  "Invalid cookie",
+
+  /* Other errors */
+  "Pending",
+  "Remote did not provide public key",
+  "Key exchange protocol is not active",
+  "Bad reserved field in packet",
+  "Bad payload length in packet",
+  "Error computing signature",
+  "System out of memory",
+
+  NULL
+};
+
+/* Maps status to readable string and returns the string. If string is not
+   found and empty character string ("") is returned. */
+
+const char *silc_ske_map_status(SilcSKEStatus status)
+{
+  int i;
+
+  for (i = 0; silc_ske_status_string[i]; i++)
+    if (status == i)
+      return silc_ske_status_string[i];
+
+  return "";
+}
+
+/* Parses remote host's version string. */
+
+bool silc_ske_parse_version(SilcSKE ske, 
+                           SilcUInt32 *protocol_version,
+                           char **protocol_version_string,
+                           SilcUInt32 *software_version, 
+                           char **software_version_string,
+                           char **vendor_version)
+{
+  return silc_parse_version_string(ske->remote_version,
+                                  protocol_version, 
+                                  protocol_version_string, 
+                                  software_version,
+                                  software_version_string,
+                                  vendor_version);
+}