]> git.ipfire.org Git - thirdparty/strongswan.git/commitdiff
ike-init: Add support for multiple key exchanges
authorTobias Brunner <tobias@strongswan.org>
Thu, 31 Oct 2019 16:16:44 +0000 (17:16 +0100)
committerTobias Brunner <tobias@strongswan.org>
Wed, 7 Aug 2024 14:20:18 +0000 (16:20 +0200)
Initially, this is handled with a key derivation for each
IKE_INTERMEDIATE exchange.  When rekeying, the keys are derived only
once all IKE_FOLLOWUP_KE exchanges are done.

src/libcharon/sa/ikev2/tasks/ike_init.c

index 8ace416094c389c3ce3e1d52cd868da7f222a746..4eda3a0620c76299fa0e663f22b4392aeaaf23c0 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008-2019 Tobias Brunner
+ * Copyright (C) 2008-2020 Tobias Brunner
  * Copyright (C) 2005-2008 Martin Willi
  * Copyright (C) 2005 Jan Hutter
  *
 #include <encoding/payloads/ke_payload.h>
 #include <encoding/payloads/nonce_payload.h>
 
-/** maximum retries to do with cookies/other dh groups */
+/** maximum retries to do with cookies/other ke methods */
 #define MAX_RETRIES 5
 
+/** maximum number of key exchanges (including the initial one) */
+#define MAX_KEY_EXCHANGES (ADDITIONAL_KEY_EXCHANGE_7 - \
+                                                  ADDITIONAL_KEY_EXCHANGE_1 + 2)
+
 typedef struct private_ike_init_t private_ike_init_t;
 
 /**
@@ -56,29 +60,39 @@ struct private_ike_init_t {
        bool initiator;
 
        /**
-        * Whether the key exchange is done
+        * Key exchanges to perform
+        */
+       struct {
+               transform_type_t type;
+               key_exchange_method_t method;
+               bool done;
+               bool derived;
+       } key_exchanges[MAX_KEY_EXCHANGES];
+
+       /**
+        * Current key exchange
         */
-       bool ke_done;
+       int ke_index;
 
        /**
-        * Whether keys have already been derived
+        * Key exchange method from the parsed or sent KE payload
         */
-       bool ke_derived;
+       key_exchange_method_t ke_method;
 
        /**
-        * diffie hellman group to use
+        * Current key exchange object
         */
-       key_exchange_method_t dh_group;
+       key_exchange_t *ke;
 
        /**
-        * diffie hellman key exchange
+        * All key exchanges performed during rekeying (key_exchange_t)
         */
-       key_exchange_t *dh;
+       array_t *kes;
 
        /**
-        * Applying DH public value failed?
+        * Applying KE public key failed?
         */
-       bool dh_failed;
+       bool ke_failed;
 
        /**
         * Keymat derivation (from IKE_SA)
@@ -86,17 +100,17 @@ struct private_ike_init_t {
        keymat_v2_t *keymat;
 
        /**
-        * nonce chosen by us
+        * Nonce chosen by us
         */
        chunk_t my_nonce;
 
        /**
-        * nonce chosen by peer
+        * Nonce chosen by peer
         */
        chunk_t other_nonce;
 
        /**
-        * nonce generator
+        * Nonce generator
         */
        nonce_gen_t *nonceg;
 
@@ -106,17 +120,17 @@ struct private_ike_init_t {
        proposal_t *proposal;
 
        /**
-        * Old IKE_SA which gets rekeyed
+        * Old IKE_SA that gets rekeyed
         */
        ike_sa_t *old_sa;
 
        /**
-        * cookie received from responder
+        * Cookie received from responder
         */
        chunk_t cookie;
 
        /**
-        * retries done so far after failure (cookie or bad dh group)
+        * Retries done so far after failure (cookie or bad KE method)
         */
        u_int retry;
 
@@ -131,6 +145,15 @@ struct private_ike_init_t {
        bool follow_redirects;
 };
 
+/**
+ * Returns the exchange type for additional exchanges when using multiple key
+ * exchanges, depending on whether this happens initially or during a rekeying
+ */
+static exchange_type_t exchange_type_multi_ke(private_ike_init_t *this)
+{
+       return this->old_sa ? IKE_FOLLOWUP_KE : IKE_INTERMEDIATE;
+}
+
 /**
  * Allocate our own nonce value
  */
@@ -320,7 +343,7 @@ static bool build_payloads(private_ike_init_t *this, message_t *message)
        sa_payload_t *sa_payload;
        ke_payload_t *ke_payload;
        nonce_payload_t *nonce_payload;
-       linked_list_t *proposal_list, *other_dh_groups;
+       linked_list_t *proposal_list, *other_ke_methods;
        ike_sa_id_t *id;
        proposal_t *proposal;
        enumerator_t *enumerator;
@@ -333,7 +356,7 @@ static bool build_payloads(private_ike_init_t *this, message_t *message)
        if (this->initiator)
        {
                proposal_list = ike_cfg->get_proposals(ike_cfg);
-               other_dh_groups = linked_list_create();
+               other_ke_methods = linked_list_create();
                enumerator = proposal_list->create_enumerator(proposal_list);
                while (enumerator->enumerate(enumerator, (void**)&proposal))
                {
@@ -342,23 +365,23 @@ static bool build_payloads(private_ike_init_t *this, message_t *message)
                        {
                                proposal->set_spi(proposal, id->get_initiator_spi(id));
                        }
-                       /* move the selected DH group to the front of the proposal */
+                       /* move the selected KE method to the front of the proposal */
                        if (!proposal->promote_transform(proposal, KEY_EXCHANGE_METHOD,
-                                                                                        this->dh_group))
+                                                                                        this->ke_method))
                        {       /* the proposal does not include the group, move to the back */
                                proposal_list->remove_at(proposal_list, enumerator);
-                               other_dh_groups->insert_last(other_dh_groups, proposal);
+                               other_ke_methods->insert_last(other_ke_methods, proposal);
                        }
                }
                enumerator->destroy(enumerator);
                /* add proposals that don't contain the selected group */
-               enumerator = other_dh_groups->create_enumerator(other_dh_groups);
+               enumerator = other_ke_methods->create_enumerator(other_ke_methods);
                while (enumerator->enumerate(enumerator, (void**)&proposal))
                {       /* no need to remove from the list as we destroy it anyway*/
                        proposal_list->insert_last(proposal_list, proposal);
                }
                enumerator->destroy(enumerator);
-               other_dh_groups->destroy(other_dh_groups);
+               other_ke_methods->destroy(other_ke_methods);
 
                sa_payload = sa_payload_create_from_proposals_v2(proposal_list);
                proposal_list->destroy_offset(proposal_list, offsetof(proposal_t, destroy));
@@ -375,25 +398,17 @@ static bool build_payloads(private_ike_init_t *this, message_t *message)
        message->add_payload(message, (payload_t*)sa_payload);
 
        ke_payload = ke_payload_create_from_key_exchange(PLV2_KEY_EXCHANGE,
-                                                                                                        this->dh);
+                                                                                                        this->ke);
        if (!ke_payload)
        {
                DBG1(DBG_IKE, "creating KE payload failed");
                return FALSE;
        }
+       message->add_payload(message, (payload_t*)ke_payload);
+
        nonce_payload = nonce_payload_create(PLV2_NONCE);
        nonce_payload->set_nonce(nonce_payload, this->my_nonce);
-
-       if (this->old_sa)
-       {       /* payload order differs if we are rekeying */
-               message->add_payload(message, (payload_t*)nonce_payload);
-               message->add_payload(message, (payload_t*)ke_payload);
-       }
-       else
-       {
-               message->add_payload(message, (payload_t*)ke_payload);
-               message->add_payload(message, (payload_t*)nonce_payload);
-       }
+       message->add_payload(message, (payload_t*)nonce_payload);
 
        /* negotiate fragmentation if we are not rekeying */
        if (!this->old_sa &&
@@ -523,6 +538,106 @@ static void process_sa_payload(private_ike_init_t *this, message_t *message,
                                                                  offsetof(proposal_t, destroy));
 }
 
+/**
+ * Collect all key exchanges from the proposal
+ */
+static void determine_key_exchanges(private_ike_init_t *this)
+{
+       transform_type_t t = KEY_EXCHANGE_METHOD;
+       uint16_t alg;
+       int i = 1;
+
+       this->proposal->get_algorithm(this->proposal, t, &alg, NULL);
+       this->key_exchanges[0].type = t;
+       this->key_exchanges[0].method = alg;
+
+       for (t = ADDITIONAL_KEY_EXCHANGE_1; t <= ADDITIONAL_KEY_EXCHANGE_7; t++)
+       {
+               if (this->proposal->get_algorithm(this->proposal, t, &alg, NULL))
+               {
+                       this->key_exchanges[i].type = t;
+                       this->key_exchanges[i].method = alg;
+                       i++;
+               }
+       }
+}
+
+/**
+ * Check if additional key exchanges are required
+ */
+static bool additional_key_exchange_required(private_ike_init_t *this)
+{
+       int i;
+
+       for (i = this->ke_index; i < MAX_KEY_EXCHANGES; i++)
+       {
+               if (this->key_exchanges[i].type && !this->key_exchanges[i].done)
+               {
+                       return TRUE;
+               }
+       }
+       return FALSE;
+}
+
+/**
+ * Clear data on key exchanges
+ */
+static void clear_key_exchanges(private_ike_init_t *this)
+{
+       int i;
+
+       for (i = 0; i < MAX_KEY_EXCHANGES; i++)
+       {
+               this->key_exchanges[i].type = 0;
+               this->key_exchanges[i].method = 0;
+               this->key_exchanges[i].done = FALSE;
+       }
+       this->ke_index = 0;
+
+       array_destroy_offset(this->kes, offsetof(key_exchange_t, destroy));
+       this->kes = NULL;
+}
+
+/**
+ * Process a KE payload
+ */
+static void process_ke_payload(private_ike_init_t *this, ke_payload_t *ke)
+{
+       key_exchange_method_t method = this->key_exchanges[this->ke_index].method;
+       key_exchange_method_t received = ke->get_key_exchange_method(ke);
+
+       if (method != received)
+       {
+               DBG1(DBG_IKE, "key exchange method in received payload %N doesn't "
+                        "match negotiated %N", key_exchange_method_names, received,
+                        key_exchange_method_names, method);
+               this->ke_failed = TRUE;
+               return;
+       }
+
+       if (!this->initiator)
+       {
+               DESTROY_IF(this->ke);
+               this->ke = this->keymat->keymat.create_ke(&this->keymat->keymat,
+                                                                                                 method);
+               if (!this->ke)
+               {
+                       DBG1(DBG_IKE, "negotiated key exchange method %N not supported",
+                                key_exchange_method_names, method);
+               }
+       }
+       else if (this->ke)
+       {
+               this->ke_failed = this->ke->get_method(this->ke) != received;
+       }
+
+       if (this->ke && !this->ke_failed)
+       {
+               this->ke_failed = !this->ke->set_public_key(this->ke,
+                                                                                               ke->get_key_exchange_data(ke));
+       }
+}
+
 /**
  * Read payloads from message
  */
@@ -531,7 +646,7 @@ static void process_payloads(private_ike_init_t *this, message_t *message)
        enumerator_t *enumerator;
        payload_t *payload;
        ike_sa_id_t *id;
-       ke_payload_t *ke_payload = NULL;
+       ke_payload_t *ke_pld = NULL;
 
        enumerator = message->create_payload_enumerator(message);
        while (enumerator->enumerate(enumerator, &payload))
@@ -545,9 +660,9 @@ static void process_payloads(private_ike_init_t *this, message_t *message)
                        }
                        case PLV2_KEY_EXCHANGE:
                        {
-                               ke_payload = (ke_payload_t*)payload;
+                               ke_pld = (ke_payload_t*)payload;
 
-                               this->dh_group = ke_payload->get_key_exchange_method(ke_payload);
+                               this->ke_method = ke_pld->get_key_exchange_method(ke_pld);
                                break;
                        }
                        case PLV2_NONCE:
@@ -641,29 +756,57 @@ static void process_payloads(private_ike_init_t *this, message_t *message)
                                                                          this->proposal->get_spi(this->proposal));
                        }
                }
-       }
 
-       if (ke_payload && this->proposal &&
-               this->proposal->has_transform(this->proposal, KEY_EXCHANGE_METHOD,
-                                                                         this->dh_group))
-       {
-               if (!this->initiator)
-               {
-                       this->dh = this->keymat->keymat.create_ke(
-                                                               &this->keymat->keymat, this->dh_group);
-               }
-               else if (this->dh)
+               determine_key_exchanges(this);
+               if (ke_pld)
                {
-                       this->dh_failed = this->dh->get_method(this->dh) != this->dh_group;
-               }
-               if (this->dh && !this->dh_failed)
-               {
-                       this->dh_failed = !this->dh->set_public_key(this->dh,
-                                                               ke_payload->get_key_exchange_data(ke_payload));
+                       process_ke_payload(this, ke_pld);
                }
        }
 }
 
+/**
+ * Build payloads in additional exchanges when using multiple key exchanges
+ */
+static bool build_payloads_multi_ke(private_ike_init_t *this,
+                                                                       message_t *message)
+{
+       ke_payload_t *ke;
+
+       ke = ke_payload_create_from_key_exchange(PLV2_KEY_EXCHANGE, this->ke);
+       if (!ke)
+       {
+               DBG1(DBG_IKE, "creating KE payload failed");
+               return FALSE;
+       }
+       message->add_payload(message, (payload_t*)ke);
+       return TRUE;
+}
+
+METHOD(task_t, build_i_multi_ke, status_t,
+       private_ike_init_t *this, message_t *message)
+{
+       key_exchange_method_t method;
+
+       message->set_exchange_type(message, exchange_type_multi_ke(this));
+
+       DESTROY_IF(this->ke);
+       method = this->key_exchanges[this->ke_index].method;
+       this->ke = this->keymat->keymat.create_ke(&this->keymat->keymat,
+                                                                                         method);
+       if (!this->ke)
+       {
+               DBG1(DBG_IKE, "negotiated key exchange method %N not supported",
+                        key_exchange_method_names, method);
+               return FAILED;
+       }
+       if (!build_payloads_multi_ke(this, message))
+       {
+               return FAILED;
+       }
+       return NEED_MORE;
+}
+
 METHOD(task_t, build_i, status_t,
        private_ike_init_t *this, message_t *message)
 {
@@ -684,49 +827,50 @@ METHOD(task_t, build_i, status_t,
        }
 
        /* if we are retrying after an INVALID_KE_PAYLOAD we already have one */
-       if (!this->dh)
+       if (!this->ke)
        {
-               if (this->old_sa && lib->settings->get_bool(lib->settings,
+               if (this->old_sa &&
+                       lib->settings->get_bool(lib->settings,
                                                                "%s.prefer_previous_dh_group", TRUE, lib->ns))
-               {       /* reuse the DH group we used for the old IKE_SA when rekeying */
+               {       /* reuse the KE method we used for the old IKE_SA when rekeying */
                        proposal_t *proposal;
-                       uint16_t dh_group;
+                       uint16_t ke_method;
 
                        proposal = this->old_sa->get_proposal(this->old_sa);
                        if (proposal->get_algorithm(proposal, KEY_EXCHANGE_METHOD,
-                                                                               &dh_group, NULL))
+                                                                               &ke_method, NULL))
                        {
-                               this->dh_group = dh_group;
+                               this->ke_method = ke_method;
                        }
                        else
                        {       /* this shouldn't happen, but let's be safe */
-                               this->dh_group = ike_cfg->get_algorithm(ike_cfg,
-                                                                                                               KEY_EXCHANGE_METHOD);
+                               this->ke_method = ike_cfg->get_algorithm(ike_cfg,
+                                                                                                                KEY_EXCHANGE_METHOD);
                        }
                }
                else
                {
-                       this->dh_group = ike_cfg->get_algorithm(ike_cfg,
-                                                                                                       KEY_EXCHANGE_METHOD);
+                       this->ke_method = ike_cfg->get_algorithm(ike_cfg,
+                                                                                                        KEY_EXCHANGE_METHOD);
                }
-               this->dh = this->keymat->keymat.create_ke(&this->keymat->keymat,
-                                                                                                 this->dh_group);
-               if (!this->dh)
+               this->ke = this->keymat->keymat.create_ke(&this->keymat->keymat,
+                                                                                                 this->ke_method);
+               if (!this->ke)
                {
-                       DBG1(DBG_IKE, "configured DH group %N not supported",
-                               key_exchange_method_names, this->dh_group);
+                       DBG1(DBG_IKE, "configured key exchange method %N not supported",
+                                key_exchange_method_names, this->ke_method);
                        return FAILED;
                }
        }
-       else if (this->dh->get_method(this->dh) != this->dh_group)
-       {       /* reset DH instance if group changed (INVALID_KE_PAYLOAD) */
-               this->dh->destroy(this->dh);
-               this->dh = this->keymat->keymat.create_ke(&this->keymat->keymat,
-                                                                                                 this->dh_group);
-               if (!this->dh)
+       else if (this->ke->get_method(this->ke) != this->ke_method)
+       {       /* reset KE instance if method changed (INVALID_KE_PAYLOAD) */
+               this->ke->destroy(this->ke);
+               this->ke = this->keymat->keymat.create_ke(&this->keymat->keymat,
+                                                                                                 this->ke_method);
+               if (!this->ke)
                {
-                       DBG1(DBG_IKE, "requested DH group %N not supported",
-                                key_exchange_method_names, this->dh_group);
+                       DBG1(DBG_IKE, "requested key exchange method %N not supported",
+                                key_exchange_method_names, this->ke_method);
                        return FAILED;
                }
        }
@@ -763,6 +907,35 @@ METHOD(task_t, build_i, status_t,
        return NEED_MORE;
 }
 
+/**
+ * Process payloads in additional exchanges when using multiple key exchanges
+ */
+static void process_payloads_multi_ke(private_ike_init_t *this,
+                                                                         message_t *message)
+{
+       ke_payload_t *ke;
+
+       ke = (ke_payload_t*)message->get_payload(message, PLV2_KEY_EXCHANGE);
+       if (ke)
+       {
+               process_ke_payload(this, ke);
+       }
+       else
+       {
+               DBG1(DBG_IKE, "KE payload missing in message");
+       }
+}
+
+METHOD(task_t, process_r_multi_ke, status_t,
+       private_ike_init_t *this, message_t *message)
+{
+       if (message->get_exchange_type(message) == exchange_type_multi_ke(this))
+       {
+               process_payloads_multi_ke(this, message);
+       }
+       return NEED_MORE;
+}
+
 METHOD(task_t, process_r,  status_t,
        private_ike_init_t *this, message_t *message)
 {
@@ -798,30 +971,46 @@ METHOD(task_t, process_r,  status_t,
 static bool derive_keys_internal(private_ike_init_t *this, chunk_t nonce_i,
                                                                 chunk_t nonce_r)
 {
+       ike_sa_t *old_sa;
        keymat_v2_t *old_keymat;
        pseudo_random_function_t prf_alg = PRF_UNDEFINED;
        chunk_t skd = chunk_empty;
        ike_sa_id_t *id;
        array_t *kes = NULL;
+       bool success;
 
-       id = this->ike_sa->get_id(this->ike_sa);
        if (this->old_sa)
        {
-               /* rekeying: Include old SKd, use old PRF, apply SPI */
-               old_keymat = (keymat_v2_t*)this->old_sa->get_keymat(this->old_sa);
-               prf_alg = old_keymat->get_skd(old_keymat, &skd);
+               if (additional_key_exchange_required(this))
+               {       /* when rekeying, we only derive keys once all exchanges are done */
+                       return FALSE;
+               }
+               old_sa = this->old_sa;
+               kes = this->kes;
        }
-       array_insert_create(&kes, ARRAY_HEAD, this->dh);
-       if (!this->keymat->derive_ike_keys(this->keymat, this->proposal, kes,
-                                                                          nonce_i, nonce_r, id, prf_alg, skd))
+       else
+       {       /* key derivation for additional key exchanges is like rekeying, so pass
+                * our own SA as old SA to get SK_d */
+               old_sa = this->ike_sa;
+               array_insert_create(&kes, ARRAY_HEAD, this->ke);
+       }
+
+       id = this->ike_sa->get_id(this->ike_sa);
+       old_keymat = (keymat_v2_t*)old_sa->get_keymat(old_sa);
+       prf_alg = old_keymat->get_skd(old_keymat, &skd);
+       success = this->keymat->derive_ike_keys(this->keymat, this->proposal, kes,
+                                                                                       nonce_i, nonce_r, id, prf_alg, skd);
+       if (success)
+       {
+               charon->bus->ike_keys(charon->bus, this->ike_sa, kes, chunk_empty,
+                                                         nonce_i, nonce_r, skd.len ? old_sa : NULL, NULL,
+                                                         AUTH_NONE);
+       }
+       if (kes != this->kes)
        {
                array_destroy(kes);
-               return FALSE;
        }
-       charon->bus->ike_keys(charon->bus, this->ike_sa, kes, chunk_empty,
-                                                 nonce_i, nonce_r, this->old_sa, NULL, AUTH_NONE);
-       array_destroy(kes);
-       return TRUE;
+       return success;
 }
 
 METHOD(ike_init_t, derive_keys, status_t,
@@ -829,7 +1018,7 @@ METHOD(ike_init_t, derive_keys, status_t,
 {
        bool success;
 
-       if (!this->ke_done || this->ke_derived)
+       if (!this->ke_index || this->key_exchanges[this->ke_index-1].derived)
        {
                return NEED_MORE;
        }
@@ -843,14 +1032,64 @@ METHOD(ike_init_t, derive_keys, status_t,
                success = derive_keys_internal(this, this->other_nonce, this->my_nonce);
        }
 
-       this->ke_derived = TRUE;
+       this->key_exchanges[this->ke_index-1].derived = TRUE;
 
        if (!success)
        {
                DBG1(DBG_IKE, "key derivation failed");
                return FAILED;
        }
-       return SUCCESS;
+       return additional_key_exchange_required(this) ? NEED_MORE : SUCCESS;
+}
+
+/**
+ * Called when a key exchange is done
+ */
+static status_t key_exchange_done(private_ike_init_t *this)
+{
+       if (this->old_sa)
+       {
+               /* during rekeying, we store all the key exchanges performed */
+               array_insert_create(&this->kes, ARRAY_TAIL, this->ke);
+               this->ke = NULL;
+       }
+
+       this->key_exchanges[this->ke_index++].done = TRUE;
+
+       return additional_key_exchange_required(this) ? NEED_MORE : SUCCESS;
+}
+
+METHOD(task_t, build_r_multi_ke, status_t,
+       private_ike_init_t *this, message_t *message)
+{
+       if (!this->ke)
+       {
+               message->add_notify(message, FALSE, INVALID_SYNTAX, chunk_empty);
+               return FAILED;
+       }
+       if (this->ke_failed)
+       {
+               message->add_notify(message, FALSE, NO_PROPOSAL_CHOSEN, chunk_empty);
+               return FAILED;
+       }
+       if (!build_payloads_multi_ke(this, message))
+       {
+               return FAILED;
+       }
+
+       if (key_exchange_done(this) != NEED_MORE && this->old_sa)
+       {
+               /* during rekeying, we derive keys once all exchanges are done */
+               if (derive_keys(this) != SUCCESS)
+               {
+                       message->add_notify(message, FALSE, NO_PROPOSAL_CHOSEN, chunk_empty);
+                       return FAILED;
+               }
+               return SUCCESS;
+       }
+       /* when not rekeying, we derive keys after each IKE_INTERMEDIATE but only
+        * once we receive the next message, so IntAuth is based on the right keys */
+       return NEED_MORE;
 }
 
 METHOD(task_t, build_r, status_t,
@@ -883,19 +1122,20 @@ METHOD(task_t, build_r, status_t,
                return FAILED;
        }
 
-       if (this->dh == NULL ||
+       if (!this->ke ||
                !this->proposal->has_transform(this->proposal, KEY_EXCHANGE_METHOD,
-                                                                          this->dh_group))
+                                                                          this->ke_method))
        {
                uint16_t group;
 
                if (this->proposal->get_algorithm(this->proposal, KEY_EXCHANGE_METHOD,
-                                                                                 &group, NULL))
+                                                                                 &group, NULL) &&
+                       this->ke_method != group)
                {
-                       DBG1(DBG_IKE, "DH group %N unacceptable, requesting %N",
-                                key_exchange_method_names, this->dh_group,
+                       DBG1(DBG_IKE, "key exchange method %N unacceptable, requesting %N",
+                                key_exchange_method_names, this->ke_method,
                                 key_exchange_method_names, group);
-                       this->dh_group = group;
+                       this->ke_method = group;
                        group = htons(group);
                        message->add_notify(message, FALSE, INVALID_KE_PAYLOAD,
                                                                chunk_from_thing(group));
@@ -908,9 +1148,9 @@ METHOD(task_t, build_r, status_t,
                return FAILED;
        }
 
-       if (this->dh_failed)
+       if (this->ke_failed)
        {
-               DBG1(DBG_IKE, "applying DH public value failed");
+               DBG1(DBG_IKE, "applying KE public value failed");
                message->add_notify(message, TRUE, NO_PROPOSAL_CHOSEN, chunk_empty);
                return FAILED;
        }
@@ -920,9 +1160,14 @@ METHOD(task_t, build_r, status_t,
                message->add_notify(message, TRUE, NO_PROPOSAL_CHOSEN, chunk_empty);
                return FAILED;
        }
-       this->ke_done = TRUE;
 
-       if (this->old_sa)
+       if (key_exchange_done(this) == NEED_MORE)
+       {
+               /* use other exchange type for additional key exchanges */
+               this->public.task.build = _build_r_multi_ke;
+               this->public.task.process = _process_r_multi_ke;
+       }
+       else if (this->old_sa)
        {
                /* during rekeying, we derive keys here directly */
                if (derive_keys(this) != SUCCESS)
@@ -1019,6 +1264,26 @@ METHOD(task_t, pre_process_i, status_t,
        return SUCCESS;
 }
 
+METHOD(task_t, process_i_multi_ke, status_t,
+       private_ike_init_t *this, message_t *message)
+{
+       process_payloads_multi_ke(this, message);
+
+       if (this->ke_failed)
+       {
+               return FAILED;
+       }
+
+       if (key_exchange_done(this) != NEED_MORE && this->old_sa)
+       {
+               /* during rekeying, we derive keys once all exchanges are done */
+               return derive_keys(this);
+       }
+       /* when not rekeying, we derive keys after each IKE_INTERMEDIATE but only
+        * once we send the next message, so IntAuth is based on the right keys */
+       return NEED_MORE;
+}
+
 METHOD(task_t, process_i, status_t,
        private_ike_init_t *this, message_t *message)
 {
@@ -1039,16 +1304,16 @@ METHOD(task_t, process_i, status_t,
                                case INVALID_KE_PAYLOAD:
                                {
                                        chunk_t data;
-                                       key_exchange_method_t bad_group DBG_UNUSED;
+                                       key_exchange_method_t bad_method DBG_UNUSED;
 
-                                       bad_group = this->dh_group;
+                                       bad_method = this->ke_method;
                                        data = notify->get_notification_data(notify);
-                                       this->dh_group = ntohs(*((uint16_t*)data.ptr));
-                                       DBG1(DBG_IKE, "peer didn't accept DH group %N, "
+                                       this->ke_method = ntohs(*((uint16_t*)data.ptr));
+                                       DBG1(DBG_IKE, "peer didn't accept key exchange method %N, "
                                                 "it requested %N", key_exchange_method_names,
-                                                bad_group, key_exchange_method_names, this->dh_group);
+                                                bad_method, key_exchange_method_names, this->ke_method);
 
-                                       if (this->old_sa == NULL)
+                                       if (!this->old_sa)
                                        {       /* reset the IKE_SA if we are not rekeying */
                                                this->ike_sa->reset(this->ike_sa, FALSE);
                                        }
@@ -1125,29 +1390,33 @@ METHOD(task_t, process_i, status_t,
        process_payloads(this, message);
 
        /* check if we have everything */
-       if (this->proposal == NULL ||
+       if (!this->proposal ||
                this->other_nonce.len == 0 || this->my_nonce.len == 0)
        {
-               DBG1(DBG_IKE, "peers proposal selection invalid");
+               DBG1(DBG_IKE, "peer's proposal selection invalid");
                return FAILED;
        }
 
-       if (this->dh == NULL ||
-               !this->proposal->has_transform(this->proposal, KEY_EXCHANGE_METHOD,
-                                                                          this->dh_group))
+       if (!this->proposal->has_transform(this->proposal, KEY_EXCHANGE_METHOD,
+                                                                          this->ke_method))
        {
-               DBG1(DBG_IKE, "peer DH group selection invalid");
+               DBG1(DBG_IKE, "peer's key exchange method selection invalid");
                return FAILED;
        }
 
-       if (this->dh_failed)
+       if (this->ke_failed)
        {
-               DBG1(DBG_IKE, "applying DH public value failed");
+               DBG1(DBG_IKE, "applying key exchange public value failed");
                return FAILED;
        }
-       this->ke_done = TRUE;
 
-       if (this->old_sa)
+       if (key_exchange_done(this) == NEED_MORE)
+       {
+               /* use other exchange type for additional key exchanges */
+               this->public.task.build = _build_i_multi_ke;
+               this->public.task.process = _process_i_multi_ke;
+       }
+       else if (this->old_sa)
        {
                /* during rekeying, we derive keys here directly */
                return derive_keys(this);
@@ -1167,24 +1436,26 @@ METHOD(task_t, migrate, void,
 {
        DESTROY_IF(this->proposal);
        chunk_free(&this->other_nonce);
-       this->ke_done = FALSE;
-       this->ke_derived = FALSE;
+       clear_key_exchanges(this);
 
        this->ike_sa = ike_sa;
        this->keymat = (keymat_v2_t*)ike_sa->get_keymat(ike_sa);
        this->proposal = NULL;
-       this->dh_failed = FALSE;
+       this->ke_failed = FALSE;
+       this->public.task.build = _build_i;
+       this->public.task.process = _process_i;
 }
 
 METHOD(task_t, destroy, void,
        private_ike_init_t *this)
 {
-       DESTROY_IF(this->dh);
+       DESTROY_IF(this->ke);
        DESTROY_IF(this->proposal);
        DESTROY_IF(this->nonceg);
        chunk_free(&this->my_nonce);
        chunk_free(&this->other_nonce);
        chunk_free(&this->cookie);
+       clear_key_exchanges(this);
        free(this);
 }
 
@@ -1221,7 +1492,7 @@ ike_init_t *ike_init_create(ike_sa_t *ike_sa, bool initiator, ike_sa_t *old_sa)
                },
                .ike_sa = ike_sa,
                .initiator = initiator,
-               .dh_group = KE_NONE,
+               .ke_method = KE_NONE,
                .keymat = (keymat_v2_t*)ike_sa->get_keymat(ike_sa),
                .old_sa = old_sa,
                .signature_authentication = lib->settings->get_bool(lib->settings,