+static bool metakey_ec_h(connection_t *c, const char *request) {
+ size_t siglen = ecdsa_size(&c->ecdsa);
+ char key[MAX_STRING_SIZE];
+ char sig[siglen];
+
+ logger(LOG_DEBUG, "Got ECDH metakey from %s", c->name);
+
+ if(sscanf(request, "%*d " MAX_STRING, key) != 1) {
+ logger(LOG_ERR, "Got bad %s from %s (%s)", "METAKEY", c->name, c->hostname);
+ return false;
+ }
+
+ int inlen = b64decode(key, key, sizeof key);
+
+ if(inlen != (ECDH_SIZE + siglen)) {
+ logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "wrong keylength");
+ return false;
+ }
+
+ if(!ecdsa_verify(&c->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE)) {
+ logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "invalid ECDSA signature");
+ return false;
+ }
+
+ char shared[ECDH_SHARED_SIZE];
+
+ if(!ecdh_compute_shared(&c->ecdh, key, shared))
+ return false;
+
+ /* Update our crypto end */
+
+ if(!cipher_open_by_name(&c->incipher, "aes-256-ofb"))
+ return false;
+ if(!digest_open_by_name(&c->indigest, "sha512", -1))
+ return false;
+ if(!cipher_open_by_name(&c->outcipher, "aes-256-ofb"))
+ return false;
+ if(!digest_open_by_name(&c->outdigest, "sha512", -1))
+ return false;
+
+ size_t mykeylen = cipher_keylength(&c->incipher);
+ size_t hiskeylen = cipher_keylength(&c->outcipher);
+
+ char *mykey;
+ char *hiskey;
+ char *seed;
+
+ if(strcmp(myself->name, c->name) < 0) {
+ mykey = key;
+ hiskey = key + mykeylen * 2;
+ xasprintf(&seed, "tinc TCP key expansion %s %s", myself->name, c->name);
+ } else {
+ mykey = key + hiskeylen * 2;
+ hiskey = key;
+ xasprintf(&seed, "tinc TCP key expansion %s %s", c->name, myself->name);
+ }
+
+ if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
+ return false;
+
+ free(seed);
+
+ cipher_set_key(&c->incipher, mykey, false);
+ digest_set_key(&c->indigest, mykey + mykeylen, mykeylen);
+
+ cipher_set_key(&c->outcipher, hiskey, true);
+ digest_set_key(&c->outdigest, hiskey + hiskeylen, hiskeylen);
+
+ c->status.decryptin = true;
+ c->status.encryptout = true;
+ c->allow_request = CHALLENGE;
+
+ return send_challenge(c);
+}
+