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Use ECDSA to sign ECDH key exchange for UDP session keys.

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The ECDSA public keys will also be included in the ANS_KEY requests,
but are only used when no ECDSA public key is known yet.
This commit is contained in:
Guus Sliepen 2011-07-16 20:21:44 +02:00
parent 03ac48ea19
commit cff27a258f
11 changed files with 116 additions and 17 deletions
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64
src/protocol_key.c
View file

@ -145,18 +145,31 @@ bool req_key_h(connection_t *c, char *request) {
}
bool send_ans_key_ecdh(node_t *to) {
char key[ECDH_SIZE * 2 + 1];
int siglen = ecdsa_size(&myself->connection->ecdsa);
char key[(ECDH_SIZE + siglen) * 2 + 1];
ecdh_generate_public(&to->ecdh, key);
if(!ecdh_generate_public(&to->ecdh, key))
return false;
b64encode(key, key, ECDH_SIZE);
if(!ecdsa_sign(&myself->connection->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE))
return false;
return send_request(to->nexthop->connection, "%d %s %s ECDH:%s %d %d %zu %d", ANS_KEY,
myself->name, to->name, key,
b64encode(key, key, ECDH_SIZE + siglen);
char *pubkey = ecdsa_get_base64_public_key(&myself->connection->ecdsa);
if(!pubkey)
return false;
int result = send_request(to->nexthop->connection, "%d %s %s ECDH:%s:%s %d %d %zu %d", ANS_KEY,
myself->name, to->name, key, pubkey,
cipher_get_nid(&myself->incipher),
digest_get_nid(&myself->indigest),
digest_length(&myself->indigest),
myself->incompression);
free(pubkey);
return result;
}
bool send_ans_key(node_t *to) {
@ -279,28 +292,53 @@ bool ans_key_h(connection_t *c, char *request) {
/* ECDH or old-style key exchange? */
if(experimental && !strncmp(key, "ECDH:", 5)) {
char *pubkey = strchr(key + 5, ':');
if(pubkey)
*pubkey++ = 0;
/* Check if we already have an ECDSA public key for this node.
* If not, use the one from the key exchange, and store it. */
if(!node_read_ecdsa_public_key(from)) {
if(!pubkey) {
logger(LOG_ERR, "No ECDSA public key known for %s (%s), cannot verify ECDH key exchange!", from->name, from->hostname);
return true;
}
if(!ecdsa_set_base64_public_key(&from->ecdsa, pubkey))
return true;
append_config_file(from->name, "ECDSAPublicKey", pubkey);
}
int siglen = ecdsa_size(&from->ecdsa);
int keylen = b64decode(key + 5, key + 5, sizeof key - 5);
if(keylen != ECDH_SIZE) {
logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
return false;
if(keylen != ECDH_SIZE + siglen) {
logger(LOG_ERR, "Node %s (%s) uses wrong keylength! %d != %d", from->name, from->hostname, keylen, ECDH_SIZE + siglen);
return true;
}
if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
logger(LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
return false;
return true;
}
if(!ecdsa_verify(&from->ecdsa, key + 5, ECDH_SIZE, key + 5 + ECDH_SIZE)) {
logger(LOG_ERR, "Possible intruder %s (%s): %s", from->name, from->hostname, "invalid ECDSA signature");
return true;
}
if(!from->ecdh) {
from->status.ecdh = true;
if(!send_ans_key(from))
return false;
return true;
}
char shared[ECDH_SHARED_SIZE * 2 + 1];
if(!ecdh_compute_shared(&from->ecdh, key + 5, shared))
return false;
return true;
/* Update our crypto end */
@ -322,7 +360,7 @@ bool ans_key_h(connection_t *c, char *request) {
}
if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
return false;
return true;
free(seed);
@ -349,7 +387,7 @@ bool ans_key_h(connection_t *c, char *request) {
if(keylen != cipher_keylength(&from->outcipher)) {
logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
return false;
return true;
}
/* Update our copy of the origin's packet key */