From 8132be8fbd6c45be309c63a117f418ad12ced094 Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Thu, 7 Jul 2011 22:30:55 +0200 Subject: [PATCH] Very primitive ECDSA signed ECDH key exchange for the meta protocol. Nonces and hash of the ID requests should be included in the seed for the PRF. --- src/protocol.h | 3 +- src/protocol_auth.c | 131 +++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 126 insertions(+), 8 deletions(-) diff --git a/src/protocol.h b/src/protocol.h index 212afaf3..191229ad 100644 --- a/src/protocol.h +++ b/src/protocol.h @@ -24,7 +24,7 @@ /* Protocol version. Different major versions are incompatible. */ #define PROT_MAJOR 17 -#define PROT_MINOR 1 +#define PROT_MINOR 2 /* Silly Windows */ @@ -83,6 +83,7 @@ extern bool seen_request(char *); extern bool send_id(struct connection_t *); extern bool send_metakey(struct connection_t *); +extern bool send_metakey_ec(struct connection_t *); extern bool send_challenge(struct connection_t *); extern bool send_chal_reply(struct connection_t *); extern bool send_ack(struct connection_t *); diff --git a/src/protocol_auth.c b/src/protocol_auth.c index d98e5c4b..d38814c6 100644 --- a/src/protocol_auth.c +++ b/src/protocol_auth.c @@ -25,13 +25,16 @@ #include "connection.h" #include "control.h" #include "control_common.h" +#include "cipher.h" #include "crypto.h" +#include "digest.h" #include "edge.h" #include "graph.h" #include "logger.h" #include "net.h" #include "netutl.h" #include "node.h" +#include "prf.h" #include "protocol.h" #include "rsa.h" #include "utils.h" @@ -109,13 +112,40 @@ bool id_h(connection_t *c, char *request) { } } - if(!read_rsa_public_key(c)) { + c->allow_request = METAKEY; + + if(c->protocol_minor >= 2) + return send_metakey_ec(c); + else + return send_metakey(c); +} + +bool send_metakey_ec(connection_t *c) { + if(!read_ecdsa_public_key(c)) return false; - } - c->allow_request = METAKEY; + logger(LOG_DEBUG, "Sending ECDH metakey to %s", c->name); + + size_t siglen = ecdsa_size(&myself->connection->ecdsa); - return send_metakey(c); + char key[ECDH_SIZE]; + char sig[siglen]; + + // TODO: include nonce? Use relevant parts of SSH or TLS protocol + + if(!ecdh_generate_public(&c->ecdh, key)) + return false; + + if(!ecdsa_sign(&myself->connection->ecdsa, key, ECDH_SIZE, sig)) + return false; + + char out[MAX_STRING_SIZE]; + + bin2hex(key, out, ECDH_SIZE); + bin2hex(sig, out + ECDH_SIZE * 2, siglen); + out[(ECDH_SIZE + siglen) * 2] = 0; + + bool result = send_request(c, "%d %s", METAKEY, out); } bool send_metakey(connection_t *c) { @@ -124,6 +154,9 @@ bool send_metakey(connection_t *c) { char enckey[len]; char hexkey[2 * len + 1]; + if(!read_rsa_public_key(c)) + return false; + if(!cipher_open_blowfish_ofb(&c->outcipher)) return false; @@ -182,7 +215,91 @@ bool send_metakey(connection_t *c) { return result; } +static bool metakey_ec_h(connection_t *c, const char *request) { + size_t siglen = ecdsa_size(&c->ecdsa); + char in[MAX_STRING_SIZE]; + char key[MAX_STRING_SIZE]; + char sig[siglen]; + + logger(LOG_DEBUG, "Got ECDH metakey from %s", c->name); + + if(sscanf(request, "%*d " MAX_STRING, in) != 1) { + logger(LOG_ERR, "Got bad %s from %s (%s)", "METAKEY", c->name, c->hostname); + return false; + } + + if(strlen(in) != (ECDH_SIZE + siglen) * 2) { + logger(LOG_ERR, "Possible intruder %s (%s): %s %d != %d", c->name, c->hostname, "wrong keylength", strlen(in) / 2, (ECDH_SIZE + siglen)); + return false; + } + + hex2bin(in, key, ECDH_SIZE); + hex2bin(in + ECDH_SIZE * 2, sig, siglen); + + if(!ecdsa_verify(&c->ecdsa, key, ECDH_SIZE, sig)) { + logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "invalid ECDSA signature"); + return false; + } + + char shared[ECDH_SHARED_SIZE * 2 + 1]; + + 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); + + bin2hex(shared, shared, ECDH_SHARED_SIZE); + shared[ECDH_SHARED_SIZE * 2] = 0; + logger(LOG_DEBUG, "Shared secret is %s", shared); + + cipher_set_key(&c->incipher, mykey, true); + digest_set_key(&c->indigest, mykey + mykeylen, mykeylen); + + cipher_set_key(&c->outcipher, hiskey, false); + digest_set_key(&c->outdigest, hiskey + hiskeylen, hiskeylen); + + c->status.decryptin = true; + c->status.encryptout = true; + c->allow_request = CHALLENGE; + + return send_challenge(c); +} + bool metakey_h(connection_t *c, char *request) { + if(c->protocol_minor >= 2) + return metakey_ec_h(c, request); + char hexkey[MAX_STRING_SIZE]; int cipher, digest, maclength, compression; size_t len = rsa_size(&myself->connection->rsa); @@ -238,7 +355,7 @@ bool metakey_h(connection_t *c, char *request) { } bool send_challenge(connection_t *c) { - size_t len = rsa_size(&c->rsa); + size_t len = c->protocol_minor >= 2 ? ECDH_SIZE : rsa_size(&c->rsa); char buffer[len * 2 + 1]; if(!c->hischallenge) @@ -260,7 +377,7 @@ bool send_challenge(connection_t *c) { bool challenge_h(connection_t *c, char *request) { char buffer[MAX_STRING_SIZE]; - size_t len = rsa_size(&myself->connection->rsa); + size_t len = c->protocol_minor >= 2 ? ECDH_SIZE : rsa_size(&myself->connection->rsa); size_t digestlen = digest_length(&c->indigest); char digest[digestlen]; @@ -318,7 +435,7 @@ bool chal_reply_h(connection_t *c, char *request) { /* Verify the hash */ - if(!digest_verify(&c->outdigest, c->hischallenge, rsa_size(&c->rsa), hishash)) { + if(!digest_verify(&c->outdigest, c->hischallenge, c->protocol_minor >= 2 ? ECDH_SIZE : rsa_size(&c->rsa), hishash)) { logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "wrong challenge reply"); return false; } -- 2.20.1