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- /*
- protocol_auth.c -- handle the meta-protocol, authentication
- Copyright (C) 1999-2005 Ivo Timmermans,
- 2000-2016 Guus Sliepen <guus@tinc-vpn.org>
- 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.
- 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
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
- #include "system.h"
- #include <openssl/sha.h>
- #include <openssl/rand.h>
- #include <openssl/err.h>
- #include <openssl/evp.h>
- #include "avl_tree.h"
- #include "conf.h"
- #include "connection.h"
- #include "edge.h"
- #include "graph.h"
- #include "logger.h"
- #include "meta.h"
- #include "net.h"
- #include "netutl.h"
- #include "node.h"
- #include "protocol.h"
- #include "proxy.h"
- #include "utils.h"
- #include "xalloc.h"
- bool send_id(connection_t *c) {
- if(proxytype && c->outgoing && !c->status.proxy_passed) {
- return send_proxyrequest(c);
- }
- return send_request(c, "%d %s %d", ID, myself->connection->name,
- myself->connection->protocol_version);
- }
- bool id_h(connection_t *c) {
- char name[MAX_STRING_SIZE];
- if(sscanf(c->buffer, "%*d " MAX_STRING " %d", name, &c->protocol_version) != 2) {
- logger(LOG_ERR, "Got bad %s from %s (%s)", "ID", c->name,
- c->hostname);
- return false;
- }
- /* Check if identity is a valid name */
- if(!check_id(name)) {
- logger(LOG_ERR, "Got bad %s from %s (%s): %s", "ID", c->name,
- c->hostname, "invalid name");
- return false;
- }
- /* If this is an outgoing connection, make sure we are connected to the right host */
- if(c->outgoing) {
- if(strcmp(c->name, name)) {
- logger(LOG_ERR, "Peer %s is %s instead of %s", c->hostname, name,
- c->name);
- return false;
- }
- } else {
- if(c->name) {
- free(c->name);
- }
- c->name = xstrdup(name);
- }
- /* Check if version matches */
- if(c->protocol_version != myself->connection->protocol_version) {
- logger(LOG_ERR, "Peer %s (%s) uses incompatible version %d",
- c->name, c->hostname, c->protocol_version);
- return false;
- }
- if(bypass_security) {
- if(!c->config_tree) {
- init_configuration(&c->config_tree);
- }
- c->allow_request = ACK;
- return send_ack(c);
- }
- if(!c->config_tree) {
- init_configuration(&c->config_tree);
- if(!read_connection_config(c)) {
- logger(LOG_ERR, "Peer %s had unknown identity (%s)", c->hostname,
- c->name);
- return false;
- }
- }
- if(!read_rsa_public_key(c)) {
- return false;
- }
- c->allow_request = METAKEY;
- return send_metakey(c);
- }
- static uint64_t byte_budget(const EVP_CIPHER *cipher) {
- /* Hopefully some failsafe way to calculate the maximum amount of bytes to
- send/receive with a given cipher before we might run into birthday paradox
- attacks. Because we might use different modes, the block size of the mode
- might be 1 byte. In that case, use the IV length. Ensure the whole thing
- is limited to what can be represented with a 64 bits integer.
- */
- int ivlen = EVP_CIPHER_iv_length(cipher);
- int blklen = EVP_CIPHER_block_size(cipher);
- int len = blklen > 1 ? blklen : ivlen > 1 ? ivlen : 8;
- int bits = len * 4 - 1;
- return bits < 64 ? UINT64_C(1) << bits : UINT64_MAX;
- }
- bool send_metakey(connection_t *c) {
- bool x;
- int len = RSA_size(c->rsa_key);
- /* Allocate buffers for the meta key */
- char buffer[2 * len + 1];
- c->outkey = xrealloc(c->outkey, len);
- if(!c->outctx) {
- c->outctx = EVP_CIPHER_CTX_new();
- if(!c->outctx) {
- abort();
- }
- }
- /* Copy random data to the buffer */
- if(1 != RAND_bytes((unsigned char *)c->outkey, len)) {
- int err = ERR_get_error();
- logger(LOG_ERR, "Failed to generate meta key (%s)", ERR_error_string(err, NULL));
- return false;
- }
- /* The message we send must be smaller than the modulus of the RSA key.
- By definition, for a key of k bits, the following formula holds:
- 2^(k-1) <= modulus < 2^(k)
- Where ^ means "to the power of", not "xor".
- This means that to be sure, we must choose our message < 2^(k-1).
- This can be done by setting the most significant bit to zero.
- */
- c->outkey[0] &= 0x7F;
- ifdebug(SCARY_THINGS) {
- bin2hex(c->outkey, buffer, len);
- buffer[len * 2] = '\0';
- logger(LOG_DEBUG, "Generated random meta key (unencrypted): %s",
- buffer);
- }
- /* Encrypt the random data
- We do not use one of the PKCS padding schemes here.
- This is allowed, because we encrypt a totally random string
- with a length equal to that of the modulus of the RSA key.
- */
- if(RSA_public_encrypt(len, (unsigned char *)c->outkey, (unsigned char *)buffer, c->rsa_key, RSA_NO_PADDING) != len) {
- logger(LOG_ERR, "Error during encryption of meta key for %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- /* Convert the encrypted random data to a hexadecimal formatted string */
- bin2hex(buffer, buffer, len);
- buffer[len * 2] = '\0';
- /* Send the meta key */
- x = send_request(c, "%d %d %d %d %d %s", METAKEY,
- c->outcipher ? EVP_CIPHER_nid(c->outcipher) : 0,
- c->outdigest ? EVP_MD_type(c->outdigest) : 0, c->outmaclength,
- c->outcompression, buffer);
- /* Further outgoing requests are encrypted with the key we just generated */
- if(c->outcipher) {
- if(!EVP_EncryptInit(c->outctx, c->outcipher,
- (unsigned char *)c->outkey + len - EVP_CIPHER_key_length(c->outcipher),
- (unsigned char *)c->outkey + len - EVP_CIPHER_key_length(c->outcipher) -
- EVP_CIPHER_iv_length(c->outcipher))) {
- logger(LOG_ERR, "Error during initialisation of cipher for %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- c->outbudget = byte_budget(c->outcipher);
- c->status.encryptout = true;
- }
- return x;
- }
- bool metakey_h(connection_t *c) {
- char buffer[MAX_STRING_SIZE];
- int cipher, digest, maclength, compression;
- int len;
- if(sscanf(c->buffer, "%*d %d %d %d %d " MAX_STRING, &cipher, &digest, &maclength, &compression, buffer) != 5) {
- logger(LOG_ERR, "Got bad %s from %s (%s)", "METAKEY", c->name,
- c->hostname);
- return false;
- }
- len = RSA_size(myself->connection->rsa_key);
- /* Check if the length of the meta key is all right */
- if(strlen(buffer) != (size_t)len * 2) {
- logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "wrong keylength");
- return false;
- }
- /* Allocate buffers for the meta key */
- c->inkey = xrealloc(c->inkey, len);
- if(!c->inctx) {
- c->inctx = EVP_CIPHER_CTX_new();
- if(!c->inctx) {
- abort();
- }
- }
- /* Convert the challenge from hexadecimal back to binary */
- if(!hex2bin(buffer, buffer, len)) {
- logger(LOG_ERR, "Got bad %s from %s(%s): %s", "METAKEY", c->name, c->hostname, "invalid key");
- return false;
- }
- /* Decrypt the meta key */
- if(RSA_private_decrypt(len, (unsigned char *)buffer, (unsigned char *)c->inkey, myself->connection->rsa_key, RSA_NO_PADDING) != len) { /* See challenge() */
- logger(LOG_ERR, "Error during decryption of meta key for %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- ifdebug(SCARY_THINGS) {
- bin2hex(c->inkey, buffer, len);
- buffer[len * 2] = '\0';
- logger(LOG_DEBUG, "Received random meta key (unencrypted): %s", buffer);
- }
- /* All incoming requests will now be encrypted. */
- /* Check and lookup cipher and digest algorithms */
- if(cipher) {
- c->incipher = EVP_get_cipherbynid(cipher);
- if(!c->incipher) {
- logger(LOG_ERR, "%s (%s) uses unknown cipher!", c->name, c->hostname);
- return false;
- }
- if(!EVP_DecryptInit(c->inctx, c->incipher,
- (unsigned char *)c->inkey + len - EVP_CIPHER_key_length(c->incipher),
- (unsigned char *)c->inkey + len - EVP_CIPHER_key_length(c->incipher) -
- EVP_CIPHER_iv_length(c->incipher))) {
- logger(LOG_ERR, "Error during initialisation of cipher from %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- c->inbudget = byte_budget(c->incipher);
- c->status.decryptin = true;
- } else {
- c->incipher = NULL;
- }
- c->inmaclength = maclength;
- if(digest) {
- c->indigest = EVP_get_digestbynid(digest);
- if(!c->indigest) {
- logger(LOG_ERR, "Node %s (%s) uses unknown digest!", c->name, c->hostname);
- return false;
- }
- if(c->inmaclength > EVP_MD_size(c->indigest) || c->inmaclength < 0) {
- logger(LOG_ERR, "%s (%s) uses bogus MAC length!", c->name, c->hostname);
- return false;
- }
- } else {
- c->indigest = NULL;
- }
- c->incompression = compression;
- c->allow_request = CHALLENGE;
- return send_challenge(c);
- }
- bool send_challenge(connection_t *c) {
- /* CHECKME: what is most reasonable value for len? */
- int len = RSA_size(c->rsa_key);
- /* Allocate buffers for the challenge */
- char buffer[2 * len + 1];
- c->hischallenge = xrealloc(c->hischallenge, len);
- /* Copy random data to the buffer */
- if(1 != RAND_bytes((unsigned char *)c->hischallenge, len)) {
- int err = ERR_get_error();
- logger(LOG_ERR, "Failed to generate challenge (%s)", ERR_error_string(err, NULL));
- return false; // Do not send predictable challenges, let connection attempt fail.
- }
- /* Convert to hex */
- bin2hex(c->hischallenge, buffer, len);
- buffer[len * 2] = '\0';
- /* Send the challenge */
- return send_request(c, "%d %s", CHALLENGE, buffer);
- }
- bool challenge_h(connection_t *c) {
- char buffer[MAX_STRING_SIZE];
- int len;
- if(sscanf(c->buffer, "%*d " MAX_STRING, buffer) != 1) {
- logger(LOG_ERR, "Got bad %s from %s (%s)", "CHALLENGE", c->name,
- c->hostname);
- return false;
- }
- len = RSA_size(myself->connection->rsa_key);
- /* Check if the length of the challenge is all right */
- if(strlen(buffer) != (size_t)len * 2) {
- logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name,
- c->hostname, "wrong challenge length");
- return false;
- }
- /* Allocate buffers for the challenge */
- c->mychallenge = xrealloc(c->mychallenge, len);
- /* Convert the challenge from hexadecimal back to binary */
- if(!hex2bin(buffer, c->mychallenge, len)) {
- logger(LOG_ERR, "Got bad %s from %s(%s): %s", "CHALLENGE", c->name, c->hostname, "invalid challenge");
- return false;
- }
- c->allow_request = CHAL_REPLY;
- /* Rest is done by send_chal_reply() */
- return send_chal_reply(c);
- }
- bool send_chal_reply(connection_t *c) {
- char hash[EVP_MAX_MD_SIZE * 2 + 1];
- EVP_MD_CTX *ctx;
- /* Calculate the hash from the challenge we received */
- ctx = EVP_MD_CTX_create();
- if(!ctx) {
- abort();
- }
- if(!EVP_DigestInit(ctx, c->indigest)
- || !EVP_DigestUpdate(ctx, c->mychallenge, RSA_size(myself->connection->rsa_key))
- || !EVP_DigestFinal(ctx, (unsigned char *)hash, NULL)) {
- EVP_MD_CTX_destroy(ctx);
- logger(LOG_ERR, "Error during calculation of response for %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- EVP_MD_CTX_destroy(ctx);
- /* Convert the hash to a hexadecimal formatted string */
- bin2hex(hash, hash, EVP_MD_size(c->indigest));
- hash[EVP_MD_size(c->indigest) * 2] = '\0';
- /* Send the reply */
- return send_request(c, "%d %s", CHAL_REPLY, hash);
- }
- bool chal_reply_h(connection_t *c) {
- char hishash[MAX_STRING_SIZE];
- char myhash[EVP_MAX_MD_SIZE];
- EVP_MD_CTX *ctx;
- if(sscanf(c->buffer, "%*d " MAX_STRING, hishash) != 1) {
- logger(LOG_ERR, "Got bad %s from %s (%s)", "CHAL_REPLY", c->name,
- c->hostname);
- return false;
- }
- /* Check if the length of the hash is all right */
- if(strlen(hishash) != (size_t)EVP_MD_size(c->outdigest) * 2) {
- logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name,
- c->hostname, "wrong challenge reply length");
- return false;
- }
- /* Convert the hash to binary format */
- if(!hex2bin(hishash, hishash, EVP_MD_size(c->outdigest))) {
- logger(LOG_ERR, "Got bad %s from %s(%s): %s", "CHAL_REPLY", c->name, c->hostname, "invalid hash");
- return false;
- }
- /* Calculate the hash from the challenge we sent */
- ctx = EVP_MD_CTX_create();
- if(!ctx) {
- abort();
- }
- if(!EVP_DigestInit(ctx, c->outdigest)
- || !EVP_DigestUpdate(ctx, c->hischallenge, RSA_size(c->rsa_key))
- || !EVP_DigestFinal(ctx, (unsigned char *)myhash, NULL)) {
- EVP_MD_CTX_destroy(ctx);
- logger(LOG_ERR, "Error during calculation of response from %s (%s): %s",
- c->name, c->hostname, ERR_error_string(ERR_get_error(), NULL));
- return false;
- }
- EVP_MD_CTX_destroy(ctx);
- /* Verify the incoming hash with the calculated hash */
- if(memcmp(hishash, myhash, EVP_MD_size(c->outdigest))) {
- logger(LOG_ERR, "Possible intruder %s (%s): %s", c->name,
- c->hostname, "wrong challenge reply");
- ifdebug(SCARY_THINGS) {
- bin2hex(myhash, hishash, SHA_DIGEST_LENGTH);
- hishash[SHA_DIGEST_LENGTH * 2] = '\0';
- logger(LOG_DEBUG, "Expected challenge reply: %s", hishash);
- }
- return false;
- }
- /* Identity has now been positively verified.
- Send an acknowledgement with the rest of the information needed.
- */
- c->allow_request = ACK;
- return send_ack(c);
- }
- bool send_ack(connection_t *c) {
- /* ACK message contains rest of the information the other end needs
- to create node_t and edge_t structures. */
- struct timeval now;
- bool choice;
- /* Estimate weight */
- gettimeofday(&now, NULL);
- c->estimated_weight = (now.tv_sec - c->start.tv_sec) * 1000 + (now.tv_usec - c->start.tv_usec) / 1000;
- /* Check some options */
- if((get_config_bool(lookup_config(c->config_tree, "IndirectData"), &choice) && choice) || myself->options & OPTION_INDIRECT) {
- c->options |= OPTION_INDIRECT;
- }
- if((get_config_bool(lookup_config(c->config_tree, "TCPOnly"), &choice) && choice) || myself->options & OPTION_TCPONLY) {
- c->options |= OPTION_TCPONLY | OPTION_INDIRECT;
- }
- if(myself->options & OPTION_PMTU_DISCOVERY && !(c->options & OPTION_TCPONLY)) {
- c->options |= OPTION_PMTU_DISCOVERY;
- }
- choice = myself->options & OPTION_CLAMP_MSS;
- get_config_bool(lookup_config(c->config_tree, "ClampMSS"), &choice);
- if(choice) {
- c->options |= OPTION_CLAMP_MSS;
- }
- get_config_int(lookup_config(c->config_tree, "Weight"), &c->estimated_weight);
- return send_request(c, "%d %s %d %x", ACK, myport, c->estimated_weight, c->options);
- }
- static void send_everything(connection_t *c) {
- avl_node_t *node, *node2;
- node_t *n;
- subnet_t *s;
- edge_t *e;
- /* Send all known subnets and edges */
- if(tunnelserver) {
- for(node = myself->subnet_tree->head; node; node = node->next) {
- s = node->data;
- send_add_subnet(c, s);
- }
- return;
- }
- for(node = node_tree->head; node; node = node->next) {
- n = node->data;
- for(node2 = n->subnet_tree->head; node2; node2 = node2->next) {
- s = node2->data;
- send_add_subnet(c, s);
- }
- for(node2 = n->edge_tree->head; node2; node2 = node2->next) {
- e = node2->data;
- send_add_edge(c, e);
- }
- }
- }
- bool ack_h(connection_t *c) {
- char hisport[MAX_STRING_SIZE];
- int weight, mtu;
- uint32_t options;
- node_t *n;
- bool choice;
- if(sscanf(c->buffer, "%*d " MAX_STRING " %d %x", hisport, &weight, &options) != 3) {
- logger(LOG_ERR, "Got bad %s from %s (%s)", "ACK", c->name,
- c->hostname);
- return false;
- }
- /* Check if we already have a node_t for him */
- n = lookup_node(c->name);
- if(!n) {
- n = new_node();
- n->name = xstrdup(c->name);
- node_add(n);
- } else {
- if(n->connection) {
- /* Oh dear, we already have a connection to this node. */
- ifdebug(CONNECTIONS) logger(LOG_DEBUG, "Established a second connection with %s (%s), closing old connection",
- n->name, n->hostname);
- terminate_connection(n->connection, false);
- /* Run graph algorithm to purge key and make sure up/down scripts are rerun with new IP addresses and stuff */
- graph();
- }
- }
- n->connection = c;
- c->node = n;
- if(!(c->options & options & OPTION_PMTU_DISCOVERY)) {
- c->options &= ~OPTION_PMTU_DISCOVERY;
- options &= ~OPTION_PMTU_DISCOVERY;
- }
- c->options |= options;
- if(get_config_int(lookup_config(c->config_tree, "PMTU"), &mtu) && mtu < n->mtu) {
- n->mtu = mtu;
- }
- if(get_config_int(lookup_config(config_tree, "PMTU"), &mtu) && mtu < n->mtu) {
- n->mtu = mtu;
- }
- if(get_config_bool(lookup_config(c->config_tree, "ClampMSS"), &choice)) {
- if(choice) {
- c->options |= OPTION_CLAMP_MSS;
- } else {
- c->options &= ~OPTION_CLAMP_MSS;
- }
- }
- /* Activate this connection */
- c->allow_request = ALL;
- c->status.active = true;
- ifdebug(CONNECTIONS) logger(LOG_NOTICE, "Connection with %s (%s) activated", c->name,
- c->hostname);
- /* Send him everything we know */
- send_everything(c);
- /* Create an edge_t for this connection */
- c->edge = new_edge();
- c->edge->from = myself;
- c->edge->to = n;
- sockaddrcpy(&c->edge->address, &c->address);
- sockaddr_setport(&c->edge->address, hisport);
- c->edge->weight = (weight + c->estimated_weight) / 2;
- c->edge->connection = c;
- c->edge->options = c->options;
- edge_add(c->edge);
- /* Notify everyone of the new edge */
- if(tunnelserver) {
- send_add_edge(c, c->edge);
- } else {
- send_add_edge(everyone, c->edge);
- }
- /* Run MST and SSSP algorithms */
- graph();
- return true;
- }
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