/** @internal
* @brief parse an incoming SSH_MSG_KEXDH_INIT packet and complete
* key exchange
**/
static int ssh_server_kexdh_init(ssh_session session, ssh_buffer packet){
ssh_string e;
e = buffer_get_ssh_string(packet);
if (e == NULL) {
ssh_set_error(session, SSH_FATAL, "No e number in client request");
return -1;
}
if (dh_import_e(session, e) < 0) {
ssh_set_error(session, SSH_FATAL, "Cannot import e number");
session->session_state=SSH_SESSION_STATE_ERROR;
} else {
session->dh_handshake_state=DH_STATE_INIT_SENT;
dh_handshake_server(session);
}
ssh_string_free(e);
return SSH_OK;
}
static int dh_handshake_server(SSH_SESSION *session) {
STRING *e;
STRING *f;
STRING *pubkey;
STRING *sign;
PUBLIC_KEY *pub;
PRIVATE_KEY *prv;
if (packet_wait(session, SSH2_MSG_KEXDH_INIT, 1) != SSH_OK) {
return -1;
}
e = buffer_get_ssh_string(session->in_buffer);
if (e == NULL) {
ssh_set_error(session, SSH_FATAL, "No e number in client request");
return -1;
}
if (dh_import_e(session, e) < 0) {
ssh_set_error(session, SSH_FATAL, "Cannot import e number");
string_free(e);
return -1;
}
string_free(e);
if (dh_generate_y(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create y number");
return -1;
}
if (dh_generate_f(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create f number");
return -1;
}
f = dh_get_f(session);
if (f == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not get the f number");
return -1;
}
switch(session->hostkeys){
case TYPE_DSS:
prv = session->dsa_key;
break;
case TYPE_RSA:
prv = session->rsa_key;
break;
default:
prv = NULL;
}
pub = publickey_from_privatekey(prv);
if (pub == NULL) {
ssh_set_error(session, SSH_FATAL,
"Could not get the public key from the private key");
string_free(f);
return -1;
}
pubkey = publickey_to_string(pub);
publickey_free(pub);
if (pubkey == NULL) {
ssh_set_error(session, SSH_FATAL, "Not enough space");
string_free(f);
return -1;
}
dh_import_pubkey(session, pubkey);
if (dh_build_k(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not import the public key");
string_free(f);
return -1;
}
if (make_sessionid(session) != SSH_OK) {
ssh_set_error(session, SSH_FATAL, "Could not create a session id");
string_free(f);
return -1;
}
sign = ssh_sign_session_id(session, prv);
if (sign == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not sign the session id");
string_free(f);
return -1;
}
/* Free private keys as they should not be readable after this point */
if (session->rsa_key) {
privatekey_free(session->rsa_key);
session->rsa_key = NULL;
}
if (session->dsa_key) {
privatekey_free(session->dsa_key);
session->dsa_key = NULL;
}
if (buffer_add_u8(session->out_buffer, SSH2_MSG_KEXDH_REPLY) < 0 ||
buffer_add_ssh_string(session->out_buffer, pubkey) < 0 ||
buffer_add_ssh_string(session->out_buffer, f) < 0 ||
buffer_add_ssh_string(session->out_buffer, sign) < 0) {
ssh_set_error(session, SSH_FATAL, "Not enough space");
buffer_free(session->out_buffer);
string_free(f);
string_free(sign);
return -1;
}
string_free(f);
string_free(sign);
if (packet_send(session) != SSH_OK) {
return -1;
}
if (buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS) < 0) {
buffer_free(session->out_buffer);
return -1;
}
if (packet_send(session) != SSH_OK) {
return -1;
}
ssh_log(session, SSH_LOG_PACKET, "SSH_MSG_NEWKEYS sent");
if (packet_wait(session, SSH2_MSG_NEWKEYS, 1) != SSH_OK) {
return -1;
}
ssh_log(session, SSH_LOG_PACKET, "Got SSH_MSG_NEWKEYS");
if (generate_session_keys(session) < 0) {
return -1;
}
/*
* Once we got SSH2_MSG_NEWKEYS we can switch next_crypto and
* current_crypto
*/
if (session->current_crypto) {
crypto_free(session->current_crypto);
}
/* FIXME TODO later, include a function to change keys */
session->current_crypto = session->next_crypto;
session->next_crypto = crypto_new();
if (session->next_crypto == NULL) {
return -1;
}
return 0;
}
static int dh_handshake_server(SSH_SESSION *session){
STRING *e,*f,*pubkey,*sign;
PUBLIC_KEY *pub;
PRIVATE_KEY *prv;
BUFFER *buf=buffer_new();
if(packet_wait(session, SSH2_MSG_KEXDH_INIT)) // FIXME BLOCKING
return -1;
e=buffer_get_ssh_string(session->in_buffer);
if(!e){
ssh_set_error(session,SSH_FATAL,"No e number in client request");
return -1;
}
dh_import_e(session,e);
dh_generate_y(session);
dh_generate_f(session);
f=dh_get_f(session);
switch(session->hostkeys){
case TYPE_DSS:
prv=session->dsa_key;
break;
case TYPE_RSA:
prv=session->rsa_key;
break;
default:
prv=NULL;
}
pub=publickey_from_privatekey(prv);
pubkey=publickey_to_string(pub);
publickey_free(pub);
dh_import_pubkey(session,pubkey);
dh_build_k(session);
make_sessionid(session);
sign=ssh_sign_session_id(session,prv);
buffer_free(buf);
/* free private keys as they should not be readable past this point */
if(session->rsa_key){
private_key_free(session->rsa_key);
session->rsa_key=NULL;
}
if(session->dsa_key){
private_key_free(session->dsa_key);
session->dsa_key=NULL;
}
buffer_add_u8(session->out_buffer,SSH2_MSG_KEXDH_REPLY);
buffer_add_ssh_string(session->out_buffer,pubkey);
buffer_add_ssh_string(session->out_buffer,f);
buffer_add_ssh_string(session->out_buffer,sign);
free(sign);
packet_send(session);
free(f);
packet_clear_out(session);
buffer_add_u8(session->out_buffer,SSH2_MSG_NEWKEYS);
packet_send(session);
ssh_say(2,"SSH_MSG_NEWKEYS sent\n");
packet_wait(session,SSH2_MSG_NEWKEYS);// FIXME BLOCKING
ssh_say(2,"Got SSH_MSG_NEWKEYS\n");
generate_session_keys(session);
/* once we got SSH2_MSG_NEWKEYS we can switch next_crypto and current_crypto */
if(session->current_crypto)
crypto_free(session->current_crypto);
/* XXX later, include a function to change keys */
session->current_crypto=session->next_crypto;
session->next_crypto=crypto_new();
return 0;
}
