int ssh_server_ecdh_init(ssh_session session, ssh_buffer packet){
/* ECDH keys */
ssh_string q_c_string;
ssh_string q_s_string;
EC_KEY *ecdh_key;
const EC_GROUP *group;
const EC_POINT *ecdh_pubkey;
bignum_CTX ctx;
/* SSH host keys (rsa,dsa,ecdsa) */
ssh_key privkey;
ssh_string sig_blob = NULL;
int len;
int rc;
/* Extract the client pubkey from the init packet */
q_c_string = ssh_buffer_get_ssh_string(packet);
if (q_c_string == NULL) {
ssh_set_error(session,SSH_FATAL, "No Q_C ECC point in packet");
return SSH_ERROR;
}
session->next_crypto->ecdh_client_pubkey = q_c_string;
/* Build server's keypair */
ctx = BN_CTX_new();
ecdh_key = EC_KEY_new_by_curve_name(NISTP256);
if (ecdh_key == NULL) {
ssh_set_error_oom(session);
BN_CTX_free(ctx);
return SSH_ERROR;
}
group = EC_KEY_get0_group(ecdh_key);
EC_KEY_generate_key(ecdh_key);
ecdh_pubkey = EC_KEY_get0_public_key(ecdh_key);
len = EC_POINT_point2oct(group,
ecdh_pubkey,
POINT_CONVERSION_UNCOMPRESSED,
NULL,
0,
ctx);
q_s_string = ssh_string_new(len);
if (q_s_string == NULL) {
EC_KEY_free(ecdh_key);
BN_CTX_free(ctx);
return SSH_ERROR;
}
EC_POINT_point2oct(group,
ecdh_pubkey,
POINT_CONVERSION_UNCOMPRESSED,
ssh_string_data(q_s_string),
len,
ctx);
BN_CTX_free(ctx);
session->next_crypto->ecdh_privkey = ecdh_key;
session->next_crypto->ecdh_server_pubkey = q_s_string;
/* build k and session_id */
rc = ecdh_build_k(session);
if (rc < 0) {
ssh_set_error(session, SSH_FATAL, "Cannot build k number");
return SSH_ERROR;
}
/* privkey is not allocated */
rc = ssh_get_key_params(session, &privkey);
if (rc == SSH_ERROR) {
return SSH_ERROR;
}
rc = ssh_make_sessionid(session);
if (rc != SSH_OK) {
ssh_set_error(session, SSH_FATAL, "Could not create a session id");
return SSH_ERROR;
}
sig_blob = ssh_srv_pki_do_sign_sessionid(session, privkey);
if (sig_blob == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not sign the session id");
return SSH_ERROR;
}
rc = ssh_buffer_pack(session->out_buffer,
"bSSS",
SSH2_MSG_KEXDH_REPLY,
session->next_crypto->server_pubkey, /* host's pubkey */
q_s_string, /* ecdh public key */
sig_blob); /* signature blob */
ssh_string_free(sig_blob);
if (rc != SSH_OK) {
ssh_set_error_oom(session);
return SSH_ERROR;
}
SSH_LOG(SSH_LOG_PROTOCOL, "SSH_MSG_KEXDH_REPLY sent");
rc = ssh_packet_send(session);
if (rc == SSH_ERROR) {
return SSH_ERROR;
}
/* Send the MSG_NEWKEYS */
rc = ssh_buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS);
if (rc < 0) {
return SSH_ERROR;;
}
session->dh_handshake_state = DH_STATE_NEWKEYS_SENT;
rc = ssh_packet_send(session);
SSH_LOG(SSH_LOG_PROTOCOL, "SSH_MSG_NEWKEYS sent");
return rc;
}
static int dh_handshake_server(ssh_session session) {
ssh_key privkey;
ssh_string sig_blob;
ssh_string f;
ssh_string pubkey_blob = NULL;
int rc;
if (ssh_dh_generate_y(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create y number");
return -1;
}
if (ssh_dh_generate_f(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create f number");
return -1;
}
f = ssh_dh_get_f(session);
if (f == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not get the f number");
return -1;
}
if (ssh_get_key_params(session,&privkey) != SSH_OK){
ssh_string_free(f);
return -1;
}
if (ssh_dh_build_k(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not import the public key");
ssh_string_free(f);
return -1;
}
if (ssh_make_sessionid(session) != SSH_OK) {
ssh_set_error(session, SSH_FATAL, "Could not create a session id");
ssh_string_free(f);
return -1;
}
sig_blob = ssh_srv_pki_do_sign_sessionid(session, privkey);
if (sig_blob == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not sign the session id");
ssh_string_free(f);
return -1;
}
rc = ssh_dh_get_next_server_publickey_blob(session, &pubkey_blob);
if (rc != SSH_OK) {
ssh_set_error_oom(session);
ssh_string_free(f);
ssh_string_free(sig_blob);
return -1;
}
rc = ssh_buffer_pack(session->out_buffer,
"bSSS",
SSH2_MSG_KEXDH_REPLY,
pubkey_blob,
f,
sig_blob);
ssh_string_free(f);
ssh_string_free(sig_blob);
ssh_string_free(pubkey_blob);
if(rc != SSH_OK){
ssh_set_error_oom(session);
ssh_buffer_reinit(session->out_buffer);
return -1;
}
if (ssh_packet_send(session) == SSH_ERROR) {
return -1;
}
if (ssh_buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS) < 0) {
ssh_buffer_reinit(session->out_buffer);
return -1;
}
if (ssh_packet_send(session) == SSH_ERROR) {
return -1;
}
SSH_LOG(SSH_LOG_PACKET, "SSH_MSG_NEWKEYS sent");
session->dh_handshake_state=DH_STATE_NEWKEYS_SENT;
return 0;
}
