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/*
* Dropbear - a SSH2 server
*
* Copyright (c) 2002,2003 Matt Johnston
* Copyright (c) 2004 by Mihnea Stoenescu
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
#include "includes.h"
#include "dbutil.h"
#include "algo.h"
#include "buffer.h"
#include "session.h"
#include "kex.h"
#include "ssh.h"
#include "packet.h"
#include "bignum.h"
#include "dbrandom.h"
#include "runopts.h"
#include "ecc.h"
#include "gensignkey.h"
static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs);
/* Handle a diffie-hellman key exchange initialisation. This involves
* calculating a session key reply value, and corresponding hash. These
* are carried out by send_msg_kexdh_reply(). recv_msg_kexdh_init() calls
* that function, then brings the new keys into use */
void recv_msg_kexdh_init() {
DEF_MP_INT(dh_e);
buffer *ecdh_qs = NULL;
TRACE(("enter recv_msg_kexdh_init"))
if (!ses.kexstate.recvkexinit) {
dropbear_exit("Premature kexdh_init message received");
}
switch (ses.newkeys->algo_kex->mode) {
#if DROPBEAR_NORMAL_DH
case DROPBEAR_KEX_NORMAL_DH:
m_mp_init(&dh_e);
if (buf_getmpint(ses.payload, &dh_e) != DROPBEAR_SUCCESS) {
dropbear_exit("Bad kex value");
}
break;
#endif
#if DROPBEAR_ECDH
case DROPBEAR_KEX_ECDH:
#endif
#if DROPBEAR_CURVE25519
case DROPBEAR_KEX_CURVE25519:
#endif
#if DROPBEAR_ECDH || DROPBEAR_CURVE25519
ecdh_qs = buf_getstringbuf(ses.payload);
break;
#endif
}
if (ses.payload->pos != ses.payload->len) {
dropbear_exit("Bad kex value");
}
send_msg_kexdh_reply(&dh_e, ecdh_qs);
mp_clear(&dh_e);
if (ecdh_qs) {
buf_free(ecdh_qs);
ecdh_qs = NULL;
}
send_msg_newkeys();
ses.requirenext = SSH_MSG_NEWKEYS;
TRACE(("leave recv_msg_kexdh_init"))
}
#if DROPBEAR_DELAY_HOSTKEY
static void svr_ensure_hostkey() {
const char* fn = NULL;
enum signkey_type type = ses.newkeys->algo_hostkey;
void **hostkey = signkey_key_ptr(svr_opts.hostkey, type);
int ret = DROPBEAR_FAILURE;
if (hostkey && *hostkey) {
return;
}
switch (type)
{
#if DROPBEAR_RSA
case DROPBEAR_SIGNKEY_RSA:
fn = RSA_PRIV_FILENAME;
break;
#endif
#if DROPBEAR_DSS
case DROPBEAR_SIGNKEY_DSS:
fn = DSS_PRIV_FILENAME;
break;
#endif
#if DROPBEAR_ECDSA
case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
case DROPBEAR_SIGNKEY_ECDSA_NISTP384:
case DROPBEAR_SIGNKEY_ECDSA_NISTP521:
fn = ECDSA_PRIV_FILENAME;
break;
#endif
default:
dropbear_assert(0);
}
if (readhostkey(fn, svr_opts.hostkey, &type) == DROPBEAR_SUCCESS) {
return;
}
if (signkey_generate(type, 0, fn, 1) == DROPBEAR_FAILURE) {
goto out;
}
ret = readhostkey(fn, svr_opts.hostkey, &type);
if (ret == DROPBEAR_SUCCESS) {
char *fp = NULL;
unsigned int len;
buffer *key_buf = buf_new(MAX_PUBKEY_SIZE);
buf_put_pub_key(key_buf, svr_opts.hostkey, type);
buf_setpos(key_buf, 4);
len = key_buf->len - key_buf->pos;
fp = sign_key_fingerprint(buf_getptr(key_buf, len), len);
dropbear_log(LOG_INFO, "Generated hostkey %s, fingerprint is %s",
fn, fp);
m_free(fp);
buf_free(key_buf);
}
out:
if (ret == DROPBEAR_FAILURE)
{
dropbear_exit("Couldn't read or generate hostkey %s", fn);
}
}
#endif
/* Generate our side of the diffie-hellman key exchange value (dh_f), and
* calculate the session key using the diffie-hellman algorithm. Following
* that, the session hash is calculated, and signed with RSA or DSS. The
* result is sent to the client.
*
* See the transport RFC4253 section 8 for details
* or RFC5656 section 4 for elliptic curve variant. */
static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs) {
TRACE(("enter send_msg_kexdh_reply"))
/* we can start creating the kexdh_reply packet */
CHECKCLEARTOWRITE();
#if DROPBEAR_DELAY_HOSTKEY
if (svr_opts.delay_hostkey)
{
svr_ensure_hostkey();
}
#endif
#if DROPBEAR_FUZZ
if (fuzz.fuzzing && fuzz.skip_kexmaths) {
fuzz_fake_send_kexdh_reply();
return;
}
#endif
buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_REPLY);
buf_put_pub_key(ses.writepayload, svr_opts.hostkey,
ses.newkeys->algo_hostkey);
switch (ses.newkeys->algo_kex->mode) {
#if DROPBEAR_NORMAL_DH
case DROPBEAR_KEX_NORMAL_DH:
{
struct kex_dh_param * dh_param = gen_kexdh_param();
kexdh_comb_key(dh_param, dh_e, svr_opts.hostkey);
/* put f */
buf_putmpint(ses.writepayload, &dh_param->pub);
free_kexdh_param(dh_param);
}
break;
#endif
#if DROPBEAR_ECDH
case DROPBEAR_KEX_ECDH:
{
struct kex_ecdh_param *ecdh_param = gen_kexecdh_param();
kexecdh_comb_key(ecdh_param, ecdh_qs, svr_opts.hostkey);
buf_put_ecc_raw_pubkey_string(ses.writepayload, &ecdh_param->key);
free_kexecdh_param(ecdh_param);
}
break;
#endif
#if DROPBEAR_CURVE25519
case DROPBEAR_KEX_CURVE25519:
{
struct kex_curve25519_param *param = gen_kexcurve25519_param();
kexcurve25519_comb_key(param, ecdh_qs, svr_opts.hostkey);
buf_putstring(ses.writepayload, (const char*)param->pub, CURVE25519_LEN);
free_kexcurve25519_param(param);
}
break;
#endif
}
/* calc the signature */
buf_put_sign(ses.writepayload, svr_opts.hostkey,
ses.newkeys->algo_hostkey, ses.hash);
/* the SSH_MSG_KEXDH_REPLY is done */
encrypt_packet();
TRACE(("leave send_msg_kexdh_reply"))
}
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