797 lines
25 KiB
C
797 lines
25 KiB
C
/*
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* Dropbear SSH
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*
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* Copyright (c) 2002-2004 Matt Johnston
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* Portions Copyright (c) 2004 by Mihnea Stoenescu
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE. */
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#include "includes.h"
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#include "dbutil.h"
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#include "algo.h"
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#include "buffer.h"
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#include "session.h"
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#include "kex.h"
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#include "ssh.h"
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#include "packet.h"
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#include "bignum.h"
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#include "random.h"
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#include "runopts.h"
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/* diffie-hellman-group1-sha1 value for p */
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#define DH_P_1_LEN 128
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static const unsigned char dh_p_1[DH_P_1_LEN] = {
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
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0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
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0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
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0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
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0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
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0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
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0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
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0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
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0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
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0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
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/* diffie-hellman-group14-sha1 value for p */
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#define DH_P_14_LEN 256
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static const unsigned char dh_p_14[DH_P_14_LEN] = {
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
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0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
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0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
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0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
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0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
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0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
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0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
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0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
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0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
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0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D,
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0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36,
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0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F,
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0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56,
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0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D,
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0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08,
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0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B,
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0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2,
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0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9,
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0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C,
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0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10,
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0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF};
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/* Same for group1 and group14 */
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static const int DH_G_VAL = 2;
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static void kexinitialise();
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void gen_new_keys();
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#ifndef DISABLE_ZLIB
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static void gen_new_zstreams();
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#endif
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static void read_kex_algos();
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/* helper function for gen_new_keys */
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static void hashkeys(unsigned char *out, int outlen,
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const hash_state * hs, unsigned const char X);
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/* Send our list of algorithms we can use */
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void send_msg_kexinit() {
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CHECKCLEARTOWRITE();
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buf_putbyte(ses.writepayload, SSH_MSG_KEXINIT);
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/* cookie */
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genrandom(buf_getwriteptr(ses.writepayload, 16), 16);
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buf_incrwritepos(ses.writepayload, 16);
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/* kex algos */
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buf_put_algolist(ses.writepayload, sshkex);
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/* server_host_key_algorithms */
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buf_put_algolist(ses.writepayload, sshhostkey);
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/* encryption_algorithms_client_to_server */
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buf_put_algolist(ses.writepayload, sshciphers);
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/* encryption_algorithms_server_to_client */
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buf_put_algolist(ses.writepayload, sshciphers);
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/* mac_algorithms_client_to_server */
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buf_put_algolist(ses.writepayload, sshhashes);
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/* mac_algorithms_server_to_client */
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buf_put_algolist(ses.writepayload, sshhashes);
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/* compression_algorithms_client_to_server */
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buf_put_algolist(ses.writepayload, ses.compress_algos);
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/* compression_algorithms_server_to_client */
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buf_put_algolist(ses.writepayload, ses.compress_algos);
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/* languages_client_to_server */
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buf_putstring(ses.writepayload, "", 0);
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/* languages_server_to_client */
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buf_putstring(ses.writepayload, "", 0);
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/* first_kex_packet_follows - unimplemented for now */
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buf_putbyte(ses.writepayload, 0x00);
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/* reserved unit32 */
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buf_putint(ses.writepayload, 0);
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/* set up transmitted kex packet buffer for hashing.
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* This is freed after the end of the kex */
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ses.transkexinit = buf_newcopy(ses.writepayload);
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encrypt_packet();
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ses.dataallowed = 0; /* don't send other packets during kex */
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TRACE(("DATAALLOWED=0"))
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TRACE(("-> KEXINIT"))
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ses.kexstate.sentkexinit = 1;
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}
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/* *** NOTE regarding (send|recv)_msg_newkeys ***
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* Changed by mihnea from the original kex.c to set dataallowed after a
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* completed key exchange, no matter the order in which it was performed.
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* This enables client mode without affecting server functionality.
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*/
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/* Bring new keys into use after a key exchange, and let the client know*/
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void send_msg_newkeys() {
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TRACE(("enter send_msg_newkeys"))
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/* generate the kexinit request */
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CHECKCLEARTOWRITE();
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buf_putbyte(ses.writepayload, SSH_MSG_NEWKEYS);
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encrypt_packet();
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/* set up our state */
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if (ses.kexstate.recvnewkeys) {
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TRACE(("while RECVNEWKEYS=1"))
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gen_new_keys();
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kexinitialise(); /* we've finished with this kex */
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TRACE((" -> DATAALLOWED=1"))
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ses.dataallowed = 1; /* we can send other packets again now */
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ses.kexstate.donefirstkex = 1;
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} else {
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ses.kexstate.sentnewkeys = 1;
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TRACE(("SENTNEWKEYS=1"))
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}
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TRACE(("-> MSG_NEWKEYS"))
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TRACE(("leave send_msg_newkeys"))
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}
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/* Bring the new keys into use after a key exchange */
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void recv_msg_newkeys() {
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TRACE(("<- MSG_NEWKEYS"))
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TRACE(("enter recv_msg_newkeys"))
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/* simply check if we've sent SSH_MSG_NEWKEYS, and if so,
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* switch to the new keys */
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if (ses.kexstate.sentnewkeys) {
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TRACE(("while SENTNEWKEYS=1"))
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gen_new_keys();
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kexinitialise(); /* we've finished with this kex */
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TRACE((" -> DATAALLOWED=1"))
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ses.dataallowed = 1; /* we can send other packets again now */
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ses.kexstate.donefirstkex = 1;
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} else {
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TRACE(("RECVNEWKEYS=1"))
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ses.kexstate.recvnewkeys = 1;
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}
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TRACE(("leave recv_msg_newkeys"))
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}
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/* Set up the kex for the first time */
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void kexfirstinitialise() {
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ses.kexstate.donefirstkex = 0;
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#ifndef DISABLE_ZLIB
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if (opts.enable_compress) {
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ses.compress_algos = ssh_compress;
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} else
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#endif
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{
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ses.compress_algos = ssh_nocompress;
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}
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kexinitialise();
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}
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/* Reset the kex state, ready for a new negotiation */
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static void kexinitialise() {
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TRACE(("kexinitialise()"))
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/* sent/recv'd MSG_KEXINIT */
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ses.kexstate.sentkexinit = 0;
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ses.kexstate.recvkexinit = 0;
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/* sent/recv'd MSG_NEWKEYS */
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ses.kexstate.recvnewkeys = 0;
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ses.kexstate.sentnewkeys = 0;
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/* first_packet_follows */
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ses.kexstate.firstfollows = 0;
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ses.kexstate.datatrans = 0;
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ses.kexstate.datarecv = 0;
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ses.kexstate.lastkextime = time(NULL);
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}
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/* Helper function for gen_new_keys, creates a hash. It makes a copy of the
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* already initialised hash_state hs, which should already have processed
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* the dh_K and hash, since these are common. X is the letter 'A', 'B' etc.
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* out must have at least min(SHA1_HASH_SIZE, outlen) bytes allocated.
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* The output will only be expanded once, as we are assured that
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* outlen <= 2*SHA1_HASH_SIZE for all known hashes.
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*
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* See Section 7.2 of rfc4253 (ssh transport) for details */
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static void hashkeys(unsigned char *out, int outlen,
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const hash_state * hs, const unsigned char X) {
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hash_state hs2;
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unsigned char k2[SHA1_HASH_SIZE]; /* used to extending */
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memcpy(&hs2, hs, sizeof(hash_state));
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sha1_process(&hs2, &X, 1);
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sha1_process(&hs2, ses.session_id, SHA1_HASH_SIZE);
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sha1_done(&hs2, out);
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if (SHA1_HASH_SIZE < outlen) {
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/* need to extend */
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memcpy(&hs2, hs, sizeof(hash_state));
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sha1_process(&hs2, out, SHA1_HASH_SIZE);
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sha1_done(&hs2, k2);
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memcpy(&out[SHA1_HASH_SIZE], k2, outlen - SHA1_HASH_SIZE);
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}
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}
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/* Generate the actual encryption/integrity keys, using the results of the
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* key exchange, as specified in section 7.2 of the transport rfc 4253.
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* This occurs after the DH key-exchange.
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*
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* ses.newkeys is the new set of keys which are generated, these are only
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* taken into use after both sides have sent a newkeys message */
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/* Originally from kex.c, generalized for cli/svr mode --mihnea */
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void gen_new_keys() {
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unsigned char C2S_IV[MAX_IV_LEN];
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unsigned char C2S_key[MAX_KEY_LEN];
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unsigned char S2C_IV[MAX_IV_LEN];
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unsigned char S2C_key[MAX_KEY_LEN];
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/* unsigned char key[MAX_KEY_LEN]; */
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unsigned char *trans_IV, *trans_key, *recv_IV, *recv_key;
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hash_state hs;
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unsigned int C2S_keysize, S2C_keysize;
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char mactransletter, macrecvletter; /* Client or server specific */
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int recv_cipher = 0, trans_cipher = 0;
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TRACE(("enter gen_new_keys"))
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/* the dh_K and hash are the start of all hashes, we make use of that */
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sha1_init(&hs);
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sha1_process_mp(&hs, ses.dh_K);
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mp_clear(ses.dh_K);
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m_free(ses.dh_K);
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sha1_process(&hs, ses.hash, SHA1_HASH_SIZE);
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m_burn(ses.hash, SHA1_HASH_SIZE);
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if (IS_DROPBEAR_CLIENT) {
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trans_IV = C2S_IV;
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recv_IV = S2C_IV;
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trans_key = C2S_key;
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recv_key = S2C_key;
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C2S_keysize = ses.newkeys->trans.algo_crypt->keysize;
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S2C_keysize = ses.newkeys->recv.algo_crypt->keysize;
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mactransletter = 'E';
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macrecvletter = 'F';
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} else {
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trans_IV = S2C_IV;
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recv_IV = C2S_IV;
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trans_key = S2C_key;
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recv_key = C2S_key;
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C2S_keysize = ses.newkeys->recv.algo_crypt->keysize;
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S2C_keysize = ses.newkeys->trans.algo_crypt->keysize;
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mactransletter = 'F';
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macrecvletter = 'E';
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}
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hashkeys(C2S_IV, SHA1_HASH_SIZE, &hs, 'A');
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hashkeys(S2C_IV, SHA1_HASH_SIZE, &hs, 'B');
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hashkeys(C2S_key, C2S_keysize, &hs, 'C');
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hashkeys(S2C_key, S2C_keysize, &hs, 'D');
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recv_cipher = find_cipher(ses.newkeys->recv.algo_crypt->cipherdesc->name);
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if (recv_cipher < 0)
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dropbear_exit("Crypto error");
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if (ses.newkeys->recv.crypt_mode->start(recv_cipher,
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recv_IV, recv_key,
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ses.newkeys->recv.algo_crypt->keysize, 0,
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&ses.newkeys->recv.cipher_state) != CRYPT_OK) {
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dropbear_exit("Crypto error");
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}
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trans_cipher = find_cipher(ses.newkeys->trans.algo_crypt->cipherdesc->name);
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if (trans_cipher < 0)
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dropbear_exit("Crypto error");
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if (ses.newkeys->trans.crypt_mode->start(trans_cipher,
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trans_IV, trans_key,
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ses.newkeys->trans.algo_crypt->keysize, 0,
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&ses.newkeys->trans.cipher_state) != CRYPT_OK) {
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dropbear_exit("Crypto error");
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}
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/* MAC keys */
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hashkeys(ses.newkeys->trans.mackey,
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ses.newkeys->trans.algo_mac->keysize, &hs, mactransletter);
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hashkeys(ses.newkeys->recv.mackey,
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ses.newkeys->recv.algo_mac->keysize, &hs, macrecvletter);
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ses.newkeys->trans.hash_index = find_hash(ses.newkeys->trans.algo_mac->hashdesc->name),
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ses.newkeys->recv.hash_index = find_hash(ses.newkeys->recv.algo_mac->hashdesc->name),
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#ifndef DISABLE_ZLIB
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gen_new_zstreams();
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#endif
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/* Switch over to the new keys */
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m_burn(ses.keys, sizeof(struct key_context));
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m_free(ses.keys);
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ses.keys = ses.newkeys;
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ses.newkeys = NULL;
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m_burn(C2S_IV, sizeof(C2S_IV));
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m_burn(C2S_key, sizeof(C2S_key));
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m_burn(S2C_IV, sizeof(S2C_IV));
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m_burn(S2C_key, sizeof(S2C_key));
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TRACE(("leave gen_new_keys"))
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}
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#ifndef DISABLE_ZLIB
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int is_compress_trans() {
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return ses.keys->trans.algo_comp == DROPBEAR_COMP_ZLIB
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|| (ses.authstate.authdone
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&& ses.keys->trans.algo_comp == DROPBEAR_COMP_ZLIB_DELAY);
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}
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int is_compress_recv() {
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return ses.keys->recv.algo_comp == DROPBEAR_COMP_ZLIB
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|| (ses.authstate.authdone
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&& ses.keys->recv.algo_comp == DROPBEAR_COMP_ZLIB_DELAY);
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}
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/* Set up new zlib compression streams, close the old ones. Only
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* called from gen_new_keys() */
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static void gen_new_zstreams() {
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/* create new zstreams */
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if (ses.newkeys->recv.algo_comp == DROPBEAR_COMP_ZLIB
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|| ses.newkeys->recv.algo_comp == DROPBEAR_COMP_ZLIB_DELAY) {
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|
ses.newkeys->recv.zstream = (z_streamp)m_malloc(sizeof(z_stream));
|
|
ses.newkeys->recv.zstream->zalloc = Z_NULL;
|
|
ses.newkeys->recv.zstream->zfree = Z_NULL;
|
|
|
|
if (inflateInit(ses.newkeys->recv.zstream) != Z_OK) {
|
|
dropbear_exit("zlib error");
|
|
}
|
|
} else {
|
|
ses.newkeys->recv.zstream = NULL;
|
|
}
|
|
|
|
if (ses.newkeys->trans.algo_comp == DROPBEAR_COMP_ZLIB
|
|
|| ses.newkeys->trans.algo_comp == DROPBEAR_COMP_ZLIB_DELAY) {
|
|
ses.newkeys->trans.zstream = (z_streamp)m_malloc(sizeof(z_stream));
|
|
ses.newkeys->trans.zstream->zalloc = Z_NULL;
|
|
ses.newkeys->trans.zstream->zfree = Z_NULL;
|
|
|
|
if (deflateInit2(ses.newkeys->trans.zstream, Z_DEFAULT_COMPRESSION,
|
|
Z_DEFLATED, DROPBEAR_ZLIB_WINDOW_BITS,
|
|
DROPBEAR_ZLIB_MEM_LEVEL, Z_DEFAULT_STRATEGY)
|
|
!= Z_OK) {
|
|
dropbear_exit("zlib error");
|
|
}
|
|
} else {
|
|
ses.newkeys->trans.zstream = NULL;
|
|
}
|
|
|
|
/* clean up old keys */
|
|
if (ses.keys->recv.zstream != NULL) {
|
|
if (inflateEnd(ses.keys->recv.zstream) == Z_STREAM_ERROR) {
|
|
/* Z_DATA_ERROR is ok, just means that stream isn't ended */
|
|
dropbear_exit("Crypto error");
|
|
}
|
|
m_free(ses.keys->recv.zstream);
|
|
}
|
|
if (ses.keys->trans.zstream != NULL) {
|
|
if (deflateEnd(ses.keys->trans.zstream) == Z_STREAM_ERROR) {
|
|
/* Z_DATA_ERROR is ok, just means that stream isn't ended */
|
|
dropbear_exit("Crypto error");
|
|
}
|
|
m_free(ses.keys->trans.zstream);
|
|
}
|
|
}
|
|
#endif /* DISABLE_ZLIB */
|
|
|
|
|
|
/* Executed upon receiving a kexinit message from the client to initiate
|
|
* key exchange. If we haven't already done so, we send the list of our
|
|
* preferred algorithms. The client's requested algorithms are processed,
|
|
* and we calculate the first portion of the key-exchange-hash for used
|
|
* later in the key exchange. No response is sent, as the client should
|
|
* initiate the diffie-hellman key exchange */
|
|
|
|
/* Originally from kex.c, generalized for cli/svr mode --mihnea */
|
|
/* Belongs in common_kex.c where it should be moved after review */
|
|
void recv_msg_kexinit() {
|
|
|
|
unsigned int kexhashbuf_len = 0;
|
|
unsigned int remote_ident_len = 0;
|
|
unsigned int local_ident_len = 0;
|
|
|
|
TRACE(("<- KEXINIT"))
|
|
TRACE(("enter recv_msg_kexinit"))
|
|
|
|
if (!ses.kexstate.sentkexinit) {
|
|
/* we need to send a kex packet */
|
|
send_msg_kexinit();
|
|
TRACE(("continue recv_msg_kexinit: sent kexinit"))
|
|
}
|
|
|
|
/* start the kex hash */
|
|
local_ident_len = strlen(LOCAL_IDENT);
|
|
remote_ident_len = strlen((char*)ses.remoteident);
|
|
|
|
kexhashbuf_len = local_ident_len + remote_ident_len
|
|
+ ses.transkexinit->len + ses.payload->len
|
|
+ KEXHASHBUF_MAX_INTS;
|
|
|
|
ses.kexhashbuf = buf_new(kexhashbuf_len);
|
|
|
|
if (IS_DROPBEAR_CLIENT) {
|
|
|
|
/* read the peer's choice of algos */
|
|
read_kex_algos();
|
|
|
|
/* V_C, the client's version string (CR and NL excluded) */
|
|
buf_putstring(ses.kexhashbuf,
|
|
(unsigned char*)LOCAL_IDENT, local_ident_len);
|
|
/* V_S, the server's version string (CR and NL excluded) */
|
|
buf_putstring(ses.kexhashbuf, ses.remoteident, remote_ident_len);
|
|
|
|
/* I_C, the payload of the client's SSH_MSG_KEXINIT */
|
|
buf_putstring(ses.kexhashbuf,
|
|
ses.transkexinit->data, ses.transkexinit->len);
|
|
/* I_S, the payload of the server's SSH_MSG_KEXINIT */
|
|
buf_setpos(ses.payload, 0);
|
|
buf_putstring(ses.kexhashbuf, ses.payload->data, ses.payload->len);
|
|
|
|
} else {
|
|
/* SERVER */
|
|
|
|
/* read the peer's choice of algos */
|
|
read_kex_algos();
|
|
/* V_C, the client's version string (CR and NL excluded) */
|
|
buf_putstring(ses.kexhashbuf, ses.remoteident, remote_ident_len);
|
|
/* V_S, the server's version string (CR and NL excluded) */
|
|
buf_putstring(ses.kexhashbuf,
|
|
(unsigned char*)LOCAL_IDENT, local_ident_len);
|
|
|
|
/* I_C, the payload of the client's SSH_MSG_KEXINIT */
|
|
buf_setpos(ses.payload, 0);
|
|
buf_putstring(ses.kexhashbuf, ses.payload->data, ses.payload->len);
|
|
|
|
/* I_S, the payload of the server's SSH_MSG_KEXINIT */
|
|
buf_putstring(ses.kexhashbuf,
|
|
ses.transkexinit->data, ses.transkexinit->len);
|
|
|
|
ses.requirenext = SSH_MSG_KEXDH_INIT;
|
|
}
|
|
|
|
buf_free(ses.transkexinit);
|
|
ses.transkexinit = NULL;
|
|
/* the rest of ses.kexhashbuf will be done after DH exchange */
|
|
|
|
ses.kexstate.recvkexinit = 1;
|
|
|
|
TRACE(("leave recv_msg_kexinit"))
|
|
}
|
|
|
|
static void load_dh_p(mp_int * dh_p)
|
|
{
|
|
switch (ses.newkeys->algo_kex) {
|
|
case DROPBEAR_KEX_DH_GROUP1:
|
|
bytes_to_mp(dh_p, dh_p_1, DH_P_1_LEN);
|
|
break;
|
|
case DROPBEAR_KEX_DH_GROUP14:
|
|
bytes_to_mp(dh_p, dh_p_14, DH_P_14_LEN);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* Initialises and generate one side of the diffie-hellman key exchange values.
|
|
* See the transport rfc 4253 section 8 for details */
|
|
/* dh_pub and dh_priv MUST be already initialised */
|
|
void gen_kexdh_vals(mp_int *dh_pub, mp_int *dh_priv) {
|
|
|
|
DEF_MP_INT(dh_p);
|
|
DEF_MP_INT(dh_q);
|
|
DEF_MP_INT(dh_g);
|
|
|
|
TRACE(("enter send_msg_kexdh_reply"))
|
|
|
|
m_mp_init_multi(&dh_g, &dh_p, &dh_q, NULL);
|
|
|
|
/* read the prime and generator*/
|
|
load_dh_p(&dh_p);
|
|
|
|
if (mp_set_int(&dh_g, DH_G_VAL) != MP_OKAY) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
|
|
/* calculate q = (p-1)/2 */
|
|
/* dh_priv is just a temp var here */
|
|
if (mp_sub_d(&dh_p, 1, dh_priv) != MP_OKAY) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
if (mp_div_2(dh_priv, &dh_q) != MP_OKAY) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
|
|
/* Generate a private portion 0 < dh_priv < dh_q */
|
|
gen_random_mpint(&dh_q, dh_priv);
|
|
|
|
/* f = g^y mod p */
|
|
if (mp_exptmod(&dh_g, dh_priv, &dh_p, dh_pub) != MP_OKAY) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
mp_clear_multi(&dh_g, &dh_p, &dh_q, NULL);
|
|
}
|
|
|
|
/* This function is fairly common between client/server, with some substitution
|
|
* of dh_e/dh_f etc. Hence these arguments:
|
|
* dh_pub_us is 'e' for the client, 'f' for the server. dh_pub_them is
|
|
* vice-versa. dh_priv is the x/y value corresponding to dh_pub_us */
|
|
void kexdh_comb_key(mp_int *dh_pub_us, mp_int *dh_priv, mp_int *dh_pub_them,
|
|
sign_key *hostkey) {
|
|
|
|
mp_int dh_p;
|
|
mp_int *dh_e = NULL, *dh_f = NULL;
|
|
hash_state hs;
|
|
|
|
/* read the prime and generator*/
|
|
m_mp_init(&dh_p);
|
|
load_dh_p(&dh_p);
|
|
|
|
/* Check that dh_pub_them (dh_e or dh_f) is in the range [1, p-1] */
|
|
if (mp_cmp(dh_pub_them, &dh_p) != MP_LT
|
|
|| mp_cmp_d(dh_pub_them, 0) != MP_GT) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
|
|
/* K = e^y mod p = f^x mod p */
|
|
ses.dh_K = (mp_int*)m_malloc(sizeof(mp_int));
|
|
m_mp_init(ses.dh_K);
|
|
if (mp_exptmod(dh_pub_them, dh_priv, &dh_p, ses.dh_K) != MP_OKAY) {
|
|
dropbear_exit("Diffie-Hellman error");
|
|
}
|
|
|
|
/* clear no longer needed vars */
|
|
mp_clear_multi(&dh_p, NULL);
|
|
|
|
/* From here on, the code needs to work with the _same_ vars on each side,
|
|
* not vice-versaing for client/server */
|
|
if (IS_DROPBEAR_CLIENT) {
|
|
dh_e = dh_pub_us;
|
|
dh_f = dh_pub_them;
|
|
} else {
|
|
dh_e = dh_pub_them;
|
|
dh_f = dh_pub_us;
|
|
}
|
|
|
|
/* Create the remainder of the hash buffer, to generate the exchange hash */
|
|
/* K_S, the host key */
|
|
buf_put_pub_key(ses.kexhashbuf, hostkey, ses.newkeys->algo_hostkey);
|
|
/* e, exchange value sent by the client */
|
|
buf_putmpint(ses.kexhashbuf, dh_e);
|
|
/* f, exchange value sent by the server */
|
|
buf_putmpint(ses.kexhashbuf, dh_f);
|
|
/* K, the shared secret */
|
|
buf_putmpint(ses.kexhashbuf, ses.dh_K);
|
|
|
|
/* calculate the hash H to sign */
|
|
sha1_init(&hs);
|
|
buf_setpos(ses.kexhashbuf, 0);
|
|
sha1_process(&hs, buf_getptr(ses.kexhashbuf, ses.kexhashbuf->len),
|
|
ses.kexhashbuf->len);
|
|
sha1_done(&hs, ses.hash);
|
|
|
|
buf_burn(ses.kexhashbuf);
|
|
buf_free(ses.kexhashbuf);
|
|
ses.kexhashbuf = NULL;
|
|
|
|
/* first time around, we set the session_id to H */
|
|
if (ses.session_id == NULL) {
|
|
/* create the session_id, this never needs freeing */
|
|
ses.session_id = (unsigned char*)m_malloc(SHA1_HASH_SIZE);
|
|
memcpy(ses.session_id, ses.hash, SHA1_HASH_SIZE);
|
|
}
|
|
}
|
|
|
|
/* read the other side's algo list. buf_match_algo is a callback to match
|
|
* algos for the client or server. */
|
|
static void read_kex_algos() {
|
|
|
|
/* for asymmetry */
|
|
algo_type * c2s_hash_algo = NULL;
|
|
algo_type * s2c_hash_algo = NULL;
|
|
algo_type * c2s_cipher_algo = NULL;
|
|
algo_type * s2c_cipher_algo = NULL;
|
|
algo_type * c2s_comp_algo = NULL;
|
|
algo_type * s2c_comp_algo = NULL;
|
|
/* the generic one */
|
|
algo_type * algo = NULL;
|
|
|
|
/* which algo couldn't match */
|
|
char * erralgo = NULL;
|
|
|
|
int goodguess = 0;
|
|
int allgood = 1; /* we AND this with each goodguess and see if its still
|
|
true after */
|
|
|
|
buf_incrpos(ses.payload, 16); /* start after the cookie */
|
|
|
|
ses.newkeys = (struct key_context*)m_malloc(sizeof(struct key_context));
|
|
|
|
/* kex_algorithms */
|
|
algo = ses.buf_match_algo(ses.payload, sshkex, &goodguess);
|
|
allgood &= goodguess;
|
|
if (algo == NULL) {
|
|
erralgo = "kex";
|
|
goto error;
|
|
}
|
|
TRACE(("kex algo %s", algo->name))
|
|
ses.newkeys->algo_kex = algo->val;
|
|
|
|
/* server_host_key_algorithms */
|
|
algo = ses.buf_match_algo(ses.payload, sshhostkey, &goodguess);
|
|
allgood &= goodguess;
|
|
if (algo == NULL) {
|
|
erralgo = "hostkey";
|
|
goto error;
|
|
}
|
|
TRACE(("hostkey algo %s", algo->name))
|
|
ses.newkeys->algo_hostkey = algo->val;
|
|
|
|
/* encryption_algorithms_client_to_server */
|
|
c2s_cipher_algo = ses.buf_match_algo(ses.payload, sshciphers, &goodguess);
|
|
if (c2s_cipher_algo == NULL) {
|
|
erralgo = "enc c->s";
|
|
goto error;
|
|
}
|
|
TRACE(("enc c2s is %s", c2s_cipher_algo->name))
|
|
|
|
/* encryption_algorithms_server_to_client */
|
|
s2c_cipher_algo = ses.buf_match_algo(ses.payload, sshciphers, &goodguess);
|
|
if (s2c_cipher_algo == NULL) {
|
|
erralgo = "enc s->c";
|
|
goto error;
|
|
}
|
|
TRACE(("enc s2c is %s", s2c_cipher_algo->name))
|
|
|
|
/* mac_algorithms_client_to_server */
|
|
c2s_hash_algo = ses.buf_match_algo(ses.payload, sshhashes, &goodguess);
|
|
if (c2s_hash_algo == NULL) {
|
|
erralgo = "mac c->s";
|
|
goto error;
|
|
}
|
|
TRACE(("hash c2s is %s", c2s_hash_algo->name))
|
|
|
|
/* mac_algorithms_server_to_client */
|
|
s2c_hash_algo = ses.buf_match_algo(ses.payload, sshhashes, &goodguess);
|
|
if (s2c_hash_algo == NULL) {
|
|
erralgo = "mac s->c";
|
|
goto error;
|
|
}
|
|
TRACE(("hash s2c is %s", s2c_hash_algo->name))
|
|
|
|
/* compression_algorithms_client_to_server */
|
|
c2s_comp_algo = ses.buf_match_algo(ses.payload, ses.compress_algos, &goodguess);
|
|
if (c2s_comp_algo == NULL) {
|
|
erralgo = "comp c->s";
|
|
goto error;
|
|
}
|
|
TRACE(("hash c2s is %s", c2s_comp_algo->name))
|
|
|
|
/* compression_algorithms_server_to_client */
|
|
s2c_comp_algo = ses.buf_match_algo(ses.payload, ses.compress_algos, &goodguess);
|
|
if (s2c_comp_algo == NULL) {
|
|
erralgo = "comp s->c";
|
|
goto error;
|
|
}
|
|
TRACE(("hash s2c is %s", s2c_comp_algo->name))
|
|
|
|
/* languages_client_to_server */
|
|
buf_eatstring(ses.payload);
|
|
|
|
/* languages_server_to_client */
|
|
buf_eatstring(ses.payload);
|
|
|
|
/* first_kex_packet_follows */
|
|
if (buf_getbool(ses.payload)) {
|
|
ses.kexstate.firstfollows = 1;
|
|
/* if the guess wasn't good, we ignore the packet sent */
|
|
if (!allgood) {
|
|
ses.ignorenext = 1;
|
|
}
|
|
}
|
|
|
|
/* Handle the asymmetry */
|
|
if (IS_DROPBEAR_CLIENT) {
|
|
ses.newkeys->recv.algo_crypt =
|
|
(struct dropbear_cipher*)s2c_cipher_algo->data;
|
|
ses.newkeys->trans.algo_crypt =
|
|
(struct dropbear_cipher*)c2s_cipher_algo->data;
|
|
ses.newkeys->recv.crypt_mode =
|
|
(struct dropbear_cipher_mode*)s2c_cipher_algo->mode;
|
|
ses.newkeys->trans.crypt_mode =
|
|
(struct dropbear_cipher_mode*)c2s_cipher_algo->mode;
|
|
ses.newkeys->recv.algo_mac =
|
|
(struct dropbear_hash*)s2c_hash_algo->data;
|
|
ses.newkeys->trans.algo_mac =
|
|
(struct dropbear_hash*)c2s_hash_algo->data;
|
|
ses.newkeys->recv.algo_comp = s2c_comp_algo->val;
|
|
ses.newkeys->trans.algo_comp = c2s_comp_algo->val;
|
|
} else {
|
|
/* SERVER */
|
|
ses.newkeys->recv.algo_crypt =
|
|
(struct dropbear_cipher*)c2s_cipher_algo->data;
|
|
ses.newkeys->trans.algo_crypt =
|
|
(struct dropbear_cipher*)s2c_cipher_algo->data;
|
|
ses.newkeys->recv.crypt_mode =
|
|
(struct dropbear_cipher_mode*)c2s_cipher_algo->mode;
|
|
ses.newkeys->trans.crypt_mode =
|
|
(struct dropbear_cipher_mode*)s2c_cipher_algo->mode;
|
|
ses.newkeys->recv.algo_mac =
|
|
(struct dropbear_hash*)c2s_hash_algo->data;
|
|
ses.newkeys->trans.algo_mac =
|
|
(struct dropbear_hash*)s2c_hash_algo->data;
|
|
ses.newkeys->recv.algo_comp = c2s_comp_algo->val;
|
|
ses.newkeys->trans.algo_comp = s2c_comp_algo->val;
|
|
}
|
|
|
|
/* reserved for future extensions */
|
|
buf_getint(ses.payload);
|
|
return;
|
|
|
|
error:
|
|
dropbear_exit("No matching algo %s", erralgo);
|
|
}
|