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annotate svr-kex.c @ 533:805ae74ec024

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Encrypt in-place, avoid an extra malloc
author Matt Johnston <matt@ucc.asn.au>
date Sun, 01 Mar 2009 14:38:25 +0000
parents 454a34b2dfd1
children 3aa74a4d83ae 76097ec1a29a
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1 /*
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2 * Dropbear - a SSH2 server
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3 *
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4 * Copyright (c) 2002,2003 Matt Johnston
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5 * Copyright (c) 2004 by Mihnea Stoenescu
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6 * All rights reserved.
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7 *
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8 * Permission is hereby granted, free of charge, to any person obtaining a copy
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9 * of this software and associated documentation files (the "Software"), to deal
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10 * in the Software without restriction, including without limitation the rights
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11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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12 * copies of the Software, and to permit persons to whom the Software is
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13 * furnished to do so, subject to the following conditions:
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14 *
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15 * The above copyright notice and this permission notice shall be included in
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16 * all copies or substantial portions of the Software.
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17 *
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18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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24 * SOFTWARE. */
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25
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26 #include "includes.h"
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27 #include "dbutil.h"
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28 #include "algo.h"
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29 #include "buffer.h"
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30 #include "session.h"
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31 #include "kex.h"
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32 #include "ssh.h"
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33 #include "packet.h"
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34 #include "bignum.h"
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35 #include "random.h"
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36 #include "runopts.h"
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39 static void send_msg_kexdh_reply(mp_int *dh_e);
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40
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41 /* Handle a diffie-hellman key exchange initialisation. This involves
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42 * calculating a session key reply value, and corresponding hash. These
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43 * are carried out by send_msg_kexdh_reply(). recv_msg_kexdh_init() calls
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44 * that function, then brings the new keys into use */
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45 void recv_msg_kexdh_init() {
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46
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47 DEF_MP_INT(dh_e);
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49 TRACE(("enter recv_msg_kexdh_init"))
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50 if (!ses.kexstate.recvkexinit) {
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51 dropbear_exit("Premature kexdh_init message received");
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52 }
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54 m_mp_init(&dh_e);
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55 if (buf_getmpint(ses.payload, &dh_e) != DROPBEAR_SUCCESS) {
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56 dropbear_exit("Failed to get kex value");
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57 }
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59 send_msg_kexdh_reply(&dh_e);
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61 mp_clear(&dh_e);
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62
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63 send_msg_newkeys();
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64 ses.requirenext = SSH_MSG_NEWKEYS;
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65 TRACE(("leave recv_msg_kexdh_init"))
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66 }
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67
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68 /* Generate our side of the diffie-hellman key exchange value (dh_f), and
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69 * calculate the session key using the diffie-hellman algorithm. Following
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70 * that, the session hash is calculated, and signed with RSA or DSS. The
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71 * result is sent to the client.
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72 *
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73 * See the ietf-secsh-transport draft, section 6, for details */
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74 static void send_msg_kexdh_reply(mp_int *dh_e) {
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76 DEF_MP_INT(dh_y);
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77 DEF_MP_INT(dh_f);
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79 TRACE(("enter send_msg_kexdh_reply"))
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80 m_mp_init_multi(&dh_y, &dh_f, NULL);
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82 gen_kexdh_vals(&dh_f, &dh_y);
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84 kexdh_comb_key(&dh_f, &dh_y, dh_e, svr_opts.hostkey);
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85 mp_clear(&dh_y);
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87 /* we can start creating the kexdh_reply packet */
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88 CHECKCLEARTOWRITE();
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89 buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_REPLY);
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90 buf_put_pub_key(ses.writepayload, svr_opts.hostkey,
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91 ses.newkeys->algo_hostkey);
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93 /* put f */
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94 buf_putmpint(ses.writepayload, &dh_f);
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95 mp_clear(&dh_f);
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96
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97 /* calc the signature */
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98 buf_put_sign(ses.writepayload, svr_opts.hostkey,
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99 ses.newkeys->algo_hostkey, ses.hash, SHA1_HASH_SIZE);
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100
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101 /* the SSH_MSG_KEXDH_REPLY is done */
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102 encrypt_packet();
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103
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104 TRACE(("leave send_msg_kexdh_reply"))
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105 }
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106