Mercurial > dropbear

annotate svr-authpasswd.c @ 994:5c5ade336926

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Prefer stronger algorithms in algorithm negotiation. Prefer diffie-hellman-group14-sha1 (2048 bit) over diffie-hellman-group1-sha1 (1024 bit). Due to meet-in-the-middle attacks the effective key length of three key 3DES is 112 bits. AES is stronger and faster then 3DES. Prefer to delay the start of compression until after authentication has completed. This avoids exposing compression code to attacks from unauthenticated users. (github pull request #9)
author Fedor Brunner <fedor.brunner@azet.sk>
date Fri, 23 Jan 2015 23:00:25 +0800
parents a625f9e135a4
children 50f8a24953e6
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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 * All rights reserved.
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6 *
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7 * Permission is hereby granted, free of charge, to any person obtaining a copy
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8 * of this software and associated documentation files (the "Software"), to deal
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9 * in the Software without restriction, including without limitation the rights
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10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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11 * copies of the Software, and to permit persons to whom the Software is
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12 * furnished to do so, subject to the following conditions:
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13 *
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14 * The above copyright notice and this permission notice shall be included in
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15 * all copies or substantial portions of the Software.
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16 *
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17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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23 * SOFTWARE. */
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24
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25 /* Validates a user password */
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27 #include "includes.h"
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28 #include "session.h"
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29 #include "buffer.h"
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30 #include "dbutil.h"
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31 #include "auth.h"
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32 #include "runopts.h"
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34 #ifdef ENABLE_SVR_PASSWORD_AUTH
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36 static int constant_time_strcmp(const char* a, const char* b) {
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37 size_t la = strlen(a);
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38 size_t lb = strlen(b);
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40 if (la != lb) {
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41 return 1;
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42 }
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44 return constant_time_memcmp(a, b, la);
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45 }
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47 /* Process a password auth request, sending success or failure messages as
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48 * appropriate */
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49 void svr_auth_password() {
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51 char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
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52 char * testcrypt = NULL; /* crypt generated from the user's password sent */
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53 unsigned char * password;
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54 unsigned int passwordlen;
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56 unsigned int changepw;
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58 passwdcrypt = ses.authstate.pw_passwd;
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60 #ifdef DEBUG_HACKCRYPT
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61 /* debugging crypt for non-root testing with shadows */
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62 passwdcrypt = DEBUG_HACKCRYPT;
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63 #endif
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64
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65 /* check if client wants to change password */
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66 changepw = buf_getbool(ses.payload);
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67 if (changepw) {
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68 /* not implemented by this server */
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69 send_msg_userauth_failure(0, 1);
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70 return;
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71 }
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73 password = buf_getstring(ses.payload, &passwordlen);
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75 /* the first bytes of passwdcrypt are the salt */
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76 testcrypt = crypt((char*)password, passwdcrypt);
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77 m_burn(password, passwordlen);
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78 m_free(password);
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80 if (testcrypt == NULL) {
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81 /* crypt() with an invalid salt like "!!" */
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82 dropbear_log(LOG_WARNING, "User account '%s' is locked",
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83 ses.authstate.pw_name);
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84 send_msg_userauth_failure(0, 1);
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85 return;
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86 }
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87
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88 /* check for empty password */
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89 if (passwdcrypt[0] == '\0') {
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90 dropbear_log(LOG_WARNING, "User '%s' has blank password, rejected",
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91 ses.authstate.pw_name);
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92 send_msg_userauth_failure(0, 1);
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93 return;
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94 }
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95
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96 if (constant_time_strcmp(testcrypt, passwdcrypt) == 0) {
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97 /* successful authentication */
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98 dropbear_log(LOG_NOTICE,
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99 "Password auth succeeded for '%s' from %s",
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100 ses.authstate.pw_name,
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101 svr_ses.addrstring);
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102 send_msg_userauth_success();
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103 } else {
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104 dropbear_log(LOG_WARNING,
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105 "Bad password attempt for '%s' from %s",
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106 ses.authstate.pw_name,
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107 svr_ses.addrstring);
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108 send_msg_userauth_failure(0, 1);
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109 }
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110 }
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112 #endif