release/src/router/dropbear/svr-authpasswd.c

   1 /*
   2  * Dropbear - a SSH2 server
   3  *
   4  * Copyright (c) 2002,2003 Matt Johnston
   5  * All rights reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE. */
  24
  25 /* Validates a user password */
  26
  27 #include "includes.h"
  28 #include "session.h"
  29 #include "buffer.h"
  30 #include "dbutil.h"
  31 #include "auth.h"
  32 #include "runopts.h"
  33
  34 #ifdef ENABLE_SVR_PASSWORD_AUTH
  35
  36 /* not constant time when strings are differing lengths.
  37  string content isn't leaked, and crypt hashes are predictable length. */
  38 static int constant_time_strcmp(const char* a, const char* b) {
  39         size_t la = strlen(a);
  40         size_t lb = strlen(b);
  41
  42         if (la != lb) {
  43                 return 1;
  44         }
  45
  46         return constant_time_memcmp(a, b, la);
  47 }
  48
  49 /* Process a password auth request, sending success or failure messages as
  50  * appropriate */
  51 void svr_auth_password() {
  52
  53         char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
  54         char * testcrypt = NULL; /* crypt generated from the user's password sent */
  55         char * password;
  56         unsigned int passwordlen;
  57
  58         unsigned int changepw;
  59
  60         passwdcrypt = ses.authstate.pw_passwd;
  61
  62 #ifdef DEBUG_HACKCRYPT
  63         /* debugging crypt for non-root testing with shadows */
  64         passwdcrypt = DEBUG_HACKCRYPT;
  65 #endif
  66
  67         /* check if client wants to change password */
  68         changepw = buf_getbool(ses.payload);
  69         if (changepw) {
  70                 /* not implemented by this server */
  71                 send_msg_userauth_failure(0, 1);
  72                 return;
  73         }
  74
  75         password = buf_getstring(ses.payload, &passwordlen);
  76
  77         /* the first bytes of passwdcrypt are the salt */
  78         testcrypt = crypt(password, passwdcrypt);
  79         m_burn(password, passwordlen);
  80         m_free(password);
  81
  82         if (testcrypt == NULL) {
  83                 /* crypt() with an invalid salt like "!!" */
  84                 dropbear_log(LOG_WARNING, "User account '%s' is locked",
  85                                 ses.authstate.pw_name);
  86                 send_msg_userauth_failure(0, 1);
  87                 return;
  88         }
  89
  90         /* check for empty password */
  91         if (passwdcrypt[0] == '\0') {
  92                 dropbear_log(LOG_WARNING, "User '%s' has blank password, rejected",
  93                                 ses.authstate.pw_name);
  94                 send_msg_userauth_failure(0, 1);
  95                 return;
  96         }
  97
  98         if (constant_time_strcmp(testcrypt, passwdcrypt) == 0) {
  99                 /* successful authentication */
 100                 dropbear_log(LOG_NOTICE,
 101                                 "Password auth succeeded for '%s' from %s",
 102                                 ses.authstate.pw_name,
 103                                 svr_ses.addrstring);
 104                 send_msg_userauth_success();
 105         } else {
 106                 dropbear_log(LOG_WARNING,
 107                                 "Bad password attempt for '%s' from %s",
 108                                 ses.authstate.pw_name,
 109                                 svr_ses.addrstring);
 110                 send_msg_userauth_failure(0, 1);
 111         }
 112 }
 113
 114 #endif