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/*
* Dropbear - a SSH2 server
*
* Copyright (c) 2002,2003 Matt Johnston
* 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. */
/* Validates a user password */
#include "includes.h"
#include "session.h"
#include "buffer.h"
#include "dbutil.h"
#include "auth.h"
#include "runopts.h"
#ifdef ENABLE_SVR_PASSWORD_AUTH
/* not constant time when strings are differing lengths.
string content isn't leaked, and crypt hashes are predictable length. */
static int constant_time_strcmp(const char* a, const char* b) {
size_t la = strlen(a);
size_t lb = strlen(b);
if (la != lb) {
return 1;
}
return constant_time_memcmp(a, b, la);
}
/* Process a password auth request, sending success or failure messages as
* appropriate */
void svr_auth_password() {
char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
char * testcrypt = NULL; /* crypt generated from the user's password sent */
char * password;
unsigned int passwordlen;
unsigned int changepw;
passwdcrypt = ses.authstate.pw_passwd;
#ifdef DEBUG_HACKCRYPT
/* debugging crypt for non-root testing with shadows */
passwdcrypt = DEBUG_HACKCRYPT;
#endif
/* check if client wants to change password */
changepw = buf_getbool(ses.payload);
if (changepw) {
/* not implemented by this server */
send_msg_userauth_failure(0, 1);
return;
}
password = buf_getstring(ses.payload, &passwordlen);
/* the first bytes of passwdcrypt are the salt */
testcrypt = crypt(password, passwdcrypt);
m_burn(password, passwordlen);
m_free(password);
if (testcrypt == NULL) {
/* crypt() with an invalid salt like "!!" */
dropbear_log(LOG_WARNING, "User account '%s' is locked",
ses.authstate.pw_name);
send_msg_userauth_failure(0, 1);
return;
}
/* check for empty password */
if (passwdcrypt[0] == '\0') {
dropbear_log(LOG_WARNING, "User '%s' has blank password, rejected",
ses.authstate.pw_name);
send_msg_userauth_failure(0, 1);
return;
}
if (constant_time_strcmp(testcrypt, passwdcrypt) == 0) {
/* successful authentication */
dropbear_log(LOG_NOTICE,
"Password auth succeeded for '%s' from %s",
ses.authstate.pw_name,
svr_ses.addrstring);
send_msg_userauth_success();
} else {
dropbear_log(LOG_WARNING,
"Bad password attempt for '%s' from %s",
ses.authstate.pw_name,
svr_ses.addrstring);
send_msg_userauth_failure(0, 1);
}
}
#endif
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