view svr-authpasswd.c @ 1631:292f79307600

fix some gcc warnings (#73) * tweak string size fix gcc8 warnings ``` svr-agentfwd.c: In function 'bindagent': svr-agentfwd.c:254:53: warning: '%s' directive output may be truncated writing up to 107 bytes into a region of size between 0 and 107 [-Wformat-truncation=] snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", path, sockfile); ^~ ~~~~~~~~ svr-agentfwd.c:254:2: note: 'snprintf' output between 2 and 216 bytes into a destination of size 108 snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", path, sockfile); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` * cleanup signed/unsigned comparison fix gcc8 warnings ``` scp.c: In function 'do_local_cmd': scp.c:132:17: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] for (i = 0; i < a->num; i++) ^ scpmisc.c: In function 'addargs': scpmisc.c:161:25: warning: comparison of integer expressions of different signedness: 'int' and 'u_int' {aka 'unsigned int'} [-Wsign-compare] } else if (args->num+2 >= nalloc) ^~ scpmisc.c: In function 'replacearg': scpmisc.c:183:12: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] if (which >= args->num) ^~ scpmisc.c: In function 'freeargs': scpmisc.c:196:17: warning: comparison of integer expressions of different signedness: 'u_int' {aka 'unsigned int'} and 'int' [-Wsign-compare] for (i = 0; i < args->num; i++) ^ ``` see https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/misc.h.diff?r1=1.16&r2=1.17
author François Perrad <francois.perrad@gadz.org>
date Wed, 20 Mar 2019 15:25:15 +0100
parents 5d2d1021ca00
children 228b086794b7
line wrap: on
line source

/*
 * 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"

#if DROPBEAR_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(int valid_user) {
	
	char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
	char * testcrypt = NULL; /* crypt generated from the user's password sent */
	char * password = NULL;
	unsigned int passwordlen;
	unsigned int changepw;

	/* 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);
	if (valid_user) {
		/* the first bytes of passwdcrypt are the salt */
		passwdcrypt = ses.authstate.pw_passwd;
		testcrypt = crypt(password, passwdcrypt);
	}
	m_burn(password, passwordlen);
	m_free(password);

	/* After we have got the payload contents we can exit if the username
	is invalid. Invalid users have already been logged. */
	if (!valid_user) {
		send_msg_userauth_failure(0, 1);
		return;
	}

	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