view auth.h @ 1715:3974f087d9c0

Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 8a485389330f
children bf1912d2d6e9
line wrap: on
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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. */

#ifndef DROPBEAR_AUTH_H_
#define DROPBEAR_AUTH_H_

#include "includes.h"
#include "signkey.h"
#include "chansession.h"

void svr_authinitialise(void);
void cli_authinitialise(void);

/* Server functions */
void recv_msg_userauth_request(void);
void send_msg_userauth_failure(int partial, int incrfail);
void send_msg_userauth_success(void);
void send_msg_userauth_banner(const buffer *msg);
void svr_auth_password(int valid_user);
void svr_auth_pubkey(int valid_user);
void svr_auth_pam(int valid_user);

#if DROPBEAR_SVR_PUBKEY_OPTIONS_BUILT
int svr_pubkey_allows_agentfwd(void);
int svr_pubkey_allows_tcpfwd(void);
int svr_pubkey_allows_x11fwd(void);
int svr_pubkey_allows_pty(void);
void svr_pubkey_set_forced_command(struct ChanSess *chansess);
void svr_pubkey_options_cleanup(void);
int svr_add_pubkey_options(buffer *options_buf, int line_num, const char* filename);
#else
/* no option : success */
#define svr_pubkey_allows_agentfwd() 1
#define svr_pubkey_allows_tcpfwd() 1
#define svr_pubkey_allows_x11fwd() 1
#define svr_pubkey_allows_pty() 1
static inline void svr_pubkey_set_forced_command(struct ChanSess *chansess) { }
static inline void svr_pubkey_options_cleanup(void) { }
#define svr_add_pubkey_options(x,y,z) DROPBEAR_SUCCESS
#endif

/* Client functions */
void recv_msg_userauth_failure(void);
void recv_msg_userauth_success(void);
void recv_msg_userauth_specific_60(void);
void recv_msg_userauth_pk_ok(void);
void recv_msg_userauth_info_request(void);
void cli_get_user(void);
void cli_auth_getmethods(void);
int cli_auth_try(void);
void recv_msg_userauth_banner(void);
void cli_pubkeyfail(void);
void cli_auth_password(void);
int cli_auth_pubkey(void);
void cli_auth_interactive(void);
char* getpass_or_cancel(const char* prompt);
void cli_auth_pubkey_cleanup(void);


#define MAX_USERNAME_LEN 100 /* arbitrary for the moment */

#define AUTH_TYPE_NONE      1
#define AUTH_TYPE_PUBKEY    (1 << 1)
#define AUTH_TYPE_PASSWORD  (1 << 2)
#define AUTH_TYPE_INTERACT  (1 << 3)

#define AUTH_METHOD_NONE "none"
#define AUTH_METHOD_NONE_LEN 4
#define AUTH_METHOD_PUBKEY "publickey"
#define AUTH_METHOD_PUBKEY_LEN 9
#define AUTH_METHOD_PASSWORD "password"
#define AUTH_METHOD_PASSWORD_LEN 8
#define AUTH_METHOD_INTERACT "keyboard-interactive"
#define AUTH_METHOD_INTERACT_LEN 20



/* This structure is shared between server and client - it contains
 * relatively little extraneous bits when used for the client rather than the
 * server */
struct AuthState {
	char *username; /* This is the username the client presents to check. It
					   is updated each run through, used for auth checking */
	unsigned char authtypes; /* Flags indicating which auth types are still 
								valid */
	unsigned int failcount; /* Number of (failed) authentication attempts.*/
	unsigned int authdone; /* 0 if we haven't authed, 1 if we have. Applies for
							  client and server (though has differing 
							  meanings). */

	unsigned int perm_warn; /* Server only, set if bad permissions on 
							   ~/.ssh/authorized_keys have already been
							   logged. */
	unsigned int checkusername_failed;  /* Server only, set if checkusername
	                                has already failed */
	struct timespec auth_starttime; /* Server only, time of receiving current 
									SSH_MSG_USERAUTH_REQUEST */

	/* These are only used for the server */
	uid_t pw_uid;
	gid_t pw_gid;
	char *pw_dir;
	char *pw_shell;
	char *pw_name;
	char *pw_passwd;
#if DROPBEAR_SVR_PUBKEY_OPTIONS_BUILT
	struct PubKeyOptions* pubkey_options;
#endif
};

#if DROPBEAR_SVR_PUBKEY_OPTIONS_BUILT
struct PubKeyOptions;
struct PubKeyOptions {
	/* Flags */
	int no_port_forwarding_flag;
	int no_agent_forwarding_flag;
	int no_x11_forwarding_flag;
	int no_pty_flag;
	/* "command=" option. */
	char * forced_command;
};
#endif

#endif /* DROPBEAR_AUTH_H_ */