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Add support for certificate key types for users and hosts.

OpenSSH certificate key types are not X.509 certificates, but a much
simpler format that encodes a public key, identity information and
some validity constraints and signs it with a CA key. CA keys are
regular SSH keys. This certificate style avoids the attack surface
of X.509 certificates and is very easy to deploy.

Certified host keys allow automatic acceptance of new host keys
when a CA certificate is marked as trusted in ~/.ssh/known_hosts.
see VERIFYING HOST KEYS in ssh(1) for details.

Certified user keys allow authentication of users when the signing
CA key is marked as trusted in authorized_keys. See "AUTHORIZED_KEYS
FILE FORMAT" in sshd(8) for details.

Certificates are minted using ssh-keygen(1), documentation is in
the "CERTIFICATES" section of that manpage.

Documentation on the format of certificates is in the file
PROTOCOL.certkeys

feedback and ok markus@

/* $OpenBSD: auth.h,v 1.64 2010/02/26 20:29:54 djm Exp $ */

/*
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef AUTH_H
#define AUTH_H

#include <signal.h>

#include <openssl/rsa.h>

#include <bsd_auth.h>
#ifdef KRB5
#include <krb5.h>
#endif

typedef struct Authctxt Authctxt;
typedef struct Authmethod Authmethod;
typedef struct KbdintDevice KbdintDevice;

struct Authctxt {
	sig_atomic_t	 success;
	int		 authenticated;	/* authenticated and alarms cancelled */
	int		 postponed;	/* authentication needs another step */
	int		 valid;		/* user exists and is allowed to login */
	int		 attempt;
	int		 failures;
	int		 force_pwchange;
	char		*user;		/* username sent by the client */
	char		*service;
	struct passwd	*pw;		/* set if 'valid' */
	char		*style;
	void		*kbdintctxt;
	void		*jpake_ctx;
	auth_session_t	*as;
#ifdef KRB5
	krb5_context	 krb5_ctx;
	krb5_ccache	 krb5_fwd_ccache;
	krb5_principal	 krb5_user;
	char		*krb5_ticket_file;
#endif
	void		*methoddata;
};
/*
 * Every authentication method has to handle authentication requests for
 * non-existing users, or for users that are not allowed to login. In this
 * case 'valid' is set to 0, but 'user' points to the username requested by
 * the client.
 */

struct Authmethod {
	char	*name;
	int	(*userauth)(Authctxt *authctxt);
	int	*enabled;
};

/*
 * Keyboard interactive device:
 * init_ctx	returns: non NULL upon success
 * query	returns: 0 - success, otherwise failure
 * respond	returns: 0 - success, 1 - need further interaction,
 *		otherwise - failure
 */
struct KbdintDevice
{
	const char *name;
	void*	(*init_ctx)(Authctxt*);
	int	(*query)(void *ctx, char **name, char **infotxt,
		    u_int *numprompts, char ***prompts, u_int **echo_on);
	int	(*respond)(void *ctx, u_int numresp, char **responses);
	void	(*free_ctx)(void *ctx);
};

int      auth_rhosts(struct passwd *, const char *);
int
auth_rhosts2(struct passwd *, const char *, const char *, const char *);

int	 auth_rhosts_rsa(Authctxt *, char *, Key *);
int      auth_password(Authctxt *, const char *);
int      auth_rsa(Authctxt *, BIGNUM *);
int      auth_rsa_challenge_dialog(Key *);
BIGNUM	*auth_rsa_generate_challenge(Key *);
int	 auth_rsa_verify_response(Key *, BIGNUM *, u_char[]);
int	 auth_rsa_key_allowed(struct passwd *, BIGNUM *, Key **);

int	 auth_rhosts_rsa_key_allowed(struct passwd *, char *, char *, Key *);
int	 hostbased_key_allowed(struct passwd *, const char *, char *, Key *);
int	 user_key_allowed(struct passwd *, Key *);

#ifdef KRB5
int	auth_krb5(Authctxt *authctxt, krb5_data *auth, char **client, krb5_data *);
int	auth_krb5_tgt(Authctxt *authctxt, krb5_data *tgt);
int	auth_krb5_password(Authctxt *authctxt, const char *password);
void	krb5_cleanup_proc(Authctxt *authctxt);
#endif /* KRB5 */

void	do_authentication(Authctxt *);
void	do_authentication2(Authctxt *);

void	auth_log(Authctxt *, int, char *, char *);
void	userauth_finish(Authctxt *, int, char *);
int	auth_root_allowed(char *);

char	*auth2_read_banner(void);

void	privsep_challenge_enable(void);

int	auth2_challenge(Authctxt *, char *);
void	auth2_challenge_stop(Authctxt *);
int	bsdauth_query(void *, char **, char **, u_int *, char ***, u_int **);
int	bsdauth_respond(void *, u_int, char **);
int	skey_query(void *, char **, char **, u_int *, char ***, u_int **);
int	skey_respond(void *, u_int, char **);

void	auth2_jpake_get_pwdata(Authctxt *, BIGNUM **, char **, char **);
void	auth2_jpake_stop(Authctxt *);

int	allowed_user(struct passwd *);
struct passwd * getpwnamallow(const char *user);

char	*get_challenge(Authctxt *);
int	verify_response(Authctxt *, const char *);

char	*authorized_keys_file(struct passwd *);
char	*authorized_keys_file2(struct passwd *);

FILE	*auth_openkeyfile(const char *, struct passwd *, int);

HostStatus
check_key_in_hostfiles(struct passwd *, Key *, const char *,
    const char *, const char *);

/* hostkey handling */
Key	*get_hostkey_by_index(int);
Key	*get_hostkey_public_by_type(int);
Key	*get_hostkey_private_by_type(int);
int	 get_hostkey_index(Key *);
int	 ssh1_session_key(BIGNUM *);

/* debug messages during authentication */
void	 auth_debug_add(const char *fmt,...) __attribute__((format(printf, 1, 2)));
void	 auth_debug_send(void);
void	 auth_debug_reset(void);

struct passwd *fakepw(void);

#define AUTH_FAIL_MSG "Too many authentication failures for %.100s"

#endif