/*
 * chap.h - New CHAP implementation.
 *
 * Copyright (c) 2003-2024 Paul Mackerras. 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.
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef PPP_CHAP_NEW_H
#define PPP_CHAP_NEW_H

#include "pppdconf.h"

#ifdef  __cplusplus
extern "C" {
#endif

/*
 * CHAP packets begin with a standard header with code, id, len (2 bytes).
 */
#define CHAP_HDRLEN	4

/*
 * Values for the code field.
 */
#define CHAP_CHALLENGE	1
#define CHAP_RESPONSE	2
#define CHAP_SUCCESS	3
#define CHAP_FAILURE	4

/*
 * CHAP digest codes.
 */
#define CHAP_MD5		5
#define CHAP_MICROSOFT		0x80
#define CHAP_MICROSOFT_V2	0x81

/*
 * Semi-arbitrary limits on challenge and response fields.
 */
#define MAX_CHALLENGE_LEN	64
#define MAX_RESPONSE_LEN	64

/* bitmask of supported algorithms */
#define MDTYPE_MICROSOFT_V2	0x1
#define MDTYPE_MICROSOFT	0x2
#define MDTYPE_MD5		0x4
#define MDTYPE_NONE		0

/* hashes supported by this instance of pppd */
extern int chap_mdtype_all;

/* Return the digest alg. ID for the most preferred digest type. */
#define CHAP_DIGEST(mdtype) \
    ((mdtype) & MDTYPE_MD5)? CHAP_MD5: \
    ((mdtype) & MDTYPE_MICROSOFT_V2)? CHAP_MICROSOFT_V2: \
    ((mdtype) & MDTYPE_MICROSOFT)? CHAP_MICROSOFT: \
    0

/* Return the bit flag (lsb set) for our most preferred digest type. */
#define CHAP_MDTYPE(mdtype) ((mdtype) ^ ((mdtype) - 1)) & (mdtype)

/* Return the bit flag for a given digest algorithm ID. */
#define CHAP_MDTYPE_D(digest) \
    ((digest) == CHAP_MICROSOFT_V2)? MDTYPE_MICROSOFT_V2: \
    ((digest) == CHAP_MICROSOFT)? MDTYPE_MICROSOFT: \
    ((digest) == CHAP_MD5)? MDTYPE_MD5: \
    0

/* Can we do the requested digest? */
#define CHAP_CANDIGEST(mdtype, digest) \
    ((digest) == CHAP_MICROSOFT_V2)? (mdtype) & MDTYPE_MICROSOFT_V2: \
    ((digest) == CHAP_MICROSOFT)? (mdtype) & MDTYPE_MICROSOFT: \
    ((digest) == CHAP_MD5)? (mdtype) & MDTYPE_MD5: \
    0


/*
 * The code for each digest type has to supply one of these.
 */
struct chap_digest_type {
	int code;

	/*
	 * Note: challenge and response arguments below are formatted as
	 * a length byte followed by the actual challenge/response data.
	 */
	void (*generate_challenge)(unsigned char *challenge);
	int (*verify_response)(int id, char *name,
		unsigned char *secret, int secret_len,
		unsigned char *challenge, unsigned char *response,
		char *message, int message_space);
	void (*make_response)(unsigned char *response, int id, char *our_name,
		unsigned char *challenge, char *secret, int secret_len,
		unsigned char *priv);
	int (*check_success)(int id, unsigned char *pkt, int len);
	void (*handle_failure)(unsigned char *pkt, int len);

	struct chap_digest_type *next;
};

/*
 * This function will return a value of 1 to indicate that a plugin intend to supply
 *   a username or a password to pppd through the chap_passwd_hook callback.
 *
 * Return a value > 0 to avoid parsing the chap-secrets file.
 */
typedef int (chap_check_hook_fn)(void);
extern chap_check_hook_fn *chap_check_hook;

/*
 * A plugin can chose to supply its own user and password overriding whatever
 *   has been provided by the configuration. Hook is only valid when pppd is
 *   acting as a client.
 *
 * The maximum size of the user argument is always MAXNAMELEN
 * The length of the password is always MAXWORDLEN, however; secrets can't be
 *   longer than MAXSECRETLEN
 *
 * Return a value < 0 to fail the connection.
 */
typedef int (chap_passwd_hook_fn)(char *user, char *password);
extern chap_passwd_hook_fn *chap_passwd_hook;

/*
 * A plugin can chose to replace the default chap_verify_response function with
 *   one of their own.
 */
typedef int (chap_verify_hook_fn)(char *name, char *ourname, int id,
			struct chap_digest_type *digest,
			unsigned char *challenge, unsigned char *response,
			char *message, int message_space);
extern chap_verify_hook_fn *chap_verify_hook;

/* Called by digest code to register a digest type */
extern void chap_register_digest(struct chap_digest_type *);

/* Lookup a digest handler by type */
extern struct chap_digest_type *chap_find_digest(int digest_code);

/* Called by authentication code to start authenticating the peer. */
extern void chap_auth_peer(int unit, char *our_name, int digest_code);

/* Called by auth. code to start authenticating us to the peer. */
extern void chap_auth_with_peer(int unit, char *our_name, int digest_code);

/* Represents the CHAP protocol to the main pppd code */
extern struct protent chap_protent;

#ifdef  __cplusplus
}
#endif

#endif // PPP_CHAP_NEW_H