[tripe] / tripe.h

/* -*-c-*-
 *
 * $Id: tripe.h,v 1.2 2001/02/03 22:40:29 mdw Exp $
 *
 * Main header file for TrIPE
 *
 * (c) 2001 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * TrIPE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with TrIPE; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: tripe.h,v $
 * Revision 1.2  2001/02/03 22:40:29  mdw
 * Put timer information into the entropy pool when packets are received
 * and on similar events.  Reseed the generator on the interval timer.
 *
 * Revision 1.1  2001/02/03 20:26:37  mdw
 * Initial checkin.
 *
 */

#ifndef TRIPE_H
#define TRIPE_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <signal.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#include <pwd.h>
#include <grp.h>

#include <mLib/alloc.h>
#include <mLib/arena.h>
#include <mLib/bres.h>
#include <mLib/dstr.h>
#include <mLib/env.h>
#include <mLib/fdflags.h>
#include <mLib/fwatch.h>
#include <mLib/mdwopt.h>
#include <mLib/quis.h>
#include <mLib/report.h>
#include <mLib/sel.h>
#include <mLib/selbuf.h>
#include <mLib/sig.h>
#include <mLib/str.h>
#include <mLib/sub.h>
#include <mLib/trace.h>

#include <catacomb/gcipher.h>
#include <catacomb/gmac.h>
#include <catacomb/grand.h>
#include <catacomb/key.h>
#include <catacomb/paranoia.h>

#include <catacomb/blowfish.h>
#include <catacomb/blowfish-cbc.h>
#include <catacomb/noise.h>
#include <catacomb/rand.h>
#include <catacomb/rmd160.h>
#include <catacomb/rmd160-hmac.h>

#include <catacomb/mp.h>
#include <catacomb/mpmont.h>
#include <catacomb/mprand.h>
#include <catacomb/dh.h>

#include "util.h"

#undef sun

/*----- Magic numbers -----------------------------------------------------*/

/* --- Tunnel types --- */

#define TUN_NOTDEF 0
#define TUN_UNET 1
#define TUN_BSD 2

/* --- Trace flags --- */

#define T_TUNNEL 1u
#define T_PEER 2u
#define T_PACKET 4u
#define T_ADMIN 8u
#define T_CRYPTO 16u
#define T_KEYSET 32u
#define T_KEYEXCH 64u
#define T_KEYMGMT 128u

#define T_ALL 255u

/* --- Units --- */

#define SEC(n) (n##u)
#define MIN(n) (n##u * 60u)
#define MEG(n) (n##ul * 1024ul * 1024ul)

/* --- Other things --- */

#define PKBUFSZ 65536

/*----- TrIPE protocol ----------------------------------------------------*/

/* --- TrIPE packet format --- *
 *
 * A packet begins with a single-byte packet type.  The remaining data
 * depends on the packet type.
 */

#define MSG_PACKET 0u
/* Followed by a 64-bit MAC and an encrypted packet.  The MAC is used as an
 * IV for a 64-bit block cipher in CBC-stealing mode.
 */

#define MSG_PRECHALLENGE 1u
/* Followed by the challenge only.  Useful for bootstrapping the system.
 */

#define MSG_CHALLENGE 2u
/* Followed by a response hash and a large-integer challenge.
 */

#define MSG_RESPONSE 3u
/* Followed by a large-integer response.
 */

/*----- Data structures ---------------------------------------------------*/

/* --- Buffers --- *
 *
 * Buffers provide a simple stream-like interface for building and parsing
 * packets.
 */

typedef struct buf {
  octet *base, *p, *limit;		/* Pointers to the buffer */
  unsigned f;				/* Various flags */
} buf;

#define BF_BROKEN 1u			/* Buffer is broken */

/* --- Socket addresses --- *
 *
 * A magic union of supported socket addresses.
 */

typedef union addr {
  struct sockaddr sa;
  struct sockaddr_in sin;
} addr;

/* --- A symmetric keyset --- *
 *
 * A keyset contains a set of symmetric keys for encrypting and decrypting
 * packets.  Keysets are stored in a list, sorted in reverse order of
 * creation, so that the most recent keyset (the one most likely to be used)
 * is first.
 *
 * Each keyset has a time limit and a data limit.  The keyset is destroyed
 * when either it has existed for too long, or it has been used to encrypt
 * too much data.  New key exchanges are triggered when keys are close to
 * expiry.
 */

typedef struct keyset {
  struct keyset *next;			/* Next active keyset in the list */
  time_t t_exp;				/* Expiry time for this keyset */
  unsigned long sz_exp;			/* Data limit for the keyset */
#ifndef NTRACE
  unsigned seq;				/* Sequence number for tracing */
#endif
  gcipher *c;				/* Keyset cipher for encryption */
  gmac *m;				/* Keyset MAC for integrity */
} keyset;

/* --- Key exchange --- *
 *
 * TrIPE uses the Wrestlers Protocol for its key exchange.  The Wrestlers
 * Protocol has a number of desirable features (e.g., perfect forward
 * secrecy, and zero-knowledge authentication) which make it attractive for
 * use in TrIPE.  The Wrestlers Protocol was designed by Mark Wooding and
 * Clive Jones.
 */

typedef struct keyexch {
  keyset **ks;				/* Peer's list of keysets */
  struct peer *p;			/* Pointer back to the peer */
  unsigned f;				/* Various useful flags */
  sel_timer t;				/* Timer for next exchange */
  dh_pub kpub;				/* Peer's public key */
  mp *my_x, *my_gx, *my_gxy;		/* My half of the exchange */
  octet my_h[RMD160_HASHSZ];		/* My challenge hash */
  mp *your_gx, *your_gxy;		/* Your half of the exchange */
  octet your_h[RMD160_HASHSZ];		/* Your challenge hash */
  time_t t_valid;			/* When this exchange goes bad */
  time_t t_qchal, t_qresp;		/* Quiet timers for packet types */
  time_t t_newchal;			/* When to accept a new challenge */
} keyexch;

#define KXF_TIMER 1u			/* Waiting for a timer to go off */
#define KXF_INIT 2u			/* Big numbers are initialized */
#define KXF_MYH 4u			/* My hash has been computed */
#define KXF_YOURH 8u			/* Your hash has been received */
#define KXF_REPLY 16u			/* Received your response OK */
#define KXF_DONE 32u			/* Key exchange completed */

/* --- Tunnel structure --- *
 *
 * Used to maintain system-specific information about the tunnel interface.
 */

typedef struct tunnel {
#if TUN_TYPE == TUN_UNET
  sel_file f;				/* Selector for Usernet device */
  struct peer *p;			/* Pointer to my peer */
#else
#  error "No support for this tunnel type"
#endif
} tunnel;

/* --- Peer structure --- *
 *
 * The main structure which glues everything else together.
 */

typedef struct peer {
  struct peer *next, *prev;		/* Links to next and previous */
  char *name;				/* Name of this peer */
  tunnel t;				/* Tunnel for local packets */
  keyset *ks;				/* List head for keysets */
  keyexch kx;				/* Key exchange protocol block */
  buf b;				/* Buffer for sending packets */
  addr peer;				/* Peer socket address */
  size_t sasz;				/* Socket address size */
} peer;

/* --- Admin structure --- */

typedef struct admin {
  struct admin *next, *prev;		/* Links to next and previous */
  selbuf b;				/* Line buffer for commands */
  int fd;				/* File descriptor for output */
#ifndef NTRACE
  unsigned seq;				/* Sequence number for tracing */
#endif
  char *pname;				/* Peer name to create */
  char *paddr;				/* Address string to resolve */
  bres_client r;			/* Background resolver task */
  sel_timer t;				/* Timer for resolver */
  addr peer;				/* Address to set */
  size_t sasz;				/* Size of the address */
} admin;

/*----- Global variables --------------------------------------------------*/

extern sel_state sel;			/* Global I/O event state */
extern dh_priv kpriv;			/* Our private key */
extern mpmont mg;			/* Montgomery context for DH group */
extern octet buf_i[PKBUFSZ], buf_o[PKBUFSZ]; /* Big packet buffers */

#ifndef NTRACE
extern const trace_opt tr_opts[];	/* Trace options array */
extern unsigned tr_flags;		/* Trace options flags */
#endif

/*----- Other macros ------------------------------------------------------*/

#define TIMER noise_timer(RAND_GLOBAL)

/*----- Key management ----------------------------------------------------*/

/* --- @km_interval@ --- *
 *
 * Arguments:	---
 *
 * Returns:	Zero if OK, nonzero to force reloading of keys.
 *
 * Use:		Called on the interval timer to perform various useful jobs.
 */

extern int km_interval(void);

/* --- @km_init@ --- *
 *
 * Arguments:	@const char *kr_priv@ = private keyring file
 *		@const char *kr_pub@ = public keyring file
 *		@const char *tag@ = tag to load
 *
 * Returns:	---
 *
 * Use:		Initializes, and loads the private key.
 */

extern void km_init(const char */*kr_priv*/, const char */*kr_pub*/,
		    const char */*tag*/);

/* --- @km_getpubkey@ --- *
 *
 * Arguments:	@const char *tag@ = public key tag to load
 *		@dh_pub *kpub@ = where to put the public key
 *
 * Returns:	Zero if OK, nonzero if it failed.
 *
 * Use:		Fetches a public key from the keyring.
 */

extern int km_getpubkey(const char */*tag*/, dh_pub */*kpub*/);

/*----- Key exchange ------------------------------------------------------*/

/* --- @kx_start@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *
 * Returns:	---
 *
 * Use:		Stimulates a key exchange.  If a key exchage is in progress,
 *		a new challenge is sent (unless the quiet timer forbids
 *		this); if no exchange is in progress, one is commenced.
 */

extern void kx_start(keyexch */*kx*/);

/* --- @kx_prechallenge@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exhange context
 *		@buf *b@ = pointer to buffer containing the packet
 *
 * Returns:	---
 *
 * Use:		Reads a prechallenge packet from the buffer and handles it.
 */

extern void kx_prechallenge(keyexch */*kx*/, buf */*b*/);

/* --- @kx_challenge@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *		@buf *b@ = a buffer containing the packet to read
 *
 * Returns:	---
 *
 * Use:		Reads a challenge from the buffer and handles it.
 */

extern void kx_challenge(keyexch */*kx*/, buf */*b*/);

/* --- @kx_response@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *		@buf *b@ = a buffer containing the packet to read
 *
 * Returns:	---
 *
 * Use:		Reads a response from the buffer and handles it.
 */

extern void kx_response(keyexch */*kx*/, buf */*b*/);

/* --- @kx_free@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *
 * Returns:	---
 *
 * Use:		Frees everything in a key exchange context.
 */

extern void kx_free(keyexch */*kx*/);

/* --- @kx_newkeys@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *
 * Returns:	---
 *
 * Use:		Informs the key exchange module that its keys may have
 *		changed.  If fetching the new keys fails, the peer will be
 *		destroyed, we log messages and struggle along with the old
 *		keys.
 */

extern void kx_newkeys(keyexch */*kx*/);

/* --- @kx_init@ --- *
 *
 * Arguments:	@keyexch *kx@ = pointer to key exchange context
 *		@peer *p@ = pointer to peer context
 *		@keyset **ks@ = pointer to keyset list
 *
 * Returns:	Zero if OK, nonzero if it failed.
 *
 * Use:		Initializes a key exchange module.  The module currently
 *		contains no keys, and will attempt to initiate a key
 *		exchange.
 */

extern int kx_init(keyexch */*kx*/, peer */*p*/, keyset **/*ks*/);

/*----- Keysets and symmetric cryptography --------------------------------*/

/* --- @ks_free@ --- *
 *
 * Arguments:	@keyset **ksroot@ = pointer to keyset list head
 *
 * Returns:	---
 *
 * Use:		Frees all of the keys in a keyset.
 */

extern void ks_free(keyset **/*ksroot*/);

/* --- @ks_prune@ --- *
 *
 * Arguments:	@keyset **ksroot@ = pointer to keyset list head
 *
 * Returns:	---
 *
 * Use:		Prunes the keyset list by removing keys which mustn't be used
 *		any more.
 */

extern void ks_prune(keyset **/*ksroot*/);

/* --- @ks_gen@ --- *
 *
 * Arguments:	@keyset **ksroot@ = pointer to keyset list head
 *		@const void *k@ = pointer to key material
 *		@size_t sz@ = size of the key material
 *
 * Returns:	The regeneration time for the new key.
 *
 * Use:		Derives a keyset from the given key material and adds it to
 *		the list.
 */

extern time_t ks_gen(keyset **/*ksroot*/, const void */*k*/, size_t /*sz*/);

/* --- @ks_encrypt@ --- *
 *
 * Arguments:	@keyset **ksroot@ = pointer to keyset list head
 *		@buf *b@ = pointer to input buffer
 *		@buf *bb@ = pointer to output buffer
 *
 * Returns:	Nonzero if a new key is needed.
 *
 * Use:		Encrypts a packet.
 */

extern int ks_encrypt(keyset **/*ksroot*/, buf */*b*/, buf */*bb*/);

/* --- @ks_decrypt@ --- *
 *
 * Arguments:	@keyset **ksroot@ = pointer to keyset list head
 *		@buf *b@ = pointer to input buffer
 *		@buf *bb@ = pointer to output buffer
 *
 * Returns:	Nonzero if the packet couldn't be decrypted.
 *
 * Use:		Decrypts a packet.
 */

extern int ks_decrypt(keyset **/*ksroot*/, buf */*b*/, buf */*bb*/);

/*----- Administration interface ------------------------------------------*/

/* --- @a_warn@ --- *
 *
 * Arguments:	@const char *fmt@ = pointer to format string
 *		@...@ = other arguments
 *
 * Returns:	---
 *
 * Use:		Informs all admin connections of a warning.
 */

extern void a_warn(const char */*fmt*/, ...);

/* --- @a_create@ --- *
 *
 * Arguments:	@int fd_in, fd_out@ = file descriptors to use
 *
 * Returns:	---
 *
 * Use:		Creates a new admin connection.
 */

extern void a_create(int /*fd_in*/, int /*fd_out*/);

/* --- @a_quit@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Shuts things down nicely.
 */

extern void a_quit(void);

/* --- @a_daemon@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Informs the admin module that it's a daemon.
 */

extern void a_daemon(void);

/* --- @a_init@ --- *
 *
 * Arguments:	@const char *sock@ = socket name to create
 *
 * Returns:	---
 *
 * Use:		Creates the admin listening socket.
 */

extern void a_init(const char */*sock*/);

/*----- Peer management ---------------------------------------------------*/

/* --- @p_txstart@ --- *
 *
 * Arguments:	@peer *p@ = pointer to peer block
 *		@unsigned msg@ = message type code
 *
 * Returns:	A pointer to a buffer to write to.
 *
 * Use:		Starts sending to a peer.  Only one send can happen at a
 *		time.
 */

extern buf *p_txstart(peer */*p*/, unsigned /*msg*/);

/* --- @p_txend@ --- *
 *
 * Arguments:	@peer *p@ = pointer to peer block
 *
 * Returns:	---
 *
 * Use:		Sends a packet to the peer.
 */

extern void p_txend(peer */*p*/);

/* --- @p_tun@ --- *
 *
 * Arguments:	@peer *p@ = pointer to peer block
 *		@buf *b@ = buffer containing incoming packet
 *
 * Returns:	---
 *
 * Use:		Handles a packet which needs to be sent to a peer.
 */

extern void p_tun(peer */*p*/, buf */*b*/);

/* --- @p_interval@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Called periodically to do tidying.
 */

extern void p_interval(void);

/* --- @p_ifname@ --- *
 *
 * Arguments:	@peer *p@ = pointer to a peer block
 *
 * Returns:	A pointer to the peer's interface name.
 */

extern const char *p_ifname(peer */*p*/);

/* --- @p_addr@ --- *
 *
 * Arguments:	@peer *p@ = pointer to a peer block
 *
 * Returns:	A pointer to the peer's address.
 */

extern const addr *p_addr(peer */*p*/);

/* --- @p_init@ --- *
 *
 * Arguments:	@unsigned port@ = port number to listen to
 *
 * Returns:	---
 *
 * Use:		Initializes the peer system; creates the socket.
 */

extern void p_init(unsigned /*port*/);

/* --- @p_port@ --- *
 *
 * Arguments:	---
 *
 * Returns:	Port number used for socket.
 */

unsigned p_port(void);

/* --- @p_create@ --- *
 *
 * Arguments:	@const char *name@ = name for this peer
 *		@struct sockaddr *sa@ = socket address of peer
 *		@size_t sz@ = size of socket address
 *
 * Returns:	Pointer to the peer block, or null if it failed.
 *
 * Use:		Creates a new named peer block.  No peer is actually attached
 *		by this point.
 */

extern peer *p_create(const char */*name*/,
		      struct sockaddr */*sa*/, size_t /*sz*/);

/* --- @p_name@ --- *
 *
 * Arguments:	@peer *p@ = pointer to a peer block
 *
 * Returns:	A pointer to the peer's name.
 */

extern const char *p_name(peer */*p*/);

/* --- @p_find@ --- *
 *
 * Arguments:	@const char *name@ = name to look up
 *
 * Returns:	Pointer to the peer block, or null if not found.
 *
 * Use:		Finds a peer by name.
 */

extern peer *p_find(const char */*name*/);

/* --- @p_destroy@ --- *
 *
 * Arguments:	@peer *p@ = pointer to a peer
 *
 * Returns:	---
 *
 * Use:		Destroys a peer.
 */

extern void p_destroy(peer */*p*/);

/* --- @p_first@, @p_next@ --- *
 *
 * Arguments:	@peer *p@ = a peer block
 *
 * Returns:	@peer_first@ returns the first peer in some ordering;
 *		@peer_next@ returns the peer following a given one in the
 *		same ordering.  Null is returned for the end of the list.
 */

extern peer *p_first(void);
extern peer *p_next(peer */*p*/);

/*----- Tunnel interface --------------------------------------------------*/

/* --- @tun_init@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Initializes the tunneling system.  Maybe this will require
 *		opening file descriptors or something.
 */

extern void tun_init(void);

/* --- @tun_create@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *		@peer *p@ = pointer to peer block
 *
 * Returns:	Zero if it worked, nonzero on failure.
 *
 * Use:		Initializes a new tunnel.
 */

extern int tun_create(tunnel */*t*/, peer */*p*/);

/* --- @tun_ifname@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *
 * Returns:	A pointer to the tunnel's interface name.
 */

extern const char *tun_ifname(tunnel */*t*/);

/* --- @tun_inject@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *		@buf *b@ = buffer to send
 *
 * Returns:	---
 *
 * Use:		Injects a packet into the local network stack.
 */

extern void tun_inject(tunnel */*t*/, buf */*b*/);

/* --- @tun_destroy@ --- *
 *
 * Arguments:	@tunnel *t@ = pointer to tunnel block
 *
 * Returns:	---
 *
 * Use:		Destroys a tunnel.
 */

extern void tun_destroy(tunnel */*t*/);

/*----- Buffer handling ---------------------------------------------------*/

/* --- Useful macros --- */

#define BBASE(b) ((b)->base)
#define BLIM(b) ((b)->limit)
#define BCUR(b) ((b)->p)
#define BSZ(b) ((b)->limit - (b)->base)
#define BLEN(b) ((b)->p - (b)->base)
#define BLEFT(b) ((b)->limit - (b)->p)
#define BSTEP(b, sz) ((b)->p += (sz))
#define BBAD(b) ((b)->f & BF_BROKEN)
#define BOK(b) (!BBAD(b))

#define BENSURE(b, sz)							\
  (BBAD(b) ? -1 : (sz) > BLEFT(b) ? (b)->f |= BF_BROKEN, -1 : 0)

/* --- @buf_init@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@void *p@ = pointer to a buffer
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	---
 *
 * Use:		Initializes the buffer block appropriately.
 */

extern void buf_init(buf */*b*/, void */*p*/, size_t /*sz*/);

/* --- @buf_break@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	Some negative value.
 *
 * Use:		Marks a buffer as broken.
 */

extern int buf_break(buf */*b*/);

/* --- @buf_ensure@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@size_t sz@ = size of data wanted
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Ensures that there are @sz@ bytes still in the buffer.
 */

extern int buf_ensure(buf */*b*/, size_t /*sz*/);

/* --- @buf_get@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@void *p@ = pointer to a buffer
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough data.
 *
 * Use:		Fetches data from the buffer into some other place.
 */

extern int buf_get(buf */*b*/, void */*p*/, size_t /*sz*/);

/* --- @buf_put@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@const void *p@ = pointer to a buffer
 *		@size_t sz@ = size of the buffer
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Fetches data from some place and puts it in the buffer
 */

extern int buf_put(buf */*b*/, const void */*p*/, size_t /*sz*/);

/* --- @buf_getbyte@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	A byte, or less than zero if there wasn't a byte there.
 *
 * Use:		Gets a single byte from a buffer.
 */

extern int buf_getbyte(buf */*b*/);

/* --- @buf_putbyte@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@int ch@ = byte to write
 *
 * Returns:	Zero if OK, nonzero if there wasn't enough space.
 *
 * Use:		Puts a single byte in a buffer.
 */

extern int buf_putbyte(buf */*b*/, int /*ch*/);

/* --- @buf_getword@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint32 *w@ = where to put the word
 *
 * Returns:	Zero if OK, or nonzero if there wasn't a word there.
 *
 * Use:		Gets a 32-bit word from a buffer.
 */

extern int buf_getword(buf */*b*/, uint32 */*w*/);

/* --- @buf_putword@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@uint32 w@ = word to write
 *
 * Returns:	Zero if OK, nonzero if there wasn't enough space.
 *
 * Use:		Puts a 32-but word in a buffer.
 */

extern int buf_putword(buf */*b*/, uint32 /*w*/);

/* --- @buf_getmp@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *
 * Returns:	A multiprecision integer, or null if there wasn't one there.
 *
 * Use:		Gets a multiprecision integer from a buffer.
 */

extern mp *buf_getmp(buf */*b*/, mp */*d*/);

/* --- @buf_putmp@ --- *
 *
 * Arguments:	@buf *b@ = pointer to a buffer block
 *		@mp *m@ = a multiprecision integer
 *
 * Returns:	Zero if it worked, nonzero if there wasn't enough space.
 *
 * Use:		Puts a multiprecision integer to a buffer.
 */

extern int buf_putmp(buf */*b*/, mp */*m*/);

/*----- Other handy utilities ---------------------------------------------*/

/* --- @mpstr@ --- *
 *
 * Arguments:	@mp *m@ = a multiprecision integer
 *
 * Returns:	A pointer to the integer's textual representation.
 *
 * Use:		Converts a multiprecision integer to a string.  Corrupts
 *		@buf_o@.
 */

extern const char *mpstr(mp */*m*/);

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif