pgprngpkt.c

著名的加密软件的应用于电子邮件中

/*
* pgpRngPkt.c -- Low-level keyring packet handling routines.
*
* Copyright (C) 1994-1997 Pretty Good Privacy, Inc. All rights reserved.
*
* Written by Colin Plumb.
*
* $Id: pgpRngPkt.c,v 1.4.2.1 1997/06/07 09:50:38 mhw Exp $
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>
#include <string.h>	 /* For memset() and memcmp() */

#include "pgpDebug.h"
#include "pgpPktByte.h"
#include "pgpRngPkt.h"
#include "pgpErr.h"
#include "pgpUsuals.h"
#include "pgpFile.h"

#ifndef NULL
#define NULL 0
#endif

#ifdef DEADCODE
char const * const packet_type[16] = {
			"0: Unknown packet type",
			"1: Public-key encrypted packet",
			"2: Signature packet",
			"3: Unknown packet type",
			"4: Unknown packet type",
			"5: Secret key",
			"6: Public key",
			"7: Unknown packet type",
			"8: Compressed packet",
			"9: Conventional-key encrypted",
			"A: Unknown packet type",
			"B: Literal packet",
			"C: Trust packet",
			"D: Key name packet",
			"E: Comment packet",
			"F: Unknown packet type"
	};
	#endif

/*
* Returns packet byte, 0 on normal EOF, or error code < 0.
*/
int
pktByteGet(struct PgpFile *f, word32 *lenp, word32 *posp)
{
	byte pktbyte;
	byte buf4[4];
	word32 len = 0;

if (posp) {
	*posp = pgpFileTell(f);
	if (*posp == (word32)-1)
		return PGPERR_KEYIO_FTELL;
}

			if (pgpFileRead(&pktbyte, 1, f) != 1)
				 return pgpFileError(f) ? PGPERR_KEYIO_READING : 0;

			if (IS_OLD_PKTBYTE(pktbyte)) {
					switch(PKTBYTE_LLEN(pktbyte)) {
					case 3:
							/* Indeterminate length, can't handle that yet */
							return PGPERR_KEYIO_BADPKT;
						case 2:
							if (pgpFileRead(buf4, 4, f) != 4)
								 goto error;
							len = (word32)buf4[0]<<24 | (word32)buf4[1]<<16 |
								 (word32)buf4[2]<<8 | (word32)buf4[3];
							break;
						case 1:
							if (pgpFileRead(buf4, 2, f) != 2)
								 goto error;
							len = (word32)buf4[0]<<8 | (word32)buf4[1];
							break;
						case 0:
							if (pgpFileRead(buf4, 1, f) != 1)
								 goto error;
							len = (word32)buf4[0];
							break;
					}
			} else if (IS_NEW_PKTBYTE(pktbyte)) {
					if (pgpFileRead(buf4, 1, f) != 1)
						goto error;
					len = (word32)buf4[0];
					if (len < 0xc0) {
						/* len is the length */
					} else if ((len & 0xe0) == 0xc0) {
						len &= 0x3f;
						if (pgpFileRead(buf4, 1, f) != 1)
							 goto error;
						len = (len << 8) + (word32)buf4[0] + 192;
					} else {
						/* Indeterminate length, can't handle that yet */
						return PGPERR_KEYIO_BADPKT;
			}
		} else
			return PGPERR_KEYIO_BADPKT;

*lenp = len;
return (int)pktbyte;

error:
if (!pgpFileError(f))
	return PGPERR_KEYIO_EOF;
pgpFileClearError(f);
return PGPERR_KEYIO_READING;
}

/*
* Returns the number of bytes which will be output by pktBytePut with the
* corresponding args.
*/
int
pktByteLen (byte pktbyte, word32 len)
	{
			if (IS_OLD_PKTBYTE(pktbyte)) {
					/* "Promote" packet byte llen field */
					/* if necessary to accomodate length */
					if (len == 0xfffffff) {
						pktbyte |= 3;
					} else if (len > 0xffff) {
						if (!(pktbyte & 2))
							 pktbyte = (pktbyte & ~3) | 2;
					} else if (len > 0xff) {
						if ((pktbyte & 3) == 0)
							 pktbyte |= 1;
					}
					switch(pktbyte & 3) {
					case 3:
								return 1;
						case 2:
								return 5;
						case 1:
								return 3;
						case 0:
								return 2;
					}
			} else {
					pgpAssert(IS_NEW_PKTBYTE(pktbyte));
					if (PKTLEN_ONE_BYTE(len)) {
						return 2;
					} else {
						return 3;
					}
			}
		
			/* Avoid warning */
			pgpAssert(0);
			return 0;
	}

	/*
* Returns the packet byte actually written, whose llen field may be greater
* than the one passed in, but will not be less, or error code < 0.
*/
int
pktBytePut(struct PgpFile *f, byte pktbyte, word32 len)
	{
			byte buf4[4];
			unsigned llen;

if (IS_OLD_PKTBYTE(pktbyte)) {
	/* "Promote" packet byte llen field */
	/* if necessary to accomodate length */
	if (len == 0xfffffff) {
						pktbyte |= 3;
					} else if (len > 0xffff) {
						if (!(pktbyte & 2))
							 pktbyte = (pktbyte & ~3) | 2;
					} else if (len > 0xff) {
						if ((pktbyte & 3) == 0)
							 pktbyte |= 1;
					}

					if (pgpFileWrite(&pktbyte, 1, f) != 1)
						return PGPERR_KEYIO_WRITING;

					switch(pktbyte & 3) {
					case 3:
								/* no length field */
								break;
							case 2:
								buf4[0] = (byte)(len >> 24);
								buf4[1] = (byte)(len >> 16);
								buf4[2] = (byte)(len >> 8);
								buf4[3] = (byte)(len );
								if (pgpFileWrite(buf4, 4, f) != 4)
									return PGPERR_KEYIO_WRITING;
								break;
							case 1:
								buf4[0] = (byte)(len >> 8);
								buf4[1] = (byte)(len );
								if (pgpFileWrite(buf4, 2, f) != 2)
									return PGPERR_KEYIO_WRITING;
								break;
							case 0:
								buf4[0] = (byte)len;
								if (pgpFileWrite(buf4, 1, f) != 1)
									return PGPERR_KEYIO_WRITING;
								break;
						}
			} else {
					pgpAssert(IS_NEW_PKTBYTE(pktbyte));
					buf4[0] = (byte)pktbyte;
					if (PKTLEN_ONE_BYTE(len)) {
						buf4[1] = PKTLEN_1BYTE(len);
						llen = 2;
					} else {
						buf4[1] = PKTLEN_BYTE0(len);
						buf4[2] = PKTLEN_BYTE1(len);
						llen = 3;
					}
					if (pgpFileWrite(buf4, llen, f) != llen)
								return PGPERR_KEYIO_WRITING;
			}
			return pktbyte;
	}

	/*
* Compare data from a file to a supplied buffer, returning < 0
* on a read error, 0 on equal, and 1 on unequal.
*/
int
fileUnequalBuf(struct PgpFile *f, char const *buf, size_t len)
	{
			char buf2[256];
			size_t amount;

			while (len) {
					amount = len < sizeof(buf2) ? len : sizeof(buf2);
					amount = pgpFileRead(buf2, amount, f);
					if (!amount)
						return pgpFileError(f) ? PGPERR_KEYIO_READING
							 	: PGPERR_KEYIO_EOF;
					if (memcmp(buf, buf2, amount) != 0)
						return 1;

					len -= amount;
					buf += amount;
			}
			return 0;	/* Match */
}