pgpaddhdr.c

著名的加密软件的应用于电子邮件中

/*
* pgpAddHdr.c -- Add a PGP Packet Header to a data stream.
*
* Copyright (C) 1995-1997 Pretty Good Privacy, Inc. All rights reserved.
*
* Written by:	Derek Atkins <[e-mail]>
*
* $Id: pgpAddHdr.c,v 1.5.2.1 1997/06/07 09:51:13 mhw Exp $
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>

#include "pgpDebug.h"
#include "pgpAddHdr.h"
#include "pgpPktByte.h"
#include "pgpAnnotate.h"
#include "pgpFIFO.h"
#include "pgpMem.h"
#include "pgpPipeline.h"
#include "pgpErr.h"

#define ADDHEADERMAGIC	0xadd0b11e
#define BLOCK_SIZE 12
#define BUFFER_SIZE (1 << BLOCK_SIZE)	/* 2^10 == 4k */

struct Context {
			struct PgpFifoDesc const *fifod;
			struct PgpFifoContext *fifo;
			struct PgpPipeline *tail;
			byte header[5];					/* pktbyte + 4byte length */
			byte *ptr;
			int hdrlen;					/* actual header length */
			int dowrite;
			int sizeknown;					/* bytes is valid */
			unsigned long bytes;	 			/* sizeAdvise() promise */
			PgpVersion version;
			byte *buffer;
			byte *bufwrite;
			byte *bufptr;
			int buflen;
			int midflush;
			int scope_depth;
	};

/*
* Return the largest x such that 2^x <= n, n>0
* Return -1 if n==0
*/
static int
NumToBits(unsigned int n)
{
	int i;

	if (!n)
		return -1;

	for (i=0; n > 1; i++)
		n >>= 1;

	return i;
}

static int
FlushHeader(struct Context *context)
	{
			int error;
			size_t retlen;

			while (context->hdrlen) {
					retlen = context->tail->write(context->tail,
							 		context->ptr,
							 		context->hdrlen,
							 		&error);
					context->ptr += retlen;
					context->hdrlen -= retlen;
					if (error)
							return error;
			}
			return 0;
	}

static int
FlushBuffer(struct Context *context)
	{
			int error;
			size_t retlen;

			while (context->buflen) {
					retlen = context->tail->write(context->tail,
							 		context->bufptr,
							 		context->buflen,
							 		&error);
					context->bufptr += retlen;
					context->buflen -= retlen;
					if (error)
							return error;
			}
			return 0;
	}

static int
ForceFlush(struct Context *context)
{
int error;
int bufl, flushed;

while (context->buflen) {
	/* First, flush out any mid-flush we might have */

bufl = context->buflen;
flushed = context->midflush;
context->buflen = context->midflush;

					error = FlushBuffer(context);

					flushed -= context->buflen;
					context->midflush = context->buflen;
					context->buflen = bufl - flushed;

					if (error)
						return error;

					/*
					* Now, figure out how much should be sent in the
					* next sub-packet
					*/
					bufl = NumToBits(context->buflen);
					if (bufl < 0)
						break;

					context->bufptr--;
					context->buflen++;
					*(context->bufptr) = 0xE0 + bufl;
					context->midflush = (2^bufl) + 1;
			}

			return 0;
}

static int
DoFlush(struct Context *context)
	{
			int error = 0;
			size_t retlen;
			byte const *p;
			unsigned len;

			error = FlushHeader(context);
			if (error)
				 return error;

		/* Next, try to flush anything that we have buffered in the fifo */
		p = pgpFifoPeek (context->fifod, context->fifo, &len);
		while (len) {
					retlen = context->tail->write(context->tail,
							 	p, len, &error);
					pgpFifoSeek (context->fifod, context->fifo, retlen);
					if (error)
						return error;
				
					p = pgpFifoPeek (context->fifod, context->fifo, &len);
			}
		return error;
}

static int
Flush(struct PgpPipeline *myself)
{
	struct Context *context;
	int error;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);

			context = (struct Context *)myself->priv;
			pgpAssert(context);
			pgpAssert(context->tail);

			if (context->buffer) {
					error = FlushHeader(context);
					if (error)
						return error;

					/* Using the new packets -- force a flush of the buffer */
					if (context->dowrite) {
						error = FlushBuffer(context);
						if (error)
							 return error;
					} else {
							error = ForceFlush(context);
							if (error)
								 return error;
					}

			} else {
					/* Using the fifo */

					if (!context->dowrite)
						return PGPERR_ADDHDR_FLUSH;

					error = DoFlush(context);
					if (error)
						return error;
			}

			return context->tail->flush(context->tail);
}

/* Only called after args are checked, so I don't have to check them */
static size_t
BufferWrite(struct PgpPipeline *myself, byte const *buf, size_t size,
			int *error)
	{
			struct Context *context;
			size_t size0 = size;
			int t;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);
			pgpAssert(error);

			context = (struct Context *)myself->priv;
			pgpAssert(context);
			pgpAssert(context->tail);
			pgpAssert(context->buffer);

			*error = FlushHeader(context);
			if (*error)
				 return 0;

			do {
					/* If we are in the middle of a block, flush it out */
					if (context->dowrite) {
							*error = FlushBuffer(context);
							if (*error)
								 break;

							context->dowrite = 0;
							context->bufptr = context->buffer + 2;
							context->bufwrite = context->bufptr;
					}

					/* Try to fill up the buffer */
					t = min(((size_t)(BUFFER_SIZE - context->buflen)), size);
					if (t) {
							memcpy(context->bufwrite, buf, t);
							buf += t;
							size -= t;
							context->bufwrite += t;
							context->buflen += t;
					}

					/*
					* If we have a full block, write out the length
					* and then write out the block
					*/
					if (context->buflen == BUFFER_SIZE) {
							context->dowrite = 1;
							context->bufptr--;
							context->buflen++;
							*(context->bufptr) = 0xE0 + BLOCK_SIZE;

							continue;
					}

			} while (size);

			return size0 - size;
}

static size_t
Write(struct PgpPipeline *myself, byte const *buf, size_t size, int *error)
	{
			struct Context *context;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);
			pgpAssert(error);

		context = (struct Context *)myself->priv;
		pgpAssert(context);
		pgpAssert(context->tail);
		pgpAssert(context->fifo);

		if (!context->dowrite) {
	/* Buffer into the fifo until we get a sizeadvise */

				 return pgpFifoWrite (context->fifod, context->fifo, buf, size);
			}

			/*
			* Ok, we've been given our size. Flush the fifo and then be
			* a write-through
			*/
			*error = DoFlush(context);
			if (*error)
				 return 0;
			if (context->sizeknown && size > context->bytes) {
				 pgpAssert(0);
				 *error = PGPERR_SIZEADVISE;
				 return 0;
			}

			size = context->tail->write(context->tail, buf, size, error);
			context->bytes -= size;
			return size;
	}

static int
Annotate(struct PgpPipeline *myself, struct PgpPipeline *origin, int type,
			byte const *string, size_t size)
	{
			struct Context *context;
			int error;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);

			context = (struct Context *)myself->priv;
			pgpAssert(context);
			pgpAssert(context->tail);

			error = context->tail->annotate(context->tail, origin, type,
				 		 	string, size);
			if (!error)
				 PGP_SCOPE_DEPTH_UPDATE(context->scope_depth, type);
			pgpAssert(context->scope_depth != -1);
			return error;
	}

static int
BufferSizeAdvise(struct PgpPipeline *myself, unsigned long size)
	{
			struct Context *context;
			int error;
			int i;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);

			context = (struct Context *)myself->priv;
			pgpAssert(context);
			pgpAssert(context->tail);
			pgpAssert(context->buffer);

			/* Do not pass non-zero sizeAdvise -- I can't do that! */
			if (size || context->scope_depth)
				 return 0;

			/* Okay, we're at end of input. */
			if (context->buflen) {
					if (context->dowrite) {
						error = FlushBuffer(context);
					} else if (context->midflush) {
						error = ForceFlush(context);
					} else {
							i = context->buflen;
							if (PKTLEN_ONE_BYTE(i)) {
								 context->bufptr--;
								 context->buflen++;
								 context->bufptr[0] = PKTLEN_1BYTE(i);
							} else {
									context->bufptr -= 2;
									context->buflen += 2;
									context->bufptr[0] = PKTLEN_BYTE0(i);
									context->bufptr[1] = PKTLEN_BYTE1(i);
							}
							context->midflush = context->buflen;
							error = ForceFlush(context);
					}
					if (error)
						return error;
			}
		
			return context->tail->sizeAdvise(context->tail, 0);
	}

static int
SizeAdvise(struct PgpPipeline *myself, unsigned long len)
	{
			struct Context *context;
			unsigned long size;
			int error;
			int i;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);

			context = (struct Context *)myself->priv;
			pgpAssert(context);
			pgpAssert(context->tail);
			pgpAssert(context->fifo);

			if (context->scope_depth)
				 return 0;	/* Can't pass it through */

			/*
			* The actual size myself module will output is the byte size
			* passed in (size), plus the size of the buffered header,
			* plus the size of the data in the fifo. However the packet
			* size does not include the header size, so add in the header
			* size after we compute the header.
			*/

			/*
			* Set the header packet up properly, if we haven't already
			* done so. We know how long the length-of-length should be,
			* so fill that many bytes of the header in MSB-first order.
			*/
			if (!context->dowrite) {
					size = len + pgpFifoSize (context->fifod, context->fifo);
		
					i = PKTBYTE_LLEN(context->header[0]);
					if (size >= 0x10000 && i <= 2)
						i = 2;
					else if (size >= 0x100 && i <= 1)
						i = 1;
					context->header[0] = (context->header[0] & ~3) | i;

					i = LLEN_TO_BYTES(i);
					context->hdrlen = i+1;
					while (i--) {
						context->header[i+1] = (byte)(size & 0xff);
						size >>= 8;
					}
			}

			if (!context->sizeknown) {
				 context->bytes = len;
				 context->sizeknown = 1;
			} else if (context->bytes != len) {
				 return PGPERR_SIZEADVISE;
			}

			/*
			* Now add in the header size, sizeAdvise the next module, and
			* if everything is ok, set the state to dowrite and flush.
			*/	
			size = len + pgpFifoSize (context->fifod, context->fifo)
				 + context->hdrlen;
			error = context->tail->sizeAdvise(context->tail, size);
			if (error)
				 return error;

			context->dowrite = 1;

			error = DoFlush(context);
			/*
			* Just in case we got a sizeAdvise(0) without anything else.
			* calling sizeAdvise(0) twice is ok!
			*/
			if (!error && !len)
				 error = context->tail->sizeAdvise(context->tail, 0);

			return error;
	}

static void
Teardown(struct PgpPipeline *myself)
{
		struct Context *context;

			pgpAssert(myself);
			pgpAssert(myself->magic == ADDHEADERMAGIC);

			context = (struct Context *)myself->priv;
			pgpAssert(context);

			if (context->tail)
				 context->tail->teardown(context->tail);

			if (context->fifo)
				 pgpFifoDestroy (context->fifod, context->fifo);

			if (context->buffer) {
				 memset(context->buffer, 0, BUFFER_SIZE+2);
				 pgpMemFree(context->buffer);
			}
		
			memset(context, 0, sizeof(*context));
			pgpMemFree(context);
			memset(myself, 0, sizeof(*myself));
			pgpMemFree(myself);
	}

struct PgpPipeline **
pgpAddHeaderCreate(struct PgpPipeline **head, PgpVersion vers,
				 struct PgpFifoDesc const *fd, byte pkttype, byte llen,
				 byte *hdr, size_t headerlen)
	{
			struct PgpPipeline *mod;
			struct PgpFifoContext *fifop = NULL;
			struct Context *context;
			byte *buf = NULL;
			byte pktbite;

		if (!head)
		return NULL;

		pgpAssert(fd);

			/* XXX If we have versions > 2.6, ignore llen */
			if (vers > PGPVERSION_2_6)
				 pktbite = PKTBYTE_BUILD_NEW(pkttype);
			else
				 pktbite = PKTBYTE_BUILD(pkttype, llen);

			context = (struct Context *)pgpMemAlloc(sizeof(*context));
			if (!context)
				 return NULL;
			mod = (struct PgpPipeline *)pgpMemAlloc(sizeof(*mod));
			if (!mod) {
				 pgpMemFree(context);
				 return NULL;
			}
			if (vers > PGPVERSION_2_6) {
				 buf = (byte *)pgpMemAlloc(BUFFER_SIZE + 2);
				 if (!buf) {
				 	pgpMemFree(context);
						 pgpMemFree(mod);
						 return NULL;
				}
				memcpy(buf+2, hdr, headerlen);

		} else {
				fifop = pgpFifoCreate (fd);
				if (!fifop) {
					pgpMemFree(context);
					pgpMemFree(mod);
					return NULL;
		}

		if (pgpFifoWrite (fd, fifop, hdr, headerlen) != headerlen) {
					pgpMemFree(context);
					pgpMemFree(mod);
					pgpFifoDestroy (fd, fifop);
					return NULL;
			}
	}

		mod->magic = ADDHEADERMAGIC;
		mod->flush = Flush;
		mod->write = Write;
		mod->sizeAdvise = SizeAdvise;
		mod->annotate = Annotate;
		mod->teardown = Teardown;
		mod->name = "Add Header Module";
		mod->priv = context;

		if (buf) {
				mod->write = BufferWrite;
				mod->sizeAdvise = BufferSizeAdvise;
		}

		memset(context, 0, sizeof(*context));
		context->fifod = fd;
	context->fifo = fifop;
	context->ptr = context->header;
	context->header[0] = pktbite;
	context->hdrlen = 1;
	context->version = vers;
	context->buffer = buf;
	context->bufptr = buf + 2;
	context->bufwrite = context->bufptr + headerlen;

	if (vers > PGPVERSION_2_6)
		context->buflen = headerlen;
	else if (llen == 3)
		context->dowrite = 1;
	
	context->tail = *head;
	*head = mod;
	return &context->tail;
}