xenocara/lib/libXdmcp/Wrap.c

/*
 * $Xorg: Wrap.c,v 1.4 2001/02/09 02:03:49 xorgcvs Exp $
 *
 * 
Copyright 1989, 1998  The Open Group

Permission to use, copy, modify, distribute, and sell this software and its
documentation for any purpose is hereby granted without fee, provided that
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
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in this Software without prior written authorization from The Open Group.
 * *
 * Author:  Keith Packard, MIT X Consortium
 */

/* $XFree86: xc/lib/Xdmcp/Wrap.c,v 1.3 2001/01/17 19:42:44 dawes Exp $ */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <X11/Xos.h>
#include <X11/X.h>
#include <X11/Xmd.h>
#include <X11/Xdmcp.h>

#ifdef HASXDMAUTH

/*
 * The following function exists only to demonstrate the
 * desired functional interface for this routine.  You will
 * need to add the appropriate algorithm if you wish to
 * use XDM-AUTHENTICATION-1/XDM-AUTHORIZATION-1.
 *
 * Examine the XDMCP specification for the correct algorithm
 */

#include "Wrap.h"

void
XdmcpWrap (
    unsigned char	*input,
    unsigned char	*wrapper,
    unsigned char	*output,
    int			bytes)
{
    int			i, j;
    int			len;
    unsigned char	tmp[8];
    unsigned char	expand_wrapper[8];
    auth_wrapper_schedule	schedule;

    _XdmcpWrapperToOddParity (wrapper, expand_wrapper);
    _XdmcpAuthSetup (expand_wrapper, schedule);
    for (j = 0; j < bytes; j += 8)
    {
	len = 8;
	if (bytes - j < len)
	    len = bytes - j;
	/* block chaining */
	for (i = 0; i < len; i++)
	{
	    if (j == 0)
		tmp[i] = input[i];
	    else
		tmp[i] = input[j + i] ^ output[j - 8 + i];
	}
	for (; i < 8; i++)
	{
	    if (j == 0)
		tmp[i] = 0;
	    else
		tmp[i] = 0 ^ output[j - 8 + i];
	}
	_XdmcpAuthDoIt (tmp, (output + j), schedule, 1);
    }
}

/*
 * Given a 56 bit wrapper in XDMCP format, create a 56
 * bit wrapper in 7-bits + odd parity format
 */

static int
OddParity (unsigned char c)
{
    c = c ^ (c >> 4);
    c = c ^ (c >> 2);
    c = c ^ (c >> 1);
    return ~c & 0x1;
}

/*
 * Spread the 56 bit wrapper among 8 bytes, using the upper 7 bits
 * of each byte, and storing an odd parity bit in the low bit
 */

void
_XdmcpWrapperToOddParity (
    unsigned char   *in,
    unsigned char   *out)
{
    int		    ashift, bshift;
    int		    i;
    unsigned char   c;

    ashift = 7;
    bshift = 1;
    for (i = 0; i < 7; i++)
    {
	c = ((in[i] << ashift) | (in[i+1] >> bshift)) & 0x7f;
	out[i] = (c << 1) | OddParity (c);
	ashift--;
	bshift++;
    }
    c = in[i];
    out[i] = (c << 1) | OddParity(c);
}

#endif