/*
 * Copyright 1995 by Richard P. Basch.  All Rights Reserved.
 * Copyright 1995 by Lehman Brothers, Inc.  All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of Richard P. Basch, Lehman Brothers and M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission.  Richard P. Basch,
 * Lehman Brothers and M.I.T. make no representations about the suitability
 * of this software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#include "des_int.h"
#include "f_tables.h"

/*
 * Triple-DES CBC encryption mode.
 */

#undef mit_des3_cbc_encrypt
int
mit_des3_cbc_encrypt(const mit_des_cblock *in, mit_des_cblock *out,
		     unsigned long length, const mit_des_key_schedule ks1,
		     const mit_des_key_schedule ks2,
		     const mit_des_key_schedule ks3,
		     const mit_des_cblock ivec, int enc)
{
    if (enc)
	krb5int_des3_cbc_encrypt(in, out, length, ks1, ks2, ks3, ivec);
    else
	krb5int_des3_cbc_decrypt(in, out, length, ks1, ks2, ks3, ivec);
    return 0;
}

void
krb5int_des3_cbc_encrypt(const mit_des_cblock *in,
			 mit_des_cblock *out,
			 unsigned long length,
			 const mit_des_key_schedule ks1,
			 const mit_des_key_schedule ks2,
			 const mit_des_key_schedule ks3,
			 const mit_des_cblock ivec)
{
    register unsigned DES_INT32 left, right;
    const unsigned DES_INT32 *kp1, *kp2, *kp3;
    const unsigned char *ip;
    unsigned char *op;

    /*
     * Get key pointer here.  This won't need to be reinitialized
     */
    kp1 = (const unsigned DES_INT32 *)ks1;
    kp2 = (const unsigned DES_INT32 *)ks2;
    kp3 = (const unsigned DES_INT32 *)ks3;

    /*
     * Initialize left and right with the contents of the initial
     * vector.
     */
    ip = ivec;
    GET_HALF_BLOCK(left, ip);
    GET_HALF_BLOCK(right, ip);

    /*
     * Suitably initialized, now work the length down 8 bytes
     * at a time.
     */
    ip = *in;
    op = *out;
    while (length > 0) {
	/*
	 * Get more input, xor it in.  If the length is
	 * greater than or equal to 8 this is straight
	 * forward.  Otherwise we have to fart around.
	 */
	if (length >= 8) {
	    left  ^= ((*ip++) & FF_UINT32) << 24;
	    left  ^= ((*ip++) & FF_UINT32) << 16;
	    left  ^= ((*ip++) & FF_UINT32) <<  8;
	    left  ^=  (*ip++) & FF_UINT32;
	    right ^= ((*ip++) & FF_UINT32) << 24;
	    right ^= ((*ip++) & FF_UINT32) << 16;
	    right ^= ((*ip++) & FF_UINT32) <<  8;
	    right ^=  (*ip++) & FF_UINT32;
	    length -= 8;
	} else {
	    /*
	     * Oh, shoot.  We need to pad the
	     * end with zeroes.  Work backwards
	     * to do this.
	     */
	    ip += (int) length;
	    switch(length) {
	    case 7:	right ^= (*(--ip) & FF_UINT32) <<  8;
	    case 6:	right ^= (*(--ip) & FF_UINT32) << 16;
	    case 5:	right ^= (*(--ip) & FF_UINT32) << 24;
	    case 4:	left  ^=  *(--ip) & FF_UINT32;
	    case 3:	left  ^= (*(--ip) & FF_UINT32) <<  8;
	    case 2:	left  ^= (*(--ip) & FF_UINT32) << 16;
	    case 1:	left  ^= (*(--ip) & FF_UINT32) << 24;

	    }
	    length = 0;
	}

	/*
	 * Encrypt what we have
	 */
	DES_DO_ENCRYPT(left, right, kp1);
	DES_DO_DECRYPT(left, right, kp2);
	DES_DO_ENCRYPT(left, right, kp3);

	/*
	 * Copy the results out
	 */
	PUT_HALF_BLOCK(left, op);
	PUT_HALF_BLOCK(right, op);
    }
}

void
krb5int_des3_cbc_decrypt(const mit_des_cblock *in,
			 mit_des_cblock *out,
			 unsigned long length,
			 const mit_des_key_schedule ks1,
			 const mit_des_key_schedule ks2,
			 const mit_des_key_schedule ks3,
			 const mit_des_cblock ivec)
{
    register unsigned DES_INT32 left, right;
    const unsigned DES_INT32 *kp1, *kp2, *kp3;
    const unsigned char *ip;
    unsigned char *op;
    unsigned DES_INT32 ocipherl, ocipherr;
    unsigned DES_INT32 cipherl, cipherr;

    /*
     * Get key pointer here.  This won't need to be reinitialized
     */
    kp1 = (const unsigned DES_INT32 *)ks1;
    kp2 = (const unsigned DES_INT32 *)ks2;
    kp3 = (const unsigned DES_INT32 *)ks3;

    /*
     * Decrypting is harder than encrypting because of
     * the necessity of remembering a lot more things.
     * Should think about this a little more...
     */

    if (length <= 0)
	return;

    /*
     * Prime the old cipher with ivec.
     */
    ip = ivec;
    GET_HALF_BLOCK(ocipherl, ip);
    GET_HALF_BLOCK(ocipherr, ip);

    /*
     * Now do this in earnest until we run out of length.
     */
    ip = *in;
    op = *out;
    for (;;) {		/* check done inside loop */
	/*
	 * Read a block from the input into left and
	 * right.  Save this cipher block for later.
	 */
	GET_HALF_BLOCK(left, ip);
	GET_HALF_BLOCK(right, ip);
	cipherl = left;
	cipherr = right;

	/*
	 * Decrypt this.
	 */
	DES_DO_DECRYPT(left, right, kp3);
	DES_DO_ENCRYPT(left, right, kp2);
	DES_DO_DECRYPT(left, right, kp1);

	/*
	 * Xor with the old cipher to get plain
	 * text.  Output 8 or less bytes of this.
	 */
	left ^= ocipherl;
	right ^= ocipherr;
	if (length > 8) {
	    length -= 8;
	    PUT_HALF_BLOCK(left, op);
	    PUT_HALF_BLOCK(right, op);
	    /*
	     * Save current cipher block here
	     */
	    ocipherl = cipherl;
	    ocipherr = cipherr;
	} else {
	    /*
	     * Trouble here.  Start at end of output,
	     * work backwards.
	     */
	    op += (int) length;
	    switch(length) {
	    case 8: *(--op) = (unsigned char) (right & 0xff);
	    case 7: *(--op) = (unsigned char) ((right >> 8) & 0xff);
	    case 6: *(--op) = (unsigned char) ((right >> 16) & 0xff);
	    case 5: *(--op) = (unsigned char) ((right >> 24) & 0xff);
	    case 4: *(--op) = (unsigned char) (left & 0xff);
	    case 3: *(--op) = (unsigned char) ((left >> 8) & 0xff);
	    case 2: *(--op) = (unsigned char) ((left >> 16) & 0xff);
	    case 1: *(--op) = (unsigned char) ((left >> 24) & 0xff);
	    }
	    break;		/* we're done */
	}
    }
}
