path: root/util/descrypt.c

/* $Id: descrypt.c,v 1.1 2002/03/07 15:13:45 in2 Exp $ */

/*
 * FreeSec: libcrypt for NetBSD
 *
 * Copyright (c) 1994 David Burren
 * All rights reserved.
 *
 * Adapted for FreeBSD-2.0 by Geoffrey M. Rehmet
 *  crypt.c should now *only* export crypt(), in order to make
 *  binaries of libcrypt exportable from the USA
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the author nor the names of other contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/secure/lib/libcrypt/crypt.c,v 1.11 1999/08/28 01:30:24 peter Exp $
 *
 * This is an original implementation of the DES and the crypt(3) interfaces
 * by David Burren <davidb@werj.com.au>.
 *
 * An excellent reference on the underlying algorithm (and related
 * algorithms) is:
 *
 *  B. Schneier, Applied Cryptography: protocols, algorithms,
 *  and source code in C, John Wiley & Sons, 1994.
 *
 * Note that in that book's description of DES the lookups for the initial,
 * pbox, and final permutations are inverted (this has been brought to the
 * attention of the author).  A list of errata for this book has been
 * posted to the sci.crypt newsgroup by the author and is available for FTP.
 *
 * ARCHITECTURE ASSUMPTIONS:
 *  This code assumes that u_longs are 32 bits.  It will probably not
 *  operate on 64-bit machines without modifications.
 *  It is assumed that the 8-byte arrays passed by reference can be
 *  addressed as arrays of u_longs (ie. the CPU is not picky about
 *  alignment).
 */

#ifndef HAVE_DES_CRYPT

#include <sys/types.h>
#include <sys/param.h>
#include <pwd.h>
#include <string.h>

static unsigned char IP[64] = {
    58, 50, 42, 34, 26, 18, 10,  2, 60, 52, 44, 36, 28, 20, 12,  4,
    62, 54, 46, 38, 30, 22, 14,  6, 64, 56, 48, 40, 32, 24, 16,  8,
    57, 49, 41, 33, 25, 17,  9,  1, 59, 51, 43, 35, 27, 19, 11,  3,
    61, 53, 45, 37, 29, 21, 13,  5, 63, 55, 47, 39, 31, 23, 15,  7
};

static unsigned char inv_key_perm[64];
static unsigned char u_key_perm[56];
static unsigned char key_perm[56] = {
    57, 49, 41, 33, 25, 17,  9,  1, 58, 50, 42, 34, 26, 18,
    10,  2, 59, 51, 43, 35, 27, 19, 11,  3, 60, 52, 44, 36,
    63, 55, 47, 39, 31, 23, 15,  7, 62, 54, 46, 38, 30, 22,
    14,  6, 61, 53, 45, 37, 29, 21, 13,  5, 28, 20, 12,  4
};

static unsigned char key_shifts[16] = {
    1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
};

static unsigned char inv_comp_perm[56];
static unsigned char comp_perm[48] = {
    14, 17, 11, 24,  1,  5,  3, 28, 15,  6, 21, 10,
    23, 19, 12,  4, 26,  8, 16,  7, 27, 20, 13,  2,
    41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48,
    44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32
};

/*
 *  No E box is used, as it's replaced by some ANDs, shifts, and ORs.
 */

static unsigned char u_sbox[8][64];
static unsigned char sbox[8][64] = {
    {
    14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
    0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
    4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
    15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
    },
    {
    15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
    3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
    0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
    13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
    },
    {
    10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
    13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
    13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
    1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
    },
    {
    7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
    13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
    10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
    3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
    },
    {
    2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
    14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
    4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
    11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
    },
    {
    12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
    10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
    9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
    4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
    },
    {
    4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
    13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
    1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
    6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
    },
    {
    13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
    1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
    7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
    2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
    }
};

static unsigned char un_pbox[32];
static unsigned char pbox[32] = {
    16,  7, 20, 21, 29, 12, 28, 17,  1, 15, 23, 26,  5, 18, 31, 10,
    2,  8, 24, 14, 32, 27,  3,  9, 19, 13, 30,  6, 22, 11,  4, 25
};

static unsigned long bits32[32] = {
    0x80000000, 0x40000000, 0x20000000, 0x10000000,
    0x08000000, 0x04000000, 0x02000000, 0x01000000,
    0x00800000, 0x00400000, 0x00200000, 0x00100000,
    0x00080000, 0x00040000, 0x00020000, 0x00010000,
    0x00008000, 0x00004000, 0x00002000, 0x00001000,
    0x00000800, 0x00000400, 0x00000200, 0x00000100,
    0x00000080, 0x00000040, 0x00000020, 0x00000010,
    0x00000008, 0x00000004, 0x00000002, 0x00000001
};

static unsigned char bits8[8] = { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };

static unsigned long saltbits;
static long old_salt;
static unsigned long *bits28, *bits24;
static unsigned char init_perm[64], final_perm[64];
static unsigned long en_keysl[16], en_keysr[16];
static unsigned long de_keysl[16], de_keysr[16];
static int des_initialised = 0;
static unsigned char m_sbox[4][4096];
static unsigned long psbox[4][256];
static unsigned long ip_maskl[8][256], ip_maskr[8][256];
static unsigned long fp_maskl[8][256], fp_maskr[8][256];
static unsigned long key_perm_maskl[8][128], key_perm_maskr[8][128];
static unsigned long comp_maskl[8][128], comp_maskr[8][128];
static unsigned long old_rawkey0, old_rawkey1;

static unsigned char    ascii64[] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
/*    0000000000111111111122222222223333333333444444444455555555556666 */
/*    0123456789012345678901234567890123456789012345678901234567890123 */

static int ascii_to_bin(char ch) {
    if(ch > 'z')
    return 0;
    if(ch >= 'a')
    return ch - 'a' + 38;
    if(ch > 'Z')
    return 0;
    if(ch >= 'A')
    return ch - 'A' + 12;
    if(ch > '9')
    return 0;
    if(ch >= '.')
    return ch - '.';
    return 0;
}

static void des_init() {
    int i, j, b, k, inbit, obit;
    unsigned long *p, *il, *ir, *fl, *fr;
    
    old_rawkey0 = old_rawkey1 = 0L;
    saltbits = 0L;
    old_salt = 0L;
    bits24 = (bits28 = bits32 + 4) + 4;
    
    /*
     * Invert the S-boxes, reordering the input bits.
     */
    for(i = 0; i < 8; i++)
    for(j = 0; j < 64; j++) {
        b = (j & 0x20) | ((j & 1) << 4) | ((j >> 1) & 0xf);
        u_sbox[i][j] = sbox[i][b];
    }
    
    /*
     * Convert the inverted S-boxes into 4 arrays of 8 bits.
     * Each will handle 12 bits of the S-box input.
     */
    for(b = 0; b < 4; b++)
    for(i = 0; i < 64; i++)
        for(j = 0; j < 64; j++)
        m_sbox[b][(i << 6) | j] =
            (u_sbox[(b << 1)][i] << 4) |
            u_sbox[(b << 1) + 1][j];

    /*
     * Set up the initial & final permutations into a useful form, and
     * initialise the inverted key permutation.
     */
    for(i = 0; i < 64; i++) {
    init_perm[final_perm[i] = IP[i] - 1] = i;
    inv_key_perm[i] = 255;
    }

    /*
     * Invert the key permutation and initialise the inverted key
     * compression permutation.
     */
    for(i = 0; i < 56; i++) {
    u_key_perm[i] = key_perm[i] - 1;
    inv_key_perm[key_perm[i] - 1] = i;
    inv_comp_perm[i] = 255;
    }

    /*
     * Invert the key compression permutation.
     */
    for(i = 0; i < 48; i++) {
    inv_comp_perm[comp_perm[i] - 1] = i;
    }

    /*
     * Set up the OR-mask arrays for the initial and final permutations,
     * and for the key initial and compression permutations.
     */
    for(k = 0; k < 8; k++) {
    for(i = 0; i < 256; i++) {
        *(il = &ip_maskl[k][i]) = 0L;
        *(ir = &ip_maskr[k][i]) = 0L;
        *(fl = &fp_maskl[k][i]) = 0L;
        *(fr = &fp_maskr[k][i]) = 0L;
        for(j = 0; j < 8; j++) {
        inbit = 8 * k + j;
        if(i & bits8[j]) {
            if((obit = init_perm[inbit]) < 32)
            *il |= bits32[obit];
            else
            *ir |= bits32[obit-32];
            if ((obit = final_perm[inbit]) < 32)
            *fl |= bits32[obit];
            else
            *fr |= bits32[obit - 32];
        }
        }
    }
    for(i = 0; i < 128; i++) {
        *(il = &key_perm_maskl[k][i]) = 0L;
        *(ir = &key_perm_maskr[k][i]) = 0L;
        for(j = 0; j < 7; j++) {
        inbit = 8 * k + j;
        if(i & bits8[j + 1]) {
            if((obit = inv_key_perm[inbit]) == 255)
            continue;
            if(obit < 28)
            *il |= bits28[obit];
            else
            *ir |= bits28[obit - 28];
        }
        }
        *(il = &comp_maskl[k][i]) = 0L;
        *(ir = &comp_maskr[k][i]) = 0L;
        for(j = 0; j < 7; j++) {
        inbit = 7 * k + j;
        if(i & bits8[j + 1]) {
            if((obit=inv_comp_perm[inbit]) == 255)
            continue;
            if(obit < 24)
            *il |= bits24[obit];
            else
            *ir |= bits24[obit - 24];
        }
        }
    }
    }
    
    /*
     * Invert the P-box permutation, and convert into OR-masks for
     * handling the output of the S-box arrays setup above.
     */
    for(i = 0; i < 32; i++)
    un_pbox[pbox[i] - 1] = i;

    for(b = 0; b < 4; b++)
    for(i = 0; i < 256; i++) {
        *(p = &psbox[b][i]) = 0L;
        for (j = 0; j < 8; j++) {
        if (i & bits8[j])
            *p |= bits32[un_pbox[8 * b + j]];
        }
    }
    
    des_initialised = 1;
}

static void setup_salt(long salt) {
    unsigned long obit, saltbit;
    int i;
    
    if (salt == old_salt)
    return;
    old_salt = salt;
    
    saltbits = 0L;
    saltbit = 1;
    obit = 0x800000;
    for (i = 0; i < 24; i++) {
    if (salt & saltbit)
        saltbits |= obit;
    saltbit <<= 1;
    obit >>= 1;
    }
}

static int des_setkey(const char *key) {
    unsigned long k0, k1, rawkey0, rawkey1;
    int shifts, round;

    if(!des_initialised)
    des_init();
    
    rawkey0 = ntohl(*(unsigned long *) key);
    rawkey1 = ntohl(*(unsigned long *) (key + 4));
    
    if((rawkey0 | rawkey1)
       && rawkey0 == old_rawkey0
       && rawkey1 == old_rawkey1) {
    /*
     * Already setup for this key.
     * This optimisation fails on a zero key (which is weak and
     * has bad parity anyway) in order to simplify the starting
     * conditions.
     */
    return 0;
    }
    old_rawkey0 = rawkey0;
    old_rawkey1 = rawkey1;
    
    /*
     *  Do key permutation and split into two 28-bit subkeys.
     */
    k0 = key_perm_maskl[0][rawkey0 >> 25]
    | key_perm_maskl[1][(rawkey0 >> 17) & 0x7f]
    | key_perm_maskl[2][(rawkey0 >> 9) & 0x7f]
    | key_perm_maskl[3][(rawkey0 >> 1) & 0x7f]
    | key_perm_maskl[4][rawkey1 >> 25]
    | key_perm_maskl[5][(rawkey1 >> 17) & 0x7f]
    | key_perm_maskl[6][(rawkey1 >> 9) & 0x7f]
    | key_perm_maskl[7][(rawkey1 >> 1) & 0x7f];
    k1 = key_perm_maskr[0][rawkey0 >> 25]
    | key_perm_maskr[1][(rawkey0 >> 17) & 0x7f]
    | key_perm_maskr[2][(rawkey0 >> 9) & 0x7f]
    | key_perm_maskr[3][(rawkey0 >> 1) & 0x7f]
    | key_perm_maskr[4][rawkey1 >> 25]
    | key_perm_maskr[5][(rawkey1 >> 17) & 0x7f]
    | key_perm_maskr[6][(rawkey1 >> 9) & 0x7f]
    | key_perm_maskr[7][(rawkey1 >> 1) & 0x7f];
    /*
     *  Rotate subkeys and do compression permutation.
     */
    shifts = 0;
    for(round = 0; round < 16; round++) {
    unsigned long t0, t1;
        
    shifts += key_shifts[round];
        
    t0 = (k0 << shifts) | (k0 >> (28 - shifts));
    t1 = (k1 << shifts) | (k1 >> (28 - shifts));
        
    de_keysl[15 - round] =
        en_keysl[round] = comp_maskl[0][(t0 >> 21) & 0x7f]
        | comp_maskl[1][(t0 >> 14) & 0x7f]
        | comp_maskl[2][(t0 >> 7) & 0x7f]
        | comp_maskl[3][t0 & 0x7f]
        | comp_maskl[4][(t1 >> 21) & 0x7f]
        | comp_maskl[5][(t1 >> 14) & 0x7f]
        | comp_maskl[6][(t1 >> 7) & 0x7f]
        | comp_maskl[7][t1 & 0x7f];
        
    de_keysr[15 - round] = en_keysr[round] =
        comp_maskr[0][(t0 >> 21) & 0x7f]
        | comp_maskr[1][(t0 >> 14) & 0x7f]
        | comp_maskr[2][(t0 >> 7) & 0x7f]
        | comp_maskr[3][t0 & 0x7f]
        | comp_maskr[4][(t1 >> 21) & 0x7f]
        | comp_maskr[5][(t1 >> 14) & 0x7f]
        | comp_maskr[6][(t1 >> 7) & 0x7f]
        | comp_maskr[7][t1 & 0x7f];
    }
    return 0;
}

static int do_des(unsigned long l_in, unsigned long r_in, unsigned long *l_out,
          unsigned long *r_out, int count) {
    /*
     *  l_in, r_in, l_out, and r_out are in pseudo-"big-endian" format.
     */
    unsigned long l, r, *kl, *kr, *kl1, *kr1;
    unsigned long f, r48l, r48r;
    int round;

    if(count == 0) {
    return 1;
    } else if(count > 0) {
    /*
         * Encrypting
         */
    kl1 = en_keysl;
    kr1 = en_keysr;
    } else {
    /*
         * Decrypting
         */
    count = -count;
    kl1 = de_keysl;
    kr1 = de_keysr;
    }
    
    /*
     *  Do initial permutation (IP).
     */
    l = ip_maskl[0][l_in >> 24]
    | ip_maskl[1][(l_in >> 16) & 0xff]
    | ip_maskl[2][(l_in >> 8) & 0xff]
    | ip_maskl[3][l_in & 0xff]
    | ip_maskl[4][r_in >> 24]
    | ip_maskl[5][(r_in >> 16) & 0xff]
    | ip_maskl[6][(r_in >> 8) & 0xff]
    | ip_maskl[7][r_in & 0xff];
    r = ip_maskr[0][l_in >> 24]
    | ip_maskr[1][(l_in >> 16) & 0xff]
    | ip_maskr[2][(l_in >> 8) & 0xff]
    | ip_maskr[3][l_in & 0xff]
    | ip_maskr[4][r_in >> 24]
    | ip_maskr[5][(r_in >> 16) & 0xff]
    | ip_maskr[6][(r_in >> 8) & 0xff]
    | ip_maskr[7][r_in & 0xff];
    
    while(count--) {
    /*
     * Do each round.
     */
    kl = kl1;
    kr = kr1;
    round = 16;
    while(round--) {
        /*
         * Expand R to 48 bits (simulate the E-box).
         */
        r48l = ((r & 0x00000001) << 23)
        | ((r & 0xf8000000) >> 9)
        | ((r & 0x1f800000) >> 11)
        | ((r & 0x01f80000) >> 13)
        | ((r & 0x001f8000) >> 15);

        r48r = ((r & 0x0001f800) << 7)
        | ((r & 0x00001f80) << 5)
        | ((r & 0x000001f8) << 3)
        | ((r & 0x0000001f) << 1)
        | ((r & 0x80000000) >> 31);
        /*
         * Do salting for crypt() and friends, and
         * XOR with the permuted key.
         */
        f = (r48l ^ r48r) & saltbits;
        r48l ^= f ^ *kl++;
        r48r ^= f ^ *kr++;
        /*
         * Do sbox lookups (which shrink it back to 32 bits)
         * and do the pbox permutation at the same time.
         */
        f = psbox[0][m_sbox[0][r48l >> 12]]
        | psbox[1][m_sbox[1][r48l & 0xfff]]
        | psbox[2][m_sbox[2][r48r >> 12]]
        | psbox[3][m_sbox[3][r48r & 0xfff]];
        /*
         * Now that we've permuted things, complete f().
         */
        f ^= l;
        l = r;
        r = f;
    }
    r = l;
    l = f;
    }
    /*
     * Do final permutation (inverse of IP).
     */
    *l_out = fp_maskl[0][l >> 24]
    | fp_maskl[1][(l >> 16) & 0xff]
    | fp_maskl[2][(l >> 8) & 0xff]
    | fp_maskl[3][l & 0xff]
    | fp_maskl[4][r >> 24]
    | fp_maskl[5][(r >> 16) & 0xff]
    | fp_maskl[6][(r >> 8) & 0xff]
    | fp_maskl[7][r & 0xff];
    *r_out = fp_maskr[0][l >> 24]
    | fp_maskr[1][(l >> 16) & 0xff]
    | fp_maskr[2][(l >> 8) & 0xff]
    | fp_maskr[3][l & 0xff]
    | fp_maskr[4][r >> 24]
    | fp_maskr[5][(r >> 16) & 0xff]
    | fp_maskr[6][(r >> 8) & 0xff]
    | fp_maskr[7][r & 0xff];
    return 0;
}

char *crypt(char *key, char *setting) {
    unsigned long count, salt, l, r0, r1, keybuf[2];
    unsigned char *p, *q;
    static unsigned char output[21];
    
    if(!des_initialised)
    des_init();
    /*
     * Copy the key, shifting each character up by one bit
     * and padding with zeros.
     */
    q = (unsigned char *)keybuf;
    while(q - (unsigned char *)keybuf - 8) {
    if((*q++ = *key << 1))
        key++;
    }
    if(des_setkey((unsigned char *)keybuf))
    return NULL;
    
    /*
     * "old"-style:
     *  setting - 2 bytes of salt
     *  key - up to 8 characters
     */
    count = 25;

    salt = (ascii_to_bin(setting[1]) << 6)
    |  ascii_to_bin(setting[0]);

    output[0] = setting[0];
    /*
     * If the encrypted password that the salt was extracted from
     * is only 1 character long, the salt will be corrupted.  We
     * need to ensure that the output string doesn't have an extra
     * NUL in it!
     */
    output[1] = setting[1] ? setting[1] : output[0];

    p = output + 2;

    setup_salt(salt);
    /*
     * Do it.
     */
    if(do_des(0L, 0L, &r0, &r1, count))
    return NULL;
    /*
     * Now encode the result...
     */
    l = (r0 >> 8);
    *p++ = ascii64[(l >> 18) & 0x3f];
    *p++ = ascii64[(l >> 12) & 0x3f];
    *p++ = ascii64[(l >> 6) & 0x3f];
    *p++ = ascii64[l & 0x3f];

    l = (r0 << 16) | ((r1 >> 16) & 0xffff);
    *p++ = ascii64[(l >> 18) & 0x3f];
    *p++ = ascii64[(l >> 12) & 0x3f];
    *p++ = ascii64[(l >> 6) & 0x3f];
    *p++ = ascii64[l & 0x3f];

    l = r1 << 2;
    *p++ = ascii64[(l >> 12) & 0x3f];
    *p++ = ascii64[(l >> 6) & 0x3f];
    *p++ = ascii64[l & 0x3f];
    *p = 0;

    return output;
}
#endif