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Annotation of 43BSDReno/kerberosIV/des/quad_cksum.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * $Source: /afs/athena.mit.edu/astaff/project/kerberos/src/lib/des/RCS/quad_cksum.c,v $
        !             3:  * $Author: jtkohl $
        !             4:  *
        !             5:  * Copyright 1985, 1986, 1987, 1988 by the Massachusetts Institute
        !             6:  * of Technology.
        !             7:  *
        !             8:  * For copying and distribution information, please see the file
        !             9:  * <mit-copyright.h>.
        !            10:  *
        !            11:  * Quadratic Congruential Manipulation Dectection Code
        !            12:  *
        !            13:  * ref: "Message Authentication"
        !            14:  *             R.R. Jueneman, S. M. Matyas, C.H. Meyer
        !            15:  *             IEEE Communications Magazine,
        !            16:  *             Sept 1985 Vol 23 No 9 p 29-40
        !            17:  *
        !            18:  * This routine, part of the Athena DES library built for the Kerberos
        !            19:  * authentication system, calculates a manipulation detection code for
        !            20:  * a message.  It is a much faster alternative to the DES-checksum
        !            21:  * method. No guarantees are offered for its security. Refer to the
        !            22:  * paper noted above for more information
        !            23:  *
        !            24:  * Implementation for 4.2bsd
        !            25:  * by S.P. Miller      Project Athena/MIT
        !            26:  */
        !            27: 
        !            28: /*
        !            29:  * Algorithm (per paper):
        !            30:  *             define:
        !            31:  *             message to be composed of n m-bit blocks X1,...,Xn
        !            32:  *             optional secret seed S in block X1
        !            33:  *             MDC in block Xn+1
        !            34:  *             prime modulus N
        !            35:  *             accumulator Z
        !            36:  *             initial (secret) value of accumulator C
        !            37:  *             N, C, and S are known at both ends
        !            38:  *             C and , optionally, S, are hidden from the end users
        !            39:  *             then
        !            40:  *                     (read array references as subscripts over time)
        !            41:  *                     Z[0] = c;
        !            42:  *                     for i = 1...n
        !            43:  *                             Z[i] = (Z[i+1] + X[i])**2 modulo N
        !            44:  *                     X[n+1] = Z[n] = MDC
        !            45:  *
        !            46:  *             Then pick
        !            47:  *                     N = 2**31 -1
        !            48:  *                     m = 16
        !            49:  *                     iterate 4 times over plaintext, also use Zn
        !            50:  *                     from iteration j as seed for iteration j+1,
        !            51:  *                     total MDC is then a 128 bit array of the four
        !            52:  *                     Zn;
        !            53:  *
        !            54:  *                     return the last Zn and optionally, all
        !            55:  *                     four as output args.
        !            56:  *
        !            57:  * Modifications:
        !            58:  *     To inhibit brute force searches of the seed space, this
        !            59:  *     implementation is modified to have
        !            60:  *     Z       = 64 bit accumulator
        !            61:  *     C       = 64 bit C seed
        !            62:  *     N       = 2**63 - 1
        !            63:  *  S  = S seed is not implemented here
        !            64:  *     arithmetic is not quite real double integer precision, since we
        !            65:  *     cant get at the carry or high order results from multiply,
        !            66:  *     but nontheless is 64 bit arithmetic.
        !            67:  */
        !            68: 
        !            69: #ifndef        lint
        !            70: static char rcsid_quad_cksum_c[] =
        !            71: "$Id: quad_cksum.c,v 4.13 90/01/02 13:46:34 jtkohl Exp $";
        !            72: #endif lint
        !            73: 
        !            74: #include <mit-copyright.h>
        !            75: 
        !            76: /* System include files */
        !            77: #include <stdio.h>
        !            78: #include <errno.h>
        !            79: 
        !            80: /* Application include files */
        !            81: #include <des.h>
        !            82: #include "des_internal.h"
        !            83: /* Definitions for byte swapping */
        !            84: 
        !            85: #ifdef LSBFIRST
        !            86: #ifdef MUSTALIGN
        !            87: static unsigned long vaxtohl();
        !            88: static unsigned short vaxtohs();
        !            89: #else /* ! MUSTALIGN */
        !            90: #define vaxtohl(x) *((unsigned long *)(x))
        !            91: #define vaxtohs(x) *((unsigned short *)(x))
        !            92: #endif /* MUSTALIGN */
        !            93: #else /* !LSBFIRST */
        !            94: static unsigned long four_bytes_vax_to_nets();
        !            95: #define vaxtohl(x) four_bytes_vax_to_nets((char *)(x))
        !            96: static unsigned short two_bytes_vax_to_nets();
        !            97: #define vaxtohs(x) two_bytes_vax_to_nets((char *)(x))
        !            98: #endif
        !            99: 
        !           100: /* Externals */
        !           101: extern char *errmsg();
        !           102: extern int errno;
        !           103: extern int des_debug;
        !           104: 
        !           105: /*** Routines ***************************************************** */
        !           106: 
        !           107: unsigned long
        !           108: des_quad_cksum(in,out,length,out_count,c_seed)
        !           109:     des_cblock *c_seed;                /* secret seed, 8 bytes */
        !           110:     unsigned char *in;         /* input block */
        !           111:     unsigned long *out;                /* optional longer output */
        !           112:     int out_count;             /* number of iterations */
        !           113:     long length;               /* original length in bytes */
        !           114: {
        !           115: 
        !           116:     /*
        !           117:      * this routine both returns the low order of the final (last in
        !           118:      * time) 32bits of the checksum, and if "out" is not a null
        !           119:      * pointer, a longer version, up to entire 32 bytes of the
        !           120:      * checksum is written unto the address pointed to.
        !           121:      */
        !           122: 
        !           123:     register unsigned long z;
        !           124:     register unsigned long z2;
        !           125:     register unsigned long x;
        !           126:     register unsigned long x2;
        !           127:     register unsigned char *p;
        !           128:     register long len;
        !           129:     register int i;
        !           130: 
        !           131:     /* use all 8 bytes of seed */
        !           132: 
        !           133:     z = vaxtohl(c_seed);
        !           134:     z2 = vaxtohl((char *)c_seed+4);
        !           135:     if (out == NULL)
        !           136:        out_count = 1;          /* default */
        !           137: 
        !           138:     /* This is repeated n times!! */
        !           139:     for (i = 1; i <=4 && i<= out_count; i++) {
        !           140:        len = length;
        !           141:        p = in;
        !           142:        while (len) {
        !           143:            if (len > 1) {
        !           144:                x = (z + vaxtohs(p));
        !           145:                p += 2;
        !           146:                len -= 2;
        !           147:            }
        !           148:            else {
        !           149:                x = (z + *(char *)p++);
        !           150:                len = 0;
        !           151:            }
        !           152:            x2 = z2;
        !           153:            z  = ((x * x) + (x2 * x2)) % 0x7fffffff;
        !           154:            z2 = (x * (x2+83653421))   % 0x7fffffff; /* modulo */
        !           155:            if (des_debug & 8)
        !           156:                printf("%d %d\n",z,z2);
        !           157:        }
        !           158: 
        !           159:        if (out != NULL) {
        !           160:            *out++ = z;
        !           161:            *out++ = z2;
        !           162:        }
        !           163:     }
        !           164:     /* return final z value as 32 bit version of checksum */
        !           165:     return z;
        !           166: }
        !           167: #ifdef MSBFIRST
        !           168: 
        !           169: static unsigned short two_bytes_vax_to_nets(p)
        !           170:     char *p;
        !           171: {
        !           172:     union {
        !           173:        char pieces[2];
        !           174:        unsigned short result;
        !           175:     } short_conv;
        !           176: 
        !           177:     short_conv.pieces[0] = p[1];
        !           178:     short_conv.pieces[1] = p[0];
        !           179:     return(short_conv.result);
        !           180: }
        !           181: 
        !           182: static unsigned long four_bytes_vax_to_nets(p)
        !           183:     char *p;
        !           184: {
        !           185:     static union {
        !           186:        char pieces[4];
        !           187:        unsigned long result;
        !           188:     } long_conv;
        !           189: 
        !           190:     long_conv.pieces[0] = p[3];
        !           191:     long_conv.pieces[1] = p[2];
        !           192:     long_conv.pieces[2] = p[1];
        !           193:     long_conv.pieces[3] = p[0];
        !           194:     return(long_conv.result);
        !           195: }
        !           196: 
        !           197: #endif
        !           198: #ifdef LSBFIRST
        !           199: #ifdef MUSTALIGN
        !           200: static unsigned long vaxtohl(x)
        !           201: char *x;
        !           202: {
        !           203:     unsigned long val;
        !           204:     bcopy(x, (char *)&val, sizeof(val));
        !           205:     return(val);
        !           206: } 
        !           207: 
        !           208: static unsigned short vaxtohs(x)
        !           209: char *x;
        !           210: {
        !           211:     unsigned short val;
        !           212:     bcopy(x, (char *)&val, sizeof(val));
        !           213:     return(val);
        !           214: } 
        !           215: #endif /* MUSTALIGN */
        !           216: #endif /* LSBFIRST */

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