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   1 /* -*-c-*-
   2  *
   3  * $Id: rc4.c,v 1.6 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * The alleged RC4 stream cipher
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <assert.h>
  33 #include <stdarg.h>
  34 #include <stdio.h>
  35
  36 #include <mLib/bits.h>
  37 #include <mLib/sub.h>
  38
  39 #include "arena.h"
  40 #include "gcipher.h"
  41 #include "grand.h"
  42 #include "paranoia.h"
  43 #include "rc4.h"
  44
  45 /*----- Global variables --------------------------------------------------*/
  46
  47 const octet rc4_keysz[] = { KSZ_RANGE, RC4_KEYSZ, 1, 255, 1 };
  48
  49 /*----- Main code ---------------------------------------------------------*/
  50
  51 /* --- @rc4_addkey@ --- *
  52  *
  53  * Arguments:   @rc4_ctx *ctx@ = pointer to context to key
  54  *              @const void *k@ = pointer to key data to use
  55  *              @size_t sz@ = size of the key data
  56  *
  57  * Returns:     ---
  58  *
  59  * Use:         Mixes key data with an RC4 context.  The RC4 context is not
  60  *              reset before mixing.  This may be used to mix new key
  61  *              material with an existing RC4 context.
  62  */
  63
  64 void rc4_addkey(rc4_ctx *ctx, const void *k, size_t sz)
  65 {
  66   unsigned i, j;
  67   const octet *p = k, *q = p + sz;
  68
  69   KSZ_ASSERT(rc4, sz);
  70
  71   for (i = j = 0; i < 256; i++) {
  72     unsigned si = ctx->s[i];
  73     j = (j + si + *p++) & 0xff;
  74     ctx->s[i] = ctx->s[j];
  75     ctx->s[j] = si;
  76     if (p == q)
  77       p = k;
  78   }
  79
  80   ctx->i = ctx->j = 0;
  81 }
  82
  83 /* --- @rc4_init@ --- *
  84  *
  85  * Arguments:   @rc4_ctx *ctx@ = pointer to context to initialize
  86  *              @const void *k@ = pointer to key data to use
  87  *              @size_t sz@ = size of the key data
  88  *
  89  * Returns:     ---
  90  *
  91  * Use:         Initializes an RC4 context ready for use.
  92  */
  93
  94 void rc4_init(rc4_ctx *ctx, const void *k, size_t sz)
  95 {
  96   unsigned i;
  97
  98   for (i = 0; i < 256; i++)
  99     ctx->s[i] = i;
 100   ctx->f = 0;
 101   rc4_addkey(ctx, k, sz);
 102 }
 103
 104 /* --- @rc4_encrypt@ --- *
 105  *
 106  * Arguments:   @rc4_ctx *ctx@ = pointer to context to use
 107  *              @const void *src@ = pointer to the source block
 108  *              @void *dest@ = pointer to the destination block
 109  *              @size_t sz@ = size of the block
 110  *
 111  * Returns:     ---
 112  *
 113  * Use:         Encrypts or decrypts a block of data.  The destination may
 114  *              be null to just grind the generator around for a while.  It's
 115  *              recommended that you say `@rc4_encrypt(&ctx, 0, 0, 1024)@'
 116  *              after initializing a new context, to prevent keystream
 117  *              guessing attacks.  The source may be null to just extract a
 118  *              big lump of data from the generator.
 119  */
 120
 121 void rc4_encrypt(rc4_ctx *ctx, const void *src, void *dest, size_t sz)
 122 {
 123   const octet *s = src;
 124   octet *d = dest;
 125
 126   if (!d)
 127     RC4_OPEN(ctx, while (sz) { unsigned x; RC4_BYTE(x); sz--; });
 128   else if (!s)
 129     RC4_OPEN(ctx, while (sz) { RC4_BYTE(*d++); sz--; });
 130   else
 131     RC4_OPEN(ctx,
 132              while (sz) { unsigned x; RC4_BYTE(x); *d++ = *s++ ^ x; sz--; });
 133 }
 134
 135 /*----- Generic cipher interface ------------------------------------------*/
 136
 137 typedef struct gctx {
 138   gcipher c;
 139   rc4_ctx rc4;
 140 } gctx;
 141
 142 static const gcipher_ops gops;
 143
 144 static gcipher *ginit(const void *k, size_t sz)
 145 {
 146   gctx *g = S_CREATE(gctx);
 147   g->c.ops = &gops;
 148   rc4_init(&g->rc4, k, sz);
 149   return (&g->c);
 150 }
 151
 152 static void gencrypt(gcipher *c, const void *s, void *t, size_t sz)
 153 {
 154   gctx *g = (gctx *)c;
 155   rc4_encrypt(&g->rc4, s, t, sz);
 156 }
 157
 158 static void gdestroy(gcipher *c)
 159 {
 160   gctx *g = (gctx *)c;
 161   BURN(*g);
 162   S_DESTROY(g);
 163 }
 164
 165 static const gcipher_ops gops = {
 166   &rc4,
 167   gencrypt, gencrypt, gdestroy, 0, 0
 168 };
 169
 170 const gccipher rc4 = {
 171   "rc4", rc4_keysz, 0,
 172   ginit
 173 };
 174
 175 /*----- Generic random number generator interface -------------------------*/
 176
 177 typedef struct grctx {
 178   grand r;
 179   rc4_ctx rc4;
 180 } grctx;
 181
 182 static void grdestroy(grand *r)
 183 {
 184   grctx *g = (grctx *)r;
 185   BURN(*g);
 186   S_DESTROY(g);
 187 }
 188
 189 static int grmisc(grand *r, unsigned op, ...)
 190 {
 191   grctx *g = (grctx *)r;
 192   va_list ap;
 193   int rc = 0;
 194   uint32 i;
 195   octet buf[4];
 196   va_start(ap, op);
 197
 198   switch (op) {
 199     case GRAND_CHECK:
 200       switch (va_arg(ap, unsigned)) {
 201         case GRAND_CHECK:
 202         case GRAND_SEEDINT:
 203         case GRAND_SEEDUINT32:
 204         case GRAND_SEEDBLOCK:
 205         case GRAND_SEEDRAND:
 206           rc = 1;
 207           break;
 208         default:
 209           rc = 0;
 210           break;
 211       }
 212       break;
 213     case GRAND_SEEDINT:
 214       i = va_arg(ap, unsigned);
 215       STORE32(buf, i);
 216       rc4_addkey(&g->rc4, buf, sizeof(buf));
 217       break;
 218     case GRAND_SEEDUINT32:
 219       i = va_arg(ap, uint32);
 220       STORE32(buf, i);
 221       rc4_addkey(&g->rc4, buf, sizeof(buf));
 222       break;
 223     case GRAND_SEEDBLOCK: {
 224       const void *p = va_arg(ap, const void *);
 225       size_t sz = va_arg(ap, size_t);
 226       rc4_addkey(&g->rc4, p, sz);
 227     } break;
 228     case GRAND_SEEDRAND: {
 229       grand *rr = va_arg(ap, grand *);
 230       octet buf[16];
 231       rr->ops->fill(rr, buf, sizeof(buf));
 232       rc4_addkey(&g->rc4, buf, sizeof(buf));
 233     } break;
 234     default:
 235       GRAND_BADOP;
 236       break;
 237   }
 238
 239   va_end(ap);
 240   return (rc);
 241 }
 242
 243 static octet grbyte(grand *r)
 244 {
 245   grctx *g = (grctx *)r;
 246   octet o;
 247   RC4_OPEN(&g->rc4, RC4_BYTE(o););
 248   return (o);
 249 }
 250
 251 static uint32 grword(grand *r)
 252 {
 253   grctx *g = (grctx *)r;
 254   octet b[4];
 255   int i;
 256   RC4_OPEN(&g->rc4,
 257            for (i = 0; i < sizeof(b); i++)
 258              RC4_BYTE(b[i]););
 259   return (LOAD32(b));
 260 }
 261
 262 static void grfill(grand *r, void *p, size_t sz)
 263 {
 264   grctx *g = (grctx *)r;
 265   rc4_encrypt(&g->rc4, 0, p, sz);
 266 }
 267
 268 static const grand_ops grops = {
 269   "rc4",
 270   GRAND_CRYPTO, 0,
 271   grmisc, grdestroy,
 272   grword, grbyte, grword, grand_range, grfill
 273 };
 274
 275 /* --- @rc4_rand@ --- *
 276  *
 277  * Arguments:   @const void *k@ = pointer to key material
 278  *              @size_t sz@ = size of key material
 279  *
 280  * Returns:     Pointer to generic random number generator interface.
 281  *
 282  * Use:         Creates a random number interface wrapper around an
 283  *              OFB-mode block cipher.
 284  */
 285
 286 grand *rc4_rand(const void *k, size_t sz)
 287 {
 288   grctx *g = S_CREATE(grctx);
 289   g->r.ops = &grops;
 290   rc4_init(&g->rc4, k, sz);
 291   return (&g->r);
 292 }
 293
 294 /*----- Test rig ----------------------------------------------------------*/
 295
 296 #ifdef TEST_RIG
 297
 298 #include <stdio.h>
 299 #include <string.h>
 300
 301 #include <mLib/quis.h>
 302 #include <mLib/testrig.h>
 303
 304 static int v_encrypt(dstr *v)
 305 {
 306   rc4_ctx ctx;
 307   dstr d = DSTR_INIT;
 308   int ok = 1;
 309
 310   rc4_init(&ctx, v[0].buf, v[0].len);
 311   dstr_ensure(&d, v[1].len);
 312   d.len = v[1].len;
 313   rc4_encrypt(&ctx, v[1].buf, d.buf, d.len);
 314
 315   if (memcmp(v[2].buf, d.buf, d.len) != 0) {
 316     ok = 0;
 317     printf("\nfail encryption:"
 318            "\n\tkey        = ");
 319     type_hex.dump(&v[0], stdout);
 320     printf("\n\tplaintext  = "); type_hex.dump(&v[1], stdout);
 321     printf("\n\texpected   = "); type_hex.dump(&v[2], stdout);
 322     printf("\n\tcalculated = "); type_hex.dump(&d, stdout);
 323     putchar('\n');
 324   }
 325
 326   return (ok);
 327 }
 328
 329 static int v_generate(dstr *v)
 330 {
 331   rc4_ctx ctx;
 332   dstr d = DSTR_INIT;
 333   int ok = 1;
 334
 335   rc4_init(&ctx, v[0].buf, v[0].len);
 336   rc4_encrypt(&ctx, 0, 0, *(int *)v[1].buf);
 337   dstr_ensure(&d, v[2].len);
 338   d.len = v[2].len;
 339   rc4_encrypt(&ctx, 0, d.buf, d.len);
 340
 341   if (memcmp(v[2].buf, d.buf, d.len) != 0) {
 342     ok = 0;
 343     printf("\nfail generation:"
 344            "\n\tkey        = ");
 345     type_hex.dump(&v[0], stdout);
 346     printf("\n\tskip len   = %i", *(int *)v[1].buf);
 347     printf("\n\texpected   = "); type_hex.dump(&v[2], stdout);
 348     printf("\n\tcalculated = "); type_hex.dump(&d, stdout);
 349     putchar('\n');
 350   }
 351
 352   return (ok);
 353 }
 354
 355 static test_chunk defs[] = {
 356   { "rc4-encrypt", v_encrypt, { &type_hex, &type_hex, &type_hex, 0 } },
 357   { "rc4-generate", v_generate, { &type_hex, &type_int, &type_hex, 0 } },
 358   { 0, 0, { 0 } }
 359 };
 360
 361 int main(int argc, char *argv[])
 362 {
 363   test_run(argc, argv, defs, SRCDIR"/tests/rc4");
 364   return (0);
 365 }
 366
 367 #endif
 368
 369 /*----- That's all, folks -------------------------------------------------*/