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   1 /* -*-c-*-
   2  *
   3  * $Id: rc4.c,v 1.5 2001/04/03 19:36:36 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: rc4.c,v $
  33  * Revision 1.5  2001/04/03 19:36:36  mdw
  34  * Don't use @va_arg@ as an argument to @STORE32@!
  35  *
  36  * Revision 1.4  2000/06/17 11:55:22  mdw
  37  * New key size interface.  Allow key material to be combined with an
  38  * existing initialized context.  Use secure arena for memory allocation.
  39  *
  40  * Revision 1.3  1999/12/13 15:34:01  mdw
  41  * Add support for seeding from a generic pseudorandom source.
  42  *
  43  * Revision 1.2  1999/12/10 23:27:35  mdw
  44  * Generic cipher and RNG interfaces.
  45  *
  46  * Revision 1.1  1999/09/03 08:41:12  mdw
  47  * Initial import.
  48  *
  49  */
  50
  51 /*----- Header files ------------------------------------------------------*/
  52
  53 #include <assert.h>
  54 #include <stdarg.h>
  55 #include <stdio.h>
  56
  57 #include <mLib/bits.h>
  58 #include <mLib/sub.h>
  59
  60 #include "arena.h"
  61 #include "gcipher.h"
  62 #include "grand.h"
  63 #include "paranoia.h"
  64 #include "rc4.h"
  65
  66 /*----- Global variables --------------------------------------------------*/
  67
  68 const octet rc4_keysz[] = { KSZ_RANGE, RC4_KEYSZ, 1, 255, 1 };
  69
  70 /*----- Main code ---------------------------------------------------------*/
  71
  72 /* --- @rc4_addkey@ --- *
  73  *
  74  * Arguments:   @rc4_ctx *ctx@ = pointer to context to key
  75  *              @const void *k@ = pointer to key data to use
  76  *              @size_t sz@ = size of the key data
  77  *
  78  * Returns:     ---
  79  *
  80  * Use:         Mixes key data with an RC4 context.  The RC4 context is not
  81  *              reset before mixing.  This may be used to mix new key
  82  *              material with an existing RC4 context.
  83  */
  84
  85 void rc4_addkey(rc4_ctx *ctx, const void *k, size_t sz)
  86 {
  87   unsigned i, j;
  88   const octet *p = k, *q = p + sz;
  89
  90   KSZ_ASSERT(rc4, sz);
  91
  92   for (i = j = 0; i < 256; i++) {
  93     unsigned si = ctx->s[i];
  94     j = (j + si + *p++) & 0xff;
  95     ctx->s[i] = ctx->s[j];
  96     ctx->s[j] = si;
  97     if (p == q)
  98       p = k;
  99   }
 100
 101   ctx->i = ctx->j = 0;
 102 }
 103
 104 /* --- @rc4_init@ --- *
 105  *
 106  * Arguments:   @rc4_ctx *ctx@ = pointer to context to initialize
 107  *              @const void *k@ = pointer to key data to use
 108  *              @size_t sz@ = size of the key data
 109  *
 110  * Returns:     ---
 111  *
 112  * Use:         Initializes an RC4 context ready for use.
 113  */
 114
 115 void rc4_init(rc4_ctx *ctx, const void *k, size_t sz)
 116 {
 117   unsigned i;
 118
 119   for (i = 0; i < 256; i++)
 120     ctx->s[i] = i;
 121   ctx->f = 0;
 122   rc4_addkey(ctx, k, sz);
 123 }
 124
 125 /* --- @rc4_encrypt@ --- *
 126  *
 127  * Arguments:   @rc4_ctx *ctx@ = pointer to context to use
 128  *              @const void *src@ = pointer to the source block
 129  *              @void *dest@ = pointer to the destination block
 130  *              @size_t sz@ = size of the block
 131  *
 132  * Returns:     ---
 133  *
 134  * Use:         Encrypts or decrypts a block of data.  The destination may
 135  *              be null to just grind the generator around for a while.  It's
 136  *              recommended that you say `@rc4_encrypt(&ctx, 0, 0, 1024)@'
 137  *              after initializing a new context, to prevent keystream
 138  *              guessing attacks.  The source may be null to just extract a
 139  *              big lump of data from the generator.
 140  */
 141
 142 void rc4_encrypt(rc4_ctx *ctx, const void *src, void *dest, size_t sz)
 143 {
 144   const octet *s = src;
 145   octet *d = dest;
 146
 147   if (!d)
 148     RC4_OPEN(ctx, while (sz) { unsigned x; RC4_BYTE(x); sz--; });
 149   else if (!s)
 150     RC4_OPEN(ctx, while (sz) { RC4_BYTE(*d++); sz--; });
 151   else
 152     RC4_OPEN(ctx,
 153              while (sz) { unsigned x; RC4_BYTE(x); *d++ = *s++ ^ x; sz--; });
 154 }
 155
 156 /*----- Generic cipher interface ------------------------------------------*/
 157
 158 typedef struct gctx {
 159   gcipher c;
 160   rc4_ctx rc4;
 161 } gctx;
 162
 163 static const gcipher_ops gops;
 164
 165 static gcipher *ginit(const void *k, size_t sz)
 166 {
 167   gctx *g = S_CREATE(gctx);
 168   g->c.ops = &gops;
 169   rc4_init(&g->rc4, k, sz);
 170   return (&g->c);
 171 }
 172
 173 static void gencrypt(gcipher *c, const void *s, void *t, size_t sz)
 174 {
 175   gctx *g = (gctx *)c;
 176   rc4_encrypt(&g->rc4, s, t, sz);
 177 }
 178
 179 static void gdestroy(gcipher *c)
 180 {
 181   gctx *g = (gctx *)c;
 182   BURN(*g);
 183   S_DESTROY(g);
 184 }
 185
 186 static const gcipher_ops gops = {
 187   &rc4,
 188   gencrypt, gencrypt, gdestroy, 0, 0
 189 };
 190
 191 const gccipher rc4 = {
 192   "rc4", rc4_keysz, 0,
 193   ginit
 194 };
 195
 196 /*----- Generic random number generator interface -------------------------*/
 197
 198 typedef struct grctx {
 199   grand r;
 200   rc4_ctx rc4;
 201 } grctx;
 202
 203 static void grdestroy(grand *r)
 204 {
 205   grctx *g = (grctx *)r;
 206   BURN(*g);
 207   S_DESTROY(g);
 208 }
 209
 210 static int grmisc(grand *r, unsigned op, ...)
 211 {
 212   grctx *g = (grctx *)r;
 213   va_list ap;
 214   int rc = 0;
 215   uint32 i;
 216   octet buf[4];
 217   va_start(ap, op);
 218
 219   switch (op) {
 220     case GRAND_CHECK:
 221       switch (va_arg(ap, unsigned)) {
 222         case GRAND_CHECK:
 223         case GRAND_SEEDINT:
 224         case GRAND_SEEDUINT32:
 225         case GRAND_SEEDBLOCK:
 226         case GRAND_SEEDRAND:
 227           rc = 1;
 228           break;
 229         default:
 230           rc = 0;
 231           break;
 232       }
 233       break;
 234     case GRAND_SEEDINT:
 235       i = va_arg(ap, unsigned);
 236       STORE32(buf, i);
 237       rc4_addkey(&g->rc4, buf, sizeof(buf));
 238       break;
 239     case GRAND_SEEDUINT32:
 240       i = va_arg(ap, uint32);
 241       STORE32(buf, i);
 242       rc4_addkey(&g->rc4, buf, sizeof(buf));
 243       break;
 244     case GRAND_SEEDBLOCK: {
 245       const void *p = va_arg(ap, const void *);
 246       size_t sz = va_arg(ap, size_t);
 247       rc4_addkey(&g->rc4, p, sz);
 248     } break;
 249     case GRAND_SEEDRAND: {
 250       grand *rr = va_arg(ap, grand *);
 251       octet buf[16];
 252       rr->ops->fill(rr, buf, sizeof(buf));
 253       rc4_addkey(&g->rc4, buf, sizeof(buf));
 254     } break;
 255     default:
 256       GRAND_BADOP;
 257       break;
 258   }
 259
 260   va_end(ap);
 261   return (rc);
 262 }
 263
 264 static octet grbyte(grand *r)
 265 {
 266   grctx *g = (grctx *)r;
 267   octet o;
 268   RC4_OPEN(&g->rc4, RC4_BYTE(o););
 269   return (o);
 270 }
 271
 272 static uint32 grword(grand *r)
 273 {
 274   grctx *g = (grctx *)r;
 275   octet b[4];
 276   int i;
 277   RC4_OPEN(&g->rc4,
 278            for (i = 0; i < sizeof(b); i++)
 279              RC4_BYTE(b[i]););
 280   return (LOAD32(b));
 281 }
 282
 283 static void grfill(grand *r, void *p, size_t sz)
 284 {
 285   grctx *g = (grctx *)r;
 286   rc4_encrypt(&g->rc4, 0, p, sz);
 287 }
 288
 289 static const grand_ops grops = {
 290   "rc4",
 291   GRAND_CRYPTO, 0,
 292   grmisc, grdestroy,
 293   grword, grbyte, grword, grand_range, grfill
 294 };
 295
 296 /* --- @rc4_rand@ --- *
 297  *
 298  * Arguments:   @const void *k@ = pointer to key material
 299  *              @size_t sz@ = size of key material
 300  *
 301  * Returns:     Pointer to generic random number generator interface.
 302  *
 303  * Use:         Creates a random number interface wrapper around an
 304  *              OFB-mode block cipher.
 305  */
 306
 307 grand *rc4_rand(const void *k, size_t sz)
 308 {
 309   grctx *g = S_CREATE(grctx);
 310   g->r.ops = &grops;
 311   rc4_init(&g->rc4, k, sz);
 312   return (&g->r);
 313 }
 314
 315 /*----- Test rig ----------------------------------------------------------*/
 316
 317 #ifdef TEST_RIG
 318
 319 #include <stdio.h>
 320 #include <string.h>
 321
 322 #include <mLib/quis.h>
 323 #include <mLib/testrig.h>
 324
 325 static int v_encrypt(dstr *v)
 326 {
 327   rc4_ctx ctx;
 328   dstr d = DSTR_INIT;
 329   int ok = 1;
 330
 331   rc4_init(&ctx, v[0].buf, v[0].len);
 332   dstr_ensure(&d, v[1].len);
 333   d.len = v[1].len;
 334   rc4_encrypt(&ctx, v[1].buf, d.buf, d.len);
 335
 336   if (memcmp(v[2].buf, d.buf, d.len) != 0) {
 337     ok = 0;
 338     printf("\nfail encryption:"
 339            "\n\tkey        = ");
 340     type_hex.dump(&v[0], stdout);
 341     printf("\n\tplaintext  = "); type_hex.dump(&v[1], stdout);
 342     printf("\n\texpected   = "); type_hex.dump(&v[2], stdout);
 343     printf("\n\tcalculated = "); type_hex.dump(&d, stdout);
 344     putchar('\n');
 345   }
 346
 347   return (ok);
 348 }
 349
 350 static int v_generate(dstr *v)
 351 {
 352   rc4_ctx ctx;
 353   dstr d = DSTR_INIT;
 354   int ok = 1;
 355
 356   rc4_init(&ctx, v[0].buf, v[0].len);
 357   rc4_encrypt(&ctx, 0, 0, *(int *)v[1].buf);
 358   dstr_ensure(&d, v[2].len);
 359   d.len = v[2].len;
 360   rc4_encrypt(&ctx, 0, d.buf, d.len);
 361
 362   if (memcmp(v[2].buf, d.buf, d.len) != 0) {
 363     ok = 0;
 364     printf("\nfail generation:"
 365            "\n\tkey        = ");
 366     type_hex.dump(&v[0], stdout);
 367     printf("\n\tskip len   = %i", *(int *)v[1].buf);
 368     printf("\n\texpected   = "); type_hex.dump(&v[2], stdout);
 369     printf("\n\tcalculated = "); type_hex.dump(&d, stdout);
 370     putchar('\n');
 371   }
 372
 373   return (ok);
 374 }
 375
 376 static test_chunk defs[] = {
 377   { "rc4-encrypt", v_encrypt, { &type_hex, &type_hex, &type_hex, 0 } },
 378   { "rc4-generate", v_generate, { &type_hex, &type_int, &type_hex, 0 } },
 379   { 0, 0, { 0 } }
 380 };
 381
 382 int main(int argc, char *argv[])
 383 {
 384   test_run(argc, argv, defs, SRCDIR"/tests/rc4");
 385   return (0);
 386 }
 387
 388 #endif
 389
 390 /*----- That's all, folks -------------------------------------------------*/