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