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rc4_enc.c
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1 /* crypto/rc4/rc4_enc.c */
2 /* Copyright (C) 1995-1998 Eric Young ([email protected])
3  * All rights reserved.
4  *
5  * This package is an SSL implementation written
6  * by Eric Young ([email protected]).
7  * The implementation was written so as to conform with Netscapes SSL.
8  *
9  * This library is free for commercial and non-commercial use as long as
10  * the following conditions are aheared to. The following conditions
11  * apply to all code found in this distribution, be it the RC4, RSA,
12  * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13  * included with this distribution is covered by the same copyright terms
14  * except that the holder is Tim Hudson ([email protected]).
15  *
16  * Copyright remains Eric Young's, and as such any Copyright notices in
17  * the code are not to be removed.
18  * If this package is used in a product, Eric Young should be given attribution
19  * as the author of the parts of the library used.
20  * This can be in the form of a textual message at program startup or
21  * in documentation (online or textual) provided with the package.
22  *
23  * Redistribution and use in source and binary forms, with or without
24  * modification, are permitted provided that the following conditions
25  * are met:
26  * 1. Redistributions of source code must retain the copyright
27  * notice, this list of conditions and the following disclaimer.
28  * 2. Redistributions in binary form must reproduce the above copyright
29  * notice, this list of conditions and the following disclaimer in the
30  * documentation and/or other materials provided with the distribution.
31  * 3. All advertising materials mentioning features or use of this software
32  * must display the following acknowledgement:
33  * "This product includes cryptographic software written by
34  * Eric Young ([email protected])"
35  * The word 'cryptographic' can be left out if the rouines from the library
36  * being used are not cryptographic related :-).
37  * 4. If you include any Windows specific code (or a derivative thereof) from
38  * the apps directory (application code) you must include an acknowledgement:
39  * "This product includes software written by Tim Hudson ([email protected])"
40  *
41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51  * SUCH DAMAGE.
52  *
53  * The licence and distribution terms for any publically available version or
54  * derivative of this code cannot be changed. i.e. this code cannot simply be
55  * copied and put under another distribution licence
56  * [including the GNU Public Licence.]
57  */
58 
59 #include <openssl/rc4.h>
60 #include "rc4_locl.h"
61 
62 /* RC4 as implemented from a posting from
63  * Newsgroups: sci.crypt
64  * From: [email protected] (David Sterndark)
65  * Subject: RC4 Algorithm revealed.
66  * Message-ID: <[email protected]>
67  * Date: Wed, 14 Sep 1994 06:35:31 GMT
68  */
69 
70 void RC4(RC4_KEY *key, size_t len, const unsigned char *indata,
71  unsigned char *outdata)
72  {
73  register RC4_INT *d;
74  register RC4_INT x,y,tx,ty;
75  size_t i;
76 
77  x=key->x;
78  y=key->y;
79  d=key->data;
80 
81 #if defined(RC4_CHUNK)
82  /*
83  * The original reason for implementing this(*) was the fact that
84  * pre-21164a Alpha CPUs don't have byte load/store instructions
85  * and e.g. a byte store has to be done with 64-bit load, shift,
86  * and, or and finally 64-bit store. Peaking data and operating
87  * at natural word size made it possible to reduce amount of
88  * instructions as well as to perform early read-ahead without
89  * suffering from RAW (read-after-write) hazard. This resulted
90  * in ~40%(**) performance improvement on 21064 box with gcc.
91  * But it's not only Alpha users who win here:-) Thanks to the
92  * early-n-wide read-ahead this implementation also exhibits
93  * >40% speed-up on SPARC and 20-30% on 64-bit MIPS (depending
94  * on sizeof(RC4_INT)).
95  *
96  * (*) "this" means code which recognizes the case when input
97  * and output pointers appear to be aligned at natural CPU
98  * word boundary
99  * (**) i.e. according to 'apps/openssl speed rc4' benchmark,
100  * crypto/rc4/rc4speed.c exhibits almost 70% speed-up...
101  *
102  * Cavets.
103  *
104  * - RC4_CHUNK="unsigned long long" should be a #1 choice for
105  * UltraSPARC. Unfortunately gcc generates very slow code
106  * (2.5-3 times slower than one generated by Sun's WorkShop
107  * C) and therefore gcc (at least 2.95 and earlier) should
108  * always be told that RC4_CHUNK="unsigned long".
109  *
110  * <[email protected]>
111  */
112 
113 # define RC4_STEP ( \
114  x=(x+1) &0xff, \
115  tx=d[x], \
116  y=(tx+y)&0xff, \
117  ty=d[y], \
118  d[y]=tx, \
119  d[x]=ty, \
120  (RC4_CHUNK)d[(tx+ty)&0xff]\
121  )
122 
123  if ( ( ((size_t)indata & (sizeof(RC4_CHUNK)-1)) |
124  ((size_t)outdata & (sizeof(RC4_CHUNK)-1)) ) == 0 )
125  {
126  RC4_CHUNK ichunk,otp;
127  const union { long one; char little; } is_endian = {1};
128 
129  /*
130  * I reckon we can afford to implement both endian
131  * cases and to decide which way to take at run-time
132  * because the machine code appears to be very compact
133  * and redundant 1-2KB is perfectly tolerable (i.e.
134  * in case the compiler fails to eliminate it:-). By
135  * suggestion from Terrel Larson <[email protected]>
136  * who also stands for the is_endian union:-)
137  *
138  * Special notes.
139  *
140  * - is_endian is declared automatic as doing otherwise
141  * (declaring static) prevents gcc from eliminating
142  * the redundant code;
143  * - compilers (those I've tried) don't seem to have
144  * problems eliminating either the operators guarded
145  * by "if (sizeof(RC4_CHUNK)==8)" or the condition
146  * expressions themselves so I've got 'em to replace
147  * corresponding #ifdefs from the previous version;
148  * - I chose to let the redundant switch cases when
149  * sizeof(RC4_CHUNK)!=8 be (were also #ifdefed
150  * before);
151  * - in case you wonder "&(sizeof(RC4_CHUNK)*8-1)" in
152  * [LB]ESHFT guards against "shift is out of range"
153  * warnings when sizeof(RC4_CHUNK)!=8
154  *
155  * <[email protected]>
156  */
157  if (!is_endian.little)
158  { /* BIG-ENDIAN CASE */
159 # define BESHFT(c) (((sizeof(RC4_CHUNK)-(c)-1)*8)&(sizeof(RC4_CHUNK)*8-1))
160  for (;len&(0-sizeof(RC4_CHUNK));len-=sizeof(RC4_CHUNK))
161  {
162  ichunk = *(RC4_CHUNK *)indata;
163  otp = RC4_STEP<<BESHFT(0);
164  otp |= RC4_STEP<<BESHFT(1);
165  otp |= RC4_STEP<<BESHFT(2);
166  otp |= RC4_STEP<<BESHFT(3);
167  if (sizeof(RC4_CHUNK)==8)
168  {
169  otp |= RC4_STEP<<BESHFT(4);
170  otp |= RC4_STEP<<BESHFT(5);
171  otp |= RC4_STEP<<BESHFT(6);
172  otp |= RC4_STEP<<BESHFT(7);
173  }
174  *(RC4_CHUNK *)outdata = otp^ichunk;
175  indata += sizeof(RC4_CHUNK);
176  outdata += sizeof(RC4_CHUNK);
177  }
178  if (len)
179  {
180  RC4_CHUNK mask=(RC4_CHUNK)-1, ochunk;
181 
182  ichunk = *(RC4_CHUNK *)indata;
183  ochunk = *(RC4_CHUNK *)outdata;
184  otp = 0;
185  i = BESHFT(0);
186  mask <<= (sizeof(RC4_CHUNK)-len)<<3;
187  switch (len&(sizeof(RC4_CHUNK)-1))
188  {
189  case 7: otp = RC4_STEP<<i, i-=8;
190  case 6: otp |= RC4_STEP<<i, i-=8;
191  case 5: otp |= RC4_STEP<<i, i-=8;
192  case 4: otp |= RC4_STEP<<i, i-=8;
193  case 3: otp |= RC4_STEP<<i, i-=8;
194  case 2: otp |= RC4_STEP<<i, i-=8;
195  case 1: otp |= RC4_STEP<<i, i-=8;
196  case 0: ; /*
197  * it's never the case,
198  * but it has to be here
199  * for ultrix?
200  */
201  }
202  ochunk &= ~mask;
203  ochunk |= (otp^ichunk) & mask;
204  *(RC4_CHUNK *)outdata = ochunk;
205  }
206  key->x=x;
207  key->y=y;
208  return;
209  }
210  else
211  { /* LITTLE-ENDIAN CASE */
212 # define LESHFT(c) (((c)*8)&(sizeof(RC4_CHUNK)*8-1))
213  for (;len&(0-sizeof(RC4_CHUNK));len-=sizeof(RC4_CHUNK))
214  {
215  ichunk = *(RC4_CHUNK *)indata;
216  otp = RC4_STEP;
217  otp |= RC4_STEP<<8;
218  otp |= RC4_STEP<<16;
219  otp |= RC4_STEP<<24;
220  if (sizeof(RC4_CHUNK)==8)
221  {
222  otp |= RC4_STEP<<LESHFT(4);
223  otp |= RC4_STEP<<LESHFT(5);
224  otp |= RC4_STEP<<LESHFT(6);
225  otp |= RC4_STEP<<LESHFT(7);
226  }
227  *(RC4_CHUNK *)outdata = otp^ichunk;
228  indata += sizeof(RC4_CHUNK);
229  outdata += sizeof(RC4_CHUNK);
230  }
231  if (len)
232  {
233  RC4_CHUNK mask=(RC4_CHUNK)-1, ochunk;
234 
235  ichunk = *(RC4_CHUNK *)indata;
236  ochunk = *(RC4_CHUNK *)outdata;
237  otp = 0;
238  i = 0;
239  mask >>= (sizeof(RC4_CHUNK)-len)<<3;
240  switch (len&(sizeof(RC4_CHUNK)-1))
241  {
242  case 7: otp = RC4_STEP, i+=8;
243  case 6: otp |= RC4_STEP<<i, i+=8;
244  case 5: otp |= RC4_STEP<<i, i+=8;
245  case 4: otp |= RC4_STEP<<i, i+=8;
246  case 3: otp |= RC4_STEP<<i, i+=8;
247  case 2: otp |= RC4_STEP<<i, i+=8;
248  case 1: otp |= RC4_STEP<<i, i+=8;
249  case 0: ; /*
250  * it's never the case,
251  * but it has to be here
252  * for ultrix?
253  */
254  }
255  ochunk &= ~mask;
256  ochunk |= (otp^ichunk) & mask;
257  *(RC4_CHUNK *)outdata = ochunk;
258  }
259  key->x=x;
260  key->y=y;
261  return;
262  }
263  }
264 #endif
265 #define LOOP(in,out) \
266  x=((x+1)&0xff); \
267  tx=d[x]; \
268  y=(tx+y)&0xff; \
269  d[x]=ty=d[y]; \
270  d[y]=tx; \
271  (out) = d[(tx+ty)&0xff]^ (in);
272 
273 #ifndef RC4_INDEX
274 #define RC4_LOOP(a,b,i) LOOP(*((a)++),*((b)++))
275 #else
276 #define RC4_LOOP(a,b,i) LOOP(a[i],b[i])
277 #endif
278 
279  i=len>>3;
280  if (i)
281  {
282  for (;;)
283  {
284  RC4_LOOP(indata,outdata,0);
285  RC4_LOOP(indata,outdata,1);
286  RC4_LOOP(indata,outdata,2);
287  RC4_LOOP(indata,outdata,3);
288  RC4_LOOP(indata,outdata,4);
289  RC4_LOOP(indata,outdata,5);
290  RC4_LOOP(indata,outdata,6);
291  RC4_LOOP(indata,outdata,7);
292 #ifdef RC4_INDEX
293  indata+=8;
294  outdata+=8;
295 #endif
296  if (--i == 0) break;
297  }
298  }
299  i=len&0x07;
300  if (i)
301  {
302  for (;;)
303  {
304  RC4_LOOP(indata,outdata,0); if (--i == 0) break;
305  RC4_LOOP(indata,outdata,1); if (--i == 0) break;
306  RC4_LOOP(indata,outdata,2); if (--i == 0) break;
307  RC4_LOOP(indata,outdata,3); if (--i == 0) break;
308  RC4_LOOP(indata,outdata,4); if (--i == 0) break;
309  RC4_LOOP(indata,outdata,5); if (--i == 0) break;
310  RC4_LOOP(indata,outdata,6); if (--i == 0) break;
311  }
312  }
313  key->x=x;
314  key->y=y;
315  }
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