ermyth/src/arc4random.C

/*
 * Arc4 random number generator for OpenBSD.
 * Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
 *
 * Modification and redistribution in source and binary forms is
 * permitted provided that due credit is given to the author and the
 * OpenBSD project (for instance by leaving this copyright notice
 * intact).
 */

/*
 * This code is derived from section 17.1 of Applied Cryptography,
 * second edition, which describes a stream cipher allegedly
 * compatible with RSA Labs "RC4" cipher (the actual description of
 * which is a trade secret).  The same algorithm is used as a stream
 * cipher called "arcfour" in Tatu Ylonen's ssh package.
 *
 * Here the stream cipher has been modified always to include the time
 * when initializing the state.  That makes it impossible to
 * regenerate the same random sequence twice, so this can't be used
 * for encryption, but will generate good random numbers.
 *
 * RC4 is a registered trademark of RSA Laboratories.
 */

/*
 * $FreeBSD: /usr/local/www/cvsroot/FreeBSD/src/lib/libc/gen/arc4random.c,v 1.10.8.1 2006/11/18 21:35:13 ache Exp $
 * Modified for Atheme by Jilles Tjoelker
 * $Id: arc4random.C,v 1.1 2007-07-19 08:24:56 pippijn Exp $
 */

#include "atheme.h"

#ifndef HAVE_ARC4RANDOM

struct arc4_stream
{
  unsigned char i;
  unsigned char j;
  unsigned char s[256];
};

#define RANDOMDEV       "/dev/urandom"

static struct arc4_stream rs;
static int rs_initialized;
static int rs_stired;
static int arc4_count;

static inline unsigned char arc4_getbyte (struct arc4_stream *);
static void arc4_stir (struct arc4_stream *);

static inline void
arc4_init (struct arc4_stream *as)
{
  int n;

  for (n = 0; n < 256; n++)
    as->s[n] = n;
  as->i = 0;
  as->j = 0;
}

static inline void
arc4_addrandom (struct arc4_stream *as, unsigned char *dat, int datlen)
{
  int n;
  unsigned char si;

  as->i--;
  for (n = 0; n < 256; n++)
    {
      as->i = (as->i + 1);
      si = as->s[as->i];
      as->j = (as->j + si + dat[n % datlen]);
      as->s[as->i] = as->s[as->j];
      as->s[as->j] = si;
    }
}

static void
arc4_stir (struct arc4_stream *as)
{
  int fd, n;
  struct
  {
    struct timeval tv;
    pid_t pid;
    unsigned char rnd[128 - sizeof (struct timeval) - sizeof (pid_t)];
  }
  rdat;

  gettimeofday (&rdat.tv, NULL);
  rdat.pid = getpid ();
  fd = open (RANDOMDEV, O_RDONLY, 0);
  if (fd >= 0)
    {
      (void) read (fd, rdat.rnd, sizeof (rdat.rnd));
      close (fd);
    }
  /* fd < 0?  Ah, what the heck. We'll just take whatever was on the
   * stack... */

  arc4_addrandom (as, (unsigned char *) &rdat, sizeof (rdat));

  /*
   * Throw away the first N bytes of output, as suggested in the
   * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
   * by Fluher, Mantin, and Shamir.  N=1024 is based on
   * suggestions in the paper "(Not So) Random Shuffles of RC4"
   * by Ilya Mironov.
   */
  for (n = 0; n < 1024; n++)
    (void) arc4_getbyte (as);
  arc4_count = 400000;
}

static inline unsigned char
arc4_getbyte (struct arc4_stream *as)
{
  unsigned char si, sj;

  as->i = (as->i + 1);
  si = as->s[as->i];
  as->j = (as->j + si);
  sj = as->s[as->j];
  as->s[as->i] = sj;
  as->s[as->j] = si;

  return (as->s[(si + sj) & 0xff]);
}

static inline unsigned int
arc4_getword (struct arc4_stream *as)
{
  unsigned int val;

  val = arc4_getbyte (as) << 24;
  val |= arc4_getbyte (as) << 16;
  val |= arc4_getbyte (as) << 8;
  val |= arc4_getbyte (as);

  return (val);
}

static void
arc4_check_init (void)
{
  if (rs_initialized)
    return;

  arc4_init (&rs);
  rs_initialized = 1;
}

static void
arc4_check_stir (void)
{
  if (!rs_stired || --arc4_count == 0)
    {
      arc4_stir (&rs);
      rs_stired = 1;
    }
}

void
arc4random_stir ()
{
  arc4_check_init ();
  arc4_stir (&rs);
}

void
arc4random_addrandom (unsigned char *dat, int datlen)
{
  arc4_check_init ();
  arc4_check_stir ();
  arc4_addrandom (&rs, dat, datlen);
}

unsigned int
arc4random (void)
{
  unsigned int rnd;

  arc4_check_init ();
  arc4_check_stir ();
  rnd = arc4_getword (&rs);

  return (rnd);
}

/* vim:cinoptions=>s,e0,n0,f0,{0,}0,^0,=s,ps,t0,c3,+s,(2s,us,)20,*30,gs,hs
 * vim:ts=8
 * vim:sw=8
 * vim:noexpandtab
 */

#endif /* !HAVE_ARC4RANDOM */
Revision:	1.2
Committed:	Tue Aug 28 17:12:24 2007 UTC (19 years ago) by pippijn
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.1:	+1 -1 lines
State:	*FILE REMOVED*
Log Message:	removed old files
#	User	Rev	Content
1	pippijn	1.1	/*
2			* Arc4 random number generator for OpenBSD.
3			* Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
4			*
5			* Modification and redistribution in source and binary forms is
6			* permitted provided that due credit is given to the author and the
7			* OpenBSD project (for instance by leaving this copyright notice
8			* intact).
9			*/
10
11			/*
12			* This code is derived from section 17.1 of Applied Cryptography,
13			* second edition, which describes a stream cipher allegedly
14			* compatible with RSA Labs "RC4" cipher (the actual description of
15			* which is a trade secret). The same algorithm is used as a stream
16			* cipher called "arcfour" in Tatu Ylonen's ssh package.
17			*
18			* Here the stream cipher has been modified always to include the time
19			* when initializing the state. That makes it impossible to
20			* regenerate the same random sequence twice, so this can't be used
21			* for encryption, but will generate good random numbers.
22			*
23			* RC4 is a registered trademark of RSA Laboratories.
24			*/
25
26			/*
27			* $FreeBSD: /usr/local/www/cvsroot/FreeBSD/src/lib/libc/gen/arc4random.c,v 1.10.8.1 2006/11/18 21:35:13 ache Exp $
28			* Modified for Atheme by Jilles Tjoelker
29	pippijn	1.2	* $Id: arc4random.C,v 1.1 2007-07-19 08:24:56 pippijn Exp $
30	pippijn	1.1	*/
31
32			#include "atheme.h"
33
34			#ifndef HAVE_ARC4RANDOM
35
36			struct arc4_stream
37			{
38			unsigned char i;
39			unsigned char j;
40			unsigned char s[256];
41			};
42
43			#define RANDOMDEV "/dev/urandom"
44
45			static struct arc4_stream rs;
46			static int rs_initialized;
47			static int rs_stired;
48			static int arc4_count;
49
50			static inline unsigned char arc4_getbyte (struct arc4_stream *);
51			static void arc4_stir (struct arc4_stream *);
52
53			static inline void
54			arc4_init (struct arc4_stream *as)
55			{
56			int n;
57
58			for (n = 0; n < 256; n++)
59			as->s[n] = n;
60			as->i = 0;
61			as->j = 0;
62			}
63
64			static inline void
65			arc4_addrandom (struct arc4_stream as, unsigned char dat, int datlen)
66			{
67			int n;
68			unsigned char si;
69
70			as->i--;
71			for (n = 0; n < 256; n++)
72			{
73			as->i = (as->i + 1);
74			si = as->s[as->i];
75			as->j = (as->j + si + dat[n % datlen]);
76			as->s[as->i] = as->s[as->j];
77			as->s[as->j] = si;
78			}
79			}
80
81			static void
82			arc4_stir (struct arc4_stream *as)
83			{
84			int fd, n;
85			struct
86			{
87			struct timeval tv;
88			pid_t pid;
89			unsigned char rnd[128 - sizeof (struct timeval) - sizeof (pid_t)];
90			}
91			rdat;
92
93			gettimeofday (&rdat.tv, NULL);
94			rdat.pid = getpid ();
95			fd = open (RANDOMDEV, O_RDONLY, 0);
96			if (fd >= 0)
97			{
98			(void) read (fd, rdat.rnd, sizeof (rdat.rnd));
99			close (fd);
100			}
101			/* fd < 0? Ah, what the heck. We'll just take whatever was on the
102			* stack... */
103
104			arc4_addrandom (as, (unsigned char *) &rdat, sizeof (rdat));
105
106			/*
107			* Throw away the first N bytes of output, as suggested in the
108			* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
109			* by Fluher, Mantin, and Shamir. N=1024 is based on
110			* suggestions in the paper "(Not So) Random Shuffles of RC4"
111			* by Ilya Mironov.
112			*/
113			for (n = 0; n < 1024; n++)
114			(void) arc4_getbyte (as);
115			arc4_count = 400000;
116			}
117
118			static inline unsigned char
119			arc4_getbyte (struct arc4_stream *as)
120			{
121			unsigned char si, sj;
122
123			as->i = (as->i + 1);
124			si = as->s[as->i];
125			as->j = (as->j + si);
126			sj = as->s[as->j];
127			as->s[as->i] = sj;
128			as->s[as->j] = si;
129
130			return (as->s[(si + sj) & 0xff]);
131			}
132
133			static inline unsigned int
134			arc4_getword (struct arc4_stream *as)
135			{
136			unsigned int val;
137
138			val = arc4_getbyte (as) << 24;
139			val \|= arc4_getbyte (as) << 16;
140			val \|= arc4_getbyte (as) << 8;
141			val \|= arc4_getbyte (as);
142
143			return (val);
144			}
145
146			static void
147			arc4_check_init (void)
148			{
149			if (rs_initialized)
150			return;
151
152			arc4_init (&rs);
153			rs_initialized = 1;
154			}
155
156			static void
157			arc4_check_stir (void)
158			{
159			if (!rs_stired \|\| --arc4_count == 0)
160			{
161			arc4_stir (&rs);
162			rs_stired = 1;
163			}
164			}
165
166			void
167			arc4random_stir ()
168			{
169			arc4_check_init ();
170			arc4_stir (&rs);
171			}
172
173			void
174			arc4random_addrandom (unsigned char *dat, int datlen)
175			{
176			arc4_check_init ();
177			arc4_check_stir ();
178			arc4_addrandom (&rs, dat, datlen);
179			}
180
181			unsigned int
182			arc4random (void)
183			{
184			unsigned int rnd;
185
186			arc4_check_init ();
187			arc4_check_stir ();
188			rnd = arc4_getword (&rs);
189
190			return (rnd);
191			}
192
193			/* vim:cinoptions=>s,e0,n0,f0,{0,}0,^0,=s,ps,t0,c3,+s,(2s,us,)20,*30,gs,hs
194			* vim:ts=8
195			* vim:sw=8
196			* vim:noexpandtab
197			*/
198
199			#endif /* !HAVE_ARC4RANDOM */