Date: Thu, 29 May 2014 21:04:11 -0400 From: Ted Unangst <tedu@tedunangst.com> To: freebsd-hackers@freebsd.org Subject: switch arc4random to chacha Message-ID: <f0b9ae8e7b2a40a9ab253438261c2c75@tedunangst.com>
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This syncs libc arc4random.c with OpenBSD, mostly to change the
implementation to ChaCha20.
I removed the more complicated seed fetching code and changed it to
just sysctl(). A quick check revealed that the FreeBSD kernel supports
this for at least five years now. It's much simpler to use code that
always works instead of a series of untested fallbacks that are even
less likely to work.
Also removes the addrandom interface as a useless complication. If the
kernel is incapable of properly seeding arc4random, application code
can't do any better.
Unfortunately, I don't have any FreeBSD systems running at the moment,
so I can't make any promises that this will even compile, but it
passed the eyeball test.
--- arc4random.c.orig Thu May 29 20:28:49 2014
+++ arc4random.c Thu May 29 20:51:59 2014
@@ -1,8 +1,9 @@
-/* $OpenBSD: arc4random.c,v 1.22 2010/12/22 08:23:42 otto Exp $ */
+/* $OpenBSD: arc4random.c,v 1.30 2014/05/06 16:06:33 tedu Exp $ */
/*
* Copyright (c) 1996, David Mazieres <dm@uun.org>
* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
+ * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
@@ -18,15 +19,7 @@
*/
/*
- * Arc4 random number generator for OpenBSD.
- *
- * 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.
- *
- * RC4 is a registered trademark of RSA Laboratories.
+ * ChaCha based random number generator for OpenBSD.
*/
#include <sys/cdefs.h>
@@ -40,28 +33,24 @@
#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysctl.h>
+#include <sys/mman.h>
#include <sys/time.h>
#include <pthread.h>
#include "libc_private.h"
#include "un-namespace.h"
+#define KEYSTREAM_ONLY
+#include "chacha_private.h"
+
#ifdef __GNUC__
#define inline __inline
#else /* !__GNUC__ */
#define inline
#endif /* !__GNUC__ */
-struct arc4_stream {
- u_int8_t i;
- u_int8_t j;
- u_int8_t s[256];
-};
-
static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
-#define RANDOMDEV "/dev/random"
-#define KEYSIZE 128
#define _ARC4_LOCK() \
do { \
if (__isthreaded) \
@@ -74,187 +63,149 @@
_pthread_mutex_unlock(&arc4random_mtx); \
} while (0)
+#define KEYSZ 32
+#define IVSZ 8
+#define BLOCKSZ 64
+#define RSBUFSZ (16*BLOCKSZ)
static int rs_initialized;
-static struct arc4_stream rs;
-static pid_t arc4_stir_pid;
-static int arc4_count;
+static pid_t rs_stir_pid;
+static chacha_ctx *rs; /* chacha context for random keystream */
+static u_char *rs_buf; /* keystream blocks */
+static size_t rs_have; /* valid bytes at end of rs_buf */
+static size_t rs_count; /* bytes till reseed */
+static inline void _rs_rekey(u_char *dat, size_t datlen);
+
extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
void *newp, size_t newlen);
-static inline u_int8_t arc4_getbyte(void);
-static void arc4_stir(void);
-
static inline void
-arc4_init(void)
+_rs_init(u_char *buf, size_t n)
{
- int n;
+ if (n < KEYSZ + IVSZ)
+ return;
- for (n = 0; n < 256; n++)
- rs.s[n] = n;
- rs.i = 0;
- rs.j = 0;
-}
+ if (rs == NULL && (rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE,
+ MAP_ANON, -1, 0)) == MAP_FAILED)
+ abort();
+ if (rs_buf == NULL && (rs_buf = mmap(NULL, RSBUFSZ, PROT_READ|PROT_WRITE,
+ MAP_ANON, -1, 0)) == MAP_FAILED)
+ abort();
-static inline void
-arc4_addrandom(u_char *dat, int datlen)
-{
- int n;
- u_int8_t si;
-
- rs.i--;
- for (n = 0; n < 256; n++) {
- rs.i = (rs.i + 1);
- si = rs.s[rs.i];
- rs.j = (rs.j + si + dat[n % datlen]);
- rs.s[rs.i] = rs.s[rs.j];
- rs.s[rs.j] = si;
- }
- rs.j = rs.i;
+ chacha_keysetup(rs, buf, KEYSZ * 8, 0);
+ chacha_ivsetup(rs, buf + KEYSZ);
}
-static size_t
-arc4_sysctl(u_char *buf, size_t size)
+static void
+_rs_stir(void)
{
- int mib[2];
- size_t len, done;
+ int mib[2];
+ size_t len;
+ u_char rnd[KEYSZ + IVSZ];
mib[0] = CTL_KERN;
mib[1] = KERN_ARND;
- done = 0;
- do {
- len = size;
- if (__sysctl(mib, 2, buf, &len, NULL, 0) == -1)
- return (done);
- done += len;
- buf += len;
- size -= len;
- } while (size > 0);
+ len = sizeof(rnd);
+ __sysctl(mib, 2, rnd, &len, NULL, 0);
- return (done);
-}
-
-static void
-arc4_stir(void)
-{
- int done, fd, i;
- struct {
- struct timeval tv;
- pid_t pid;
- u_char rnd[KEYSIZE];
- } rdat;
-
if (!rs_initialized) {
- arc4_init();
rs_initialized = 1;
- }
- done = 0;
- if (arc4_sysctl((u_char *)&rdat, KEYSIZE) == KEYSIZE)
- done = 1;
- if (!done) {
- fd = _open(RANDOMDEV, O_RDONLY | O_CLOEXEC, 0);
- if (fd >= 0) {
- if (_read(fd, &rdat, KEYSIZE) == KEYSIZE)
- done = 1;
- (void)_close(fd);
- }
- }
- if (!done) {
- (void)gettimeofday(&rdat.tv, NULL);
- rdat.pid = getpid();
- /* We'll just take whatever was on the stack too... */
- }
+ _rs_init(rnd, sizeof(rnd));
+ } else
+ _rs_rekey(rnd, sizeof(rnd));
+ bzero(rnd, sizeof(rnd)); /* explicit_bzero */
- arc4_addrandom((u_char *)&rdat, KEYSIZE);
+ /* invalidate rs_buf */
+ rs_have = 0;
+ memset(rs_buf, 0, RSBUFSZ);
- /*
- * Discard early keystream, as per recommendations in:
- * "(Not So) Random Shuffles of RC4" by Ilya Mironov.
- */
- for (i = 0; i < 1024; i++)
- (void)arc4_getbyte();
- arc4_count = 1600000;
+ rs_count = 1600000;
}
-static void
-arc4_stir_if_needed(void)
+static inline void
+_rs_stir_if_needed(size_t len)
{
pid_t pid = getpid();
- if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid)
- {
- arc4_stir_pid = pid;
- arc4_stir();
- }
+ if (rs_count <= len || !rs_initialized || rs_stir_pid != pid) {
+ rs_stir_pid = pid;
+ _rs_stir();
+ } else
+ rs_count -= len;
}
-static inline u_int8_t
-arc4_getbyte(void)
+static inline void
+_rs_rekey(u_char *dat, size_t datlen)
{
- u_int8_t si, sj;
+#ifndef KEYSTREAM_ONLY
+ memset(rs_buf, 0,RSBUFSZ);
+#endif
+ /* fill rs_buf with the keystream */
+ chacha_encrypt_bytes(rs, rs_buf, rs_buf, RSBUFSZ);
+ /* mix in optional user provided data */
+ if (dat) {
+ size_t i, m;
- rs.i = (rs.i + 1);
- si = rs.s[rs.i];
- rs.j = (rs.j + si);
- sj = rs.s[rs.j];
- rs.s[rs.i] = sj;
- rs.s[rs.j] = si;
- return (rs.s[(si + sj) & 0xff]);
+ m = MIN(datlen, KEYSZ + IVSZ);
+ for (i = 0; i < m; i++)
+ rs_buf[i] ^= dat[i];
+ }
+ /* immediately reinit for backtracking resistance */
+ _rs_init(rs_buf, KEYSZ + IVSZ);
+ memset(rs_buf, 0, KEYSZ + IVSZ);
+ rs_have = RSBUFSZ - KEYSZ - IVSZ;
}
-static inline u_int32_t
-arc4_getword(void)
+static inline void
+_rs_random_buf(void *_buf, size_t n)
{
- u_int32_t val;
- val = arc4_getbyte() << 24;
- val |= arc4_getbyte() << 16;
- val |= arc4_getbyte() << 8;
- val |= arc4_getbyte();
- return val;
-}
+ u_char *buf = (u_char *)_buf;
+ size_t m;
-void
-arc4random_stir(void)
-{
- _ARC4_LOCK();
- arc4_stir();
- _ARC4_UNLOCK();
+ _rs_stir_if_needed(n);
+ while (n > 0) {
+ if (rs_have > 0) {
+ m = MIN(n, rs_have);
+ memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
+ memset(rs_buf + RSBUFSZ - rs_have, 0, m);
+ buf += m;
+ n -= m;
+ rs_have -= m;
+ }
+ if (rs_have == 0)
+ _rs_rekey(NULL, 0);
+ }
}
-void
-arc4random_addrandom(u_char *dat, int datlen)
+static inline void
+_rs_random_u32(u_int32_t *val)
{
- _ARC4_LOCK();
- if (!rs_initialized)
- arc4_stir();
- arc4_addrandom(dat, datlen);
- _ARC4_UNLOCK();
+ _rs_stir_if_needed(sizeof(*val));
+ if (rs_have < sizeof(*val))
+ _rs_rekey(NULL, 0);
+ memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
+ memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
+ rs_have -= sizeof(*val);
+ return;
}
u_int32_t
arc4random(void)
{
u_int32_t val;
+
_ARC4_LOCK();
- arc4_count -= 4;
- arc4_stir_if_needed();
- val = arc4_getword();
+ _rs_random_u32(&val);
_ARC4_UNLOCK();
return val;
}
void
-arc4random_buf(void *_buf, size_t n)
+arc4random_buf(void *buf, size_t n)
{
- u_char *buf = (u_char *)_buf;
_ARC4_LOCK();
- arc4_stir_if_needed();
- while (n--) {
- if (--arc4_count <= 0)
- arc4_stir();
- buf[n] = arc4_getbyte();
- }
+ _rs_random_buf(buf, n);
_ARC4_UNLOCK();
}
@@ -276,17 +227,8 @@
if (upper_bound < 2)
return 0;
-#if (ULONG_MAX > 0xffffffffUL)
- min = 0x100000000UL % upper_bound;
-#else
- /* Calculate (2**32 % upper_bound) avoiding 64-bit math */
- if (upper_bound > 0x80000000)
- min = 1 + ~upper_bound; /* 2**32 - upper_bound */
- else {
- /* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
- min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
- }
-#endif
+ /* 2**32 % x == (2**32 - x) % x */
+ min = -upper_bound % upper_bound;
/*
* This could theoretically loop forever but each retry has
@@ -302,24 +244,3 @@
return r % upper_bound;
}
-
-#if 0
-/*-------- Test code for i386 --------*/
-#include <stdio.h>
-#include <machine/pctr.h>
-int
-main(int argc, char **argv)
-{
- const int iter = 1000000;
- int i;
- pctrval v;
-
- v = rdtsc();
- for (i = 0; i < iter; i++)
- arc4random();
- v = rdtsc() - v;
- v /= iter;
-
- printf("%qd cycles\n", v);
-}
-#endif
--- /dev/null Thu May 29 20:52:04 2014
+++ chacha_private.h Thu May 29 20:40:54 2014
@@ -0,0 +1,222 @@
+/*
+chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+*/
+
+/* $OpenBSD: chacha_private.h,v 1.2 2013/10/04 07:02:27 djm Exp $ */
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+
+typedef struct
+{
+ u32 input[16]; /* could be compressed */
+} chacha_ctx;
+
+#define U8C(v) (v##U)
+#define U32C(v) (v##U)
+
+#define U8V(v) ((u8)(v) & U8C(0xFF))
+#define U32V(v) ((u32)(v) & U32C(0xFFFFFFFF))
+
+#define ROTL32(v, n) \
+ (U32V((v) << (n)) | ((v) >> (32 - (n))))
+
+#define U8TO32_LITTLE(p) \
+ (((u32)((p)[0]) ) | \
+ ((u32)((p)[1]) << 8) | \
+ ((u32)((p)[2]) << 16) | \
+ ((u32)((p)[3]) << 24))
+
+#define U32TO8_LITTLE(p, v) \
+ do { \
+ (p)[0] = U8V((v) ); \
+ (p)[1] = U8V((v) >> 8); \
+ (p)[2] = U8V((v) >> 16); \
+ (p)[3] = U8V((v) >> 24); \
+ } while (0)
+
+#define ROTATE(v,c) (ROTL32(v,c))
+#define XOR(v,w) ((v) ^ (w))
+#define PLUS(v,w) (U32V((v) + (w)))
+#define PLUSONE(v) (PLUS((v),1))
+
+#define QUARTERROUND(a,b,c,d) \
+ a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
+ c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
+ a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
+ c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
+
+static const char sigma[16] = "expand 32-byte k";
+static const char tau[16] = "expand 16-byte k";
+
+static void
+chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
+{
+ const char *constants;
+
+ x->input[4] = U8TO32_LITTLE(k + 0);
+ x->input[5] = U8TO32_LITTLE(k + 4);
+ x->input[6] = U8TO32_LITTLE(k + 8);
+ x->input[7] = U8TO32_LITTLE(k + 12);
+ if (kbits == 256) { /* recommended */
+ k += 16;
+ constants = sigma;
+ } else { /* kbits == 128 */
+ constants = tau;
+ }
+ x->input[8] = U8TO32_LITTLE(k + 0);
+ x->input[9] = U8TO32_LITTLE(k + 4);
+ x->input[10] = U8TO32_LITTLE(k + 8);
+ x->input[11] = U8TO32_LITTLE(k + 12);
+ x->input[0] = U8TO32_LITTLE(constants + 0);
+ x->input[1] = U8TO32_LITTLE(constants + 4);
+ x->input[2] = U8TO32_LITTLE(constants + 8);
+ x->input[3] = U8TO32_LITTLE(constants + 12);
+}
+
+static void
+chacha_ivsetup(chacha_ctx *x,const u8 *iv)
+{
+ x->input[12] = 0;
+ x->input[13] = 0;
+ x->input[14] = U8TO32_LITTLE(iv + 0);
+ x->input[15] = U8TO32_LITTLE(iv + 4);
+}
+
+static void
+chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
+{
+ u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+ u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
+ u8 *ctarget = NULL;
+ u8 tmp[64];
+ u_int i;
+
+ if (!bytes) return;
+
+ j0 = x->input[0];
+ j1 = x->input[1];
+ j2 = x->input[2];
+ j3 = x->input[3];
+ j4 = x->input[4];
+ j5 = x->input[5];
+ j6 = x->input[6];
+ j7 = x->input[7];
+ j8 = x->input[8];
+ j9 = x->input[9];
+ j10 = x->input[10];
+ j11 = x->input[11];
+ j12 = x->input[12];
+ j13 = x->input[13];
+ j14 = x->input[14];
+ j15 = x->input[15];
+
+ for (;;) {
+ if (bytes < 64) {
+ for (i = 0;i < bytes;++i) tmp[i] = m[i];
+ m = tmp;
+ ctarget = c;
+ c = tmp;
+ }
+ x0 = j0;
+ x1 = j1;
+ x2 = j2;
+ x3 = j3;
+ x4 = j4;
+ x5 = j5;
+ x6 = j6;
+ x7 = j7;
+ x8 = j8;
+ x9 = j9;
+ x10 = j10;
+ x11 = j11;
+ x12 = j12;
+ x13 = j13;
+ x14 = j14;
+ x15 = j15;
+ for (i = 20;i > 0;i -= 2) {
+ QUARTERROUND( x0, x4, x8,x12)
+ QUARTERROUND( x1, x5, x9,x13)
+ QUARTERROUND( x2, x6,x10,x14)
+ QUARTERROUND( x3, x7,x11,x15)
+ QUARTERROUND( x0, x5,x10,x15)
+ QUARTERROUND( x1, x6,x11,x12)
+ QUARTERROUND( x2, x7, x8,x13)
+ QUARTERROUND( x3, x4, x9,x14)
+ }
+ x0 = PLUS(x0,j0);
+ x1 = PLUS(x1,j1);
+ x2 = PLUS(x2,j2);
+ x3 = PLUS(x3,j3);
+ x4 = PLUS(x4,j4);
+ x5 = PLUS(x5,j5);
+ x6 = PLUS(x6,j6);
+ x7 = PLUS(x7,j7);
+ x8 = PLUS(x8,j8);
+ x9 = PLUS(x9,j9);
+ x10 = PLUS(x10,j10);
+ x11 = PLUS(x11,j11);
+ x12 = PLUS(x12,j12);
+ x13 = PLUS(x13,j13);
+ x14 = PLUS(x14,j14);
+ x15 = PLUS(x15,j15);
+
+#ifndef KEYSTREAM_ONLY
+ x0 = XOR(x0,U8TO32_LITTLE(m + 0));
+ x1 = XOR(x1,U8TO32_LITTLE(m + 4));
+ x2 = XOR(x2,U8TO32_LITTLE(m + 8));
+ x3 = XOR(x3,U8TO32_LITTLE(m + 12));
+ x4 = XOR(x4,U8TO32_LITTLE(m + 16));
+ x5 = XOR(x5,U8TO32_LITTLE(m + 20));
+ x6 = XOR(x6,U8TO32_LITTLE(m + 24));
+ x7 = XOR(x7,U8TO32_LITTLE(m + 28));
+ x8 = XOR(x8,U8TO32_LITTLE(m + 32));
+ x9 = XOR(x9,U8TO32_LITTLE(m + 36));
+ x10 = XOR(x10,U8TO32_LITTLE(m + 40));
+ x11 = XOR(x11,U8TO32_LITTLE(m + 44));
+ x12 = XOR(x12,U8TO32_LITTLE(m + 48));
+ x13 = XOR(x13,U8TO32_LITTLE(m + 52));
+ x14 = XOR(x14,U8TO32_LITTLE(m + 56));
+ x15 = XOR(x15,U8TO32_LITTLE(m + 60));
+#endif
+
+ j12 = PLUSONE(j12);
+ if (!j12) {
+ j13 = PLUSONE(j13);
+ /* stopping at 2^70 bytes per nonce is user's responsibility */
+ }
+
+ U32TO8_LITTLE(c + 0,x0);
+ U32TO8_LITTLE(c + 4,x1);
+ U32TO8_LITTLE(c + 8,x2);
+ U32TO8_LITTLE(c + 12,x3);
+ U32TO8_LITTLE(c + 16,x4);
+ U32TO8_LITTLE(c + 20,x5);
+ U32TO8_LITTLE(c + 24,x6);
+ U32TO8_LITTLE(c + 28,x7);
+ U32TO8_LITTLE(c + 32,x8);
+ U32TO8_LITTLE(c + 36,x9);
+ U32TO8_LITTLE(c + 40,x10);
+ U32TO8_LITTLE(c + 44,x11);
+ U32TO8_LITTLE(c + 48,x12);
+ U32TO8_LITTLE(c + 52,x13);
+ U32TO8_LITTLE(c + 56,x14);
+ U32TO8_LITTLE(c + 60,x15);
+
+ if (bytes <= 64) {
+ if (bytes < 64) {
+ for (i = 0;i < bytes;++i) ctarget[i] = c[i];
+ }
+ x->input[12] = j12;
+ x->input[13] = j13;
+ return;
+ }
+ bytes -= 64;
+ c += 64;
+#ifndef KEYSTREAM_ONLY
+ m += 64;
+#endif
+ }
+}
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