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am 7b87d441: Merge "Switch to OpenBSD res_random."

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* commit '7b87d441b0f2aa3ad5021ab6bd879a995a1bc2ce':
  Switch to OpenBSD res_random.
This commit is contained in:
Elliott Hughes 2014-08-26 23:41:23 +00:00 committed by Android Git Automerger
commit f975bc2d59
3 changed files with 282 additions and 42 deletions
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8
libc/Android.mk
View file

@ -643,7 +643,13 @@ LOCAL_SRC_FILES := \
upstream-netbsd/lib/libc/isc/ev_timers.c \
upstream-netbsd/lib/libc/resolv/mtctxres.c \
LOCAL_CFLAGS := \
# We use the OpenBSD res_random.
LOCAL_CFLAGS += \
-Dres_randomid=__res_randomid
LOCAL_SRC_FILES += \
upstream-openbsd/lib/libc/net/res_random.c \
LOCAL_CFLAGS += \
$(libc_common_cflags) \
-DANDROID_CHANGES \
-DINET6 \

41
libc/dns/resolv/res_init.c
View file

@ -616,47 +616,6 @@ net_mask(struct in_addr in) /*!< XXX - should really use system's version of thi
}
#endif
#ifdef ANDROID_CHANGES
static int
real_randomid(u_int *random_value) {
/* open the nonblocking random device, returning -1 on failure */
int random_device = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
if (random_device < 0) {
return -1;
}
/* read from the random device, returning -1 on failure (or too many retries)*/
for (u_int retry = 5; retry > 0; retry--) {
int retval = read(random_device, random_value, sizeof(u_int));
if (retval == sizeof(u_int)) {
*random_value &= 0xffff;
close(random_device);
return 0;
} else if ((retval < 0) && (errno != EINTR)) {
break;
}
}
close(random_device);
return -1;
}
#endif /* ANDROID_CHANGES */
u_int
res_randomid(void) {
#ifdef ANDROID_CHANGES
int status = 0;
u_int output = 0;
status = real_randomid(&output);
if (status != -1) {
return output;
}
#endif /* ANDROID_CHANGES */
struct timeval now;
gettimeofday(&now, NULL);
return (0xffff & (now.tv_sec ^ now.tv_usec ^ getpid()));
}
/*%
* This routine is for closing the socket if a virtual circuit is used and
* the program wants to close it. This provides support for endhostent()

275
libc/upstream-openbsd/lib/libc/net/res_random.c Normal file
View file

@ -0,0 +1,275 @@
/* $OpenBSD: res_random.c,v 1.21 2014/07/20 04:22:34 guenther Exp $ */
/*
* Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
* Copyright 2008 Damien Miller <djm@openbsd.org>
* All rights reserved.
*
* Theo de Raadt <deraadt@openbsd.org> came up with the idea of using
* such a mathematical system to generate more random (yet non-repeating)
* ids to solve the resolver/named problem. But Niels designed the
* actual system based on the constraints.
*
* Later modified by Damien Miller to wrap the LCG output in a 15-bit
* permutation generator based on a Luby-Rackoff block cipher. This
* ensures the output is non-repeating and preserves the MSB twiddle
* trick, but makes it more resistant to LCG prediction.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* seed = random 15bit
* n = prime, g0 = generator to n,
* j = random so that gcd(j,n-1) == 1
* g = g0^j mod n will be a generator again.
*
* X[0] = random seed.
* X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator
* with a = 7^(even random) mod m,
* b = random with gcd(b,m) == 1
* m = 31104 and a maximal period of m-1.
*
* The transaction id is determined by:
* id[n] = seed xor (g^X[n] mod n)
*
* Effectivly the id is restricted to the lower 15 bits, thus
* yielding two different cycles by toggling the msb on and off.
* This avoids reuse issues caused by reseeding.
*
* The output of this generator is then randomly permuted though a
* custom 15 bit Luby-Rackoff block cipher.
*/
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/time.h>
#include <resolv.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include "thread_private.h"
#define RU_OUT 180 /* Time after wich will be reseeded */
#define RU_MAX 30000 /* Uniq cycle, avoid blackjack prediction */
#define RU_GEN 2 /* Starting generator */
#define RU_N 32749 /* RU_N-1 = 2*2*3*2729 */
#define RU_AGEN 7 /* determine ru_a as RU_AGEN^(2*rand) */
#define RU_M 31104 /* RU_M = 2^7*3^5 - don't change */
#define RU_ROUNDS 11 /* Number of rounds for permute (odd) */
struct prf_ctx {
/* PRF lookup table for odd rounds (7 bits input to 8 bits output) */
u_char prf7[(RU_ROUNDS / 2) * (1 << 7)];
/* PRF lookup table for even rounds (8 bits input to 7 bits output) */
u_char prf8[((RU_ROUNDS + 1) / 2) * (1 << 8)];
};
#define PFAC_N 3
static const u_int16_t pfacts[PFAC_N] = {
2,
3,
2729
};
static u_int16_t ru_x;
static u_int16_t ru_seed, ru_seed2;
static u_int16_t ru_a, ru_b;
static u_int16_t ru_g;
static u_int16_t ru_counter = 0;
static u_int16_t ru_msb = 0;
static struct prf_ctx *ru_prf = NULL;
static time_t ru_reseed;
static u_int16_t pmod(u_int16_t, u_int16_t, u_int16_t);
static void res_initid(void);
/*
* Do a fast modular exponation, returned value will be in the range
* of 0 - (mod-1)
*/
static u_int16_t
pmod(u_int16_t gen, u_int16_t exp, u_int16_t mod)
{
u_int16_t s, t, u;
s = 1;
t = gen;
u = exp;
while (u) {
if (u & 1)
s = (s * t) % mod;
u >>= 1;
t = (t * t) % mod;
}
return (s);
}
/*
* 15-bit permutation based on Luby-Rackoff block cipher
*/
static u_int
permute15(u_int in)
{
int i;
u_int left, right, tmp;
if (ru_prf == NULL)
return in;
left = (in >> 8) & 0x7f;
right = in & 0xff;
/*
* Each round swaps the width of left and right. Even rounds have
* a 7-bit left, odd rounds have an 8-bit left. Since this uses an
* odd number of rounds, left is always 8 bits wide at the end.
*/
for (i = 0; i < RU_ROUNDS; i++) {
if ((i & 1) == 0)
tmp = ru_prf->prf8[(i << (8 - 1)) | right] & 0x7f;
else
tmp = ru_prf->prf7[((i - 1) << (7 - 1)) | right];
tmp ^= left;
left = right;
right = tmp;
}
return (right << 8) | left;
}
/*
* Initializes the seed and chooses a suitable generator. Also toggles
* the msb flag. The msb flag is used to generate two distinct
* cycles of random numbers and thus avoiding reuse of ids.
*
* This function is called from res_randomid() when needed, an
* application does not have to worry about it.
*/
static void
res_initid(void)
{
u_int16_t j, i;
u_int32_t tmp;
int noprime = 1;
struct timespec ts;
ru_x = arc4random_uniform(RU_M);
/* 15 bits of random seed */
tmp = arc4random();
ru_seed = (tmp >> 16) & 0x7FFF;
ru_seed2 = tmp & 0x7FFF;
/* Determine the LCG we use */
tmp = arc4random();
ru_b = (tmp & 0xfffe) | 1;
ru_a = pmod(RU_AGEN, (tmp >> 16) & 0xfffe, RU_M);
while (ru_b % 3 == 0)
ru_b += 2;
j = arc4random_uniform(RU_N);
/*
* Do a fast gcd(j,RU_N-1), so we can find a j with
* gcd(j, RU_N-1) == 1, giving a new generator for
* RU_GEN^j mod RU_N
*/
while (noprime) {
for (i = 0; i < PFAC_N; i++)
if (j % pfacts[i] == 0)
break;
if (i >= PFAC_N)
noprime = 0;
else
j = (j + 1) % RU_N;
}
ru_g = pmod(RU_GEN, j, RU_N);
ru_counter = 0;
/* Initialise PRF for Luby-Rackoff permutation */
if (ru_prf == NULL)
ru_prf = malloc(sizeof(*ru_prf));
if (ru_prf != NULL)
arc4random_buf(ru_prf, sizeof(*ru_prf));
clock_gettime(CLOCK_MONOTONIC, &ts);
ru_reseed = ts.tv_sec + RU_OUT;
ru_msb = ru_msb == 0x8000 ? 0 : 0x8000;
}
u_int
res_randomid(void)
{
struct timespec ts;
u_int r;
_THREAD_PRIVATE_MUTEX(random);
clock_gettime(CLOCK_MONOTONIC, &ts);
_THREAD_PRIVATE_MUTEX_LOCK(random);
if (ru_counter >= RU_MAX || ts.tv_sec > ru_reseed)
res_initid();
/* Linear Congruential Generator */
ru_x = (ru_a * ru_x + ru_b) % RU_M;
ru_counter++;
r = permute15(ru_seed ^ pmod(ru_g, ru_seed2 + ru_x, RU_N)) | ru_msb;
_THREAD_PRIVATE_MUTEX_UNLOCK(random);
return (r);
}
#if 0
int
main(int argc, char **argv)
{
int i, n;
u_int16_t wert;
res_initid();
printf("Generator: %u\n", ru_g);
printf("Seed: %u\n", ru_seed);
printf("Reseed at %ld\n", ru_reseed);
printf("Ru_X: %u\n", ru_x);
printf("Ru_A: %u\n", ru_a);
printf("Ru_B: %u\n", ru_b);
n = argc > 1 ? atoi(argv[1]) : 60001;
for (i=0;i<n;i++) {
wert = res_randomid();
printf("%u\n", wert);
}
return 0;
}
#endif