mirror of
https://github.com/cuberite/libevent.git
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Add an arc4random implementation for use by evdns
Previously, evdns was at the mercy of the user for providing a good entropy source; without one, it would be vulnerable to various active attacks. This patch adds a port of OpenBSD's arc4random() calls to Libevent [port by Chris Davis], and wraps it up a little bit so we can use it more safely.
This commit is contained in:
Nick Mathewson
parent
1dd7e6dc3a
commit
d4de062efc
@ -44,7 +44,7 @@ EXTRA_DIST = \
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Doxyfile \
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kqueue.c epoll_sub.c epoll.c select.c poll.c signal.c \
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evport.c devpoll.c win32select.c event_rpcgen.py \
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event_iocp.c buffer_iocp.c iocp-internal.h \
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event_iocp.c buffer_iocp.c iocp-internal.h arc4random.c \
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sample/Makefile.am sample/Makefile.in sample/event-test.c \
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sample/signal-test.c sample/time-test.c \
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test/Makefile.am test/Makefile.in test/bench.c test/regress.c \
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@ -107,7 +107,7 @@ event-config.h: config.h
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CORE_SRC = event.c evthread.c buffer.c \
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bufferevent.c bufferevent_sock.c bufferevent_filter.c \
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bufferevent_pair.c listener.c bufferevent_ratelim.c \
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evmap.c log.c evutil.c strlcpy.c $(SYS_SRC)
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evmap.c log.c evutil.c evutil_rand.c strlcpy.c $(SYS_SRC)
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EXTRA_SRC = event_tagging.c http.c evdns.c evrpc.c
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358
arc4random.c
Normal file
358
arc4random.c
Normal file
@ -0,0 +1,358 @@
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/* Portable arc4random.c based on arc4random.c from OpenBSD.
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* Portable version by Chris Davis, adapted for Libevent by Nick Mathewson
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*
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* Note that in Libevent, this file isn't compiled directly. Instead,
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* it's included from evutil_rand.c
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*/
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/*
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* Copyright (c) 1996, David Mazieres <dm@uun.org>
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* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Arc4 random number generator for OpenBSD.
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*
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* This code is derived from section 17.1 of Applied Cryptography,
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* second edition, which describes a stream cipher allegedly
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* compatible with RSA Labs "RC4" cipher (the actual description of
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* which is a trade secret). The same algorithm is used as a stream
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* cipher called "arcfour" in Tatu Ylonen's ssh package.
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*
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* Here the stream cipher has been modified always to include the time
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* when initializing the state. That makes it impossible to
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* regenerate the same random sequence twice, so this can't be used
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* for encryption, but will generate good random numbers.
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*
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* RC4 is a registered trademark of RSA Laboratories.
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*/
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#ifndef ARC4RANDOM_EXPORT
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#define ARC4RANDOM_EXPORT
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#endif
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#ifndef ARC4RANDOM_NO_INCLUDES
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#ifdef WIN32
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#include <wincrypt.h>
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#else
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/param.h>
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#include <sys/time.h>
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#endif
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#endif
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/* Add platform entropy 32 bytes (256 bits) at a time. */
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#define ADD_ENTROPY 32
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/* Re-seed from the platform RNG after generating this many bytes. */
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#define BYTES_BEFORE_RESEED 1600000
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struct arc4_stream {
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unsigned char i;
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unsigned char j;
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unsigned char s[256];
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};
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static int rs_initialized;
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static struct arc4_stream rs;
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static pid_t arc4_stir_pid;
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static int arc4_count;
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static int arc4_seeded_ok;
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static inline unsigned char arc4_getbyte(void);
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static inline void
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arc4_init(void)
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{
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int n;
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for (n = 0; n < 256; n++)
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rs.s[n] = n;
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rs.i = 0;
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rs.j = 0;
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}
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static inline void
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arc4_addrandom(const unsigned char *dat, int datlen)
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{
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int n;
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unsigned char si;
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rs.i--;
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for (n = 0; n < 256; n++) {
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rs.i = (rs.i + 1);
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si = rs.s[rs.i];
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rs.j = (rs.j + si + dat[n % datlen]);
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rs.s[rs.i] = rs.s[rs.j];
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rs.s[rs.j] = si;
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}
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rs.j = rs.i;
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}
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#ifndef WIN32
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static ssize_t
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read_all(int fd, unsigned char *buf, size_t count)
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{
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size_t numread = 0;
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ssize_t result;
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while (numread < count) {
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result = read(fd, buf+numread, count-numread);
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if (result<0)
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return -1;
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else if (result == 0)
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break;
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numread += result;
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}
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return (ssize_t)numread;
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}
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#endif
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/* This is adapted from Tor's crypto_seed_rng() */
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static int
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arc4_seed(void)
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{
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unsigned char buf[ADD_ENTROPY];
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/* local variables */
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#ifdef WIN32
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static int provider_set = 0;
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static HCRYPTPROV provider;
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#else
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static const char *filenames[] = {
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"/dev/srandom", "/dev/urandom", "/dev/random", NULL
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};
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int fd, i;
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size_t n;
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#endif
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#ifdef WIN32
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if (!provider_set) {
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if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
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CRYPT_VERIFYCONTEXT)) {
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if ((unsigned long)GetLastError() != (unsigned long)NTE_BAD_KEYSET)
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return -1;
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}
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provider_set = 1;
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}
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if (!CryptGenRandom(provider, sizeof(buf), buf))
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return -1;
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arc4_addrandom(buf, sizeof(buf));
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memset(buf, 0, sizeof(buf));
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arc4_seeded_ok = 1;
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return 0;
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#else
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for (i = 0; filenames[i]; ++i) {
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fd = open(filenames[i], O_RDONLY, 0);
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if (fd<0)
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continue;
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n = read_all(fd, buf, sizeof(buf));
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close(fd);
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if (n != sizeof(buf))
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return -1;
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arc4_addrandom(buf, sizeof(buf));
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memset(buf, 0, sizeof(buf));
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arc4_seeded_ok = 1;
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return 0;
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}
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return -1;
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#endif
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}
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static void
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arc4_stir(void)
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{
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int i;
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if (!rs_initialized) {
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arc4_init();
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rs_initialized = 1;
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}
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arc4_seed();
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/*
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* Discard early keystream, as per recommendations in
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* "Weaknesses in the Key Scheduling Algorithm of RC4" by
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* Scott Fluhrer, Itsik Mantin, and Adi Shamir.
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* http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
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*
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* Ilya Mironov's "(Not So) Random Shuffles of RC4" suggests that
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* we drop at least 2*256 bytes, with 12*256 as a conservative
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* value.
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*
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* RFC4345 says to drop 6*256.
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*
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* At least some versions of this code drop 4*256, in a mistaken
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* belief that "words" in the Fluhrer/Mantin/Shamir paper refers
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* to processor words.
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*
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* We add another sect to the cargo cult, and choose 12*256.
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*/
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for (i = 0; i < 12*256; i++)
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(void)arc4_getbyte();
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arc4_count = BYTES_BEFORE_RESEED;
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}
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static void
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arc4_stir_if_needed(void)
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{
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pid_t pid = getpid();
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if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid)
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{
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arc4_stir_pid = pid;
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arc4_stir();
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}
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}
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static inline unsigned char
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arc4_getbyte(void)
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{
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unsigned char si, sj;
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rs.i = (rs.i + 1);
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si = rs.s[rs.i];
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rs.j = (rs.j + si);
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sj = rs.s[rs.j];
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rs.s[rs.i] = sj;
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rs.s[rs.j] = si;
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return (rs.s[(si + sj) & 0xff]);
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}
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static inline unsigned int
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arc4_getword(void)
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{
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unsigned int val;
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val = arc4_getbyte() << 24;
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val |= arc4_getbyte() << 16;
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val |= arc4_getbyte() << 8;
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val |= arc4_getbyte();
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return val;
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}
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#ifndef ARC4RANDOM_NOSTIR
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ARC4RANDOM_EXPORT int
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arc4random_stir(void)
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{
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int val;
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_ARC4_LOCK();
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val = arc4_stir();
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_ARC4_UNLOCK();
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return val;
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}
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#endif
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#ifndef ARC4RANDOM_NOADDRANDOM
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ARC4RANDOM_EXPORT void
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arc4random_addrandom(const unsigned char *dat, int datlen)
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{
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int j;
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_ARC4_LOCK();
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if (!rs_initialized)
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arc4_stir();
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for (j = 0; j < datlen; j += 256) {
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/* arc4_addrandom() ignores all but the first 256 bytes of
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* its input. We want to make sure to look at ALL the
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* data in 'dat', just in case the user is doing something
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* crazy like passing us all the files in /var/log. */
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arc4_addrandom(dat + j, datlen - j);
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}
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_ARC4_UNLOCK();
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}
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#endif
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#ifndef ARC4RANDOM_NORANDOM
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ARC4RANDOM_EXPORT unsigned int
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arc4random(void)
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{
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unsigned int val;
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_ARC4_LOCK();
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arc4_count -= 4;
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arc4_stir_if_needed();
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val = arc4_getword();
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_ARC4_UNLOCK();
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return val;
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}
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#endif
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ARC4RANDOM_EXPORT void
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arc4random_buf(void *_buf, size_t n)
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{
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unsigned char *buf = _buf;
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_ARC4_LOCK();
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arc4_stir_if_needed();
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while (n--) {
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if (--arc4_count <= 0)
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arc4_stir();
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buf[n] = arc4_getbyte();
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}
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_ARC4_UNLOCK();
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}
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#ifndef ARC4RANDOM_NOUNIFORM
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/*
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* Calculate a uniformly distributed random number less than upper_bound
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* avoiding "modulo bias".
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*
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* Uniformity is achieved by generating new random numbers until the one
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* returned is outside the range [0, 2**32 % upper_bound). This
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* guarantees the selected random number will be inside
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* [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
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* after reduction modulo upper_bound.
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*/
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ARC4RANDOM_EXPORT unsigned int
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arc4random_uniform(unsigned int upper_bound)
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{
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unsigned int r, min;
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if (upper_bound < 2)
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return 0;
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#if (UINT_MAX > 0xffffffffUL)
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min = 0x100000000UL % upper_bound;
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#else
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/* Calculate (2**32 % upper_bound) avoiding 64-bit math */
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if (upper_bound > 0x80000000)
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min = 1 + ~upper_bound; /* 2**32 - upper_bound */
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else {
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/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
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min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
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}
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#endif
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/*
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* This could theoretically loop forever but each retry has
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* p > 0.5 (worst case, usually far better) of selecting a
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* number inside the range we need, so it should rarely need
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* to re-roll.
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*/
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for (;;) {
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r = arc4random();
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if (r >= min)
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break;
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}
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return r % upper_bound;
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}
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#endif
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@ -244,14 +244,6 @@ AC_CHECK_FUNC(gethostbyname_r, [
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AC_CHECK_SIZEOF(long)
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if test "x$ac_cv_func_arc4random" = "xyes" ; then
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AC_DEFINE(DNS_USE_ARC4RANDOM_FOR_ID, 1, [Define if we should use arc4random to generate dns transation IDs])
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elif test "x$ac_cv_func_clock_gettime" = "xyes"; then
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AC_DEFINE(DNS_USE_CPU_CLOCK_FOR_ID, 1, [Define if we should use clock_gettime to generate dns transation IDs])
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else
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AC_DEFINE(DNS_USE_GETTIMEOFDAY_FOR_ID, 1, [Define if s no secure id variant is available])
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fi
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AC_MSG_CHECKING(for F_SETFD in fcntl.h)
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AC_EGREP_CPP(yes,
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[
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132
evdns.c
132
evdns.c
@ -37,45 +37,6 @@
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#include <sys/types.h>
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#include "event-config.h"
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#ifdef _EVENT_DNS_USE_FTIME_FOR_ID
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#include <sys/timeb.h>
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#endif
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#ifndef _EVENT_DNS_USE_CPU_CLOCK_FOR_ID
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#ifndef _EVENT_DNS_USE_GETTIMEOFDAY_FOR_ID
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#ifndef _EVENT_DNS_USE_OPENSSL_FOR_ID
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#ifndef _EVENT_DNS_USE_FTIME_FOR_ID
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#ifndef _EVENT_DNS_USE_ARC4RANDOM_FOR_ID
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#error Must configure at least one id generation method.
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#error Please see the documentation.
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#endif
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#endif
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#endif
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#endif
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#endif
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/* #define _POSIX_C_SOURCE 200507 */
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#define _GNU_SOURCE
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/* for strtok_r */
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#define _REENTRANT
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#ifdef _EVENT_DNS_USE_CPU_CLOCK_FOR_ID
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#ifdef _EVENT_DNS_USE_OPENSSL_FOR_ID
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#error Multiple id options selected
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#endif
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#ifdef _EVENT_DNS_USE_GETTIMEOFDAY_FOR_ID
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#error Multiple id options selected
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#endif
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#include <time.h>
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#endif
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#ifdef _EVENT_DNS_USE_OPENSSL_FOR_ID
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#ifdef _EVENT_DNS_USE_GETTIMEOFDAY_FOR_ID
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#error Multiple id options selected
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#endif
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#include <openssl/rand.h>
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#endif
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#ifndef _FORTIFY_SOURCE
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#define _FORTIFY_SOURCE 3
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#endif
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@ -1213,97 +1174,15 @@ err:
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#undef GET8
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}
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static u16
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default_transaction_id_fn(void)
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{
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u16 trans_id;
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#ifdef _EVENT_DNS_USE_CPU_CLOCK_FOR_ID
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struct timespec ts;
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static int clkid = -1;
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if (clkid == -1) {
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clkid = CLOCK_REALTIME;
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#ifdef CLOCK_MONOTONIC
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if (clock_gettime(CLOCK_MONOTONIC, &ts) != -1)
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clkid = CLOCK_MONOTONIC;
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#endif
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}
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if (clock_gettime(clkid, &ts) == -1)
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event_err(1, "clock_gettime");
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trans_id = ts.tv_nsec & 0xffff;
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#endif
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#ifdef _EVENT_DNS_USE_FTIME_FOR_ID
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struct _timeb tb;
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_ftime(&tb);
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trans_id = tb.millitm & 0xffff;
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#endif
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#ifdef _EVENT_DNS_USE_GETTIMEOFDAY_FOR_ID
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struct timeval tv;
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evutil_gettimeofday(&tv, NULL);
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trans_id = tv.tv_usec & 0xffff;
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#endif
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#ifdef _EVENT_DNS_USE_OPENSSL_FOR_ID
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if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) {
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/* in the case that the RAND call fails we used to back */
|
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/* down to using gettimeofday. */
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/*
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struct timeval tv;
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gettimeofday(&tv, NULL);
|
||||
trans_id = tv.tv_usec & 0xffff;
|
||||
*/
|
||||
event_errx("RAND_pseudo_bytes failed!");
|
||||
}
|
||||
#endif
|
||||
|
||||
#ifdef _EVENT_DNS_USE_ARC4RANDOM_FOR_ID
|
||||
trans_id = arc4random() & 0xffff;
|
||||
#endif
|
||||
|
||||
return trans_id;
|
||||
}
|
||||
|
||||
static ev_uint16_t (*trans_id_function)(void) = default_transaction_id_fn;
|
||||
|
||||
static void
|
||||
default_random_bytes_fn(char *buf, size_t n)
|
||||
{
|
||||
unsigned i;
|
||||
for (i = 0; i < n; i += 2) {
|
||||
u16 tid = trans_id_function();
|
||||
buf[i] = (tid >> 8) & 0xff;
|
||||
if (i+1<n)
|
||||
buf[i+1] = tid & 0xff;
|
||||
}
|
||||
}
|
||||
|
||||
static void (*rand_bytes_function)(char *buf, size_t n) =
|
||||
default_random_bytes_fn;
|
||||
|
||||
static u16
|
||||
trans_id_from_random_bytes_fn(void)
|
||||
{
|
||||
u16 tid;
|
||||
rand_bytes_function((char*) &tid, sizeof(tid));
|
||||
return tid;
|
||||
}
|
||||
|
||||
void
|
||||
evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
|
||||
{
|
||||
if (fn)
|
||||
trans_id_function = fn;
|
||||
else
|
||||
trans_id_function = default_transaction_id_fn;
|
||||
rand_bytes_function = default_random_bytes_fn;
|
||||
}
|
||||
|
||||
void
|
||||
evdns_set_random_bytes_fn(void (*fn)(char *, size_t))
|
||||
{
|
||||
rand_bytes_function = fn;
|
||||
trans_id_function = trans_id_from_random_bytes_fn;
|
||||
}
|
||||
|
||||
/* Try to choose a strong transaction id which isn't already in flight */
|
||||
@ -1311,7 +1190,8 @@ static u16
|
||||
transaction_id_pick(struct evdns_base *base) {
|
||||
ASSERT_LOCKED(base);
|
||||
for (;;) {
|
||||
u16 trans_id = trans_id_function();
|
||||
u16 trans_id;
|
||||
evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id));
|
||||
|
||||
if (trans_id == 0xffff) continue;
|
||||
/* now check to see if that id is already inflight */
|
||||
@ -2675,7 +2555,7 @@ request_new(struct evdns_base *base, int type, const char *name, int flags,
|
||||
unsigned i;
|
||||
char randbits[(sizeof(namebuf)+7)/8];
|
||||
strlcpy(namebuf, name, sizeof(namebuf));
|
||||
rand_bytes_function(randbits, (name_len+7)/8);
|
||||
evutil_secure_rng_get_bytes(randbits, (name_len+7)/8);
|
||||
for (i = 0; i < name_len; ++i) {
|
||||
if (EVUTIL_ISALPHA(namebuf[i])) {
|
||||
if ((randbits[i >> 3] & (1<<(i & 7))))
|
||||
@ -3720,6 +3600,12 @@ evdns_base_new(struct event_base *event_base, int initialize_nameservers)
|
||||
{
|
||||
struct evdns_base *base;
|
||||
|
||||
if (evutil_secure_rng_init() < 0) {
|
||||
log(EVDNS_LOG_WARN, "Unable to seed random number generator; "
|
||||
"DNS can't run.");
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/* Give the evutil library a hook into its evdns-enabled
|
||||
* functionality. We can't just call evdns_getaddrinfo directly or
|
||||
* else libevent-core will depend on libevent-extras. */
|
||||
|
||||
4
evutil.c
4
evutil.c
@ -1859,9 +1859,9 @@ long
|
||||
_evutil_weakrand(void)
|
||||
{
|
||||
#ifdef WIN32
|
||||
return rand();
|
||||
return rand();
|
||||
#else
|
||||
return random();
|
||||
return random();
|
||||
#endif
|
||||
}
|
||||
|
||||
|
||||
92
evutil_rand.c
Normal file
92
evutil_rand.c
Normal file
@ -0,0 +1,92 @@
|
||||
/*
|
||||
* Copyright (c) 2007-2010 Niels Provos and Nick Mathewson
|
||||
*
|
||||
* 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.
|
||||
* 3. The name of the author may not be used to endorse or promote products
|
||||
* derived from this software without specific prior written permission.
|
||||
*
|
||||
* 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.
|
||||
*/
|
||||
|
||||
/* This file has our secure PRNG code. On platforms that have arc4random(),
|
||||
* we just use that. Otherwise, we include arc4random.c as a bunch of static
|
||||
* functions, and wrap it lightly. We don't expose the arc4random*() APIs
|
||||
* because A) they aren't in our namespace, and B) it's not nice to name your
|
||||
* APIs after their implementations. We keep them in a separate file
|
||||
* so that other people can rip it out and use it for whatever.
|
||||
*/
|
||||
|
||||
#include "event-config.h"
|
||||
|
||||
#include "util-internal.h"
|
||||
#include "evthread-internal.h"
|
||||
|
||||
#ifdef _EVENT_HAVE_ARC4RANDOM
|
||||
#include <stdlib.h>
|
||||
int
|
||||
evutil_secure_rng_init(void)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
#else /* !_EVENT_HAVE_ARC4RANDOM { */
|
||||
|
||||
#ifdef _EVENT_ssize_t
|
||||
#define ssize_t _EVENT_SSIZE_t
|
||||
#endif
|
||||
#define ARC4RANDOM_EXPORT static
|
||||
#define _ARC4_LOCK() EVLOCK_LOCK(arc4rand_lock, 0)
|
||||
#define _ARC4_UNLOCK() EVLOCK_UNLOCK(arc4rand_lock, 0)
|
||||
static void *arc4rand_lock;
|
||||
|
||||
#define ARC4RANDOM_NOSTIR
|
||||
#define ARC4RANDOM_NORANDOM
|
||||
#define ARC4RANDOM_NOUNIFORM
|
||||
|
||||
#include "./arc4random.c"
|
||||
|
||||
int
|
||||
evutil_secure_rng_init(void)
|
||||
{
|
||||
int val;
|
||||
if (!arc4rand_lock) {
|
||||
EVTHREAD_ALLOC_LOCK(arc4rand_lock, 0);
|
||||
}
|
||||
|
||||
_ARC4_LOCK();
|
||||
if (!arc4_seeded_ok)
|
||||
arc4_stir();
|
||||
val = arc4_seeded_ok ? 0 : -1;
|
||||
_ARC4_UNLOCK();
|
||||
return val;
|
||||
}
|
||||
|
||||
#endif /* } !_EVENT_HAVE_ARC4RANDOM */
|
||||
|
||||
void
|
||||
evutil_secure_rng_get_bytes(void *buf, size_t n)
|
||||
{
|
||||
arc4random_buf(buf, n);
|
||||
}
|
||||
|
||||
void
|
||||
evutil_secure_rng_add_bytes(const char *buf, size_t n)
|
||||
{
|
||||
arc4random_addrandom((const unsigned char*)buf, n);
|
||||
}
|
||||
|
||||
@ -58,31 +58,6 @@
|
||||
* (see http://www.imperialviolet.org/page25.html#e498). Otherwise,
|
||||
* please continue.
|
||||
*
|
||||
* This code is based on Libevent and you must call event_init before
|
||||
* any of the APIs in this file. You must also seed the OpenSSL random
|
||||
* source if you are using OpenSSL for ids (see below).
|
||||
*
|
||||
* This library is designed to be included and shipped with your source
|
||||
* code. You statically link with it. You should also test for the
|
||||
* existence of strtok_r and define HAVE_STRTOK_R if you have it.
|
||||
*
|
||||
* The DNS protocol requires a good source of id numbers and these
|
||||
* numbers should be unpredictable for spoofing reasons. There are
|
||||
* three methods for generating them here and you must define exactly
|
||||
* one of them. In increasing order of preference:
|
||||
*
|
||||
* DNS_USE_GETTIMEOFDAY_FOR_ID:
|
||||
* Using the bottom 16 bits of the usec result from gettimeofday. This
|
||||
* is a pretty poor solution but should work anywhere.
|
||||
* DNS_USE_CPU_CLOCK_FOR_ID:
|
||||
* Using the bottom 16 bits of the nsec result from the CPU's time
|
||||
* counter. This is better, but may not work everywhere. Requires
|
||||
* POSIX realtime support and you'll need to link against -lrt on
|
||||
* glibc systems at least.
|
||||
* DNS_USE_OPENSSL_FOR_ID:
|
||||
* Uses the OpenSSL RAND_bytes call to generate the data. You must
|
||||
* have seeded the pool before making any calls to this library.
|
||||
*
|
||||
* The library keeps track of the state of nameservers and will avoid
|
||||
* them when they go down. Otherwise it will round robin between them.
|
||||
*
|
||||
@ -513,6 +488,9 @@ void evdns_set_log_fn(evdns_debug_log_fn_type fn);
|
||||
is bad for security.
|
||||
|
||||
@param fn the new callback, or NULL to use the default.
|
||||
|
||||
NOTE: This function has no effect in Libevent 2.0.4-alpha and later,
|
||||
since Libevent now provides its own secure RNG.
|
||||
*/
|
||||
void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void));
|
||||
|
||||
@ -521,6 +499,9 @@ void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void));
|
||||
the same function as passed to evdns_set_transaction_id_fn to generate
|
||||
bytes two at a time. If a function is provided here, it's also used
|
||||
to generate transaction IDs.
|
||||
|
||||
NOTE: This function has no effect in Libevent 2.0.4-alpha and later,
|
||||
since Libevent now provides its own secure RNG.
|
||||
*/
|
||||
void evdns_set_random_bytes_fn(void (*fn)(char *, size_t));
|
||||
|
||||
|
||||
@ -525,6 +525,18 @@ void evutil_freeaddrinfo(struct evutil_addrinfo *ai);
|
||||
|
||||
const char *evutil_gai_strerror(int err);
|
||||
|
||||
/* Generate n bytes of secure pseudorandom data, and store them in buf.
|
||||
*
|
||||
* By default, Libevent uses an ARC4-based random number generator, seeded
|
||||
* using the platform's entropy source (/dev/urandom on Unix-like systems;
|
||||
* CryptGenRandom on Windows).
|
||||
*/
|
||||
void evutil_secure_rng_get_bytes(void *buf, size_t n);
|
||||
|
||||
int evutil_secure_rng_init(void);
|
||||
|
||||
void evutil_secure_rng_add_bytes(const char *dat, size_t datlen);
|
||||
|
||||
#ifdef __cplusplus
|
||||
}
|
||||
#endif
|
||||
|
||||
@ -704,6 +704,7 @@ end:
|
||||
evdns_close_server_port(port2);
|
||||
}
|
||||
|
||||
#if 0
|
||||
static void
|
||||
dumb_bytes_fn(char *p, size_t n)
|
||||
{
|
||||
@ -713,6 +714,7 @@ dumb_bytes_fn(char *p, size_t n)
|
||||
for(i=0;i<n;++i)
|
||||
p[i] = (char)(rand() & 7);
|
||||
}
|
||||
#endif
|
||||
|
||||
static void
|
||||
dns_inflight_test(void *arg)
|
||||
@ -727,9 +729,11 @@ dns_inflight_test(void *arg)
|
||||
|
||||
tt_assert(regress_dnsserver(base, &portnum, reissue_table));
|
||||
|
||||
#if 0
|
||||
/* Make sure that having another (very bad!) RNG doesn't mess us
|
||||
* up. */
|
||||
evdns_set_random_bytes_fn(dumb_bytes_fn);
|
||||
#endif
|
||||
|
||||
dns = evdns_base_new(base, 0);
|
||||
tt_assert(!evdns_base_nameserver_ip_add(dns, "127.0.0.1:53900"));
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user