Replace PostmasterRandom() with a stronger source, second attempt.

This adds a new routine, pg_strong_random() for generating random bytes,
for use in both frontend and backend. At the moment, it's only used in
the backend, but the upcoming SCRAM authentication patches need strong
random numbers in libpq as well.

pg_strong_random() is based on, and replaces, the existing implementation
in pgcrypto. It can acquire strong random numbers from a number of sources,
depending on what's available:

- OpenSSL RAND_bytes(), if built with OpenSSL
- On Windows, the native cryptographic functions are used
- /dev/urandom

Unlike the current pgcrypto function, the source is chosen by configure.
That makes it easier to test different implementations, and ensures that
we don't accidentally fall back to a less secure implementation, if the
primary source fails. All of those methods are quite reliable, it would be
pretty surprising for them to fail, so we'd rather find out by failing
hard.

If no strong random source is available, we fall back to using erand48(),
seeded from current timestamp, like PostmasterRandom() was. That isn't
cryptographically secure, but allows us to still work on platforms that
don't have any of the above stronger sources. Because it's not very secure,
the built-in implementation is only used if explicitly requested with
--disable-strong-random.

This replaces the more complicated Fortuna algorithm we used to have in
pgcrypto, which is unfortunate, but all modern platforms have /dev/urandom,
so it doesn't seem worth the maintenance effort to keep that. pgcrypto
functions that require strong random numbers will be disabled with
--disable-strong-random.

Original patch by Magnus Hagander, tons of further work by Michael Paquier
and me.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRy3krN8quR9XujMVVHYtXJ0_60nqgVc6oUk8ygyVkZsA@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqRWkNYRRPJA7-cF+LfroYV10pvjdz6GNvxk-Eee9FypKA@mail.gmail.com

1 files changed, 0 insertions, 247 deletions

diff --git a/contrib/pgcrypto/random.c b/contrib/pgcrypto/random.c
deleted file mode 100644
index d72679e412d..00000000000
--- a/contrib/pgcrypto/random.c
+++ /dev/null
@@ -1,247 +0,0 @@
-/*
- * random.c
- *		Acquire randomness from system.  For seeding RNG.
- *
- * Copyright (c) 2001 Marko Kreen
- * All rights reserved.
- *
- * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
- *
- * contrib/pgcrypto/random.c
- */
-
-#include "postgres.h"
-
-#include "px.h"
-#include "utils/memdebug.h"
-
-/* how many bytes to ask from system random provider */
-#define RND_BYTES  32
-
-/*
- * Try to read from /dev/urandom or /dev/random on these OS'es.
- *
- * The list can be pretty liberal, as the device not existing
- * is expected event.
- */
-#if defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) \
-	|| defined(__NetBSD__) || defined(__DragonFly__) \
-	|| defined(__darwin__) || defined(__SOLARIS__) \
-	|| defined(__hpux) || defined(__HPUX__) \
-	|| defined(__CYGWIN__) || defined(_AIX)
-
-#define TRY_DEV_RANDOM
-
-#include <fcntl.h>
-#include <unistd.h>
-
-static int
-safe_read(int fd, void *buf, size_t count)
-{
-	int			done = 0;
-	char	   *p = buf;
-	int			res;
-
-	while (count)
-	{
-		res = read(fd, p, count);
-		if (res <= 0)
-		{
-			if (errno == EINTR)
-				continue;
-			return PXE_DEV_READ_ERROR;
-		}
-		p += res;
-		done += res;
-		count -= res;
-	}
-	return done;
-}
-
-static uint8 *
-try_dev_random(uint8 *dst)
-{
-	int			fd;
-	int			res;
-
-	fd = open("/dev/urandom", O_RDONLY, 0);
-	if (fd == -1)
-	{
-		fd = open("/dev/random", O_RDONLY, 0);
-		if (fd == -1)
-			return dst;
-	}
-	res = safe_read(fd, dst, RND_BYTES);
-	close(fd);
-	if (res > 0)
-		dst += res;
-	return dst;
-}
-#endif
-
-/*
- * Try to find randomness on Windows
- */
-#ifdef WIN32
-
-#define TRY_WIN32_GENRAND
-#define TRY_WIN32_PERFC
-
-#include <windows.h>
-#include <wincrypt.h>
-
-/*
- * this function is from libtomcrypt
- *
- * try to use Microsoft crypto API
- */
-static uint8 *
-try_win32_genrand(uint8 *dst)
-{
-	int			res;
-	HCRYPTPROV	h = 0;
-
-	res = CryptAcquireContext(&h, NULL, MS_DEF_PROV, PROV_RSA_FULL,
-							  (CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET));
-	if (!res)
-		res = CryptAcquireContext(&h, NULL, MS_DEF_PROV, PROV_RSA_FULL,
-			   CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET | CRYPT_NEWKEYSET);
-	if (!res)
-		return dst;
-
-	res = CryptGenRandom(h, RND_BYTES, dst);
-	if (res == TRUE)
-		dst += RND_BYTES;
-
-	CryptReleaseContext(h, 0);
-	return dst;
-}
-
-static uint8 *
-try_win32_perfc(uint8 *dst)
-{
-	int			res;
-	LARGE_INTEGER time;
-
-	res = QueryPerformanceCounter(&time);
-	if (!res)
-		return dst;
-
-	memcpy(dst, &time, sizeof(time));
-	return dst + sizeof(time);
-}
-#endif   /* WIN32 */
-
-
-/*
- * If we are not on Windows, then hopefully we are
- * on a unix-like system.  Use the usual suspects
- * for randomness.
- */
-#ifndef WIN32
-
-#define TRY_UNIXSTD
-
-#include <sys/types.h>
-#include <sys/time.h>
-#include <time.h>
-#include <unistd.h>
-
-/*
- * Everything here is predictible, only needs some patience.
- *
- * But there is a chance that the system-specific functions
- * did not work.  So keep faith and try to slow the attacker down.
- */
-static uint8 *
-try_unix_std(uint8 *dst)
-{
-	pid_t		pid;
-	int			x;
-	PX_MD	   *md;
-	struct timeval tv;
-	int			res;
-
-	/* process id */
-	pid = getpid();
-	memcpy(dst, (uint8 *) &pid, sizeof(pid));
-	dst += sizeof(pid);
-
-	/* time */
-	gettimeofday(&tv, NULL);
-	memcpy(dst, (uint8 *) &tv, sizeof(tv));
-	dst += sizeof(tv);
-
-	/* pointless, but should not hurt */
-	x = random();
-	memcpy(dst, (uint8 *) &x, sizeof(x));
-	dst += sizeof(x);
-
-	/* hash of uninitialized stack and heap allocations */
-	res = px_find_digest("sha1", &md);
-	if (res >= 0)
-	{
-		uint8	   *ptr;
-		uint8		stack[8192];
-		int			alloc = 32 * 1024;
-
-		VALGRIND_MAKE_MEM_DEFINED(stack, sizeof(stack));
-		px_md_update(md, stack, sizeof(stack));
-		ptr = px_alloc(alloc);
-		VALGRIND_MAKE_MEM_DEFINED(ptr, alloc);
-		px_md_update(md, ptr, alloc);
-		px_free(ptr);
-
-		px_md_finish(md, dst);
-		px_md_free(md);
-
-		dst += 20;
-	}
-
-	return dst;
-}
-#endif
-
-/*
- * try to extract some randomness for initial seeding
- *
- * dst should have room for 1024 bytes.
- */
-unsigned
-px_acquire_system_randomness(uint8 *dst)
-{
-	uint8	   *p = dst;
-
-#ifdef TRY_DEV_RANDOM
-	p = try_dev_random(p);
-#endif
-#ifdef TRY_WIN32_GENRAND
-	p = try_win32_genrand(p);
-#endif
-#ifdef TRY_WIN32_PERFC
-	p = try_win32_perfc(p);
-#endif
-#ifdef TRY_UNIXSTD
-	p = try_unix_std(p);
-#endif
-	return p - dst;
-}