greenplumn pg_strong_random 源码

greenplumn pg_strong_random 代码

文件路径：/src/port/pg_strong_random.c

/*-------------------------------------------------------------------------
 *
 * pg_strong_random.c
 *	  generate a cryptographically secure random number
 *
 * Our definition of "strong" is that it's suitable for generating random
 * salts and query cancellation keys, during authentication.
 *
 * Note: this code is run quite early in postmaster and backend startup;
 * therefore, even when built for backend, it cannot rely on backend
 * infrastructure such as elog() or palloc().
 *
 * Copyright (c) 1996-2019, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  src/port/pg_strong_random.c
 *
 *-------------------------------------------------------------------------
 */

#include "c.h"

#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>

#ifdef USE_OPENSSL
#include <openssl/rand.h>
#endif
#ifdef WIN32
#include <wincrypt.h>
#endif

#ifdef WIN32
/*
 * Cache a global crypto provider that only gets freed when the process
 * exits, in case we need random numbers more than once.
 */
static HCRYPTPROV hProvider = 0;
#endif

#if defined(USE_DEV_URANDOM)
/*
 * Read (random) bytes from a file.
 */
static bool
random_from_file(const char *filename, void *buf, size_t len)
{
	int			f;
	char	   *p = buf;
	ssize_t		res;

	f = open(filename, O_RDONLY, 0);
	if (f == -1)
		return false;

	while (len)
	{
		res = read(f, p, len);
		if (res <= 0)
		{
			if (errno == EINTR)
				continue;		/* interrupted by signal, just retry */

			close(f);
			return false;
		}

		p += res;
		len -= res;
	}

	close(f);
	return true;
}
#endif

/*
 * pg_strong_random
 *
 * Generate requested number of random bytes. The returned bytes are
 * cryptographically secure, suitable for use e.g. in authentication.
 *
 * We rely on system facilities for actually generating the numbers.
 * We support a number of sources:
 *
 * 1. OpenSSL's RAND_bytes()
 * 2. Windows' CryptGenRandom() function
 * 3. /dev/urandom
 *
 * The configure script will choose which one to use, and set
 * a USE_*_RANDOM flag accordingly.
 *
 * Returns true on success, and false if none of the sources
 * were available. NB: It is important to check the return value!
 * Proceeding with key generation when no random data was available
 * would lead to predictable keys and security issues.
 */
bool
pg_strong_random(void *buf, size_t len)
{
	/*
	 * When built with OpenSSL, use OpenSSL's RAND_bytes function.
	 */
#if defined(USE_OPENSSL_RANDOM)
	int			i;

	/*
	 * Check that OpenSSL's CSPRNG has been sufficiently seeded, and if not
	 * add more seed data using RAND_poll().  With some older versions of
	 * OpenSSL, it may be necessary to call RAND_poll() a number of times.
	 */
#define NUM_RAND_POLL_RETRIES 8

	for (i = 0; i < NUM_RAND_POLL_RETRIES; i++)
	{
		if (RAND_status() == 1)
		{
			/* The CSPRNG is sufficiently seeded */
			break;
		}

		if (RAND_poll() == 0)
		{
			/*
			 * RAND_poll() failed to generate any seed data, which means that
			 * RAND_bytes() will probably fail.  For now, just fall through
			 * and let that happen.  XXX: maybe we could seed it some other
			 * way.
			 */
			break;
		}
	}

	if (RAND_bytes(buf, len) == 1)
		return true;
	return false;

	/*
	 * Windows has CryptoAPI for strong cryptographic numbers.
	 */
#elif defined(USE_WIN32_RANDOM)
	if (hProvider == 0)
	{
		if (!CryptAcquireContext(&hProvider,
								 NULL,
								 MS_DEF_PROV,
								 PROV_RSA_FULL,
								 CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
		{
			/*
			 * On failure, set back to 0 in case the value was for some reason
			 * modified.
			 */
			hProvider = 0;
		}
	}
	/* Re-check in case we just retrieved the provider */
	if (hProvider != 0)
	{
		if (CryptGenRandom(hProvider, len, buf))
			return true;
	}
	return false;

	/*
	 * Read /dev/urandom ourselves.
	 */
#elif defined(USE_DEV_URANDOM)
	if (random_from_file("/dev/urandom", buf, len))
		return true;
	return false;

#else
	/* The autoconf script should not have allowed this */
#error no source of random numbers configured
#endif
}

相关信息

greenplumn 源码目录

相关文章

greenplumn chklocale 源码

greenplumn crypt 源码

greenplumn dirent 源码

greenplumn dirmod 源码

greenplumn dlopen 源码

greenplumn erand48 源码

greenplumn fls 源码

greenplumn fseeko 源码

greenplumn getaddrinfo 源码

greenplumn getopt 源码