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fe0a0b5993
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
112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* erand48.c
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*
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* This file supplies pg_erand48(), pg_lrand48(), and pg_srand48(), which
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* are just like erand48(), lrand48(), and srand48() except that we use
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* our own implementation rather than the one provided by the operating
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* system. We used to test for an operating system version rather than
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* unconditionally using our own, but (1) some versions of Cygwin have a
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* buggy erand48() that always returns zero and (2) as of 2011, glibc's
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* erand48() is strangely coded to be almost-but-not-quite thread-safe,
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* which doesn't matter for the backend but is important for pgbench.
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*
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*
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* Copyright (c) 1993 Martin Birgmeier
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* All rights reserved.
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*
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* You may redistribute unmodified or modified versions of this source
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* code provided that the above copyright notice and this and the
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* following conditions are retained.
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*
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* This software is provided ``as is'', and comes with no warranties
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* of any kind. I shall in no event be liable for anything that happens
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* to anyone/anything when using this software.
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*
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* IDENTIFICATION
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* src/port/erand48.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include <math.h>
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#define RAND48_SEED_0 (0x330e)
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#define RAND48_SEED_1 (0xabcd)
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#define RAND48_SEED_2 (0x1234)
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#define RAND48_MULT_0 (0xe66d)
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#define RAND48_MULT_1 (0xdeec)
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#define RAND48_MULT_2 (0x0005)
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#define RAND48_ADD (0x000b)
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static unsigned short _rand48_seed[3] = {
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RAND48_SEED_0,
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RAND48_SEED_1,
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RAND48_SEED_2
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};
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static unsigned short _rand48_mult[3] = {
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RAND48_MULT_0,
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RAND48_MULT_1,
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RAND48_MULT_2
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};
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static unsigned short _rand48_add = RAND48_ADD;
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static void
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_dorand48(unsigned short xseed[3])
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{
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unsigned long accu;
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unsigned short temp[2];
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accu = (unsigned long) _rand48_mult[0] * (unsigned long) xseed[0] +
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(unsigned long) _rand48_add;
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temp[0] = (unsigned short) accu; /* lower 16 bits */
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accu >>= sizeof(unsigned short) * 8;
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accu += (unsigned long) _rand48_mult[0] * (unsigned long) xseed[1] +
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(unsigned long) _rand48_mult[1] * (unsigned long) xseed[0];
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temp[1] = (unsigned short) accu; /* middle 16 bits */
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accu >>= sizeof(unsigned short) * 8;
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accu += _rand48_mult[0] * xseed[2] + _rand48_mult[1] * xseed[1] + _rand48_mult[2] * xseed[0];
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xseed[0] = temp[0];
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xseed[1] = temp[1];
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xseed[2] = (unsigned short) accu;
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}
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double
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pg_erand48(unsigned short xseed[3])
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{
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_dorand48(xseed);
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return ldexp((double) xseed[0], -48) +
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ldexp((double) xseed[1], -32) +
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ldexp((double) xseed[2], -16);
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}
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long
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pg_lrand48(void)
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{
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_dorand48(_rand48_seed);
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return ((long) _rand48_seed[2] << 15) + ((long) _rand48_seed[1] >> 1);
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}
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long
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pg_jrand48(unsigned short xseed[3])
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{
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_dorand48(xseed);
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return ((long) xseed[2] << 16) + ((long) xseed[1]);
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}
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void
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pg_srand48(long seed)
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{
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_rand48_seed[0] = RAND48_SEED_0;
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_rand48_seed[1] = (unsigned short) seed;
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_rand48_seed[2] = (unsigned short) (seed >> 16);
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_rand48_mult[0] = RAND48_MULT_0;
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_rand48_mult[1] = RAND48_MULT_1;
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_rand48_mult[2] = RAND48_MULT_2;
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_rand48_add = RAND48_ADD;
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}
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