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

Browse Source 
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
This commit is contained in:
Heikki Linnakangas
2016-12-05 13:42:59 +02:00
parent 5dc851afde
commit fe0a0b5993
42 changed files with 1473 additions and 1105 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
contrib/pgcrypto/openssl.c
View File

@ -712,49 +712,3 @@ px_find_cipher(const char *name, PX_Cipher **res)
*res = c;
return 0;
}
static int openssl_random_init = 0;
/*
* OpenSSL random should re-feeded occasionally. From /dev/urandom
* preferably.
*/
static void
init_openssl_rand(void)
{
if (RAND_get_rand_method() == NULL)
{
#ifdef HAVE_RAND_OPENSSL
RAND_set_rand_method(RAND_OpenSSL());
#else
RAND_set_rand_method(RAND_SSLeay());
#endif
}
openssl_random_init = 1;
}
int
px_get_random_bytes(uint8 *dst, unsigned count)
{
int res;
if (!openssl_random_init)
init_openssl_rand();
res = RAND_bytes(dst, count);
if (res == 1)
return count;
return PXE_OSSL_RAND_ERROR;
}
int
px_add_entropy(const uint8 *data, unsigned count)
{
/*
* estimate 0 bits
*/
RAND_add(data, count, 0);
return 0;
}