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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

95
contrib/pgcrypto/pgp-pgsql.c
View File

@ -61,65 +61,6 @@ PG_FUNCTION_INFO_V1(pg_armor);
PG_FUNCTION_INFO_V1(pg_dearmor);
PG_FUNCTION_INFO_V1(pgp_armor_headers);
/*
* Mix a block of data into RNG.
*/
static void
add_block_entropy(PX_MD *md, text *data)
{
uint8 sha1[20];
px_md_reset(md);
px_md_update(md, (uint8 *) VARDATA(data), VARSIZE(data) - VARHDRSZ);
px_md_finish(md, sha1);
px_add_entropy(sha1, 20);
px_memset(sha1, 0, 20);
}
/*
* Mix user data into RNG. It is for user own interests to have
* RNG state shuffled.
*/
static void
add_entropy(text *data1, text *data2, text *data3)
{
PX_MD *md;
uint8 rnd[3];
if (!data1 && !data2 && !data3)
return;
if (px_get_random_bytes(rnd, 3) < 0)
return;
if (px_find_digest("sha1", &md) < 0)
return;
/*
* Try to make the feeding unpredictable.
*
* Prefer data over keys, as it's rather likely that key is same in
* several calls.
*/
/* chance: 7/8 */
if (data1 && rnd[0] >= 32)
add_block_entropy(md, data1);
/* chance: 5/8 */
if (data2 && rnd[1] >= 160)
add_block_entropy(md, data2);
/* chance: 5/8 */
if (data3 && rnd[2] >= 160)
add_block_entropy(md, data3);
px_md_free(md);
px_memset(rnd, 0, sizeof(rnd));
}
/*
* returns src in case of no conversion or error
*/
@ -432,11 +373,7 @@ init_work(PGP_Context **ctx_p, int is_text,
VARSIZE(args) - VARHDRSZ, ex);
if (err)
{
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(err))));
}
px_THROW_ERROR(err);
if (ex->debug)
px_set_debug_handler(show_debug);
@ -459,11 +396,6 @@ encrypt_internal(int is_pubenc, int is_text,
struct debug_expect ex;
text *tmp_data = NULL;
/*
* Add data and key info RNG.
*/
add_entropy(data, key, NULL);
init_work(&ctx, is_text, args, &ex);
if (is_text && pgp_get_unicode_mode(ctx))
@ -516,9 +448,7 @@ encrypt_internal(int is_pubenc, int is_text,
pgp_free(ctx);
mbuf_free(src);
mbuf_free(dst);
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(err))));
px_THROW_ERROR(err);
}
/* res_len includes VARHDRSZ */
@ -605,9 +535,7 @@ decrypt_internal(int is_pubenc, int need_text, text *data,
{
px_set_debug_handler(NULL);
mbuf_free(dst);
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(err))));
px_THROW_ERROR(err);
}
res_len = mbuf_steal_data(dst, &restmp);
@ -629,11 +557,6 @@ decrypt_internal(int is_pubenc, int need_text, text *data,
}
px_set_debug_handler(NULL);
/*
* add successful decryptions also into RNG
*/
add_entropy(res, key, keypsw);
return res;
}
@ -985,9 +908,7 @@ pg_dearmor(PG_FUNCTION_ARGS)
ret = pgp_armor_decode((uint8 *) VARDATA(data), data_len, &buf);
if (ret < 0)
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(ret))));
px_THROW_ERROR(ret);
res = palloc(VARHDRSZ + buf.len);
SET_VARSIZE(res, VARHDRSZ + buf.len);
memcpy(VARDATA(res), buf.data, buf.len);
@ -1041,9 +962,7 @@ pgp_armor_headers(PG_FUNCTION_ARGS)
&state->nheaders, &state->keys,
&state->values);
if (res < 0)
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(res))));
px_THROW_ERROR(res);
MemoryContextSwitchTo(oldcontext);
funcctx->user_fctx = state;
@ -1092,9 +1011,7 @@ pgp_key_id_w(PG_FUNCTION_ARGS)
res_len = pgp_get_keyid(buf, VARDATA(res));
mbuf_free(buf);
if (res_len < 0)
ereport(ERROR,
(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
errmsg("%s", px_strerror(res_len))));
px_THROW_ERROR(res_len);
SET_VARSIZE(res, VARHDRSZ + res_len);
PG_FREE_IF_COPY(data, 0);