Big thanks to Solar Designer who pointed out a bug in bcrypt

salt generation code.  He also urged using better random source
and making possible to choose using bcrypt and xdes rounds more
easily.  So, here's patch:

* For all salt generation, use Solar Designer's own code.  This
  is mostly due fact that his code is more fit for get_random_bytes()
  style interface.
* New function: gen_salt(type, rounds).  This lets specify iteration
  count for algorithm.
* random.c: px_get_random_bytes() function.
  Supported randomness soure: /dev/urandom, OpenSSL PRNG, libc random()
  Default: /dev/urandom.
* Draft description of C API for pgcrypto functions.

New files: API, crypt-gensalt.c, random.c

Marko Kreen

1 files changed, 28 insertions, 0 deletions

diff --git a/contrib/pgcrypto/README.pgcrypto b/contrib/pgcrypto/README.pgcrypto
index 7173710bc3f..c79f996a324 100644
--- a/contrib/pgcrypto/README.pgcrypto
+++ b/contrib/pgcrypto/README.pgcrypto
@@ -9,6 +9,13 @@ INSTALLATION
 
 Edit makefile, if you want to use any external library.
 
+NB!  Default randomness source is /dev/urandom device.  If you
+do not have it, you also need to edit Makefile to let pgcrypto
+use either OpenSSL PRNG or libc random() PRNG.  Using libc random()
+is discouraged.
+
+After editing Makefile:
+
 make
 make install
 
@@ -73,6 +80,27 @@ gen_salt(type::text)::text
 	When you use --enable-system-crypt then note that system
 	libcrypt may not support them all.
 
+gen_salt(type::text, rounds::int4)::text
+
+	same as above, but lets user specify iteration count
+	for algorithm.  Number is algotithm specific:
+
+	type	default	min	max
+	---------------------------------
+	xdes	725	1	16777215
+	bf	6	4	31
+
+	In case of xdes there is a additional limitation that the
+	count must be a odd number.
+
+	The higher the count, the more time it takes to calculate
+	crypt and therefore the more time to break it.  But beware!
+	With too high count it takes a _very_long_ time to
+	calculate it.
+
+	For maximum security, you should choose the 'bf' crypt
+	and use maximum number of rounds you can still tolerate.
+
 encrypt(data::bytea, key::bytea, type::text)::bytea
 decrypt(data::bytea, key::bytea, type::text)::bytea
 encrypt_iv(data::bytea, key::bytea, iv::bytea, type::text)::bytea