BUG #4791: NULL value in function causes reproducible segmentation fault

The following bug has been logged online:

Bug reference: 4791
Logged by: Sikkerhed.org ApS
Email address: support(at)sikkerhed(dot)org
PostgreSQL version: 8.3.7-0lenny1
Operating system: Debian GNU/Linux 5.0.1 stable (fully updated)
Description: NULL value in function causes reproducible segmentation
fault
Details:

We are using a couple of functions in PostgreSQL, namely

CREATE OR REPLACE FUNCTION digest(text, text) RETURNS bytea AS
'$libdir/pgcrypto', 'pg_digest' LANGUAGE 'C';

CREATE OR REPLACE FUNCTION sha1(text) RETURNS text AS 'SELECT
ENCODE(DIGEST($1, ''sha1''), ''hex'') AS result' LANGUAGE 'SQL';

We experienced a bad crash on our production server, and narrowed it down to
a reproducible test case.

The following query will crash the server every time:

SELECT SHA1(NULL);

Please let us know if you require more information.