From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: "cc@sse-ag.ch" <cc@sse-ag.ch>,
        "pgsql-docs@lists.postgresql.org" <pgsql-docs@lists.postgresql.org>
Subject: Re: Potential vuln in example for "F.25.1.1. digest()"
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Tue, 17 Aug 2021 11:06:34 -0700"
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Date: Tue, 17 Aug 2021 14:33:17 -0400
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Tuesday, August 17, 2021, PG Doc comments form <noreply@postgresql.or=
g>
> wrote:
>> in "F.25.1.1. digest()" you suggest:
>> =

>> CREATE OR REPLACE FUNCTION sha1(bytea) returns text AS $$
>> SELECT encode(digest($1, 'sha1'), 'hex')
>> $$ LANGUAGE SQL STRICT IMMUTABLE;
>> =

>> While this is a great example, it may expose a database app to
>> vulnerabilities if the attacker succeeds in overriding the function
>> sha1(...) in the app's user context (schema)

> You should read this:
> https://wiki.postgresql.org/wiki/A_Guide_to_CVE-2018-1058%3A_Protect_You=
r_Search_Path

Yeah.  I can't get terribly excited about trying to make this one
example unconditionally-secure; there are dozens if not hundreds
of similar cases in our docs.  Trying to make them all safe
against insecure search paths would mostly result in unreadable
examples.

			regards, tom lane