Re: Encoding protection for pgcrypto

On Fri, Feb 9, 2024 at 5:34 PM cary huang <hcary328(at)gmail(dot)com> wrote:
>
> The following review has been posted through the commitfest application:
> make installcheck-world: tested, failed
> Implements feature: not tested
> Spec compliant: not tested
> Documentation: not tested
>
> Hello
>
> I had a look at your patch, which applies fine to PostgreSQL master. I noticed that the new regression tests you have added to test utf-8 encoding fails on my setup (make check) with the following diffs:
>
> ---------------------------------------
> @ -13,6 +13,7 @@
> =ivrD
> -----END PGP MESSAGE-----
> '), '0123456789abcdefghij'), 'sha1');
> +ERROR: invalid byte sequence for encoding "UTF8": 0x91
> -- Database encoding protection. Ciphertext source:
> -- printf '\xe0\xe0\xbff' | gpg --batch --passphrase mykey --textmode --armor --symmetric
> select pgp_sym_decrypt(dearmor('
> @@ -23,5 +24,5 @@
> =QKy4
> -----END PGP MESSAGE-----
> '), 'mykey', 'debug=1');
> +ERROR: invalid byte sequence for encoding "UTF8": 0xe0 0xe0 0xbf
> \quit
> -\endif
> ---------------------------------------
>
> I am not sure but it seems that you intentionally provide a text input that would produce a non-utf-8 compliant decrypted output, which triggers the error from within "pg_verifymbstr()" call that you have added in pgp-pgsql.c? Are the errors expected in your new test case? If so, then the tests shall pass instead because it has caught a invalid encoding in decrypted output.

Thanks for sharing that, I had updated the pgp-decrypt_utf8.out in the
v2.patch which will pass the `make -C contrib/pgcrypto check`.

> Generally, I am ok with the extra encoding check after text decryption but do not think if it is a good idea to just error out and abort the transaction when it detects invalid encoding character. text decryption routines may be used quite frequently and users generally do not expect them to abort transaction. It may be ok to just give them a warning about invalid character encoding.

Thanks for pointing that out. The goal for this patch is to fix the
encoding for the TEXT return value because by default the PostgreSQL
TEXT type should have the same encoding as the database encoding. So I
only added mbverify for the pgp_sym_decrypt_text and
pgp_pub_decrypt_text functions. If customers want to use these two
functions without encoding, they should use pgp_pub_decrypt_bytea and
pgp_sym_decrypt_bytea because BYTEA is represented as a binary string
in PostgreSQL.

Please let me know if you have more questions or concerns. Thanks!

> thanks
> --------------------
> Cary Huang
> Highgo Software - Canada
> www.highgo.ca