Re: [PATCH v4] gpg-interface.c: detect and reject multiple signatures on commits

From: Duy Nguyen <pclouds@gmail.com>
Date: Nov 3, 2018, 15:17 UTC
Message-ID: <CACsJy8DKD3F3o74gTHW-WEL_hpB8x+oaWX8_SwN01Nmz3W9Z_w@mail.gmail.com>
In-Reply-To: <20181020193020.28517-1-mgorny@gentoo.org>

On Sat, Oct 20, 2018 at 9:31 PM Michał Górny <mgorny@gentoo.org> wrote:

Show 15 quoted lines

> +test_expect_success GPG 'detect fudged commit with double signature' '
> +       sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
> +       sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
> +               sed -e "s/^gpgsig//;s/^ //" | gpg --dearmor >double-sig1.sig &&
> +       gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
> +       cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
> +       sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/gpgsig /;2,\$s/^/ /" \
> +               double-combined.asc > double-gpgsig &&
> +       sed -e "/committer/r double-gpgsig" double-base >double-commit &&
> +       git hash-object -w -t commit double-commit >double-commit.commit &&
> +       test_must_fail git verify-commit $(cat double-commit.commit) &&
> +       git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
> +       grep "BAD signature from" double-actual &&
> +       grep "Good signature from" double-actual
> +'

This test fails on 'master' today for me

gpg: WARNING: multiple signatures detected. Only the first will be checked. gpg: Signature made Sat Nov 3 15:13:28 2018 UTC gpg: using DSA key 13B6F51ECDDE430D gpg: issuer "committer@example.com" gpg: BAD signature from "C O Mitter <committer@example.com>" [ultimate] gpg: BAD signature from "C O Mitter <committer@example.com>" [ultimate] not ok 16 - detect fudged commit with double signature

Perhaps my gpg is too old?

$ gpg --version gpg (GnuPG) 2.1.15 libgcrypt 1.7.3 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

Home: /home/pclouds/.gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

-- 
Duy