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From:   Junio C Hamano <gitster@pobox.com>
To:     Fabian Stelzer <fs@gigacodes.de>
Cc:     Fabian Stelzer via GitGitGadget <gitgitgadget@gmail.com>,
        git@vger.kernel.org, Han-Wen Nienhuys <hanwen@google.com>,
        "brian m. carlson" <sandals@crustytoothpaste.net>,
        "Randall S. Becker" <rsbecker@nexbridge.com>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Hans Jerry Illikainen <hji@dyntopia.com>,
        =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason <avarab@gmail.com>,
        Felipe Contreras <felipe.contreras@gmail.com>,
        Eric Sunshine <sunshine@sunshineco.com>,
        Gwyneth Morgan <gwymor@tilde.club>
Subject: Re: [PATCH v6 5/9] ssh signing: parse ssh-keygen output and verify
 signatures
References: <pull.1041.v5.git.git.1627391744.gitgitgadget@gmail.com>
        <pull.1041.v6.git.git.1627501009.gitgitgadget@gmail.com>
        <725764018ceb5bcecc748cc5169d4305ea9d7d23.1627501009.git.gitgitgadget@gmail.com>
        <xmqq35ry85or.fsf@gitster.g>
        <54671c83-4b1f-5e24-a6ad-226a4f45f952@gigacodes.de>
Date:   Thu, 29 Jul 2021 13:43:46 -0700
In-Reply-To: <54671c83-4b1f-5e24-a6ad-226a4f45f952@gigacodes.de> (Fabian
        Stelzer's message of "Thu, 29 Jul 2021 11:12:27 +0200")
Message-ID: <xmqqczr04zr1.fsf@gitster.g>
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Fabian Stelzer <fs@gigacodes.de> writes:

>>> +		/* Search for the last "with" to get the full principal */
>>> +		principal = line;
>>> +		do {
>>> +			search = strstr(line, " with ");
>>> +			if (search)
>>> +				line = search + 1;
>>> +		} while (search != NULL);
>>> +		sigc->signer = xmemdupz(principal, line - principal - 1);
>>> +		sigc->fingerprint = xstrdup(strstr(line, "key") + 4);
>> OK.  This does not care the "RSA" part, which is future resistant.
>> It assumes the <algo>:<fingerprint> comes after literal " key ",
>> which I think is a reasonable thing to do.
>> However, we never checked if the line has "key" in it, so
>> strstr(line, "key") + 4 may not be pointing at where this code
>> expects.
>
> Hmm. What would i do if i don't find "key"? Still mark the signature
> as valid an just leave fingerprint & key empty?

We didn't get a satisfactory response from the ssh-keygen we expect
that tells us that the external tool successfully decided that the
signature is good or bad.  I would feel safer if we said we did not
see a good signature in such a case.