Re: What ASN.1 got right

Michael Thomas <> Wed, 03 March 2021 00:43 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id C87EE3A1556 for <>; Tue, 2 Mar 2021 16:43:15 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.75
X-Spam-Status: No, score=-1.75 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.25, NICE_REPLY_A=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=no autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id fcdnT_qfyWZb for <>; Tue, 2 Mar 2021 16:43:14 -0800 (PST)
Received: from ( [IPv6:2607:f8b0:4864:20::1031]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 846123A1552 for <>; Tue, 2 Mar 2021 16:43:14 -0800 (PST)
Received: by with SMTP id d13-20020a17090abf8db02900c0590648b1so2000304pjs.1 for <>; Tue, 02 Mar 2021 16:43:14 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=fluffulence; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=w+jxPd6iuLp7Q5bUFjQRBWDKsQZY7T/OwlXp9G3IUw0=; b=nSjMasb7bFflVIdA6cpdwF7Jq8HCM/drJ4IDy7igau4CP2At6OcpGawlMFBSBpls3w bmaNppxw+mKQOGBj6NwzfSuTwpHa4hBsPY3I58MTEG7umlI/ckXw9G86meEBxGrlw394 fNH4kNfv/DnDlBlM192owH8AJLwf3dxBOLEMAL1Mtj8oFTAexEBYobqg8HAhQWdqQaSL RPAmn9+U9Q6+zu2rb5nYti1QdH0zjpocKfXUyjqyj+ZMwqnMudF0npO+bc+9r5aJLtRK jqdVQveu2nlrAPR4LC+Ig5J1sUL4q1E5eKxbHj+D+PLt41Fn6ZFx1i+KjqsrjnACAQzj Ls0A==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=w+jxPd6iuLp7Q5bUFjQRBWDKsQZY7T/OwlXp9G3IUw0=; b=uoINYD5RW5bjSYpC67L40/CT29pjj6oXky9YlGu/VpTq30xbY9elyuhI05Mjv4xUL8 jYAVZzTFamRo9hXmnC42HURlA8xk5i7nqGtjzIyGxLx6NmfRdBrAP6EqFXNXGX2c6dhe LkOH72+PnUYcYySCN655WMK9Ar4QX60n2SpvtkRDNmObXBw/roUdpZIOpUMi0xOQZw+a jEiSFsmsSOBmGMN14RJY7cBs7/oCReN7H3kxe4jfto8iFHj4wDOBcs9aEF8OAmlX4dv+ Na+bv8/RCkpw8rz5hI2TI+V9Mi7i88UlaI8lxmTsFkj8b90OAikFacl3pZ1CT0xrKUcp pHIQ==
X-Gm-Message-State: AOAM533rdXp1FZTCrE+TJ3iwmfZXBPobhC6p5ayNFc8WSEORGRm2oAGc 3g/RnIJfJQoyDfSFBI78oLqDpzL5Zzi7xw==
X-Google-Smtp-Source: ABdhPJwJ7L/pPANHQDjiiQ5FR09zCSbzCtZ1j4CdBXy6/QcN//QEIEh20yhF5xi2LStjcvRpZq8WTw==
X-Received: by 2002:a17:902:aa0a:b029:e4:c090:ad76 with SMTP id be10-20020a170902aa0ab02900e4c090ad76mr8588704plb.2.1614732192881; Tue, 02 Mar 2021 16:43:12 -0800 (PST)
Received: from mike-mac.lan ([]) by with ESMTPSA id d16sm16432794pfq.203.2021. (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Mar 2021 16:43:12 -0800 (PST)
Subject: Re: What ASN.1 got right
To: Nico Williams <>
Cc: Phillip Hallam-Baker <>, IETF Discussion Mailing List <>
References: <> <20210302183901.GV30153@localhost> <> <> <> <> <> <> <20210302234928.GX30153@localhost> <> <20210303002330.GZ30153@localhost>
From: Michael Thomas <>
Message-ID: <>
Date: Tue, 2 Mar 2021 16:43:10 -0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.8.0
MIME-Version: 1.0
In-Reply-To: <20210303002330.GZ30153@localhost>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Archived-At: <>
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: IETF-Discussion <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 03 Mar 2021 00:43:16 -0000

On 3/2/21 4:23 PM, Nico Williams wrote:
>> I'm talking about the server side sshd just fetching the associated ssh keys
>> with the user trying to log in, maybe with some authz sprinkled in for finer
>> granularity. It could be LDAP, it could whatever you want. I don't know how
>> configurable sshd is, so that might limit your choices.
> I wouldn't want to do this.  It's much more complex than the client
> sending a certificate.

Huh? It's a bit of configuration on the server side that is probably 
captured in provisioning systems. And client provisioning -- which is 
what certs imply -- is extremely problematic. How do I get a client ssh 
cert onto my phone's ssh app, for example? Not having to change client 
behavior or provisioning significantly simplifies the problem.

> And getting their public key(s) (they will almost certainly have more
> than one, and many ephemeral) into the directory is the equivalent of
> getting a certificate issued.  So you're not saving anything, and you're
> adding complexity, and if you're using LDAP you're not even getting rid
> of x.500 or ASN.1.
Not having to do anything at all on the client is a significant savings. 
I would much rather the help desk cost of nothing different than taking 
calls on how to install the ssh certs on exotic and not so exotic clients.
>> If you care about that, I suppose. I think most people do the leap of faith
>> and known_hosts ignores the problem.
> I very much care about that.  Certainly in a corporate network.

It's orthogonal to the client side authentication problem though.

>> I don't see how doing nothing at all on the client can be "infinitely
>> easier" than doing a lot of something else. [...]
> It's not nothing.  New keys?  Update the directory.  Same complexity as
> getting keys certified, only worse because the online CA only needs to
> be online when you want new keys / certs, but the directory has to be
> online any time you want to use those keys.

Uploading a new public keys is the ~same for both. Downloading a client 
cert is a whole lot of something. And if your corpro directory is down, 
you are already in a world of hurt. The advantage of offline 
verification in the age of 24/7 internet is very niche.

>> Is anybody using PKINIT?
> Yes.

Where? In any volume?