Re: [stir] Review of draft-ietf-stir-passport-09

Hi Eric,

Thanks.  Answers inline.

-Chris

> On Oct 29, 2016, at 7:32 AM, Eric Rescorla <ekr@rtfm.com> wrote:
> 
> OVERALL
> This document would be easier to read if it came with an example
> at the beginning (perhaps the one in 9.1).
> 
> I've also been thinking about the use of a URL here. This has
> the result that it doesn't bind the certificate itself into the
> digital signature, but only the URL. So this implies that it's
> at least potentially possible to substitute one certificate
> for another with the same private key. Is that a concern here?

Other than stolen private key scenarios, which are a concern whether you use URL or not, I’m not sure of a reason why someone would want to do this for legitimate reasons and there would be any concern for multiple certificates being able to validate a call, or whether someone with legitimate access to the private key and would want to use this technique illegitimately would be a valid scenario unless they are a bad actor in the first place.

> 
> 
> S 4.3.
> Certificate chains are generally self-validating, so can you explain
> why you need HTTPS here? Clearly, it's good practice for confidentiality
> and to prevent other forms of attack, but still.

https://tools.ietf.org/html/rfc7515#section-4.1.5 <https://tools.ietf.org/html/rfc7515#section-4.1.5> does call for it.  I could certainly remove the direct reference to this fact and leave it to the generic reference to RFC7515.  It also technically calls for server identity validation using RFC6125 as well.

> 
> 
> S 5.2.
>    {
>    "dest":{
>           "tn":["12125551212"],
>               "uri":["sip:alice@example.com <mailto:sip%3Aalice@example.com>",
>                   "sip:bob@example.net <mailto:sip%3Abob@example.net>"]
>           },
>           "iat":"1443208345",
>           "orig":{"tn":"12155551212"}
>       }
> 
> This indentation seems weird. Should you be outdenting the "uri" line.

Simple format problem, fixed.

> 
> S 5.2.2.
> Given the ambiguity about multiple fingerprints, you should probably
> cite the 4572-bis draft.

Added.

> 
> 
> S 7.
>     The using protocol of the compact form of PASSporT MUST
> 
> This "using protocol" language is pretty odd. Maybe define a specific
> term somewhere else? "application protocol"?
> 

The “using protocol” was a suggestion from JP, so i’ll let him answer that.

> S 9.
>    JSON, as a canonical format, can include spaces and line breaks, and
>    key value pairs can occur in any order.
> 
> Doesn't this mean that JSON isn't canonical?

good point :) fixed.

> 
> 
> S A.1, A.2
> 
> These aren't actually X.509 structure. Also, the private key in S 8.1
> is in an OpenSSL-specific structure. Could you encode it in PKCS#8.

Ok so I’ll do this:

openssl pkcs8 -topk8 -nocrypt -in key.pem -out p8file.pem

-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgi7q2TZvN9VDFg8Vy
qCP06bETrR2v8MRvr89rn4i+UAahRANCAAQWfaj1HUETpoNCrOtp9KA8o0V79IuW
ARKt9C1cFPkyd3FBP4SeiNZxQhDrD0tdBHls3/wFe8++K2FrPyQF9vuh
-----END PRIVATE KEY——

Correct?

> 
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