discuss on draft-ietf-secsh-dns-04.txt

[Randy Bush <randy@psg.com>]

1. Introduction

   The SSH [5] protocol provides secure remote login and other secure
   network services over an insecure network.  The security of the
   connection relies on the server authenticating itself to the client.

it also relies on the user on the client host authenticating
themself to the server.  though this is not germane to this
document, the above statement could be dangerous out of context.

---

   Server authentication is normally done by presenting the fingerprint
   of an unknown public key to the user for verification.

the public key is not unknown, in fact the opposite.  if it was
unknown, then all ssh would offer is being able to talk to the same
liar all the time. :-)

perhaps "unique" is what was meant?

---

2.4 Authentication

   A public key verified using this method MUST only be trusted if the
   SSHFP resource record (RR) used for verification was authenticated by
   a trusted SIG RR.

may want to say that the trust must either come from a validated
trust descent from the root or from a validated descent from a zone
trusted because of a locally known association.

---

   The overall security of using SSHFP for SSH host key verification is
   dependent on detailed aspects of how verification is done in SSH
   implementations.

and of the practices of securing the data inserted in the SSHFP RR
in the dns and in the client host's diligence in accessing those
data securely.  c.f. the discussion on
draft-ietf-dnsext-ad-is-secure-06.txt

---

nits:

   fingerprint out-of-band before accepting the key, many users blindly
   accepts the presented key.
         ^
-
   algorithm and fingerprint of the key received from the SSH server
   matches the algorithm and fingerprint of one of the SSHFP resource
        ^^
-
      A message digest of the public key, using the message digest
      algorithm specified in the SSHFP fingerprint type, MUST match the
      SSH FP fingerprint.
         ^
-
3.2 Presentation Format of the SSHFP RR

   The presentation format of the SSHFP resource record consists of two
   numbers (algorithm and fingerprint type) followed by the fingerprint
   itself presented in hex, e.g:

         host.example.  SSHFP 2 1 123456789abcdef67890123456789abcdef67890

well bad wording, actually, as the example shows, the presentation
format consists of the label, the RR type, SSHFP, and ...

randy