x/crypto/ssh: PublicKey Fingerprint

[dragon3]

It would be useful if PublicKey interface has Fingerprint method which returns the value described bellow:
http://tools.ietf.org/html/rfc4716#section-4

Now I'm trying to make my ssh server with go.
When I made it with python twisted.conch, I used twisted.conch.ssh.keys.Key#fingerprint method to find user's public key, It was useful.

[ianlancetaylor]

CC @hanwen @agl

[hanwen]

As the RFC describes, it's just the md5 of PublicKey.Marshal().

h := md5.New()
h.Write(key.Marshal())
fp := fmt.Sprintf("%x", h.Sum(nil))

there is no need to add this to the SSH package.

[dragon3]

@hanwen Thank you for your comment.

I know that I can get fingerprint with as you said and "separate by colons".
But I think it is convenient if PublicKey has that, because I found many developers write own "fingerprint" function/method ( I searched on github ).

[adg]

It seems like a reasonable feature to implement a standards-compliant fingerprint format method.

[dragon3]

@adg @agl Thank you for your response!

[hanwen]

are there other features that you miss? I am not per se against utility methods like these in a centralized place, but the package is quite big as it is. Next thing we know, we'd be adding a parser for .ssh/known_hosts and .ssh/config.

If there are more utility methods missing, we might have enough for a ssh/sshutil package. (in retrospect, the handling of Authorized keys should have probably been moved out of the main package too.)

[dragon3]

@hanwen

are there other features that you miss?

No, that's it so far.

[dragon3]

It's been almost 1 year since I created this issue, so I'm closing this issue.
Please let me know and re-open this issue if you are still interested in this issue.

Thank you!

[stouset]

As the RFC describes, it's just the md5 of PublicKey.Marshal().

You're literally suggesting here that you'd rather users of this library consult an RFC than for you to provide and implement a simple three-line function.

I really, really, really don't understand this mentality. Yes, it's a simple implementation. But a) having to look this procedure up costs your users time, b) having to reimplement, maintain, and test this function costs your users more time, and c) if 1,000 developers implement this on their own, at least one of these implementations will have a bug.

Why not just implement this once, and save your users a pointless duplication of time and effort?

[bradfitz]

@dragon3, no harm keeping this open. Still seems like a valid request.