== The relationship between SSH, SSL, and the Heartbleed bug

I will lead with the summary: since the [[Heartbleed bug
http://heartbleed.com/]] is a bug in OpenSSL's implementation of a part
of the TLS protocol, no version or implementation of SSH is affected by
Heartbleed because the SSH protocol is not built on top of TLS.

So, there's four things involved here:

* [[SSL aka TLS http://en.wikipedia.org/wiki/Transport_Layer_Security]]
  is the underlying network encryption protocol used for HTTPS and
  a bunch of other SSL/TLS things. [[Heartbleed http://heartbleed.com/]]
  is an error in implementing the 'TLS heartbeat' protocol extension
  to the TLS protocol. A number of other secure protocols are built
  partially or completely on top of TLS, such as [[OpenVPN
  http://en.wikipedia.org/wiki/OpenVPN]].

* [[SSH http://en.wikipedia.org/wiki/Secure_Shell]] is the protocol
  used for, well, SSH connections. It's completely separate from
  TLS and is not layered on top of it in any way. However, TLS and
  SSH both use a common set of cryptography primitives such as
  [[Diffie-Hellman key exchange
  http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange]], [[AES
  http://en.wikipedia.org/wiki/Advanced_Encryption_Standard]], and
  [[SHA1 http://en.wikipedia.org/wiki/SHA-1]].

  (Anyone sane who's designing a secure protocol reuses these
  primitives instead of trying to invent their own.)

* OpenSSL is an implementation of SSL/TLS in the form of a large
  cryptography library. It also exports a whole bunch of functions
  and so on that do various cryptography primitives and other
  lower-level operations that are useful for things doing cryptography
  in general.

* OpenSSH is one implementation of the SSH protocol. It uses various
  functions exported by OpenSSL for a lot of cryptography related
  things such as generating randomness, but it doesn't use the
  SSL/TLS portions of OpenSSL because SSH (the protocol) doesn't
  involve TLS (the protocol).

Low level flaws in OpenSSL such as [[Debian breaking its randomness
http://www.debian.org/security/2008/dsa-1571]] can affect OpenSSH
when OpenSSH uses something that's affected by the low level flaw.
In the case of the Debian issue, [[OpenSSH gets its random numbers
from OpenSSL SshEncryptionProtection]] and so was affected in [[a
number of ways ../linux/DebianSSLConsequences]].

High level flaws in OpenSSL's implementation of TLS itself will
never affect OpenSSH because OpenSSH simply doesn't use those bits
of OpenSSL. For instance, if OpenSSL turns out to have an SSL
certificate verification bug (which happened recently with other
SSL implementations) it won't affect OpenSSH's SSH user and host
key verification.

As a corollary, OpenSSH (and all SSH implementations) aren't
directly affected by TLS protocol attacks such as [[BEAST
http://en.wikipedia.org/wiki/Transport_Layer_Security#BEAST_attack]] or
[[Lucky Thirteen http://en.wikipedia.org/wiki/Lucky_Thirteen_attack]],
although people may be able to develop similar attacks against SSH
using the same general principles.