wireshark decryption

[Aurélien Aptel]

Stefan Metzmacher <metze at samba.org> writes:
> ntlmssph->session_key is not the 32bit "session key" (which seems to be
> a key into a session array instead of being a crypto key) used in
> SMB1,

Fair enough.

> it's the session key that resulted out of the ntlmssp exchange.

So, is this key really supposed to be used as-is to derive the crypto
keys?

The Microsoft Open Specifications Support Team says this about session
keys [1]:

> Note: These cryptographic keys are all derived from the SessionKey. As
> a result, SMB 3.0 signing and encryption is as secure as the session
> key. Not only must this key be unique and very random, but also it
> needs be kept secret.

If the ntlmssph->session_key is read on the wire it's not
secret. Something is not right.

1: https://blogs.msdn.microsoft.com/openspecification/2012/10/05/encryption-in-smb-3-0-a-protocol-perspective/

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Aurélien Aptel / SUSE Labs Samba Team
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