samba - Sep 2023 - Is 'sec=ntlmsspi' with 'seal' secure over an untrusted network?

Hello,

I'm using a cloud provider's storage solution, which only works with
SMB,
with username/password. I assume the best configuration with
'sec=ntlmsspi'
and 'seal'.

But is this secure over an untrusted network? (i.e. to satisfy a strict
security audit)

Microsoft states that "NTLMv2 is a little better, since it variable length
and salted hash, but not that much better" (than NTLMv1).
There's this article that talks about cracking NTLMSSP:
https://www.mike-gualtieri.com/posts/live-off-the-land-and-crack-the-ntlmssp-protocol

I'm wondering if NTLMSSPI avoids these issues?
Or whether `seal` encrypts the connection, avoiding leaking any information
in the first place? ("The encryption algorithm used is AES-128-CCM").
Or
whether the encrypted connection is established later.

Thanks for any thoughts on this!

Kind regards
Erik

On Wed, Sep 06, 2023 at 04:25:42PM +0200, Erik Schulz via samba
wrote:
>Hello,
>
>I'm using a cloud provider's storage solution, which only works with
SMB,
>with username/password. I assume the best configuration with
'sec=ntlmsspi'
>and 'seal'.
>
>But is this secure over an untrusted network? (i.e. to satisfy a strict
>security audit)
No, almost certainly not. They will need to provide krb5
auth to pass a strict security audit IMHO.
>Microsoft states that "NTLMv2 is a little better, since it variable
length
>and salted hash, but not that much better" (than NTLMv1).
>There's this article that talks about cracking NTLMSSP:
>https://www.mike-gualtieri.com/posts/live-off-the-land-and-crack-the-ntlmssp-protocol
>
>I'm wondering if NTLMSSPI avoids these issues?
No.
>Or whether `seal` encrypts the connection, avoiding leaking any information
>in the first place? ("The encryption algorithm used is
AES-128-CCM"). Or
>whether the encrypted connection is established later.
The encrypted connection is established after the NTLM auth,
as that is what sets up the session key.

On Wed, 2023-09-06 at 16:25 +0200, Erik Schulz via samba
wrote:
> Hello,
> I'm using a cloud provider's storage solution, which only works
with
> SMB,with username/password. I assume the best configuration with
> 'sec=ntlmsspi'and 'seal'.
> But is this secure over an untrusted network? (i.e. to satisfy a
> strictsecurity audit)
> Microsoft states that "NTLMv2 is a little better, since it variable
> lengthand salted hash, but not that much better" (than
> NTLMv1).There's this article that talks about cracking NTLMSSP:
>
https://www.mike-gualtieri.com/posts/live-off-the-land-and-crack-the-ntlmssp-protocol
> 
> I'm wondering if NTLMSSPI avoids these issues?Or whether `seal`
> encrypts the connection, avoiding leaking any informationin the first
> place? ("The encryption algorithm used is AES-128-CCM").
Orwhether
> the encrypted connection is established later.
The encryption is established after the NTLM completes.  Strong
passwords may make this an acceptable choice.

Kerberos is similar, actually, if you can get to the client/KDC
exchange then a weak user password can be brute forced. 

 This is why Samba 4.19 is significant, as we can claim to be Windows
2012 and have Windows clients use 'Kerberos Armoring' aka 'FAST'
(if
you set up the Group Polciies), but this is regarding the AD DC, not
your situation.

Andrew Bartlett

-- 
Andrew Bartlett (he/him)       https://samba.org/~abartlet/Samba Team Member
(since 2001) https://samba.orgSamba Team Lead               
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