Hongwei, > A quick clarification for the AES bit in Negotiate Flag, as shown in > 3.1.4.2. The information in the document regarding this bit is wrong. Bit W > NETLOGON_NEG_SUPPORTS_AES_SHA2 (0x00400000) is not supported in Windows > 7/Windows Server 2008 R2. The right bit to negotiate AES support should be > NETLOGON_NEG_SUPPORTS_AES(0x01000000), as you already indicated. If you > use bit 0x00400000 to negotiate the AES support, it might be the source of > your problem.
I was already only using the correct bit. > I will file a request to fix this problem in the document. Meanwhile, I > will work on the AES encryption details for Schannel. Thanks! metze > -----Original Message----- > From: Stefan (metze) Metzmacher [mailto:me...@samba.org] > Sent: Friday, August 28, 2009 12:00 PM > To: Hongwei Sun > Cc: p...@tridgell.net; cifs-proto...@samba.org > Subject: Re: [Pfif] MS-NRPC: AES Schannel problems > > Stefan (metze) Metzmacher schrieb: >> Hongwei, >> >>> The SharedSecret used for AES session key computation, as described in >>> 3.1.4.3 MS-NRPC , should be the NTOWF (MD4(UNICODE(Passwd))) of the >>> plaintext password. The section 3.1.1 of MS-NRPC explains what a >>> SharedSecret is used for session key calculation in Windows >>> implementations. The SharedSecret is stored in UnicodePwd AD attribute. >>> Please see section 3.1.1 and Windows Behavior notes <66>,<67> of MS-NRPC >>> for details. >> Yes, I saw that and that's why I've also done it like this, but I was >> wondering why Section 3.4.1 has M4SS := MD4(UNICODE(SharedSecret)) >> explicit for the hmac_md5 session key and the des session key. >> >> I think it would make sense to also add it to the hmac_sha256 section >> in order to remove the confusion I had. >> >>> I will continue working on all questions related to AES encryption. >> Thanks, as it seems I compute the session key correct, this is the >> place >> (netlogon_creds_step_crypt()) where I have a bug, because I'm getting >> access denied when I try DCERPC_SCHANNEL_AES against a w2k8r2rc server. >> > > Please also provide details about the aes encryption used when schannel acts > as security provider for dcerpc. > > I noticed that the documentation on has only the > NETLOGON_NEG_SUPPORTS_AES_SHA2 (0x00400000) flag, but w2k8r2 used the new > flag NETLOGON_NEG_SUPPORTS_AES(0x01000000). > > I assume the docs may missing also some crypto details, because of this... > > metze >
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