linux-kernel - Re: CIFS regression mounting vers=1.0 NTLMSSP when hostname is too long

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Date:   Wed, 4 May 2022 00:43:42 -0500
From:   Steven French <sfrench@...ba.org>
To:     Paulo Alcantara <pc@....nz>, Byron Stanoszek <gandalf@...ds.org>
Cc:     linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: CIFS regression mounting vers=1.0 NTLMSSP when hostname is too
 long

makes sense - do you see anything related in the NTLMSSP doc?

Want to spin up a patch for SMB1 for this?

On 5/3/22 20:35, Paulo Alcantara wrote:
> Byron Stanoszek <gandalf@...ds.org> writes:
>
>> I would like to report a regression in the CIFS fs. Sometime between Linux 4.14
>> and 5.16, mounting CIFS with option vers=1.0 (and
>> CONFIG_CIFS_ALLOW_INSECURE_LEGACY=y set appropriately) with security type
>> NTLMSSP stopped working for me. The server side is a Windows 2003 Server.
>>
>> I found that this behavior depends on the length of the Linux client's
>> host+domain name (e.g. utsname()->nodename), where the mount works as long as
>> the name is 16 characters or less. Anything 17 or above returns -EIO, per the
>> following example:
> Looks like your server is expecting the WorkstationName field in
> AUTHENTICATE_MESSAGE payload to be 16 bytes long.  That is, NetBIOS name
> length as per rfc1001.
>
>> I implemented a workaround using the following patch:
>>
>> Signed-off-by: Byron Stanoszek <gandalf@...ds.org>
>> ---
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -101,7 +101,7 @@
>>    #define XATTR_DOS_ATTRIB "user.DOSATTRIB"
>>    #endif
>>
>> -#define CIFS_MAX_WORKSTATION_LEN  (__NEW_UTS_LEN + 1)  /* reasonable max for client */
>> +#define CIFS_MAX_WORKSTATION_LEN 16
>>
>>    /*
>>     * CIFS vfs client Status information (based on what we know.)
>>
>> I don't know if this patch is correct or will have any real effect outside of
>> the NTLMSSP session connect sequence, but it worked in my case.
> Perhaps we should be use TCP_Server_Info::workstation_RFC1001_name in
> fs/cifs/sess.c:build_ntlmssp_auth_blob() instead only when connecting to
> old servers by using insecure dialects -- like SMB1, in your case.