Re: [PATCH] cifs: allow guest mounts to work for smb3.11

["Aurélien Aptel" <aaptel@suse.com>]

Ronnie Sahlberg <lsahlber@redhat.com> writes:

> Fix Guest/Anonymous sessions so that they work with SMB 3.11.
>
> In git commit 6188f28 tightened the conditions and forced signing for
> the SMB2-TreeConnect commands as per MS-SMB2.

We could add a

    Fixes: 6188f28bf608 ("Tree connect for SMB3.1.1 must be signed for non-encrypted shares")

tag in the commit message.
>  
> -	/* 3.11 tcon req must be signed if not encrypted. See MS-SMB2 3.2.4.1.1 */
> +	/*
> +	 * 3.11 tcon req must be signed if not encrypted. See MS-SMB2 3.2.4.1.1
> +	 * unless it is guest or anonymous user. See MS-SMB2 3.2.5.3.1
> +	 */
>  	if ((ses->server->dialect == SMB311_PROT_ID) &&
> -	    !smb3_encryption_required(tcon))
> +	    !smb3_encryption_required(tcon) &&
> +	    !(ses->session_flags & (SMB2_SESSION_FLAG_IS_GUEST|SMB2_SESSION_FLAG_IS_NULL)))
>  		req->sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
>  
>  	memset(&rqst, 0, sizeof(struct smb_rqst));

I suspect there might more (and/or better) places to check. If you grep for
SMB2_FLAGS_SIGNED there are a couple of other places that should be
considered:

smb2_hdr_assemble() { ...
	if (tcon->ses && tcon->ses->server && tcon->ses->server->sign &&
	    !smb3_encryption_required(tcon))
		shdr->Flags |= SMB2_FLAGS_SIGNED;
...
}

cifs_get_smb_ses() { ...
	ses->sectype = volume_info->sectype;
	ses->sign = volume_info->sign;

	mutex_lock(&ses->session_mutex);
	rc = cifs_negotiate_protocol(xid, ses);
	if (!rc)
		rc = cifs_setup_session(xid, ses, volume_info->local_nls);
	mutex_unlock(&ses->session_mutex);
	if (rc)
		goto get_ses_fail;
...
}

After negprot and before sess setup we already know the protocol version so I guess there
could be some patch there as well.

See also SMB2_logoff(), SMB2_ioctl_init(), cifs_enable_signing()

Cheers,
-- 
Aurélien Aptel / SUSE Labs Samba Team
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