ksmbd: do not sign response to session request for guest login

commit 5fde3c21cf33830eda7bfd006dc7f4bf07ec9fe6 upstream.

If ksmbd.mountd is configured to assign unknown users to the guest account
("map to guest = bad user" in the config), ksmbd signs the response.

This is wrong according to MS-SMB2 3.3.5.5.3:
   12. If the SMB2_SESSION_FLAG_IS_GUEST bit is not set in the SessionFlags
   field, and Session.IsAnonymous is FALSE, the server MUST sign the
   final session setup response before sending it to the client, as
   follows:
    [...]

This fixes libsmb2 based applications failing to establish a session
("Wrong signature in received").

Fixes: 9445e1eebdb7 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: Marios Makassikis <mmakassikis@freebox.fr>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 533742ebcb379cf8b2e1c5826efb497089e997cb..9b16ee657b51a6783d5a8b2232f4e1a45ecaaa9b 100644 (file)
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -8657,6 +8657,7 @@ int smb3_decrypt_req(struct ksmbd_work *work)
 bool smb3_11_final_sess_setup_resp(struct ksmbd_work *work)
 {
        struct ksmbd_conn *conn = work->conn;
+       struct ksmbd_session *sess = work->sess;
        struct smb2_hdr *rsp = smb2_get_msg(work->response_buf);
 
        if (conn->dialect < SMB30_PROT_ID)
@@ -8666,6 +8667,7 @@ bool smb3_11_final_sess_setup_resp(struct ksmbd_work *work)
                rsp = ksmbd_resp_buf_next(work);
 
        if (le16_to_cpu(rsp->Command) == SMB2_SESSION_SETUP_HE &&
+           sess->user && !user_guest(sess->user) &&
            rsp->Status == STATUS_SUCCESS)
                return true;
        return false;