fs/cifs: correctly to anonymous authentication for the NTLM(v1) authentication

Only server which map unknown users to guest will allow
access using a non-null NTChallengeResponse.

For Samba it's the "map to guest = bad user" option.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913

Signed-off-by: Stefan Metzmacher <metze@samba.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/sess.c

@@ -781,26 +781,31 @@ sess_auth_ntlm(struct sess_data *sess_data)
 	capabilities = cifs_ssetup_hdr(ses, pSMB);
 
 	pSMB->req_no_secext.Capabilities = cpu_to_le32(capabilities);
-	pSMB->req_no_secext.CaseInsensitivePasswordLength =
-			cpu_to_le16(CIFS_AUTH_RESP_SIZE);
-	pSMB->req_no_secext.CaseSensitivePasswordLength =
-			cpu_to_le16(CIFS_AUTH_RESP_SIZE);
+	if (ses->user_name != NULL) {
+		pSMB->req_no_secext.CaseInsensitivePasswordLength =
+				cpu_to_le16(CIFS_AUTH_RESP_SIZE);
+		pSMB->req_no_secext.CaseSensitivePasswordLength =
+				cpu_to_le16(CIFS_AUTH_RESP_SIZE);
 
-	/* calculate ntlm response and session key */
-	rc = setup_ntlm_response(ses, sess_data->nls_cp);
-	if (rc) {
-		cifs_dbg(VFS, "Error %d during NTLM authentication\n",
-				 rc);
-		goto out;
-	}
+		/* calculate ntlm response and session key */
+		rc = setup_ntlm_response(ses, sess_data->nls_cp);
+		if (rc) {
+			cifs_dbg(VFS, "Error %d during NTLM authentication\n",
+					 rc);
+			goto out;
+		}
 
-	/* copy ntlm response */
-	memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
-			CIFS_AUTH_RESP_SIZE);
-	bcc_ptr += CIFS_AUTH_RESP_SIZE;
-	memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
-			CIFS_AUTH_RESP_SIZE);
-	bcc_ptr += CIFS_AUTH_RESP_SIZE;
+		/* copy ntlm response */
+		memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
+				CIFS_AUTH_RESP_SIZE);
+		bcc_ptr += CIFS_AUTH_RESP_SIZE;
+		memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
+				CIFS_AUTH_RESP_SIZE);
+		bcc_ptr += CIFS_AUTH_RESP_SIZE;
+	} else {
+		pSMB->req_no_secext.CaseInsensitivePasswordLength = 0;
+		pSMB->req_no_secext.CaseSensitivePasswordLength = 0;
+	}
 
 	if (ses->capabilities & CAP_UNICODE) {
 		/* unicode strings must be word aligned */