scsi: target: iscsi: Allow AuthMethod=None

Allow negotiating AuthMethod=None at CSG=0 (Security Negotiation) when
authentication is not required. That is required by the CHAP test in
Windows HLK.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Mike Christie <[e-mail]>
Signed-off-by: Dmitry Bogdanov <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/target/iscsi/iscsi_target_login.c

···
 {
 	struct iscsi_node_attrib *na;
 	struct iscsit_session *sess = conn->sess;
+	struct iscsi_param *param;
 	bool iser = false;
 
 	sess->tpg = conn->tpg;
···
 				conn->param_list);
 
 	na = iscsit_tpg_get_node_attrib(sess);
+
+	/*
+	 * If ACL allows non-authorized access in TPG with CHAP,
+	 * then set None to AuthMethod.
+	 */
+	param = iscsi_find_param_from_key(AUTHMETHOD, conn->param_list);
+	if (param && !strstr(param->value, NONE)) {
+		if (!iscsi_conn_auth_required(conn))
+			if (iscsi_change_param_sprintf(conn, "AuthMethod=%s",
+						       NONE))
+				return -1;
+	}
 
 	/*
 	 * Need to send TargetPortalGroupTag back in first login response

drivers/target/iscsi/iscsi_target_nego.c

···
 	return 0;
 }
 
-static bool iscsi_conn_auth_required(struct iscsit_conn *conn)
+bool iscsi_conn_auth_required(struct iscsit_conn *conn)
 {
 	struct iscsi_node_acl *nacl;
 	struct se_node_acl *se_nacl;

drivers/target/iscsi/iscsi_target_nego.h

···
 extern int iscsi_target_start_negotiation(
 		struct iscsi_login *, struct iscsit_conn *);
 extern void iscsi_target_nego_release(struct iscsit_conn *);
-
+extern bool iscsi_conn_auth_required(struct iscsit_conn *conn);
 #endif /* ISCSI_TARGET_NEGO_H */