put shared code into own mod (common), + apicontext env vars

common/utils.go

@@ -0,0 +1,46 @@
+/*
+Copyright © 2023 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package common
+
+import (
+	"errors"
+	"regexp"
+)
+
+/*
+   Untaint user input, that is: remove all non supported chars.
+
+   wanted is a  regexp matching chars we shall  leave. Everything else
+   will be removed. Eg:
+
+   untainted := Untaint(input, `[^a-zA-Z0-9\-]`)
+
+   Returns a  new string  and an  error if the  input string  has been
+   modified.  It's the  callers  choice  to decide  what  to do  about
+   it. You may  ignore the error and use the  untainted string or bail
+   out.
+*/
+func Untaint(input string, wanted *regexp.Regexp) (string, error) {
+	untainted := wanted.ReplaceAllString(input, "")
+
+	if len(untainted) != len(input) {
+		return untainted, errors.New("Invalid input string!")
+	}
+
+	return untainted, nil
+}