1 files changed, 49 insertions, 0 deletions
diff --git a/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.kt b/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.kt
new file mode 100644
index 00000000..8c822dcb
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.kt
@@ -0,0 +1,49 @@
+/*
+ * Copyright © 2017-2023 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.widget
+
+import android.text.InputFilter
+import android.text.SpannableStringBuilder
+import android.text.Spanned
+import com.wireguard.crypto.Key
+
+/**
+ * InputFilter for entering WireGuard private/public keys encoded with base64.
+ */
+class KeyInputFilter : InputFilter {
+    override fun filter(
+        source: CharSequence,
+        sStart: Int, sEnd: Int,
+        dest: Spanned,
+        dStart: Int, dEnd: Int
+    ): CharSequence? {
+        var replacement: SpannableStringBuilder? = null
+        var rIndex = 0
+        val dLength = dest.length
+        for (sIndex in sStart until sEnd) {
+            val c = source[sIndex]
+            val dIndex = dStart + (sIndex - sStart)
+            // Restrict characters to the base64 character set.
+            // Ensure adding this character does not push the length over the limit.
+            if ((dIndex + 1 < Key.Format.BASE64.length && isAllowed(c) ||
+                        dIndex + 1 == Key.Format.BASE64.length && c == '=') &&
+                dLength + (sIndex - sStart) < Key.Format.BASE64.length
+            ) {
+                ++rIndex
+            } else {
+                if (replacement == null) replacement = SpannableStringBuilder(source, sStart, sEnd)
+                replacement.delete(rIndex, rIndex + 1)
+            }
+        }
+        return replacement
+    }
+
+    companion object {
+        private fun isAllowed(c: Char) = Character.isLetterOrDigit(c) || c == '+' || c == '/'
+
+        @JvmStatic
+        fun newInstance() = KeyInputFilter()
+    }
+}