1 files changed, 54 insertions, 0 deletions
diff --git a/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.java b/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.java
new file mode 100644
index 00000000..79572aa3
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/widget/KeyInputFilter.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.widget;
+
+import androidx.annotation.Nullable;
+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.
+ */
+
+public class KeyInputFilter implements InputFilter {
+    private static boolean isAllowed(final char c) {
+        return Character.isLetterOrDigit(c) || c == '+' || c == '/';
+    }
+
+    public static InputFilter newInstance() {
+        return new KeyInputFilter();
+    }
+
+    @Nullable
+    @Override
+    public CharSequence filter(final CharSequence source,
+                               final int sStart, final int sEnd,
+                               final Spanned dest,
+                               final int dStart, final int dEnd) {
+        SpannableStringBuilder replacement = null;
+        int rIndex = 0;
+        final int dLength = dest.length();
+        for (int sIndex = sStart; sIndex < sEnd; ++sIndex) {
+            final char c = source.charAt(sIndex);
+            final int 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.getLength() && isAllowed(c)) ||
+                    (dIndex + 1 == Key.Format.BASE64.getLength() && c == '=')) &&
+                    dLength + (sIndex - sStart) < Key.Format.BASE64.getLength()) {
+                ++rIndex;
+            } else {
+                if (replacement == null)
+                    replacement = new SpannableStringBuilder(source, sStart, sEnd);
+                replacement.delete(rIndex, rIndex + 1);
+            }
+        }
+        return replacement;
+    }
+}