EditFragment: Input filters for config name and private key

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/ConfigEditFragment.java

@@ -2,6 +2,10 @@ package com.wireguard.android;
 
 import android.content.Context;
 import android.os.Bundle;
+import android.text.InputFilter;
+import android.text.LoginFilter;
+import android.text.SpannableStringBuilder;
+import android.text.Spanned;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuInflater;
@@ -9,9 +13,11 @@ import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.inputmethod.InputMethodManager;
+import android.widget.EditText;
 
 import com.wireguard.android.databinding.ConfigEditFragmentBinding;
 import com.wireguard.config.Config;
+import com.wireguard.crypto.KeyEncoding;
 
 /**
  * Fragment for editing a WireGuard configuration.
@@ -41,6 +47,50 @@ public class ConfigEditFragment extends BaseConfigFragment {
                              final Bundle savedInstanceState) {
         final ConfigEditFragmentBinding binding =
                 ConfigEditFragmentBinding.inflate(inflater, parent, false);
+        final EditText configNameText = binding.getRoot().findViewById(R.id.config_name_text);
+        configNameText.setFilters(new InputFilter[]{
+                new InputFilter.LengthFilter(16),
+                new LoginFilter.UsernameFilterGeneric() {
+                    @Override
+                    public boolean isAllowed(final char c) {
+                        return Character.isLetterOrDigit(c) || "_=+.-".indexOf(c) != -1;
+                    }
+                }
+        });
+        final EditText privateKeyText = binding.getRoot().findViewById(R.id.private_key_text);
+        privateKeyText.setFilters(new InputFilter[]{
+                new InputFilter() {
+                    @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 < KeyEncoding.KEY_LENGTH_BASE64 && isAllowed(c)) ||
+                                    (dIndex + 1 == KeyEncoding.KEY_LENGTH_BASE64 && c == '=')) &&
+                                    dLength + (sIndex - sStart) < KeyEncoding.KEY_LENGTH_BASE64) {
+                                ++rIndex;
+                            } else {
+                                if (replacement == null)
+                                    replacement = new SpannableStringBuilder(source, sStart, sEnd);
+                                replacement.delete(rIndex, rIndex + 1);
+                            }
+                        }
+                        return replacement;
+                    }
+
+                    private boolean isAllowed(final char c) {
+                        return Character.isLetterOrDigit(c) || c == '+' || c == '/';
+                    }
+                }
+        });
         binding.setConfig(localConfig);
         return binding.getRoot();
     }