/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.tools.klint.checks;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.klint.detector.api.Category;
import com.android.tools.klint.detector.api.ConstantEvaluator;
import com.android.tools.klint.detector.api.Detector;
import com.android.tools.klint.detector.api.Implementation;
import com.android.tools.klint.detector.api.Issue;
import com.android.tools.klint.detector.api.JavaContext;
import com.android.tools.klint.detector.api.Scope;
import com.android.tools.klint.detector.api.Severity;
import com.google.common.collect.Sets;
import org.jetbrains.uast.UCallExpression;
import org.jetbrains.uast.UElement;
import org.jetbrains.uast.UExpression;
import org.jetbrains.uast.ULiteralExpression;
import org.jetbrains.uast.UMethod;
import org.jetbrains.uast.visitor.UastVisitor;
import java.util.Collections;
import java.util.List;
import java.util.Set;
/**
* Ensures that Cipher.getInstance is not called with AES as the parameter.
*/
public class CipherGetInstanceDetector extends Detector implements Detector.UastScanner {
public static final Issue ISSUE = Issue.create(
"GetInstance", //$NON-NLS-1$
"Cipher.getInstance with ECB",
"`Cipher#getInstance` should not be called with ECB as the cipher mode or without " +
"setting the cipher mode because the default mode on android is ECB, which " +
"is insecure.",
Category.SECURITY,
9,
Severity.WARNING,
new Implementation(
CipherGetInstanceDetector.class,
Scope.JAVA_FILE_SCOPE));
private static final String CIPHER = "javax.crypto.Cipher"; //$NON-NLS-1$
private static final String GET_INSTANCE = "getInstance"; //$NON-NLS-1$
private static final Set<String> ALGORITHM_ONLY =
Sets.newHashSet("AES", "DES", "DESede"); //$NON-NLS-1$
private static final String ECB = "ECB"; //$NON-NLS-1$
// ---- Implements UastScanner ----
@Nullable
@Override
public List<String> getApplicableMethodNames() {
return Collections.singletonList(GET_INSTANCE);
}
@Override
public void visitMethod(@NonNull JavaContext context, @Nullable UastVisitor visitor,
@NonNull UCallExpression node, @NonNull UMethod method) {
if (!context.getEvaluator().isMemberInSubClassOf(method, CIPHER, false)) {
return;
}
List<UExpression> arguments = node.getValueArguments();
if (arguments.size() == 1) {
UExpression expression = arguments.get(0);
Object value = ConstantEvaluator.evaluate(context, expression);
if (value instanceof String) {
checkParameter(context, node, expression, (String)value,
!(expression instanceof ULiteralExpression));
}
}
}
private static void checkParameter(@NonNull JavaContext context,
@NonNull UCallExpression call, @NonNull UElement node, @NonNull String value,
boolean includeValue) {
if (ALGORITHM_ONLY.contains(value)) {
String message = "`Cipher.getInstance` should not be called without setting the"
+ " encryption mode and padding";
context.report(ISSUE, call, context.getUastLocation(node), message);
} else if (value.contains(ECB)) {
String message = "ECB encryption mode should not be used";
if (includeValue) {
message += " (was \"" + value + "\")";
}
context.report(ISSUE, call, context.getUastLocation(node), message);
}
}
}