com.android.tools.lint.checks.SecureRandomDetector Maven / Gradle / Ivy
/*
* Copyright (C) 2012 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.lint.checks;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.client.api.JavaEvaluator;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.ConstantEvaluator;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Detector.JavaPsiScanner;
import com.android.tools.lint.detector.api.Implementation;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.JavaContext;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import com.android.tools.lint.detector.api.TypeEvaluator;
import com.intellij.psi.JavaElementVisitor;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiExpression;
import com.intellij.psi.PsiMethod;
import com.intellij.psi.PsiMethodCallExpression;
import com.intellij.psi.PsiType;
import java.util.Collections;
import java.util.List;
/**
* Checks for hardcoded seeds with random numbers.
*/
public class SecureRandomDetector extends Detector implements JavaPsiScanner {
/** Unregistered activities and services */
public static final Issue ISSUE = Issue.create(
"SecureRandom", //$NON-NLS-1$
"Using a fixed seed with `SecureRandom`",
"Specifying a fixed seed will cause the instance to return a predictable sequence " +
"of numbers. This may be useful for testing but it is not appropriate for secure use.",
Category.SECURITY,
9,
Severity.WARNING,
new Implementation(
SecureRandomDetector.class,
Scope.JAVA_FILE_SCOPE))
.addMoreInfo("http://developer.android.com/reference/java/security/SecureRandom.html");
private static final String SET_SEED = "setSeed"; //$NON-NLS-1$
public static final String JAVA_SECURITY_SECURE_RANDOM = "java.security.SecureRandom";
public static final String JAVA_UTIL_RANDOM = "java.util.Random";
/** Constructs a new {@link SecureRandomDetector} */
public SecureRandomDetector() {
}
// ---- Implements JavaScanner ----
@Nullable
@Override
public List getApplicableMethodNames() {
return Collections.singletonList(SET_SEED);
}
@Override
public void visitMethod(@NonNull JavaContext context, @Nullable JavaElementVisitor visitor,
@NonNull PsiMethodCallExpression call, @NonNull PsiMethod method) {
PsiExpression[] arguments = call.getArgumentList().getExpressions();
if (arguments.length == 0) {
return;
}
PsiExpression seedArgument = arguments[0];
JavaEvaluator evaluator = context.getEvaluator();
if (evaluator.isMemberInClass(method, JAVA_SECURITY_SECURE_RANDOM)
|| evaluator.isMemberInSubClassOf(method, JAVA_UTIL_RANDOM, false)
&& isSecureRandomReceiver(context, call)) {
// Called with a fixed seed?
Object seed = ConstantEvaluator.evaluate(context, seedArgument);
//noinspection VariableNotUsedInsideIf
if (seed != null) {
context.report(ISSUE, call, context.getLocation(call),
"Do not call `setSeed()` on a `SecureRandom` with a fixed seed: " +
"it is not secure. Use `getSeed()`.");
} else {
// Called with a simple System.currentTimeMillis() seed or something like that?
PsiElement resolvedArgument = evaluator.resolve(seedArgument);
if (resolvedArgument instanceof PsiMethod) {
PsiMethod seedMethod = (PsiMethod) resolvedArgument;
String methodName = seedMethod.getName();
if (methodName.equals("currentTimeMillis")
|| methodName.equals("nanoTime")) {
context.report(ISSUE, call, context.getLocation(call),
"It is dangerous to seed `SecureRandom` with the current "
+ "time because that value is more predictable to "
+ "an attacker than the default seed.");
}
}
}
}
}
/**
* Returns true if the given invocation is assigned a SecureRandom type
*/
private static boolean isSecureRandomReceiver(
@NonNull JavaContext context,
@NonNull PsiMethodCallExpression call) {
PsiElement operand = call.getMethodExpression().getQualifier();
return operand != null && isSecureRandomType(context, operand);
}
/**
* Returns true if the node evaluates to an instance of type SecureRandom
*/
private static boolean isSecureRandomType(
@NonNull JavaContext context,
@NonNull PsiElement node) {
PsiType type = TypeEvaluator.evaluate(context, node);
return type != null && JAVA_SECURITY_SECURE_RANDOM.equals(type.getCanonicalText());
}
}