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Soot extending data flow tracking components for Java
package soot.jimple.infoflow.data;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import soot.Unit;
import soot.jimple.ReturnStmt;
import soot.jimple.ReturnVoidStmt;
import soot.jimple.infoflow.solver.memory.IMemoryManager;
/**
* Memory manager implementation for FlowDroid
*
* @author Steven Arzt
*
*/
public class FlowDroidMemoryManager implements IMemoryManager {
private final Logger logger = LoggerFactory.getLogger(getClass());
/**
* Special class for encapsulating taint abstractions for a full equality check
* including those fields (predecessor, etc.) that are normally left out
*
* @author Steven Arzt
*
*/
private static class AbstractionCacheKey {
private final Abstraction abs;
public AbstractionCacheKey(Abstraction abs) {
this.abs = abs;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * abs.hashCode();
result = prime * result + ((abs.getPredecessor() == null) ? 0 : abs.getPredecessor().hashCode());
result = prime * result + ((abs.getCurrentStmt() == null) ? 0 : abs.getCurrentStmt().hashCode());
result = prime * result
+ ((abs.getCorrespondingCallSite() == null) ? 0 : abs.getCorrespondingCallSite().hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
AbstractionCacheKey other = (AbstractionCacheKey) obj;
if (!abs.equals(other.abs))
return false;
if (abs.getPredecessor() != other.abs.getPredecessor())
return false;
if (abs.getCurrentStmt() != other.abs.getCurrentStmt())
return false;
if (abs.getCorrespondingCallSite() != other.abs.getCorrespondingCallSite())
return false;
return true;
}
}
private ConcurrentMap apCache = new ConcurrentHashMap<>();
private ConcurrentHashMap absCache = new ConcurrentHashMap<>();
private AtomicInteger reuseCounter = new AtomicInteger();
private final boolean tracingEnabled;
private final PathDataErasureMode erasePathData;
private boolean useAbstractionCache = false;
/**
* Supported modes that define which path tracking data shall be erased and
* which shall be kept
*/
public enum PathDataErasureMode {
/**
* Keep all path tracking data.
*/
EraseNothing,
/**
* Keep only those path tracking items that are necessary for context- sensitive
* path reconstruction.
*/
KeepOnlyContextData,
/**
* Erase all path tracking data.
*/
EraseAll
}
/**
* Constructs a new instance of the AccessPathManager class
*/
public FlowDroidMemoryManager() {
this(false, PathDataErasureMode.EraseNothing);
}
/**
* Constructs a new instance of the AccessPathManager class
*
* @param tracingEnabled True if performance tracing data shall be recorded
* @param erasePathData Specifies whether data for tracking paths (current
* statement, corresponding call site) shall be erased.
*/
public FlowDroidMemoryManager(boolean tracingEnabled, PathDataErasureMode erasePathData) {
this.tracingEnabled = tracingEnabled;
this.erasePathData = erasePathData;
logger.info("Initializing FlowDroid memory manager...");
if (this.tracingEnabled)
logger.info("FDMM: Tracing enabled. This may negatively affect performance.");
if (this.erasePathData != PathDataErasureMode.EraseNothing)
logger.info("FDMM: Path data erasure enabled");
}
/**
* Gets the cached equivalent of the given access path
*
* @param ap The access path for which to get the cached equivalent
* @return The cached equivalent of the given access path
*/
private AccessPath getCachedAccessPath(AccessPath ap) {
AccessPath oldAP = apCache.putIfAbsent(ap, ap);
if (oldAP == null)
return ap;
// We can re-use an old access path
if (tracingEnabled && oldAP != ap)
reuseCounter.incrementAndGet();
return oldAP;
}
/**
* Gets a cached equivalent abstraction for the given abstraction if we have
* one, otherwise returns null
*
* @param abs The abstraction for which to perform a cache lookup
* @return The cached abstraction equivalent to the given one of it exists,
* otherwise null
*/
private Abstraction getCachedAbstraction(Abstraction abs) {
Abstraction oldAbs = absCache.putIfAbsent(new AbstractionCacheKey(abs), abs);
if (oldAbs != null && oldAbs != abs)
if (tracingEnabled)
reuseCounter.incrementAndGet();
return oldAbs;
}
/**
* Gets the number of access paths that have been re-used through caching
*
* @return The number of access paths that have been re-used through caching
*/
public int getReuseCount() {
return this.reuseCounter.get();
}
@Override
public Abstraction handleMemoryObject(Abstraction obj) {
return obj;
}
@Override
public Abstraction handleGeneratedMemoryObject(Abstraction input, Abstraction output) {
// We we just pass the same object on, there is nothing to optimize
if (input == output)
return output;
// If the flow function gave us a chain of abstractions, we can
// compact it
Abstraction pred = output.getPredecessor();
if (pred != null && pred != input)
output.setPredecessor(input);
// If the abstraction didn't change at all, we can use the old one
if (input.equals(output)) {
if (output.getCurrentStmt() == null || input.getCurrentStmt() == output.getCurrentStmt())
return input;
if (input.getCurrentStmt() == null) {
synchronized (input) {
if (input.getCurrentStmt() == null) {
input.setCurrentStmt(output.getCurrentStmt());
input.setCorrespondingCallSite(output.getCorrespondingCallSite());
return input;
}
}
}
}
// We check for a cached version of the access path
{
AccessPath newAP = getCachedAccessPath(output.getAccessPath());
output.setAccessPath(newAP);
}
// If an intermediate statement does not change any taint state, skip it. Note
// that we should not do this when we're reconstructing paths or we might lose
// statements along the way.
if (erasePathData != PathDataErasureMode.EraseNothing) {
Abstraction curAbs = output.getPredecessor();
while (curAbs != null && curAbs.getNeighbors() == null) {
Abstraction predPred = curAbs.getPredecessor();
if (predPred != null) {
if (predPred.equals(output))
output = predPred;
}
curAbs = predPred;
}
}
// Erase path data if requested. We may only change the current abstraction,
// because predecessors may already be recorded as neighbors.
erasePathData(output);
// We check for a cached version of the complete abstraction
if (useAbstractionCache) {
Abstraction cachedAbs = getCachedAbstraction(output);
if (cachedAbs != null)
return cachedAbs;
}
return output;
}
/**
* Erases the statements recorded in the given abstraction if the solver has
* been configured to do so
*
* @param output The abstraction to optimize
*/
protected void erasePathData(Abstraction output) {
if (erasePathData != PathDataErasureMode.EraseNothing) {
// Unconditional erasure
if (erasePathData == PathDataErasureMode.EraseAll) {
output.setCurrentStmt(null);
output.setCorrespondingCallSite(null);
}
// Call-to-return edges
else if (erasePathData == PathDataErasureMode.KeepOnlyContextData
&& output.getCorrespondingCallSite() == output.getCurrentStmt()) {
output.setCurrentStmt(null);
output.setCorrespondingCallSite(null);
}
// Normal statements
else if (erasePathData == PathDataErasureMode.KeepOnlyContextData
&& output.getCorrespondingCallSite() == null && output.getCurrentStmt() != null) {
// Lock the abstraction and check again. This is to make sure that no other
// thread has already erased the path data in the meantime and we access null
// objects.
if (output.getCorrespondingCallSite() == null && output.getCurrentStmt() != null
&& !output.getCurrentStmt().containsInvokeExpr()
&& !(output.getCurrentStmt() instanceof ReturnStmt)
&& !(output.getCurrentStmt() instanceof ReturnVoidStmt)) {
output.setCurrentStmt(null);
output.setCorrespondingCallSite(null);
}
}
}
}
/**
* Sets whether the memory manager shall use the abstraction cache
*
* @param useAbstractionCache True if the abstraction cache shall be used,
* otherwise false
*/
public void setUseAbstractionCache(boolean useAbstractionCache) {
this.useAbstractionCache = useAbstractionCache;
}
@Override
public boolean isEssentialJoinPoint(Abstraction abs, Unit relatedCallSite) {
return relatedCallSite != null && erasePathData != PathDataErasureMode.EraseAll;
}
}