findsqlinjection.java

A static analysis tool to find bugs in Java programs

		INVOKEINTERFACE invoke = (INVOKEINTERFACE) ins;

		String methodName = invoke.getMethodName(cpg);
		String interfaceName = invoke.getClassName(cpg);
		if (methodName.startsWith("execute") && interfaceName.equals("java.sql.Statement")) {
			return true;
		}

		return false;
	}

	private boolean isDatabaseSink(Instruction ins, ConstantPoolGen cpg) {
		return isPreparedStatementDatabaseSink(ins, cpg) || isExecuteDatabaseSink(ins, cpg);
	}

	private StringAppendState getStringAppendState(CFG cfg, ConstantPoolGen cpg) throws CFGBuilderException {
		StringAppendState stringAppendState = new StringAppendState();
		String sig = method.getSignature();
		sig = sig.substring(0,sig.indexOf(')'));

		if (sig.indexOf("java/lang/String") >= 0)
			stringAppendState.setSawInitialTaint();
		for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
			Location location = i.next();
			InstructionHandle handle = location.getHandle();
			Instruction ins = handle.getInstruction();
			if (isConstantStringLoad(location, cpg)) {
				stringAppendState = updateStringAppendState(location, cpg, stringAppendState);
			} else if (isStringAppend(ins, cpg)) {
				stringAppendState.setSawAppend(handle);

				Location prevLocation = getPreviousLocation(cfg, location, true);
				if (prevLocation != null && !isSafeValue(prevLocation, cpg))
						stringAppendState.setSawUnsafeAppend(handle);

			} else if (ins instanceof InvokeInstruction) {
				InvokeInstruction inv = (InvokeInstruction) ins;
				String sig1 = inv.getSignature(cpg);
				String sig2 = sig1.substring(sig1.indexOf(')'));

				if (sig2.indexOf("java/lang/String") >= 0) {
					String methodName = inv.getMethodName(cpg);
					String className = inv.getClassName(cpg);
					if (methodName.equals("valueOf") && className.equals("java.lang.String") && sig1.equals("(Ljava/lang/Object;)Ljava/lang/String;")) {
						try {
						TypeDataflow typeDataflow = classContext.getTypeDataflow(method);
						TypeFrame frame = typeDataflow.getFactAtLocation(location);
						if (!frame.isValid()) {
							// This basic block is probably dead
							continue;
						}
						Type operandType = frame.getTopValue();
						if (operandType.equals(TopType.instance())) {
							// unreachable
							continue;
						}
						String sig3 = operandType.getSignature();
						if (!sig3.equals("Ljava/lang/String;"))
							stringAppendState.setSawTaint(handle);
						} catch (CheckedAnalysisException e) {
							stringAppendState.setSawTaint(handle);
						}
					} else if (className.startsWith("java.lang.String") || className.equals("java.lang.Long") 
							|| className.equals("java.lang.Integer") || className.equals("java.lang.Float") || className.equals("java.lang.Double")
							|| className.equals("java.lang.Short")  || className.equals("java.lang.Byte") || className.equals("java.lang.Character")) {
						// ignore it
						assert true;
					} else if (methodName.startsWith("to") && methodName.endsWith("String") && methodName.length() > 8) {
						// ignore it
						assert true;
					} else  stringAppendState.setSawTaint(handle);
				}
			} else if (ins instanceof GETFIELD) {
				GETFIELD getfield = (GETFIELD) ins;
				String sig2 = getfield.getSignature(cpg);
				if (sig2.indexOf("java/lang/String") >= 0)
					stringAppendState.setSawTaint(handle);
			}
		}

		return stringAppendState;
	}

	private boolean isSafeValue(Location location, ConstantPoolGen cpg) throws CFGBuilderException {
		Instruction prevIns = location.getHandle().getInstruction();
		if (prevIns instanceof LDC || prevIns instanceof GETSTATIC)
			return true;
		if (prevIns instanceof InvokeInstruction) {
			String methodName = ((InvokeInstruction) prevIns).getMethodName(cpg);
			if (methodName.startsWith("to") && methodName.endsWith("String") && methodName.length() > 8)
				return true;
		}
		if (prevIns instanceof AALOAD) {
			CFG cfg = classContext.getCFG(method);

			Location prev = getPreviousLocation(cfg, location, true);
			if (prev != null) {
				Location prev2 = getPreviousLocation(cfg, prev, true);
				if (prev2 != null && prev2.getHandle().getInstruction() instanceof GETSTATIC) {
					GETSTATIC getStatic = (GETSTATIC) prev2.getHandle().getInstruction();
					if (getStatic.getSignature(cpg).equals("[Ljava/lang/String;"))
						return true;
				}               
			}          
		}
		return false;
	}

	private @CheckForNull
	InstructionHandle getPreviousInstruction(InstructionHandle handle, boolean skipNops) {
		while (handle.getPrev() != null) {
			handle = handle.getPrev();
			Instruction prevIns = handle.getInstruction();
			if (!(prevIns instanceof NOP && skipNops)) {
				return handle;
			}
		}
		return null;
	}

	private @CheckForNull
	Location getPreviousLocation(CFG cfg, Location startLocation, boolean skipNops) {
		Location loc = startLocation;
		InstructionHandle prev = getPreviousInstruction(loc.getHandle(), skipNops);
		if (prev != null)
			return new Location(prev, loc.getBasicBlock());
		BasicBlock block = loc.getBasicBlock();
		while (true) {
			block = cfg.getPredecessorWithEdgeType(block, EdgeTypes.FALL_THROUGH_EDGE);
			if (block == null)
				return null;
			InstructionHandle lastInstruction = block.getLastInstruction();
			if (lastInstruction != null)
				return new Location(lastInstruction, block);
		}
	}

	private @CheckForNull
	InstructionHandle getPreviousInstruction(CFG cfg, Location startLocation, boolean skipNops) {
		Location loc = startLocation;
		InstructionHandle prev = getPreviousInstruction(loc.getHandle(), skipNops);
		if (prev != null)
			return prev;
		BasicBlock block = loc.getBasicBlock();
		while (true) {
			block = cfg.getPredecessorWithEdgeType(block, EdgeTypes.FALL_THROUGH_EDGE);
			if (block == null)
				return null;
			InstructionHandle lastInstruction = block.getLastInstruction();
			if (lastInstruction != null)
				return lastInstruction;
		}
	}

	private BugInstance generateBugInstance(JavaClass javaClass, MethodGen methodGen, InstructionHandle handle,
			StringAppendState stringAppendState) {
		Instruction instruction = handle.getInstruction();
		ConstantPoolGen cpg = methodGen.getConstantPool();
		int priority = LOW_PRIORITY;
		if (stringAppendState.getSawAppend(handle)) {
			if (stringAppendState.getSawOpenQuote(handle) && stringAppendState.getSawCloseQuote(handle)) {
				priority = HIGH_PRIORITY;
			} else if (stringAppendState.getSawComma(handle)) {
				priority = NORMAL_PRIORITY;
			}

			if (!stringAppendState.getSawUnsafeAppend(handle)) {
				priority += 2;
			}
			else if (!stringAppendState.getSawTaint(handle)) {
				priority ++;
			}
		}

		String description = "";
		if (isExecuteDatabaseSink(instruction, cpg)) {
			description = "SQL_NONCONSTANT_STRING_PASSED_TO_EXECUTE";
		} else if (isPreparedStatementDatabaseSink(instruction, cpg)) {
			description = "SQL_PREPARED_STATEMENT_GENERATED_FROM_NONCONSTANT_STRING";
		}

		BugInstance bug = new BugInstance(this, description, priority);
		bug.addClassAndMethod(methodGen, javaClass.getSourceFileName());

		return bug;
	}

	Method method;
	ClassContext classContext;
	private void analyzeMethod(ClassContext classContext, Method method) throws DataflowAnalysisException,
			CFGBuilderException {
		JavaClass javaClass = classContext.getJavaClass();
		this.method = method;
		this.classContext = classContext;
		MethodGen methodGen = classContext.getMethodGen(method);
		if (methodGen == null)
			return;

		ConstantPoolGen cpg = methodGen.getConstantPool();
		CFG cfg = classContext.getCFG(method);

		StringAppendState stringAppendState = getStringAppendState(cfg, cpg);

		ConstantDataflow dataflow = classContext.getConstantDataflow(method);
		for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
			Location location = i.next();
			Instruction ins = location.getHandle().getInstruction();
			if (isDatabaseSink(ins, cpg)) {
				ConstantFrame frame = dataflow.getFactAtLocation(location);
				Constant value = frame.getStackValue(0);

				if (!value.isConstantString()) {
					// TODO: verify it's the same string represented by
					// stringAppendState
					// FIXME: will false positive on const/static strings
					// returns by methods
					Location prev = getPreviousLocation(cfg, location, true);
					if (prev == null || !isSafeValue(prev, cpg)) {
						BugInstance bug = generateBugInstance(javaClass, methodGen, location.getHandle(),
								stringAppendState);
						bug.addSourceLine(classContext, methodGen, javaClass.getSourceFileName(), location.getHandle());
						bugReporter.reportBug(bug);
					}
				}
			}
		}
	}

	public void report() {
	}
}

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