solidity/libsolidity/formal/CHC.cpp
2019-09-13 12:40:53 +02:00

683 lines
18 KiB
C++

/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libsolidity/formal/CHC.h>
#ifdef HAVE_Z3
#include <libsolidity/formal/Z3CHCInterface.h>
#endif
#include <libsolidity/formal/SymbolicTypes.h>
#include <libsolidity/ast/TypeProvider.h>
using namespace std;
using namespace dev;
using namespace langutil;
using namespace dev::solidity;
CHC::CHC(smt::EncodingContext& _context, ErrorReporter& _errorReporter):
SMTEncoder(_context),
#ifdef HAVE_Z3
m_interface(make_shared<smt::Z3CHCInterface>()),
#endif
m_outerErrorReporter(_errorReporter)
{
}
void CHC::analyze(SourceUnit const& _source)
{
solAssert(_source.annotation().experimentalFeatures.count(ExperimentalFeature::SMTChecker), "");
#ifdef HAVE_Z3
auto z3Interface = dynamic_pointer_cast<smt::Z3CHCInterface>(m_interface);
solAssert(z3Interface, "");
m_context.setSolver(z3Interface->z3Interface());
m_context.clear();
m_context.setAssertionAccumulation(false);
m_variableUsage.setFunctionInlining(false);
_source.accept(*this);
#endif
}
bool CHC::visit(ContractDefinition const& _contract)
{
if (!shouldVisit(_contract))
return false;
reset();
if (!SMTEncoder::visit(_contract))
return false;
m_stateVariables = _contract.stateVariablesIncludingInherited();
for (auto const& var: m_stateVariables)
// SMT solvers do not support function types as arguments.
if (var->type()->category() == Type::Category::Function)
m_stateSorts.push_back(make_shared<smt::Sort>(smt::Kind::Int));
else
m_stateSorts.push_back(smt::smtSort(*var->type()));
clearIndices();
string interfaceName = "interface_" + _contract.name() + "_" + to_string(_contract.id());
m_interfacePredicate = createSymbolicBlock(interfaceSort(), interfaceName);
// TODO create static instances for Bool/Int sorts in SolverInterface.
auto boolSort = make_shared<smt::Sort>(smt::Kind::Bool);
auto errorFunctionSort = make_shared<smt::FunctionSort>(
vector<smt::SortPointer>(),
boolSort
);
m_errorPredicate = createSymbolicBlock(errorFunctionSort, "error");
// If the contract has a constructor it is handled as a function.
// Otherwise we zero-initialize all state vars.
// TODO take into account state vars init values.
if (!_contract.constructor())
{
string constructorName = "constructor_" + _contract.name() + "_" + to_string(_contract.id());
m_constructorPredicate = createSymbolicBlock(constructorSort(), constructorName);
smt::Expression constructorPred = (*m_constructorPredicate)({});
addRule(constructorPred, constructorName);
for (auto const& var: m_stateVariables)
{
auto const& symbVar = m_context.variable(*var);
symbVar->increaseIndex();
m_interface->declareVariable(symbVar->currentName(), *symbVar->sort());
m_context.setZeroValue(*symbVar);
}
connectBlocks(constructorPred, interface());
}
return true;
}
void CHC::endVisit(ContractDefinition const& _contract)
{
if (!shouldVisit(_contract))
return;
for (unsigned i = 0; i < m_verificationTargets.size(); ++i)
{
auto const& target = m_verificationTargets.at(i);
auto errorAppl = error(i + 1);
if (query(errorAppl, target->location()))
m_safeAssertions.insert(target);
}
SMTEncoder::endVisit(_contract);
}
bool CHC::visit(FunctionDefinition const& _function)
{
if (!shouldVisit(_function))
return false;
solAssert(!m_currentFunction, "Inlining internal function calls not yet implemented");
m_currentFunction = &_function;
initFunction(_function);
// Store the constraints related to variable initialization.
smt::Expression const& initAssertions = m_context.assertions();
m_context.pushSolver();
solAssert(m_functionBlocks == 0, "");
createBlock(m_currentFunction);
createBlock(&m_currentFunction->body(), "block_");
auto functionPred = predicate(m_currentFunction);
auto bodyPred = predicate(&m_currentFunction->body());
connectBlocks(interface(), functionPred);
connectBlocks(functionPred, bodyPred);
m_context.popSolver();
pushBlock(&m_currentFunction->body());
// We need to re-add the constraints that were created for initialization of variables.
m_context.addAssertion(initAssertions);
SMTEncoder::visit(*m_currentFunction);
return false;
}
void CHC::endVisit(FunctionDefinition const& _function)
{
if (!shouldVisit(_function))
return;
solAssert(m_currentFunction == &_function, "Inlining internal function calls not yet implemented");
// Function Exit block.
createBlock(m_currentFunction);
connectBlocks(m_path.back(), predicate(&_function));
// Rule FunctionExit -> Interface, uses no constraints.
clearIndices();
m_context.pushSolver();
connectBlocks(predicate(&_function), interface());
m_context.popSolver();
m_currentFunction = nullptr;
solAssert(m_path.size() == m_functionBlocks, "");
while (m_functionBlocks > 0)
popBlock();
solAssert(m_path.empty(), "");
SMTEncoder::endVisit(_function);
}
bool CHC::visit(IfStatement const& _if)
{
solAssert(m_currentFunction, "");
bool unknownFunctionCallWasSeen = m_unknownFunctionCallSeen;
m_unknownFunctionCallSeen = false;
SMTEncoder::visit(_if);
if (m_unknownFunctionCallSeen)
eraseKnowledge();
m_unknownFunctionCallSeen = unknownFunctionCallWasSeen;
return false;
}
bool CHC::visit(WhileStatement const& _while)
{
bool unknownFunctionCallWasSeen = m_unknownFunctionCallSeen;
m_unknownFunctionCallSeen = false;
solAssert(m_currentFunction, "");
if (_while.isDoWhile())
_while.body().accept(*this);
visitLoop(
_while,
&_while.condition(),
_while.body(),
nullptr
);
if (m_unknownFunctionCallSeen)
eraseKnowledge();
m_unknownFunctionCallSeen = unknownFunctionCallWasSeen;
return false;
}
bool CHC::visit(ForStatement const& _for)
{
bool unknownFunctionCallWasSeen = m_unknownFunctionCallSeen;
m_unknownFunctionCallSeen = false;
solAssert(m_currentFunction, "");
if (auto init = _for.initializationExpression())
init->accept(*this);
visitLoop(
_for,
_for.condition(),
_for.body(),
_for.loopExpression()
);
if (m_unknownFunctionCallSeen)
eraseKnowledge();
m_unknownFunctionCallSeen = unknownFunctionCallWasSeen;
return false;
}
void CHC::endVisit(FunctionCall const& _funCall)
{
solAssert(_funCall.annotation().kind != FunctionCallKind::Unset, "");
if (_funCall.annotation().kind != FunctionCallKind::FunctionCall)
{
SMTEncoder::endVisit(_funCall);
return;
}
FunctionType const& funType = dynamic_cast<FunctionType const&>(*_funCall.expression().annotation().type);
switch (funType.kind())
{
case FunctionType::Kind::Assert:
visitAssert(_funCall);
SMTEncoder::endVisit(_funCall);
break;
case FunctionType::Kind::Internal:
case FunctionType::Kind::External:
case FunctionType::Kind::DelegateCall:
case FunctionType::Kind::BareCall:
case FunctionType::Kind::BareCallCode:
case FunctionType::Kind::BareDelegateCall:
case FunctionType::Kind::BareStaticCall:
case FunctionType::Kind::Creation:
case FunctionType::Kind::KECCAK256:
case FunctionType::Kind::ECRecover:
case FunctionType::Kind::SHA256:
case FunctionType::Kind::RIPEMD160:
case FunctionType::Kind::BlockHash:
case FunctionType::Kind::AddMod:
case FunctionType::Kind::MulMod:
SMTEncoder::endVisit(_funCall);
unknownFunctionCall(_funCall);
break;
default:
SMTEncoder::endVisit(_funCall);
break;
}
createReturnedExpressions(_funCall);
}
void CHC::endVisit(Break const&)
{
solAssert(m_breakDest, "");
m_breakSeen = true;
}
void CHC::endVisit(Continue const&)
{
solAssert(m_continueDest, "");
m_continueSeen = true;
}
void CHC::visitAssert(FunctionCall const& _funCall)
{
auto const& args = _funCall.arguments();
solAssert(args.size() == 1, "");
solAssert(args.front()->annotation().type->category() == Type::Category::Bool, "");
solAssert(!m_path.empty(), "");
createErrorBlock();
smt::Expression assertNeg = !(m_context.expression(*args.front())->currentValue());
connectBlocks(m_path.back(), error(), currentPathConditions() && assertNeg);
m_verificationTargets.push_back(&_funCall);
}
void CHC::unknownFunctionCall(FunctionCall const&)
{
/// Function calls are not handled at the moment,
/// so always erase knowledge.
/// TODO remove when function calls get predicates/blocks.
eraseKnowledge();
/// Used to erase outer scope knowledge in loops and ifs.
/// TODO remove when function calls get predicates/blocks.
m_unknownFunctionCallSeen = true;
}
void CHC::visitLoop(
BreakableStatement const& _loop,
Expression const* _condition,
Statement const& _body,
ASTNode const* _postLoop
)
{
bool breakWasSeen = m_breakSeen;
bool continueWasSeen = m_continueSeen;
m_breakSeen = false;
m_continueSeen = false;
solAssert(m_currentFunction, "");
auto const& functionBody = m_currentFunction->body();
createBlock(&_loop, "loop_header_");
createBlock(&_body, "loop_body_");
createBlock(&functionBody, "block_");
connectBlocks(m_path.back(), predicate(&_loop));
// We need to save the next block here because new blocks
// might be created inside the loop body.
// This will be m_path.back() in the end of this function.
pushBlock(&functionBody);
smt::Expression loopHeader = predicate(&_loop);
pushBlock(&_loop);
if (_condition)
_condition->accept(*this);
auto condition = _condition ? expr(*_condition) : smt::Expression(true);
connectBlocks(loopHeader, predicate(&_body), condition);
connectBlocks(loopHeader, predicate(&functionBody), !condition);
// Loop body visit.
pushBlock(&_body);
m_breakDest = &functionBody;
m_continueDest = _postLoop ? _postLoop : &_loop;
auto functionBlocks = m_functionBlocks;
_body.accept(*this);
if (_postLoop)
{
createBlock(_postLoop, "loop_post_");
connectBlocks(m_path.back(), predicate(_postLoop));
pushBlock(_postLoop);
_postLoop->accept(*this);
}
// Back edge.
connectBlocks(m_path.back(), predicate(&_loop));
// Pop all function blocks created by nested inner loops
// to adjust the assertion context.
for (unsigned i = m_functionBlocks; i > functionBlocks; --i)
popBlock();
m_functionBlocks = functionBlocks;
// Loop body
popBlock();
// Loop header
popBlock();
// New function block starts with indices = 0
clearIndices();
if (m_breakSeen || m_continueSeen)
{
eraseKnowledge();
m_context.resetVariables([](VariableDeclaration const&) { return true; });
}
m_breakSeen = breakWasSeen;
m_continueSeen = continueWasSeen;
}
void CHC::reset()
{
m_stateSorts.clear();
m_stateVariables.clear();
m_verificationTargets.clear();
m_safeAssertions.clear();
m_unknownFunctionCallSeen = false;
m_breakSeen = false;
m_continueSeen = false;
}
void CHC::eraseKnowledge()
{
resetStateVariables();
m_context.resetVariables([&](VariableDeclaration const& _variable) { return _variable.hasReferenceOrMappingType(); });
}
bool CHC::shouldVisit(ContractDefinition const& _contract) const
{
if (
_contract.isLibrary() ||
_contract.isInterface()
)
return false;
return true;
}
bool CHC::shouldVisit(FunctionDefinition const& _function) const
{
if (
_function.isPublic() &&
_function.isImplemented() &&
!_function.isConstructor()
)
return true;
return false;
}
void CHC::pushBlock(ASTNode const* _node)
{
clearIndices();
m_context.pushSolver();
m_path.push_back(predicate(_node));
++m_functionBlocks;
}
void CHC::popBlock()
{
m_context.popSolver();
m_path.pop_back();
--m_functionBlocks;
}
smt::SortPointer CHC::constructorSort()
{
solAssert(m_currentContract, "");
auto boolSort = make_shared<smt::Sort>(smt::Kind::Bool);
if (!m_currentContract->constructor())
return make_shared<smt::FunctionSort>(vector<smt::SortPointer>{}, boolSort);
return sort(*m_currentContract->constructor());
}
smt::SortPointer CHC::interfaceSort()
{
auto boolSort = make_shared<smt::Sort>(smt::Kind::Bool);
return make_shared<smt::FunctionSort>(
m_stateSorts,
boolSort
);
}
smt::SortPointer CHC::sort(FunctionDefinition const& _function)
{
if (m_nodeSorts.count(&_function))
return m_nodeSorts.at(&_function);
auto boolSort = make_shared<smt::Sort>(smt::Kind::Bool);
vector<smt::SortPointer> varSorts;
for (auto const& var: _function.parameters() + _function.returnParameters())
varSorts.push_back(smt::smtSort(*var->type()));
auto sort = make_shared<smt::FunctionSort>(
m_stateSorts + varSorts,
boolSort
);
return m_nodeSorts[&_function] = move(sort);
}
smt::SortPointer CHC::sort(ASTNode const* _node)
{
if (m_nodeSorts.count(_node))
return m_nodeSorts.at(_node);
if (auto funDef = dynamic_cast<FunctionDefinition const*>(_node))
return sort(*funDef);
auto fSort = dynamic_pointer_cast<smt::FunctionSort>(sort(*m_currentFunction));
solAssert(fSort, "");
auto boolSort = make_shared<smt::Sort>(smt::Kind::Bool);
vector<smt::SortPointer> varSorts;
for (auto const& var: m_currentFunction->localVariables())
varSorts.push_back(smt::smtSort(*var->type()));
auto functionBodySort = make_shared<smt::FunctionSort>(
fSort->domain + varSorts,
boolSort
);
return m_nodeSorts[_node] = move(functionBodySort);
}
unique_ptr<smt::SymbolicFunctionVariable> CHC::createSymbolicBlock(smt::SortPointer _sort, string const& _name)
{
auto block = make_unique<smt::SymbolicFunctionVariable>(
_sort,
_name,
m_context
);
m_interface->registerRelation(block->currentValue());
return block;
}
smt::Expression CHC::constructor()
{
solAssert(m_currentContract, "");
if (!m_currentContract->constructor())
return (*m_constructorPredicate)({});
vector<smt::Expression> paramExprs;
for (auto const& var: m_currentContract->constructor()->parameters())
paramExprs.push_back(m_context.variable(*var)->currentValue());
return (*m_constructorPredicate)(paramExprs);
}
smt::Expression CHC::interface()
{
vector<smt::Expression> paramExprs;
for (auto const& var: m_stateVariables)
paramExprs.push_back(m_context.variable(*var)->currentValue());
return (*m_interfacePredicate)(paramExprs);
}
smt::Expression CHC::error()
{
return (*m_errorPredicate)({});
}
smt::Expression CHC::error(unsigned _idx)
{
return m_errorPredicate->valueAtIndex(_idx)({});
}
void CHC::createBlock(ASTNode const* _node, string const& _prefix)
{
if (m_predicates.count(_node))
{
m_predicates.at(_node)->increaseIndex();
m_interface->registerRelation(m_predicates.at(_node)->currentValue());
}
else
m_predicates[_node] = createSymbolicBlock(sort(_node), _prefix + predicateName(_node));
}
void CHC::createErrorBlock()
{
solAssert(m_errorPredicate, "");
m_errorPredicate->increaseIndex();
m_interface->registerRelation(m_errorPredicate->currentValue());
}
void CHC::connectBlocks(smt::Expression const& _from, smt::Expression const& _to, smt::Expression const& _constraints)
{
smt::Expression edge = smt::Expression::implies(
_from && m_context.assertions() && _constraints,
_to
);
addRule(edge, _from.name + "_to_" + _to.name);
}
vector<smt::Expression> CHC::currentFunctionVariables()
{
solAssert(m_currentFunction, "");
vector<smt::Expression> paramExprs;
for (auto const& var: m_stateVariables)
paramExprs.push_back(m_context.variable(*var)->currentValue());
for (auto const& var: m_currentFunction->parameters() + m_currentFunction->returnParameters())
paramExprs.push_back(m_context.variable(*var)->currentValue());
return paramExprs;
}
vector<smt::Expression> CHC::currentBlockVariables()
{
solAssert(m_currentFunction, "");
vector<smt::Expression> paramExprs;
for (auto const& var: m_currentFunction->localVariables())
paramExprs.push_back(m_context.variable(*var)->currentValue());
return currentFunctionVariables() + paramExprs;
}
void CHC::clearIndices()
{
for (auto const& var: m_stateVariables)
m_context.variable(*var)->resetIndex();
if (m_currentFunction)
{
for (auto const& var: m_currentFunction->parameters() + m_currentFunction->returnParameters())
m_context.variable(*var)->resetIndex();
for (auto const& var: m_currentFunction->localVariables())
m_context.variable(*var)->resetIndex();
}
}
string CHC::predicateName(ASTNode const* _node)
{
string prefix;
if (auto funDef = dynamic_cast<FunctionDefinition const*>(_node))
{
prefix = funDef->isConstructor() ?
"constructor" :
funDef->isFallback() ?
"fallback" :
"function_" + funDef->name();
prefix += "_";
}
return prefix + to_string(_node->id());
}
smt::Expression CHC::predicate(ASTNode const* _node)
{
if (dynamic_cast<FunctionDefinition const*>(_node))
return (*m_predicates.at(_node))(currentFunctionVariables());
return (*m_predicates.at(_node))(currentBlockVariables());
}
void CHC::addRule(smt::Expression const& _rule, string const& _ruleName)
{
m_interface->addRule(_rule, _ruleName);
}
bool CHC::query(smt::Expression const& _query, langutil::SourceLocation const& _location)
{
smt::CheckResult result;
vector<string> values;
tie(result, values) = m_interface->query(_query);
switch (result)
{
case smt::CheckResult::SATISFIABLE:
break;
case smt::CheckResult::UNSATISFIABLE:
return true;
case smt::CheckResult::UNKNOWN:
break;
case smt::CheckResult::CONFLICTING:
m_outerErrorReporter.warning(_location, "At least two SMT solvers provided conflicting answers. Results might not be sound.");
break;
case smt::CheckResult::ERROR:
m_outerErrorReporter.warning(_location, "Error trying to invoke SMT solver.");
break;
}
return false;
}