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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
#include <stddef.h>
#include <stdint.h>
#include <limits>
#include <ostream>
#include "base/check.h"
#include "base/memory/raw_ptr.h"
#include "base/notreached.h"
#include "sandbox/linux/bpf_dsl/bpf_dsl_impl.h"
#include "sandbox/linux/bpf_dsl/errorcode.h"
#include "sandbox/linux/bpf_dsl/policy_compiler.h"
#include "sandbox/linux/system_headers/linux_seccomp.h"
namespace sandbox {
namespace bpf_dsl {
namespace {
class ReturnResultExprImpl : public internal::ResultExprImpl {
public:
explicit ReturnResultExprImpl(uint32_t ret) : ret_(ret) {}
ReturnResultExprImpl(const ReturnResultExprImpl&) = delete;
ReturnResultExprImpl& operator=(const ReturnResultExprImpl&) = delete;
~ReturnResultExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc) const override {
return pc->Return(ret_);
}
bool IsAllow() const override { return IsAction(SECCOMP_RET_ALLOW); }
bool IsDeny() const override {
return IsAction(SECCOMP_RET_ERRNO) || IsAction(SECCOMP_RET_KILL) ||
IsAction(SECCOMP_RET_USER_NOTIF);
}
private:
bool IsAction(uint32_t action) const {
return (ret_ & SECCOMP_RET_ACTION) == action;
}
uint32_t ret_;
};
class TrapResultExprImpl : public internal::ResultExprImpl {
public:
TrapResultExprImpl(TrapRegistry::TrapFnc func, const void* arg, bool safe)
: handler_(func, arg, safe) {}
TrapResultExprImpl(const TrapResultExprImpl&) = delete;
TrapResultExprImpl& operator=(const TrapResultExprImpl&) = delete;
~TrapResultExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc) const override {
return pc->Trap(handler_);
}
bool HasUnsafeTraps() const override { return !handler_.safe; }
bool IsDeny() const override { return true; }
private:
TrapRegistry::Handler handler_;
};
class IfThenResultExprImpl : public internal::ResultExprImpl {
public:
IfThenResultExprImpl(BoolExpr cond,
ResultExpr then_result,
ResultExpr else_result)
: cond_(std::move(cond)),
then_result_(std::move(then_result)),
else_result_(std::move(else_result)) {}
IfThenResultExprImpl(const IfThenResultExprImpl&) = delete;
IfThenResultExprImpl& operator=(const IfThenResultExprImpl&) = delete;
~IfThenResultExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc) const override {
// We compile the "then" and "else" expressions in separate statements so
// they have a defined sequencing. See https://crbug.com/529480.
CodeGen::Node then_node = then_result_->Compile(pc);
CodeGen::Node else_node = else_result_->Compile(pc);
return cond_->Compile(pc, then_node, else_node);
}
bool HasUnsafeTraps() const override {
return then_result_->HasUnsafeTraps() || else_result_->HasUnsafeTraps();
}
private:
BoolExpr cond_;
ResultExpr then_result_;
ResultExpr else_result_;
};
class ConstBoolExprImpl : public internal::BoolExprImpl {
public:
explicit ConstBoolExprImpl(bool value) : value_(value) {}
ConstBoolExprImpl(const ConstBoolExprImpl&) = delete;
ConstBoolExprImpl& operator=(const ConstBoolExprImpl&) = delete;
~ConstBoolExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc,
CodeGen::Node then_node,
CodeGen::Node else_node) const override {
return value_ ? then_node : else_node;
}
private:
bool value_;
};
class MaskedEqualBoolExprImpl : public internal::BoolExprImpl {
public:
MaskedEqualBoolExprImpl(int argno,
size_t width,
uint64_t mask,
uint64_t value)
: argno_(argno), width_(width), mask_(mask), value_(value) {}
MaskedEqualBoolExprImpl(const MaskedEqualBoolExprImpl&) = delete;
MaskedEqualBoolExprImpl& operator=(const MaskedEqualBoolExprImpl&) = delete;
~MaskedEqualBoolExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc,
CodeGen::Node then_node,
CodeGen::Node else_node) const override {
return pc->MaskedEqual(argno_, width_, mask_, value_, then_node, else_node);
}
private:
int argno_;
size_t width_;
uint64_t mask_;
uint64_t value_;
};
class NegateBoolExprImpl : public internal::BoolExprImpl {
public:
explicit NegateBoolExprImpl(BoolExpr cond) : cond_(std::move(cond)) {}
NegateBoolExprImpl(const NegateBoolExprImpl&) = delete;
NegateBoolExprImpl& operator=(const NegateBoolExprImpl&) = delete;
~NegateBoolExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc,
CodeGen::Node then_node,
CodeGen::Node else_node) const override {
return cond_->Compile(pc, else_node, then_node);
}
private:
BoolExpr cond_;
};
class AndBoolExprImpl : public internal::BoolExprImpl {
public:
AndBoolExprImpl(BoolExpr lhs, BoolExpr rhs)
: lhs_(std::move(lhs)), rhs_(std::move(rhs)) {}
AndBoolExprImpl(const AndBoolExprImpl&) = delete;
AndBoolExprImpl& operator=(const AndBoolExprImpl&) = delete;
~AndBoolExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc,
CodeGen::Node then_node,
CodeGen::Node else_node) const override {
return lhs_->Compile(pc, rhs_->Compile(pc, then_node, else_node),
else_node);
}
private:
BoolExpr lhs_;
BoolExpr rhs_;
};
class OrBoolExprImpl : public internal::BoolExprImpl {
public:
OrBoolExprImpl(BoolExpr lhs, BoolExpr rhs)
: lhs_(std::move(lhs)), rhs_(std::move(rhs)) {}
OrBoolExprImpl(const OrBoolExprImpl&) = delete;
OrBoolExprImpl& operator=(const OrBoolExprImpl&) = delete;
~OrBoolExprImpl() override = default;
CodeGen::Node Compile(PolicyCompiler* pc,
CodeGen::Node then_node,
CodeGen::Node else_node) const override {
return lhs_->Compile(pc, then_node,
rhs_->Compile(pc, then_node, else_node));
}
private:
BoolExpr lhs_;
BoolExpr rhs_;
};
} // namespace
namespace internal {
bool ResultExprImpl::HasUnsafeTraps() const {
return false;
}
bool ResultExprImpl::IsAllow() const {
return false;
}
bool ResultExprImpl::IsDeny() const {
return false;
}
uint64_t DefaultMask(size_t size) {
switch (size) {
case 4:
return std::numeric_limits<uint32_t>::max();
case 8:
return std::numeric_limits<uint64_t>::max();
default:
NOTREACHED() << "Unimplemented DefaultMask case";
}
}
BoolExpr ArgEq(int num, size_t size, uint64_t mask, uint64_t val) {
// If this is changed, update Arg<T>::EqualTo's static_cast rules
// accordingly.
CHECK(size == 4 || size == 8);
return std::make_shared<MaskedEqualBoolExprImpl>(num, size, mask, val);
}
} // namespace internal
ResultExpr Allow() {
return std::make_shared<ReturnResultExprImpl>(SECCOMP_RET_ALLOW);
}
ResultExpr Error(int err) {
CHECK(err >= ErrorCode::ERR_MIN_ERRNO && err <= ErrorCode::ERR_MAX_ERRNO);
return std::make_shared<ReturnResultExprImpl>(SECCOMP_RET_ERRNO + err);
}
ResultExpr Kill() {
return std::make_shared<ReturnResultExprImpl>(SECCOMP_RET_KILL);
}
ResultExpr Trace(uint16_t aux) {
return std::make_shared<ReturnResultExprImpl>(SECCOMP_RET_TRACE + aux);
}
ResultExpr Trap(TrapRegistry::TrapFnc trap_func, const void* aux) {
return std::make_shared<TrapResultExprImpl>(trap_func, aux, true /* safe */);
}
ResultExpr UnsafeTrap(TrapRegistry::TrapFnc trap_func, const void* aux) {
return std::make_shared<TrapResultExprImpl>(trap_func, aux,
false /* unsafe */);
}
ResultExpr UserNotify() {
return std::make_shared<ReturnResultExprImpl>(SECCOMP_RET_USER_NOTIF);
}
BoolExpr BoolConst(bool value) {
return std::make_shared<ConstBoolExprImpl>(value);
}
BoolExpr Not(BoolExpr cond) {
return std::make_shared<NegateBoolExprImpl>(std::move(cond));
}
BoolExpr AllOf() {
return BoolConst(true);
}
BoolExpr AllOf(BoolExpr lhs, BoolExpr rhs) {
return std::make_shared<AndBoolExprImpl>(std::move(lhs), std::move(rhs));
}
BoolExpr AnyOf() {
return BoolConst(false);
}
BoolExpr AnyOf(BoolExpr lhs, BoolExpr rhs) {
return std::make_shared<OrBoolExprImpl>(std::move(lhs), std::move(rhs));
}
Elser If(BoolExpr cond, ResultExpr then_result) {
return Elser(nullptr).ElseIf(std::move(cond), std::move(then_result));
}
Elser::Elser(cons::List<Clause> clause_list) : clause_list_(clause_list) {
}
Elser::Elser(const Elser& elser) = default;
Elser::~Elser() = default;
Elser Elser::ElseIf(BoolExpr cond, ResultExpr then_result) const {
return Elser(Cons(std::make_pair(std::move(cond), std::move(then_result)),
clause_list_));
}
ResultExpr Elser::Else(ResultExpr else_result) const {
// We finally have the default result expression for this
// if/then/else sequence. Also, we've already accumulated all
// if/then pairs into a list of reverse order (i.e., lower priority
// conditions are listed before higher priority ones). E.g., an
// expression like
//
// If(b1, e1).ElseIf(b2, e2).ElseIf(b3, e3).Else(e4)
//
// will have built up a list like
//
// [(b3, e3), (b2, e2), (b1, e1)].
//
// Now that we have e4, we can walk the list and create a ResultExpr
// tree like:
//
// expr = e4
// expr = (b3 ? e3 : expr) = (b3 ? e3 : e4)
// expr = (b2 ? e2 : expr) = (b2 ? e2 : (b3 ? e3 : e4))
// expr = (b1 ? e1 : expr) = (b1 ? e1 : (b2 ? e2 : (b3 ? e3 : e4)))
//
// and end up with an appropriately chained tree.
ResultExpr expr = std::move(else_result);
for (const Clause& clause : clause_list_) {
expr = std::make_shared<IfThenResultExprImpl>(clause.first, clause.second,
std::move(expr));
}
return expr;
}
} // namespace bpf_dsl
} // namespace sandbox
namespace std {
template class shared_ptr<const sandbox::bpf_dsl::internal::BoolExprImpl>;
template class shared_ptr<const sandbox::bpf_dsl::internal::ResultExprImpl>;
} // namespace std
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