gecko/security/sandbox/linux/SandboxAssembler.h

98 lines
3.2 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_SandboxAssembler_h
#define mozilla_SandboxAssembler_h
#include "sandbox/linux/seccomp-bpf/codegen.h"
#include <vector>
#include "mozilla/Assertions.h"
using namespace sandbox;
namespace mozilla {
class SandboxAssembler {
public:
SandboxAssembler();
~SandboxAssembler();
class Condition {
friend class SandboxAssembler;
uint32_t mSyscallNr;
bool mCheckingArg;
uint8_t mArgChecked;
// This class retains a copy of the array, because C++11
// initializer_list isn't supported on all relevant platforms.
std::vector<uint32_t> mArgValues;
public:
// Match any instance of the given syscall, with any arguments.
explicit Condition(uint32_t aSyscallNr)
: mSyscallNr(aSyscallNr)
, mCheckingArg(false)
{ }
// Match the syscall only if the given argument is one of the
// values in the array specified. (If the argument isn't
// representable as uint32, the process is killed or signaled, as
// appropriate.)
template<size_t n>
Condition(uint32_t aSyscallNr, uint8_t aArgChecked,
const uint32_t (&aArgValues)[n])
: mSyscallNr(aSyscallNr)
, mCheckingArg(true)
, mArgChecked(aArgChecked)
, mArgValues(aArgValues, aArgValues + n)
{
MOZ_ASSERT(aArgChecked < sNumArgs);
}
};
// Allow syscalls matching this condition, if no earlier condition matched.
void Allow(const Condition &aCond) {
Handle(aCond, RetAllow());
}
// Cause syscalls matching this condition to fail with the given error, if
// no earlier condition matched.
void Deny(int aErrno, const Condition &aCond) {
Handle(aCond, RetDeny(aErrno));
}
void Finish();
void Compile(std::vector<struct sock_filter> *aProgram,
bool aPrint = false);
private:
CodeGen mCode;
// The entry point of the filter program.
Instruction *mHead;
// Pointer to an instruction with a null successor which needs to be filled
// in with the rest of the program; see CodeGen::JoinInstructions.
Instruction *mTail;
// In some cases we will have two such instructions; this, if not null, is
// that. (If we have more complicated conditions in the future, this may
// need to be generalized into a vector<Instruction*>.)
Instruction *mTailAlt;
Instruction *RetAllow();
Instruction *RetDeny(int aErrno);
Instruction *RetKill();
Instruction *LoadArch(Instruction *aNext);
Instruction *LoadSyscall(Instruction *aNext);
Instruction *LoadArgHi(int aArg, Instruction *aNext);
Instruction *LoadArgLo(int aArg, Instruction *aNext);
Instruction *JmpEq(uint32_t aValue, Instruction *aThen, Instruction *aElse);
void AppendCheck(Instruction *aCheck,
Instruction *aNewTail,
Instruction *aNewTailAlt);
void Handle(const Condition &aCond, Instruction* aResult);
static const uint8_t sNumArgs = 6;
};
}
#endif