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https://github.com/google/sandboxed-api.git
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33206c5d3f
On some newer compiler versions, compiler optimizations and loop unrolling change the memory layout so that 64 bytes are not enough to overwrite the return address reliably. PiperOrigin-RevId: 240343358 Change-Id: Ifb1a1dc1cb482793b7387887f0fd68a237879227
80 lines
2.5 KiB
C++
80 lines
2.5 KiB
C++
// Copyright 2019 Google LLC. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// This file is an example of a computational-centric binary which is intended
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// to be sandboxed by the sandbox2.
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#include <syscall.h>
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#include <cstdint>
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#include <cstring>
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#include <glog/logging.h>
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#include "sandboxed_api/util/flag.h"
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#include "sandboxed_api/sandbox2/client.h"
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#include "sandboxed_api/sandbox2/comms.h"
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#include "sandboxed_api/sandbox2/util.h"
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ABSL_FLAG(bool, call_syscall_not_allowed, false,
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"Call a syscall that is not allowed by policy.");
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// This function is insecure (i.e. can be crashed and exploited) to demonstrate
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// how sandboxing can be helpful in defending against bugs.
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// We need to make sure that this function is not inlined, so that we don't
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// optimize the bug away.
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static uint32_t ComputeCRC4Impl(const uint8_t* ptr, uint64_t len) {
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uint8_t buf[8] = {0};
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memcpy(buf, ptr, len); // buffer overflow!
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uint32_t crc4 = 0;
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for (uint64_t i = 0; i < len; i++) {
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crc4 ^= (buf[i] << (i % 4) * 8);
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}
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return crc4;
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}
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int main(int argc, char** argv) {
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google::ParseCommandLineFlags(&argc, &argv, false);
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// Set-up the sandbox2::Client object, using a file descriptor (1023).
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sandbox2::Comms comms(sandbox2::Comms::kSandbox2ClientCommsFD);
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sandbox2::Client sandbox2_client(&comms);
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// Enable sandboxing from here.
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sandbox2_client.SandboxMeHere();
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// A syscall not allowed in policy, should cause a violation.
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if (absl::GetFlag(FLAGS_call_syscall_not_allowed)) {
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sandbox2::util::Syscall(__NR_sendfile, 0, 0, 0, 0, 0, 0);
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}
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// Receive data to be processed, process it, and return results.
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std::vector<uint8_t> buffer;
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if (!comms.RecvBytes(&buffer)) {
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return 1;
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}
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// Make sure we don't inline the function. See the comment in
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// ComputeCRC4Impl() for more details.
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std::function<uint32_t(const uint8_t*, uint64_t)> ComputeCRC4 =
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ComputeCRC4Impl;
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uint32_t crc4 = ComputeCRC4(buffer.data(), buffer.size());
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if (!comms.SendUint32(crc4)) {
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return 2;
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}
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return 0;
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}
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