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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <vector>
#include "base/bind.h"
#include "base/memory/scoped_ptr.h"
#include "base/posix/eintr_wrapper.h"
#include "build/build_config.h"
#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
#include "sandbox/linux/bpf_dsl/policy.h"
#include "sandbox/linux/bpf_dsl/seccomp_macros.h"
#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
#include "sandbox/linux/syscall_broker/broker_file_permission.h"
#include "sandbox/linux/syscall_broker/broker_process.h"
#include "sandbox/linux/system_headers/linux_syscalls.h"
#include "sandbox/linux/tests/unit_tests.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace sandbox {
namespace {
using bpf_dsl::Allow;
using bpf_dsl::ResultExpr;
using bpf_dsl::Trap;
bool NoOpCallback() {
return true;
}
// Test a trap handler that makes use of a broker process to open().
class InitializedOpenBroker {
public:
InitializedOpenBroker() : initialized_(false) {
std::vector<syscall_broker::BrokerFilePermission> permissions;
permissions.push_back(
syscall_broker::BrokerFilePermission::ReadOnly("/proc/allowed"));
permissions.push_back(
syscall_broker::BrokerFilePermission::ReadOnly("/proc/cpuinfo"));
broker_process_.reset(
new syscall_broker::BrokerProcess(EPERM, permissions));
BPF_ASSERT(broker_process() != NULL);
BPF_ASSERT(broker_process_->Init(base::Bind(&NoOpCallback)));
initialized_ = true;
}
bool initialized() { return initialized_; }
class syscall_broker::BrokerProcess* broker_process() {
return broker_process_.get();
}
private:
bool initialized_;
scoped_ptr<class syscall_broker::BrokerProcess> broker_process_;
DISALLOW_COPY_AND_ASSIGN(InitializedOpenBroker);
};
intptr_t BrokerOpenTrapHandler(const struct arch_seccomp_data& args,
void* aux) {
BPF_ASSERT(aux);
syscall_broker::BrokerProcess* broker_process =
static_cast<syscall_broker::BrokerProcess*>(aux);
switch (args.nr) {
case __NR_faccessat: // access is a wrapper of faccessat in android
BPF_ASSERT(static_cast<int>(args.args[0]) == AT_FDCWD);
return broker_process->Access(reinterpret_cast<const char*>(args.args[1]),
static_cast<int>(args.args[2]));
#if defined(__NR_access)
case __NR_access:
return broker_process->Access(reinterpret_cast<const char*>(args.args[0]),
static_cast<int>(args.args[1]));
#endif
#if defined(__NR_open)
case __NR_open:
return broker_process->Open(reinterpret_cast<const char*>(args.args[0]),
static_cast<int>(args.args[1]));
#endif
case __NR_openat:
// We only call open() so if we arrive here, it's because glibc uses
// the openat() system call.
BPF_ASSERT(static_cast<int>(args.args[0]) == AT_FDCWD);
return broker_process->Open(reinterpret_cast<const char*>(args.args[1]),
static_cast<int>(args.args[2]));
default:
BPF_ASSERT(false);
return -ENOSYS;
}
}
class DenyOpenPolicy : public bpf_dsl::Policy {
public:
explicit DenyOpenPolicy(InitializedOpenBroker* iob) : iob_(iob) {}
~DenyOpenPolicy() override {}
ResultExpr EvaluateSyscall(int sysno) const override {
DCHECK(SandboxBPF::IsValidSyscallNumber(sysno));
switch (sysno) {
case __NR_faccessat:
#if defined(__NR_access)
case __NR_access:
#endif
#if defined(__NR_open)
case __NR_open:
#endif
case __NR_openat:
// We get a InitializedOpenBroker class, but our trap handler wants
// the syscall_broker::BrokerProcess object.
return Trap(BrokerOpenTrapHandler, iob_->broker_process());
default:
return Allow();
}
}
private:
InitializedOpenBroker* iob_;
DISALLOW_COPY_AND_ASSIGN(DenyOpenPolicy);
};
// We use a InitializedOpenBroker class, so that we can run unsandboxed
// code in its constructor, which is the only way to do so in a BPF_TEST.
BPF_TEST(SandboxBPF,
UseOpenBroker,
DenyOpenPolicy,
InitializedOpenBroker /* (*BPF_AUX) */) {
BPF_ASSERT(BPF_AUX->initialized());
syscall_broker::BrokerProcess* broker_process = BPF_AUX->broker_process();
BPF_ASSERT(broker_process != NULL);
// First, use the broker "manually"
BPF_ASSERT(broker_process->Open("/proc/denied", O_RDONLY) == -EPERM);
BPF_ASSERT(broker_process->Access("/proc/denied", R_OK) == -EPERM);
BPF_ASSERT(broker_process->Open("/proc/allowed", O_RDONLY) == -ENOENT);
BPF_ASSERT(broker_process->Access("/proc/allowed", R_OK) == -ENOENT);
// Now use glibc's open() as an external library would.
BPF_ASSERT(open("/proc/denied", O_RDONLY) == -1);
BPF_ASSERT(errno == EPERM);
BPF_ASSERT(open("/proc/allowed", O_RDONLY) == -1);
BPF_ASSERT(errno == ENOENT);
// Also test glibc's openat(), some versions of libc use it transparently
// instead of open().
BPF_ASSERT(openat(AT_FDCWD, "/proc/denied", O_RDONLY) == -1);
BPF_ASSERT(errno == EPERM);
BPF_ASSERT(openat(AT_FDCWD, "/proc/allowed", O_RDONLY) == -1);
BPF_ASSERT(errno == ENOENT);
// And test glibc's access().
BPF_ASSERT(access("/proc/denied", R_OK) == -1);
BPF_ASSERT(errno == EPERM);
BPF_ASSERT(access("/proc/allowed", R_OK) == -1);
BPF_ASSERT(errno == ENOENT);
// This is also white listed and does exist.
int cpu_info_access = access("/proc/cpuinfo", R_OK);
BPF_ASSERT(cpu_info_access == 0);
int cpu_info_fd = open("/proc/cpuinfo", O_RDONLY);
BPF_ASSERT(cpu_info_fd >= 0);
char buf[1024];
BPF_ASSERT(read(cpu_info_fd, buf, sizeof(buf)) > 0);
}
} // namespace
} // namespace sandbox
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