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sandboxed-api/sandboxed_api/sandbox2/policybuilder.cc
Martijn Vels 753eacd314 Reduce requirements for restartable sequences 
PiperOrigin-RevId: 361780465
Change-Id: I299bc55c94d60575e16f0ea6b5f82b8b793af1cb
2021-03-09 04:33:29 -08:00

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// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "sandboxed_api/sandbox2/policybuilder.h"
#include <asm/ioctls.h> // For TCGETS
#include <fcntl.h> // For the fcntl flags
#include <linux/futex.h>
#include <linux/net.h> // For SYS_CONNECT
#include <linux/random.h> // For GRND_NONBLOCK
#include <sys/mman.h> // For mmap arguments
#include <sys/socket.h>
#include <syscall.h>
#include <csignal>
#include <cstdint>
#include <utility>
#include "absl/memory/memory.h"
#include "absl/status/statusor.h"
#include "absl/strings/escaping.h"
#include "absl/strings/match.h"
#include "sandboxed_api/config.h"
#include "sandboxed_api/sandbox2/namespace.h"
#include "sandboxed_api/sandbox2/util/bpf_helper.h"
#include "sandboxed_api/util/path.h"
#include "sandboxed_api/util/status_macros.h"
#if defined(SAPI_X86_64)
#include <asm/prctl.h>
#elif defined(SAPI_PPC64_LE)
#include <asm/termbits.h> // On PPC, TCGETS macro needs termios
#endif
namespace sandbox2 {
namespace {
namespace file = ::sapi::file;
constexpr PolicyBuilder::SyscallInitializer kMmapSyscalls = {
#ifdef __NR_mmap2
__NR_mmap2,
#endif
#ifdef __NR_mmap
__NR_mmap,
#endif
};
} // namespace
PolicyBuilder& PolicyBuilder::AllowSyscall(unsigned int num) {
if (handled_syscalls_.insert(num).second) {
user_policy_.insert(user_policy_.end(), {SYSCALL(num, ALLOW)});
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowSyscalls(const std::vector<uint32_t>& nums) {
for (auto num : nums) {
AllowSyscall(num);
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowSyscalls(SyscallInitializer nums) {
for (auto num : nums) {
AllowSyscall(num);
}
return *this;
}
PolicyBuilder& PolicyBuilder::BlockSyscallWithErrno(unsigned int num,
int error) {
if (handled_syscalls_.insert(num).second) {
user_policy_.insert(user_policy_.end(), {SYSCALL(num, ERRNO(error))});
if (num == __NR_bpf) {
user_policy_handles_bpf_ = true;
}
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowExit() {
return AllowSyscalls({__NR_exit, __NR_exit_group});
}
PolicyBuilder& PolicyBuilder::AllowScudoMalloc() {
AllowTime();
AllowSyscalls({__NR_munmap, __NR_nanosleep});
AllowFutexOp(FUTEX_WAKE);
AllowLimitedMadvise();
AllowGetRandom();
AllowWipeOnFork();
return AddPolicyOnMmap([](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(2), // prot
JEQ32(PROT_NONE, JUMP(&labels, prot_none)),
JNE32(PROT_READ | PROT_WRITE, JUMP(&labels, mmap_end)),
// PROT_READ | PROT_WRITE
ARG_32(3), // flags
JEQ32(MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, ALLOW),
JEQ32(MAP_PRIVATE | MAP_ANONYMOUS, ALLOW),
JUMP(&labels, mmap_end),
// PROT_NONE
LABEL(&labels, prot_none),
ARG_32(3), // flags
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, ALLOW),
LABEL(&labels, mmap_end),
};
});
}
PolicyBuilder& PolicyBuilder::AllowTcMalloc() {
AllowTime();
AllowRestartableSequences();
AllowSyscalls(
{__NR_munmap, __NR_nanosleep, __NR_brk, __NR_mincore, __NR_membarrier});
AllowLimitedMadvise();
AddPolicyOnSyscall(__NR_mprotect, {
ARG_32(2),
JEQ32(PROT_READ | PROT_WRITE, ALLOW),
JEQ32(PROT_NONE, ALLOW),
});
return AddPolicyOnMmap([](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(2), // prot
JEQ32(PROT_NONE, JUMP(&labels, prot_none)),
JNE32(PROT_READ | PROT_WRITE, JUMP(&labels, mmap_end)),
// PROT_READ | PROT_WRITE
ARG_32(3), // flags
JNE32(MAP_ANONYMOUS | MAP_PRIVATE, JUMP(&labels, mmap_end)),
ALLOW,
// PROT_NONE
LABEL(&labels, prot_none),
ARG_32(3), // flags
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, ALLOW),
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE, ALLOW),
LABEL(&labels, mmap_end),
};
});
}
PolicyBuilder& PolicyBuilder::AllowSystemMalloc() {
AllowSyscalls({__NR_munmap, __NR_brk});
AllowFutexOp(FUTEX_WAKE);
AddPolicyOnSyscall(__NR_mremap, {
ARG_32(3),
JEQ32(MREMAP_MAYMOVE, ALLOW),
});
return AddPolicyOnMmap([](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(2), // prot
JEQ32(PROT_NONE, JUMP(&labels, prot_none)),
JNE32(PROT_READ | PROT_WRITE, JUMP(&labels, mmap_end)),
// PROT_READ | PROT_WRITE
ARG_32(3), // flags
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE, ALLOW),
// PROT_NONE
LABEL(&labels, prot_none),
ARG_32(3), // flags
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, ALLOW),
LABEL(&labels, mmap_end),
};
});
return *this;
}
PolicyBuilder& PolicyBuilder::AllowLlvmSanitizers() {
if constexpr (sapi::sanitizers::IsAny()) {
AddPolicyOnSyscall(__NR_madvise, {
ARG_32(2),
JEQ32(MADV_DONTDUMP, ALLOW),
JEQ32(MADV_NOHUGEPAGE, ALLOW),
});
// Sanitizers read from /proc. For example:
// https://github.com/llvm-mirror/compiler-rt/blob/69445f095c22aac2388f939bedebf224a6efcdaf/lib/sanitizer_common/sanitizer_linux.cpp#L1101
AddDirectory("/proc");
}
if constexpr (sapi::sanitizers::IsASan()) {
AllowSyscall(__NR_sigaltstack);
// asan uses a custom allocator that runs mmap under the hood. For example:
// https://github.com/llvm/llvm-project/blob/596d534ac3524052df210be8d3c01a33b2260a42/compiler-rt/lib/asan/asan_allocator.cpp#L980
// https://github.com/llvm/llvm-project/blob/62ec4ac90738a5f2d209ed28c822223e58aaaeb7/compiler-rt/lib/sanitizer_common/sanitizer_allocator_secondary.h#L98
AllowMmap();
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowLimitedMadvise() {
return AddPolicyOnSyscall(__NR_madvise, {
ARG_32(2),
JEQ32(MADV_DONTNEED, ALLOW),
JEQ32(MADV_REMOVE, ALLOW),
JEQ32(MADV_NOHUGEPAGE, ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowMmap() {
return AllowSyscalls(kMmapSyscalls);
}
PolicyBuilder& PolicyBuilder::AllowOpen() {
#ifdef __NR_open
AllowSyscall(__NR_open);
#endif
#ifdef __NR_openat
AllowSyscall(__NR_openat);
#endif
return *this;
}
PolicyBuilder& PolicyBuilder::AllowStat() {
#ifdef __NR_fstat
AllowSyscall(__NR_fstat);
#endif
#ifdef __NR_fstat64
AllowSyscall(__NR_fstat64);
#endif
#ifdef __NR_fstatat
AllowSyscall(__NR_fstatat);
#endif
#ifdef __NR_fstatat64
AllowSyscall(__NR_fstatat64);
#endif
#ifdef __NR_lstat
AllowSyscall(__NR_lstat);
#endif
#ifdef __NR_lstat64
AllowSyscall(__NR_lstat64);
#endif
#ifdef __NR_newfstatat
AllowSyscall(__NR_newfstatat);
#endif
#ifdef __NR_oldfstat
AllowSyscall(__NR_oldfstat);
#endif
#ifdef __NR_oldlstat
AllowSyscall(__NR_oldlstat);
#endif
#ifdef __NR_oldstat
AllowSyscall(__NR_oldstat);
#endif
#ifdef __NR_stat
AllowSyscall(__NR_stat);
#endif
#ifdef __NR_stat64
AllowSyscall(__NR_stat64);
#endif
#ifdef __NR_statfs
AllowSyscall(__NR_statfs);
#endif
#ifdef __NR_statfs64
AllowSyscall(__NR_statfs64);
#endif
return *this;
}
PolicyBuilder& PolicyBuilder::AllowAccess() {
#ifdef __NR_access
AllowSyscall(__NR_access);
#endif
#ifdef __NR_faccessat
AllowSyscall(__NR_faccessat);
#endif
return *this;
}
PolicyBuilder& PolicyBuilder::AllowRead() {
return AllowSyscalls({
__NR_read,
__NR_readv,
__NR_preadv,
__NR_pread64,
});
}
PolicyBuilder& PolicyBuilder::AllowWrite() {
return AllowSyscalls({
__NR_write,
__NR_writev,
__NR_pwritev,
__NR_pwrite64,
});
}
PolicyBuilder& PolicyBuilder::AllowReaddir() {
return AllowSyscalls({
#ifdef __NR_getdents
__NR_getdents,
#endif
#ifdef __NR_getdents64
__NR_getdents64,
#endif
});
}
PolicyBuilder& PolicyBuilder::AllowSafeFcntl() {
return AddPolicyOnSyscalls({__NR_fcntl,
#ifdef __NR_fcntl64
__NR_fcntl64
#endif
},
{
ARG_32(1),
JEQ32(F_GETFD, ALLOW),
JEQ32(F_SETFD, ALLOW),
JEQ32(F_GETFL, ALLOW),
JEQ32(F_SETFL, ALLOW),
JEQ32(F_GETLK, ALLOW),
JEQ32(F_SETLK, ALLOW),
JEQ32(F_SETLKW, ALLOW),
JEQ32(F_DUPFD, ALLOW),
JEQ32(F_DUPFD_CLOEXEC, ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowFork() {
return AllowSyscalls({
#ifdef __NR_fork
__NR_fork,
#endif
#ifdef __NR_vfork
__NR_vfork,
#endif
__NR_clone});
}
PolicyBuilder& PolicyBuilder::AllowWait() {
return AllowSyscalls({
#ifdef __NR_waitpid
__NR_waitpid,
#endif
__NR_wait4});
}
PolicyBuilder& PolicyBuilder::AllowHandleSignals() {
return AllowSyscalls({
__NR_rt_sigaction,
__NR_rt_sigreturn,
__NR_rt_sigprocmask,
#ifdef __NR_signal
__NR_signal,
#endif
#ifdef __NR_sigaction
__NR_sigaction,
#endif
#ifdef __NR_sigreturn
__NR_sigreturn,
#endif
#ifdef __NR_sigprocmask
__NR_sigprocmask,
#endif
#ifdef __NR_sigaltstack
__NR_sigaltstack,
#endif
});
}
PolicyBuilder& PolicyBuilder::AllowTCGETS() {
return AddPolicyOnSyscall(__NR_ioctl, {
ARG_32(1),
JEQ32(TCGETS, ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowTime() {
return AllowSyscalls({
#ifdef __NR_time
__NR_time,
#endif
__NR_gettimeofday, __NR_clock_gettime});
}
PolicyBuilder& PolicyBuilder::AllowSleep() {
return AllowSyscalls({
__NR_clock_nanosleep,
__NR_nanosleep,
});
}
PolicyBuilder& PolicyBuilder::AllowGetIDs() {
return AllowSyscalls({
__NR_getuid,
__NR_geteuid,
__NR_getresuid,
__NR_getgid,
__NR_getegid,
__NR_getresgid,
#ifdef __NR_getuid32
__NR_getuid32,
__NR_geteuid32,
__NR_getresuid32,
__NR_getgid32,
__NR_getegid32,
__NR_getresgid32,
#endif
__NR_getgroups,
});
}
PolicyBuilder& PolicyBuilder::AllowRestartableSequences() {
AddPolicyOnMmap([](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(2), // prot
JEQ32(PROT_READ | PROT_WRITE, ALLOW),
ARG_32(3), // flags
JEQ32(MAP_PRIVATE | MAP_ANONYMOUS, ALLOW),
};
});
#ifdef __NR_rseq
AllowSyscall(__NR_rseq);
#endif
AllowFutexOp(FUTEX_WAIT);
AllowFutexOp(FUTEX_WAKE);
AddPolicyOnSyscall(__NR_rt_sigprocmask, {
ARG_32(0),
JEQ32(SIG_SETMASK, ALLOW),
});
return AllowSyscalls({__NR_membarrier, __NR_getcpu});
}
PolicyBuilder& PolicyBuilder::AllowGetPIDs() {
return AllowSyscalls({
__NR_getpid,
__NR_getppid,
__NR_gettid,
});
}
PolicyBuilder& PolicyBuilder::AllowGetRlimit() {
return AllowSyscalls({
#ifdef __NR_getrlimit
__NR_getrlimit,
#endif
#ifdef __NR_ugetrlimit
__NR_ugetrlimit,
#endif
});
}
PolicyBuilder& PolicyBuilder::AllowSetRlimit() {
return AllowSyscalls({
#ifdef __NR_setrlimit
__NR_setrlimit,
#endif
#ifdef __NR_usetrlimit
__NR_usetrlimit,
#endif
});
}
PolicyBuilder& PolicyBuilder::AllowGetRandom() {
return AddPolicyOnSyscall(__NR_getrandom, {
ARG_32(2),
JEQ32(0, ALLOW),
JEQ32(GRND_NONBLOCK, ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowWipeOnFork() {
// System headers may not be recent enough to include MADV_WIPEONFORK.
static constexpr uint32_t kMadv_WipeOnFork = 18;
// The -1 value is used by code to probe that the kernel returns -EINVAL for
// unknown values because some environments, like qemu, ignore madvise
// completely, but code needs to know whether WIPEONFORK took effect.
return AddPolicyOnSyscall(__NR_madvise,
{
ARG_32(2),
JEQ32(kMadv_WipeOnFork, ALLOW),
JEQ32(static_cast<uint32_t>(-1), ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowLogForwarding() {
AllowWrite();
AllowSystemMalloc();
AllowTcMalloc();
AllowSyscalls({// from logging code
__NR_clock_gettime,
// From comms
__NR_gettid, __NR_close});
// For LOG(FATAL)
return AddPolicyOnSyscall(__NR_kill,
[](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(0),
JNE32(0, JUMP(&labels, pid_not_null)),
ARG_32(1),
JEQ32(SIGABRT, ALLOW),
LABEL(&labels, pid_not_null),
};
});
}
PolicyBuilder& PolicyBuilder::AllowFutexOp(int op) {
return AddPolicyOnSyscall(
__NR_futex, {
ARG_32(1),
// a <- a & FUTEX_CMD_MASK
BPF_STMT(BPF_ALU + BPF_AND + BPF_K,
static_cast<uint32_t>(FUTEX_CMD_MASK)),
JEQ32(static_cast<uint32_t>(op) & FUTEX_CMD_MASK, ALLOW),
});
}
PolicyBuilder& PolicyBuilder::AllowStaticStartup() {
AllowGetRlimit();
AllowSyscalls({
// These syscalls take a pointer, so no restriction.
__NR_uname, __NR_brk, __NR_set_tid_address,
#if defined(__ARM_NR_set_tls)
// libc sets the TLS during startup
__ARM_NR_set_tls,
#endif
// This syscall takes a pointer and a length.
// We could restrict length, but it might change, so not worth it.
__NR_set_robust_list,
});
AllowFutexOp(FUTEX_WAIT_BITSET);
AddPolicyOnSyscall(__NR_rt_sigaction,
{
ARG_32(0),
// This is real-time signals used internally by libc.
JEQ32(__SIGRTMIN + 0, ALLOW),
JEQ32(__SIGRTMIN + 1, ALLOW),
});
AddPolicyOnSyscall(__NR_rt_sigprocmask, {
ARG_32(0),
JEQ32(SIG_UNBLOCK, ALLOW),
});
#ifdef SAPI_X86_64
// The second argument is a pointer.
AddPolicyOnSyscall(__NR_arch_prctl, {
ARG_32(0),
JEQ32(ARCH_SET_FS, ALLOW),
});
#endif
if constexpr (sapi::host_cpu::IsArm64()) {
BlockSyscallWithErrno(__NR_readlinkat, ENOENT);
}
#ifdef __NR_readlink
BlockSyscallWithErrno(__NR_readlink, ENOENT);
#endif
if constexpr (sapi::host_cpu::IsArm()) {
AddPolicyOnSyscall(__NR_mprotect, {
ARG_32(2),
JEQ32(PROT_READ, ALLOW),
});
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowDynamicStartup() {
AllowRead();
AllowStat();
AllowSyscalls({__NR_lseek,
#ifdef __NR__llseek
__NR__llseek, // Newer glibc on PPC
#endif
__NR_close, __NR_munmap});
AddPolicyOnSyscall(__NR_mprotect, {
ARG_32(2),
JEQ32(PROT_READ, ALLOW),
JEQ32(PROT_NONE, ALLOW),
JEQ32(PROT_READ | PROT_WRITE, ALLOW),
JEQ32(PROT_READ | PROT_EXEC, ALLOW),
});
AllowStaticStartup();
return AddPolicyOnMmap([](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(2), // prot
JEQ32(PROT_READ | PROT_EXEC, JUMP(&labels, prot_exec)),
JEQ32(PROT_READ | PROT_WRITE, JUMP(&labels, prot_read_write)),
JNE32(PROT_READ, JUMP(&labels, mmap_end)),
// PROT_READ
ARG_32(3), // flags
JEQ32(MAP_PRIVATE, ALLOW),
JUMP(&labels, mmap_end),
// PROT_READ | PROT_WRITE
LABEL(&labels, prot_read_write),
ARG_32(3), // flags
JEQ32(MAP_FILE | MAP_PRIVATE | MAP_FIXED | MAP_DENYWRITE, ALLOW),
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, ALLOW),
JEQ32(MAP_ANONYMOUS | MAP_PRIVATE, ALLOW),
JUMP(&labels, mmap_end),
// PROT_READ | PROT_EXEC
LABEL(&labels, prot_exec),
ARG_32(3), // flags
JEQ32(MAP_FILE | MAP_PRIVATE | MAP_DENYWRITE, ALLOW),
LABEL(&labels, mmap_end),
};
});
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscall(unsigned int num,
BpfInitializer policy) {
return AddPolicyOnSyscalls({num}, policy);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscall(
unsigned int num, const std::vector<sock_filter>& policy) {
return AddPolicyOnSyscalls({num}, policy);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscall(unsigned int num, BpfFunc f) {
return AddPolicyOnSyscalls({num}, f);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscalls(
SyscallInitializer nums, const std::vector<sock_filter>& policy) {
auto resolved_policy =
ResolveBpfFunc(
[nums, policy](bpf_labels& labels) -> std::vector<sock_filter> {
std::vector<sock_filter> out;
out.reserve(nums.size() + policy.size());
for (auto num : nums) {
out.insert(out.end(), {SYSCALL(num, JUMP(&labels, do_policy_l))});
}
out.insert(out.end(), {JUMP(&labels, dont_do_policy_l),
LABEL(&labels, do_policy_l)});
for (const auto& filter : policy) {
// Syscall arch is expected as TRACE value
if (filter.code == (BPF_RET | BPF_K) &&
(filter.k & SECCOMP_RET_ACTION) == SECCOMP_RET_TRACE &&
(filter.k & SECCOMP_RET_DATA) != Syscall::GetHostArch()) {
LOG(WARNING)
<< "SANDBOX2_TRACE should be used in policy instead of "
"TRACE(value)";
out.push_back(SANDBOX2_TRACE);
} else {
out.push_back(filter);
}
}
out.push_back(LOAD_SYSCALL_NR);
out.insert(out.end(), {LABEL(&labels, dont_do_policy_l)});
return out;
});
// Pre-/Postcondition: Syscall number loaded into A register
user_policy_.insert(user_policy_.end(), resolved_policy.begin(),
resolved_policy.end());
return *this;
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscalls(SyscallInitializer nums,
BpfInitializer policy) {
std::vector<sock_filter> policy_vector(policy);
return AddPolicyOnSyscalls(nums, policy_vector);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnSyscalls(SyscallInitializer nums,
BpfFunc f) {
return AddPolicyOnSyscalls(nums, ResolveBpfFunc(f));
}
PolicyBuilder& PolicyBuilder::AddPolicyOnMmap(BpfInitializer policy) {
return AddPolicyOnSyscalls(kMmapSyscalls, policy);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnMmap(
const std::vector<sock_filter>& policy) {
return AddPolicyOnSyscalls(kMmapSyscalls, policy);
}
PolicyBuilder& PolicyBuilder::AddPolicyOnMmap(BpfFunc f) {
return AddPolicyOnSyscalls(kMmapSyscalls, f);
}
PolicyBuilder& PolicyBuilder::DangerDefaultAllowAll() {
user_policy_.push_back(ALLOW);
return *this;
}
absl::StatusOr<std::string> PolicyBuilder::ValidateAbsolutePath(
absl::string_view path) {
if (!file::IsAbsolutePath(path)) {
return absl::InvalidArgumentError(
absl::StrCat("Path is not absolute: '", path, "'"));
}
return ValidatePath(path);
}
absl::StatusOr<std::string> PolicyBuilder::ValidatePath(
absl::string_view path) {
std::string fixed_path = file::CleanPath(path);
if (fixed_path != path) {
return absl::InvalidArgumentError(absl::StrCat(
"Path was not normalized. '", path, "' != '", fixed_path, "'"));
}
return fixed_path;
}
std::vector<sock_filter> PolicyBuilder::ResolveBpfFunc(BpfFunc f) {
bpf_labels l = {0};
std::vector<sock_filter> policy = f(l);
if (bpf_resolve_jumps(&l, policy.data(), policy.size()) != 0) {
SetError(absl::InternalError("Cannot resolve bpf jumps"));
}
return policy;
}
absl::StatusOr<std::unique_ptr<Policy>> PolicyBuilder::TryBuild() {
auto output = absl::WrapUnique(new Policy());
if (!last_status_.ok()) {
return last_status_;
}
if (already_built_) {
return absl::FailedPreconditionError("Can only build policy once.");
}
if (use_namespaces_) {
if (allow_unrestricted_networking_ && hostname_ != kDefaultHostname) {
return absl::FailedPreconditionError(
"Cannot set hostname without network namespaces.");
}
output->SetNamespace(absl::make_unique<Namespace>(
allow_unrestricted_networking_, std::move(mounts_), hostname_));
} else {
// Not explicitly disabling them here as this is a technical limitation in
// our stack trace collection functionality.
LOG(WARNING) << "Using policy without namespaces, disabling stack traces on"
<< " crash";
}
output->collect_stacktrace_on_signal_ = collect_stacktrace_on_signal_;
output->collect_stacktrace_on_violation_ = collect_stacktrace_on_violation_;
output->collect_stacktrace_on_timeout_ = collect_stacktrace_on_timeout_;
output->collect_stacktrace_on_kill_ = collect_stacktrace_on_kill_;
output->user_policy_ = std::move(user_policy_);
output->user_policy_handles_bpf_ = user_policy_handles_bpf_;
auto pb_description = absl::make_unique<PolicyBuilderDescription>();
StoreDescription(pb_description.get());
output->policy_builder_description_ = std::move(pb_description);
output->allowed_hosts_ = std::move(allowed_hosts_);
already_built_ = true;
return std::move(output);
}
PolicyBuilder& PolicyBuilder::AddFile(absl::string_view path, bool is_ro) {
return AddFileAt(path, path, is_ro);
}
PolicyBuilder& PolicyBuilder::SetError(const absl::Status& status) {
LOG(ERROR) << status;
last_status_ = status;
return *this;
}
PolicyBuilder& PolicyBuilder::AddFileAt(absl::string_view outside,
absl::string_view inside, bool is_ro) {
EnableNamespaces();
auto fixed_outside_or = ValidateAbsolutePath(outside);
if (!fixed_outside_or.ok()) {
SetError(fixed_outside_or.status());
return *this;
}
auto fixed_outside = std::move(fixed_outside_or).value();
if (absl::StartsWith(fixed_outside, "/proc/self")) {
SetError(absl::InvalidArgumentError(
absl::StrCat("Cannot add /proc/self mounts, you need to mount the "
"whole /proc instead. You tried to mount ",
outside)));
return *this;
}
if (auto status = mounts_.AddFileAt(fixed_outside, inside, is_ro);
!status.ok()) {
SetError(
absl::InternalError(absl::StrCat("Could not add file ", outside, " => ",
inside, ": ", status.message())));
}
return *this;
}
PolicyBuilder& PolicyBuilder::AddLibrariesForBinary(
absl::string_view path, absl::string_view ld_library_path) {
EnableNamespaces();
auto fixed_path_or = ValidatePath(path);
if (!fixed_path_or.ok()) {
SetError(fixed_path_or.status());
return *this;
}
auto fixed_path = std::move(fixed_path_or).value();
if (auto status = mounts_.AddMappingsForBinary(fixed_path, ld_library_path);
!status.ok()) {
SetError(absl::InternalError(absl::StrCat(
"Could not add libraries for ", fixed_path, ": ", status.message())));
}
return *this;
}
PolicyBuilder& PolicyBuilder::AddLibrariesForBinary(
int fd, absl::string_view ld_library_path) {
return AddLibrariesForBinary(absl::StrCat("/proc/self/fd/", fd),
ld_library_path);
}
PolicyBuilder& PolicyBuilder::AddDirectory(absl::string_view path, bool is_ro) {
return AddDirectoryAt(path, path, is_ro);
}
PolicyBuilder& PolicyBuilder::AddDirectoryAt(absl::string_view outside,
absl::string_view inside,
bool is_ro) {
EnableNamespaces();
auto fixed_outside_or = ValidateAbsolutePath(outside);
if (!fixed_outside_or.ok()) {
SetError(fixed_outside_or.status());
return *this;
}
auto fixed_outside = std::move(fixed_outside_or).value();
if (absl::StartsWith(fixed_outside, "/proc/self")) {
SetError(absl::InvalidArgumentError(
absl::StrCat("Cannot add /proc/self mounts, you need to mount the "
"whole /proc instead. You tried to mount ",
outside)));
return *this;
}
if (auto status = mounts_.AddDirectoryAt(fixed_outside, inside, is_ro);
!status.ok()) {
SetError(absl::InternalError(absl::StrCat("Could not add directory ",
outside, " => ", inside, ": ",
status.message())));
}
return *this;
}
PolicyBuilder& PolicyBuilder::AddTmpfs(absl::string_view inside, size_t sz) {
EnableNamespaces();
if (auto status = mounts_.AddTmpfs(inside, sz); !status.ok()) {
SetError(absl::InternalError(absl::StrCat("Could not mount tmpfs ", inside,
": ", status.message())));
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowUnrestrictedNetworking() {
EnableNamespaces();
allow_unrestricted_networking_ = true;
return *this;
}
PolicyBuilder& PolicyBuilder::SetHostname(absl::string_view hostname) {
EnableNamespaces();
hostname_ = std::string(hostname);
return *this;
}
PolicyBuilder& PolicyBuilder::CollectStacktracesOnViolation(bool enable) {
collect_stacktrace_on_violation_ = enable;
return *this;
}
PolicyBuilder& PolicyBuilder::CollectStacktracesOnSignal(bool enable) {
collect_stacktrace_on_signal_ = enable;
return *this;
}
PolicyBuilder& PolicyBuilder::CollectStacktracesOnTimeout(bool enable) {
collect_stacktrace_on_timeout_ = enable;
return *this;
}
PolicyBuilder& PolicyBuilder::CollectStacktracesOnKill(bool enable) {
collect_stacktrace_on_kill_ = enable;
return *this;
}
PolicyBuilder& PolicyBuilder::AddNetworkProxyPolicy() {
if (allowed_hosts_) {
SetError(absl::FailedPreconditionError(
"AddNetworkProxyPolicy or AddNetworkProxyHandlerPolicy can be called "
"at most once"));
return *this;
}
allowed_hosts_ = AllowedHosts();
AllowFutexOp(FUTEX_WAKE);
AllowFutexOp(FUTEX_WAIT);
AllowFutexOp(FUTEX_WAIT_BITSET);
AllowSyscalls({
#ifdef __NR_dup2
__NR_dup2,
#endif
__NR_recvmsg,
__NR_close,
__NR_gettid,
});
AddPolicyOnSyscall(__NR_socket, {
ARG_32(0),
JEQ32(AF_INET, ALLOW),
JEQ32(AF_INET6, ALLOW),
});
AddPolicyOnSyscall(__NR_getsockopt,
[](bpf_labels& labels) -> std::vector<sock_filter> {
return {
ARG_32(1),
JNE32(SOL_SOCKET, JUMP(&labels, getsockopt_end)),
ARG_32(2),
JEQ32(SO_TYPE, ALLOW),
LABEL(&labels, getsockopt_end),
};
});
#ifdef SAPI_PPC64_LE
AddPolicyOnSyscall(__NR_socketcall, {
ARG_32(0),
JEQ32(SYS_SOCKET, ALLOW),
JEQ32(SYS_GETSOCKOPT, ALLOW),
JEQ32(SYS_RECVMSG, ALLOW),
});
#endif
return *this;
}
PolicyBuilder& PolicyBuilder::AddNetworkProxyHandlerPolicy() {
AddNetworkProxyPolicy();
AllowSyscall(__NR_rt_sigreturn);
AddPolicyOnSyscall(__NR_rt_sigaction, {
ARG_32(0),
JEQ32(SIGSYS, ALLOW),
});
AddPolicyOnSyscall(__NR_rt_sigprocmask, {
ARG_32(0),
JEQ32(SIG_UNBLOCK, ALLOW),
});
AddPolicyOnSyscall(__NR_connect, {TRAP(0)});
#ifdef SAPI_PPC64_LE
AddPolicyOnSyscall(__NR_socketcall, {
ARG_32(0),
JEQ32(SYS_CONNECT, TRAP(0)),
});
#endif
return *this;
}
PolicyBuilder& PolicyBuilder::SetRootWritable() {
EnableNamespaces();
mounts_.SetRootWritable();
return *this;
}
void PolicyBuilder::StoreDescription(PolicyBuilderDescription* pb_description) {
for (const auto& handled_syscall : handled_syscalls_) {
pb_description->add_handled_syscalls(handled_syscall);
}
}
PolicyBuilder& PolicyBuilder::AllowIPv4(const std::string& ip_and_mask,
uint32_t port) {
if (!allowed_hosts_) {
SetError(absl::FailedPreconditionError(
"AddNetworkProxyPolicy or AddNetworkProxyHandlerPolicy must be called "
"before adding IP rules"));
return *this;
}
absl::Status status = allowed_hosts_->AllowIPv4(ip_and_mask, port);
if (!status.ok()) {
SetError(status);
}
return *this;
}
PolicyBuilder& PolicyBuilder::AllowIPv6(const std::string& ip_and_mask,
uint32_t port) {
if (!allowed_hosts_) {
SetError(absl::FailedPreconditionError(
"AddNetworkProxyPolicy or AddNetworkProxyHandlerPolicy must be called "
"before adding IP rules"));
return *this;
}
absl::Status status = allowed_hosts_->AllowIPv6(ip_and_mask, port);
if (!status.ok()) {
SetError(status);
}
return *this;
}
} // namespace sandbox2
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