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// Copyright 2018 The gVisor Authors.
//
// 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.
package seccomp
import (
"syscall"
"unsafe"
"gvisor.dev/gvisor/pkg/abi/linux"
)
// sockFprog is sock_fprog taken from <linux/filter.h>.
type sockFprog struct {
Len uint16
pad [6]byte
Filter *linux.BPFInstruction
}
// SetFilter installs the given BPF program.
//
// This is safe to call from an afterFork context.
//
//go:nosplit
func SetFilter(instrs []linux.BPFInstruction) syscall.Errno {
// PR_SET_NO_NEW_PRIVS is required in order to enable seccomp. See seccomp(2) for details.
if _, _, errno := syscall.RawSyscall(syscall.SYS_PRCTL, linux.PR_SET_NO_NEW_PRIVS, 1, 0); errno != 0 {
return errno
}
sockProg := sockFprog{
Len: uint16(len(instrs)),
Filter: (*linux.BPFInstruction)(unsafe.Pointer(&instrs[0])),
}
return seccomp(linux.SECCOMP_SET_MODE_FILTER, linux.SECCOMP_FILTER_FLAG_TSYNC, unsafe.Pointer(&sockProg))
}
func isKillProcessAvailable() (bool, error) {
action := uint32(linux.SECCOMP_RET_KILL_PROCESS)
if errno := seccomp(linux.SECCOMP_GET_ACTION_AVAIL, 0, unsafe.Pointer(&action)); errno != 0 {
// EINVAL: SECCOMP_GET_ACTION_AVAIL not in this kernel yet.
// EOPNOTSUPP: SECCOMP_RET_KILL_PROCESS not supported.
if errno == syscall.EINVAL || errno == syscall.EOPNOTSUPP {
return false, nil
}
return false, errno
}
return true, nil
}
// seccomp calls seccomp(2). This is safe to call from an afterFork context.
//
//go:nosplit
func seccomp(op, flags uint32, ptr unsafe.Pointer) syscall.Errno {
if _, _, errno := syscall.RawSyscall(SYS_SECCOMP, uintptr(op), uintptr(flags), uintptr(ptr)); errno != 0 {
return errno
}
return 0
}
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