77 lines
2.4 KiB
Go
77 lines
2.4 KiB
Go
// Copyright 2018 The gVisor Authors.
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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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package linux
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import (
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/bpf"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/syserror"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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// userSockFprog is equivalent to Linux's struct sock_fprog on amd64.
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type userSockFprog struct {
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// Len is the length of the filter in BPF instructions.
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Len uint16
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_ [6]byte // padding for alignment
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// Filter is a user pointer to the struct sock_filter array that makes up
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// the filter program. Filter is a uint64 rather than a usermem.Addr
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// because usermem.Addr is actually uintptr, which is not a fixed-size
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// type, and encoding/binary.Read objects to this.
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Filter uint64
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}
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// seccomp applies a seccomp policy to the current task.
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func seccomp(t *kernel.Task, mode, flags uint64, addr usermem.Addr) error {
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// We only support SECCOMP_SET_MODE_FILTER at the moment.
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if mode != linux.SECCOMP_SET_MODE_FILTER {
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// Unsupported mode.
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return syserror.EINVAL
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}
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tsync := flags&linux.SECCOMP_FILTER_FLAG_TSYNC != 0
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// The only flag we support now is SECCOMP_FILTER_FLAG_TSYNC.
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if flags&^linux.SECCOMP_FILTER_FLAG_TSYNC != 0 {
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// Unsupported flag.
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return syserror.EINVAL
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}
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var fprog userSockFprog
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if _, err := t.CopyIn(addr, &fprog); err != nil {
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return err
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}
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filter := make([]linux.BPFInstruction, int(fprog.Len))
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if _, err := t.CopyIn(usermem.Addr(fprog.Filter), &filter); err != nil {
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return err
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}
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compiledFilter, err := bpf.Compile(filter)
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if err != nil {
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t.Debugf("Invalid seccomp-bpf filter: %v", err)
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return syserror.EINVAL
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}
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return t.AppendSyscallFilter(compiledFilter, tsync)
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}
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// Seccomp implements linux syscall seccomp(2).
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func Seccomp(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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return 0, nil, seccomp(t, args[0].Uint64(), args[1].Uint64(), args[2].Pointer())
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}
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