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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 cmd holds implementations of the runsc commands.
package cmd
import (
"fmt"
"os"
"runtime"
"strconv"
"strings"
specs "github.com/opencontainers/runtime-spec/specs-go"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/runsc/specutils"
)
// intFlags can be used with int flags that appear multiple times. It supports
// comma-separated lists too.
type intFlags []int
// String implements flag.Value.
func (i *intFlags) String() string {
sInts := make([]string, 0, len(*i))
for _, fd := range *i {
sInts = append(sInts, strconv.Itoa(fd))
}
return strings.Join(sInts, ",")
}
// Get implements flag.Value.
func (i *intFlags) Get() any {
return i
}
// GetArray returns an array of ints representing FDs.
func (i *intFlags) GetArray() []int {
return *i
}
// GetFDs returns an array of *fd.FD.
func (i *intFlags) GetFDs() []*fd.FD {
rv := make([]*fd.FD, 0, len(*i))
for _, val := range *i {
rv = append(rv, fd.New(val))
}
return rv
}
// Set implements flag.Value. Set(String()) should be idempotent.
func (i *intFlags) Set(s string) error {
for _, sFD := range strings.Split(s, ",") {
fd, err := strconv.Atoi(sFD)
if err != nil {
return fmt.Errorf("invalid flag value: %v", err)
}
if fd < -1 {
return fmt.Errorf("flag value must be >= -1: %d", fd)
}
*i = append(*i, fd)
}
return nil
}
// setCapsAndCallSelf sets capabilities to the current thread and then execve's
// itself again with the arguments specified in 'args' to restart the process
// with the desired capabilities.
func setCapsAndCallSelf(args []string, caps *specs.LinuxCapabilities) error {
// Keep thread locked while capabilities are changed.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
if err := applyCaps(caps); err != nil {
return fmt.Errorf("applyCaps() failed: %v", err)
}
binPath := specutils.ExePath
log.Infof("Execve %q again, bye!", binPath)
err := unix.Exec(binPath, args, os.Environ())
return fmt.Errorf("error executing %s: %v", binPath, err)
}
// callSelfAsNobody sets UID and GID to nobody and then execve's itself again.
func callSelfAsNobody(args []string) error {
// Keep thread locked while user/group are changed.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
const nobody = 65534
if _, _, err := unix.RawSyscall(unix.SYS_SETGID, uintptr(nobody), 0, 0); err != 0 {
return fmt.Errorf("error setting uid: %v", err)
}
if _, _, err := unix.RawSyscall(unix.SYS_SETUID, uintptr(nobody), 0, 0); err != 0 {
return fmt.Errorf("error setting gid: %v", err)
}
// Drop all capabilities.
if err := applyCaps(&specs.LinuxCapabilities{}); err != nil {
return fmt.Errorf("error dropping capabilities: %w", err)
}
binPath := specutils.ExePath
log.Infof("Execve %q again, bye!", binPath)
err := unix.Exec(binPath, args, os.Environ())
return fmt.Errorf("error executing %s: %v", binPath, err)
}
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