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// Copyright 2020 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 control
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
)
// SCMRightsVFS2 represents a SCM_RIGHTS socket control message.
type SCMRightsVFS2 interface {
transport.RightsControlMessage
// Files returns up to max RightsFiles.
//
// Returned files are consumed and ownership is transferred to the caller.
// Subsequent calls to Files will return the next files.
Files(ctx context.Context, max int) (rf RightsFilesVFS2, truncated bool)
}
// RightsFiles represents a SCM_RIGHTS socket control message. A reference is
// maintained for each vfs.FileDescription and is release either when an FD is created or
// when the Release method is called.
type RightsFilesVFS2 []*vfs.FileDescription
// NewSCMRightsVFS2 creates a new SCM_RIGHTS socket control message
// representation using local sentry FDs.
func NewSCMRightsVFS2(t *kernel.Task, fds []int32) (SCMRightsVFS2, error) {
files := make(RightsFilesVFS2, 0, len(fds))
for _, fd := range fds {
file := t.GetFileVFS2(fd)
if file == nil {
files.Release()
return nil, syserror.EBADF
}
files = append(files, file)
}
return &files, nil
}
// Files implements SCMRights.Files.
func (fs *RightsFilesVFS2) Files(ctx context.Context, max int) (RightsFilesVFS2, bool) {
n := max
var trunc bool
if l := len(*fs); n > l {
n = l
} else if n < l {
trunc = true
}
rf := (*fs)[:n]
*fs = (*fs)[n:]
return rf, trunc
}
// Clone implements transport.RightsControlMessage.Clone.
func (fs *RightsFilesVFS2) Clone() transport.RightsControlMessage {
nfs := append(RightsFilesVFS2(nil), *fs...)
for _, nf := range nfs {
nf.IncRef()
}
return &nfs
}
// Release implements transport.RightsControlMessage.Release.
func (fs *RightsFilesVFS2) Release() {
for _, f := range *fs {
f.DecRef()
}
*fs = nil
}
// rightsFDsVFS2 gets up to the specified maximum number of FDs.
func rightsFDsVFS2(t *kernel.Task, rights SCMRightsVFS2, cloexec bool, max int) ([]int32, bool) {
files, trunc := rights.Files(t, max)
fds := make([]int32, 0, len(files))
for i := 0; i < max && len(files) > 0; i++ {
fd, err := t.NewFDFromVFS2(0, files[0], kernel.FDFlags{
CloseOnExec: cloexec,
})
files[0].DecRef()
files = files[1:]
if err != nil {
t.Warningf("Error inserting FD: %v", err)
// This is what Linux does.
break
}
fds = append(fds, int32(fd))
}
return fds, trunc
}
// PackRightsVFS2 packs as many FDs as will fit into the unused capacity of buf.
func PackRightsVFS2(t *kernel.Task, rights SCMRightsVFS2, cloexec bool, buf []byte, flags int) ([]byte, int) {
maxFDs := (cap(buf) - len(buf) - linux.SizeOfControlMessageHeader) / 4
// Linux does not return any FDs if none fit.
if maxFDs <= 0 {
flags |= linux.MSG_CTRUNC
return buf, flags
}
fds, trunc := rightsFDsVFS2(t, rights, cloexec, maxFDs)
if trunc {
flags |= linux.MSG_CTRUNC
}
align := t.Arch().Width()
return putCmsg(buf, flags, linux.SCM_RIGHTS, align, fds)
}
// NewVFS2 creates default control messages if needed.
func NewVFS2(t *kernel.Task, socketOrEndpoint interface{}, rights SCMRightsVFS2) transport.ControlMessages {
return transport.ControlMessages{
Credentials: makeCreds(t, socketOrEndpoint),
Rights: rights,
}
}
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