165 lines
3.4 KiB
Go
165 lines
3.4 KiB
Go
/*
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Copyright The containerd Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package command
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import (
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"bytes"
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"encoding/json"
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"io"
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"os"
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"path/filepath"
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"syscall"
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"text/template"
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specs "github.com/opencontainers/runtime-spec/specs-go"
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"github.com/urfave/cli"
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)
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var ociHook = cli.Command{
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Name: "oci-hook",
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Usage: "provides a base for OCI runtime hooks to allow arguments to be injected.",
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Action: func(context *cli.Context) error {
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state, err := loadHookState(os.Stdin)
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if err != nil {
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return err
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}
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spec, err := loadSpec(state.Bundle)
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if err != nil {
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return err
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}
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var (
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ctx = newTemplateContext(state, spec)
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args = []string(context.Args())
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env = os.Environ()
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)
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if err := newList(&args).render(ctx); err != nil {
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return err
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}
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if err := newList(&env).render(ctx); err != nil {
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return err
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}
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return syscall.Exec(args[0], args, env)
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},
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}
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type hookSpec struct {
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Root struct {
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Path string `json:"path"`
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} `json:"root"`
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}
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func loadSpec(bundle string) (*hookSpec, error) {
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f, err := os.Open(filepath.Join(bundle, "config.json"))
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if err != nil {
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return nil, err
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}
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defer f.Close()
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var s hookSpec
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if err := json.NewDecoder(f).Decode(&s); err != nil {
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return nil, err
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}
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return &s, nil
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}
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func loadHookState(r io.Reader) (*specs.State, error) {
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var s specs.State
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if err := json.NewDecoder(r).Decode(&s); err != nil {
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return nil, err
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}
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return &s, nil
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}
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func newTemplateContext(state *specs.State, spec *hookSpec) *templateContext {
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t := &templateContext{
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state: state,
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root: spec.Root.Path,
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}
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t.funcs = template.FuncMap{
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"id": t.id,
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"bundle": t.bundle,
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"rootfs": t.rootfs,
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"pid": t.pid,
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"annotation": t.annotation,
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"status": t.status,
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}
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return t
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}
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type templateContext struct {
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state *specs.State
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root string
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funcs template.FuncMap
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}
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func (t *templateContext) id() string {
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return t.state.ID
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}
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func (t *templateContext) bundle() string {
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return t.state.Bundle
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}
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func (t *templateContext) rootfs() string {
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if filepath.IsAbs(t.root) {
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return t.root
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}
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return filepath.Join(t.state.Bundle, t.root)
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}
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func (t *templateContext) pid() int {
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return t.state.Pid
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}
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func (t *templateContext) annotation(k string) string {
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return t.state.Annotations[k]
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}
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func (t *templateContext) status() string {
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return t.state.Status
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}
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func render(ctx *templateContext, source string, out io.Writer) error {
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t, err := template.New("oci-hook").Funcs(ctx.funcs).Parse(source)
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if err != nil {
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return err
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}
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return t.Execute(out, ctx)
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}
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func newList(l *[]string) *templateList {
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return &templateList{
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l: l,
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}
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}
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type templateList struct {
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l *[]string
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}
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func (l *templateList) render(ctx *templateContext) error {
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buf := bytes.NewBuffer(nil)
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for i, s := range *l.l {
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buf.Reset()
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if err := render(ctx, s, buf); err != nil {
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return err
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}
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(*l.l)[i] = buf.String()
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}
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buf.Reset()
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return nil
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}
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