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// Copyright 2020 The Hugo Authors. All rights reserved.
//
// 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 hexec
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"regexp"
"strings"
"os"
"os/exec"
"github.com/cli/safeexec"
"github.com/gohugoio/hugo/config"
"github.com/gohugoio/hugo/config/security"
)
var WithDir = func(dir string) func(c *commandeer) {
return func(c *commandeer) {
c.dir = dir
}
}
var WithContext = func(ctx context.Context) func(c *commandeer) {
return func(c *commandeer) {
c.ctx = ctx
}
}
var WithStdout = func(w io.Writer) func(c *commandeer) {
return func(c *commandeer) {
c.stdout = w
}
}
var WithStderr = func(w io.Writer) func(c *commandeer) {
return func(c *commandeer) {
c.stderr = w
}
}
var WithStdin = func(r io.Reader) func(c *commandeer) {
return func(c *commandeer) {
c.stdin = r
}
}
var WithEnviron = func(env []string) func(c *commandeer) {
return func(c *commandeer) {
setOrAppend := func(s string) {
k1, _ := config.SplitEnvVar(s)
var found bool
for i, v := range c.env {
k2, _ := config.SplitEnvVar(v)
if k1 == k2 {
found = true
c.env[i] = s
}
}
if !found {
c.env = append(c.env, s)
}
}
for _, s := range env {
setOrAppend(s)
}
}
}
// New creates a new Exec using the provided security config.
func New(cfg security.Config) *Exec {
var baseEnviron []string
for _, v := range os.Environ() {
k, _ := config.SplitEnvVar(v)
if cfg.Exec.OsEnv.Accept(k) {
baseEnviron = append(baseEnviron, v)
}
}
return &Exec{
sc: cfg,
baseEnviron: baseEnviron,
}
}
// IsNotFound reports whether this is an error about a binary not found.
func IsNotFound(err error) bool {
var notFoundErr *NotFoundError
return errors.As(err, ¬FoundErr)
}
// SafeCommand is a wrapper around os/exec Command which uses a LookPath
// implementation that does not search in current directory before looking in PATH.
// See https://github.com/cli/safeexec and the linked issues.
func SafeCommand(name string, arg ...string) (*exec.Cmd, error) {
bin, err := safeexec.LookPath(name)
if err != nil {
return nil, err
}
return exec.Command(bin, arg...), nil
}
// Exec encorces a security policy for commands run via os/exec.
type Exec struct {
sc security.Config
// os.Environ filtered by the Exec.OsEnviron whitelist filter.
baseEnviron []string
}
// New will fail if name is not allowed according to the configured security policy.
// Else a configured Runner will be returned ready to be Run.
func (e *Exec) New(name string, arg ...interface{}) (Runner, error) {
if err := e.sc.CheckAllowedExec(name); err != nil {
return nil, err
}
env := make([]string, len(e.baseEnviron))
copy(env, e.baseEnviron)
cm := &commandeer{
name: name,
env: env,
}
return cm.command(arg...)
}
// Npx is a convenience method to create a Runner running npx --no-install <name> <args.
func (e *Exec) Npx(name string, arg ...interface{}) (Runner, error) {
arg = append(arg[:0], append([]interface{}{"--no-install", name}, arg[0:]...)...)
return e.New("npx", arg...)
}
// Sec returns the security policies this Exec is configured with.
func (e *Exec) Sec() security.Config {
return e.sc
}
type NotFoundError struct {
name string
}
func (e *NotFoundError) Error() string {
return fmt.Sprintf("binary with name %q not found", e.name)
}
// Runner wraps a *os.Cmd.
type Runner interface {
Run() error
StdinPipe() (io.WriteCloser, error)
}
type cmdWrapper struct {
name string
c *exec.Cmd
outerr *bytes.Buffer
}
var notFoundRe = regexp.MustCompile(`(?s)not found:|could not determine executable`)
func (c *cmdWrapper) Run() error {
err := c.c.Run()
if err == nil {
return nil
}
if notFoundRe.MatchString(c.outerr.String()) {
return &NotFoundError{name: c.name}
}
return fmt.Errorf("failed to execute binary %q with args %v: %s", c.name, c.c.Args[1:], c.outerr.String())
}
func (c *cmdWrapper) StdinPipe() (io.WriteCloser, error) {
return c.c.StdinPipe()
}
type commandeer struct {
stdout io.Writer
stderr io.Writer
stdin io.Reader
dir string
ctx context.Context
name string
env []string
}
func (c *commandeer) command(arg ...interface{}) (*cmdWrapper, error) {
if c == nil {
return nil, nil
}
var args []string
for _, a := range arg {
switch v := a.(type) {
case string:
args = append(args, v)
case func(*commandeer):
v(c)
default:
return nil, fmt.Errorf("invalid argument to command: %T", a)
}
}
bin, err := safeexec.LookPath(c.
|