// Download and write files atomically to the file system
-// Copyright (C) 2019 Simon Ruderich
+// Copyright (C) 2019-2021 Simon Ruderich
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
import (
"bytes"
+ "crypto/sha512"
+ "encoding/hex"
"fmt"
"io/ioutil"
"log"
"os"
"path/filepath"
"syscall"
+ "time"
+ "github.com/google/renameio"
"github.com/pkg/errors"
)
return nil
}
+func checksumFile(file *File) (string, error) {
+ x, err := ioutil.ReadFile(file.Path)
+ if err != nil {
+ return "", err
+ }
+ return checksumBytes(x), nil
+}
+
+func checksumBytes(x []byte) string {
+ h := sha512.New()
+ h.Write(x)
+ return hex.EncodeToString(h.Sum(nil))
+}
+
func fetchFile(file *File, state *State) error {
t := state.LastModified[file.Url]
- status, body, err := fetchIfModified(file.Url, &t)
+
+ hash, err := checksumFile(file)
+ if err != nil {
+ // See below in deployFile() for the reason
+ return errors.Wrapf(err, "file.path %q must exist", file.Path)
+ }
+ if hash != state.Checksum[file.Url] {
+ log.Printf("%q -> %q: hash has changed", file.Url, file.Path)
+ var zero time.Time
+ t = zero // force download
+ }
+
+ oldT := t
+ status, body, err := fetchIfModified(file.Url,
+ file.Username, file.Password, file.CA, &t)
if err != nil {
return err
}
if status == http.StatusNotModified {
+ if oldT.IsZero() {
+ return fmt.Errorf("status code 304 " +
+ "but did not send If-Modified-Since")
+ }
log.Printf("%q -> %q: not modified", file.Url, file.Path)
return nil
}
} else {
return fmt.Errorf("unsupported file type %v", file.Type)
}
+
+ state.Checksum[file.Url] = checksumBytes(file.body)
return nil
}
return fmt.Errorf("refusing to write empty file")
}
- // Write the file in an atomic fashion by creating a temporary file
- // and renaming it over the target file
-
- dir := filepath.Dir(file.Path)
- name := filepath.Base(file.Path)
-
- f, err := ioutil.TempFile(dir, "tmp-"+name+"-")
+ f, err := renameio.TempFile(filepath.Dir(file.Path), file.Path)
if err != nil {
return err
}
- defer os.Remove(f.Name())
- defer f.Close()
+ defer f.Cleanup()
- // Apply permissions/user/group from the target file, use Stat instead
- // of Lstat as only the target's permissions are relevant
+ // Apply permissions/user/group from the target file but remove the
+ // write permissions to discourage manual modifications, use Stat
+ // instead of Lstat as only the target's permissions are relevant
stat, err := os.Stat(file.Path)
if err != nil {
// We do not create the path if it doesn't exist, because we
// do not know the proper permissions
return errors.Wrapf(err, "file.path %q must exist", file.Path)
}
- err = f.Chmod(stat.Mode())
+ err = f.Chmod(stat.Mode() & ^os.FileMode(0222)) // remove write perms
if err != nil {
return err
}
if err != nil {
return err
}
- err = f.Sync()
+ err = f.CloseAtomicallyReplace()
if err != nil {
return err
}
- return os.Rename(f.Name(), file.Path)
+ return syncPath(filepath.Dir(file.Path))
}