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file.go
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file.go
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// Copyright 2015 CoreOS, Inc.
//
// 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 util
import (
"encoding/hex"
"fmt"
"hash"
"io"
"io/ioutil"
"net/http"
"net/url"
"os"
"path/filepath"
"strconv"
"syscall"
"github.com/coreos/ignition/internal/config/types"
"github.com/coreos/ignition/internal/log"
"github.com/coreos/ignition/internal/resource"
"github.com/coreos/ignition/internal/util"
)
const (
DefaultDirectoryPermissions os.FileMode = 0755
DefaultFilePermissions os.FileMode = 0644
)
type FetchOp struct {
Hash hash.Hash
Path string
Url url.URL
Mode *int
FetchOptions resource.FetchOptions
Overwrite *bool
Append bool
Node types.Node
}
// newHashedReader returns a new ReadCloser that also writes to the provided hash.
func newHashedReader(reader io.ReadCloser, hasher hash.Hash) io.ReadCloser {
return struct {
io.Reader
io.Closer
}{
Reader: io.TeeReader(reader, hasher),
Closer: reader,
}
}
// PrepareFetch converts a given logger, http client, and types.File into a
// FetchOp. This includes operations such as parsing the source URL, generating
// a hasher, and performing user/group name lookups. If an error is encountered,
// the issue will be logged and nil will be returned.
func (u Util) PrepareFetch(l *log.Logger, f types.File) *FetchOp {
var err error
var expectedSum []byte
// explicitly ignoring the error here because the config should already be
// validated by this point
uri, _ := url.Parse(f.Contents.Source)
hasher, err := util.GetHasher(f.Contents.Verification)
if err != nil {
l.Crit("Error verifying file %q: %v", f.Path, err)
return nil
}
if hasher != nil {
// explicitly ignoring the error here because the config should already
// be validated by this point
_, expectedSumString, _ := util.HashParts(f.Contents.Verification)
expectedSum, err = hex.DecodeString(expectedSumString)
if err != nil {
l.Crit("Error parsing verification string %q: %v", expectedSumString, err)
return nil
}
}
var headers http.Header
if f.Contents.HTTPHeaders != nil && len(f.Contents.HTTPHeaders) > 0 {
headers, err = f.Contents.HTTPHeaders.Parse()
if err != nil {
l.Crit("error parsing http headers: %v", err)
return nil
}
}
return &FetchOp{
Path: f.Path,
Hash: hasher,
Node: f.Node,
Url: *uri,
Mode: f.Mode,
Overwrite: f.Overwrite,
Append: f.Append,
FetchOptions: resource.FetchOptions{
Hash: hasher,
Compression: f.Contents.Compression,
ExpectedSum: expectedSum,
Headers: headers,
},
}
}
func (u Util) WriteLink(s types.Link) error {
path, err := u.JoinPath(s.Path)
if err != nil {
return err
}
if err := MkdirForFile(path); err != nil {
return err
}
if s.Hard {
targetPath, err := u.JoinPath(s.Target)
if err != nil {
return err
}
return os.Link(targetPath, path)
}
if err := os.Symlink(s.Target, path); err != nil {
return err
}
uid, gid, err := u.ResolveNodeUidAndGid(s.Node, 0, 0)
if err != nil {
return err
}
if err := os.Lchown(path, uid, gid); err != nil {
return err
}
return nil
}
// PerformFetch performs a fetch operation generated by PrepareFetch, retrieving
// the file and writing it to disk. Any encountered errors are returned.
func (u Util) PerformFetch(f *FetchOp) error {
path, err := u.JoinPath(string(f.Path))
if err != nil {
return err
}
if f.Overwrite != nil && *f.Overwrite == false {
// Both directories and links will fail to be created if the target path
// already exists. Because files are downloaded into a temporary file
// and then renamed to the target path, we don't have the same
// guarantees here. If the user explicitly doesn't want us to overwrite
// preexisting nodes, check the target path and fail if something's
// there.
_, err := os.Lstat(path)
switch {
case os.IsNotExist(err):
break
case err != nil:
return err
default:
return fmt.Errorf("error creating %q: something else exists at that path", f.Path)
}
}
if f.Overwrite == nil && !f.Append {
// For files, overwrite defaults to true if append is false. If
// overwrite wasn't specified, delete the path.
err := os.RemoveAll(path)
if err != nil {
return err
}
}
if err := MkdirForFile(path); err != nil {
return err
}
// Create a temporary file in the same directory to ensure it's on the same filesystem
var tmp *os.File
if tmp, err = ioutil.TempFile(filepath.Dir(path), "tmp"); err != nil {
return err
}
defer tmp.Close()
// sometimes the following line will fail (the file might be renamed),
// but that's ok (we wanted to keep the file in that case).
defer os.Remove(tmp.Name())
err = u.Fetcher.Fetch(f.Url, tmp, f.FetchOptions)
if err != nil {
u.Crit("Error fetching file %q: %v", f.Path, err)
return err
}
if f.Append {
// Make sure that we're appending to a file
finfo, err := os.Lstat(path)
switch {
case os.IsNotExist(err):
// No problem, we'll create it.
break
case err != nil:
return err
default:
if !finfo.Mode().IsRegular() {
return fmt.Errorf("can only append to files: %q", f.Path)
}
}
// Default to the appended file's owner for the uid and gid
defaultUid, defaultGid, mode := getFileOwnerAndMode(path)
uid, gid, err := u.ResolveNodeUidAndGid(f.Node, defaultUid, defaultGid)
if err != nil {
return err
}
if f.Mode != nil {
mode = os.FileMode(*f.Mode)
}
targetFile, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, mode)
if err != nil {
return err
}
defer targetFile.Close()
if _, err = tmp.Seek(0, os.SEEK_SET); err != nil {
return err
}
if _, err = io.Copy(targetFile, tmp); err != nil {
return err
}
if err = os.Chown(targetFile.Name(), uid, gid); err != nil {
return err
}
if err = os.Chmod(targetFile.Name(), mode); err != nil {
return err
}
} else {
// XXX(vc): Note that we assume to be operating on the file we just wrote, this is only guaranteed
// by using syscall.Fchown() and syscall.Fchmod()
// Ensure the ownership and mode are as requested (since WriteFile can be affected by sticky bit)
mode := os.FileMode(0)
if f.Mode != nil {
mode = os.FileMode(*f.Mode)
}
uid, gid, err := u.ResolveNodeUidAndGid(f.Node, 0, 0)
if err != nil {
return err
}
if err = os.Chown(tmp.Name(), uid, gid); err != nil {
return err
}
if err = os.Chmod(tmp.Name(), mode); err != nil {
return err
}
if err = os.Rename(tmp.Name(), path); err != nil {
return err
}
}
return nil
}
// MkdirForFile helper creates the directory components of path.
func MkdirForFile(path string) error {
return os.MkdirAll(filepath.Dir(path), DefaultDirectoryPermissions)
}
// PathExists returns true if a node exists within DestDir, false otherwise. Any
// error other than ENOENT is treated as fatal.
func (u Util) PathExists(path string) (bool, error) {
path, err := u.JoinPath(path)
if err != nil {
return false, err
}
_, err = os.Lstat(path)
switch {
case os.IsNotExist(err):
return false, nil
case err != nil:
return false, err
default:
return true, nil
}
}
// getFileOwner will return the uid and gid for the file at a given path. If the
// file doesn't exist, or some other error is encountered when running stat on
// the path, 0, 0, and 0 will be returned.
func getFileOwnerAndMode(path string) (int, int, os.FileMode) {
finfo, err := os.Stat(path)
if err != nil {
return 0, 0, 0
}
return int(finfo.Sys().(*syscall.Stat_t).Uid), int(finfo.Sys().(*syscall.Stat_t).Gid), finfo.Mode()
}
// ResolveNodeUidAndGid attempts to convert a types.Node into a concrete uid and
// gid. If the node has the User.ID field set, that's used for the uid. If the
// node has the User.Name field set, a username -> uid lookup is performed. If
// neither are set, it returns the passed in defaultUid. The logic is identical
// for gids with equivalent fields.
func (u Util) ResolveNodeUidAndGid(n types.Node, defaultUid, defaultGid int) (int, int, error) {
var err error
uid, gid := defaultUid, defaultGid
if n.User != nil {
if n.User.ID != nil {
uid = *n.User.ID
} else if n.User.Name != "" {
uid, err = u.getUserID(n.User.Name)
if err != nil {
return 0, 0, err
}
}
}
if n.Group != nil {
if n.Group.ID != nil {
gid = *n.Group.ID
} else if n.Group.Name != "" {
gid, err = u.getGroupID(n.Group.Name)
if err != nil {
return 0, 0, err
}
}
}
return uid, gid, nil
}
func (u Util) getUserID(name string) (int, error) {
usr, err := u.userLookup(name)
if err != nil {
return 0, fmt.Errorf("No such user %q: %v", name, err)
}
uid, err := strconv.ParseInt(usr.Uid, 0, 0)
if err != nil {
return 0, fmt.Errorf("Couldn't parse uid %q: %v", usr.Uid, err)
}
return int(uid), nil
}
func (u Util) getGroupID(name string) (int, error) {
g, err := u.groupLookup(name)
if err != nil {
return 0, fmt.Errorf("No such group %q: %v", name, err)
}
gid, err := strconv.ParseInt(g.Gid, 0, 0)
if err != nil {
return 0, fmt.Errorf("Couldn't parse gid %q: %v", g.Gid, err)
}
return int(gid), nil
}
func (u Util) DeletePathOnOverwrite(n types.Node) error {
if n.Overwrite == nil || !*n.Overwrite {
return nil
}
path, err := u.JoinPath(string(n.Path))
if err != nil {
return err
}
return os.RemoveAll(path)
}