// Copyright (C) The Arvados Authors. All rights reserved. // // SPDX-License-Identifier: AGPL-3.0 package keepweb import ( "crypto/rand" "errors" "fmt" "io" prand "math/rand" "os" "path" "strings" "sync/atomic" "time" "git.arvados.org/arvados.git/sdk/go/arvados" "golang.org/x/net/context" "golang.org/x/net/webdav" ) var ( lockPrefix string = uuid() nextLockSuffix int64 = prand.Int63() errReadOnly = errors.New("read-only filesystem") ) // webdavFS implements a webdav.FileSystem by wrapping an // arvados.CollectionFilesystem. // // Collections don't preserve empty directories, so Mkdir is // effectively a no-op, and we need to make parent dirs spring into // existence automatically so sequences like "mkcol foo; put foo/bar" // work as expected. type webdavFS struct { collfs arvados.FileSystem writing bool // webdav PROPFIND reads the first few bytes of each file // whose filename extension isn't recognized, which is // prohibitively expensive: we end up fetching multiple 64MiB // blocks. Avoid this by returning EOF on all reads when // handling a PROPFIND. alwaysReadEOF bool } func (fs *webdavFS) makeparents(name string) { if !fs.writing { return } dir, _ := path.Split(name) if dir == "" || dir == "/" { return } dir = dir[:len(dir)-1] fs.makeparents(dir) fs.collfs.Mkdir(dir, 0755) } func (fs *webdavFS) Mkdir(ctx context.Context, name string, perm os.FileMode) error { if !fs.writing { return errReadOnly } name = strings.TrimRight(name, "/") fs.makeparents(name) return fs.collfs.Mkdir(name, 0755) } func (fs *webdavFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (f webdav.File, err error) { writing := flag&(os.O_WRONLY|os.O_RDWR|os.O_TRUNC) != 0 if writing { fs.makeparents(name) } f, err = fs.collfs.OpenFile(name, flag, perm) if !fs.writing { // webdav module returns 404 on all OpenFile errors, // but returns 405 Method Not Allowed if OpenFile() // succeeds but Write() or Close() fails. We'd rather // have 405. writeFailer ensures Close() fails if the // file is opened for writing *or* Write() is called. var err error if writing { err = errReadOnly } f = writeFailer{File: f, err: err} } if fs.alwaysReadEOF { f = readEOF{File: f} } return } func (fs *webdavFS) RemoveAll(ctx context.Context, name string) error { return fs.collfs.RemoveAll(name) } func (fs *webdavFS) Rename(ctx context.Context, oldName, newName string) error { if !fs.writing { return errReadOnly } if strings.HasSuffix(oldName, "/") { // WebDAV "MOVE foo/ bar/" means rename foo to bar. oldName = oldName[:len(oldName)-1] newName = strings.TrimSuffix(newName, "/") } fs.makeparents(newName) return fs.collfs.Rename(oldName, newName) } func (fs *webdavFS) Stat(ctx context.Context, name string) (os.FileInfo, error) { if fs.writing { fs.makeparents(name) } return fs.collfs.Stat(name) } type writeFailer struct { webdav.File err error } func (wf writeFailer) Write([]byte) (int, error) { wf.err = errReadOnly return 0, wf.err } func (wf writeFailer) Close() error { err := wf.File.Close() if err != nil { wf.err = err } return wf.err } type readEOF struct { webdav.File } func (readEOF) Read(p []byte) (int, error) { return 0, io.EOF } // noLockSystem implements webdav.LockSystem by returning success for // every possible locking operation, even though it has no side // effects such as actually locking anything. This works for a // read-only webdav filesystem because webdav locks only apply to // writes. // // This is more suitable than webdav.NewMemLS() for two reasons: // First, it allows keep-web to use one locker for all collections // even though coll1.vhost/foo and coll2.vhost/foo have the same path // but represent different resources. Additionally, it returns valid // tokens (rfc2518 specifies that tokens are represented as URIs and // are unique across all resources for all time), which might improve // client compatibility. // // However, it does also permit impossible operations, like acquiring // conflicting locks and releasing non-existent locks. This might // confuse some clients if they try to probe for correctness. // // Currently this is a moot point: the LOCK and UNLOCK methods are not // accepted by keep-web, so it suffices to implement the // webdav.LockSystem interface. type noLockSystem struct{} func (*noLockSystem) Confirm(time.Time, string, string, ...webdav.Condition) (func(), error) { return noop, nil } func (*noLockSystem) Create(now time.Time, details webdav.LockDetails) (token string, err error) { return fmt.Sprintf("opaquelocktoken:%s-%x", lockPrefix, atomic.AddInt64(&nextLockSuffix, 1)), nil } func (*noLockSystem) Refresh(now time.Time, token string, duration time.Duration) (webdav.LockDetails, error) { return webdav.LockDetails{}, nil } func (*noLockSystem) Unlock(now time.Time, token string) error { return nil } func noop() {} // Return a version 1 variant 4 UUID, meaning all bits are random // except the ones indicating the version and variant. func uuid() string { var data [16]byte if _, err := rand.Read(data[:]); err != nil { panic(err) } // variant 1: N=10xx data[8] = data[8]&0x3f | 0x80 // version 4: M=0100 data[6] = data[6]&0x0f | 0x40 return fmt.Sprintf("%x-%x-%x-%x-%x", data[0:4], data[4:6], data[6:8], data[8:10], data[10:]) }