X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/654ee9154fe85832a0862c27fd7b982831a75a0d..b39f7a6141ecd5c53531b7705c0496623b4df9e9:/services/keep-web/webdav.go?ds=sidebyside

diff --git a/services/keep-web/webdav.go b/services/keep-web/webdav.go
index 1b5811dad7..a7b7980995 100644
--- a/services/keep-web/webdav.go
+++ b/services/keep-web/webdav.go
@@ -5,58 +5,194 @@
 package main
 
 import (
+	"crypto/rand"
 	"errors"
-	"net/http"
+	"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 errReadOnly = errors.New("read-only filesystem")
+var (
+	lockPrefix     string = uuid()
+	nextLockSuffix int64  = prand.Int63()
+	errReadOnly           = errors.New("read-only filesystem")
+)
 
-// webdavFS implements a read-only webdav.FileSystem by wrapping
-// http.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 {
-	httpfs http.FileSystem
+	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
 }
 
-var _ webdav.FileSystem = &webdavFS{}
+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 {
-	return errReadOnly
+	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) (webdav.File, error) {
-	f, err := fs.httpfs.Open(name)
-	if err != nil {
-		return nil, err
+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}
 	}
-	return &webdavFile{File: f}, nil
+	if fs.alwaysReadEOF {
+		f = readEOF{File: f}
+	}
+	return
 }
 
 func (fs *webdavFS) RemoveAll(ctx context.Context, name string) error {
-	return errReadOnly
+	return fs.collfs.RemoveAll(name)
 }
 
 func (fs *webdavFS) Rename(ctx context.Context, oldName, newName string) error {
-	return errReadOnly
+	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 f, err := fs.httpfs.Open(name); err != nil {
-		return nil, err
-	} else {
-		return f.Stat()
+	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
 }
 
-// webdavFile implements a read-only webdav.File by wrapping
-// http.File. Writes fail.
-type webdavFile struct {
-	http.File
+func (*noLockSystem) Refresh(now time.Time, token string, duration time.Duration) (webdav.LockDetails, error) {
+	return webdav.LockDetails{}, nil
 }
 
-func (f *webdavFile) Write([]byte) (int, error) {
-	return 0, errReadOnly
+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:])
 }