webdav/xml.go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package webdav

// The XML encoding is covered by Section 14.
// http://www.webdav.org/specs/rfc4918.html#xml.element.definitions

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"time"
)

// http://www.webdav.org/specs/rfc4918.html#ELEMENT_lockinfo
type lockInfo struct {
	XMLName   xml.Name  `xml:"lockinfo"`
	Exclusive *struct{} `xml:"lockscope>exclusive"`
	Shared    *struct{} `xml:"lockscope>shared"`
	Write     *struct{} `xml:"locktype>write"`
	Owner     owner     `xml:"owner"`
}

// http://www.webdav.org/specs/rfc4918.html#ELEMENT_owner
type owner struct {
	InnerXML string `xml:",innerxml"`
}

func readLockInfo(r io.Reader) (li lockInfo, status int, err error) {
	c := &countingReader{r: r}
	if err = xml.NewDecoder(c).Decode(&li); err != nil {
		if err == io.EOF {
			if c.n == 0 {
				// An empty body means to refresh the lock.
				// http://www.webdav.org/specs/rfc4918.html#refreshing-locks
				return lockInfo{}, 0, nil
			}
			err = errInvalidLockInfo
		}
		return lockInfo{}, http.StatusBadRequest, err
	}
	// We only support exclusive (non-shared) write locks. In practice, these are
	// the only types of locks that seem to matter.
	if li.Exclusive == nil || li.Shared != nil || li.Write == nil {
		return lockInfo{}, http.StatusNotImplemented, errUnsupportedLockInfo
	}
	return li, 0, nil
}

type countingReader struct {
	n int
	r io.Reader
}

func (c *countingReader) Read(p []byte) (int, error) {
	n, err := c.r.Read(p)
	c.n += n
	return n, err
}

func writeLockInfo(w io.Writer, token string, ld LockDetails) (int, error) {
	depth := "infinity"
	if ld.ZeroDepth {
		depth = "0"
	}
	timeout := ld.Duration / time.Second
	return fmt.Fprintf(w, "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"+
		"<D:prop xmlns:D=\"DAV:\"><D:lockdiscovery><D:activelock>\n"+
		"	<D:locktype><D:write/></D:locktype>\n"+
		"	<D:lockscope><D:exclusive/></D:lockscope>\n"+
		"	<D:depth>%s</D:depth>\n"+
		"	<D:owner>%s</D:owner>\n"+
		"	<D:timeout>Second-%d</D:timeout>\n"+
		"	<D:locktoken><D:href>%s</D:href></D:locktoken>\n"+
		"	<D:lockroot><D:href>%s</D:href></D:lockroot>\n"+
		"</D:activelock></D:lockdiscovery></D:prop>",
		depth, ld.OwnerXML, timeout, escape(token), escape(ld.Root),
	)
}

func escape(s string) string {
	for i := 0; i < len(s); i++ {
		switch s[i] {
		case '"', '&', '\'', '<', '>':
			b := bytes.NewBuffer(nil)
			xml.EscapeText(b, []byte(s))
			return b.String()
		}
	}
	return s
}

// Next returns the next token, if any, in the XML stream of d.
// RFC 4918 requires to ignore comments, processing instructions
// and directives.
// http://www.webdav.org/specs/rfc4918.html#property_values
// http://www.webdav.org/specs/rfc4918.html#xml-extensibility
func next(d *xml.Decoder) (xml.Token, error) {
	for {
		t, err := d.Token()
		if err != nil {
			return t, err
		}
		switch t.(type) {
		case xml.Comment, xml.Directive, xml.ProcInst:
			continue
		default:
			return t, nil
		}
	}
}

type propnames []xml.Name

// UnmarshalXML appends the property names enclosed within start to pn.
//
// It returns an error if start does not contain any properties or if
// properties contain values. Character data between properties is ignored.
func (pn *propnames) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	for {
		t, err := next(d)
		if err != nil {
			return err
		}
		switch t.(type) {
		case xml.EndElement:
			if len(*pn) == 0 {
				return fmt.Errorf("%s must not be empty", start.Name.Local)
			}
			return nil
		case xml.StartElement:
			name := t.(xml.StartElement).Name
			t, err = next(d)
			if err != nil {
				return err
			}
			if _, ok := t.(xml.EndElement); !ok {
				return fmt.Errorf("unexpected token %T", t)
			}
			*pn = append(*pn, name)
		}
	}
}

// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propfind
type propfind struct {
	XMLName  xml.Name  `xml:"DAV: propfind"`
	Allprop  *struct{} `xml:"DAV: allprop"`
	Propname *struct{} `xml:"DAV: propname"`
	Prop     propnames `xml:"DAV: prop"`
	Include  propnames `xml:"DAV: include"`
}

func readPropfind(r io.Reader) (pf propfind, status int, err error) {
	c := countingReader{r: r}
	if err = xml.NewDecoder(&c).Decode(&pf); err != nil {
		if err == io.EOF {
			if c.n == 0 {
				// An empty body means to propfind allprop.
				// http://www.webdav.org/specs/rfc4918.html#METHOD_PROPFIND
				return propfind{Allprop: new(struct{})}, 0, nil
			}
			err = errInvalidPropfind
		}
		return propfind{}, http.StatusBadRequest, err
	}

	if pf.Allprop == nil && pf.Include != nil {
		return propfind{}, http.StatusBadRequest, errInvalidPropfind
	}
	if pf.Allprop != nil && (pf.Prop != nil || pf.Propname != nil) {
		return propfind{}, http.StatusBadRequest, errInvalidPropfind
	}
	if pf.Prop != nil && pf.Propname != nil {
		return propfind{}, http.StatusBadRequest, errInvalidPropfind
	}
	if pf.Propname == nil && pf.Allprop == nil && pf.Prop == nil {
		return propfind{}, http.StatusBadRequest, errInvalidPropfind
	}
	return pf, 0, nil
}