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// Copyright 2010 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 multipart implements MIME multipart parsing, as defined in RFC
2046.
The implementation is sufficient for HTTP (RFC 2388) and the multipart
bodies generated by popular browsers.
*/
package multipart
import (
"bufio"
"bytes"
"fmt"
"io"
"io/ioutil"
"mime"
"net/textproto"
)
var emptyParams = make(map[string]string)
// A Part represents a single part in a multipart body.
type Part struct {
// The headers of the body, if any, with the keys canonicalized
// in the same fashion that the Go http.Request headers are.
// For example, "foo-bar" changes case to "Foo-Bar"
//
// As a special case, if the "Content-Transfer-Encoding" header
// has a value of "quoted-printable", that header is instead
// hidden from this map and the body is transparently decoded
// during Read calls.
Header textproto.MIMEHeader
buffer *bytes.Buffer
mr *Reader
bytesRead int
disposition string
dispositionParams map[string]string
// r is either a reader directly reading from mr, or it's a
// wrapper around such a reader, decoding the
// Content-Transfer-Encoding
r io.Reader
}
// FormName returns the name parameter if p has a Content-Disposition
// of type "form-data". Otherwise it returns the empty string.
func (p *Part) FormName() string {
// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
// of Content-Disposition value format.
if p.dispositionParams == nil {
p.parseContentDisposition()
}
if p.disposition != "form-data" {
return ""
}
return p.dispositionParams["name"]
}
// FileName returns the filename parameter of the Part's
// Content-Disposition header.
func (p *Part) FileName() string {
if p.dispositionParams == nil {
p.parseContentDisposition()
}
return p.dispositionParams["filename"]
}
func (p *Part) parseContentDisposition() {
v := p.Header.Get("Content-Disposition")
var err error
p.disposition, p.dispositionParams, err = mime.ParseMediaType(v)
if err != nil {
p.dispositionParams = emptyParams
}
}
// NewReader creates a new multipart Reader reading from reader using the
// given MIME boundary.
func NewReader(reader io.Reader, boundary string) *Reader {
b := []byte("\r\n--" + boundary + "--")
return &Reader{
bufReader: bufio.NewReader(reader),
nl: b[:2],
nlDashBoundary: b[:len(b)-2],
dashBoundaryDash: b[2:],
dashBoundary: b[2 : len(b)-2],
}
}
func newPart(mr *Reader) (*Part, error) {
bp := &Part{
Header: make(map[string][]string),
mr: mr,
buffer: new(bytes.Buffer),
}
if err := bp.populateHeaders(); err != nil {
return nil, err
}
bp.r = partReader{bp}
const cte = "Content-Transfer-Encoding"
if bp.Header.Get(cte) == "quoted-printable" {
bp.Header.Del(cte)
bp.r = newQuotedPrintableReader(bp.r)
}
return bp, nil
}
func (bp *Part) populateHeaders() error {
r := textproto.NewReader(bp.mr.bufReader)
header, err := r.ReadMIMEHeader()
if err == nil {
bp.Header = header
}
return err
}
// Read reads the body of a part, after its headers and before the
// next part (if any) begins.
func (p *Part) Read(d []byte) (n int, err error) {
return p.r.Read(d)
}
// partReader implements io.Reader by reading raw bytes directly from the
// wrapped *Part, without doing any Transfer-Encoding decoding.
type partReader struct {
p *Part
}
func (pr partReader) Read(d []byte) (n int, err error) {
p := pr.p
defer func() {
p.bytesRead += n
}()
if p.buffer.Len() >= len(d) {
// Internal buffer of unconsumed data is large enough for
// the read request. No need to parse more at the moment.
return p.buffer.Read(d)
}
peek, err := p.mr.bufReader.Peek(4096) // TODO(bradfitz): add buffer size accessor
// Look for an immediate empty part without a leading \r\n
// before the boundary separator. Some MIME code makes empty
// parts like this. Most browsers, however, write the \r\n
// before the subsequent boundary even for empty parts and
// won't hit this path.
if p.bytesRead == 0 && p.mr.peekBufferIsEmptyPart(peek) {
return 0, io.EOF
}
unexpectedEOF := err == io.EOF
if err != nil && !unexpectedEOF {
return 0, fmt.Errorf("multipart: Part Read: %v", err)
}
if peek == nil {
panic("nil peek buf")
}
// Search the peek buffer for "\r\n--boundary". If found,
// consume everything up to the boundary. If not, consume only
// as much of the peek buffer as cannot hold the boundary
// string.
nCopy := 0
foundBoundary := false
if idx := bytes.Index(peek, p.mr.nlDashBoundary); idx != -1 {
nCopy = idx
foundBoundary = true
} else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
nCopy = safeCount
} else if unexpectedEOF {
// If we've run out of peek buffer and the boundary
// wasn't found (and can't possibly fit), we must have
// hit the end of the file unexpectedly.
return 0, io.ErrUnexpectedEOF
}
if nCopy > 0 {
if _, err := io.CopyN(p.buffer, p.mr.bufReader, int64(nCopy)); err != nil {
return 0, err
}
}
n, err = p.buffer.Read(d)
if err == io.EOF && !foundBoundary {
// If the boundary hasn't been reached there's more to
// read, so don't pass through an EOF from the buffer
err = nil
}
return
}
func (p *Part) Close() error {
io.Copy(ioutil.Discard, p)
return nil
}
// Reader is an iterator over parts in a MIME multipart body.
// Reader's underlying parser consumes its input as needed. Seeking
// isn't supported.
type Reader struct {
bufReader *bufio.Reader
currentPart *Part
partsRead int
nl []byte // "\r\n" or "\n" (set after seeing first boundary line)
nlDashBoundary []byte // nl + "--boundary"
dashBoundaryDash []byte // "--boundary--"
dashBoundary []byte // "--boundary"
}
// NextPart returns the next part in the multipart or an error.
// When there are no more parts, the error io.EOF is returned.
func (r *Reader) NextPart() (*Part, error) {
if r.currentPart != nil {
r.currentPart.Close()
}
expectNewPart := false
for {
line, err := r.bufReader.ReadSlice('\n')
if err == io.EOF && r.isFinalBoundary(line) {
// If the buffer ends in "--boundary--" without the
// trailing "\r\n", ReadSlice will return an error
// (since it's missing the '\n'), but this is a valid
// multipart EOF so we need to return io.EOF instead of
// a fmt-wrapped one.
return nil, io.EOF
}
if err != nil {
return nil, fmt.Errorf("multipart: NextPart: %v", err)
}
if r.isBoundaryDelimiterLine(line) {
r.partsRead++
bp, err := newPart(r)
if err != nil {
return nil, err
}
r.currentPart = bp
return bp, nil
}
if r.isFinalBoundary(line) {
// Expected EOF
return nil, io.EOF
}
if expectNewPart {
return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
}
if r.partsRead == 0 {
// skip line
continue
}
// Consume the "\n" or "\r\n" separator between the
// body of the previous part and the boundary line we
// now expect will follow. (either a new part or the
// end boundary)
if bytes.Equal(line, r.nl) {
expectNewPart = true
continue
}
return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
}
}
// isFinalBoundary reports whether line is the final boundary line
// indicating that all parts are over.
// It matches `^--boundary--[ \t]*(\r\n)?$`
func (mr *Reader) isFinalBoundary(line []byte) bool {
if !bytes.HasPrefix(line, mr.dashBoundaryDash) {
return false
}
rest := line[len(mr.dashBoundaryDash):]
rest = skipLWSPChar(rest)
return len(rest) == 0 || bytes.Equal(rest, mr.nl)
}
func (mr *Reader) isBoundaryDelimiterLine(line []byte) (ret bool) {
// http://tools.ietf.org/html/rfc2046#section-5.1
// The boundary delimiter line is then defined as a line
// consisting entirely of two hyphen characters ("-",
// decimal value 45) followed by the boundary parameter
// value from the Content-Type header field, optional linear
// whitespace, and a terminating CRLF.
if !bytes.HasPrefix(line, mr.dashBoundary) {
return false
}
rest := line[len(mr.dashBoundary):]
rest = skipLWSPChar(rest)
// On the first part, see our lines are ending in \n instead of \r\n
// and switch into that mode if so. This is a violation of the spec,
// but occurs in practice.
if mr.partsRead == 0 && len(rest) == 1 && rest[0] == '\n' {
mr.nl = mr.nl[1:]
mr.nlDashBoundary = mr.nlDashBoundary[1:]
}
return bytes.Equal(rest, mr.nl)
}
// peekBufferIsEmptyPart reports whether the provided peek-ahead
// buffer represents an empty part. It is called only if we've not
// already read any bytes in this part and checks for the case of MIME
// software not writing the \r\n on empty parts. Some does, some
// doesn't.
//
// This checks that what follows the "--boundary" is actually the end
// ("--boundary--" with optional whitespace) or optional whitespace
// and then a newline, so we don't catch "--boundaryFAKE", in which
// case the whole line is part of the data.
func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
// End of parts case.
// Test whether peek matches `^--boundary--[ \t]*(?:\r\n|$)`
if bytes.HasPrefix(peek, mr.dashBoundaryDash) {
rest := peek[len(mr.dashBoundaryDash):]
rest = skipLWSPChar(rest)
return bytes.HasPrefix(rest, mr.nl) || len(rest) == 0
}
if !bytes.HasPrefix(peek, mr.dashBoundary) {
return false
}
// Test whether rest matches `^[ \t]*\r\n`)
rest := peek[len(mr.dashBoundary):]
rest = skipLWSPChar(rest)
return bytes.HasPrefix(rest, mr.nl)
}
// skipLWSPChar returns b with leading spaces and tabs removed.
// RFC 822 defines:
// LWSP-char = SPACE / HTAB
func skipLWSPChar(b []byte) []byte {
for len(b) > 0 && (b[0] == ' ' || b[0] == '\t') {
b = b[1:]
}
return b
}