src/encoding/pem/pem.go - go - Git at Google

 // Copyright 2009 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 pem implements the PEM data encoding, which originated in Privacy
 // Enhanced Mail. The most common use of PEM encoding today is in TLS keys and
 // certificates. See RFC 1421.
 package pem

 import (
 	"bytes"
 	"encoding/base64"
 	"errors"
 	"io"
 	"sort"
 	"strings"
 )

 // A Block represents a PEM encoded structure.
 //
 // The encoded form is:
 //    -----BEGIN Type-----
 //    Headers
 //    base64-encoded Bytes
 //    -----END Type-----
 // where Headers is a possibly empty sequence of Key: Value lines.
 type Block struct {
 	Type    string            // The type, taken from the preamble (i.e. "RSA PRIVATE KEY").
 	Headers map[string]string // Optional headers.
 	Bytes   []byte            // The decoded bytes of the contents. Typically a DER encoded ASN.1 structure.
 }

 // getLine results the first \r\n or \n delineated line from the given byte
 // array. The line does not include trailing whitespace or the trailing new
 // line bytes. The remainder of the byte array (also not including the new line
 // bytes) is also returned and this will always be smaller than the original
 // argument.
 func getLine(data []byte) (line, rest []byte) {
 	i := bytes.IndexByte(data, '\n')
 	var j int
 	if i < 0 {
 		i = len(data)
 		j = i
 	} else {
 		j = i + 1
 		if i > 0 && data[i-1] == '\r' {
 			i--
 		}
 	}
 	return bytes.TrimRight(data[0:i], " \t"), data[j:]
 }

 // removeWhitespace returns a copy of its input with all spaces, tab and
 // newline characters removed.
 func removeWhitespace(data []byte) []byte {
 	result := make([]byte, len(data))
 	n := 0

 	for _, b := range data {
 		if b == ' ' || b == '\t' || b == '\r' || b == '\n' {
 			continue
 		}
 		result[n] = b
 		n++
 	}

 	return result[0:n]
 }

 var pemStart = []byte("\n-----BEGIN ")
 var pemEnd = []byte("\n-----END ")
 var pemEndOfLine = []byte("-----")

 // Decode will find the next PEM formatted block (certificate, private key
 // etc) in the input. It returns that block and the remainder of the input. If
 // no PEM data is found, p is nil and the whole of the input is returned in
 // rest.
 func Decode(data []byte) (p *Block, rest []byte) {
 	// pemStart begins with a newline. However, at the very beginning of
 	// the byte array, we'll accept the start string without it.
 	rest = data
 	if bytes.HasPrefix(data, pemStart[1:]) {
 		rest = rest[len(pemStart)-1 : len(data)]
 	} else if i := bytes.Index(data, pemStart); i >= 0 {
 		rest = rest[i+len(pemStart) : len(data)]
 	} else {
 		return nil, data
 	}

 	typeLine, rest := getLine(rest)
 	if !bytes.HasSuffix(typeLine, pemEndOfLine) {
 		return decodeError(data, rest)
 	}
 	typeLine = typeLine[0 : len(typeLine)-len(pemEndOfLine)]

 	p = &Block{
 		Headers: make(map[string]string),
 		Type:    string(typeLine),
 	}

 	for {
 		// This loop terminates because getLine's second result is
 		// always smaller than its argument.
 		if len(rest) == 0 {
 			return nil, data
 		}
 		line, next := getLine(rest)

 		i := bytes.IndexByte(line, ':')
 		if i == -1 {
 			break
 		}

 		// TODO(agl): need to cope with values that spread across lines.
 		key, val := line[:i], line[i+1:]
 		key = bytes.TrimSpace(key)
 		val = bytes.TrimSpace(val)
 		p.Headers[string(key)] = string(val)
 		rest = next
 	}

 	var endIndex, endTrailerIndex int

 	// If there were no headers, the END line might occur
 	// immediately, without a leading newline.
 	if len(p.Headers) == 0 && bytes.HasPrefix(rest, pemEnd[1:]) {
 		endIndex = 0
 		endTrailerIndex = len(pemEnd) - 1
 	} else {
 		endIndex = bytes.Index(rest, pemEnd)
 		endTrailerIndex = endIndex + len(pemEnd)
 	}

 	if endIndex < 0 {
 		return decodeError(data, rest)
 	}

 	// After the "-----" of the ending line, there should be the same type
 	// and then a final five dashes.
 	endTrailer := rest[endTrailerIndex:]
 	endTrailerLen := len(typeLine) + len(pemEndOfLine)
 	if len(endTrailer) < endTrailerLen {
 		return decodeError(data, rest)
 	}

 	restOfEndLine := endTrailer[endTrailerLen:]
 	endTrailer = endTrailer[:endTrailerLen]
 	if !bytes.HasPrefix(endTrailer, typeLine) ||
 		!bytes.HasSuffix(endTrailer, pemEndOfLine) {
 		return decodeError(data, rest)
 	}

 	// The line must end with only whitespace.
 	if s, _ := getLine(restOfEndLine); len(s) != 0 {
 		return decodeError(data, rest)
 	}

 	base64Data := removeWhitespace(rest[:endIndex])
 	p.Bytes = make([]byte, base64.StdEncoding.DecodedLen(len(base64Data)))
 	n, err := base64.StdEncoding.Decode(p.Bytes, base64Data)
 	if err != nil {
 		return decodeError(data, rest)
 	}
 	p.Bytes = p.Bytes[:n]

 	// the -1 is because we might have only matched pemEnd without the
 	// leading newline if the PEM block was empty.
 	_, rest = getLine(rest[endIndex+len(pemEnd)-1:])

 	return
 }

 func decodeError(data, rest []byte) (*Block, []byte) {
 	// If we get here then we have rejected a likely looking, but
 	// ultimately invalid PEM block. We need to start over from a new
 	// position. We have consumed the preamble line and will have consumed
 	// any lines which could be header lines. However, a valid preamble
 	// line is not a valid header line, therefore we cannot have consumed
 	// the preamble line for the any subsequent block. Thus, we will always
 	// find any valid block, no matter what bytes precede it.
 	//
 	// For example, if the input is
 	//
 	//    -----BEGIN MALFORMED BLOCK-----
 	//    junk that may look like header lines
 	//   or data lines, but no END line
 	//
 	//    -----BEGIN ACTUAL BLOCK-----
 	//    realdata
 	//    -----END ACTUAL BLOCK-----
 	//
 	// we've failed to parse using the first BEGIN line
 	// and now will try again, using the second BEGIN line.
 	p, rest := Decode(rest)
 	if p == nil {
 		rest = data
 	}
 	return p, rest
 }

 const pemLineLength = 64

 type lineBreaker struct {
 	line [pemLineLength]byte
 	used int
 	out  io.Writer
 }

 var nl = []byte{'\n'}

 func (l *lineBreaker) Write(b []byte) (n int, err error) {
 	if l.used+len(b) < pemLineLength {
 		copy(l.line[l.used:], b)
 		l.used += len(b)
 		return len(b), nil
 	}

 	n, err = l.out.Write(l.line[0:l.used])
 	if err != nil {
 		return
 	}
 	excess := pemLineLength - l.used
 	l.used = 0

 	n, err = l.out.Write(b[0:excess])
 	if err != nil {
 		return
 	}

 	n, err = l.out.Write(nl)
 	if err != nil {
 		return
 	}

 	return l.Write(b[excess:])
 }

 func (l *lineBreaker) Close() (err error) {
 	if l.used > 0 {
 		_, err = l.out.Write(l.line[0:l.used])
 		if err != nil {
 			return
 		}
 		_, err = l.out.Write(nl)
 	}

 	return
 }

 func writeHeader(out io.Writer, k, v string) error {
 	_, err := out.Write([]byte(k + ": " + v + "\n"))
 	return err
 }

 // Encode writes the PEM encoding of b to out.
 func Encode(out io.Writer, b *Block) error {
 	// Check for invalid block before writing any output.
 	for k := range b.Headers {
 		if strings.Contains(k, ":") {
 			return errors.New("pem: cannot encode a header key that contains a colon")
 		}
 	}

 	// All errors below are relayed from underlying io.Writer,
 	// so it is now safe to write data.

 	if _, err := out.Write(pemStart[1:]); err != nil {
 		return err
 	}
 	if _, err := out.Write([]byte(b.Type + "-----\n")); err != nil {
 		return err
 	}

 	if len(b.Headers) > 0 {
 		const procType = "Proc-Type"
 		h := make([]string, 0, len(b.Headers))
 		hasProcType := false
 		for k := range b.Headers {
 			if k == procType {
 				hasProcType = true
 				continue
 			}
 			h = append(h, k)
 		}
 		// The Proc-Type header must be written first.
 		// See RFC 1421, section 4.6.1.1
 		if hasProcType {
 			if err := writeHeader(out, procType, b.Headers[procType]); err != nil {
 				return err
 			}
 		}
 		// For consistency of output, write other headers sorted by key.
 		sort.Strings(h)
 		for _, k := range h {
 			if err := writeHeader(out, k, b.Headers[k]); err != nil {
 				return err
 			}
 		}
 		if _, err := out.Write(nl); err != nil {
 			return err
 		}
 	}

 	var breaker lineBreaker
 	breaker.out = out

 	b64 := base64.NewEncoder(base64.StdEncoding, &breaker)
 	if _, err := b64.Write(b.Bytes); err != nil {
 		return err
 	}
 	b64.Close()
 	breaker.Close()

 	if _, err := out.Write(pemEnd[1:]); err != nil {
 		return err
 	}
 	_, err := out.Write([]byte(b.Type + "-----\n"))
 	return err
 }

 // EncodeToMemory returns the PEM encoding of b.
 //
 // If b has invalid headers and cannot be encoded,
 // EncodeToMemory returns nil. If it is important to
 // report details about this error case, use Encode instead.
 func EncodeToMemory(b *Block) []byte {
 	var buf bytes.Buffer
 	if err := Encode(&buf, b); err != nil {
 		return nil
 	}
 	return buf.Bytes()
 }
	// Copyright 2009 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 pem implements the PEM data encoding, which originated in Privacy
	// Enhanced Mail. The most common use of PEM encoding today is in TLS keys and
	// certificates. See RFC 1421.
	package pem

	import (
	"bytes"
	"encoding/base64"
	"errors"
	"io"
	"sort"
	"strings"
	)

	// A Block represents a PEM encoded structure.
	//
	// The encoded form is:
	// -----BEGIN Type-----
	// Headers
	// base64-encoded Bytes
	// -----END Type-----
	// where Headers is a possibly empty sequence of Key: Value lines.
	type Block struct {
	Type string // The type, taken from the preamble (i.e. "RSA PRIVATE KEY").
	Headers map[string]string // Optional headers.
	Bytes []byte // The decoded bytes of the contents. Typically a DER encoded ASN.1 structure.
	}

	// getLine results the first \r\n or \n delineated line from the given byte
	// array. The line does not include trailing whitespace or the trailing new
	// line bytes. The remainder of the byte array (also not including the new line
	// bytes) is also returned and this will always be smaller than the original
	// argument.
	func getLine(data []byte) (line, rest []byte) {
	i := bytes.IndexByte(data, '\n')
	var j int
	if i < 0 {
	i = len(data)
	j = i
	} else {
	j = i + 1
	if i > 0 && data[i-1] == '\r' {
	i--
	}
	}
	return bytes.TrimRight(data[0:i], " \t"), data[j:]
	}

	// removeWhitespace returns a copy of its input with all spaces, tab and
	// newline characters removed.
	func removeWhitespace(data []byte) []byte {
	result := make([]byte, len(data))
	n := 0

	for _, b := range data {
	if b == ' ' \|\| b == '\t' \|\| b == '\r' \|\| b == '\n' {
	continue
	}
	result[n] = b
	n++
	}

	return result[0:n]
	}

	var pemStart = []byte("\n-----BEGIN ")
	var pemEnd = []byte("\n-----END ")
	var pemEndOfLine = []byte("-----")

	// Decode will find the next PEM formatted block (certificate, private key
	// etc) in the input. It returns that block and the remainder of the input. If
	// no PEM data is found, p is nil and the whole of the input is returned in
	// rest.
	func Decode(data []byte) (p *Block, rest []byte) {
	// pemStart begins with a newline. However, at the very beginning of
	// the byte array, we'll accept the start string without it.
	rest = data
	if bytes.HasPrefix(data, pemStart[1:]) {
	rest = rest[len(pemStart)-1 : len(data)]
	} else if i := bytes.Index(data, pemStart); i >= 0 {
	rest = rest[i+len(pemStart) : len(data)]
	} else {
	return nil, data
	}

	typeLine, rest := getLine(rest)
	if !bytes.HasSuffix(typeLine, pemEndOfLine) {
	return decodeError(data, rest)
	}
	typeLine = typeLine[0 : len(typeLine)-len(pemEndOfLine)]

	p = &Block{
	Headers: make(map[string]string),
	Type: string(typeLine),
	}

	for {
	// This loop terminates because getLine's second result is
	// always smaller than its argument.
	if len(rest) == 0 {
	return nil, data
	}
	line, next := getLine(rest)

	i := bytes.IndexByte(line, ':')
	if i == -1 {
	break
	}

	// TODO(agl): need to cope with values that spread across lines.
	key, val := line[:i], line[i+1:]
	key = bytes.TrimSpace(key)
	val = bytes.TrimSpace(val)
	p.Headers[string(key)] = string(val)
	rest = next
	}

	var endIndex, endTrailerIndex int

	// If there were no headers, the END line might occur
	// immediately, without a leading newline.
	if len(p.Headers) == 0 && bytes.HasPrefix(rest, pemEnd[1:]) {
	endIndex = 0
	endTrailerIndex = len(pemEnd) - 1
	} else {
	endIndex = bytes.Index(rest, pemEnd)
	endTrailerIndex = endIndex + len(pemEnd)
	}

	if endIndex < 0 {
	return decodeError(data, rest)
	}

	// After the "-----" of the ending line, there should be the same type
	// and then a final five dashes.
	endTrailer := rest[endTrailerIndex:]
	endTrailerLen := len(typeLine) + len(pemEndOfLine)
	if len(endTrailer) < endTrailerLen {
	return decodeError(data, rest)
	}

	restOfEndLine := endTrailer[endTrailerLen:]
	endTrailer = endTrailer[:endTrailerLen]
	if !bytes.HasPrefix(endTrailer, typeLine) \|\|
	!bytes.HasSuffix(endTrailer, pemEndOfLine) {
	return decodeError(data, rest)
	}

	// The line must end with only whitespace.
	if s, _ := getLine(restOfEndLine); len(s) != 0 {
	return decodeError(data, rest)
	}

	base64Data := removeWhitespace(rest[:endIndex])
	p.Bytes = make([]byte, base64.StdEncoding.DecodedLen(len(base64Data)))
	n, err := base64.StdEncoding.Decode(p.Bytes, base64Data)
	if err != nil {
	return decodeError(data, rest)
	}
	p.Bytes = p.Bytes[:n]

	// the -1 is because we might have only matched pemEnd without the
	// leading newline if the PEM block was empty.
	_, rest = getLine(rest[endIndex+len(pemEnd)-1:])

	return
	}

	func decodeError(data, rest []byte) (*Block, []byte) {
	// If we get here then we have rejected a likely looking, but
	// ultimately invalid PEM block. We need to start over from a new
	// position. We have consumed the preamble line and will have consumed
	// any lines which could be header lines. However, a valid preamble
	// line is not a valid header line, therefore we cannot have consumed
	// the preamble line for the any subsequent block. Thus, we will always
	// find any valid block, no matter what bytes precede it.
	//
	// For example, if the input is
	//
	// -----BEGIN MALFORMED BLOCK-----
	// junk that may look like header lines
	// or data lines, but no END line
	//
	// -----BEGIN ACTUAL BLOCK-----
	// realdata
	// -----END ACTUAL BLOCK-----
	//
	// we've failed to parse using the first BEGIN line
	// and now will try again, using the second BEGIN line.
	p, rest := Decode(rest)
	if p == nil {
	rest = data
	}
	return p, rest
	}

	const pemLineLength = 64

	type lineBreaker struct {
	line [pemLineLength]byte
	used int
	out io.Writer
	}

	var nl = []byte{'\n'}

	func (l *lineBreaker) Write(b []byte) (n int, err error) {
	if l.used+len(b) < pemLineLength {
	copy(l.line[l.used:], b)
	l.used += len(b)
	return len(b), nil
	}

	n, err = l.out.Write(l.line[0:l.used])
	if err != nil {
	return
	}
	excess := pemLineLength - l.used
	l.used = 0

	n, err = l.out.Write(b[0:excess])
	if err != nil {
	return
	}

	n, err = l.out.Write(nl)
	if err != nil {
	return
	}

	return l.Write(b[excess:])
	}

	func (l *lineBreaker) Close() (err error) {
	if l.used > 0 {
	_, err = l.out.Write(l.line[0:l.used])
	if err != nil {
	return
	}
	_, err = l.out.Write(nl)
	}

	return
	}

	func writeHeader(out io.Writer, k, v string) error {
	_, err := out.Write([]byte(k + ": " + v + "\n"))
	return err
	}

	// Encode writes the PEM encoding of b to out.
	func Encode(out io.Writer, b *Block) error {
	// Check for invalid block before writing any output.
	for k := range b.Headers {
	if strings.Contains(k, ":") {
	return errors.New("pem: cannot encode a header key that contains a colon")
	}
	}

	// All errors below are relayed from underlying io.Writer,
	// so it is now safe to write data.

	if _, err := out.Write(pemStart[1:]); err != nil {
	return err
	}
	if _, err := out.Write([]byte(b.Type + "-----\n")); err != nil {
	return err
	}

	if len(b.Headers) > 0 {
	const procType = "Proc-Type"
	h := make([]string, 0, len(b.Headers))
	hasProcType := false
	for k := range b.Headers {
	if k == procType {
	hasProcType = true
	continue
	}
	h = append(h, k)
	}
	// The Proc-Type header must be written first.
	// See RFC 1421, section 4.6.1.1
	if hasProcType {
	if err := writeHeader(out, procType, b.Headers[procType]); err != nil {
	return err
	}
	}
	// For consistency of output, write other headers sorted by key.
	sort.Strings(h)
	for _, k := range h {
	if err := writeHeader(out, k, b.Headers[k]); err != nil {
	return err
	}
	}
	if _, err := out.Write(nl); err != nil {
	return err
	}
	}

	var breaker lineBreaker
	breaker.out = out

	b64 := base64.NewEncoder(base64.StdEncoding, &breaker)
	if _, err := b64.Write(b.Bytes); err != nil {
	return err
	}
	b64.Close()
	breaker.Close()

	if _, err := out.Write(pemEnd[1:]); err != nil {
	return err
	}
	_, err := out.Write([]byte(b.Type + "-----\n"))
	return err
	}

	// EncodeToMemory returns the PEM encoding of b.
	//
	// If b has invalid headers and cannot be encoded,
	// EncodeToMemory returns nil. If it is important to
	// report details about this error case, use Encode instead.
	func EncodeToMemory(b *Block) []byte {
	var buf bytes.Buffer
	if err := Encode(&buf, b); err != nil {
	return nil
	}
	return buf.Bytes()
	}