mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-05 08:51:48 +00:00
333 lines
8.3 KiB
Go
333 lines
8.3 KiB
Go
// 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()
|
|
}
|