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// Copyright (c) 2021 Tulir Asokan
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package id
import (
"bytes"
"encoding/hex"
"errors"
"fmt"
"regexp"
"strings"
)
// UserID represents a Matrix user ID.
// https://matrix.org/docs/spec/appendices#user-identifiers
type UserID string
const UserIDMaxLength = 255
func NewUserID(localpart, homeserver string) UserID {
return UserID(fmt.Sprintf("@%s:%s", localpart, homeserver))
}
func NewEncodedUserID(localpart, homeserver string) UserID {
return NewUserID(EncodeUserLocalpart(localpart), homeserver)
}
var (
ErrInvalidUserID = errors.New("is not a valid user ID")
ErrNoncompliantLocalpart = errors.New("contains characters that are not allowed")
ErrUserIDTooLong = errors.New("the given user ID is longer than 255 characters")
ErrEmptyLocalpart = errors.New("empty localparts are not allowed")
)
// Parse parses the user ID into the localpart and server name.
//
// Note that this only enforces very basic user ID formatting requirements: user IDs start with
// a @, and contain a : after the @. If you want to enforce localpart validity, see the
// ParseAndValidate and ValidateUserLocalpart functions.
func (userID UserID) Parse() (localpart, homeserver string, err error) {
if len(userID) == 0 || userID[0] != '@' || !strings.ContainsRune(string(userID), ':') {
// This error wrapping lets you use errors.Is() nicely even though the message contains the user ID
err = fmt.Errorf("'%s' %w", userID, ErrInvalidUserID)
return
}
parts := strings.SplitN(string(userID), ":", 2)
localpart, homeserver = strings.TrimPrefix(parts[0], "@"), parts[1]
return
}
func (userID UserID) Localpart() string {
localpart, _, _ := userID.Parse()
return localpart
}
func (userID UserID) Homeserver() string {
_, homeserver, _ := userID.Parse()
return homeserver
}
// URI returns the user ID as a MatrixURI struct, which can then be stringified into a matrix: URI or a matrix.to URL.
//
// This does not parse or validate the user ID. Use the ParseAndValidate method if you want to ensure the user ID is valid first.
func (userID UserID) URI() *MatrixURI {
return &MatrixURI{
Sigil1: '@',
MXID1: string(userID)[1:],
}
}
var ValidLocalpartRegex = regexp.MustCompile("^[0-9a-z-.=_/]+$")
// ValidateUserLocalpart validates a Matrix user ID localpart using the grammar
// in https://matrix.org/docs/spec/appendices#user-identifier
func ValidateUserLocalpart(localpart string) error {
if len(localpart) == 0 {
return ErrEmptyLocalpart
} else if !ValidLocalpartRegex.MatchString(localpart) {
return fmt.Errorf("'%s' %w", localpart, ErrNoncompliantLocalpart)
}
return nil
}
// ParseAndValidate parses the user ID into the localpart and server name like Parse,
// and also validates that the localpart is allowed according to the user identifiers spec.
func (userID UserID) ParseAndValidate() (localpart, homeserver string, err error) {
localpart, homeserver, err = userID.Parse()
if err == nil {
err = ValidateUserLocalpart(localpart)
}
if err == nil && len(userID) > UserIDMaxLength {
err = ErrUserIDTooLong
}
return
}
func (userID UserID) ParseAndDecode() (localpart, homeserver string, err error) {
localpart, homeserver, err = userID.ParseAndValidate()
if err == nil {
localpart, err = DecodeUserLocalpart(localpart)
}
return
}
func (userID UserID) String() string {
return string(userID)
}
const lowerhex = "0123456789abcdef"
// encode the given byte using quoted-printable encoding (e.g "=2f")
// and writes it to the buffer
// See https://golang.org/src/mime/quotedprintable/writer.go
func encode(buf *bytes.Buffer, b byte) {
buf.WriteByte('=')
buf.WriteByte(lowerhex[b>>4])
buf.WriteByte(lowerhex[b&0x0f])
}
// escape the given alpha character and writes it to the buffer
func escape(buf *bytes.Buffer, b byte) {
buf.WriteByte('_')
if b == '_' {
buf.WriteByte('_') // another _
} else {
buf.WriteByte(b + 0x20) // ASCII shift A-Z to a-z
}
}
func shouldEncode(b byte) bool {
return b != '-' && b != '.' && b != '_' && !(b >= '0' && b <= '9') && !(b >= 'a' && b <= 'z') && !(b >= 'A' && b <= 'Z')
}
func shouldEscape(b byte) bool {
return (b >= 'A' && b <= 'Z') || b == '_'
}
func isValidByte(b byte) bool {
return isValidEscapedChar(b) || (b >= '0' && b <= '9') || b == '.' || b == '=' || b == '-'
}
func isValidEscapedChar(b byte) bool {
return b == '_' || (b >= 'a' && b <= 'z')
}
// EncodeUserLocalpart encodes the given string into Matrix-compliant user ID localpart form.
// See https://spec.matrix.org/v1.2/appendices/#mapping-from-other-character-sets
//
// This returns a string with only the characters "a-z0-9._=-". The uppercase range A-Z
// are encoded using leading underscores ("_"). Characters outside the aforementioned ranges
// (including literal underscores ("_") and equals ("=")) are encoded as UTF8 code points (NOT NCRs)
// and converted to lower-case hex with a leading "=". For example:
//
// Alph@Bet_50up => _alph=40_bet=5f50up
func EncodeUserLocalpart(str string) string {
strBytes := []byte(str)
var outputBuffer bytes.Buffer
for _, b := range strBytes {
if shouldEncode(b) {
encode(&outputBuffer, b)
} else if shouldEscape(b) {
escape(&outputBuffer, b)
} else {
outputBuffer.WriteByte(b)
}
}
return outputBuffer.String()
}
// DecodeUserLocalpart decodes the given string back into the original input string.
// Returns an error if the given string is not a valid user ID localpart encoding.
// See https://spec.matrix.org/v1.2/appendices/#mapping-from-other-character-sets
//
// This decodes quoted-printable bytes back into UTF8, and unescapes casing. For
// example:
//
// _alph=40_bet=5f50up => Alph@Bet_50up
//
// Returns an error if the input string contains characters outside the
// range "a-z0-9._=-", has an invalid quote-printable byte (e.g. not hex), or has
// an invalid _ escaped byte (e.g. "_5").
func DecodeUserLocalpart(str string) (string, error) {
strBytes := []byte(str)
var outputBuffer bytes.Buffer
for i := 0; i < len(strBytes); i++ {
b := strBytes[i]
if !isValidByte(b) {
return "", fmt.Errorf("Byte pos %d: Invalid byte", i)
}
if b == '_' { // next byte is a-z and should be upper-case or is another _ and should be a literal _
if i+1 >= len(strBytes) {
return "", fmt.Errorf("Byte pos %d: expected _[a-z_] encoding but ran out of string", i)
}
if !isValidEscapedChar(strBytes[i+1]) { // invalid escaping
return "", fmt.Errorf("Byte pos %d: expected _[a-z_] encoding", i)
}
if strBytes[i+1] == '_' {
outputBuffer.WriteByte('_')
} else {
outputBuffer.WriteByte(strBytes[i+1] - 0x20) // ASCII shift a-z to A-Z
}
i++ // skip next byte since we just handled it
} else if b == '=' { // next 2 bytes are hex and should be buffered ready to be read as utf8
if i+2 >= len(strBytes) {
return "", fmt.Errorf("Byte pos: %d: expected quote-printable encoding but ran out of string", i)
}
dst := make([]byte, 1)
_, err := hex.Decode(dst, strBytes[i+1:i+3])
if err != nil {
return "", err
}
outputBuffer.WriteByte(dst[0])
i += 2 // skip next 2 bytes since we just handled it
} else { // pass through
outputBuffer.WriteByte(b)
}
}
return outputBuffer.String(), nil
}
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