/
parse.go
284 lines (255 loc) · 4.99 KB
/
parse.go
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package scram
import (
"encoding/base64"
"errors"
"fmt"
"strconv"
"strings"
)
type parser struct {
s string // Original casing.
lower string // Lower casing, for case-insensitive token consumption.
o int // Offset in s/lower.
}
type parseError struct{ err error }
func (e parseError) Error() string {
return e.err.Error()
}
func (e parseError) Unwrap() error {
return e.err
}
// toLower lower cases bytes that are A-Z. strings.ToLower does too much. and
// would replace invalid bytes with unicode replacement characters, which would
// break our requirement that offsets into the original and upper case strings
// point to the same character.
func toLower(s string) string {
r := []byte(s)
for i, c := range r {
if c >= 'A' && c <= 'Z' {
r[i] = c + 0x20
}
}
return string(r)
}
func newParser(buf []byte) *parser {
s := string(buf)
return &parser{s, toLower(s), 0}
}
// Turn panics of parseError into a descriptive ErrInvalidEncoding. Called with
// defer by functions that parse.
func (p *parser) recover(rerr *error) {
x := recover()
if x == nil {
return
}
err, ok := x.(error)
if !ok {
panic(x)
}
var xerr Error
if errors.As(err, &xerr) {
*rerr = err
return
}
*rerr = fmt.Errorf("%w: %s", ErrInvalidEncoding, err)
}
func (p *parser) xerrorf(format string, args ...any) {
panic(parseError{fmt.Errorf(format, args...)})
}
func (p *parser) xcheckf(err error, format string, args ...any) {
if err != nil {
panic(parseError{fmt.Errorf("%s: %w", fmt.Sprintf(format, args...), err)})
}
}
func (p *parser) xempty() {
if p.o != len(p.s) {
p.xerrorf("leftover data")
}
}
func (p *parser) xnonempty() {
if p.o >= len(p.s) {
p.xerrorf("unexpected end")
}
}
func (p *parser) xbyte() byte {
p.xnonempty()
c := p.lower[p.o]
p.o++
return c
}
func (p *parser) peek(s string) bool {
return strings.HasPrefix(p.lower[p.o:], s)
}
func (p *parser) take(s string) bool {
if p.peek(s) {
p.o += len(s)
return true
}
return false
}
func (p *parser) xtake(s string) {
if !p.take(s) {
p.xerrorf("expected %q", s)
}
}
func (p *parser) xauthzid() string {
p.xtake("a=")
return p.xsaslname()
}
func (p *parser) xusername() string {
p.xtake("n=")
return p.xsaslname()
}
func (p *parser) xnonce() string {
p.xtake("r=")
o := p.o
for ; o < len(p.s); o++ {
c := p.s[o]
if c <= ' ' || c >= 0x7f || c == ',' {
break
}
}
if o == p.o {
p.xerrorf("empty nonce")
}
r := p.s[p.o:o]
p.o = o
return r
}
func (p *parser) xattrval() {
c := p.xbyte()
if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') {
p.xerrorf("expected alpha for attr-val")
}
p.xtake("=")
p.xvalue()
}
func (p *parser) xvalue() string {
for o, c := range p.s[p.o:] {
if c == 0 || c == ',' {
if o == 0 {
p.xerrorf("invalid empty value")
}
r := p.s[p.o : p.o+o]
p.o = o
return r
}
}
p.xnonempty()
r := p.s[p.o:]
p.o = len(p.s)
return r
}
func (p *parser) xbase64() []byte {
o := p.o
for ; o < len(p.s); o++ {
c := p.s[o]
if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c == '/' || c == '+' || c == '=') {
break
}
}
buf, err := base64.StdEncoding.DecodeString(p.s[p.o:o])
p.xcheckf(err, "decoding base64")
p.o = o
return buf
}
func (p *parser) xsaslname() string {
var esc string
var is bool
var r string
for o, c := range p.s[p.o:] {
if c == 0 || c == ',' {
if is {
p.xerrorf("saslname unexpected end")
}
if o == 0 {
p.xerrorf("saslname cannot be empty")
}
p.o += o
return r
}
if is {
esc += string(c)
if len(esc) < 2 {
continue
}
switch esc {
case "2c", "2C":
r += ","
case "3d", "3D":
r += "="
default:
p.xerrorf("bad escape %q in saslanem", esc)
}
is = false
esc = ""
continue
} else if c == '=' {
is = true
continue
}
r += string(c)
}
if is {
p.xerrorf("saslname unexpected end")
}
if r == "" {
p.xerrorf("saslname cannot be empty")
}
p.o = len(p.s)
return r
}
// ../rfc/5802:889
func (p *parser) xcbname() string {
o := p.o
for ; o < len(p.s); o++ {
c := p.s[o]
if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c == '.' || c == '-' {
continue
}
break
}
if o == p.o {
p.xerrorf("empty channel binding name")
}
r := p.s[p.o:o]
p.o = o
return string(r)
}
func (p *parser) xchannelBinding() []byte {
p.xtake("c=")
return p.xbase64()
}
func (p *parser) xproof() []byte {
p.xtake("p=")
return p.xbase64()
}
func (p *parser) xsalt() []byte {
p.xtake("s=")
return p.xbase64()
}
func (p *parser) xtakefn1(fn func(rune, int) bool) string {
for o, c := range p.s[p.o:] {
if !fn(c, o) {
if o == 0 {
p.xerrorf("non-empty match required")
}
r := p.s[p.o : p.o+o]
p.o += o
return r
}
}
p.xnonempty()
r := p.s[p.o:]
p.o = len(p.s)
return r
}
func (p *parser) xiterations() int {
p.xtake("i=")
digits := p.xtakefn1(func(c rune, i int) bool {
return c >= '1' && c <= '9' || i > 0 && c == '0'
})
v, err := strconv.ParseInt(digits, 10, 32)
p.xcheckf(err, "parsing int")
return int(v)
}