@ -342,13 +342,57 @@ func (s *SVCBMandatory) copy() SVCBKeyValue {
// h.Hdr = dns.RR_Header{Name: ".", Rrtype: dns.TypeHTTPS, Class: dns.ClassINET}
// e := new(dns.SVCBAlpn)
// e.Alpn = []string{"h2", "http/1.1"}
// h.Value = append( o .Value, e)
// h.Value = append( h .Value, e)
type SVCBAlpn struct {
Alpn [ ] string
}
func ( * SVCBAlpn ) Key ( ) SVCBKey { return SVCB_ALPN }
func ( s * SVCBAlpn ) String ( ) string { return strings . Join ( s . Alpn , "," ) }
func ( * SVCBAlpn ) Key ( ) SVCBKey { return SVCB_ALPN }
func ( s * SVCBAlpn ) String ( ) string {
// An ALPN value is a comma-separated list of values, each of which can be
// an arbitrary binary value. In order to allow parsing, the comma and
// backslash characters are themselves excaped.
//
// However, this escaping is done in addition to the normal escaping which
// happens in zone files, meaning that these values must be
// double-escaped. This looks terrible, so if you see a never-ending
// sequence of backslash in a zone file this may be why.
//
// https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-svcb-https-08#appendix-A.1
var str strings . Builder
for i , alpn := range s . Alpn {
// 4*len(alpn) is the worst case where we escape every character in the alpn as \123, plus 1 byte for the ',' separating the alpn from others
str . Grow ( 4 * len ( alpn ) + 1 )
if i > 0 {
str . WriteByte ( ',' )
}
for j := 0 ; j < len ( alpn ) ; j ++ {
e := alpn [ j ]
if ' ' > e || e > '~' {
str . WriteString ( escapeByte ( e ) )
continue
}
switch e {
// We escape a few characters which may confuse humans or parsers.
case '"' , ';' , ' ' :
str . WriteByte ( '\\' )
str . WriteByte ( e )
// The comma and backslash characters themselves must be
// doubly-escaped. We use `\\` for the first backslash and
// the escaped numeric value for the other value. We especially
// don't want a comma in the output.
case ',' :
str . WriteString ( ` \\\044 ` )
case '\\' :
str . WriteString ( ` \\\092 ` )
default :
str . WriteByte ( e )
}
}
}
return str . String ( )
}
func ( s * SVCBAlpn ) pack ( ) ( [ ] byte , error ) {
// Liberally estimate the size of an alpn as 10 octets
@ -383,7 +427,47 @@ func (s *SVCBAlpn) unpack(b []byte) error {
}
func ( s * SVCBAlpn ) parse ( b string ) error {
s . Alpn = strings . Split ( b , "," )
if len ( b ) == 0 {
s . Alpn = [ ] string { }
return nil
}
alpn := [ ] string { }
a := [ ] byte { }
for p := 0 ; p < len ( b ) ; {
c , q := nextByte ( b , p )
if q == 0 {
return errors . New ( "dns: svcbalpn: unterminated escape" )
}
p += q
// If we find a comma, we have finished reading an alpn.
if c == ',' {
if len ( a ) == 0 {
return errors . New ( "dns: svcbalpn: empty protocol identifier" )
}
alpn = append ( alpn , string ( a ) )
a = [ ] byte { }
continue
}
// If it's a backslash, we need to handle a comma-separated list.
if c == '\\' {
dc , dq := nextByte ( b , p )
if dq == 0 {
return errors . New ( "dns: svcbalpn: unterminated escape decoding comma-separated list" )
}
if dc != '\\' && dc != ',' {
return errors . New ( "dns: svcbalpn: bad escaped character decoding comma-separated list" )
}
p += dq
c = dc
}
a = append ( a , c )
}
// Add the final alpn.
if len ( a ) == 0 {
return errors . New ( "dns: svcbalpn: last protocol identifier empty" )
}
s . Alpn = append ( alpn , string ( a ) )
return nil
}
Shane Kerr
1 year ago
committed by
GitHub