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Fix dohpath parsing/stringify #1366

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merged 3 commits into from May 10, 2022
Merged

Fix dohpath parsing/stringify #1366

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01e03fa
dohpath escaped in String(), and parsed such values
shane-ns1 Apr 14, 2022
f0ed4db
Update the test for dohpath with escaping
shane-ns1 Apr 14, 2022
0b5d485
Fix cut & paste error with svcdohpath error
shane-ns1 Apr 14, 2022
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1 change: 1 addition & 0 deletions parse_test.go
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Expand Up @@ -1654,6 +1654,7 @@ func TestParseSVCB(t *testing.T) {
`example.com. SVCB 16 foo.example.org. alpn=f\\\092oo\092,bar,h2`: `example.com. 3600 IN SVCB 16 foo.example.org. alpn="f\\\092oo\092,bar,h2"`,
// From draft-ietf-add-ddr-06
`_dns.example.net. SVCB 1 example.net. alpn=h2 dohpath=/dns-query{?dns}`: `_dns.example.net. 3600 IN SVCB 1 example.net. alpn="h2" dohpath="/dns-query{?dns}"`,
`_dns.example.net. SVCB 1 example.net. alpn=h2 dohpath=/dns\045query{\?dns}`: `_dns.example.net. 3600 IN SVCB 1 example.net. alpn="h2" dohpath="/dns-query{?dns}"`,
}
for s, o := range svcbs {
rr, err := NewRR(s)
Expand Down
106 changes: 61 additions & 45 deletions svcb.go
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Expand Up @@ -4,6 +4,7 @@ import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"net"
"sort"
"strconv"
Expand Down Expand Up @@ -697,7 +698,7 @@ type SVCBDoHPath struct {
}

func (*SVCBDoHPath) Key() SVCBKey { return SVCB_DOHPATH }
func (s *SVCBDoHPath) String() string { return s.Template }
func (s *SVCBDoHPath) String() string { return svcbParamToStr([]byte(s.Template)) }
func (s *SVCBDoHPath) len() int { return len(s.Template) }
func (s *SVCBDoHPath) pack() ([]byte, error) { return []byte(s.Template), nil }

Expand All @@ -707,7 +708,11 @@ func (s *SVCBDoHPath) unpack(b []byte) error {
}

func (s *SVCBDoHPath) parse(b string) error {
s.Template = b
template, err := svcbParseParam(b)
if err != nil {
return fmt.Errorf("dns: svcblocal: svcb private/experimental key %w", err)
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This message should probably be about svcbdohpath?

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Whoops! Cut & paste error. I've fix this, thanks for spotting!

}
s.Template = string(template)
return nil
}

Expand All @@ -733,6 +738,7 @@ type SVCBLocal struct {
}

func (s *SVCBLocal) Key() SVCBKey { return s.KeyCode }
func (s *SVCBLocal) String() string { return svcbParamToStr(s.Data) }
func (s *SVCBLocal) pack() ([]byte, error) { return append([]byte(nil), s.Data...), nil }
func (s *SVCBLocal) len() int { return len(s.Data) }

Expand All @@ -741,50 +747,10 @@ func (s *SVCBLocal) unpack(b []byte) error {
return nil
}

func (s *SVCBLocal) String() string {
var str strings.Builder
str.Grow(4 * len(s.Data))
for _, e := range s.Data {
if ' ' <= e && e <= '~' {
switch e {
case '"', ';', ' ', '\\':
str.WriteByte('\\')
str.WriteByte(e)
default:
str.WriteByte(e)
}
} else {
str.WriteString(escapeByte(e))
}
}
return str.String()
}

func (s *SVCBLocal) parse(b string) error {
data := make([]byte, 0, len(b))
for i := 0; i < len(b); {
if b[i] != '\\' {
data = append(data, b[i])
i++
continue
}
if i+1 == len(b) {
return errors.New("dns: svcblocal: svcb private/experimental key escape unterminated")
}
if isDigit(b[i+1]) {
if i+3 < len(b) && isDigit(b[i+2]) && isDigit(b[i+3]) {
a, err := strconv.ParseUint(b[i+1:i+4], 10, 8)
if err == nil {
i += 4
data = append(data, byte(a))
continue
}
}
return errors.New("dns: svcblocal: svcb private/experimental key bad escaped octet")
} else {
data = append(data, b[i+1])
i += 2
}
data, err := svcbParseParam(b)
if err != nil {
return fmt.Errorf("dns: svcblocal: svcb private/experimental key %w", err)
}
s.Data = data
return nil
Expand Down Expand Up @@ -825,3 +791,53 @@ func areSVCBPairArraysEqual(a []SVCBKeyValue, b []SVCBKeyValue) bool {
}
return true
}

// svcbParamStr converts the value of an SVCB parameter into a DNS presentation-format string.
func svcbParamToStr(s []byte) string {
var str strings.Builder
str.Grow(4 * len(s))
for _, e := range s {
if ' ' <= e && e <= '~' {
switch e {
case '"', ';', ' ', '\\':
str.WriteByte('\\')
str.WriteByte(e)
default:
str.WriteByte(e)
}
} else {
str.WriteString(escapeByte(e))
}
}
return str.String()
}

// svcbParseParam parses a DNS presentation-format string into an SVCB parameter value.
func svcbParseParam(b string) ([]byte, error) {
data := make([]byte, 0, len(b))
for i := 0; i < len(b); {
if b[i] != '\\' {
data = append(data, b[i])
i++
continue
}
if i+1 == len(b) {
return nil, errors.New("escape unterminated")
}
if isDigit(b[i+1]) {
if i+3 < len(b) && isDigit(b[i+2]) && isDigit(b[i+3]) {
a, err := strconv.ParseUint(b[i+1:i+4], 10, 8)
if err == nil {
i += 4
data = append(data, byte(a))
continue
}
}
return nil, errors.New("bad escaped octet")
} else {
data = append(data, b[i+1])
i += 2
}
}
return data, nil
}