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DNS SVCB and HTTPS resource records (RFC 9460). #1159

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DNS SVCB and HTTPS resource records (RFC 9460). #1159

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d5b8702
DNS SVCB and HTTPS resource records (RFC 9460).
markkurossi Mar 24, 2024
2f7dff3
Govet fixes.
markkurossi Mar 24, 2024
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171 changes: 171 additions & 0 deletions layers/dns.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,8 @@ const (
DNSTypeAAAA DNSType = 28 // a IPv6 host address [RFC3596]
DNSTypeSRV DNSType = 33 // server discovery [RFC2782] [RFC6195]
DNSTypeOPT DNSType = 41 // OPT Pseudo-RR [RFC6891]
DNSTypeSVCB DNSType = 64 // SVCB DNS RR [RFC9460]
DNSTypeHTTPS DNSType = 65 // HTTPS RR [RFC9460]
DNSTypeURI DNSType = 256 // URI RR [RFC7553]
)

Expand Down Expand Up @@ -116,6 +118,10 @@ func (dt DNSType) String() string {
return "SRV"
case DNSTypeOPT:
return "OPT"
case DNSTypeSVCB:
return "SVCB"
case DNSTypeHTTPS:
return "HTTPS"
case DNSTypeURI:
return "URI"
}
Expand Down Expand Up @@ -445,6 +451,8 @@ func recSize(rr *DNSResourceRecord) int {
l += len(opt.Data)
}
return l
case DNSTypeSVCB, DNSTypeHTTPS:
return rr.SVCB.size()
}

return 0
Expand Down Expand Up @@ -700,6 +708,7 @@ type DNSResourceRecord struct {
SRV DNSSRV
MX DNSMX
OPT []DNSOPT // See RFC 6891, section 6.1.2
SVCB DNSSVCB // See RFC 9460, this contains both SVCB and HTTPS
URI DNSURI

// Undecoded TXT for backward compatibility
Expand Down Expand Up @@ -816,6 +825,8 @@ func (rr *DNSResourceRecord) encode(data []byte, offset int, opts gopacket.Seria
copy(data[noff2+4:], opt.Data)
noff2 += 4 + len(opt.Data)
}
case DNSTypeSVCB, DNSTypeHTTPS:
rr.SVCB.encode(data, noff+10)
default:
return 0, fmt.Errorf("serializing resource record of type %v not supported", rr.Type)
}
Expand Down Expand Up @@ -903,6 +914,47 @@ func decodeOPTs(data []byte, offset int) ([]DNSOPT, error) {
return allOPT, nil
}

func decodeSVCB(data []byte, offset int, buffer *[]byte) (DNSSVCB, error) {
var svcb DNSSVCB
end := len(data)

if offset == end {
return svcb, fmt.Errorf("DNSSVCB record is empty")
}

if offset+3 > end {
return svcb, fmt.Errorf("DNSSVCB record is of length %d, it should be at least length 3", end-offset)
}
priority := binary.BigEndian.Uint16(data[offset:])
target, ofs, err := decodeName(data, offset+2, buffer, 1)
if err != nil {
return svcb, err
}

var params []DNSSvcParam
for ofs < end {
if offset+4 > end {
return svcb, fmt.Errorf("DNSSVCB record truncated in SvcParams")
}
key := DNSSvcParamKey(binary.BigEndian.Uint16(data[ofs:]))
l := int(binary.BigEndian.Uint16(data[ofs+2:]))
if ofs+4+l > end {
return svcb, fmt.Errorf("DNSSVCB record truncated in SvcParams")
}
params = append(params, DNSSvcParam{
Key: key,
Value: data[ofs+4 : ofs+4+l],
})
ofs += 4 + l
}

return DNSSVCB{
Priority: priority,
Target: target,
Params: params,
}, nil
}

func (rr *DNSResourceRecord) decodeRData(data []byte, offset int, buffer *[]byte) error {
switch rr.Type {
case DNSTypeA:
Expand Down Expand Up @@ -988,6 +1040,12 @@ func (rr *DNSResourceRecord) decodeRData(data []byte, offset int, buffer *[]byte
return err
}
rr.OPT = allOPT
case DNSTypeSVCB, DNSTypeHTTPS:
svcb, err := decodeSVCB(data, offset, buffer)
if err != nil {
return err
}
rr.SVCB = svcb
}
return nil
}
Expand All @@ -1013,6 +1071,119 @@ type DNSMX struct {
Name []byte
}

// DNSSVCB resource record is used to facilitate the lookup of
// information needed to make connections to network services, such as
// for HTTP origins.
type DNSSVCB struct {
Priority uint16
Target []byte
Params []DNSSvcParam
}

func (svcb DNSSVCB) size() int {
// Target.
sz := len(svcb.Target)
if sz == 0 {
sz++
} else {
sz += 2
}
// Priority.
sz += 2

// Params.
for _, param := range svcb.Params {
sz += param.size()
}
return sz
}

func (svcb DNSSVCB) String() string {
return fmt.Sprintf("%v [%s] %v",
svcb.Priority, string(svcb.Target), svcb.Params)
}

func (svcb DNSSVCB) encode(data []byte, offset int) {
binary.BigEndian.PutUint16(data[offset:], svcb.Priority)
offset = encodeName(svcb.Target, data, offset+2)

for _, param := range svcb.Params {
offset = param.encode(data, offset)
}
}

// DNSSvcParamKey defines SVCB service parameter keys.
type DNSSvcParamKey uint16

func (key DNSSvcParamKey) String() string {
switch key {
default:
return "Unknown"
case DNSSvcParamKeyMandatory:
return "mandatory"
case DNSSvcParamKeyAlpn:
return "alpn"
case DNSSvcParamKeyNoDefaultAlpn:
return "no-default-alpn"
case DNSSvcParamKeyPort:
return "port"
case DNSSvcParamKeyIPv4Hint:
return "ipv4hint"
case DNSSvcParamKeyECH:
return "ech"
case DNSSvcParamKeyIPv6Hint:
return "ipv6hint"
case DNSSvcParamKeyDoHPath:
return "dohpath"
case DNSSvcParamKeyOHTTP:
return "ohttp"
case DNSSvcParamKeyDoHURI:
return "dohuri"
case DNSSvcParamKeyInvalidKey:
return "Invalid key"
}
}

// DNSSvcParamKey known values.
const (
DNSSvcParamKeyMandatory DNSSvcParamKey = 0 // RFC9460, Section 8
DNSSvcParamKeyAlpn DNSSvcParamKey = 1 // RFC9460, Section 7.1
DNSSvcParamKeyNoDefaultAlpn DNSSvcParamKey = 2 // RFC9460, Section 7.1
DNSSvcParamKeyPort DNSSvcParamKey = 3 // RFC9460, Section 7.2
DNSSvcParamKeyIPv4Hint DNSSvcParamKey = 4 // RFC9460, Section 7.3
DNSSvcParamKeyECH DNSSvcParamKey = 5 // RFC9460
DNSSvcParamKeyIPv6Hint DNSSvcParamKey = 6 // RFC9460, Section 7.3
DNSSvcParamKeyDoHPath DNSSvcParamKey = 7 // RFC9461
DNSSvcParamKeyOHTTP DNSSvcParamKey = 8 // RFC9540, Section 4
DNSSvcParamKeyDoHURI DNSSvcParamKey = 32768 // draft-pauly-add-resolver-discovery-00.html
DNSSvcParamKeyInvalidKey DNSSvcParamKey = 65535 // RFC9460
)

// DNSSvcParam is a service param, see RFC9460, section 2.2.
type DNSSvcParam struct {
Key DNSSvcParamKey
Value []byte
}

func (param DNSSvcParam) size() int {
return 2 + 2 + len(param.Value)
}

func (param DNSSvcParam) encode(data []byte, offset int) int {
binary.BigEndian.PutUint16(data[offset:], uint16(param.Key))
offset += 2
binary.BigEndian.PutUint16(data[offset:], uint16(len(param.Value)))
offset += 2
copy(data[offset:], param.Value)
offset += len(param.Value)

return offset
}

func (param DNSSvcParam) String() string {
return fmt.Sprintf("%s=%x", param.Key, param.Value)
}

// DNSURI is a URI record, defining a target (URI) of a server/service
type DNSURI struct {
Priority, Weight uint16
Expand Down
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