forked from coredns/coredns
/
edns0.go
384 lines (323 loc) · 9.99 KB
/
edns0.go
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// Package rewrite is plugin for rewriting requests internally to something different.
package rewrite
import (
"context"
"encoding/hex"
"fmt"
"net"
"strconv"
"strings"
"github.com/coredns/coredns/plugin/metadata"
"github.com/coredns/coredns/plugin/pkg/edns"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
// edns0LocalRule is a rewrite rule for EDNS0_LOCAL options.
type edns0LocalRule struct {
mode string
action string
code uint16
data []byte
}
// edns0VariableRule is a rewrite rule for EDNS0_LOCAL options with variable.
type edns0VariableRule struct {
mode string
action string
code uint16
variable string
}
// ends0NsidRule is a rewrite rule for EDNS0_NSID options.
type edns0NsidRule struct {
mode string
action string
}
// setupEdns0Opt will retrieve the EDNS0 OPT or create it if it does not exist.
func setupEdns0Opt(r *dns.Msg) *dns.OPT {
o := r.IsEdns0()
if o == nil {
r.SetEdns0(4096, false)
o = r.IsEdns0()
}
return o
}
// Rewrite will alter the request EDNS0 NSID option
func (rule *edns0NsidRule) Rewrite(ctx context.Context, state request.Request) Result {
o := setupEdns0Opt(state.Req)
for _, s := range o.Option {
if e, ok := s.(*dns.EDNS0_NSID); ok {
if rule.action == Replace || rule.action == Set {
e.Nsid = "" // make sure it is empty for request
return RewriteDone
}
}
}
// add option if not found
if rule.action == Append || rule.action == Set {
o.Option = append(o.Option, &dns.EDNS0_NSID{Code: dns.EDNS0NSID, Nsid: ""})
return RewriteDone
}
return RewriteIgnored
}
// Mode returns the processing mode.
func (rule *edns0NsidRule) Mode() string { return rule.mode }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *edns0NsidRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// Rewrite will alter the request EDNS0 local options.
func (rule *edns0LocalRule) Rewrite(ctx context.Context, state request.Request) Result {
o := setupEdns0Opt(state.Req)
for _, s := range o.Option {
if e, ok := s.(*dns.EDNS0_LOCAL); ok {
if rule.code == e.Code {
if rule.action == Replace || rule.action == Set {
e.Data = rule.data
return RewriteDone
}
}
}
}
// add option if not found
if rule.action == Append || rule.action == Set {
o.Option = append(o.Option, &dns.EDNS0_LOCAL{Code: rule.code, Data: rule.data})
return RewriteDone
}
return RewriteIgnored
}
// Mode returns the processing mode.
func (rule *edns0LocalRule) Mode() string { return rule.mode }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *edns0LocalRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// newEdns0Rule creates an EDNS0 rule of the appropriate type based on the args
func newEdns0Rule(mode string, args ...string) (Rule, error) {
if len(args) < 2 {
return nil, fmt.Errorf("too few arguments for an EDNS0 rule")
}
ruleType := strings.ToLower(args[0])
action := strings.ToLower(args[1])
switch action {
case Append:
case Replace:
case Set:
default:
return nil, fmt.Errorf("invalid action: %q", action)
}
switch ruleType {
case "local":
if len(args) != 4 {
return nil, fmt.Errorf("EDNS0 local rules require exactly three args")
}
// Check for variable option.
if strings.HasPrefix(args[3], "{") && strings.HasSuffix(args[3], "}") {
return newEdns0VariableRule(mode, action, args[2], args[3])
}
return newEdns0LocalRule(mode, action, args[2], args[3])
case "nsid":
if len(args) != 2 {
return nil, fmt.Errorf("EDNS0 NSID rules do not accept args")
}
return &edns0NsidRule{mode: mode, action: action}, nil
case "subnet":
if len(args) != 4 {
return nil, fmt.Errorf("EDNS0 subnet rules require exactly three args")
}
return newEdns0SubnetRule(mode, action, args[2], args[3])
default:
return nil, fmt.Errorf("invalid rule type %q", ruleType)
}
}
func newEdns0LocalRule(mode, action, code, data string) (*edns0LocalRule, error) {
c, err := strconv.ParseUint(code, 0, 16)
if err != nil {
return nil, err
}
decoded := []byte(data)
if strings.HasPrefix(data, "0x") {
decoded, err = hex.DecodeString(data[2:])
if err != nil {
return nil, err
}
}
// Add this code to the ones the server supports.
edns.SetSupportedOption(uint16(c))
return &edns0LocalRule{mode: mode, action: action, code: uint16(c), data: decoded}, nil
}
// newEdns0VariableRule creates an EDNS0 rule that handles variable substitution
func newEdns0VariableRule(mode, action, code, variable string) (*edns0VariableRule, error) {
c, err := strconv.ParseUint(code, 0, 16)
if err != nil {
return nil, err
}
//Validate
if !isValidVariable(variable) {
return nil, fmt.Errorf("unsupported variable name %q", variable)
}
// Add this code to the ones the server supports.
edns.SetSupportedOption(uint16(c))
return &edns0VariableRule{mode: mode, action: action, code: uint16(c), variable: variable}, nil
}
// ruleData returns the data specified by the variable.
func (rule *edns0VariableRule) ruleData(ctx context.Context, state request.Request) ([]byte, error) {
switch rule.variable {
case queryName:
return []byte(state.QName()), nil
case queryType:
return uint16ToWire(state.QType()), nil
case clientIP:
return ipToWire(state.Family(), state.IP())
case serverIP:
return ipToWire(state.Family(), state.LocalIP())
case clientPort:
return portToWire(state.Port())
case serverPort:
return portToWire(state.LocalPort())
case protocol:
return []byte(state.Proto()), nil
}
fetcher := metadata.ValueFunc(ctx, rule.variable[1:len(rule.variable)-1])
if fetcher != nil {
value := fetcher()
if len(value) > 0 {
return []byte(value), nil
}
}
return nil, fmt.Errorf("unable to extract data for variable %s", rule.variable)
}
// Rewrite will alter the request EDNS0 local options with specified variables.
func (rule *edns0VariableRule) Rewrite(ctx context.Context, state request.Request) Result {
data, err := rule.ruleData(ctx, state)
if err != nil || data == nil {
return RewriteIgnored
}
o := setupEdns0Opt(state.Req)
for _, s := range o.Option {
if e, ok := s.(*dns.EDNS0_LOCAL); ok {
if rule.code == e.Code {
if rule.action == Replace || rule.action == Set {
e.Data = data
return RewriteDone
}
return RewriteIgnored
}
}
}
// add option if not found
if rule.action == Append || rule.action == Set {
o.Option = append(o.Option, &dns.EDNS0_LOCAL{Code: rule.code, Data: data})
return RewriteDone
}
return RewriteIgnored
}
// Mode returns the processing mode.
func (rule *edns0VariableRule) Mode() string { return rule.mode }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *edns0VariableRule) GetResponseRule() ResponseRule { return ResponseRule{} }
func isValidVariable(variable string) bool {
switch variable {
case
queryName,
queryType,
clientIP,
clientPort,
protocol,
serverIP,
serverPort:
return true
}
// we cannot validate the labels of metadata - but we can verify it has the syntax of a label
if strings.HasPrefix(variable, "{") && strings.HasSuffix(variable, "}") && metadata.IsLabel(variable[1:len(variable)-1]) {
return true
}
return false
}
// ends0SubnetRule is a rewrite rule for EDNS0 subnet options
type edns0SubnetRule struct {
mode string
v4BitMaskLen uint8
v6BitMaskLen uint8
action string
}
func newEdns0SubnetRule(mode, action, v4BitMaskLen, v6BitMaskLen string) (*edns0SubnetRule, error) {
v4Len, err := strconv.ParseUint(v4BitMaskLen, 0, 16)
if err != nil {
return nil, err
}
// validate V4 length
if v4Len > net.IPv4len*8 {
return nil, fmt.Errorf("invalid IPv4 bit mask length %d", v4Len)
}
v6Len, err := strconv.ParseUint(v6BitMaskLen, 0, 16)
if err != nil {
return nil, err
}
// validate V6 length
if v6Len > net.IPv6len*8 {
return nil, fmt.Errorf("invalid IPv6 bit mask length %d", v6Len)
}
return &edns0SubnetRule{mode: mode, action: action,
v4BitMaskLen: uint8(v4Len), v6BitMaskLen: uint8(v6Len)}, nil
}
// fillEcsData sets the subnet data into the ecs option
func (rule *edns0SubnetRule) fillEcsData(state request.Request, ecs *dns.EDNS0_SUBNET) error {
family := state.Family()
if (family != 1) && (family != 2) {
return fmt.Errorf("unable to fill data for EDNS0 subnet due to invalid IP family")
}
ecs.Family = uint16(family)
ecs.SourceScope = 0
ipAddr := state.IP()
switch family {
case 1:
ipv4Mask := net.CIDRMask(int(rule.v4BitMaskLen), 32)
ipv4Addr := net.ParseIP(ipAddr)
ecs.SourceNetmask = rule.v4BitMaskLen
ecs.Address = ipv4Addr.Mask(ipv4Mask).To4()
case 2:
ipv6Mask := net.CIDRMask(int(rule.v6BitMaskLen), 128)
ipv6Addr := net.ParseIP(ipAddr)
ecs.SourceNetmask = rule.v6BitMaskLen
ecs.Address = ipv6Addr.Mask(ipv6Mask).To16()
}
return nil
}
// Rewrite will alter the request EDNS0 subnet option.
func (rule *edns0SubnetRule) Rewrite(ctx context.Context, state request.Request) Result {
o := setupEdns0Opt(state.Req)
for _, s := range o.Option {
if e, ok := s.(*dns.EDNS0_SUBNET); ok {
if rule.action == Replace || rule.action == Set {
if rule.fillEcsData(state, e) == nil {
return RewriteDone
}
}
return RewriteIgnored
}
}
// add option if not found
if rule.action == Append || rule.action == Set {
opt := &dns.EDNS0_SUBNET{Code: dns.EDNS0SUBNET}
if rule.fillEcsData(state, opt) == nil {
o.Option = append(o.Option, opt)
return RewriteDone
}
}
return RewriteIgnored
}
// Mode returns the processing mode
func (rule *edns0SubnetRule) Mode() string { return rule.mode }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *edns0SubnetRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// These are all defined actions.
const (
Replace = "replace"
Set = "set"
Append = "append"
)
// Supported local EDNS0 variables
const (
queryName = "{qname}"
queryType = "{qtype}"
clientIP = "{client_ip}"
clientPort = "{client_port}"
protocol = "{protocol}"
serverIP = "{server_ip}"
serverPort = "{server_port}"
)