forked from coredns/coredns
/
name.go
309 lines (281 loc) · 9.44 KB
/
name.go
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package rewrite
import (
"context"
"fmt"
"regexp"
"strconv"
"strings"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
type exactNameRule struct {
NextAction string
From string
To string
ResponseRule
}
type prefixNameRule struct {
NextAction string
Prefix string
Replacement string
}
type suffixNameRule struct {
NextAction string
Suffix string
Replacement string
}
type substringNameRule struct {
NextAction string
Substring string
Replacement string
}
type regexNameRule struct {
NextAction string
Pattern *regexp.Regexp
Replacement string
ResponseRule
}
const (
// ExactMatch matches only on exact match of the name in the question section of a request
ExactMatch = "exact"
// PrefixMatch matches when the name begins with the matching string
PrefixMatch = "prefix"
// SuffixMatch matches when the name ends with the matching string
SuffixMatch = "suffix"
// SubstringMatch matches on partial match of the name in the question section of a request
SubstringMatch = "substring"
// RegexMatch matches when the name in the question section of a request matches a regular expression
RegexMatch = "regex"
)
// Rewrite rewrites the current request based upon exact match of the name
// in the question section of the request.
func (rule *exactNameRule) Rewrite(ctx context.Context, state request.Request) Result {
if rule.From == state.Name() {
state.Req.Question[0].Name = rule.To
return RewriteDone
}
return RewriteIgnored
}
// Rewrite rewrites the current request when the name begins with the matching string.
func (rule *prefixNameRule) Rewrite(ctx context.Context, state request.Request) Result {
if strings.HasPrefix(state.Name(), rule.Prefix) {
state.Req.Question[0].Name = rule.Replacement + strings.TrimLeft(state.Name(), rule.Prefix)
return RewriteDone
}
return RewriteIgnored
}
// Rewrite rewrites the current request when the name ends with the matching string.
func (rule *suffixNameRule) Rewrite(ctx context.Context, state request.Request) Result {
if strings.HasSuffix(state.Name(), rule.Suffix) {
state.Req.Question[0].Name = strings.TrimRight(state.Name(), rule.Suffix) + rule.Replacement
return RewriteDone
}
return RewriteIgnored
}
// Rewrite rewrites the current request based upon partial match of the
// name in the question section of the request.
func (rule *substringNameRule) Rewrite(ctx context.Context, state request.Request) Result {
if strings.Contains(state.Name(), rule.Substring) {
state.Req.Question[0].Name = strings.Replace(state.Name(), rule.Substring, rule.Replacement, -1)
return RewriteDone
}
return RewriteIgnored
}
// Rewrite rewrites the current request when the name in the question
// section of the request matches a regular expression.
func (rule *regexNameRule) Rewrite(ctx context.Context, state request.Request) Result {
regexGroups := rule.Pattern.FindStringSubmatch(state.Name())
if len(regexGroups) == 0 {
return RewriteIgnored
}
s := rule.Replacement
for groupIndex, groupValue := range regexGroups {
groupIndexStr := "{" + strconv.Itoa(groupIndex) + "}"
if strings.Contains(s, groupIndexStr) {
s = strings.Replace(s, groupIndexStr, groupValue, -1)
}
}
state.Req.Question[0].Name = s
return RewriteDone
}
// newNameRule creates a name matching rule based on exact, partial, or regex match
func newNameRule(nextAction string, args ...string) (Rule, error) {
var matchType, rewriteQuestionFrom, rewriteQuestionTo string
var rewriteAnswerField, rewriteAnswerFrom, rewriteAnswerTo string
if len(args) < 2 {
return nil, fmt.Errorf("too few arguments for a name rule")
}
if len(args) == 2 {
matchType = "exact"
rewriteQuestionFrom = plugin.Name(args[0]).Normalize()
rewriteQuestionTo = plugin.Name(args[1]).Normalize()
}
if len(args) >= 3 {
matchType = strings.ToLower(args[0])
rewriteQuestionFrom = plugin.Name(args[1]).Normalize()
rewriteQuestionTo = plugin.Name(args[2]).Normalize()
}
if matchType == RegexMatch {
rewriteQuestionFrom = args[1]
rewriteQuestionTo = args[2]
}
if matchType == ExactMatch || matchType == SuffixMatch {
if !hasClosingDot(rewriteQuestionFrom) {
rewriteQuestionFrom = rewriteQuestionFrom + "."
}
if !hasClosingDot(rewriteQuestionTo) {
rewriteQuestionTo = rewriteQuestionTo + "."
}
}
if len(args) > 3 && len(args) != 7 {
return nil, fmt.Errorf("response rewrites must consist only of a name rule with 3 arguments and an answer rule with 3 arguments")
}
if len(args) < 7 {
switch matchType {
case ExactMatch:
rewriteAnswerFromPattern, err := isValidRegexPattern(rewriteQuestionTo, rewriteQuestionFrom)
if err != nil {
return nil, err
}
return &exactNameRule{
nextAction,
rewriteQuestionFrom,
rewriteQuestionTo,
ResponseRule{
Active: true,
Type: "name",
Pattern: rewriteAnswerFromPattern,
Replacement: rewriteQuestionFrom,
},
}, nil
case PrefixMatch:
return &prefixNameRule{
nextAction,
rewriteQuestionFrom,
rewriteQuestionTo,
}, nil
case SuffixMatch:
return &suffixNameRule{
nextAction,
rewriteQuestionFrom,
rewriteQuestionTo,
}, nil
case SubstringMatch:
return &substringNameRule{
nextAction,
rewriteQuestionFrom,
rewriteQuestionTo,
}, nil
case RegexMatch:
rewriteQuestionFromPattern, err := isValidRegexPattern(rewriteQuestionFrom, rewriteQuestionTo)
if err != nil {
return nil, err
}
rewriteQuestionTo := plugin.Name(args[2]).Normalize()
return ®exNameRule{
nextAction,
rewriteQuestionFromPattern,
rewriteQuestionTo,
ResponseRule{
Type: "name",
},
}, nil
default:
return nil, fmt.Errorf("A name rule supports only exact, prefix, suffix, substring, and regex name matching, received: %s", matchType)
}
}
if len(args) == 7 {
if matchType == RegexMatch {
if args[3] != "answer" {
return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
}
rewriteQuestionFromPattern, err := isValidRegexPattern(rewriteQuestionFrom, rewriteQuestionTo)
if err != nil {
return nil, err
}
rewriteAnswerField = strings.ToLower(args[4])
switch rewriteAnswerField {
case "name":
default:
return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
}
rewriteAnswerFrom = args[5]
rewriteAnswerTo = args[6]
rewriteAnswerFromPattern, err := isValidRegexPattern(rewriteAnswerFrom, rewriteAnswerTo)
if err != nil {
return nil, err
}
rewriteQuestionTo = plugin.Name(args[2]).Normalize()
rewriteAnswerTo = plugin.Name(args[6]).Normalize()
return ®exNameRule{
nextAction,
rewriteQuestionFromPattern,
rewriteQuestionTo,
ResponseRule{
Active: true,
Type: "name",
Pattern: rewriteAnswerFromPattern,
Replacement: rewriteAnswerTo,
},
}, nil
}
return nil, fmt.Errorf("the rewrite of response is supported only for name regex rule")
}
return nil, fmt.Errorf("the rewrite rule is invalid: %s", args)
}
// Mode returns the processing nextAction
func (rule *exactNameRule) Mode() string { return rule.NextAction }
func (rule *prefixNameRule) Mode() string { return rule.NextAction }
func (rule *suffixNameRule) Mode() string { return rule.NextAction }
func (rule *substringNameRule) Mode() string { return rule.NextAction }
func (rule *regexNameRule) Mode() string { return rule.NextAction }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *exactNameRule) GetResponseRule() ResponseRule { return rule.ResponseRule }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *prefixNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *suffixNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
func (rule *substringNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
// GetResponseRule return a rule to rewrite the response with.
func (rule *regexNameRule) GetResponseRule() ResponseRule { return rule.ResponseRule }
// validName returns true if s is valid domain name and shorter than 256 characters.
func validName(s string) bool {
_, ok := dns.IsDomainName(s)
if !ok {
return false
}
if len(dns.Name(s).String()) > 255 {
return false
}
return true
}
// hasClosingDot return true if s has a closing dot at the end.
func hasClosingDot(s string) bool {
if strings.HasSuffix(s, ".") {
return true
}
return false
}
// getSubExprUsage return the number of subexpressions used in s.
func getSubExprUsage(s string) int {
subExprUsage := 0
for i := 0; i <= 100; i++ {
if strings.Contains(s, "{"+strconv.Itoa(i)+"}") {
subExprUsage++
}
}
return subExprUsage
}
// isValidRegexPattern return a regular expression for pattern matching or errors, if any.
func isValidRegexPattern(rewriteFrom, rewriteTo string) (*regexp.Regexp, error) {
rewriteFromPattern, err := regexp.Compile(rewriteFrom)
if err != nil {
return nil, fmt.Errorf("Invalid regex matching pattern: %s", rewriteFrom)
}
if getSubExprUsage(rewriteTo) > rewriteFromPattern.NumSubexp() {
return nil, fmt.Errorf("The rewrite regex pattern (%s) uses more subexpressions than its corresponding matching regex pattern (%s)", rewriteTo, rewriteFrom)
}
return rewriteFromPattern, nil
}