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Pull request: filtering: fix legacy rewrite wildcards

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Updates #3343.

Squashed commit of the following:

commit ab3c3e002a6d2a11bc3207fdaaeb292aaa194907
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Jul 12 20:58:57 2021 +0300

    filtering: fix legacy rewrite wildcards
This commit is contained in:
Ainar Garipov
2021-07-12 21:10:39 +03:00
parent f419896ec6
commit 194ea6ef95
4 changed files with 112 additions and 61 deletions
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89
internal/filtering/rewrites.go
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@@ -15,10 +15,16 @@ import (
// RewriteEntry is a rewrite array element
type RewriteEntry struct {
// Domain is the domain for which this rewrite should work.
Domain string `yaml:"domain"`
Answer string `yaml:"answer"` // IP address or canonical name
Type uint16 `yaml:"-"` // DNS record type: CNAME, A or AAAA
IP net.IP `yaml:"-"` // Parsed IP address (if Type is A or AAAA)
// Answer is the IP address, canonical name, or one of the special
// values: "A" or "AAAA".
Answer string `yaml:"answer"`
// IP is the IP address that should be used in the response if Type is
// A or AAAA.
IP net.IP `yaml:"-"`
// Type is the DNS record type: A, AAAA, or CNAME.
Type uint16 `yaml:"-"`
}
func (r *RewriteEntry) equals(b RewriteEntry) bool {
@@ -26,27 +32,32 @@ func (r *RewriteEntry) equals(b RewriteEntry) bool {
}
func isWildcard(host string) bool {
return len(host) >= 2 &&
host[0] == '*' && host[1] == '.'
return len(host) > 1 && host[0] == '*' && host[1] == '.'
}
// Return TRUE of host name matches a wildcard pattern
func matchDomainWildcard(host, wildcard string) bool {
return isWildcard(wildcard) &&
strings.HasSuffix(host, wildcard[1:])
// matchDomainWildcard returns true if host matches the wildcard pattern.
func matchDomainWildcard(host, wildcard string) (ok bool) {
return isWildcard(wildcard) && strings.HasSuffix(host, wildcard[1:])
}
type rewritesArray []RewriteEntry
// rewritesSorted is a slice of legacy rewrites for sorting.
//
// The sorting priority:
//
// A and AAAA > CNAME
// wildcard > exact
// lower level wildcard > higher level wildcard
//
type rewritesSorted []RewriteEntry
func (a rewritesArray) Len() int { return len(a) }
// Len implements the sort.Interface interface for legacyRewritesSorted.
func (a rewritesSorted) Len() int { return len(a) }
func (a rewritesArray) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// Swap implements the sort.Interface interface for legacyRewritesSorted.
func (a rewritesSorted) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// Priority:
// . CNAME < A/AAAA;
// . exact < wildcard;
// . higher level wildcard < lower level wildcard
func (a rewritesArray) Less(i, j int) bool {
// Less implements the sort.Interface interface for legacyRewritesSorted.
func (a rewritesSorted) Less(i, j int) bool {
if a[i].Type == dns.TypeCNAME && a[j].Type != dns.TypeCNAME {
return true
} else if a[i].Type != dns.TypeCNAME && a[j].Type == dns.TypeCNAME {
@@ -67,31 +78,37 @@ func (a rewritesArray) Less(i, j int) bool {
return len(a[i].Domain) > len(a[j].Domain)
}
// Prepare entry for use
// prepare prepares the a new or decoded entry.
func (r *RewriteEntry) prepare() {
if r.Answer == "AAAA" {
switch r.Answer {
case "AAAA":
r.IP = nil
r.Type = dns.TypeAAAA
return
} else if r.Answer == "A" {
case "A":
r.IP = nil
r.Type = dns.TypeA
return
default:
// Go on.
}
ip := net.ParseIP(r.Answer)
if ip == nil {
r.Type = dns.TypeCNAME
return
}
r.IP = ip
r.Type = dns.TypeAAAA
ip4 := ip.To4()
if ip4 != nil {
r.IP = ip4
r.Type = dns.TypeA
} else {
r.IP = ip
r.Type = dns.TypeAAAA
}
}
@@ -101,19 +118,23 @@ func (d *DNSFilter) prepareRewrites() {
}
}
// Get the list of matched rewrite entries.
// Priority: CNAME, A/AAAA; exact, wildcard.
// If matched exactly, don't return wildcard entries.
// If matched by several wildcards, select the more specific one
func findRewrites(a []RewriteEntry, host string) []RewriteEntry {
rr := rewritesArray{}
// findRewrites returns the list of matched rewrite entries. The priority is:
// CNAME, then A and AAAA; exact, then wildcard. If the host is matched
// exactly, wildcard entries aren't returned. If the host matched by wildcards,
// return the most specific for the question type.
func findRewrites(a []RewriteEntry, host string, qtype uint16) []RewriteEntry {
rr := rewritesSorted{}
for _, r := range a {
if r.Domain != host {
if !matchDomainWildcard(host, r.Domain) {
continue
}
if r.Domain != host && !matchDomainWildcard(host, r.Domain) {
continue
}
// Return CNAMEs for all types requests, but only the
// appropriate ones for A and AAAA.
if r.Type == dns.TypeCNAME ||
(r.Type == qtype && (qtype == dns.TypeA || qtype == dns.TypeAAAA)) {
rr = append(rr, r)
}
rr = append(rr, r)
}
if len(rr) == 0 {