Pull request: filtering: fix legacy rewrite domain case

Updates #3351.

Squashed commit of the following:

commit cc1c72cc13026ed703bb140e55dc3eb886846e48
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Jul 13 17:23:33 2021 +0300

    filtering: fix legacy rewrite domain case

CHANGELOG.md

@@ -62,6 +62,7 @@ released by then.
 
 ### Fixed
 
+- Domain name letter case mismatches in DNS rewrites ([#3351]).
 - Conflicts between IPv4 and IPv6 DNS rewrites ([#3343]).
 - Letter case mismatches in `CNAME` filtering ([#3335]).
 - Occasional breakages on network errors with DNS-over-HTTP upstreams ([#3217]).
@@ -105,6 +106,7 @@ released by then.
 [#3257]: https://github.com/AdguardTeam/AdGuardHome/issues/3257
 [#3335]: https://github.com/AdguardTeam/AdGuardHome/issues/3335
 [#3343]: https://github.com/AdguardTeam/AdGuardHome/issues/3343
+[#3351]: https://github.com/AdguardTeam/AdGuardHome/issues/3351
 
 
 

internal/filtering/rewrites.go

@@ -80,6 +80,11 @@ func (a rewritesSorted) Less(i, j int) bool {
 
 // prepare prepares the a new or decoded entry.
 func (r *RewriteEntry) prepare() {
+	// TODO(a.garipov): Write a case-agnostic version of strings.HasSuffix
+	// and use it in matchDomainWildcard instead of using strings.ToLower
+	// everywhere.
+	r.Domain = strings.ToLower(r.Domain)
+
 	switch r.Answer {
 	case "AAAA":
 		r.IP = nil

internal/filtering/rewrites_test.go

@@ -63,6 +63,9 @@ func TestRewrites(t *testing.T) {
 	}, {
 		Domain: "*.hostboth.com",
 		Answer: "1234::5678",
+	}, {
+		Domain: "BIGHOST.COM",
+		Answer: "1.2.3.7",
 	}}
 	d.prepareRewrites()
 
@@ -126,6 +129,12 @@ func TestRewrites(t *testing.T) {
 		wantCName: "",
 		wantVals:  []net.IP{net.ParseIP("1234::5678")},
 		dtyp:      dns.TypeAAAA,
+	}, {
+		name:      "issue3351",
+		host:      "bighost.com",
+		wantCName: "",
+		wantVals:  []net.IP{{1, 2, 3, 7}},
+		dtyp:      dns.TypeA,
 	}}
 
 	for _, tc := range testCases {
@@ -139,7 +148,8 @@ func TestRewrites(t *testing.T) {
 				return
 			}
 
-			require.Equal(t, Rewritten, r.Reason)
+			require.Equalf(t, Rewritten, r.Reason, "got %s", r.Reason)
+
 			if tc.wantCName != "" {
 				assert.Equal(t, tc.wantCName, r.CanonName)
 			}
@@ -319,7 +329,7 @@ func TestRewritesExceptionIP(t *testing.T) {
 				return
 			}
 
-			assert.Equal(t, Rewritten, r.Reason)
+			assert.Equalf(t, Rewritten, r.Reason, "got %s", r.Reason)
 
 			require.Len(t, r.IPList, len(tc.want))