Bug 1635566 - TRR: Perform a case-insensitive match for the host name r=necko-reviewers,dragana

This is according to RFC 4343 : Domain Name System (DNS) Case Insensitivity Clarification

Differential Revision: https://phabricator.services.mozilla.com/D75081

netwerk/dns/TRR.cpp

@@ -873,10 +873,14 @@ nsresult TRR::DohDecode(nsCString& aHost) {
       return NS_ERROR_ILLEGAL_VALUE;
     }
 
-    // We check if the qname matches the host or the FQDN version of the host
-    if (qname.Equals(aHost) ||
-        (aHost.Length() == qname.Length() + 1 && aHost.Last() == '.' &&
-         StringBeginsWith(aHost, qname))) {
+    // We check if the qname is a case-insensitive match for the host or the
+    // FQDN version of the host
+    bool responseMatchesQuestion =
+        (qname.Length() == aHost.Length() ||
+         (aHost.Length() == qname.Length() + 1 && aHost.Last() == '.')) &&
+        qname.Compare(aHost.BeginReading(), true, qname.Length()) == 0;
+
+    if (responseMatchesQuestion) {
       // RDATA
       // - A (TYPE 1):  4 bytes
       // - AAAA (TYPE 28): 16 bytes

netwerk/test/unit/test_trr_case_sensitivity.js

@@ -125,5 +125,17 @@ add_task(async function test_trr_casing() {
   ]);
   await new TRRDNSListener("a.test.com", "8.8.8.8");
 
+  await trrServer.registerDoHAnswers("CAPITAL.COM", "A", [
+    {
+      name: "capital.com",
+      ttl: 55,
+      type: "A",
+      flush: false,
+      data: "2.2.2.2",
+    },
+  ]);
+  await new TRRDNSListener("CAPITAL.COM", "2.2.2.2");
+  await new TRRDNSListener("CAPITAL.COM.", "2.2.2.2");
+
   await trrServer.stop();
 });