Bug 1649472 - Add telemetry for PHA in TLS 1.3 r=jcj,keeler

Differential Revision: https://phabricator.services.mozilla.com/D81715

security/manager/ssl/nsNSSIOLayer.cpp

@@ -1911,6 +1911,10 @@ SECStatus nsNSS_SSLGetClientAuthData(void* arg, PRFileDesc* socket,
     info->SetSentClientCert();
     Telemetry::ScalarAdd(Telemetry::ScalarID::SECURITY_CLIENT_CERT, u"sent"_ns,
                          1);
+    if (info->GetSSLVersionUsed() == nsISSLSocketControl::TLS_VERSION_1_3) {
+        Telemetry::Accumulate(Telemetry::TLS_1_3_CLIENT_AUTH_USES_PHA,
+                              info->IsHandshakeCompleted());
+    }
   }
 
   return SECSuccess;

toolkit/components/telemetry/Histograms.json

@@ -15127,6 +15127,16 @@
     "releaseChannelCollection": "opt-out",
     "description": "Whether a child process successfully mapped the User Agent style sheet shared memory buffer at the desired address"
   },
+  "TLS_1_3_CLIENT_AUTH_USES_PHA": {
+    "record_in_processes": ["main"],
+    "products": ["firefox", "fennec"],
+    "alert_emails": ["mbirghan@mozilla.com", "seceng-telemetry@mozilla.com"],
+    "bug_numbers": [1649472],
+    "releaseChannelCollection": "opt-out",
+    "expires_in_version": "99",
+    "kind": "boolean",
+    "description": "Whether TLS 1.3 client authentication uses PHA (true) or regular in-handshake authentication (false)"
+  },
   "TLS_DELEGATED_CREDENTIALS_TIME_UNTIL_READY_MS": {
     "record_in_processes": ["main"],
     "products": ["firefox", "fennec"],