webauthn: add histogram for attestation prompt events.

Change-Id: Ib6c4ae24146e435585fe1ba064e26002d49b8f9c
Reviewed-on: https://chromium-review.googlesource.com/1224953Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591526}

content/browser/webauth/authenticator_impl.cc

@@ -12,6 +12,7 @@
 #include "base/base64url.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/rand_util.h"
 #include "base/strings/string_piece.h"
 #include "base/timer/timer.h"
@@ -67,6 +68,29 @@ const char kGetType[] = "webauthn.get";
 
 namespace {
 
+// AttestationPromptResult enumerates events related to attestation prompts.
+// These values are recorded in an UMA histogram and so should not be
+// reassigned.
+enum class AttestationPromptResult {
+  // kQueried indicates that the embedder was queried in order to determine
+  // whether attestation information should be returned to the origin.
+  kQueried = 0,
+  // kTimeout indicates that a timeout occured while awaiting the result of an
+  // attestation query.
+  kTimeout = 1,
+  // kAllowed indicates that the query to the embedder was resolved positively.
+  // (E.g. the user clicked to allow, or the embedded allowed immediately by
+  // policy.)
+  kAllowed = 2,
+  // kBlocked indicates that the query to the embedder was resolved negatively.
+  // (E.g. the user clicked to block, or closed the dialog.)
+  kBlocked = 3,
+  // kAbandoned indications that the user closed the tab or navigated away while
+  // the attestation prompt was showing.
+  kAbandoned = 4,
+  kMaxValue = kAbandoned,
+};
+
 // Ensure that the origin's effective domain is a valid domain.
 // Only the domain format of host is valid.
 // Reference https://url.spec.whatwg.org/#valid-domain-string and
@@ -770,6 +794,9 @@ void AuthenticatorImpl::OnRegisterResponse(
 
       if (attestation_preference_ !=
           blink::mojom::AttestationConveyancePreference::NONE) {
+        UMA_HISTOGRAM_ENUMERATION("WebAuthentication.AttestationPromptResult",
+                                  AttestationPromptResult::kQueried);
+        awaiting_attestation_response_ = true;
         request_delegate_->ShouldReturnAttestation(
             relying_party_id_,
             base::BindOnce(
@@ -794,6 +821,7 @@ void AuthenticatorImpl::OnRegisterResponse(
 void AuthenticatorImpl::OnRegisterResponseAttestationDecided(
     device::AuthenticatorMakeCredentialResponse response_data,
     bool attestation_permitted) {
+  awaiting_attestation_response_ = false;
   if (!request_) {
     // The request has already been cleaned up, probably because a navigation
     // occured while the permissions prompt was pending.
@@ -804,6 +832,8 @@ void AuthenticatorImpl::OnRegisterResponseAttestationDecided(
          blink::mojom::AttestationConveyancePreference::NONE);
 
   if (!attestation_permitted) {
+    UMA_HISTOGRAM_ENUMERATION("WebAuthentication.AttestationPromptResult",
+                              AttestationPromptResult::kBlocked);
     InvokeCallbackAndCleanup(
         std::move(make_credential_response_callback_),
         blink::mojom::AuthenticatorStatus::NOT_ALLOWED_ERROR, nullptr,
@@ -811,6 +841,8 @@ void AuthenticatorImpl::OnRegisterResponseAttestationDecided(
     return;
   }
 
+  UMA_HISTOGRAM_ENUMERATION("WebAuthentication.AttestationPromptResult",
+                            AttestationPromptResult::kAllowed);
   bool include_attestation = true;
 
   // The check for IsAttestationCertificateInappropriatelyIdentifying is
@@ -916,6 +948,12 @@ void AuthenticatorImpl::FailWithNotAllowedErrorAndCleanup() {
 
 void AuthenticatorImpl::OnTimeout() {
   DCHECK(request_delegate_);
+  if (awaiting_attestation_response_) {
+    UMA_HISTOGRAM_ENUMERATION("WebAuthentication.AttestationPromptResult",
+                              AttestationPromptResult::kTimeout);
+    awaiting_attestation_response_ = false;
+  }
+
   request_delegate_->DidFailWithInterestingReason(
       AuthenticatorRequestClientDelegate::InterestingFailureReason::kTimeout);
 
@@ -956,6 +994,12 @@ void AuthenticatorImpl::InvokeCallbackAndCleanup(
 }
 
 void AuthenticatorImpl::Cleanup() {
+  if (awaiting_attestation_response_) {
+    UMA_HISTOGRAM_ENUMERATION("WebAuthentication.AttestationPromptResult",
+                              AttestationPromptResult::kAbandoned);
+    awaiting_attestation_response_ = false;
+  }
+
   timer_->Stop();
   request_.reset();
   request_delegate_.reset();

content/browser/webauth/authenticator_impl.h

@@ -186,6 +186,9 @@ class CONTENT_EXPORT AuthenticatorImpl : public blink::mojom::Authenticator,
   // retried with this value.
   base::Optional<std::array<uint8_t, crypto::kSHA256Length>>
       alternative_application_parameter_;
+  // awaiting_attestation_response_ is true if the embedder has been queried
+  // about an attestsation decision and the response is still pending.
+  bool awaiting_attestation_response_ = false;
 
   // Owns pipes to this Authenticator from |render_frame_host_|.
   mojo::Binding<blink::mojom::Authenticator> binding_;

tools/metrics/histograms/enums.xml

@@ -51048,6 +51048,14 @@ Full version information for the fingerprint enum values:
   <int value="2" label="Source Node start()"/>
 </enum>
 
+<enum name="WebAuthenticationAttestationPromptResult">
+  <int value="0" label="Queried"/>
+  <int value="1" label="Timeout"/>
+  <int value="2" label="Allowed"/>
+  <int value="3" label="Blocked"/>
+  <int value="4" label="Abandoned"/>
+</enum>
+
 <enum name="WebBluetoothConnectGATTOutcome">
   <int value="0" label="Success"/>
   <int value="1" label="Device no longer in range"/>

tools/metrics/histograms/histograms.xml

@@ -114244,6 +114244,20 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="WebAuthentication.AttestationPromptResult"
+    enum="WebAuthenticationAttestationPromptResult">
+  <owner>agl@chromium.org</owner>
+  <summary>
+    Tracks events related to prompting users for permission to pass WebAuthn
+    attestation information back to origins. &quot;Queried&quot; means that the
+    embedder was queried for a decision. (Since such decisions can be resolved
+    by enterprise policy, that doesn't imply that a user saw a permissions
+    prompt in every case.) Then one of four things can happen: a timeout, a
+    positive or negative resolution, or the request is abandoned. The latter
+    case occurs when, for example, the tab is closed or the user navigates away.
+  </summary>
+</histogram>
+
 <histogram name="WebController.CertVerificationErrorsCacheHit"
     enum="BooleanCacheHit">
   <owner>eugenebut@chromium.org</owner>