diff --git a/quic/core/crypto/proof_source.h b/quic/core/crypto/proof_source.h
index da28612..e208b94 100644
--- a/quic/core/crypto/proof_source.h
+++ b/quic/core/crypto/proof_source.h
@@ -85,7 +85,13 @@
     //
     // |signature| contains the signature of the data provided to
     // ComputeTlsSignature. Its value is undefined if |ok| is false.
-    virtual void Run(bool ok, std::string signature) = 0;
+    //
+    // |details| holds a pointer to an object representing the statistics, if
+    // any, gathered during the operation of ComputeTlsSignature.  If no stats
+    // are available, this will be nullptr.
+    virtual void Run(bool ok,
+                     std::string signature,
+                     std::unique_ptr<Details> details) = 0;
 
    private:
     SignatureCallback(const SignatureCallback&) = delete;
diff --git a/quic/core/quic_crypto_client_handshaker_test.cc b/quic/core/quic_crypto_client_handshaker_test.cc
index 30dcbfc..9274b7e 100644
--- a/quic/core/quic_crypto_client_handshaker_test.cc
+++ b/quic/core/quic_crypto_client_handshaker_test.cc
@@ -99,7 +99,7 @@
       uint16_t /*signature_algorit*/,
       quiche::QuicheStringPiece /*in*/,
       std::unique_ptr<SignatureCallback> callback) override {
-    callback->Run(true, "Dummy signature");
+    callback->Run(true, "Dummy signature", /*details=*/nullptr);
   }
 };
 
diff --git a/quic/core/tls_server_handshaker.cc b/quic/core/tls_server_handshaker.cc
index e10c067..ced2bd4 100644
--- a/quic/core/tls_server_handshaker.cc
+++ b/quic/core/tls_server_handshaker.cc
@@ -21,13 +21,16 @@
     TlsServerHandshaker* handshaker)
     : handshaker_(handshaker) {}
 
-void TlsServerHandshaker::SignatureCallback::Run(bool ok,
-                                                 std::string signature) {
+void TlsServerHandshaker::SignatureCallback::Run(
+    bool ok,
+    std::string signature,
+    std::unique_ptr<ProofSource::Details> details) {
   if (handshaker_ == nullptr) {
     return;
   }
   if (ok) {
     handshaker_->cert_verify_sig_ = std::move(signature);
+    handshaker_->proof_source_details_ = std::move(details);
   }
   State last_state = handshaker_->state_;
   handshaker_->state_ = STATE_SIGNATURE_COMPLETE;
@@ -414,7 +417,8 @@
     return SSL_TLSEXT_ERR_ALERT_FATAL;
   }
 
-  QUIC_LOG(INFO) << "Set " << chain->certs.size() << " certs for server";
+  QUIC_LOG(INFO) << "Set " << chain->certs.size() << " certs for server "
+                 << "with hostname " << hostname_;
   return SSL_TLSEXT_ERR_OK;
 }
 
diff --git a/quic/core/tls_server_handshaker.h b/quic/core/tls_server_handshaker.h
index 22baf16..22ae45d 100644
--- a/quic/core/tls_server_handshaker.h
+++ b/quic/core/tls_server_handshaker.h
@@ -71,6 +71,10 @@
     return &tls_connection_;
   }
 
+  ProofSource::Details* proof_source_details() const {
+    return proof_source_details_.get();
+  }
+
   virtual void ProcessAdditionalTransportParameters(
       const TransportParameters& /*params*/) {}
 
@@ -109,7 +113,9 @@
       : public ProofSource::SignatureCallback {
    public:
     explicit SignatureCallback(TlsServerHandshaker* handshaker);
-    void Run(bool ok, std::string signature) override;
+    void Run(bool ok,
+             std::string signature,
+             std::unique_ptr<ProofSource::Details> details) override;
 
     // If called, Cancel causes the pending callback to be a no-op.
     void Cancel();
@@ -142,6 +148,7 @@
 
   std::string hostname_;
   std::string cert_verify_sig_;
+  std::unique_ptr<ProofSource::Details> proof_source_details_;
 
   // Used to hold the ENCRYPTION_FORWARD_SECURE read secret until the handshake
   // is complete. This is temporary until
diff --git a/quic/qbone/qbone_session_test.cc b/quic/qbone/qbone_session_test.cc
index 629d281..7ea1c51 100644
--- a/quic/qbone/qbone_session_test.cc
+++ b/quic/qbone/qbone_session_test.cc
@@ -100,7 +100,7 @@
       uint16_t signature_algorithm,
       quiche::QuicheStringPiece in,
       std::unique_ptr<SignatureCallback> callback) override {
-    callback->Run(true, "Signature");
+    callback->Run(true, "Signature", /*details=*/nullptr);
   }
 
  private:
diff --git a/quic/quartc/quartc_crypto_helpers.cc b/quic/quartc/quartc_crypto_helpers.cc
index e3b96ad..1a02845 100644
--- a/quic/quartc/quartc_crypto_helpers.cc
+++ b/quic/quartc/quartc_crypto_helpers.cc
@@ -39,7 +39,7 @@
     uint16_t /*signature_algorithm*/,
     quiche::QuicheStringPiece /*in*/,
     std::unique_ptr<SignatureCallback> callback) {
-  callback->Run(true, "Dummy signature");
+  callback->Run(true, "Dummy signature", /*details=*/nullptr);
 }
 
 QuicAsyncStatus InsecureProofVerifier::VerifyProof(
diff --git a/quic/test_tools/failing_proof_source.cc b/quic/test_tools/failing_proof_source.cc
index b71c6fd..1f52476 100644
--- a/quic/test_tools/failing_proof_source.cc
+++ b/quic/test_tools/failing_proof_source.cc
@@ -30,7 +30,7 @@
     uint16_t /*signature_algorithm*/,
     quiche::QuicheStringPiece /*in*/,
     std::unique_ptr<SignatureCallback> callback) {
-  callback->Run(false, "");
+  callback->Run(false, "", nullptr);
 }
 
 }  // namespace test
diff --git a/quic/test_tools/quic_test_client.cc b/quic/test_tools/quic_test_client.cc
index 1f95d22..5ddc879 100644
--- a/quic/test_tools/quic_test_client.cc
+++ b/quic/test_tools/quic_test_client.cc
@@ -57,6 +57,44 @@
       std::string* error_details,
       std::unique_ptr<ProofVerifyDetails>* details,
       std::unique_ptr<ProofVerifierCallback> callback) override {
+    QuicAsyncStatus process_certs_result = ProcessCerts(certs, cert_sct);
+    if (process_certs_result != QUIC_SUCCESS) {
+      return process_certs_result;
+    }
+
+    if (!verifier_) {
+      return QUIC_SUCCESS;
+    }
+
+    return verifier_->VerifyProof(hostname, port, server_config,
+                                  transport_version, chlo_hash, certs, cert_sct,
+                                  signature, context, error_details, details,
+                                  std::move(callback));
+  }
+
+  QuicAsyncStatus VerifyCertChain(
+      const std::string& /*hostname*/,
+      const std::vector<std::string>& certs,
+      const std::string& /*ocsp_response*/,
+      const std::string& cert_sct,
+      const ProofVerifyContext* /*context*/,
+      std::string* /*error_details*/,
+      std::unique_ptr<ProofVerifyDetails>* /*details*/,
+      std::unique_ptr<ProofVerifierCallback> /*callback*/) override {
+    return ProcessCerts(certs, cert_sct);
+  }
+
+  std::unique_ptr<ProofVerifyContext> CreateDefaultContext() override {
+    return verifier_ != nullptr ? verifier_->CreateDefaultContext() : nullptr;
+  }
+
+  const std::string& common_name() const { return common_name_; }
+
+  const std::string& cert_sct() const { return cert_sct_; }
+
+ private:
+  QuicAsyncStatus ProcessCerts(const std::vector<std::string>& certs,
+                               const std::string& cert_sct) {
     common_name_.clear();
     if (certs.empty()) {
       return QUIC_FAILURE;
@@ -79,38 +117,9 @@
 
     common_name_ = buf;
     cert_sct_ = cert_sct;
-
-    if (!verifier_) {
-      return QUIC_SUCCESS;
-    }
-
-    return verifier_->VerifyProof(hostname, port, server_config,
-                                  transport_version, chlo_hash, certs, cert_sct,
-                                  signature, context, error_details, details,
-                                  std::move(callback));
-  }
-
-  QuicAsyncStatus VerifyCertChain(
-      const std::string& /*hostname*/,
-      const std::vector<std::string>& /*certs*/,
-      const std::string& /*ocsp_response*/,
-      const std::string& /*cert_sct*/,
-      const ProofVerifyContext* /*context*/,
-      std::string* /*error_details*/,
-      std::unique_ptr<ProofVerifyDetails>* /*details*/,
-      std::unique_ptr<ProofVerifierCallback> /*callback*/) override {
     return QUIC_SUCCESS;
   }
 
-  std::unique_ptr<ProofVerifyContext> CreateDefaultContext() override {
-    return verifier_ != nullptr ? verifier_->CreateDefaultContext() : nullptr;
-  }
-
-  const std::string& common_name() const { return common_name_; }
-
-  const std::string& cert_sct() const { return cert_sct_; }
-
- private:
   std::unique_ptr<ProofVerifier> verifier_;
   std::string common_name_;
   std::string cert_sct_;