From 7f347cd59faee6a0fb08fe58f3c92d754153d61a Mon Sep 17 00:00:00 2001
From: Fred Gylys-Colwell <fredgc@google.com>
Date: Mon, 13 Jul 2020 10:12:37 -0700
Subject: [PATCH] Adjust nonce for v15 servers

Merge from Widevine repo of http://go/wvgerrit/102783

When OEMCrypto is v16, but the license server is v15, we should not
create a new nonce for a license renewal. However, the request does
need a nonce or the license server will not generate a valid key
control block. So we should use the nonce that came from the original
license.

Bug: 160676790
Test: tested playback using netflix
Test: GTS tests. http://go/forrest-run/L55100000642199761
Change-Id: Ie1644b5abe0662387edf01f6110d82f70a64df6c
---
 libwvdrmengine/cdm/core/include/license.h |  3 +++
 libwvdrmengine/cdm/core/src/license.cpp   | 19 +++++++++++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/libwvdrmengine/cdm/core/include/license.h b/libwvdrmengine/cdm/core/include/license.h
index 95c307e4..9d566803 100644
--- a/libwvdrmengine/cdm/core/include/license.h
+++ b/libwvdrmengine/cdm/core/include/license.h
@@ -176,6 +176,9 @@ class CdmLicense {
   // HandleKeyResponse
   VersionInfo latest_service_version_;
 
+  // The nonce used in the original license request.
+  uint32_t license_nonce_;
+
 #if defined(UNIT_TEST)
   friend class CdmLicenseTestPeer;
 #endif
diff --git a/libwvdrmengine/cdm/core/src/license.cpp b/libwvdrmengine/cdm/core/src/license.cpp
index a6585d34..a934571c 100644
--- a/libwvdrmengine/cdm/core/src/license.cpp
+++ b/libwvdrmengine/cdm/core/src/license.cpp
@@ -237,6 +237,7 @@ bool CdmLicense::Init(const std::string& client_token,
   crypto_session_ = session;
   policy_engine_ = policy_engine;
   use_privacy_mode_ = use_privacy_mode;
+  license_nonce_ = 0;
   initialized_ = true;
   return true;
 }
@@ -313,8 +314,7 @@ CdmResponseType CdmLicense::PrepareKeyRequest(
 
   // Get/set the nonce.  This value will be reflected in the Key Control Block
   // of the license response.
-  uint32_t nonce;
-  status = crypto_session_->GenerateNonce(&nonce);
+  status = crypto_session_->GenerateNonce(&license_nonce_);
 
   switch (status) {
     case NO_ERROR:
@@ -325,7 +325,7 @@ CdmResponseType CdmLicense::PrepareKeyRequest(
     default:
       return LICENSE_REQUEST_NONCE_GENERATION_ERROR;
   }
-  license_request.set_key_control_nonce(nonce);
+  license_request.set_key_control_nonce(license_nonce_);
   license_request.set_protocol_version(video_widevine::VERSION_2_1);
 
   // License request is complete. Serialize it.
@@ -460,11 +460,11 @@ CdmResponseType CdmLicense::PrepareKeyUpdateRequest(
     LOGW("Unknown API Version");
     api_version = 15;
   }
-  uint32_t nonce = 0;
   if (api_version < 16) {
     // For a pre-v16 license, get/set the nonce.  This value will be reflected
     // in the Key Control Block of the license response.
-    const CdmResponseType status = crypto_session_->GenerateNonce(&nonce);
+    const CdmResponseType status =
+        crypto_session_->GenerateNonce(&license_nonce_);
     switch (status) {
       case NO_ERROR:
         break;
@@ -475,7 +475,7 @@ CdmResponseType CdmLicense::PrepareKeyUpdateRequest(
         return LICENSE_RENEWAL_NONCE_GENERATION_ERROR;
     }
   }
-  license_request.set_key_control_nonce(nonce);
+  license_request.set_key_control_nonce(license_nonce_);
   license_request.set_protocol_version(video_widevine::VERSION_2_1);
 
   // License request is complete. Serialize it.
@@ -810,6 +810,13 @@ CdmResponseType CdmLicense::RestoreOfflineLicense(
   }
 
   key_request_ = signed_request.msg();
+  LicenseRequest original_license_request;
+  if (!original_license_request.ParseFromString(key_request_)) {
+    LOGW("Could not parse original request.");
+  } else {
+    license_nonce_ = original_license_request.key_control_nonce();
+  }
+
   CdmResponseType sts = HandleKeyResponse(license_response);
 
   if (sts != KEY_ADDED) return sts;