Validate Service Certificates Before Accepting Them

(This is a merge of http://go/wvgerrit/14630)

To create a better flow when an application sets a service certificate
manually, we will now validate the certificate when it is given to us,
and if it is invalid, we will not allow the property to be set.

Bug: 21307186
Change-Id: If980ad075604223fc962a859fae93e98d86a7f4f

libwvdrmengine/mediadrm/src/WVDrmPlugin.cpp

@@ -585,7 +585,11 @@ status_t WVDrmPlugin::setPropertyByteArray(const String8& name,
                                            const Vector<uint8_t>& value) {
   if (name == "serviceCertificate") {
     std::string cert(value.begin(), value.end());
-    mPropertySet.set_service_certificate(cert);
+    if (WvContentDecryptionModule::IsValidServiceCertificate(cert)) {
+      mPropertySet.set_service_certificate(cert);
+    } else {
+      return android::BAD_VALUE;
+    }
   } else {
     ALOGE("App set unknown byte array property %s", name.string());
     return android::ERROR_DRM_CANNOT_HANDLE;