Certificate Transparency: Parse Signed Tree Heads and validate them

net/cert/ct_serialization.h

Index: net/cert/ct_serialization.h
diff --git a/net/cert/ct_serialization.h b/net/cert/ct_serialization.h
index 19dc0873f4f1f809d256dae7d3fc322b2e95e9c4..a3855c92e567b648926e76c8edd3454a363df8e1 100644
--- a/net/cert/ct_serialization.h
+++ b/net/cert/ct_serialization.h
@@ -11,6 +11,7 @@
 #include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
 #include "net/cert/signed_certificate_timestamp.h"
+#include "net/cert/signed_tree_head.h"
 
 namespace net {
 
@@ -48,6 +49,11 @@ NET_EXPORT_PRIVATE bool EncodeV1SCTSignedData(
     const std::string& extensions,
     std::string* output);
 
+// Encodes the data signed by a Signed Tree Head (STH) |sth| into |output|.
+// The signature included in the |sth| can then be verified over these bytes.
+NET_EXPORT_PRIVATE void EncodeTreeHeadSignature(const SignedTreeHead& sth,
+                                                std::string* output);
+
 // Decode a list of Signed Certificate Timestamps
 // (SignedCertificateTimestampList as defined in RFC6962): from a single
 // string in |input| to a vector of individually-encoded SCTs |output|.