From db1c5cf0eeba9b47a3f89bebc1abd9985ee9fef7 Mon Sep 17 00:00:00 2001
From: Magnus Ahltorp <map@kth.se>
Date: Thu, 26 Mar 2015 23:59:30 +0100
Subject: Provide function for calculating entryhash from entry

---
 Makefile               |  2 +-
 src/catlfish.erl       | 25 +++++++++++++++++++++++++
 tools/compileconfig.py |  2 ++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index cd445e3..58a1160 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 build all:
-	erl -pa ../lager/ebin -make
+	./make.erl
 clean:
 	-rm ebin/*.beam
 release: all
diff --git a/src/catlfish.erl b/src/catlfish.erl
index 2e5ffd4..ed75495 100644
--- a/src/catlfish.erl
+++ b/src/catlfish.erl
@@ -5,6 +5,7 @@
 -export([add_chain/3, entries/2, entry_and_proof/2]).
 -export([known_roots/0, update_known_roots/0]).
 -export([init_cache_table/0]).
+-export([entryhash_from_entry/1]).
 -include_lib("eunit/include/eunit.hrl").
 
 -define(PROTOCOL_VERSION, 0).
@@ -243,6 +244,30 @@ init_cache_table() ->
     end,
     ets:new(?CACHE_TABLE, [set, public, named_table]).
 
+deserialise_extra_data(ExtraData) ->
+    case decode_tls_vector(ExtraData, 3) of
+        {E, <<>>} ->
+            [E];
+        {E, Rest} ->
+            [E | deserialise_extra_data(Rest)]
+    end.
+
+entryhash_from_entry(Entry) ->
+    {MTLText, ExtraDataPacked} = unpack_entry(Entry),
+    {ExtraData, <<>>} = decode_tls_vector(ExtraDataPacked, 3),
+    MTL = deserialise_mtl(MTLText),
+    TimestampedEntry = MTL#mtl.entry,
+    Chain = deserialise_extra_data(ExtraData),
+    Data =
+        case TimestampedEntry#timestamped_entry.entry_type of
+            x509_entry ->
+                SignedEntry = TimestampedEntry#timestamped_entry.signed_entry,
+                [SignedEntry#signed_x509_entry.asn1_cert | Chain];
+            precert_entry ->
+                Chain
+        end,
+    crypto:hash(sha256, Data).
+
 %% Private functions.
 -spec unpack_entry(binary()) -> {binary(), binary()}.
 unpack_entry(Entry) ->
diff --git a/tools/compileconfig.py b/tools/compileconfig.py
index 30424c5..e3d9ee0 100755
--- a/tools/compileconfig.py
+++ b/tools/compileconfig.py
@@ -188,6 +188,8 @@ def gen_config(nodename, config, localconfig):
     if nodetype == "frontendnodes":
         plopconfig += [
             (Symbol("sth_path"), paths["db"] + "sth"),
+            (Symbol("entryhash_from_entry"),
+             (Symbol("catlfish"), Symbol("entryhash_from_entry"))),
         ]
 
     signingnode = config["signingnodes"][0]
-- 
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