From 9c01188671322d92e29d9610697402ab049e8882 Mon Sep 17 00:00:00 2001
From: Grégoire Détrez <gregoire@mullvad.net>
Date: Mon, 5 Sep 2022 16:44:42 +0200
Subject: Modularize: ASCII serialization/deserialization

Add a sigsum.ascii module that handle Sigsum ASCII serialisation format
and an associated test module.
---
 sigsum-witness.py | 53 ++++++++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

(limited to 'sigsum-witness.py')

diff --git a/sigsum-witness.py b/sigsum-witness.py
index 5de433a..3f5ac38 100755
--- a/sigsum-witness.py
+++ b/sigsum-witness.py
@@ -23,7 +23,7 @@ import struct
 import sys
 import threading
 import time
-from binascii import hexlify, unhexlify
+from binascii import hexlify
 from hashlib import sha256
 from math import floor
 from pathlib import PurePath
@@ -34,6 +34,7 @@ import nacl.signing
 import prometheus_client as prometheus
 import requests
 
+from sigsum import ascii
 from tools.libsigntools import ssh_to_sign
 
 BASE_URL_DEFAULT = 'http://poc.sigsum.org:4780/'
@@ -169,44 +170,39 @@ def parse_keyval(text):
 
 class TreeHead:
     def __init__(self, sth_data):
-        self._text = parse_keyval(sth_data)
-        assert(len(self._text) == 4)
-        assert('timestamp' in self._text)
-        assert('tree_size' in self._text)
-        assert('root_hash' in self._text)
-        assert('signature' in self._text)
+        self._data = ascii.loads(sth_data)
+        assert(len(self._data) == 4)
+        assert('timestamp' in self._data)
+        assert('tree_size' in self._data)
+        assert('root_hash' in self._data)
+        assert('signature' in self._data)
 
     @property
     def timestamp(self):
-        return int(self._text['timestamp'])
+        return self._data.getint('timestamp')
 
     @property
     def tree_size(self):
-        return int(self._text['tree_size'])
+        return self._data.getint('tree_size')
 
     @property
     def root_hash(self):
-        return unhexlify(self._text['root_hash'])
+        return self._data.getbytes('root_hash')
 
     def text(self):
-        text = 'timestamp={}\n'.format(self._text['timestamp'])
-        text += 'tree_size={}\n'.format(self._text['tree_size'])
-        text += 'root_hash={}\n'.format(self._text['root_hash'])
-        text += 'signature={}\n'.format(self._text['signature'])
-        return text.encode('ascii')
+        return ascii.dumps(self._data).encode('ascii')
 
     def to_signed_data(self, pubkey):
         namespace = 'tree_head:v0:{}@sigsum.org'.format(hexlify(sha256(pubkey.encode()).digest()).decode())
         msg = struct.pack('!QQ', self.timestamp, self.tree_size)
-        msg += unhexlify(self._text['root_hash'])
+        msg += self.root_hash
         assert(len(msg) == 8 + 8 + 32)
         return ssh_to_sign(namespace, 'sha256', sha256(msg).digest())
 
     def signature_valid(self, pubkey):
         # Guard against tree head with >1 signature -- don't try to
         # validate a cosigned tree head.
-        assert(type(self._text['signature']) is str)
-        sig = unhexlify(self._text['signature'])
+        sig = self._data.getbytes('signature')
         assert(len(sig) == 64)
         data = self.to_signed_data(pubkey)
         try:
@@ -286,19 +282,18 @@ class ConsistencyProof():
     def __init__(self, old_size, new_size, consistency_proof_data):
         self._old_size = old_size
         self._new_size = new_size
-        self._text = parse_keyval(consistency_proof_data)
-        assert(len(self._text) == 1)
-        assert('consistency_path' in self._text)
+        self._data = ascii.loads(consistency_proof_data)
+        assert(len(self._data) == 1)
+        assert('consistency_path' in self._data)
 
     def old_size(self):
         return self._old_size
     def new_size(self):
         return self._new_size
+
     def path(self):
-        if type(self._text['consistency_path']) is list:
-            return [unhexlify(e) for e in self._text['consistency_path']]
-        else:
-            return [unhexlify(self._text['consistency_path'])]
+        return self._data.getbytes('consistency_path', many=True)
+
 
 def make_base_dir_maybe():
     dirname = os.path.expanduser(g_args.base_dir)
@@ -410,10 +405,10 @@ def consistency_proof_valid(first, second, proof):
 def sign_send_store_tree_head(signing_key, log_key, tree_head):
     signature = signing_key.sign(tree_head.to_signed_data(log_key)).signature
     hash = sha256(signing_key.verify_key.encode())
-
-    post_data = 'cosignature={}\n'.format(hexlify(signature).decode('ascii'))
-    post_data += 'key_hash={}\n'.format(hash.hexdigest())
-
+    post_data = ascii.dumps({
+        'cosignature': signature.hex(),
+        'key_hash': hash.hexdigest(),
+    })
     try:
         req = requests.post(g_args.base_url + 'sigsum/v0/add-cosignature', post_data)
     except requests.ConnectionError as err:
-- 
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