Add tools/fetchacert.py, fetching exactly one chain from a log.

Also move a piece of common code from fetchallcerts.py to certtools.py.

3 files changed, 32 insertions, 10 deletions

diff --git a/tools/certtools.py b/tools/certtools.py
index 0e639f2..ffd631c 100644
--- a/tools/certtools.py
+++ b/tools/certtools.py
@@ -588,3 +588,13 @@ def verify_inclusion_proof(inclusion_proof, index, treesize, leafhash):
     chain = zip([(index, 0)] + nodes_for_index(index, treesize), [leafhash] + inclusion_proof)
     (_, hash) = reduce(lambda e1, e2: combine_two_hashes(e1, e2, treesize), chain)
     return hash
+
+def extract_original_entry(entry):
+    leaf_input =  base64.decodestring(entry["leaf_input"])
+    (leaf_cert, timestamp, issuer_key_hash) = unpack_mtl(leaf_input)
+    extra_data = base64.decodestring(entry["extra_data"])
+    if issuer_key_hash != None:
+        (precert, extra_data) = extract_precertificate(extra_data)
+        leaf_cert = precert
+    certchain = decode_certificate_chain(extra_data)
+    return ([leaf_cert] + certchain, timestamp, issuer_key_hash)
diff --git a/tools/fetchacert.py b/tools/fetchacert.py
new file mode 100755
index 0000000..82ea7c1
--- /dev/null
+++ b/tools/fetchacert.py
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import argparse
+import base64
+from certtools import *
+
+parser = argparse.ArgumentParser(description='')
+parser.add_argument('baseurl', help="Base URL for CT server")
+parser.add_argument('index', type=int, help="Index for entry to fetch")
+args = parser.parse_args()
+
+rawentries = get_entries(args.baseurl, args.index, args.index)["entries"]
+entry = extract_original_entry(rawentries[0])
+(chain, _timestamp, _issuer_key_hash) = entry
+s = ""
+for cert in chain:
+    s += "-----BEGIN CERTIFICATE-----\n"
+    s += base64.encodestring(cert).rstrip() + "\n"
+    s += "-----END CERTIFICATE-----\n"
+    s += "\n"
+print s
diff --git a/tools/fetchallcerts.py b/tools/fetchallcerts.py
index 398c563..e0ea92f 100755
--- a/tools/fetchallcerts.py
+++ b/tools/fetchallcerts.py
@@ -24,16 +24,6 @@ parser.add_argument('--store', default=None, metavar="dir", help='Store certific
 parser.add_argument('--write-sth', action='store_true', help='Write STH')
 args = parser.parse_args()
 
-def extract_original_entry(entry):
-    leaf_input =  base64.decodestring(entry["leaf_input"])
-    (leaf_cert, timestamp, issuer_key_hash) = unpack_mtl(leaf_input)
-    extra_data = base64.decodestring(entry["extra_data"])
-    if issuer_key_hash != None:
-        (precert, extra_data) = extract_precertificate(extra_data)
-        leaf_cert = precert
-    certchain = decode_certificate_chain(extra_data)
-    return ([leaf_cert] + certchain, timestamp, issuer_key_hash)
-
 def get_entries_wrapper(baseurl, start, end):
     fetched_entries = 0
     while start + fetched_entries < (end + 1):