From f6bb4413466aa2588bcb7d22b9e6bf97885f16d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mat=C4=9Bj=20Cepl?= <mcepl@cepl.eu>
Date: Wed, 29 Jan 2020 20:16:11 +0100
Subject: NULL is legal argument for key and iv paramters of EVP_CipherInit(3)

Fixes #272
---
 SWIG/_evp.i       | 13 +++++++++++--
 tests/test_evp.py |  5 +++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/SWIG/_evp.i b/SWIG/_evp.i
index d04e806..9a3b67b 100644
--- a/SWIG/_evp.i
+++ b/SWIG/_evp.i
@@ -430,8 +430,17 @@ PyObject *cipher_init(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
     const void *kbuf, *ibuf;
     Py_ssize_t klen, ilen;
 
-    if ((PyObject_AsReadBuffer(key, &kbuf, &klen) == -1)
-        || (PyObject_AsReadBuffer(iv, &ibuf, &ilen) == -1))
+    if (cipher == Py_None)
+        cipher = NULL;
+
+    if (key == Py_None)
+        kbuf = NULL;
+    else if (PyObject_AsReadBuffer(key, &kbuf, &klen) == -1)
+        return NULL;
+
+    if (iv == Py_None)
+        ibuf = NULL;
+    else if (PyObject_AsReadBuffer(iv, &ibuf, &ilen) == -1)
         return NULL;
 
     if (!EVP_CipherInit(ctx, cipher, (unsigned char *)kbuf,
diff --git a/tests/test_evp.py b/tests/test_evp.py
index d133ed0..fff7127 100644
--- a/tests/test_evp.py
+++ b/tests/test_evp.py
@@ -517,6 +517,11 @@ class CipherTestCase(unittest.TestCase):
                 unhexlify('5cd148eeaf680d4ff933aed83009cad4110162f53ef89fd44fad09611b0524d4'),
                 unhexlify(''))
 
+    def test_cipher_init_reinit(self):
+        ctx = m2.cipher_ctx_new()
+        m2.cipher_init(ctx, m2.aes_128_cbc(), b'\x01' * (128//8), b'\x02' * (128//8), 1)
+        m2.cipher_init(ctx, m2.aes_128_cbc(), None, None, 1)
+
 
 class PBKDF2TestCase(unittest.TestCase):
     def test_rfc3211_test_vectors(self):
-- 
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