Fix decrypt in FFI/Python. Github issue 53

6 files changed, 30 insertions, 7 deletions

diff --git a/botan_version.py b/botan_version.py
index 1aa794863..fae0cd228 100644
--- a/botan_version.py
+++ b/botan_version.py
@@ -1,7 +1,7 @@
 
 release_major = 1
 release_minor = 11
-release_patch = 14
+release_patch = 15
 release_so_abi_rev = release_patch
 
 # These are set by the distribution script
diff --git a/doc/relnotes/1_11_15.rst b/doc/relnotes/1_11_15.rst
new file mode 100644
index 000000000..4c47785df
--- /dev/null
+++ b/doc/relnotes/1_11_15.rst
@@ -0,0 +1,5 @@
+Version 1.11.15, Not Yet Released
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* A bug in ffi.cpp meant Python could only encrypt. Github issue 53.
+
diff --git a/doc/relnotes/index.rst b/doc/relnotes/index.rst
index ff92f9e4f..896b70479 100644
--- a/doc/relnotes/index.rst
+++ b/doc/relnotes/index.rst
@@ -8,6 +8,7 @@ Series 1.11
 .. toctree::
    :maxdepth: 1
 
+   1_11_15
    1_11_14
    1_11_13
    1_11_12
diff --git a/src/lib/ffi/ffi.cpp b/src/lib/ffi/ffi.cpp
index 6c29a6f7e..c5a862200 100644
--- a/src/lib/ffi/ffi.cpp
+++ b/src/lib/ffi/ffi.cpp
@@ -393,7 +393,8 @@ int botan_cipher_init(botan_cipher_t* cipher, const char* cipher_name, uint32_t
    {
    try
       {
-      Botan::Cipher_Dir dir = (flags & 0) ? Botan::DECRYPTION : Botan::ENCRYPTION;
+      const bool encrypt_p = ((flags & BOTAN_CIPHER_INIT_FLAG_MASK_DIRECTION) == BOTAN_CIPHER_INIT_FLAG_ENCRYPT);
+      const Botan::Cipher_Dir dir = encrypt_p ? Botan::ENCRYPTION : Botan::DECRYPTION;
       std::unique_ptr<Botan::Cipher_Mode> mode(Botan::get_cipher_mode(cipher_name, dir));
       if(!mode)
          return -1;
@@ -469,6 +470,7 @@ int botan_cipher_update(botan_cipher_t cipher_obj,
          {
          mbuf.assign(input, input + input_size);
          *input_consumed = input_size;
+         *output_written = 0;
 
          try
             {
diff --git a/src/lib/ffi/ffi.h b/src/lib/ffi/ffi.h
index 9ba02f02c..b4e99defd 100644
--- a/src/lib/ffi/ffi.h
+++ b/src/lib/ffi/ffi.h
@@ -90,6 +90,10 @@ BOTAN_DLL int botan_mac_destroy(botan_mac_t mac);
 */
 typedef struct botan_cipher_struct* botan_cipher_t;
 
+#define BOTAN_CIPHER_INIT_FLAG_MASK_DIRECTION 1
+#define BOTAN_CIPHER_INIT_FLAG_ENCRYPT 0
+#define BOTAN_CIPHER_INIT_FLAG_DECRYPT 1
+
 BOTAN_DLL int botan_cipher_init(botan_cipher_t* cipher, const char* name, uint32_t flags);
 
 BOTAN_DLL int botan_cipher_valid_nonce_length(botan_cipher_t cipher, size_t nl);
diff --git a/src/python/botan.py b/src/python/botan.py
index 919a426b7..129aeaebb 100755
--- a/src/python/botan.py
+++ b/src/python/botan.py
@@ -517,11 +517,22 @@ def test():
     print "md5", h.final().encode('hex')
 
     gcm = cipher('AES-128/GCM')
-    gcm.set_key('00000000000000000000000000000000'.decode('hex'))
-    gcm.start('000000000000000000000000'.decode('hex'))
-    gcm.update('')
-    gcm.update('')
-    print 'gcm', gcm.finish('00000000000000000000000000000000'.decode('hex')).encode('hex')
+    gcm_dec = cipher('AES-128/GCM', encrypt=False)
+
+    iv = r.get(12)
+    key = r.get(16)
+    pt = r.get(21)
+    gcm.set_key(key)
+    gcm.start(iv)
+    assert len(gcm.update('')) == 0
+    ct = gcm.finish(pt)
+    print "gcm ct", ct.encode('hex')
+
+    gcm_dec.set_key(key)
+    gcm_dec.start(iv)
+    dec = gcm_dec.finish(ct)
+    print "gcm pt", pt.encode('hex'), len(pt)
+    print "gcm de", dec.encode('hex'), len(dec)
 
     rsapriv = private_key('rsa', 1536, r)