Don't allow update_into to mutate immutable objects (pyca#8230)

reaperhulk · Feb 7, 2023 · b35ad89 · b35ad89
1 parent 338a65a
commit b35ad89
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
@@ -156,7 +156,7 @@ def update_into(self, data: bytes, buf: bytes) -> int:
         data_processed = 0
         total_out = 0
         outlen = self._backend._ffi.new("int *")
-        baseoutbuf = self._backend._ffi.from_buffer(buf)
+        baseoutbuf = self._backend._ffi.from_buffer(buf, require_writable=True)
         baseinbuf = self._backend._ffi.from_buffer(data)
 
         while data_processed != total_data_len:

diff --git a/tests/hazmat/primitives/test_ciphers.py b/tests/hazmat/primitives/test_ciphers.py
@@ -318,6 +318,14 @@ def test_update_into_buffer_too_small(self, backend):
         with pytest.raises(ValueError):
             encryptor.update_into(b"testing", buf)
 
+    def test_update_into_immutable(self, backend):
+        key = b"\x00" * 16
+        c = ciphers.Cipher(AES(key), modes.ECB(), backend)
+        encryptor = c.encryptor()
+        buf = b"\x00" * 32
+        with pytest.raises((TypeError, BufferError)):
+            encryptor.update_into(b"testing", buf)
+
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
             AES(b"\x00" * 16), modes.GCM(b"\x00" * 12)