From f2d12107e97172c07a797a99767ece9038c50730 Mon Sep 17 00:00:00 2001
From: Alex Gaynor <alex.gaynor@gmail.com>
Date: Tue, 7 Feb 2023 11:34:18 -0500
Subject: [PATCH] Don't allow update_into to mutate immutable objects (#8230)

---
 src/cryptography/hazmat/backends/openssl/ciphers.py | 2 +-
 tests/hazmat/primitives/test_ciphers.py             | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
index 1e805d235..839613c1e 100644
--- a/src/cryptography/hazmat/backends/openssl/ciphers.py
+++ b/src/cryptography/hazmat/backends/openssl/ciphers.py
@@ -135,7 +135,7 @@ class _CipherContext(object):
         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
index a9219fe99..d5410a656 100644
--- a/tests/hazmat/primitives/test_ciphers.py
+++ b/tests/hazmat/primitives/test_ciphers.py
@@ -310,6 +310,14 @@ class TestCipherUpdateInto(object):
         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)
-- 
2.39.2