[Buildroot] [PATCH 1/1] package/python-m2crypto: fix CVE-2020-25657

* [Buildroot] [PATCH 1/1] package/python-m2crypto: fix CVE-2020-25657
@ 2023-02-26 13:27 Fabrice Fontaine
  2023-02-27 14:43 ` Peter Korsgaard
  2023-03-14  9:52 ` Peter Korsgaard
  0 siblings, 2 replies; 3+ messages in thread
From: Fabrice Fontaine @ 2023-02-26 13:27 UTC (permalink / raw)
  To: buildroot; +Cc: Gustavo Heinz, Fabrice Fontaine, Asaf Kahlon

A flaw was found in all released versions of m2crypto, where they are
vulnerable to Bleichenbacher timing attacks in the RSA decryption API
via the timed processing of valid PKCS#1 v1.5 Ciphertext. The highest
threat from this vulnerability is to confidentiality.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
 ...he-RSA-decryption-API-CVE-2020-25657.patch | 174 ++++++++++++++++++
 package/python-m2crypto/python-m2crypto.mk    |   3 +
 2 files changed, 177 insertions(+)
 create mode 100644 package/python-m2crypto/0001-Mitigate-the-Bleichenbacher-timing-attacks-in-the-RSA-decryption-API-CVE-2020-25657.patch

diff --git a/package/python-m2crypto/0001-Mitigate-the-Bleichenbacher-timing-attacks-in-the-RSA-decryption-API-CVE-2020-25657.patch b/package/python-m2crypto/0001-Mitigate-the-Bleichenbacher-timing-attacks-in-the-RSA-decryption-API-CVE-2020-25657.patch
new file mode 100644
index 0000000000..68200b7d9b
--- /dev/null
+++ b/package/python-m2crypto/0001-Mitigate-the-Bleichenbacher-timing-attacks-in-the-RSA-decryption-API-CVE-2020-25657.patch
@@ -0,0 +1,174 @@
+From 84c53958def0f510e92119fca14d74f94215827a Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Mat=C4=9Bj=20Cepl?= <mcepl@cepl.eu>
+Date: Tue, 28 Jun 2022 21:17:01 +0200
+Subject: [PATCH] Mitigate the Bleichenbacher timing attacks in the RSA
+ decryption API (CVE-2020-25657)
+
+Fixes #282
+
+[Retrieved from:
+https://gitlab.com/m2crypto/m2crypto/-/commit/84c53958def0f510e92119fca14d74f94215827a]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ src/SWIG/_m2crypto_wrap.c | 20 ++++++++++++--------
+ src/SWIG/_rsa.i           | 20 ++++++++++++--------
+ tests/test_rsa.py         | 15 +++++++--------
+ 3 files changed, 31 insertions(+), 24 deletions(-)
+
+diff --git a/src/SWIG/_m2crypto_wrap.c b/src/SWIG/_m2crypto_wrap.c
+index aba9eb6d..a9f30da9 100644
+--- a/src/SWIG/_m2crypto_wrap.c
++++ b/src/SWIG/_m2crypto_wrap.c
+@@ -7040,9 +7040,10 @@ PyObject *rsa_private_encrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_private_encrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -7070,9 +7071,10 @@ PyObject *rsa_public_decrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_public_decrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -7097,9 +7099,10 @@ PyObject *rsa_public_encrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_public_encrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -7124,9 +7127,10 @@ PyObject *rsa_private_decrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_private_decrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+ 
+diff --git a/src/SWIG/_rsa.i b/src/SWIG/_rsa.i
+index bc714e01..1377b8be 100644
+--- a/src/SWIG/_rsa.i
++++ b/src/SWIG/_rsa.i
+@@ -239,9 +239,10 @@ PyObject *rsa_private_encrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_private_encrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -269,9 +270,10 @@ PyObject *rsa_public_decrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_public_decrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -296,9 +298,10 @@ PyObject *rsa_public_encrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_public_encrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+ 
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+@@ -323,9 +326,10 @@ PyObject *rsa_private_decrypt(RSA *rsa, PyObject *from, int padding) {
+     tlen = RSA_private_decrypt(flen, (unsigned char *)fbuf,
+         (unsigned char *)tbuf, rsa, padding);
+     if (tlen == -1) {
+-        m2_PyErr_Msg(_rsa_err);
++        ERR_clear_error();
++        PyErr_Clear();
+         PyMem_Free(tbuf);
+-        return NULL;
++        Py_RETURN_NONE;
+     }
+     ret = PyBytes_FromStringAndSize((const char *)tbuf, tlen);
+ 
+diff --git a/tests/test_rsa.py b/tests/test_rsa.py
+index 7bb3af75..5e75d681 100644
+--- a/tests/test_rsa.py
++++ b/tests/test_rsa.py
+@@ -109,8 +109,9 @@ class RSATestCase(unittest.TestCase):
+         # The other paddings.
+         for padding in self.s_padding_nok:
+             p = getattr(RSA, padding)
+-            with self.assertRaises(RSA.RSAError):
+-                priv.private_encrypt(self.data, p)
++            # Exception disabled as a part of mitigation against CVE-2020-25657
++            # with self.assertRaises(RSA.RSAError):
++            priv.private_encrypt(self.data, p)
+         # Type-check the data to be encrypted.
+         with self.assertRaises(TypeError):
+             priv.private_encrypt(self.gen_callback, RSA.pkcs1_padding)
+@@ -127,10 +128,12 @@ class RSATestCase(unittest.TestCase):
+             self.assertEqual(ptxt, self.data)
+ 
+         # no_padding
+-        with six.assertRaisesRegex(self, RSA.RSAError, 'data too small'):
+-            priv.public_encrypt(self.data, RSA.no_padding)
++        # Exception disabled as a part of mitigation against CVE-2020-25657
++        # with six.assertRaisesRegex(self, RSA.RSAError, 'data too small'):
++        priv.public_encrypt(self.data, RSA.no_padding)
+ 
+         # Type-check the data to be encrypted.
++        # Exception disabled as a part of mitigation against CVE-2020-25657
+         with self.assertRaises(TypeError):
+             priv.public_encrypt(self.gen_callback, RSA.pkcs1_padding)
+ 
+@@ -146,10 +149,6 @@ class RSATestCase(unittest.TestCase):
+                          b'\000\000\000\003\001\000\001')  # aka 65537 aka 0xf4
+         with self.assertRaises(RSA.RSAError):
+             setattr(rsa, 'e', '\000\000\000\003\001\000\001')
+-        with self.assertRaises(RSA.RSAError):
+-            rsa.private_encrypt(1)
+-        with self.assertRaises(RSA.RSAError):
+-            rsa.private_decrypt(1)
+         assert rsa.check_key()
+ 
+     def test_loadpub_bad(self):
+-- 
+GitLab
+
diff --git a/package/python-m2crypto/python-m2crypto.mk b/package/python-m2crypto/python-m2crypto.mk
index 02ad76d3f4..3c28fa3b0d 100644
--- a/package/python-m2crypto/python-m2crypto.mk
+++ b/package/python-m2crypto/python-m2crypto.mk
@@ -15,4 +15,7 @@ PYTHON_M2CRYPTO_CPE_ID_PRODUCT = m2crypto
 PYTHON_M2CRYPTO_DEPENDENCIES = openssl host-swig
 PYTHON_M2CRYPTO_BUILD_OPTS = --openssl=$(STAGING_DIR)/usr
 
+# 0001-Mitigate-the-Bleichenbacher-timing-attacks-in-the-RSA-decryption-API-CVE-2020-25657.patch
+PYTHON_M2CRYPTO_IGNORE_CVES += CVE-2020-25657
+
 $(eval $(python-package))
-- 
2.39.1

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