dev-python/rsa: Backport CVE-2020-13757 fix to 3.4.2

Bug: https://bugs.gentoo.org/727888
Signed-off-by: Michał Górny <mgorny@gentoo.org>

2 files changed, 99 insertions, 0 deletions

diff --git a/dev-python/rsa/files/rsa-3.4.2-cve-2020-13757.patch b/dev-python/rsa/files/rsa-3.4.2-cve-2020-13757.patch
new file mode 100644
index 000000000000..ccee6c0281bb
--- /dev/null
+++ b/dev-python/rsa/files/rsa-3.4.2-cve-2020-13757.patch
@@ -0,0 +1,95 @@
+diff -Nur rsa-3.4.2.orig/rsa/pkcs1.py rsa-3.4.2/rsa/pkcs1.py
+--- rsa-3.4.2.orig/rsa/pkcs1.py	2020-07-05 10:28:57.622204136 +0200
++++ rsa-3.4.2/rsa/pkcs1.py	2020-07-05 10:30:28.103672033 +0200
+@@ -232,6 +232,12 @@
+     decrypted = priv_key.blinded_decrypt(encrypted)
+     cleartext = transform.int2bytes(decrypted, blocksize)
+ 
++    # Detect leading zeroes in the crypto. These are not reflected in the
++    # encrypted value (as leading zeroes do not influence the value of an
++    # integer). This fixes CVE-2020-13757.
++    if len(crypto) > blocksize:
++        raise DecryptionError('Decryption failed')
++
+     # If we can't find the cleartext marker, decryption failed.
+     if cleartext[0:2] != b('\x00\x02'):
+         raise DecryptionError('Decryption failed')
+@@ -310,6 +316,9 @@
+     cleartext = HASH_ASN1[method_name] + message_hash
+     expected = _pad_for_signing(cleartext, keylength)
+ 
++    if len(signature) != keylength:
++        raise VerificationError('Verification failed')
++
+     # Compare with the signed one
+     if expected != clearsig:
+         raise VerificationError('Verification failed')
+diff -Nur rsa-3.4.2.orig/tests/test_pkcs1.py rsa-3.4.2/tests/test_pkcs1.py
+--- rsa-3.4.2.orig/tests/test_pkcs1.py	2020-07-05 10:28:57.621204131 +0200
++++ rsa-3.4.2/tests/test_pkcs1.py	2020-07-05 10:32:26.858286153 +0200
+@@ -17,6 +17,7 @@
+ """Tests string operations."""
+ 
+ import struct
++import sys
+ import unittest
+ 
+ import rsa
+@@ -64,6 +65,35 @@
+ 
+         self.assertNotEqual(encrypted1, encrypted2)
+ 
++class ExtraZeroesTest(unittest.TestCase):
++    def setUp(self):
++        # Key, cyphertext, and plaintext taken from https://github.com/sybrenstuvel/python-rsa/issues/146
++        self.private_key = rsa.PrivateKey.load_pkcs1(
++            "-----BEGIN RSA PRIVATE KEY-----\nMIIEowIBAAKCAQEAs1EKK81M5kTFtZSuUFnhKy8FS2WNXaWVmi/fGHG4CLw98+Yo\n0nkuUarVwSS0O9pFPcpc3kvPKOe9Tv+6DLS3Qru21aATy2PRqjqJ4CYn71OYtSwM\n/ZfSCKvrjXybzgu+sBmobdtYm+sppbdL+GEHXGd8gdQw8DDCZSR6+dPJFAzLZTCd\nB+Ctwe/RXPF+ewVdfaOGjkZIzDoYDw7n+OHnsYCYozkbTOcWHpjVevipR+IBpGPi\n1rvKgFnlcG6d/tj0hWRl/6cS7RqhjoiNEtxqoJzpXs/Kg8xbCxXbCchkf11STA8u\ndiCjQWuWI8rcDwl69XMmHJjIQAqhKvOOQ8rYTQIDAQABAoIBABpQLQ7qbHtp4h1Y\nORAfcFRW7Q74UvtH/iEHH1TF8zyM6wZsYtcn4y0mxYE3Mp+J0xlTJbeVJkwZXYVH\nL3UH29CWHSlR+TWiazTwrCTRVJDhEoqbcTiRW8fb+o/jljVxMcVDrpyYUHNo2c6w\njBxhmKPtp66hhaDpds1Cwi0A8APZ8Z2W6kya/L/hRBzMgCz7Bon1nYBMak5PQEwV\nF0dF7Wy4vIjvCzO6DSqA415DvJDzUAUucgFudbANNXo4HJwNRnBpymYIh8mHdmNJ\n/MQ0YLSqUWvOB57dh7oWQwe3UsJ37ZUorTugvxh3NJ7Tt5ZqbCQBEECb9ND63gxo\n/a3YR/0CgYEA7BJc834xCi/0YmO5suBinWOQAF7IiRPU+3G9TdhWEkSYquupg9e6\nK9lC5k0iP+t6I69NYF7+6mvXDTmv6Z01o6oV50oXaHeAk74O3UqNCbLe9tybZ/+F\ndkYlwuGSNttMQBzjCiVy0+y0+Wm3rRnFIsAtd0RlZ24aN3bFTWJINIsCgYEAwnQq\nvNmJe9SwtnH5c/yCqPhKv1cF/4jdQZSGI6/p3KYNxlQzkHZ/6uvrU5V27ov6YbX8\nvKlKfO91oJFQxUD6lpTdgAStI3GMiJBJIZNpyZ9EWNSvwUj28H34cySpbZz3s4Xd\nhiJBShgy+fKURvBQwtWmQHZJ3EGrcOI7PcwiyYcCgYEAlql5jSUCY0ALtidzQogW\nJ+B87N+RGHsBuJ/0cxQYinwg+ySAAVbSyF1WZujfbO/5+YBN362A/1dn3lbswCnH\nK/bHF9+fZNqvwprPnceQj5oK1n4g6JSZNsy6GNAhosT+uwQ0misgR8SQE4W25dDG\nkdEYsz+BgCsyrCcu8J5C+tUCgYAFVPQbC4f2ikVyKzvgz0qx4WUDTBqRACq48p6e\n+eLatv7nskVbr7QgN+nS9+Uz80ihR0Ev1yCAvnwmM/XYAskcOea87OPmdeWZlQM8\nVXNwINrZ6LMNBLgorfuTBK1UoRo1pPUHCYdqxbEYI2unak18mikd2WB7Fp3h0YI4\nVpGZnwKBgBxkAYnZv+jGI4MyEKdsQgxvROXXYOJZkWzsKuKxVkVpYP2V4nR2YMOJ\nViJQ8FUEnPq35cMDlUk4SnoqrrHIJNOvcJSCqM+bWHAioAsfByLbUPM8sm3CDdIk\nXVJl32HuKYPJOMIWfc7hIfxLRHnCN+coz2M6tgqMDs0E/OfjuqVZ\n-----END RSA PRIVATE KEY-----",
++            format='PEM')
++        cyphertext = "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"
++        plaintext = "54657374"
++
++        if sys.version_info < (3, 0):
++            self.cyphertext = cyphertext.decode("hex")
++            self.plaintext = plaintext.decode('hex')
++        else:
++            self.cyphertext = bytes.fromhex(cyphertext)
++            self.plaintext = bytes.fromhex(plaintext)
++
++    def test_unmodified(self):
++        message = rsa.decrypt(self.cyphertext, self.private_key)
++        self.assertEqual(message, self.plaintext)
++
++    def test_prepend_zeroes(self):
++        cyphertext = b'\00\00' + self.cyphertext
++        with self.assertRaises(rsa.DecryptionError):
++            rsa.decrypt(cyphertext, self.private_key)
++
++    def test_append_zeroes(self):
++        cyphertext = self.cyphertext + b'\00\00'
++        with self.assertRaises(rsa.DecryptionError):
++            rsa.decrypt(cyphertext, self.private_key)
+ 
+ class SignatureTest(unittest.TestCase):
+     def setUp(self):
+@@ -105,3 +135,21 @@
+         signature2 = pkcs1.sign(message, self.priv, 'SHA-1')
+ 
+         self.assertEqual(signature1, signature2)
++
++    def test_prepend_zeroes(self):
++        """Prepending the signature with zeroes should be detected."""
++
++        message = b'je moeder'
++        signature = pkcs1.sign(message, self.priv, 'SHA-256')
++        signature = b'\00\00' + signature
++        with self.assertRaises(rsa.VerificationError):
++            pkcs1.verify(message, signature, self.pub)
++
++    def test_apppend_zeroes(self):
++        """Apppending the signature with zeroes should be detected."""
++
++        message = b'je moeder'
++        signature = pkcs1.sign(message, self.priv, 'SHA-256')
++        signature = signature + b'\00\00'
++        with self.assertRaises(rsa.VerificationError):
++            pkcs1.verify(message, signature, self.pub)
diff --git a/dev-python/rsa/rsa-3.4.2-r1.ebuild b/dev-python/rsa/rsa-3.4.2-r2.ebuild
index bc2b7755ef5e..8b4366f95ce6 100644
--- a/dev-python/rsa/rsa-3.4.2-r1.ebuild
+++ b/dev-python/rsa/rsa-3.4.2-r2.ebuild
@@ -29,6 +29,10 @@ DEPEND="${RDEPEND}
 		)
 	"
 
+PATCHES=(
+	"${FILESDIR}"/${P}-cve-2020-13757.patch
+)
+
 python_test() {
 	nosetests --verbose || die
 }