bpo-38270: Check for hash digest algorithms and avoid MD5 (GH-16382)

Make it easier to run and test Python on systems with restrict crypto policies:

* add requires_hashdigest to test.support to check if a hash digest algorithm is available and working
* avoid MD5 in test_hmac
* replace MD5 with SHA256 in test_tarfile
* mark network tests that require MD5 for MD5-based digest auth or CRAM-MD5


https://bugs.python.org/issue38270

1 files changed, 10 insertions, 1 deletions

diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index f1332e9..d0c9862 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -4,6 +4,7 @@ import email.mime.text
 from email.message import EmailMessage
 from email.base64mime import body_encode as encode_base64
 import email.utils
+import hashlib
 import hmac
 import socket
 import smtpd
@@ -21,6 +22,7 @@ import unittest
 from test import support, mock_socket
 from test.support import HOST
 from test.support import threading_setup, threading_cleanup, join_thread
+from test.support import requires_hashdigest
 from unittest.mock import Mock
 
 
@@ -1009,6 +1011,7 @@ class SMTPSimTests(unittest.TestCase):
         self.assertEqual(resp, (235, b'Authentication Succeeded'))
         smtp.close()
 
+    @requires_hashdigest('md5')
     def testAUTH_CRAM_MD5(self):
         self.serv.add_feature("AUTH CRAM-MD5")
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=15)
@@ -1025,7 +1028,13 @@ class SMTPSimTests(unittest.TestCase):
         smtp.close()
 
     def test_auth_function(self):
-        supported = {'CRAM-MD5', 'PLAIN', 'LOGIN'}
+        supported = {'PLAIN', 'LOGIN'}
+        try:
+            hashlib.md5()
+        except ValueError:
+            pass
+        else:
+            supported.add('CRAM-MD5')
         for mechanism in supported:
             self.serv.add_feature("AUTH {}".format(mechanism))
         for mechanism in supported: