Results from concurrent scans against multiple hosts are no longer improperly combined (#190).

src/ssh_audit/ssh2_kexdb.py

@@ -23,6 +23,9 @@
    THE SOFTWARE.
 """
 # pylint: disable=unused-import
+import copy
+import threading
+
 from typing import Dict, List, Set, Sequence, Tuple, Iterable  # noqa: F401
 from typing import Callable, Optional, Union, Any  # noqa: F401
 
@@ -69,8 +72,10 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
     INFO_REMOVED_IN_OPENSSH70 = 'removed in OpenSSH 7.0: https://www.openssh.com/txt/release-7.0'
     INFO_WITHDRAWN_PQ_ALG = 'the sntrup4591761 algorithm was withdrawn, as it may not provide strong post-quantum security'
 
+    # Maintains a dictionary per calling thread that yields its own copy of MASTER_DB.  This prevents results from one thread polluting the results of another thread.
+    DB_PER_THREAD: Dict[int, Dict[str, Dict[str, List[List[Optional[str]]]]]] = {}
 
-    ALGORITHMS: Dict[str, Dict[str, List[List[Optional[str]]]]] = {
+    MASTER_DB: Dict[str, Dict[str, List[List[Optional[str]]]]] = {
         # Format: 'algorithm_name': [['version_first_appeared_in'], [reason_for_failure1, reason_for_failure2, ...], [warning1, warning2, ...], [info1, info2, ...]]
         'kex': {
             'Curve25519SHA256': [[]],
@@ -390,3 +395,24 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
             'umac-96@openssh.com': [[], [], [WARN_ENCRYPT_AND_MAC], [INFO_NEVER_IMPLEMENTED_IN_OPENSSH]],
         }
     }
+
+
+    @staticmethod
+    def get_db() -> Dict[str, Dict[str, List[List[Optional[str]]]]]:
+        '''Returns a copy of the MASTER_DB that is private to the calling thread.  This prevents multiple threads from polluting the results of other threads.'''
+        calling_thread_id = threading.get_ident()
+
+        if calling_thread_id not in SSH2_KexDB.DB_PER_THREAD:
+            SSH2_KexDB.DB_PER_THREAD[calling_thread_id] = copy.deepcopy(SSH2_KexDB.MASTER_DB)
+
+        return SSH2_KexDB.DB_PER_THREAD[calling_thread_id]
+
+
+    @staticmethod
+    def thread_exit() -> None:
+        '''Deletes the calling thread's copy of the MASTER_DB.  This is needed because, in rare circumstances, a terminated thread's ID can be re-used by new threads.'''
+
+        calling_thread_id = threading.get_ident()
+
+        if calling_thread_id in SSH2_KexDB.DB_PER_THREAD:
+            del SSH2_KexDB.DB_PER_THREAD[calling_thread_id]