Turn b"ext-info-[cs]" into private constants

dctikan · Oct 15, 2021 · 58d1cf5 · 58d1cf5
1 parent b38508e
commit 58d1cf5
Showing 1 changed file with 13 additions and 3 deletions.
diff --git a/src/twisted/conch/ssh/transport.py b/src/twisted/conch/ssh/transport.py
@@ -491,6 +491,14 @@ class SSHTransportBase(protocol.Protocol):
     _keyExchangeState = _KEY_EXCHANGE_NONE
     _blockedByKeyExchange = None
 
+    # Added to key exchange algorithms by a client to indicate support for
+    # extension negotiation.
+    _EXT_INFO_C = b"ext-info-c"
+
+    # Added to key exchange algorithms by a server to indicate support for
+    # extension negotiation.
+    _EXT_INFO_S = b"ext-info-s"
+
     _supportsExtensionNegotiation = False
     otherExtensions: Dict[bytes, bytes] = {}
 
@@ -543,7 +551,9 @@ def sendKexInit(self):
         # there's nothing to forbid the server from sending it as well, and
         # doing so makes things easier if it needs to process extensions
         # sent by clients in future.
-        supportedKeyExchanges.append(b"ext-info-c" if self.isClient else b"ext-info-s")
+        supportedKeyExchanges.append(
+            self._EXT_INFO_C if self.isClient else self._EXT_INFO_S
+        )
 
         self.ourKexInitPayload = b"".join(
             [
@@ -906,7 +916,7 @@ def ssh_KEXINIT(self, packet):
                 self.incomingCompressionType,
             )
             # RFC 8308, section 2.2
-            or self.kexAlg in (b"ext-info-c", b"ext-info-s")
+            or self.kexAlg in (self._EXT_INFO_C, self._EXT_INFO_S)
         ):
             self.sendDisconnect(
                 DISCONNECT_KEY_EXCHANGE_FAILED, b"couldn't match all kex parts"
@@ -918,7 +928,7 @@ def ssh_KEXINIT(self, packet):
             )
             return
         self._supportsExtensionNegotiation = (
-            b"ext-info-s" if self.isClient else b"ext-info-c"
+            self._EXT_INFO_S if self.isClient else self._EXT_INFO_C
         ) in kexAlgs
         self._log.debug(
             "kex alg={kexAlg!r} key alg={keyAlg!r}",