Merge branch '3.2' into 3.3

4 files changed, 15 insertions, 4 deletions

diff --git a/paramiko/transport.py b/paramiko/transport.py
index 8785d6bb..14a26333 100644
--- a/paramiko/transport.py
+++ b/paramiko/transport.py
@@ -2450,8 +2450,9 @@ class Transport(threading.Thread, ClosingContextManager):
 
         # Strip out ext-info "kex algo"
         self._remote_ext_info = None
-        if kex_algo_list[-1].startswith("ext-info-"):
-            self._remote_ext_info = kex_algo_list.pop()
+        for i, algo in enumerate(kex_algo_list):
+            if algo.startswith("ext-info-"):
+                self._remote_ext_info = kex_algo_list.pop(i)
 
         # as a server, we pick the first item in the client's list that we
         # support.
diff --git a/sites/www/changelog.rst b/sites/www/changelog.rst
index 0bd08ef6..45df830c 100644
--- a/sites/www/changelog.rst
+++ b/sites/www/changelog.rst
@@ -2,6 +2,9 @@
 Changelog
 =========
 
+- :bug:`-` Tweak ``ext-info-(c|s)`` detection during KEXINIT protocol phase;
+  the original implementation made assumptions based on an OpenSSH
+  implementation detail.
 - :release:`3.3.1 <2023-07-28>`
 - :bug:`-` Cleaned up some very old root level files, mostly just to exercise
   some of our doc build and release machinery. This changelog entry
diff --git a/tests/_util.py b/tests/_util.py
index ec7585df..acc06852 100644
--- a/tests/_util.py
+++ b/tests/_util.py
@@ -352,6 +352,9 @@ def server(
     """
     SSH server contextmanager for testing.
 
+    Yields a tuple of ``(tc, ts)`` (client- and server-side `Transport`
+    objects), or ``(tc, ts, err)`` when ``catch_error==True``.
+
     :param hostkey:
         Host key to use for the server; if None, loads
         ``rsa.key``.
diff --git a/tests/test_transport.py b/tests/test_transport.py
index b2efd637..421c078b 100644
--- a/tests/test_transport.py
+++ b/tests/test_transport.py
@@ -1213,10 +1213,14 @@ class TestSHA2SignatureKeyExchange(unittest.TestCase):
 
 
 class TestExtInfo(unittest.TestCase):
-    def test_ext_info_handshake(self):
+    def test_ext_info_handshake_exposed_in_client_kexinit(self):
         with server() as (tc, _):
+            # NOTE: this is latest KEXINIT /sent by us/ (Transport retains it)
             kex = tc._get_latest_kex_init()
-            assert kex["kex_algo_list"][-1] == "ext-info-c"
+            # flag in KexAlgorithms list
+            assert "ext-info-c" in kex["kex_algo_list"]
+            # data stored on Transport after hearing back from a compatible
+            # server (such as ourselves in server mode)
             assert tc.server_extensions == {
                 "server-sig-algs": b"ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ssh-dss"  # noqa
             }