Use hash for ControlPath instead of full variables

The generated socket path can be too long, if your FQDN is very long...

Typical error message from ssh client:
unix_listener: path "/tmp/ssh-fqduawon/master-USER@HOST:PORT.qfCZ51OAZgTzVLbg" too long for Unix domain socket

Use a hashed version instead, to keep within the socket file path limit.

This requires OpenSSH_6.7p1, or later.

Change-Id: Ia4bb9ae8aac6c4ee31d5a458f917f3753f40001b
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/255632
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Anders Björklund <anders.bjorklund.2@volvocars.com>

2 files changed, 62 insertions, 1 deletions

diff --git a/git_command.py b/git_command.py
index a2782151..1cb8f1aa 100644
--- a/git_command.py
+++ b/git_command.py
@@ -16,6 +16,7 @@
 
 from __future__ import print_function
 import os
+import re
 import sys
 import subprocess
 import tempfile
@@ -47,6 +48,35 @@ LAST_CWD = None
 _ssh_proxy_path = None
 _ssh_sock_path = None
 _ssh_clients = []
+_ssh_version = None
+
+
+def _run_ssh_version():
+  """run ssh -V to display the version number"""
+  return subprocess.check_output(['ssh', '-V'], stderr=subprocess.STDOUT).decode()
+
+
+def _parse_ssh_version(ver_str=None):
+  """parse a ssh version string into a tuple"""
+  if ver_str is None:
+    ver_str = _run_ssh_version()
+  m = re.match(r'^OpenSSH_([0-9.]+)(p[0-9]+)?\s', ver_str)
+  if m:
+    return tuple(int(x) for x in m.group(1).split('.'))
+  else:
+    return ()
+
+
+def ssh_version():
+  """return ssh version as a tuple"""
+  global _ssh_version
+  if _ssh_version is None:
+    try:
+      _ssh_version = _parse_ssh_version()
+    except subprocess.CalledProcessError:
+      print('fatal: unable to detect ssh version', file=sys.stderr)
+      sys.exit(1)
+  return _ssh_version
 
 
 def ssh_sock(create=True):
@@ -57,9 +87,13 @@ def ssh_sock(create=True):
     tmp_dir = '/tmp'
     if not os.path.exists(tmp_dir):
       tmp_dir = tempfile.gettempdir()
+    if ssh_version() < (6, 7):
+      tokens = '%r@%h:%p'
+    else:
+      tokens = '%C'  # hash of %l%h%p%r
     _ssh_sock_path = os.path.join(
         tempfile.mkdtemp('', 'ssh-', tmp_dir),
-        'master-%r@%h:%p')
+        'master-' + tokens)
   return _ssh_sock_path
 
 
diff --git a/tests/test_git_command.py b/tests/test_git_command.py
index c2d3f1df..2c22b250 100644
--- a/tests/test_git_command.py
+++ b/tests/test_git_command.py
@@ -30,6 +30,33 @@ import git_command
 import wrapper
 
 
+class SSHUnitTest(unittest.TestCase):
+  """Tests the ssh functions."""
+
+  def test_ssh_version(self):
+    """Check ssh_version() handling."""
+    ver = git_command._parse_ssh_version('Unknown\n')
+    self.assertEqual(ver, ())
+    ver = git_command._parse_ssh_version('OpenSSH_1.0\n')
+    self.assertEqual(ver, (1, 0))
+    ver = git_command._parse_ssh_version('OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.13, OpenSSL 1.0.1f 6 Jan 2014\n')
+    self.assertEqual(ver, (6, 6, 1))
+    ver = git_command._parse_ssh_version('OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n  7 Dec 2017\n')
+    self.assertEqual(ver, (7, 6))
+
+  def test_ssh_sock(self):
+    """Check ssh_sock() function."""
+    with mock.patch('tempfile.mkdtemp', return_value='/tmp/foo'):
+      # old ssh version uses port
+      with mock.patch('git_command.ssh_version', return_value=(6, 6)):
+        self.assertTrue(git_command.ssh_sock().endswith('%p'))
+      git_command._ssh_sock_path = None
+      # new ssh version uses hash
+      with mock.patch('git_command.ssh_version', return_value=(6, 7)):
+        self.assertTrue(git_command.ssh_sock().endswith('%C'))
+      git_command._ssh_sock_path = None
+
+
 class GitCallUnitTest(unittest.TestCase):
   """Tests the _GitCall class (via git_command.git)."""