Use a -short- custom hash for controlpersist path by default (#20843)

* A method to validate and alter the ssh control path automatically.
* First tries %C to use the shortened hash
* On further failure, it removes section by section from the original path
* Fix hostname
* Implement bcoca's suggested changes
* Remove unused option
* Remove unused class var
* Use to_string to avoid unicode error
* Switch from to_text to to_bytes
* Update the example config for the new controlpath feature

examples/ansible.cfg

@@ -310,16 +310,14 @@
 # control_path_dir = /tmp/.ansible/cp
 #control_path_dir = ~/.ansible/cp
 
-# The path to use for the ControlPath sockets. This defaults to
-# "%(directory)s/ansible-ssh-%%h-%%p-%%r", however on some systems with
-# very long hostnames or very long path names (caused by long user names or
-# deeply nested home directories) this can exceed the character limit on
-# file socket names (108 characters for most platforms). In that case, you
-# may wish to shorten the string below.
+# The path to use for the ControlPath sockets. This defaults to a hashed string of the hostname, 
+# port and username (empty string in the config). The hash mitigates a common problem users 
+# found with long hostames and the conventional %(directory)s/ansible-ssh-%%h-%%p-%%r format. 
+# In those cases, a "too long for Unix domain socket" ssh error would occur.
 #
 # Example:
 # control_path = %(directory)s/%%h-%%r
-#control_path = %(directory)s/ansible-ssh-%%h-%%p-%%r
+#control_path =
 
 # Enabling pipelining reduces the number of SSH operations required to
 # execute a module on the remote server. This can result in a significant

lib/ansible/constants.py

@@ -331,7 +331,7 @@ def load_config_file():
 # to .format() in the future.  be sure to read this:
 # http://lucumr.pocoo.org/2016/12/29/careful-with-str-format/ and understand
 # that it may be a security risk to do so.
-ANSIBLE_SSH_CONTROL_PATH       = get_config(p, 'ssh_connection', 'control_path', 'ANSIBLE_SSH_CONTROL_PATH', u"%(directory)s/ansible-ssh-%%h-%%p-%%r")
+ANSIBLE_SSH_CONTROL_PATH       = get_config(p, 'ssh_connection', 'control_path', 'ANSIBLE_SSH_CONTROL_PATH', None)
 ANSIBLE_SSH_CONTROL_PATH_DIR   = get_config(p, 'ssh_connection', 'control_path_dir', 'ANSIBLE_SSH_CONTROL_PATH_DIR', u'~/.ansible/cp')
 ANSIBLE_SSH_PIPELINING         = get_config(p, 'ssh_connection', 'pipelining', 'ANSIBLE_SSH_PIPELINING', False, value_type='boolean')
 ANSIBLE_SSH_RETRIES            = get_config(p, 'ssh_connection', 'retries', 'ANSIBLE_SSH_RETRIES', 0, value_type='integer')

lib/ansible/plugins/connection/ssh.py

@@ -21,6 +21,7 @@
 
 import errno
 import fcntl
+import hashlib
 import os
 import pty
 import select
@@ -59,6 +60,10 @@ def __init__(self, *args, **kwargs):
         super(Connection, self).__init__(*args, **kwargs)
 
         self.host = self._play_context.remote_addr
+        self.port = self._play_context.port
+        self.user = self._play_context.remote_user
+        self.control_path = C.ANSIBLE_SSH_CONTROL_PATH
+        self.control_path_dir = C.ANSIBLE_SSH_CONTROL_PATH_DIR
 
     # The connection is created by running ssh/scp/sftp from the exec_command,
     # put_file, and fetch_file methods, so we don't need to do any connection
@@ -67,6 +72,16 @@ def __init__(self, *args, **kwargs):
     def _connect(self):
         return self
 
+    @staticmethod
+    def _create_control_path(host, port, user):
+        '''Make a hash for the controlpath based on con attributes'''
+        pstring = '%s-%s-%s' % (host, port, user)
+        m = hashlib.sha1()
+        m.update(to_bytes(pstring))
+        digest = m.hexdigest()
+        cpath = '%(directory)s/' + digest[:10]
+        return cpath
+
     @staticmethod
     def _sshpass_available():
         global SSHPASS_AVAILABLE
@@ -228,15 +243,21 @@ def _build_command(self, binary, *other_args):
             self._persistent = True
 
             if not controlpath:
-                cpdir = unfrackpath(C.ANSIBLE_SSH_CONTROL_PATH_DIR)
+                cpdir = unfrackpath(self.control_path_dir)
                 b_cpdir = to_bytes(cpdir, errors='surrogate_or_strict')
 
                 # The directory must exist and be writable.
                 makedirs_safe(b_cpdir, 0o700)
                 if not os.access(b_cpdir, os.W_OK):
                     raise AnsibleError("Cannot write to ControlPath %s" % to_native(cpdir))
 
-                b_args = (b"-o", b"ControlPath=" + to_bytes(C.ANSIBLE_SSH_CONTROL_PATH % dict(directory=cpdir), errors='surrogate_or_strict'))
+                if not self.control_path:
+                    self.control_path = self._create_control_path(
+                        self.host,
+                        self.port,
+                        self.user
+                    )
+                b_args = (b"-o", b"ControlPath=" + to_bytes(self.control_path % dict(directory=cpdir), errors='surrogate_or_strict'))
                 self._add_args(b_command, b_args, u"found only ControlPersist; added ControlPath")
 
         # Finally, we add any caller-supplied extras.