root / ncclient / transport / ssh.py @ 4f650d54
History | View | Annotate | Download (12.1 kB)
1 |
# Copyright 2009 Shikhar Bhushan
|
---|---|
2 |
#
|
3 |
# Licensed under the Apache License, Version 2.0 (the "License");
|
4 |
# you may not use this file except in compliance with the License.
|
5 |
# You may obtain a copy of the License at
|
6 |
#
|
7 |
# http://www.apache.org/licenses/LICENSE-2.0
|
8 |
#
|
9 |
# Unless required by applicable law or agreed to in writing, software
|
10 |
# distributed under the License is distributed on an "AS IS" BASIS,
|
11 |
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
12 |
# See the License for the specific language governing permissions and
|
13 |
# limitations under the License.
|
14 |
|
15 |
import os |
16 |
import socket |
17 |
from binascii import hexlify |
18 |
from cStringIO import StringIO |
19 |
from select import select |
20 |
|
21 |
import paramiko |
22 |
|
23 |
from errors import AuthenticationError, SessionCloseError, SSHError, SSHUnknownHostError |
24 |
from session import Session |
25 |
|
26 |
import logging |
27 |
logger = logging.getLogger('ncclient.transport.ssh')
|
28 |
|
29 |
BUF_SIZE = 4096
|
30 |
MSG_DELIM = ']]>]]>'
|
31 |
TICK = 0.1
|
32 |
|
33 |
def default_unknown_host_cb(host, key): |
34 |
"""An `unknown host callback` returns :const:`True` if it finds the key
|
35 |
acceptable, and :const:`False` if not.
|
36 |
|
37 |
:arg host: the hostname/address which needs to be verified
|
38 |
|
39 |
:arg key: a hex string representing the host key fingerprint
|
40 |
|
41 |
:returns: this default callback always returns :const:`False`
|
42 |
"""
|
43 |
return False |
44 |
|
45 |
|
46 |
class SSHSession(Session): |
47 |
|
48 |
"Implements a :rfc:`4742` NETCONF session over SSH."
|
49 |
|
50 |
def __init__(self, capabilities): |
51 |
Session.__init__(self, capabilities)
|
52 |
self._host_keys = paramiko.HostKeys()
|
53 |
self._system_host_keys = paramiko.HostKeys()
|
54 |
self._transport = None |
55 |
self._connected = False |
56 |
self._channel = None |
57 |
self._expecting_close = False |
58 |
self._buffer = StringIO() # for incoming data |
59 |
# parsing-related, see _parse()
|
60 |
self._parsing_state = 0 |
61 |
self._parsing_pos = 0 |
62 |
|
63 |
def _parse(self): |
64 |
'''Messages ae delimited by MSG_DELIM. The buffer could have grown by a
|
65 |
maximum of BUF_SIZE bytes everytime this method is called. Retains state
|
66 |
across method calls and if a byte has been read it will not be
|
67 |
considered again. '''
|
68 |
delim = MSG_DELIM |
69 |
n = len(delim) - 1 |
70 |
expect = self._parsing_state
|
71 |
buf = self._buffer
|
72 |
buf.seek(self._parsing_pos)
|
73 |
while True: |
74 |
x = buf.read(1)
|
75 |
if not x: # done reading |
76 |
break
|
77 |
elif x == delim[expect]: # what we expected |
78 |
expect += 1 # expect the next delim char |
79 |
else:
|
80 |
continue
|
81 |
# loop till last delim char expected, break if other char encountered
|
82 |
for i in range(expect, n): |
83 |
x = buf.read(1)
|
84 |
if not x: # done reading |
85 |
break
|
86 |
if x == delim[expect]: # what we expected |
87 |
expect += 1 # expect the next delim char |
88 |
else:
|
89 |
expect = 0 # reset |
90 |
break
|
91 |
else: # if we didn't break out of the loop, full delim was parsed |
92 |
msg_till = buf.tell() - n |
93 |
buf.seek(0)
|
94 |
logger.debug('parsed new message')
|
95 |
self._dispatch_message(buf.read(msg_till).strip())
|
96 |
buf.seek(n+1, os.SEEK_CUR)
|
97 |
rest = buf.read() |
98 |
buf = StringIO() |
99 |
buf.write(rest) |
100 |
buf.seek(0)
|
101 |
expect = 0
|
102 |
self._buffer = buf
|
103 |
self._parsing_state = expect
|
104 |
self._parsing_pos = self._buffer.tell() |
105 |
|
106 |
def load_system_host_keys(self, filename=None): |
107 |
if filename is None: |
108 |
filename = os.path.expanduser('~/.ssh/known_hosts')
|
109 |
try:
|
110 |
self._system_host_keys.load(filename)
|
111 |
except IOError: |
112 |
# for windows
|
113 |
filename = os.path.expanduser('~/ssh/known_hosts')
|
114 |
try:
|
115 |
self._system_host_keys.load(filename)
|
116 |
except IOError: |
117 |
pass
|
118 |
return
|
119 |
self._system_host_keys.load(filename)
|
120 |
|
121 |
def load_host_keys(self, filename): |
122 |
self._host_keys.load(filename)
|
123 |
|
124 |
def add_host_key(self, key): |
125 |
self._host_keys.add(key)
|
126 |
|
127 |
def save_host_keys(self, filename): |
128 |
f = open(filename, 'w') |
129 |
for host, keys in self._host_keys.iteritems(): |
130 |
for keytype, key in keys.iteritems(): |
131 |
f.write('%s %s %s\n' % (host, keytype, key.get_base64()))
|
132 |
f.close() |
133 |
|
134 |
def close(self): |
135 |
self._expecting_close = True |
136 |
if self._transport.is_active(): |
137 |
self._transport.close()
|
138 |
self._connected = False |
139 |
|
140 |
def connect(self, host, port=830, timeout=None, |
141 |
unknown_host_cb=default_unknown_host_cb, |
142 |
username=None, password=None, |
143 |
key_filename=None, allow_agent=True, look_for_keys=True): |
144 |
"""Connect via SSH and initialize the NETCONF session. First attempts
|
145 |
the publickey authentication method and then password authentication.
|
146 |
|
147 |
To disable publickey authentication, call with *allow_agent* and
|
148 |
*look_for_keys* as :const:`False`
|
149 |
|
150 |
:arg host: the hostname or IP address to connect to
|
151 |
|
152 |
:arg port: by default 830, but some devices use the default SSH port of 22 so this may need to be specified
|
153 |
|
154 |
:arg timeout: an optional timeout for the TCP handshake
|
155 |
|
156 |
:arg unknown_host_cb: called when a host key is not known. See :func:`unknown_host_cb` for details on signature
|
157 |
|
158 |
:arg username: the username to use for SSH authentication
|
159 |
|
160 |
:arg password: the password used if using password authentication, or the passphrase to use in order to unlock keys that require it
|
161 |
|
162 |
:arg key_filename: a filename where a the private key to be used can be found
|
163 |
|
164 |
:arg allow_agent: enables querying SSH agent (if found) for keys
|
165 |
|
166 |
:arg look_for_keys: enables looking in the usual locations for ssh keys (e.g. :file:`~/.ssh/id_*`)
|
167 |
"""
|
168 |
|
169 |
assert(username is not None) |
170 |
|
171 |
for (family, socktype, proto, canonname, sockaddr) in \ |
172 |
socket.getaddrinfo(host, port): |
173 |
if socktype == socket.SOCK_STREAM:
|
174 |
af = family |
175 |
addr = sockaddr |
176 |
break
|
177 |
else:
|
178 |
raise SSHError('No suitable address family for %s' % host) |
179 |
sock = socket.socket(af, socket.SOCK_STREAM) |
180 |
sock.settimeout(timeout) |
181 |
sock.connect(addr) |
182 |
t = self._transport = paramiko.Transport(sock)
|
183 |
t.set_log_channel(logger.name) |
184 |
|
185 |
try:
|
186 |
t.start_client() |
187 |
except paramiko.SSHException:
|
188 |
raise SSHError('Negotiation failed') |
189 |
|
190 |
# host key verification
|
191 |
server_key = t.get_remote_server_key() |
192 |
known_host = self._host_keys.check(host, server_key) or \ |
193 |
self._system_host_keys.check(host, server_key)
|
194 |
|
195 |
fp = hexlify(server_key.get_fingerprint()) |
196 |
if not known_host and not unknown_host_cb(host, fp): |
197 |
raise SSHUnknownHostError(host, fp)
|
198 |
|
199 |
if key_filename is None: |
200 |
key_filenames = [] |
201 |
elif isinstance(key_filename, basestring): |
202 |
key_filenames = [ key_filename ] |
203 |
else:
|
204 |
key_filenames = key_filename |
205 |
|
206 |
self._auth(username, password, key_filenames, allow_agent, look_for_keys)
|
207 |
|
208 |
self._connected = True # there was no error authenticating |
209 |
|
210 |
c = self._channel = self._transport.open_session() |
211 |
c.set_name('netconf')
|
212 |
c.invoke_subsystem('netconf')
|
213 |
|
214 |
self._post_connect()
|
215 |
|
216 |
# on the lines of paramiko.SSHClient._auth()
|
217 |
def _auth(self, username, password, key_filenames, allow_agent, |
218 |
look_for_keys): |
219 |
saved_exception = None
|
220 |
|
221 |
for key_filename in key_filenames: |
222 |
for cls in (paramiko.RSAKey, paramiko.DSSKey): |
223 |
try:
|
224 |
key = cls.from_private_key_file(key_filename, password) |
225 |
logger.debug('Trying key %s from %s' %
|
226 |
(hexlify(key.get_fingerprint()), key_filename)) |
227 |
self._transport.auth_publickey(username, key)
|
228 |
return
|
229 |
except Exception as e: |
230 |
saved_exception = e |
231 |
logger.debug(e) |
232 |
|
233 |
if allow_agent:
|
234 |
for key in paramiko.Agent().get_keys(): |
235 |
try:
|
236 |
logger.debug('Trying SSH agent key %s' %
|
237 |
hexlify(key.get_fingerprint())) |
238 |
self._transport.auth_publickey(username, key)
|
239 |
return
|
240 |
except Exception as e: |
241 |
saved_exception = e |
242 |
logger.debug(e) |
243 |
|
244 |
keyfiles = [] |
245 |
if look_for_keys:
|
246 |
rsa_key = os.path.expanduser('~/.ssh/id_rsa')
|
247 |
dsa_key = os.path.expanduser('~/.ssh/id_dsa')
|
248 |
if os.path.isfile(rsa_key):
|
249 |
keyfiles.append((paramiko.RSAKey, rsa_key)) |
250 |
if os.path.isfile(dsa_key):
|
251 |
keyfiles.append((paramiko.DSSKey, dsa_key)) |
252 |
# look in ~/ssh/ for windows users:
|
253 |
rsa_key = os.path.expanduser('~/ssh/id_rsa')
|
254 |
dsa_key = os.path.expanduser('~/ssh/id_dsa')
|
255 |
if os.path.isfile(rsa_key):
|
256 |
keyfiles.append((paramiko.RSAKey, rsa_key)) |
257 |
if os.path.isfile(dsa_key):
|
258 |
keyfiles.append((paramiko.DSSKey, dsa_key)) |
259 |
|
260 |
for cls, filename in keyfiles: |
261 |
try:
|
262 |
key = cls.from_private_key_file(filename, password) |
263 |
logger.debug('Trying discovered key %s in %s' %
|
264 |
(hexlify(key.get_fingerprint()), filename)) |
265 |
self._transport.auth_publickey(username, key)
|
266 |
return
|
267 |
except Exception as e: |
268 |
saved_exception = e |
269 |
logger.debug(e) |
270 |
|
271 |
if password is not None: |
272 |
try:
|
273 |
self._transport.auth_password(username, password)
|
274 |
return
|
275 |
except Exception as e: |
276 |
saved_exception = e |
277 |
logger.debug(e) |
278 |
|
279 |
if saved_exception is not None: |
280 |
# need pep-3134 to do this right
|
281 |
raise SSHAuthenticationError(repr(saved_exception)) |
282 |
|
283 |
raise SSHAuthenticationError('No authentication methods available') |
284 |
|
285 |
def run(self): |
286 |
chan = self._channel
|
287 |
chan.setblocking(0)
|
288 |
q = self._q
|
289 |
try:
|
290 |
while True: |
291 |
# select on a paramiko ssh channel object does not ever return
|
292 |
# it in the writable list, so it channel's don't exactly emulate
|
293 |
# the socket api
|
294 |
r, w, e = select([chan], [], [], TICK) |
295 |
# will wakeup evey TICK seconds to check if something
|
296 |
# to send, more if something to read (due to select returning
|
297 |
# chan in readable list)
|
298 |
if r:
|
299 |
data = chan.recv(BUF_SIZE) |
300 |
if data:
|
301 |
self._buffer.write(data)
|
302 |
self._parse()
|
303 |
else:
|
304 |
raise SessionCloseError(self._buffer.getvalue()) |
305 |
if not q.empty() and chan.send_ready(): |
306 |
logger.debug('sending message')
|
307 |
data = q.get() + MSG_DELIM |
308 |
while data:
|
309 |
n = chan.send(data) |
310 |
if n <= 0: |
311 |
raise SessionCloseError(self._buffer.getvalue(), data) |
312 |
data = data[n:] |
313 |
except Exception as e: |
314 |
logger.debug('broke out of main loop')
|
315 |
self.close()
|
316 |
if not (isinstance(e, SessionCloseError) and self._expecting_close): |
317 |
self._dispatch_error(e)
|
318 |
|
319 |
@property
|
320 |
def transport(self): |
321 |
"""The underlying `paramiko.Transport
|
322 |
<http://www.lag.net/paramiko/docs/paramiko.Transport-class.html>`_
|
323 |
object. This makes it possible to call methods like set_keepalive on it.
|
324 |
"""
|
325 |
return self._transport |
326 |
|
327 |
@property
|
328 |
def can_pipeline(self): |
329 |
if 'Cisco' in self._transport.remote_version: |
330 |
return False |
331 |
# elif ..
|
332 |
return True |