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https://github.com/vale981/rmview
synced 2025-03-05 09:11:39 -05:00
Proper Known Hosts handling
- Dialog offers to Add/Update host keys - `host_key_policy` setting
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Emanuele
parent
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commit
057e227438
3 changed files with 130 additions and 47 deletions
41
README.md
41
README.md
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@ -105,15 +105,15 @@ All the settings are optional.
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Connection parameters are provided as a dictionary with the following keys (all optional):
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| Parameter | Values | Comments |
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| ------------------------ | -------------------------------------- | ------------------------------------- |
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| `address` | IP of remarkable | tool prompts for it if missing |
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| `auth_method` | Either `"password"` or `"key"` | defaults to password if key not given |
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| `username` | Username for ssh access on reMarkable | default: `"root"` |
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| `password` | Password provided by reMarkable | not needed if key provided |
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| `key` | Local path to key for ssh | not needed if password provided |
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| `timeout` | Connection timeout in seconds | default: 1 |
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| `insecure_auto_add_host` | Ignores the check on the fingerprint | default: `false` |
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| Parameter | Values | Comments |
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| ----------------- | ------------------------------------------------------- | ------------------------------------- |
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| `address` | IP of remarkable | tool prompts for it if missing |
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| `auth_method` | Either `"password"` or `"key"` | defaults to password if key not given |
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| `username` | Username for ssh access on reMarkable | default: `"root"` |
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| `password` | Password provided by reMarkable | not needed if key provided |
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| `key` | Local path to key for ssh | not needed if password provided |
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| `timeout` | Connection timeout in seconds | default: 1 |
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| `host_key_policy` | `"ask"`, `"ignore_new"`, `"ignore_all"`, `"auto_add"` | default: `"ask"` (description below) |
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The `address` parameter can be either:
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- a single string, in which case the address is used for connection
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@ -124,17 +124,24 @@ To establish a connection with the tablet, you can use any of the following:
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- Specify `"auth_method": "key"` to use a SSH key. In case an SSH key hasn't already been associated with the tablet, you can provide its path with the `key` setting.
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- Provide a `password` in settings
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If `auth_method` is `password` but no password is specified, then the tool will ask for the password on connection.
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As a security measure, the keys used by known hosts are checked at each connection to prevent man-in-the-middle attacks.
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The first time you connect to the tablet, it will not be among the known hosts.
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In this situation rMview will present the option to add it to the known hosts, which should be done in a trusted network.
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Updates to the tablet's firmware modify the key used by it, so the next connection would see the mismatch between the old key and the new.
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Again rMview would prompt the user in this case with the option to update the key. Again this should be done in a trusted network.
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The `host_key_policy` parameter controls this behaviour:
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- `"ask"` is the default behaviour and prompts the user with a choice when the host key is unknown or not matching.
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- `"ignore_new"` ignores unknown keys but reports mismatches.
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- `"ignore_all"` ignores both unknown and not matching keys. Use at your own risk.
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- `"auto_add"` adds unknown keys without prompting but reports mismatches.
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The old `"insecure_auto_add_host": true` parameter is deprecated and equivalent to `"ignore_all"`.
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In case your `~/.ssh/known_hosts` file contains the relevant key associations, rMview should pick them up.
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If you use the "Add/Update" feature when prompted by rMview (for example after a tablet update) then `~/.ssh/known_hosts` will be ignored from then on.
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:warning: **Connecting after an update:**
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An update to the reMarkable tablet would change its "fingerprint" i.e. the identifier that signals we are connecting to the expected device (and not somebody impersonating it).
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When this happens you may get an error message upon connection.
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There are two main ways to fix this:
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1. Change your `~/.ssh/known_hosts` file to match the new fingerprint (you can get instructions by connecting manually via ssh).
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2. Set the `insecure_auto_add_host` setting to `true`, which will make rmview ignore the check.
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This is not recommended unless you are in a trusted network.
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:warning: **Key format error:**
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If you get an error when connect using a key, but the key seems ok when connecting manually with ssh, you probably need to convert the key to the PEM format (or re-generate it using the `-m PEM` option of `ssh-keygen`). See [here](https://github.com/paramiko/paramiko/issues/340#issuecomment-492448662) for details.
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@ -6,6 +6,7 @@ from PyQt5.QtWidgets import *
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import paramiko
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import struct
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import time
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from binascii import hexlify
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import sys
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import os
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@ -13,6 +14,43 @@ import logging
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log = logging.getLogger('rmview')
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class UnknownHostKeyException(paramiko.SSHException):
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def __init__(self, hostname, key):
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paramiko.SSHException.__init__(self, hostname, key)
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self.hostname = hostname
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self.key = key
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def __str__(self):
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msg = "Unknown host key for server '{}': got '{}'"
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return msg.format(
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self.hostname,
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self.key.get_base64(),
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)
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AddNewHostKey = paramiko.AutoAddPolicy
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class RejectNewHostKey(paramiko.MissingHostKeyPolicy):
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def missing_host_key(self, client, hostname, key):
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raise UnknownHostKeyException(hostname, key)
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class IgnoreNewHostKey(paramiko.MissingHostKeyPolicy):
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def missing_host_key(self, client, hostname, key):
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log.warning("Unknown %s host key for %s: %s", key.get_name(), hostname, hexlify(key.get_fingerprint()))
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HOST_KEY_POLICY = {
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"ask": RejectNewHostKey,
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"ignore_new": IgnoreNewHostKey,
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"ignore_all": IgnoreNewHostKey,
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"auto_add": AddNewHostKey
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}
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class rMConnectSignals(QObject):
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onConnect = pyqtSignal(object)
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@ -23,7 +61,8 @@ class rMConnect(QRunnable):
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_exception = None
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def __init__(self, address='10.11.99.1', username='root', password=None, key=None, timeout=1, onConnect=None, onError=None, insecure_auto_add_host=False, **kwargs):
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def __init__(self, address='10.11.99.1', username='root', password=None, key=None, timeout=1,
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onConnect=None, onError=None, host_key_policy=None, known_hosts=None, **kwargs):
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super(rMConnect, self).__init__()
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self.address = address
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self.signals = rMConnectSignals()
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@ -31,13 +70,23 @@ class rMConnect(QRunnable):
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self.signals.onConnect.connect(onConnect)
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if callable(onError):
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self.signals.onError.connect(onError)
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# self.key = key
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try:
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self.client = paramiko.SSHClient()
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if insecure_auto_add_host:
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self.client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
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else:
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self.client.load_system_host_keys()
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if host_key_policy != "ignore_all":
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if known_hosts and os.path.isfile(known_hosts):
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self.client.load_host_keys(known_hosts)
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log.info("LOADED %s", known_hosts)
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else:
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# ideally we would want to always load the system ones
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# and have the local keys have precedence, but paramiko gives
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# always precedence to system keys
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self.client.load_system_host_keys()
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policy = HOST_KEY_POLICY.get(host_key_policy, RejectNewHostKey)
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self.client.set_missing_host_key_policy(policy())
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if key is not None:
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key = os.path.expanduser(key)
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@ -59,7 +108,6 @@ class rMConnect(QRunnable):
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'password': password,
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'pkey': pkey,
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'timeout': timeout,
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'look_for_keys': False
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}
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except Exception as e:
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self._exception = e
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@ -4,10 +4,10 @@ from PyQt5.QtCore import *
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from . import resources
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from .workers import FrameBufferWorker, PointerWorker
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from .connection import rMConnect
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from .connection import rMConnect, RejectNewHostKey, AddNewHostKey, UnknownHostKeyException
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from .viewer import QtImageViewer
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from paramiko import BadHostKeyException, SSHException
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from paramiko import BadHostKeyException, HostKeys
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from .rmparams import *
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@ -38,8 +38,9 @@ class rMViewApp(QApplication):
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def __init__(self, args):
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super(rMViewApp, self).__init__(args)
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self.DEFAULT_CONFIG = QStandardPaths.standardLocations(QStandardPaths.ConfigLocation)[0]
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self.DEFAULT_CONFIG = os.path.join(self.DEFAULT_CONFIG, 'rmview.json')
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self.CONFIG_DIR = QStandardPaths.standardLocations(QStandardPaths.ConfigLocation)[0]
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self.DEFAULT_CONFIG = os.path.join(self.CONFIG_DIR, 'rmview.json')
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self.LOCAL_KNOWN_HOSTS = os.path.join(self.CONFIG_DIR, 'rmview_known_hosts')
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config_files = [] if len(args) < 2 else [args[1]]
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config_files += ['rmview.json', self.DEFAULT_CONFIG]
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@ -175,13 +176,27 @@ class rMViewApp(QApplication):
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else:
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return False
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# backwards compatibility
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if self.config['ssh'].get('insecure_auto_add_host') and 'host_key_policy' not in self.config['ssh']:
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log.warning("The 'insecure_auto_add_host' setting is deprecated, see documentation.")
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self.config['ssh']['host_key_policy'] = "ignore_all"
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if self.config['ssh']['host_key_policy'] == "auto_add":
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if not os.path.isfile(self.LOCAL_KNOWN_HOSTS):
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open(self.LOCAL_KNOWN_HOSTS, 'a').close()
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log.info(self.config)
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return True
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def requestConnect(self):
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def requestConnect(self, host_key_policy=None):
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self.viewer.setWindowTitle("rMview - Connecting...")
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args = self.config.get('ssh')
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if host_key_policy:
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args = args.copy()
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args['host_key_policy'] = host_key_policy
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self.threadpool.start(
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rMConnect(**self.config.get('ssh'),
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rMConnect(**args,
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known_hosts=self.LOCAL_KNOWN_HOSTS,
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onError=self.connectionError,
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onConnect=self.connected ) )
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@ -200,8 +215,6 @@ class rMViewApp(QApplication):
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self.ssh = ssh
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self.viewer.setWindowTitle("rMview - " + self.config.get('ssh').get('address'))
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# check we are dealing with RM1
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# cat /sys/devices/soc0/machine -> reMarkable 1.x
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_,out,_ = ssh.exec_command("cat /sys/devices/soc0/machine")
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rmv = out.read().decode("utf-8")
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version = re.fullmatch(r"reMarkable (\d+)\..*\n", rmv)
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@ -358,48 +371,63 @@ class rMViewApp(QApplication):
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icon = QPixmap(":/assets/dead.svg")
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icon.setDevicePixelRatio(self.devicePixelRatio())
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mbox.setIconPixmap(icon)
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mbox.addButton("Settings...", QMessageBox.ResetRole)
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mbox.addButton(QMessageBox.Cancel)
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if isinstance(e, BadHostKeyException):
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mbox.setDetailedText(str(e))
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mbox.setInformativeText(
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"<big>The host at %s has the wrong key.<br>"
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"This usually happens just after a software update on the tablet.</big><br><br>"
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"You have three options to fix this problem:"
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"You have three options to fix this permanently:"
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"<ol><li>"
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"Press Update to replace the old key with the new."
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"<br></li><li>"
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"Change your <code>~/.ssh/known_hosts</code> file to match the new fingerprint.<br>"
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"The easiest way to do this is connecting manually via ssh and follow the instructions."
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"<br></li><li>"
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"Set <code>\"insecure_auto_add_host\": true</code> to rmView\'s settings.<br>"
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"Set <code>\"host_key_policy\": \"ignore_new\"</code> in the <code>ssh</code> section of rmView\'s settings.<br>"
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"This is not recommended unless you are in a trusted network."
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"<br></li><li>"
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"Connect using username/password."
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"<br></li><ol>" % (self.config.get('ssh').get('address'))
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"<br></li><ol>" % (e.hostname)
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)
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elif isinstance(e, SSHException) and str(e).endswith('known_hosts'):
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mbox.addButton("Ignore", QMessageBox.NoRole)
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mbox.addButton("Update", QMessageBox.YesRole)
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elif isinstance(e, UnknownHostKeyException):
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mbox.setDetailedText(str(e))
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mbox.setInformativeText(
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"<big>The host at %s is unknown.<br>"
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"This usually happens if this is the first time you use ssh with your tablet.</big><br><br>"
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"You have three options to fix this problem:"
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"You have three options to fix this permanently:"
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"<ol><li>"
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"Press Add to add the key to the known hosts."
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"<br></li><li>"
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"Change your <code>~/.ssh/known_hosts</code> file to match the new fingerprint.<br>"
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"The easiest way to do this is connecting manually via ssh and follow the instructions."
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"<br></li><li>"
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"Set <code>\"insecure_auto_add_host\": true</code> to rmView\'s settings.<br>"
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"Set <code>\"host_key_policy\": \"ignore_new\"</code> in the <code>ssh</code> section of rmView\'s settings.<br>"
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"This is not recommended unless you are in a trusted network."
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"<br></li><li>"
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"Connect using username/password."
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"<br></li><ol>" % (self.config.get('ssh').get('address'))
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"<br></li><ol>" % (e.hostname)
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)
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mbox.addButton("Ignore", QMessageBox.NoRole)
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mbox.addButton("Add", QMessageBox.YesRole)
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else:
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mbox.setInformativeText("I could not connect to the reMarkable at %s:\n%s." % (self.config.get('ssh').get('address'), e))
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mbox.addButton(QMessageBox.Cancel)
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mbox.addButton("Settings...", QMessageBox.ResetRole)
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mbox.addButton(QMessageBox.Retry)
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mbox.setDefaultButton(QMessageBox.Retry)
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mbox.addButton(QMessageBox.Retry)
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mbox.setDefaultButton(QMessageBox.Retry)
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answer = mbox.exec()
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if answer == QMessageBox.Retry:
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self.requestConnect()
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elif answer == QMessageBox.Cancel:
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self.quit()
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elif answer == 1: # Ignore
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self.requestConnect(host_key_policy="ignore_all")
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elif answer == 2: # Add/Update
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if not os.path.isfile(self.LOCAL_KNOWN_HOSTS):
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open(self.LOCAL_KNOWN_HOSTS, 'a').close()
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hk = HostKeys(self.LOCAL_KNOWN_HOSTS)
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hk.add(e.hostname, e.key.get_name(), e.key)
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hk.save(self.LOCAL_KNOWN_HOSTS)
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log.info("Saved host key in %s", self.LOCAL_KNOWN_HOSTS)
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self.requestConnect()
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else:
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self.openSettings(prompt=False)
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self.quit()
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