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Merge pull request #650 from skuhl/hw-improve

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Improve hostwatch robustness and documentation
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Brian May 2021-06-03 07:28:12 +10:00 committed by GitHub
commit 78b80709f2
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2 changed files with 69 additions and 19 deletions
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9
docs/manpage.rst
View File

@ -89,6 +89,13 @@ Options
few subnets over the VPN, you probably would prefer to
keep using your local DNS server for everything else.
:program:`sshuttle` tries to store a cache of the hostnames in
~/.sshuttle.hosts on the remote host. Similarly, it tries to read
the file when you later reconnect to the host with --auto-hosts
enabled to quickly populate the host list. When troubleshooting
this feature, try removing this file on the remote host when
sshuttle is not running.
.. option:: -N, --auto-nets
In addition to the subnets provided on the command
@ -178,7 +185,7 @@ Options
A comma-separated list of hostnames to use to
initialize the :option:`--auto-hosts` scan algorithm.
:option:`--auto-hosts` does things like poll local SMB servers
:option:`--auto-hosts` does things like poll netstat output
for lists of local hostnames, but can speed things up
if you use this option to give it a few names to start
from.

79
sshuttle/hostwatch.py
View File

@ -15,6 +15,8 @@ POLL_TIME = 60 * 15
NETSTAT_POLL_TIME = 30
CACHEFILE = os.path.expanduser('~/.sshuttle.hosts')
# Have we already failed to write CACHEFILE?
CACHE_WRITE_FAILED = False
hostnames = {}
queue = {}
@ -31,7 +33,10 @@ def _is_ip(s):
def write_host_cache():
"""If possible, write our hosts file to disk so future connections
can reuse the hosts that we already found."""
tmpname = '%s.%d.tmp' % (CACHEFILE, os.getpid())
global CACHE_WRITE_FAILED
try:
f = open(tmpname, 'wb')
for name, ip in sorted(hostnames.items()):
@ -39,7 +44,15 @@ def write_host_cache():
f.close()
os.chmod(tmpname, 384) # 600 in octal, 'rw-------'
os.rename(tmpname, CACHEFILE)
finally:
CACHE_WRITE_FAILED = False
except (OSError, IOError):
# Write message if we haven't yet or if we get a failure after
# a previous success.
if not CACHE_WRITE_FAILED:
log("Failed to write host cache to temporary file "
"%s and rename it to %s" % (tmpname, CACHEFILE))
CACHE_WRITE_FAILED = True
try:
os.unlink(tmpname)
except BaseException:
@ -47,25 +60,34 @@ def write_host_cache():
def read_host_cache():
"""If possible, read the cache file from disk to populate hosts that
were found in a previous sshuttle run."""
try:
f = open(CACHEFILE)
except IOError:
except (OSError, IOError):
_, e = sys.exc_info()[:2]
if e.errno == errno.ENOENT:
return
else:
raise
log("Failed to read existing host cache file %s on remote host"
% CACHEFILE)
return
for line in f:
words = line.strip().split(',')
if len(words) == 2:
(name, ip) = words
name = re.sub(r'[^-\w\.]', '-', name).strip()
# Remove characters that shouldn't be in IP
ip = re.sub(r'[^0-9.]', '', ip).strip()
if name and ip:
found_host(name, ip)
def found_host(name, ip):
"""The provided name maps to the given IP. Add the host to the
hostnames list, send the host to the sshuttle client via
stdout, and write the host to the cache file.
"""
hostname = re.sub(r'\..*', '', name)
hostname = re.sub(r'[^-\w\.]', '_', hostname)
if (ip.startswith('127.') or ip.startswith('255.') or
@ -84,29 +106,37 @@ def found_host(name, ip):
def _check_etc_hosts():
debug2(' > hosts')
for line in open('/etc/hosts'):
line = re.sub(r'#.*', '', line)
words = line.strip().split()
if not words:
continue
ip = words[0]
names = words[1:]
if _is_ip(ip):
debug3('< %s %r' % (ip, names))
for n in names:
check_host(n)
found_host(n, ip)
"""If possible, read /etc/hosts to find hosts."""
filename = '/etc/hosts'
debug2(' > Reading %s on remote host' % filename)
try:
for line in open(filename):
line = re.sub(r'#.*', '', line) # remove comments
words = line.strip().split()
if not words:
continue
ip = words[0]
if _is_ip(ip):
names = words[1:]
debug3('< %s %r' % (ip, names))
for n in names:
check_host(n)
found_host(n, ip)
except (OSError, IOError):
debug1("Failed to read %s on remote host" % filename)
def _check_revdns(ip):
"""Use reverse DNS to try to get hostnames from an IP addresses."""
debug2(' > rev: %s' % ip)
try:
r = socket.gethostbyaddr(ip)
debug3('< %s' % r[0])
check_host(r[0])
found_host(r[0], ip)
except (socket.herror, UnicodeError):
except (OSError, socket.error, UnicodeError):
# This case is expected to occur regularly.
# debug3('< %s gethostbyaddr failed on remote host' % ip)
pass
@ -134,7 +164,14 @@ def _check_netstat():
log('%r failed: %r' % (argv, e))
return
# The same IPs may appear multiple times. Consolidate them so the
# debug message doesn't print the same IP repeatedly.
ip_list = []
for ip in re.findall(r'\d+\.\d+\.\d+\.\d+', content):
if ip not in ip_list:
ip_list.append(ip)
for ip in sorted(ip_list):
debug3('< %s' % ip)
check_host(ip)
@ -179,13 +216,19 @@ def hw_main(seed_hosts, auto_hosts):
while 1:
now = time.time()
# For each item in the queue
for t, last_polled in list(queue.items()):
(op, args) = t
if not _stdin_still_ok(0):
break
# Determine if we need to run.
maxtime = POLL_TIME
# netstat runs more often than other jobs
if op == _check_netstat:
maxtime = NETSTAT_POLL_TIME
# Check if this jobs needs to run.
if now - last_polled > maxtime:
queue[t] = time.time()
op(*args)
@ -195,5 +238,5 @@ def hw_main(seed_hosts, auto_hosts):
break
# FIXME: use a smarter timeout based on oldest last_polled
if not _stdin_still_ok(1):
if not _stdin_still_ok(1): # sleeps for up to 1 second
break