429 lines
20 KiB
Python
429 lines
20 KiB
Python
#!/usr/bin/env python3
|
|
|
|
# Pythonized automated way of running https://sysadministrivia.com/news/hardening-ssh-security
|
|
# TODO: check for cryptography module. if it exists, we can do this entirely pythonically
|
|
# without ever needing to use subprocess/ssh-keygen, i think!
|
|
|
|
# Thanks to https://stackoverflow.com/a/39126754.
|
|
|
|
# Also, I need to re-write this. It's getting uglier.
|
|
|
|
# stdlib
|
|
import datetime
|
|
import glob
|
|
import os
|
|
import pwd
|
|
import re
|
|
import signal
|
|
import shutil
|
|
import subprocess # REMOVE WHEN SWITCHING TO PURE PYTHON
|
|
#### PREP FOR PURE PYTHON IMPLEMENTATION ####
|
|
# # non-stdlib - testing and automatic install if necessary.
|
|
# # TODO #
|
|
# - cryptography module won't generate new-format "openssh-key-v1" keys.
|
|
# - See https://github.com/pts/py_ssh_keygen_ed25519 for possible conversion to python 3
|
|
# - https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key
|
|
# - https://github.com/pyca/cryptography/issues/3509 and https://github.com/paramiko/paramiko/issues/1136
|
|
# has_crypto = False
|
|
# pure_py = False
|
|
# has_pip = False
|
|
# pipver = None
|
|
# try:
|
|
# import cryptography
|
|
# has_crypto = True
|
|
# except ImportError:
|
|
# # We'll try to install it. We set up the logic below.
|
|
# try:
|
|
# import pip
|
|
# has_pip = True
|
|
# # We'll use these to create a temporary lib path and remove it when done.
|
|
# import sys
|
|
# import tempfile
|
|
# except ImportError:
|
|
# # ABSOLUTE LAST fallback, if we got to THIS case, is to use subprocess.
|
|
# has_pip = False
|
|
# import subprocess
|
|
#
|
|
# # Try installing it then!
|
|
# if not all((has_crypto, )):
|
|
# # venv only included after python 3.3.x. We fallback to subprocess if we can't do dis.
|
|
# if sys.hexversion >= 0x30300f0:
|
|
# has_ensurepip = False
|
|
# import venv
|
|
# if not has_pip and sys.hexversion >= 0x30400f0:
|
|
# import ensurepip
|
|
# has_ensurepip = True
|
|
# temppath = tempfile.mkdtemp('_VENV')
|
|
# v = venv.create(temppath)
|
|
# if has_ensurepip and not has_pip:
|
|
# # This SHOULD be unnecessary, but we want to try really hard.
|
|
# ensurepip.bootstrap(root = temppath)
|
|
# import pip
|
|
# has_pip = True
|
|
# if has_pip:
|
|
# pipver = pip.__version__.split('.')
|
|
# # A thousand people are yelling at me for this.
|
|
# if int(pipver[0]) >= 10:
|
|
# from pip._internal import main as pipinstall
|
|
# else:
|
|
# pipinstall = pip.main
|
|
# if int(pipver[0]) >= 8:
|
|
# pipcmd = ['install',
|
|
# '--prefix={0}'.format(temppath),
|
|
# '--ignore-installed']
|
|
# else:
|
|
# pipcmd = ['install',
|
|
# '--install-option="--prefix={0}"'.format(temppath),
|
|
# '--ignore-installed']
|
|
# # Get the lib path.
|
|
# libpath = os.path.join(temppath, 'lib')
|
|
# if os.path.exists('{0}64'.format(libpath)) and not os.path.islink('{0}64'.format(libpath)):
|
|
# libpath += '64'
|
|
# for i in os.listdir(libpath): # TODO: make this more sane. We cheat a bit here by making assumptions.
|
|
# if re.search('python([0-9]+(\.[0-9]+)?)?$', i):
|
|
# libpath = os.path.join(libpath, i)
|
|
# break
|
|
# libpath = os.path.join(libpath, 'site-packages')
|
|
# sys.prefix = temppath
|
|
# for m in ('cryptography', 'ed25519'):
|
|
# pipinstall(['install', 'cryptography'])
|
|
# sys.path.append(libpath)
|
|
# try:
|
|
# import cryptography
|
|
# has_crypto = True
|
|
# except ImportError: # All that trouble for nothin'. Shucks.
|
|
# pass
|
|
#
|
|
# if all((has_crypto, )):
|
|
# pure_py = True
|
|
#
|
|
# if pure_py:
|
|
# from cryptography.hazmat.primitives import serialization as crypto_serialization
|
|
# from cryptography.hazmat.primitives.asymmetric import rsa
|
|
# from cryptography.hazmat.backends import default_backend as crypto_default_backend
|
|
#
|
|
|
|
# We need static backup suffixes.
|
|
tstamp = int(datetime.datetime.utcnow().timestamp())
|
|
|
|
# TODO: associate various config directives with version, too.
|
|
# For now, we use this for primarily CentOS 6.x, which doesn't support ED25519 and probably some of the MACs.
|
|
# Bastards.
|
|
# https://ssh-comparison.quendi.de/comparison/cipher.html at some point in the future...
|
|
# TODO: maybe implement some parsing of the ssh -Q stuff? https://superuser.com/a/869005/984616
|
|
# If you encounter a version incompatibility, please let me know!
|
|
# nmap --script ssh2-enum-algos -PN -sV -p22 <host>
|
|
magic_ver = 6.5
|
|
ssh_ver = subprocess.run(['ssh', '-V'], stderr = subprocess.PIPE).stderr.decode('utf-8').strip().split()[0]
|
|
# FUCK YOU, DEBIAN. FUCK YOU AND ALL OF YOUR DERIVATIVES. YOU'RE FUCKING TRASH.
|
|
# YOU BELONG NOWHERE NEAR A DATACENTER.
|
|
ssh_ver = float(re.sub('^(?:Open|Sun_)SSH_([0-9\.]+)(?:p[0-9]+)?(?:,.*)?.*$', '\g<1>', ssh_ver))
|
|
if ssh_ver >= magic_ver:
|
|
has_ed25519 = True
|
|
supported_keys = ('ed25519', 'rsa')
|
|
new_moduli = False
|
|
else:
|
|
has_ed25519 = False
|
|
supported_keys = ('rsa', )
|
|
new_moduli = False
|
|
# https://github.com/openssh/openssh-portable/commit/3e60d18fba1b502c21d64fc7e81d80bcd08a2092
|
|
if ssh_ver >= 8.1:
|
|
new_moduli = True
|
|
|
|
|
|
conf_options = {}
|
|
conf_options['sshd'] = {'KexAlgorithms': 'diffie-hellman-group-exchange-sha256',
|
|
'Protocol': '2',
|
|
'HostKey': ['/etc/ssh/ssh_host_rsa_key'],
|
|
#'PermitRootLogin': 'prohibit-password', # older daemons don't like "prohibit-..."
|
|
'PermitRootLogin': 'without-password',
|
|
'PasswordAuthentication': 'no',
|
|
'ChallengeResponseAuthentication': 'no',
|
|
'PubkeyAuthentication': 'yes',
|
|
'Ciphers': 'aes256-ctr,aes192-ctr,aes128-ctr',
|
|
'MACs': 'hmac-sha2-512,hmac-sha2-256'}
|
|
if has_ed25519:
|
|
conf_options['sshd']['HostKey'].append('/etc/ssh/ssh_host_ed25519_key')
|
|
conf_options['sshd']['KexAlgorithms'] = ','.join(('curve25519-sha256@libssh.org',
|
|
conf_options['sshd']['KexAlgorithms']))
|
|
conf_options['sshd']['Ciphers'] = ','.join((('chacha20-poly1305@openssh.com,'
|
|
'aes256-gcm@openssh.com,'
|
|
'aes128-gcm@openssh.com'),
|
|
conf_options['sshd']['Ciphers']))
|
|
conf_options['sshd']['MACs'] = ','.join((('hmac-sha2-512-etm@openssh.com,'
|
|
'hmac-sha2-256-etm@openssh.com,'
|
|
'umac-128-etm@openssh.com'),
|
|
conf_options['sshd']['MACs'],
|
|
'umac-128@openssh.com'))
|
|
# Uncomment if this is further configured
|
|
#conf_options['sshd']['AllowGroups'] = 'ssh-user'
|
|
|
|
conf_options['ssh'] = {'Host': {'*': {'KexAlgorithms': 'diffie-hellman-group-exchange-sha256',
|
|
'PubkeyAuthentication': 'yes',
|
|
'HostKeyAlgorithms': 'ssh-rsa'}}}
|
|
if has_ed25519:
|
|
conf_options['ssh']['Host']['*']['KexAlgorithms'] = ','.join(('curve25519-sha256@libssh.org',
|
|
conf_options['ssh']['Host']['*']['KexAlgorithms']))
|
|
conf_options['ssh']['Host']['*']['HostKeyAlgorithms'] = ','.join(
|
|
(('ssh-ed25519-cert-v01@openssh.com,'
|
|
'ssh-rsa-cert-v01@openssh.com,'
|
|
'ssh-ed25519'),
|
|
conf_options['ssh']['Host']['*']['HostKeyAlgorithms']))
|
|
|
|
|
|
def hostKeys(buildmoduli):
|
|
# Starting haveged should help lessen the time load a non-negligible amount, especially on virtual platforms.
|
|
if os.path.lexists('/usr/bin/haveged'):
|
|
# We could use psutil here, but then that's a python dependency we don't need.
|
|
# We could parse the /proc directory, but that's quite unnecessary. pgrep's installed by default on
|
|
# most distros.
|
|
with open(os.devnull, 'wb') as devnull:
|
|
if subprocess.run(['pgrep', 'haveged'], stdout = devnull).returncode != 0:
|
|
subprocess.run(['haveged'], stdout = devnull)
|
|
#Warning: The moduli stuff takes a LONG time to run. Hours.
|
|
if buildmoduli:
|
|
if not new_moduli:
|
|
subprocess.run(['ssh-keygen',
|
|
'-G', '/etc/ssh/moduli.all',
|
|
'-b', '4096',
|
|
'-q'])
|
|
subprocess.run(['ssh-keygen',
|
|
'-T', '/etc/ssh/moduli.safe',
|
|
'-f', '/etc/ssh/moduli.all',
|
|
'-q'])
|
|
else:
|
|
subprocess.run(['ssh-keygen',
|
|
'-q',
|
|
'-M', 'generate',
|
|
'-O', 'bits=4096',
|
|
'/etc/ssh/moduli.all'])
|
|
subprocess.run(['ssh-keygen',
|
|
'-q',
|
|
'-M', 'screen',
|
|
'-f', '/etc/ssh/moduli.all',
|
|
'/etc/ssh/moduli.safe'])
|
|
if os.path.lexists('/etc/ssh/moduli'):
|
|
os.rename('/etc/ssh/moduli', '/etc/ssh/moduli.old')
|
|
os.rename('/etc/ssh/moduli.safe', '/etc/ssh/moduli')
|
|
os.remove('/etc/ssh/moduli.all')
|
|
for suffix in ('', '.pub'):
|
|
for k in glob.glob('/etc/ssh/ssh_host_*key{0}'.format(suffix)):
|
|
os.rename(k, '{0}.old.{1}'.format(k, tstamp))
|
|
if has_ed25519:
|
|
subprocess.run(['ssh-keygen',
|
|
'-t', 'ed25519',
|
|
'-f', '/etc/ssh/ssh_host_ed25519_key',
|
|
'-q',
|
|
'-N', ''])
|
|
subprocess.run(['ssh-keygen',
|
|
'-t', 'rsa',
|
|
'-b', '4096',
|
|
'-f', '/etc/ssh/ssh_host_rsa_key',
|
|
'-q',
|
|
'-N', ''])
|
|
# We currently don't use this, but for simplicity's sake let's return the host keys.
|
|
hostkeys = {}
|
|
for k in supported_keys:
|
|
with open('/etc/ssh/ssh_host_{0}_key.pub'.format(k), 'r') as f:
|
|
hostkeys[k] = f.read()
|
|
return(hostkeys)
|
|
|
|
def config(opts, t):
|
|
special = {'sshd': {}, 'ssh': {}}
|
|
# We need to handle these directives a little differently...
|
|
special['sshd']['opts'] = ['Match']
|
|
special['sshd']['filters'] = ['User', 'Group', 'Host', 'LocalAddress', 'LocalPort', 'Address']
|
|
# These are arguments supported by each of the special options. We'll use this to verify entries.
|
|
special['sshd']['args'] = ['AcceptEnv', 'AllowAgentForwarding', 'AllowGroups', 'AllowStreamLocalForwarding',
|
|
'AllowTcpForwarding', 'AllowUsers', 'AuthenticationMethods', 'AuthorizedKeysCommand',
|
|
'AuthorizedKeysCommandUser', 'AuthorizedKeysFile', 'AuthorizedPrincipalsCommand',
|
|
'AuthorizedPrincipalsCommandUser', 'AuthorizedPrincipalsFile', 'Banner',
|
|
'ChrootDirectory', 'ClientAliveCountMax', 'ClientAliveInterval', 'DenyGroups',
|
|
'DenyUsers', 'ForceCommand', 'GatewayPorts', 'GSSAPIAuthentication',
|
|
'HostbasedAcceptedKeyTypes', 'HostbasedAuthentication',
|
|
'HostbasedUsesNameFromPacketOnly', 'IPQoS', 'KbdInteractiveAuthentication',
|
|
'KerberosAuthentication', 'MaxAuthTries', 'MaxSessions', 'PasswordAuthentication',
|
|
'PermitEmptyPasswords', 'PermitOpen', 'PermitRootLogin', 'PermitTTY', 'PermitTunnel',
|
|
'PermitUserRC', 'PubkeyAcceptedKeyTypes', 'PubkeyAuthentication', 'RekeyLimit',
|
|
'RevokedKeys', 'StreamLocalBindMask', 'StreamLocalBindUnlink', 'TrustedUserCAKeys',
|
|
'X11DisplayOffset', 'X11Forwarding', 'X11UseLocalHost']
|
|
special['ssh']['opts'] = ['Host', 'Match']
|
|
special['ssh']['args'] = ['canonical', 'exec', 'host', 'originalhost', 'user', 'localuser']
|
|
cf = '/etc/ssh/{0}_config'.format(t)
|
|
shutil.copy2(cf, '{0}.bak.{1}'.format(cf, tstamp))
|
|
with open(cf, 'r') as f:
|
|
conf = f.readlines()
|
|
conf.append('\n\n# Added per https://sysadministrivia.com/news/hardening-ssh-security\n\n')
|
|
confopts = []
|
|
# Get an index of directives pre-existing in the config file.
|
|
for line in conf[:]:
|
|
opt = line.split()
|
|
if opt:
|
|
if not re.match('^(#.*|\s+.*)$', opt[0]):
|
|
confopts.append(opt[0])
|
|
# We also need to modify the config file- comment out starting with the first occurrence of the
|
|
# specopts, if it exists. This is why we make a backup.
|
|
commentidx = None
|
|
for idx, i in enumerate(conf):
|
|
if re.match('^({0})\s+.*$'.format('|'.join(special[t]['opts'])), i):
|
|
commentidx = idx
|
|
break
|
|
if commentidx is not None:
|
|
idx = commentidx
|
|
while idx <= (len(conf) - 1):
|
|
conf[idx] = '#{0}'.format(conf[idx])
|
|
idx += 1
|
|
# Now we actually start replacing/adding some major configuration.
|
|
for o in opts.keys():
|
|
if o in special[t]['opts'] or isinstance(opts[o], dict):
|
|
# We need to put these at the bottom of the file due to how they're handled by sshd's config parsing.
|
|
continue
|
|
# We handle these a little specially too- they're for multiple lines sharing the same directive.
|
|
# Since the config should be explicit, we remove any existing entries specified that we find.
|
|
else:
|
|
if o in confopts:
|
|
# If I was more worried about recursion, or if I was appending here, I should use conf[:].
|
|
# But I'm not. So I won't.
|
|
for idx, opt in enumerate(conf):
|
|
if re.match('^{0}(\s.*)?\n$'.format(o), opt):
|
|
conf[idx] = '#{0}'.format(opt)
|
|
# Here we handle the "multiple-specifying" options- notably, HostKey.
|
|
if isinstance(opts[o], list):
|
|
for l in opts[o]:
|
|
if l is not None:
|
|
conf.append('{0} {1}\n'.format(o, l))
|
|
else:
|
|
conf.append('{0}\n'.format(o))
|
|
else:
|
|
# So it isn't something we explicitly save until the end (such as a Match or Host),
|
|
# and it isn't something that's specified multiple times.
|
|
if opts[o] is not None:
|
|
conf.append('{0} {1}\n'.format(o, opts[o]))
|
|
else:
|
|
conf.append('{0}\n'.format(o))
|
|
# NOW we can add the Host/Match/etc. directives.
|
|
for o in opts.keys():
|
|
if isinstance(opts[o], dict):
|
|
for k in opts[o].keys():
|
|
conf.append('{0} {1}\n'.format(o, k))
|
|
for l in opts[o][k].keys():
|
|
if opts[o][k][l] is not None:
|
|
conf.append('\t{0} {1}\n'.format(l, opts[o][k][l]))
|
|
else:
|
|
conf.append('\t{0}\n'.format(l))
|
|
with open(cf, 'w') as f:
|
|
f.write(''.join(conf))
|
|
return()
|
|
|
|
def clientKeys(user = 'root'):
|
|
uid = pwd.getpwnam(user).pw_uid
|
|
gid = pwd.getpwnam(user).pw_gid
|
|
homedir = os.path.expanduser('~{0}'.format(user))
|
|
sshdir = '{0}/.ssh'.format(homedir)
|
|
os.makedirs(sshdir, mode = 0o700, exist_ok = True)
|
|
if has_ed25519:
|
|
if not os.path.lexists('{0}/id_ed25519'.format(sshdir)) \
|
|
and not os.path.lexists('{0}/id_ed25519.pub'.format(sshdir)):
|
|
subprocess.run(['ssh-keygen',
|
|
'-t', 'ed25519',
|
|
'-o',
|
|
'-a', '100',
|
|
'-f', '{0}/id_ed25519'.format(sshdir),
|
|
'-q',
|
|
'-N', ''])
|
|
if not os.path.lexists('{0}/id_rsa'.format(sshdir)) and not os.path.lexists('{0}/id_rsa.pub'.format(sshdir)):
|
|
if has_ed25519:
|
|
subprocess.run(['ssh-keygen',
|
|
'-t', 'rsa',
|
|
'-b', '4096',
|
|
'-o',
|
|
'-a', '100',
|
|
'-f', '{0}/id_rsa'.format(sshdir),
|
|
'-q',
|
|
'-N', ''])
|
|
else:
|
|
subprocess.run(['ssh-keygen',
|
|
'-t', 'rsa',
|
|
'-b', '4096',
|
|
'-a', '100',
|
|
'-f', '{0}/id_rsa'.format(sshdir),
|
|
'-q',
|
|
'-N', ''])
|
|
for basedir, dirs, files in os.walk(sshdir):
|
|
os.chown(basedir, uid, gid)
|
|
os.chmod(basedir, 0o700)
|
|
for f in files:
|
|
os.chown(os.path.join(basedir, f), uid, gid)
|
|
os.chmod(os.path.join(basedir, f), 0o600)
|
|
if 'pubkeys' not in globals():
|
|
pubkeys = {}
|
|
pubkeys[user] = {}
|
|
for k in supported_keys:
|
|
with open('{0}/id_{1}.pub'.format(sshdir, k), 'r') as f:
|
|
pubkeys[user][k] = f.read()
|
|
return(pubkeys)
|
|
|
|
def daemonMgr():
|
|
# In case the script is running without sshd running.
|
|
pidfile = '/var/run/sshd.pid'
|
|
if not os.path.isfile(pidfile):
|
|
return()
|
|
# We're about to do somethin' stupid. Let's make it a teeny bit less stupid.
|
|
with open(os.devnull, 'w') as devnull:
|
|
confchk = subprocess.run(['sshd', '-T'], stdout = devnull)
|
|
if confchk.returncode != 0:
|
|
for suffix in ('', '.pub'):
|
|
for k in glob.glob('/etc/ssh/ssh_host_*key{0}'.format(suffix)):
|
|
os.rename('{0}.old.{1}'.format(k, tstamp), k)
|
|
for conf in ('', 'd'):
|
|
cf = '/etc/ssh/ssh{0}_config'.format(conf)
|
|
os.rename('{0}.{1}'.format(cf, tstamp),
|
|
cf)
|
|
exit('OOPS. We goofed. Backup restored and bailing out.')
|
|
# We need to restart sshd once we're done. I feel dirty doing this, but this is the most cross-platform way I can
|
|
# do it. First, we need the path to the PID file.
|
|
# TODO: do some kind of better way of doing this.
|
|
with open('/etc/ssh/sshd_config', 'r') as f:
|
|
for line in f.readlines():
|
|
if re.search('^\s*PidFile\s+.*', line):
|
|
pidfile = re.sub('^\s*PidFile\s+(.*)(#.*)?$', '\g<1>', line)
|
|
break
|
|
with open(pidfile, 'r') as f:
|
|
pid = int(f.read().strip())
|
|
os.kill(pid, signal.SIGHUP)
|
|
return()
|
|
|
|
def main():
|
|
self_pidfile = '/tmp/sshsecure.pid'
|
|
is_running = False
|
|
# First, check to see if we're already running.
|
|
# This is where I'd put a psutil call... IF I HAD ONE.
|
|
if os.path.isfile(self_pidfile):
|
|
is_running = subprocess.run(['pgrep', '-F', self_pidfile], stdout = subprocess.PIPE)
|
|
if is_running.stdout.decode('utf-8').strip() != '':
|
|
# We're still running. Exit gracefully.
|
|
print('We seem to still be running from a past execution; exiting')
|
|
exit(0)
|
|
else:
|
|
# It's a stale PID file.
|
|
os.remove(self_pidfile)
|
|
with open(self_pidfile, 'w') as f:
|
|
f.write(str(os.getpid()) + '\n')
|
|
_chkfile = '/etc/ssh/.aif-generated'
|
|
if not os.path.isfile(_chkfile):
|
|
# Warning: The moduli stuff can take a LONG time to run. Hours.
|
|
buildmoduli = True
|
|
hostKeys(buildmoduli)
|
|
for t in ('sshd', 'ssh'):
|
|
config(conf_options[t], t)
|
|
clientKeys()
|
|
with open(_chkfile, 'w') as f:
|
|
f.write(('ssh, sshd, and hostkey configurations/keys have been modified by sshsecure.py from OpTools.\n'
|
|
'https://git.square-r00t.net/OpTools/\n'))
|
|
daemonMgr()
|
|
os.remove(self_pidfile)
|
|
return()
|
|
|
|
if __name__ == '__main__':
|
|
main()
|