letsencrypt-tiny

   1 #!/usr/bin/env python3
   2 ## Call with "--help" for documentation.
   3
   4 import argparse, configparser, itertools, stat, os, os.path, sys, subprocess, datetime
   5
   6 ## Helper functions
   7 def readConfig(fname, defSection = 'DEFAULT'):
   8     config = configparser.ConfigParser()
   9     with open(fname) as file:
  10         stream = itertools.chain(("["+defSection+"]\n",), file)
  11         config.read_file(stream)
  12     return config
  13
  14 def certfile(name):
  15     global config
  16     return os.path.join(config['dirs']['certs'], name + ".crt" )
  17
  18 def keyfile(name):
  19     global config
  20     return os.path.join(config['dirs']['keys'], name + ".key")
  21
  22 def make_backup(fname):
  23     if os.path.exists(fname):
  24         backupname = os.path.basename(fname) + "." + str(datetime.date.today())
  25         i = 0
  26         while True:
  27             backupfile = os.path.join(config['dirs']['backups'], backupname + "." + str(i))
  28             if not os.path.exists(backupfile):
  29                 os.rename(fname, backupfile)
  30                 break
  31             elif i >= 100:
  32                 print("Somehow it's really hard to find a name for the backup file...")
  33             i += 1
  34     assert not os.path.exists(fname)
  35
  36 def trigger_hook(hook):
  37     global config
  38     exe = config['hooks'].get(hook)
  39     if exe is not None:
  40         subprocess.check_call([exe])
  41
  42 def key_mtime(name):
  43     return datetime.datetime.fromtimestamp(os.stat(keyfile(name)).st_mtime)
  44
  45 def cert_expiry(name):
  46     from certcheck import cert_expiry_date
  47     return cert_expiry_date(certfile(name))
  48
  49 ## Work functions, operating on file names
  50
  51 ## The interesting work
  52 def acme(keyfilename, certfilename, domains):
  53     global config
  54     accountkey = config['acme']['account-key']
  55     csrfilename = certfilename + '.csr.tmp'
  56     assert os.path.exists(keyfilename)
  57     assert accountkey
  58     # Generating the CSR is done by a shell script
  59     exe = os.path.join(os.path.dirname(__file__), 'gencsr')
  60     csr = subprocess.check_output([exe, keyfilename] + domains)
  61     assert not os.path.exists(csrfilename)
  62     with open(csrfilename, 'wb') as file:
  63         file.write(csr)
  64     # call acme-tiny as a script
  65     acme_tiny = os.path.join(config['acme']['acme-tiny'], 'acme_tiny.py')
  66     signed_crt = subprocess.check_output(["python", acme_tiny, "--quiet", "--account-key", accountkey, "--csr", csrfilename, "--acme-dir", config['acme']['challenge-dir']])
  67     # save new certificate
  68     make_backup(certfilename)
  69     with open(certfilename, 'wb') as f:
  70         f.write(signed_crt)
  71     # clean up
  72     os.remove(csrfilename)
  73
  74 def openssl_genrsa(keyfilename):
  75     with subprocess.Popen(["openssl", "genrsa", str(int(config['DEFAULT']['key-length']))], stdout=subprocess.PIPE, stderr=subprocess.PIPE) as f:
  76         (stdout, stderr) = f.communicate()
  77         if f.returncode:
  78             sys.stderr.write(stderr)
  79             raise Exception("Error while generating private key")
  80     # Now we have a key, save it. This should never overwrite anything.
  81     assert not os.path.exists(keyfilename)
  82     with open(keyfilename, 'wb') as f:
  83         f.write(stdout)
  84
  85 ## High-level functions, operating on nice key names
  86 def request_cert(name):
  87     global config
  88     if not os.path.exists(keyfile(name)):
  89         raise Exception("No such key: {}".format(name))
  90     domains = config['DEFAULT']['domains'].split()
  91     print("Obtaining certificate '{}' for domains: {}".format(name, ' '.join(domains)))
  92     acme(keyfile(name), certfile(name), domains)
  93
  94 def generate_key(name):
  95     print("Generating new private key '{}'".format(name))
  96     openssl_genrsa(keyfile(name))
  97
  98 def check_staging(live, staging):
  99     '''Returns 0 if nothing was done, 1 if a stage key is present but has to be kept, 2 is a stage key was unstaged.'''
 100     if not os.path.exists(keyfile(staging)):
 101         return 0
 102
 103     staging_time = datetime.timedelta(hours = int(config['timing'].get('staging-hours', 0)))
 104     key_age = datetime.datetime.now() - key_mtime(staging)
 105     if key_age < staging_time:
 106         return 1
 107     print("Unstaging '{}' to '{}'".format(staging, live))
 108     # unstage the key!
 109     make_backup(keyfile(live))
 110     os.rename(keyfile(staging), keyfile(live))
 111     make_backup(certfile(live))
 112     os.rename(certfile(staging), certfile(live))
 113     return 2
 114
 115 def auto_renewal(live, staging):
 116     '''Returns 0 if nothing was done, 1 if only certs were changed, 2 if certs and keys were changed.'''
 117     max_key_age = datetime.timedelta(days = int(config['timing']['max-key-age-days']))
 118     renew_cert_time = datetime.timedelta(days = int(config['timing']['renew-cert-before-expiry-days']))
 119
 120     # determine what to do
 121     now = datetime.datetime.now()
 122     key_age = now - key_mtime(live)
 123     cert_validity = cert_expiry(live) - now
 124     need_new_key = key_age >= max_key_age
 125     need_new_cert = cert_validity <= renew_cert_time
 126     if need_new_cert and key_age + renew_cert_time >= max_key_age:
 127         # We are about to request a new certificate, and within <renew_cert_time>, we need a new key: Get the new key now
 128         need_new_key = True
 129
 130     # Do it
 131     if need_new_key:
 132         generate_key(staging)
 133         request_cert(staging)
 134         check_staging(live, staging) # we may want to immediately enable the new key & cert
 135         return 2
 136     elif need_new_cert:
 137         request_cert(live)
 138         return 1
 139     else:
 140         return 0
 141
 142 ## Main
 143 if __name__ == "__main__":
 144     # allow overwriting some values on the command-line
 145     parser = argparse.ArgumentParser(description='Generate and (automatically) renew certificates, optionally providing staging for new keys')
 146     parser.add_argument("-c", "--config",
 147                         dest="config",
 148                         help="The configuration file")
 149     parser.add_argument("-k", "--hooks",
 150                         dest="hooks", action="store_true",
 151                         help="Trigger hooks.")
 152     parser.add_argument("action", metavar='ACTION', nargs=1,
 153                         help="The action to perform. Possible values: init, renew, cron")
 154     args = parser.parse_args()
 155
 156     # read config, sanity check
 157     if not os.path.isfile(args.config):
 158         raise Exception("The config file does not exist: "+args.config)
 159     global config
 160     config = readConfig(args.config)
 161
 162     live = config['files']['live']
 163     staging = config['files']['staging']
 164     if args.action[0] == 'renew':
 165         request_cert(live)
 166         if os.path.exists(keyfile(staging)) and os.path.exists(certfile(staging)):
 167             request_cert(staging)
 168         # trigger the "new cert" hook
 169         if args.hooks:
 170             trigger_hook('post-certchange')
 171     elif args.action[0] == 'cron':
 172         # First, check if we need to unstage a staging key
 173         unstaged = check_staging(live, staging)
 174         if unstaged >= 1:
 175             # A staging key is present, do *not* check for renewal
 176             if unstaged >= 2 and args.hooks:
 177                 # trigger all the hooks
 178                 trigger_hook('post-certchange')
 179                 trigger_hook('post-keychange')
 180         else:
 181             # Check if we need to renew anything
 182             renewed = auto_renewal(live, staging)
 183             if args.hooks:
 184                 if renewed >= 1:
 185                     trigger_hook('post-certchange')
 186                 if renewed >= 2:
 187                     trigger_hook('post-keychange')
 188     elif args.action[0] == 'init':
 189         # create directories with appropriate permissions
 190         try:
 191             os.makedirs(config['dirs']['certs'], mode = 0o755, exist_ok = True)
 192             os.makedirs(config['dirs']['keys'], mode = 0o710, exist_ok = True)
 193             os.makedirs(config['dirs']['backups'], mode = 0o700, exist_ok = True)
 194         except OSError:
 195             pass
 196         # if necessary, generate ACME account key
 197         accountkey = config['acme']['account-key']
 198         if not os.path.exists(accountkey):
 199             print("Generating new ACME key")
 200             openssl_genrsa(accountkey)
 201         # if necessary, generate key + certificate
 202         live = config['files']['live']
 203         if not os.path.exists(keyfile(live)):
 204             generate_key(live)
 205             request_cert(live)
 206             if args.hooks:
 207                 trigger_hook('post-certchange')
 208                 trigger_hook('post-keychange')
 209     else:
 210         raise Exception("Unknown action {}".format(args.action))