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Check expiring certificates
import datetime
import logging
import socket
import ssl
YOUR_DOMAIN = 'serverlesscode.com'
WARNING_BUFFER = 14
logger = logging.getLogger()
logger.setLevel(logging.INFO)
ssl_date_fmt = r'%b %d %H:%M:%S %Y %Z'
class AlreadyExpired(Exception):
pass
def ssl_expires_in(hostname, buffer_days=14):
"""Gets the SSL cert from a given hostname and checks if it expires within buffer_days days"""
context = ssl.create_default_context()
conn = context.wrap_socket(
socket.socket(socket.AF_INET),
server_hostname=hostname,
)
# 3 second timeout because Lambda has runtime limitations
conn.settimeout(3.0)
conn.connect((hostname, 443))
ssl_info = conn.getpeercert()
expires = datetime.datetime.strptime(ssl_info['notAfter'], ssl_date_fmt)
# if the cert expires in less than two weeks, we should reissue it
if expires < (datetime.datetime.utcnow() + datetime.timedelta(days=buffer_days)):
# expires sooner than the buffer
return True
elif expires < datetime.datetime.utcnow():
# cert has already expired - uhoh!
raise AlreadyExpired("Cert expired at %s" % ssl_info['notAfter'])
else:
# everything is fine
return False
def lambda_handler(event, context):
try:
if not ssl_expires_in(YOUR_DOMAIN, WARNING_BUFFER):
logger.info("SSL certificate doesn't expire for a while - you're set!")
return {"success": True, "cert_status": "valid"}
else:
logger.warning("SSL certificate expires soon")
return {"success": True, "cert_status": "expiring soon"}
except AlreadyExpired as e:
logger.exception("Certificate is expired, get worried!")
return {"success": True, "cert_status": "expired"}
except Exception as e:
logger.exception("Failed to get certificate info")
return {"success": False, "cert_status": "unknown"}
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