diff --git a/plugins/check_otp b/plugins/check_otp
index a617c88..460bba9 100755
--- a/plugins/check_otp
+++ b/plugins/check_otp
@@ -2,10 +2,10 @@
 #
 # check_otp - Nagios check plugin for LinOTP/PrivacyIDEA OTP validation
 #
-# Version 1.0, latest version, documentation and bugtracker available at:
+# Version 1.1, latest version, documentation and bugtracker available at:
 #              https://gitlab.lindenaar.net/scripts/nagios-plugins
 #
-# Copyright (c) 2016 Frederik Lindenaar
+# Copyright (c) 2018 Frederik Lindenaar
 #
 # This script is free software: you can redistribute and/or modify it under the
 # terms of version 3 of the GNU General Public License as published by the Free
@@ -25,14 +25,18 @@ from hashlib import sha1
 from getpass import getpass
 from urllib import urlencode
 from urllib2 import Request, HTTPError, URLError, urlopen
+from ssl import CertificateError, \
+                create_default_context as create_default_SSL_context, \
+                _create_unverified_context as create_unverified_SSL_context
 from base64 import b16decode, b32decode, standard_b64decode
 from argparse import ArgumentParser as StandardArgumentParser, FileType, \
               _StoreAction as StoreAction, _StoreConstAction as StoreConstAction
 
 # Constants (no need to change but allows for easy customization)
-VERSION="1.0"
+VERSION="1.1"
 PROG_NAME=os.path.splitext(os.path.basename(__file__))[0]
 PROG_VERSION=PROG_NAME + ' ' + VERSION
+HTTP_AGENT=PROG_NAME + '/' + VERSION
 URL_API_SUFFIX='/validate/check'
 ENV_VAR_USER='USER_NAME'
 ENV_VAR_PWD='USER_PASSWORD'
@@ -222,8 +226,18 @@ def parse_args():
                         help='port number to connect to (only used with -H)')
     parser.add_argument('-P', '--path',
                         help='URL path to be used (only used with -H)')
+
     parser.add_argument('-S', '--no-ssl',   action='store_true',
                         help='connect WITHOUT SSL (only used with -H)')
+    parser.add_argument('--no-ssl-validation',
+                        action='store_const', dest='sslcontext',
+                        const=create_unverified_SSL_context(),
+                        default=create_default_SSL_context(),
+                        help='Do not validate server SSL certificate (DANGEROUS)')
+    parser.add_argument('--cacert',
+                        help='CA Certificate file for SSL server validation')
+    parser.add_argument('--capath',
+                        help='CA Certificate directory for SSL server validation')
 
     parser.add_argument('-n', '--name', default=envvar(ENV_VAR_NAME, PROG_NAME),
                         help="name in authentication request for logging "
@@ -319,6 +333,15 @@ def parse_args():
         if not isempty(args.path):
             args.url+= args.path if args.path[0]=='/' else '/' + args.path
 
+    # Pass-on CA file/path to SSLContext if provided on the command line
+    if not isempty(args.cacert):
+        try:
+            args.sslcontext.load_verify_locations(cafile=args.cacert)
+        except IOError as e:
+            args.cmdparser.error("cafile '%s': %s" % (args.cacert, str(e)))
+    elif not isempty(args.capath):
+        args.sslcontext.load_verify_locations(capath=args.capath)
+
     # We should now be ready to authenticate, fail if that's not the case
     if args.func == Password:
         if isempty(args.login) and isempty(args.serial) \
@@ -336,7 +359,7 @@ def parse_args():
     return args
 
 
-def checkotp(url, subject, secret, isserial=False, nas=None):
+def checkotp(url, subject, secret, isserial=False, nas=None, sslcontext=create_default_SSL_context()):
     """Check a subject (user or token) with secret against PrivacyIDEA / LinOTP.
 
     Args:
@@ -363,7 +386,9 @@ def checkotp(url, subject, secret, isserial=False, nas=None):
             v if k!='pass' else '***MASKED***') for k,v in params.iteritems()]))
 
      # Perform the API authentication request
-    response = json.load(urlopen(Request(url, data=urlencode(params))))
+    response = json.load(urlopen(Request(url, data=urlencode(params),
+                                         headers={'User-Agent':HTTP_AGENT}),
+                                 context=sslcontext))
     if logger.isEnabledFor(logging.DEBUG):
         logger.debug('result: %s', json.dumps(response, indent=4))
 
@@ -407,10 +432,10 @@ if __name__ == '__main__':
         response=checkotp(args.url,
                           args.login if isempty(args.serial) else args.serial,
                           secret, isserial=not isempty(args.serial),
-                          nas=args.name)
+                          nas=args.name, sslcontext=args.sslcontext)
         endtime = time()
 
-    except (HTTPError, URLError) as e:
+    except (HTTPError, URLError, CertificateError) as e:
         nagios_exit(NAGIOS_CRITICAL,'%s request failed: %s' % (message, e))
 
     except (KeyboardInterrupt, EOFError) as e:
@@ -478,3 +503,4 @@ if __name__ == '__main__':
 
     nagios_exit(nagiosresult, message, [
                   ('time', [ elapse, args.warn, args.critical, 0, None ])])
+