dtls for python

dtls-client.py

# -*- coding: latin-1 -*-
#
# Copyright (C) AB Strakt
# Copyright (C) Jean-Paul Calderone
# See LICENSE for details.

"""
Simple SSL client, using blocking I/O
"""

from OpenSSL import SSL
import sys, os, select, socket

def verify_cb(conn, cert, errnum, depth, ok):
    # This obviously has to be updated
    print 'Got certificate: %s' % cert.get_subject()
    return ok

if len(sys.argv) < 3:
    print 'Usage: python[2] client.py HOST PORT'
    sys.exit(1)

dir = os.path.dirname(sys.argv[0])
if dir == '':
    dir = os.curdir

# Initialize context
ctx = SSL.Context(SSL.DTLSv1_METHOD)
ctx.set_verify(SSL.VERIFY_PEER, verify_cb) # Demand a certificate
ctx.use_privatekey_file (os.path.join(dir, 'client.pkey'))
ctx.use_certificate_file(os.path.join(dir, 'client.cert'))
ctx.load_verify_locations(os.path.join(dir, 'CA.cert'))

# Set up client
sock = SSL.Connection(ctx, socket.socket(socket.AF_INET, socket.SOCK_DGRAM))
addr = (sys.argv[1], int(sys.argv[2]))
sock.connect(addr)

while 1:
    line = sys.stdin.readline()
    if line == '':
        break
    try:
        sock.sendto(line, addr)
        print 'received', sock.recvfrom(1024)
        sys.stdout.flush()
    except SSL.Error as e:
        print e
        print 'Connection died unexpectedly'
        break


sock.shutdown()
sock.close()

dtls-server.py

# -*- coding: latin-1 -*-
#
# Copyright (C) AB Strakt
# Copyright (C) Jean-Paul Calderone
# See LICENSE for details.

"""
Simple echo server, using nonblocking I/O
"""

from OpenSSL import SSL
import sys, os, select, socket


def verify_cb(conn, cert, errnum, depth, ok):
    # This obviously has to be updated
    print 'Got certificate: %s' % cert.get_subject()
    return ok

if len(sys.argv) < 2:
    print 'Usage: python[2] server.py PORT'
    sys.exit(1)

dir = os.path.dirname(sys.argv[0])
if dir == '':
    dir = os.curdir

# Initialize context
ctx = SSL.Context(SSL.DTLSv1_METHOD)
ctx.set_options(SSL.OP_NO_SSLv2)
ctx.set_verify(SSL.VERIFY_PEER|SSL.VERIFY_FAIL_IF_NO_PEER_CERT, verify_cb) # Demand a certificate
ctx.use_privatekey_file (os.path.join(dir, 'server.pkey'))
ctx.use_certificate_file(os.path.join(dir, 'server.cert'))
ctx.load_verify_locations(os.path.join(dir, 'CA.cert'))

# Set up server
server = SSL.Connection(ctx, socket.socket(socket.AF_INET, socket.SOCK_DGRAM))
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server.bind(('', int(sys.argv[1])))
#server.listen(3) 
server.setblocking(0)

clients = {}
writers = {}

def dropClient(cli, errors=None):
    if errors:
        print 'Client %s left unexpectedly:' % (clients[cli],)
        print '  ', errors
    else:
        print 'Client %s left politely' % (clients[cli],)
    del clients[cli]
    if writers.has_key(cli):
        del writers[cli]
    if not errors:
        cli.shutdown()
    cli.close()

while 1:
    try:
        r,w,_ = select.select([server]+clients.keys(), writers.keys(), [])
    except:
        break

    for cli in r:
        print 'something happended', cli, cli==server
        try:
            #cli,addr = server.accept()
            ret, addr = server.recvfrom(1024)
            print 'Connection from %s' % (addr,)
            clients[cli] = addr

        except (SSL.WantReadError, SSL.WantWriteError, SSL.WantX509LookupError):
            pass
        except SSL.ZeroReturnError:
            dropClient(cli)
        except SSL.Error, errors:
            dropClient(cli, errors)
        except Exception as e:
            print e
            pass
        else:
            if not writers.has_key(cli):
                writers[cli] = ''
            print 'got', ret
            writers[cli] = writers[cli] + ret

    for cli, addr in clients.iteritems():
        try:
            print 'sending response', cli, addr
            ret = server.sendto(writers[cli], addr)
        except (SSL.WantReadError, SSL.WantWriteError, SSL.WantX509LookupError) as e:
            print e
            pass
        except SSL.ZeroReturnError:
            dropClient(cli)
        except SSL.Error, errors:
            dropClient(cli, errors)
        else:
            writers[cli] = writers[cli][ret:]
            if writers[cli] == '':
                del writers[cli]

for cli in clients.keys():
    cli.close()
server.close()

pyopenssl library do not support DTLSv1_METHOD. TLS only. (https://pyopenssl.org/en/stable/api/ssl.html)
Try this: rbit/pydtls#15 (comment)