Preliminary I2P Interface support

RNS/vendor/i2plib/__init__.py

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+"""
+A modern asynchronous library for building I2P applications. 
+"""
+
+from .__version__ import (
+    __title__, __description__, __url__, __version__,
+    __author__, __author_email__, __license__, __copyright__
+)
+
+from .sam import Destination, PrivateKey
+
+from .aiosam import (
+    get_sam_socket, dest_lookup, new_destination, 
+    create_session, stream_connect, stream_accept,
+    Session, StreamConnection, StreamAcceptor
+)
+
+from .tunnel import ClientTunnel, ServerTunnel
+
+from .utils import get_sam_address
+
+from .exceptions import (
+     CantReachPeer, DuplicatedDest, DuplicatedId, I2PError,
+     InvalidId, InvalidKey, KeyNotFound, PeerNotFound, Timeout,
+)

RNS/vendor/i2plib/__version__.py

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+__title__ = 'i2plib'
+__description__ = 'A modern asynchronous library for building I2P applications.'
+__url__ = 'https://github.com/l-n-s/i2plib'
+__version__ = '0.0.14'
+__author__ = 'Viktor Villainov'
+__author_email__ = 'supervillain@riseup.net'
+__license__ = 'MIT'
+__copyright__ = 'Copyright 2018 Viktor Villainov'

RNS/vendor/i2plib/aiosam.py

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+import asyncio
+
+from . import sam
+from . import exceptions
+from . import utils
+from .log import logger
+
+def parse_reply(data):
+    if not data:
+        raise ConnectionAbortedError("Empty response: SAM API went offline")
+
+    try:
+        msg = sam.Message(data.decode().strip())
+        logger.debug("SAM reply: "+str(msg))
+    except:
+        raise ConnectionAbortedError("Invalid SAM response")
+
+    return msg
+
+
+async def get_sam_socket(sam_address=sam.DEFAULT_ADDRESS, loop=None):
+    """A couroutine used to create a new SAM socket.
+
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) event loop instance
+    :return: A (reader, writer) pair
+    """
+    reader, writer = await asyncio.open_connection(*sam_address, loop=loop)
+    writer.write(sam.hello("3.1", "3.1"))
+    reply = parse_reply(await reader.readline())
+    if reply.ok:
+        return (reader, writer)
+    else:
+        writer.close()
+        raise exceptions.SAM_EXCEPTIONS[reply["RESULT"]]()
+
+async def dest_lookup(domain, sam_address=sam.DEFAULT_ADDRESS, 
+                      loop=None):
+    """A coroutine used to lookup a full I2P destination by .i2p domain or 
+    .b32.i2p address.
+
+    :param domain: Address to be resolved, can be a .i2p domain or a .b32.i2p 
+                   address.
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :return: An instance of :class:`Destination`
+    """
+    reader, writer = await get_sam_socket(sam_address, loop)
+    writer.write(sam.naming_lookup(domain))
+    reply = parse_reply(await reader.readline())
+    writer.close()
+    if reply.ok:
+        return sam.Destination(reply["VALUE"])
+    else:
+        raise exceptions.SAM_EXCEPTIONS[reply["RESULT"]]()
+
+async def new_destination(sam_address=sam.DEFAULT_ADDRESS, loop=None,
+                      sig_type=sam.Destination.default_sig_type):
+    """A coroutine used to generate a new destination with a private key of a 
+    chosen signature type.
+
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :param sig_type: (optional) Signature type
+    :return: An instance of :class:`Destination`
+    """
+    reader, writer = await get_sam_socket(sam_address, loop)
+    writer.write(sam.dest_generate(sig_type))
+    reply = parse_reply(await reader.readline())
+    writer.close()
+    return sam.Destination(reply["PRIV"], has_private_key=True)
+
+async def create_session(session_name, sam_address=sam.DEFAULT_ADDRESS, 
+                         loop=None, style="STREAM",
+                         signature_type=sam.Destination.default_sig_type,
+                         destination=None, options={}):
+    """A coroutine used to create a new SAM session.
+
+    :param session_name: Session nick name
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :param style: (optional) Session style, can be STREAM, DATAGRAM, RAW
+    :param signature_type: (optional) If the destination is TRANSIENT, this 
+                        signature type is used
+    :param destination: (optional) Destination to use in this session. Can be 
+                        a base64 encoded string, :class:`Destination` 
+                        instance or None. TRANSIENT destination is used when it
+                        is None.
+    :param options: (optional) A dict object with i2cp options
+    :return: A (reader, writer) pair
+    """
+    logger.debug("Creating session {}".format(session_name))
+    if destination:
+        if type(destination) == sam.Destination:
+            destination = destination
+        else:
+            destination = sam.Destination(
+                    destination, has_private_key=True)
+
+        dest_string = destination.private_key.base64
+    else:
+        dest_string = sam.TRANSIENT_DESTINATION
+
+    options = " ".join(["{}={}".format(k, v) for k, v in options.items()])
+
+    reader, writer = await get_sam_socket(sam_address, loop)
+    writer.write(sam.session_create(
+            style, session_name, dest_string, options))
+
+    reply = parse_reply(await reader.readline())
+    if reply.ok:
+        if not destination:
+            destination = sam.Destination(
+                    reply["DESTINATION"], has_private_key=True) 
+        logger.debug(destination.base32)
+        logger.debug("Session created {}".format(session_name))
+        return (reader, writer)
+    else:
+        writer.close()
+        raise exceptions.SAM_EXCEPTIONS[reply["RESULT"]]()
+
+async def stream_connect(session_name, destination, 
+                         sam_address=sam.DEFAULT_ADDRESS, loop=None):
+    """A coroutine used to connect to a remote I2P destination.
+
+    :param session_name: Session nick name
+    :param destination: I2P destination to connect to
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :return: A (reader, writer) pair
+    """
+    logger.debug("Connecting stream {}".format(session_name))
+    if isinstance(destination, str) and not destination.endswith(".i2p"):
+        destination = sam.Destination(destination)
+    elif isinstance(destination, str):
+        destination = await dest_lookup(destination, sam_address, loop)
+
+    reader, writer = await get_sam_socket(sam_address, loop)
+    writer.write(sam.stream_connect(session_name, destination.base64,
+                                           silent="false"))
+    reply = parse_reply(await reader.readline())
+    if reply.ok:
+        logger.debug("Stream connected {}".format(session_name))
+        return (reader, writer)
+    else:
+        writer.close()
+        raise exceptions.SAM_EXCEPTIONS[reply["RESULT"]]()
+
+async def stream_accept(session_name, sam_address=sam.DEFAULT_ADDRESS,
+                        loop=None):
+    """A coroutine used to accept a connection from the I2P network.
+
+    :param session_name: Session nick name
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :return: A (reader, writer) pair
+    """
+    reader, writer = await get_sam_socket(sam_address, loop)
+    writer.write(sam.stream_accept(session_name, silent="false"))
+    reply = parse_reply(await reader.readline())
+    if reply.ok:
+        return (reader, writer)
+    else:
+        writer.close()
+        raise exceptions.SAM_EXCEPTIONS[reply["RESULT"]]()
+
+### Context managers
+
+class Session:
+    """Async SAM session context manager.
+
+    :param session_name: Session nick name
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :param style: (optional) Session style, can be STREAM, DATAGRAM, RAW
+    :param signature_type: (optional) If the destination is TRANSIENT, this 
+                        signature type is used
+    :param destination: (optional) Destination to use in this session. Can be 
+                        a base64 encoded string, :class:`Destination` 
+                        instance or None. TRANSIENT destination is used when it
+                        is None.
+    :param options: (optional) A dict object with i2cp options
+    :return: :class:`Session` object
+    """
+    def __init__(self, session_name, sam_address=sam.DEFAULT_ADDRESS, 
+                         loop=None, style="STREAM",
+                         signature_type=sam.Destination.default_sig_type,
+                         destination=None, options={}):
+        self.session_name = session_name
+        self.sam_address = sam_address
+        self.loop = loop
+        self.style = style
+        self.signature_type = signature_type
+        self.destination = destination
+        self.options = options
+
+    async def __aenter__(self):
+        self.reader, self.writer = await create_session(self.session_name, 
+                sam_address=self.sam_address, loop=self.loop, style=self.style, 
+                signature_type=self.signature_type, 
+                destination=self.destination, options=self.options)
+        return self
+
+    async def __aexit__(self, exc_type, exc, tb):
+        ### TODO handle exceptions
+        self.writer.close()
+
+class StreamConnection:
+    """Async stream connection context manager.
+
+    :param session_name: Session nick name
+    :param destination: I2P destination to connect to
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :return: :class:`StreamConnection` object
+    """
+    def __init__(self, session_name, destination, 
+                 sam_address=sam.DEFAULT_ADDRESS, loop=None):
+        self.session_name = session_name
+        self.sam_address = sam_address
+        self.loop = loop
+        self.destination = destination
+
+    async def __aenter__(self):
+        self.reader, self.writer = await stream_connect(self.session_name, 
+                self.destination, sam_address=self.sam_address, loop=self.loop)
+        self.read = self.reader.read
+        self.write = self.writer.write
+        return self
+
+    async def __aexit__(self, exc_type, exc, tb):
+        ### TODO handle exceptions
+        self.writer.close()
+
+class StreamAcceptor:
+    """Async stream acceptor context manager.
+
+    :param session_name: Session nick name
+    :param sam_address: (optional) SAM API address
+    :param loop: (optional) Event loop instance
+    :return: :class:`StreamAcceptor` object
+    """
+    def __init__(self, session_name, sam_address=sam.DEFAULT_ADDRESS, 
+                 loop=None):
+        self.session_name = session_name
+        self.sam_address = sam_address
+        self.loop = loop
+
+    async def __aenter__(self):
+        self.reader, self.writer = await stream_accept(self.session_name, 
+                        sam_address=self.sam_address, loop=self.loop)
+        self.read = self.reader.read
+        self.write = self.writer.write
+        return self
+
+    async def __aexit__(self, exc_type, exc, tb):
+        ### TODO handle exceptions
+        self.writer.close()

RNS/vendor/i2plib/exceptions.py

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+# SAM exceptions
+
+class SAMException(IOError):
+    """Base class for SAM exceptions"""
+
+class CantReachPeer(SAMException):
+    """The peer exists, but cannot be reached"""
+
+class DuplicatedDest(SAMException):
+    """The specified Destination is already in use"""
+
+class DuplicatedId(SAMException):
+    """The nickname is already associated with a session"""
+
+class I2PError(SAMException):
+    """A generic I2P error"""
+
+class InvalidId(SAMException):
+    """STREAM SESSION ID doesn't exist"""
+
+class InvalidKey(SAMException):
+    """The specified key is not valid (bad format, etc.)"""
+
+class KeyNotFound(SAMException):
+    """The naming system can't resolve the given name"""
+
+class PeerNotFound(SAMException):
+    """The peer cannot be found on the network"""
+
+class Timeout(SAMException):
+    """The peer cannot be found on the network"""
+
+SAM_EXCEPTIONS = {
+    "CANT_REACH_PEER": CantReachPeer,
+    "DUPLICATED_DEST": DuplicatedDest,
+    "DUPLICATED_ID": DuplicatedId,
+    "I2P_ERROR": I2PError,
+    "INVALID_ID": InvalidId,
+    "INVALID_KEY": InvalidKey,
+    "KEY_NOT_FOUND": KeyNotFound,
+    "PEER_NOT_FOUND": PeerNotFound,
+    "TIMEOUT": Timeout,
+}
+

RNS/vendor/i2plib/log.py

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+"""Logging configuration."""
+import logging
+
+# Name the logger after the package.
+logger = logging.getLogger(__package__)

RNS/vendor/i2plib/sam.py

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+from base64 import b64decode, b64encode, b32encode
+from hashlib import sha256
+import struct
+import re
+
+
+I2P_B64_CHARS = "-~"
+
+def i2p_b64encode(x):
+    """Encode I2P destination"""
+    return b64encode(x, altchars=I2P_B64_CHARS.encode()).decode() 
+
+def i2p_b64decode(x):
+    """Decode I2P destination"""
+    return b64decode(x, altchars=I2P_B64_CHARS, validate=True)
+
+SAM_BUFSIZE = 4096
+DEFAULT_ADDRESS = ("127.0.0.1", 7656)
+DEFAULT_MIN_VER = "3.1"
+DEFAULT_MAX_VER = "3.1"
+TRANSIENT_DESTINATION = "TRANSIENT"
+
+VALID_BASE32_ADDRESS = re.compile(r"^([a-zA-Z0-9]{52}).b32.i2p$")
+VALID_BASE64_ADDRESS = re.compile(r"^([a-zA-Z0-9-~=]{516,528})$")
+
+class Message(object):
+    """Parse SAM message to an object"""
+    def __init__(self, s):
+        self.opts = {}
+        if type(s) != str:
+            self._reply_string = s.decode().strip()
+        else:
+            self._reply_string = s
+
+        self.cmd, self.action, opts = self._reply_string.split(" ", 2)
+        for v in opts.split(" "):
+            data = v.split("=", 1) if "=" in v else (v, True)
+            self.opts[data[0]] = data[1]
+
+    def __getitem__(self, key):
+        return self.opts[key]
+
+    @property
+    def ok(self):
+        return self["RESULT"] == "OK"
+
+    def __repr__(self):
+        return self._reply_string
+
+
+# SAM request messages
+
+def hello(min_version, max_version):
+    return "HELLO VERSION MIN={} MAX={}\n".format(min_version, 
+            max_version).encode()
+
+def session_create(style, session_id, destination, options=""):
+    return "SESSION CREATE STYLE={} ID={} DESTINATION={} {}\n".format(
+            style, session_id, destination, options).encode()
+
+
+def stream_connect(session_id, destination, silent="false"):
+    return "STREAM CONNECT ID={} DESTINATION={} SILENT={}\n".format(
+            session_id, destination, silent).encode()
+
+def stream_accept(session_id, silent="false"):
+    return "STREAM ACCEPT ID={} SILENT={}\n".format(session_id, silent).encode()
+
+def stream_forward(session_id, port, options=""):
+    return "STREAM FORWARD ID={} PORT={} {}\n".format(
+            session_id, port, options).encode()
+
+
+
+def naming_lookup(name):
+    return "NAMING LOOKUP NAME={}\n".format(name).encode()
+
+def dest_generate(signature_type):
+    return "DEST GENERATE SIGNATURE_TYPE={}\n".format(signature_type).encode()
+
+class Destination(object):
+    """I2P destination
+
+    https://geti2p.net/spec/common-structures#destination
+
+    :param data: (optional) Base64 encoded data or binary data 
+    :param path: (optional) A path to a file with binary data 
+    :param has_private_key: (optional) Does data have a private key? 
+    """
+
+    ECDSA_SHA256_P256 = 1
+    ECDSA_SHA384_P384 = 2
+    ECDSA_SHA512_P521 = 3
+    EdDSA_SHA512_Ed25519 = 7
+
+    default_sig_type = EdDSA_SHA512_Ed25519
+
+    _pubkey_size = 256
+    _signkey_size = 128
+    _min_cert_size = 3
+
+    def __init__(self, data=None, path=None, has_private_key=False):
+        #: Binary destination
+        self.data = bytes() 
+        #: Base64 encoded destination
+        self.base64 = ""    
+        #: :class:`RNS.vendor.i2plib.PrivateKey` instance or None
+        self.private_key = None    
+        
+        if path:
+            with open(path, "rb") as f: data = f.read()
+
+        if data and has_private_key:
+            self.private_key = PrivateKey(data)
+
+            cert_len = struct.unpack("!H", self.private_key.data[385:387])[0]
+            data = self.private_key.data[:387+cert_len]
+
+        if not data:
+            raise Exception("Can't create a destination with no data")
+
+        self.data = data if type(data) == bytes else i2p_b64decode(data)
+        self.base64 = data if type(data) == str else i2p_b64encode(data)
+
+    def __repr__(self):
+        return "<Destination: {}>".format(self.base32)
+
+    @property
+    def base32(self):
+        """Base32 destination hash of this destination"""
+        desthash = sha256(self.data).digest()
+        return b32encode(desthash).decode()[:52].lower()
+    
+class PrivateKey(object):
+    """I2P private key
+
+    https://geti2p.net/spec/common-structures#keysandcert
+
+    :param data: Base64 encoded data or binary data 
+    """
+
+    def __init__(self, data):
+        #: Binary private key
+        self.data = data if type(data) == bytes else i2p_b64decode(data)
+        #: Base64 encoded private key
+        self.base64 = data if type(data) == str else i2p_b64encode(data)
+

RNS/vendor/i2plib/tunnel.py

@@ -0,0 +1,203 @@
+import logging
+import asyncio
+import argparse
+
+from . import sam 
+from . import aiosam
+from . import utils
+from .log import logger
+
+BUFFER_SIZE = 65536
+
+async def proxy_data(reader, writer):
+    """Proxy data from reader to writer"""
+    try:
+        while True:
+            data = await reader.read(BUFFER_SIZE)
+            if not data:
+                break
+            writer.write(data)
+    except Exception as e:
+        logger.debug('proxy_data_task exception {}'.format(e))
+    finally:
+        try:
+            writer.close()
+        except RuntimeError:
+            pass
+        logger.debug('close connection')
+
+class I2PTunnel(object):
+    """Base I2P Tunnel object, not to be used directly
+
+    :param local_address: A local address to use for a tunnel. 
+                          E.g. ("127.0.0.1", 6668)
+    :param destination: (optional) Destination to use for this tunnel. Can be 
+                        a base64 encoded string, :class:`Destination`
+                        instance or None. A new destination is created when it
+                        is None.
+    :param session_name: (optional) Session nick name. A new session nickname is
+                        generated if not specified.
+    :param options: (optional) A dict object with i2cp options
+    :param loop: (optional) Event loop instance
+    :param sam_address: (optional) SAM API address
+    """
+
+    def __init__(self, local_address, destination=None, session_name=None, 
+                 options={}, loop=None, sam_address=sam.DEFAULT_ADDRESS):
+        self.local_address = local_address
+        self.destination = destination
+        self.session_name = session_name or utils.generate_session_id()
+        self.options = options
+        self.loop = loop
+        self.sam_address = sam_address
+
+    async def _pre_run(self):
+        if not self.destination:
+            self.destination = await aiosam.new_destination(
+                sam_address=self.sam_address, loop=self.loop)
+        _, self.session_writer = await aiosam.create_session(
+                self.session_name, style=self.style, options=self.options,
+                sam_address=self.sam_address, 
+                loop=self.loop, destination=self.destination)
+
+    def stop(self):
+        """Stop the tunnel"""
+        self.session_writer.close()
+
+class ClientTunnel(I2PTunnel):
+    """Client tunnel, a subclass of tunnel.I2PTunnel
+
+    If you run a client tunnel with a local address ("127.0.0.1", 6668) and
+    a remote destination "irc.echelon.i2p", all connections to 127.0.0.1:6668 
+    will be proxied to irc.echelon.i2p.
+
+    :param remote_destination: Remote I2P destination, can be either .i2p 
+                        domain, .b32.i2p address, base64 destination or 
+                        :class:`Destination` instance
+    """
+
+    def __init__(self, remote_destination, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.style = "STREAM"
+        self.remote_destination = remote_destination
+
+    async def run(self):
+        """A coroutine used to run the tunnel"""
+        await self._pre_run()
+
+        async def handle_client(client_reader, client_writer):
+            """Handle local client connection"""
+            remote_reader, remote_writer = await aiosam.stream_connect(
+                    self.session_name, self.remote_destination, 
+                    sam_address=self.sam_address, loop=self.loop)
+            asyncio.ensure_future(proxy_data(remote_reader, client_writer), 
+                                  loop=self.loop)
+            asyncio.ensure_future(proxy_data(client_reader, remote_writer),
+                                  loop=self.loop)
+
+        self.server = await asyncio.start_server(handle_client, *self.local_address, 
+                                         loop=self.loop)
+
+    def stop(self):
+        super().stop()
+        self.server.close()
+
+class ServerTunnel(I2PTunnel):
+    """Server tunnel, a subclass of tunnel.I2PTunnel
+
+    If you want to expose a local service 127.0.0.1:80 to the I2P network, run
+    a server tunnel with a local address ("127.0.0.1", 80). If you don't 
+    provide a private key or a session name, it will use a TRANSIENT 
+    destination.
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.style = "STREAM"
+
+    async def run(self):
+        """A coroutine used to run the tunnel"""
+        await self._pre_run()
+
+        async def handle_client(incoming, client_reader, client_writer):
+            # data and dest may come in one chunk
+            dest, data = incoming.split(b"\n", 1) 
+            remote_destination = sam.Destination(dest.decode())
+            logger.debug("{} client connected: {}.b32.i2p".format(
+                self.session_name, remote_destination.base32))
+
+            try:
+                remote_reader, remote_writer = await asyncio.wait_for(
+                        asyncio.open_connection(
+                           host=self.local_address[0], 
+                           port=self.local_address[1], loop=self.loop),
+                        timeout=5, loop=self.loop)
+                if data: remote_writer.write(data)
+                asyncio.ensure_future(proxy_data(remote_reader, client_writer),
+                                      loop=self.loop)
+                asyncio.ensure_future(proxy_data(client_reader, remote_writer),
+                                      loop=self.loop)
+            except ConnectionRefusedError:
+                client_writer.close()
+
+        async def server_loop():
+            try:
+                while True:
+                    client_reader, client_writer = await aiosam.stream_accept(
+                            self.session_name, sam_address=self.sam_address, 
+                            loop=self.loop)
+                    incoming = await client_reader.read(BUFFER_SIZE)
+                    asyncio.ensure_future(handle_client(
+                        incoming, client_reader, client_writer), loop=self.loop)
+            except asyncio.CancelledError:
+                pass
+
+        self.server_loop = asyncio.ensure_future(server_loop(), loop=self.loop)
+
+    def stop(self):
+        super().stop()
+        self.server_loop.cancel()
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument('type', metavar="TYPE", choices=('server', 'client'),
+                        help="Tunnel type (server or client)")
+    parser.add_argument('address', metavar="ADDRESS", 
+                        help="Local address (e.g. 127.0.0.1:8000)")
+    parser.add_argument('--debug', '-d', action='store_true',
+                        help='Debugging')
+    parser.add_argument('--key', '-k', default='', metavar='PRIVATE_KEY',
+                        help='Path to private key file')
+    parser.add_argument('--destination', '-D', default='', 
+                        metavar='DESTINATION', help='Remote destination')
+    args = parser.parse_args()
+
+    SAM_ADDRESS = utils.get_sam_address()
+
+    logging.basicConfig(level=logging.DEBUG if args.debug else logging.INFO)
+    loop = asyncio.get_event_loop()
+    loop.set_debug(args.debug)
+
+    if args.key:
+        destination = sam.Destination(path=args.key, has_private_key=True)
+    else:
+        destination = None
+
+    local_address = utils.address_from_string(args.address)
+
+    if args.type == "client":
+        tunnel = ClientTunnel(args.destination, local_address, loop=loop, 
+                destination=destination, sam_address=SAM_ADDRESS)
+    elif args.type == "server":
+        tunnel = ServerTunnel(local_address, loop=loop, destination=destination, 
+                sam_address=SAM_ADDRESS)
+
+    asyncio.ensure_future(tunnel.run(), loop=loop)
+
+    try:
+        loop.run_forever()
+    except KeyboardInterrupt:
+        tunnel.stop()
+    finally:
+        loop.stop()
+        loop.close()

RNS/vendor/i2plib/utils.py

@@ -0,0 +1,42 @@
+import socket
+import os
+import random
+import string
+
+from . import sam
+
+def get_free_port():
+    """Get a free port on your local host"""
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    s.bind(('', 0))
+    free_port = s.getsockname()[1]
+    s.close()
+    return free_port
+
+def is_address_accessible(address):
+    """Check if address is accessible or down"""
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    is_accessible = s.connect_ex(address) == 0
+    s.close()
+    return is_accessible
+
+def address_from_string(address_string):
+    """Address tuple from host:port string"""
+    address = address_string.split(":")
+    return (address[0], int(address[1]))
+
+def get_sam_address():
+    """
+    Get SAM address from environment variable I2P_SAM_ADDRESS, or use a default
+    value
+    """
+    value = os.getenv("I2P_SAM_ADDRESS")
+    return address_from_string(value) if value else sam.DEFAULT_ADDRESS
+
+def generate_session_id(length=6):
+    """Generate random session id"""
+    rand = random.SystemRandom()
+    sid = [rand.choice(string.ascii_letters) for _ in range(length)]
+    return "reticulum-" + "".join(sid)
+