esgd/esgd.py

import socketserver
import subprocess
import os

class GopherError(BaseException): pass
class RequestError(GopherError): pass

def recieveRequest(context):
    data = b""
    while data[-2:] != b"\r\n":
        data += context.request.recv(1)
    decoded = data[:-2].decode("utf-8")
    return decoded

def requestParser(request):
    if ".." in request: raise RequestError
    try:
        if request[0] == "/": request = request[1:]
    except IndexError: pass
    request = request.replace("?", "\t").split("\t")
    try: return (request[0], request[1])
    except IndexError: return (request[0], "")

def returnRelative(file):
    gph = False
    if file == "":
        ret = "gophermap"
        gph = True
    elif os.path.isdir(file):
        ret = file + "/gophermap"
        gph = True
    elif os.path.isfile(file): ret = file
    else: raise RequestError("unreachable state")
    return (ret, gph)

def fileSendable(file): return os.access(file, os.F_OK|os.R_OK)

def fileCGI(file):
    return os.access(file, os.F_OK|os.R_OK|os.X_OK)

def notFound(context):
    context.request.sendall(b"3error: file not found!\r\n.\r\n")

def invalid(context):
    context.request.sendall(b"3error: selector contains '..'!\r\n.\r\n")

def sendFile(file, context):
    with open(file, "r") as fd:
        sendFileArray(fd.readlines(), context)

def sendFileArray(arr, context):
    [context.request.sendall(
        (i.rstrip() + "\r\n").encode("utf-8")
    ) for i in arr]
    context.request.sendall(b".\r\n")

def cgi(file, query, context):
    env = {}
    env["QUERY_STRING"] = query
    env["SCRIPT_NAME"] = "/" + file
    env["REMOTE_ADDR"] = context.client_address[0]

    proc = subprocess.Popen(
        [os.getcwd() + "/" + file],
        stdout = subprocess.PIPE,
        env = env
    )

    try: out, err = proc.communicate(timeout=10)
    except TimeoutExpired:
        proc.kill()
        out, err = proc.communicate()

    return out.decode("utf-8").replace("\r", "").split("\n")

class gopherHandler(socketserver.BaseRequestHandler):
    def handle(self):
        decoded = recieveRequest(self)
        try:
            parsed = requestParser(decoded)
        except RequestError:
            invalid(self)
            return

        try: file = returnRelative(parsed[0])
        except RequestError:
            notFound(self)
            return
        if fileCGI(file[0]):
            sendFileArray(cgi(file[0], parsed[1], self), self)
        elif fileSendable(file[0]): sendFile(file[0], self)
        else: notFound(self)

if __name__ == "__main__":
    HOST, PORT = "localhost", 70

    with socketserver.TCPServer((HOST, PORT), gopherHandler) as server:
        server.serve_forever()