The scenario is - I need to send push notification to Apple push server hosted at gateway.sandbox.push.apple.com. This Apple server is load balanced and the destination IP address can be anything in 17.x.x.x block.
Now my server which will be requesting Apple server is in secure environment and is behind firewalls. I have got the IP range 17.x.x.x unblocked, but DNS resolving is not possible on that server. That server also doesn't have Internet access on it.
What I did was - I pinged the Apple server from another system and got the Apple server's IP address for the moment. Then I mapped that IP address with the DNS name in the hosts file of my Windows server. This worked, but now the IP address can change anytime at the Apple end, and this will break things.
What can I do in this scenario?
You can talk to your security people and in cooperation with them come up with a proper, internally supported, way to provide what you need. What you need is to look up an address, and then talk to that address. Currently, you are only provided half of that.
What you're asking us for is a way to circumvent your own organization's security policies (policies that admittedly appear stupid, but that's another matter entirely). Even if someone here can come up with a technical way to do what you ask that works for now, it's likely to break at any time, since you're working at odds with your own workplace. Also, what will your bosses say if they find out that you're violating security policies?
Security very often comes down to tradeoffs. As the saying goes, the only truly secure system is one that has been encased in concrete and sunk to the bottom of the sea. But such a system will also be somewhat difficult to get useful work out of, so usually we accept lesser security in order to get work done. In your case, the tradeoff currently sits in a place that prevents you from doing whatever it is you're working on. So your organization needs to make a choice: change the tradeoff so that your machine can look up names, or keep the current tradeoff and accept that your task will not be done.
I'm sorry that I can't give you a straight up "Sure, do this" kind of answer, but your problem really is not technical.
I'm using Cloud Haskell for creating a quite simple client-server application (game, to be little more specific). It may be a little overhit, but their idea of processes and nodes seems nice and clear to me.
The application runs quite nice with their simplelocalnet, but I would like to use more than just local network. From what I have read about their idea of process/transport layer, it should be possible to use different topologies just on the 'backend' layer, not going down to network transport.
However, for now I have found just a few backend variations, except for simplelocalnetwork: backend for Azure, which is stated to be just a "Proof of concept", and for p2p. Good, but nothing of these two seems useful for my purpose.
The concept of application is: server "meets" clients (players), then starts the game with them. Server "plays" with each player independently, then showing the results of each one.
I hoped to find something like tcp-backend, so it would be like on local network, but over the internet (of course, clients know the IP adress of server). Still I found nothing.
Can anyone point me to the backend I could use (ideally working on TCP or UDP)? Or I have to go down to Network.Transport anyway? Or maybe you can suggest a different solution?
Thank you in advance - or just for reading this:)
Have a nice day.
I was trying to make a simple multiplayer (P2P) board game that connects players over the internet. So far, the only networking applications I've worked on only communicate with permanent web servers via HTTP.
After some preliminary reading, I learnt that most devices are subject to NAT nowadays, which makes P2P connections a pain to establish. I've read about 2 ways around the NAT hurdle:
Set up a central server to facilitate NAT punch-through.
Use Internet Gateway Device (from UPnP) to do automatic port-forwarding.
I haven't delved into the details yet, but it seems like NAT punch-through requires me to set up a permanent matchmaking server (for which I doubt is within my budget) and to administer it (which I have no experience in). UPnP seems like the way to go.
Would you say that my assessment is accurate? Are there any other options? Is there anything else I should take into account before designing/implementing my game?
(I'm planning to write my game using Qt, to support multiple platforms. Someone has made a Qt-based P2P file sharer using the MiniUPnPc library, so I'm thinking of studying that implementation)
One thing you can do to avoid the issue all together is just require your end user to make a local version of the app server and forward the ports themselves. Just give them an option to either "Create Game" or "Join Game", and if they create a game make them specify the port they want to run it on. Then it's their responsibility to make sure that port is open.
Having said that, I recently went through setting up a matchmaking style networked game using Unity3d and I can comment on setting up a matchmaking server within that framework.
There are 2 pieces to the process, the MasterServer and the Facilitator, where the MasterServer just holds all the game related information and the Facilitator handles incoming connections to the server.
Because the MasterServer/Facilitator are only handling connection information, they're fairly light processes and you can just run them in the background on your home machine if you don't mind leaving your machine on all the time.
It pretty much regulates itself once you have it up and running. It's not any more difficult than running a standard web server anyway.
I haven't explored using Internet Gateway Device to handle networking, but looking at the wiki for it (http://en.wikipedia.org/wiki/Internet_Gateway_Device_Protocol), it looks like it's just a magic thing to handle NAT punch through automatically. I have done little to no research on this method, but it looks like it might be something that has to be installed on the client end, which I feel like isn't what you want. If you find a way to make it work the way you want, let me know; I'd be curious to see it in action.
I'm developing a chat application (in VB.Net). It will be a "secure" chat program. All traffic will be encrypted (I also need to find the best approach for this, but that's not the question for now).
Currently the program works. I have a server application and a client application. However I want to setup the application so that it doesn't need a central server for it to work.
What approach can I take to decentralize the network?
I think I need to develop the clients in a way so that they do also act as a server.
How would the clients know what server it needs to connect with / what happens if a server is down? How would the clients / servers now what other nodes there are in the network without having a central server?
At best I don't want the clients to know what the IP addresses are of the different nodes, however I don't think this would be possible without having a central server.
As stated the application will be written in VB.Net, but I think the language doesn't really matter at this point.
Just want to know the different approaches I can follow.
Look for example at the paper of the Kademlia protocol (you can find it here). If you just want a quick overview, look at the Wikipedia page http://en.wikipedia.org/wiki/Kademlia. The Kademlia protocol defines a way of node lookups in a network in a decentral way. It has been successfully applied in the eMule software - so it is tested to really work.
It should cause no serious problems to apply it to your chat software.
You need some known IP address for clients to initially get into a network. Once a client is part of a network, things can be more decentralized, but that first step needs something.
There are basically only two options - either the user provides one (for an existing node of the network - essentially how BitTorrent trackers work), or you hard-code in a gateway node (which is effectively a central server).
Maybe you can see uChat program. It's a program from uTorrent creator with chat without server in mind.
The idea is connect to a swarm from a magnetlink and use it to send an receive messages. This is as Amber answer, you need an access point, may it be a server, a know swarm, manual ip, etc.
Here is uChat presentation: http://blog.bittorrent.com/2011/06/30/uchat-we-just-need-each-other/
I'm working on an external web site (in DMZ) that needs to get data from our internal production database.
All of the designs that I have come up with are rejected because the network department will not allow a connection of any sort (WCF, Oracle, etc.) to come inside from the DMZ.
The suggestions that have come from the networking side generally fall under two categories -
1) Export the required data to a server in the DMZ and export modified/inserted records eventually somehow, or
2) Poll from inside, continually asking a service in the DMZ whether it has any requests that need serviced.
I'm averse to suggestion 1 because I don't like the idea of a database sitting in the DMZ. Option 2 seems like a ridiculous amount of extra complication for the nature of what's being done.
Are these the only legitimate solutions? Is there an obvious solution I'm missing? Is the "No connections in from DMZ" decree practical?
Edit: One line I'm constantly hearing is that "no large company allows a web site to connect inside to get live production data. That's why they send confirmation emails". Is that really how it works?
I'm sorry, but your networking department are on crack or something like that - they clearly do not understand what the purpose of a DMZ is. To summarize - there are three "areas" - the big, bad outside world, your pure and virginal inside world, and the well known, trusted, safe DMZ.
The rules are:
Connections from outside can only get to hosts in the DMZ, and on specific ports (80, 443, etc);
Connections from the outside to the inside are blocked absolutely;
Connections from the inside to either the DMZ or the outside are fine and dandy;
Only hosts in the DMZ may establish connections to the inside, and again, only on well known and permitted ports.
Point four is the one they haven't grasped - the "no connections from the DMZ" policy is misguided.
Ask them "How does our email system work then?" I assume you have a corporate mail server, maybe exchange, and individuals have clients that connect to it. Ask them to explain how your corporate email, with access to internet email, works and is compliant with their policy.
Sorry, it doesn't really give you an answer.
I am a security architect at a fortune 50 financial firm. We had these same conversations. I don't agree with your network group. I understand their angst, and I understand that they would like a better solution but most places don't opt with the better choices (due to ignorance on their part [ie the network guys not you]).
Two options if they are hard set on this:
You can use a SQL proxy solution like greensql (I don't work for them, just know of them) they are just greensql dot com.
The approach they refer to that most "Large orgs" use is a tiered web model. Where you have a front end web server (accessed by the public at large), a mid-tier (application or services layer where the actual processes occurs), and a database tier. The mid-tier is the only thing that can talk to the database tier. In my opinion this model is optimal for most large orgs. BUT that being said, most large orgs will run into either a vendor provided product that does not support a middle tier, they developed without a middle tier and the transition requires development resources they dont have to spare to develop the mid-tier web services, or plain outright there is no priorty at some companies to go that route.
Its a gray area, no solid right or wrong in that regard, so if they are speaking in finality terms then they are clearly wrong. I applaud their zeal, as a security professional I understand where they are coming from. BUT, we have to enable to business to function securely. Thats the challange and the gauntlet I always try and throw down to myself. how can I deliver what my customer (my developers, my admins, my dbas, business users) what they want (within reason, and if I tell someone no I always try to offer an alternative that meets most of their needs).
Honestly it should be an open conversation. Here's where I think you can get some room, ask them to threat model the risk they are looking to mitigate. Ask them to offer alternative solutions that enable your web apps to function. If they are saying they cant talk, then put the onus on them to provide a solution. If they can't then you default to it working. Site that you open connections from the dmz to the db ONLY for the approved ports. Let them know that DMZ is for offering external services. External services are not good without internal data for anything more than potentially file transfer solutions.
Just my two cents, hope this comment helps. And try to be easy on my security brethren. We have some less experienced misguided in our flock that cling to some old ways of doing things. As the world evolves the threat evolves and so does our approach to mitigation.
Why don't you replicate your database servers? You can ensure that the connection is from the internal servers to the external servers and not the other way.
One way is to use the ms sync framework - you can build a simple windows service that can synchronize changes from internal database to your external database (which can reside on a separate db server) and then use that in your public facing website. Advantage is, your sync logic can filter out sensitive data and keep only things that are really necessary. And since the entire control of data will be in your internal servers (PUSH data out instead of pull) I dont think IT will have an issue with that.
The connection formed is never in - it is out - which means no ports need to be opened.
I'm mostly with Ken Ray on this; however, there appears to be some missing information. Let's see if I get this right:
You have a web application.
Part of that web application needs to display data from a different production server (not the one that normally backs your site).
The data you want/need is handled by a completely different application internally.
This data is critical to the normal flow of your business and only a limited set needs to be available to the outside world.
If I'm on track, then I would have to say that I agree with your IT department and I wouldn't let you directly access that server either.
Just take option 1. Have the production server export the data you need to a commonly accessible drop location. Have the other db server (one in the DMZ) pick up the data and import it on a regular basis. Finally, have your web app ONLY talk to the db server in the dmz.
Given how a lot of people build sites these days I would also be loath to just open a sql port from the dmz to the web server in question. Quite frankly I could be convinced to open the connection if I was assured that 1. you only used stored procs to access the data you need; 2. the account information used to access the database was encrypted and completely restricted to only running those procs; 3. those procs had zero dynamic sql and were limited to selects; 4. your code was built right.
A regular IT person would probably not be qualified to answer all of those questions. And if this database was from a third party, I would bet you might loose support if you were to start accessing it from outside it's normal application.
Before talking about your particular problem I want to deal with the Update that you provided.
I haven't worked for a "large" company - though large is hard to judge without a context, but I have built my share of web applications for the non profit and university department that I used to work for. In both situations I have always connected to the production DB that is on the internal Network from the Web server on the DMZ. I am pretty sure many large companies do this too; think for example of how Sharepoint's architecture is setup - back-end indexing, database, etc. servers, which are connected to by front facing web servers located in the DMZ.
Also the practice of sending confirmation e-mails, which I believe you are referring to confirmations when you register for a site don't usually deal with security. They are more a method to verify that a user has entered a valid e-mail address.
Now with that out of the way, let us look at your problem. Unfortunately, other than the two solutions you presented, I can't think of any other way to do this. Though some things that you might want to think about:
Solutions 1:
Depending on the sensitivity of the data that you need to work with, extracting it onto a server on the DMZ - whether using a service or some sort of automatic synchronization software - goes against basic security common sense. What you have done is move the data from a server behind a firewall to one that is in front of it. They might as well just let you get to the internal db server from the DMZ.
Solution 2:
I am no networking expert, so please correct me if I am wrong, but a polling mechanism still requires some sort of communication back from the web server to inform the database server that it needs some data back, which means a port needs to be open, and again you might as well tell them to let you get to the internal database without the hassle, because you haven't really added any additional security with this method.
So, I hope that this helps in at least providing you with some arguments to allow you to access the data directly. To me it seems like there are many misconceptions in your network department over how a secure database backed web application architecture should look like.
Here's what you could do... it's a bit of a stretch, but it should work...
Write a service that sits on the server in the DMZ. It will listen on three ports, A, B, and C (pick whatever port numbers make sense). I'll call this the DMZ tunnel app.
Write another service that lives anywhere on the internal network. It will connect to the DMZ tunnel app on port B. Once this connection is established, the DMZ tunnel app no longer needs to listen on port B. This is the "control connection".
When something connects to port A of the DMZ tunnel app, it will send a request over the control connection for a new DB/whatever connection. The internal tunnel app will respond by connecting to the internal resource. Once this connection is established, it will connect back to the DMZ tunnel app on port C.
After possibly verifying some tokens (this part is up to you) the DMZ tunnel app will then forward data back and forth between the connections it received on port A and C. You will effectively have a transparent TCP proxy created from two services running in the DMZ and on the internal network.
And, for the best part, once this is done you can explain what you did to your IT department and watch their faces as they realize that you did not violate the letter of their security policy, but you are still being productive. I tell you, they will hate that.
If all development solutions cannot be applied because of system engineering restriction in DMZ then give them the ball.
Put your website in intranet, and tell them 'Now I need inbound HTTP:80 or HTTPS:443 connections to that applications. Set up what you want : reverse proxies, ISA Server, protocols break, SSL... I will adapt my application if necessary.'
About ISA, I guess they got one if you have exchange with external connections.
Lot of companies are choosing this solution when a resource need to be shared between intranet and public.
Setting up a specific and intranet network with high security rules is the best way to make the administration, integration and deployment easier. What is easier is well known, what is known is masterized : less security breach.
More and more system enginers (like mines) prefer to maintain an intranet network with small 'security breach' like HTTP than to open other protocols and ports.
By the way, if they knew WCF services, they would have accepted this solution. This is the most secure solution if well designed.
Personnaly, I use this two methods : TCP(HTTP or not) Services and ISA Server.