Have anyone implemented NEDNSProxyManager before? - ios

I tried to use the NEDNSProxyManager to redirect the dns to my own server but failed to do that.
It should be able to do that as based on Apple Documentation
A DNS proxy allows your app to intercept all DNS traffic generated on a device. You can use this capability to provide services like DNS traffic encryption, typically by redirecting DNS traffic to your own server. You usually do this in the context of managed devices, such as those owned by a school or an enterprise.
Any help is much appreciated.

Related

Figuring out to set up HTTPS

I'm a relatively new programmer to backend security so very much in the dark about how to set up HTTPS. I'm currently writing an IOS app that is sending http requests to my public EC2 backend domain, however I'm trying to transition this to HTTPS. Right now the backend is running on the developmental Flask server using HTTPS with a self signed certificate. However the problem is that on the IOS app side, it rejects this as invalid so I'm unable to test HTTPS dependant features. I tried to use the domain exception with the infoplist and ip.xip.io but it still complains that someone could be pretending to be this address. Could someone list in a very systematic way how I should approach building this out,i.e are there any free CA's, do I need a cert from a CA, and how to go about properly connecting the app and backend with HTTPS using my ec2 public ip.
Perhaps the iOS app will authenticate properly using a free community certificate. Investigate free certificate authorities, like letsencrypt. There are several. These work like the commercial CAs such as GoDaddy.
Actually the easiest solution was to just use Ngrok

Azure Application Gateway exit IPs

We're looking to use Application Gateway as a frontend\proxy for a website we host onsite. The website has a public IP but we'd like to restrict access to the site to only traffic coming from the Application Gateway. Is there a way to determine what IP the traffic would be coming from as it exits Azure? Is it like other Azure traffic where it could come from any IP subnet they have assigned to that specific region? I haven't seen this question asked and it's not directly referenced in any of MS documentation that I can find.
Thanks!
Not sure why you want to restrict access to the site to only traffic coming from the Application Gateway because if you configure it and add the website in the backend of Application Gateway. The traffic from a client will always reach the website through the Application gateway as the Application Gateway works as an application proxy by accepting traffic and based on rules that are defined with it, routes the traffic to the appropriate back-end instances.
You may want to know to restrict access on the application gateway subnet via NSG. Then the inbound or outbound traffic in the Application Gateway subnet will be filtered via NSG.
Network Security Groups (NSGs) are supported on the application
gateway subnet with the following restrictions:
Exceptions must be put in for incoming traffic on ports 65503-65534
for the Application Gateway v1 SKU and ports 65200 - 65535 for the v2
SKU. This port-range is required for Azure infrastructure
communication. They are protected (locked down) by Azure certificates.
Without proper certificates, external entities, including the
customers of those gateways, will not be able to initiate any changes
on those endpoints.
Outbound internet connectivity can't be blocked.
Traffic from the AzureLoadBalancer tag must be allowed.
Hope this will help, let me know if you have any other concerns.
Update
If you just want to whitelist the Azure service on the firewall, you can read the Azure Datacenter IP Ranges. You can figure out which datacenters your service are located in then narrow down the IP ranges.

iOS app that communicates with server by IP not domain

Is it mandatory by Apple to use the domain name of my application server, or can I just use the IP address? Is my app going to be rejected by Apple, if I don't use a domain?
ATS protection does not apply for resources loaded via IP address, assuming you are loading over HTTP. Attempting HTTPS will throw an exception (As HTTPS by design requires a domain and an accompanying certificate)

How can a client app using HTTPS be tested for protection against a MITMA?

I have an iOS client app which connects to a server using HTTPS.
I've added code in the client to verify the identify of the server.
How can a tester testing this feature test that it is now secure, how can they for example create a MITM situation and check that the client rejects connects etc.?
I've tried googling for how to do this but haven't had much luck.
Can it be done using tools like Charles and proxies etc. or is messing around with a wireless router and having detailed knowledge necessary?
This might be over simplification for your solution, but concepts might help.
A web browsers extracts the name of hosts from embedded certificate and do a comparison of host name that we're trying to connect with. If validation fails, we usually see a security warning. For ex: we can connect with facebook by either typing https://www.facebook.com or by typing https://173.252.100.16/. When we choose second option, we get a security warning.
Your program must be using SSL client socket to connect with HTTPS server. The socket must be having capability to extract the hostname from the embedded certificate. Once you get that, compare that with valid HOST NAME that your program is trying to connect with. If it matches, let request proceed, If not, abandon that session.
To re-create MITM, your web server can use a self signed certificate that can be issue to whatever host name you want, but the IP of server could be 127.0.0.1 (for example). Since there is a mismatch between the host name and actual IP, we can probably simulate the MITM situation.
I'm assuming that digital certificate can't be forged in this case.

Custom domains in a Rails App

I want users of my service to be able to add their own custom domains. For example, www.[their domain].com should be able to access their application's index and show pages. My service is implemented in Rails 3.
I've seen apps like Tumblr offer this functionality for their front facing blogs. Although I have seen apps for Rails that implement sub domains in the way that Basecamp does, I have not found a resource for fully custom domains.
They'll need to create an A record in their DNS to point to your app servers IP. You'll need to know what domain they have pointed to your server and log it against their account, and also set your web servers config in such a way as to channel the requests from other domains to your app. You can then use the request object to look up their account in your application_controller.
I just answered a similar question so I decided to chime in here too.
#Codebeef gave a good answer but this won't work anymore in the world where HTTPS is a must in most modern browsers.
This is the full picture of how to handle custom domains for your app.
If your customers just CNAME to your domain or create the A record to your IP and you don't handle TLS termination for these custom domains, your app will not support HTTPS, and without it, your app won't work in modern browsers on these custom domains.
You need to set up a TLS termination reverse proxy in front of your webserver. This proxy can be run on a separate machine but you can run it on the same machine as the webserver.
CNAME vs A record
If your customers want to have your app on their subdomain, e.g. app.customer.com they can create a CNAME app.customer.com pointing to your proxy.
If they want to have your app on their root domain, e.g. customer.com then they'll have to create an A record on customer.com pointing to your proxy's IP. Make sure this IP doesn't change, ever!
How to handle TLS termination?
To make TLS termination work, you'll have to issue TLS certificates for these custom domains. You can use Let's Encrypt for that. Your proxy will see the Host header of the incoming request, e.g. app.customer1.com or customer2.com etc., and then it will decide which TLS certificate to use by checking the SNI.
The proxy can be set up to automatically issue and renew certificates for these custom domains. On the first request from a new custom domain, the proxy will see it doesn't have the appropriate certificate. It will ask Let's Encrypt for a new certificate. Let's Encrypt will first issue a challenge to see if you manage the domain, and since the customer already created a CNAME or A record pointing to your proxy, that tells Let's Encrypt you indeed manage the domain, and it will let you issue a certificate for it.
To issue and renew certificates automatically, I'd recommend using Caddyserver, greenlock.js, OpenResty (Nginx).
tl;dr on what happens here;
Caddyserver listens on 443 and 80, it receives requests, issues, and renews certificates automatically, proxies traffic to your backend.
How to handle it on my backend
Your proxy is terminating TLS and proxying requests to your backend. However, your backend doesn't know who is the original customer behind the request. This is why you need to tell your proxy to include additional headers in proxied requests to identify the customer. Just add X-Serve-For: app.customer.com or X-Serve-For: customer2.com or whatever the Host header is of the original request.
Now when you receive the proxied request on the backend, you can read this custom header and you know who is the customer behind the request. You can implement your logic based on that, show data belonging to this customer, etc.
More
Put a load balancer in front of your fleet of proxies for higher availability. You'll also have to use distributed storage for certificates and Let's Encrypt challenges. Use AWS ECS or EBS for automated recovery if something fails, otherwise, you may be waking up in the middle of the night restarting machines, or your proxy manually.
If you need more detail you can DM me on Twitter #dragocrnjac

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