In iOS MDM /server url will be called for each operation by the device when it is woken by APNS. I have securely encrypted and signed other profiles at the time of enrollment and successfully passed the server url to device. Its working fine but I have few concerns over this server endpoint as follows.
1) Any client or entity who could send similar plist payload can invoke this service. If a 3rd party has access to a device UDID they can compose this xml payload and invoke this service. From the server point of view it will be hard to track this behavior and identify real devices. To identify that in the real scenario will it send and CMS data or related to validate this scenario?
2) Once the device hit this endpoint from server we can generate operation profiles and send back to devices. For the profiles at the enrollment time we could extract the public certificate from CMS data and encrypt from that. But for this server url how do I achieve that? Seems its not getting any cert like that from device side. Just wondering whether to save the public keys we got in earlier stages but since at the enrollment it goes through 2 SCEP calls not sure what to use it. Will those subsequent profiles payload can be encrypted using previous public cert? Right now I do the signing anyway which works fine.
1.) Any client or entity who could send similar plist payload can invoke this service. If a 3rd party has access to a device UDID they can compose this xml payload and invoke this service. From the server point of view it will be hard to track this behavior and identify real devices. To identify that in the real scenario will it send and CMS data or related to validate this scenario?
Yes, Any client who could possess the UDID and Server URl can send a valid Plist to your server acting like the device.
But they cannot sign the plist with the private key in the device(Which is generated during SCEP enrolment). You would be having corresponding Public key for it to validate the signature.
To force the device to send the signature along each request to Server URL, you have to include SignMessage tag in your MDM payload and set it as true. Like this
<key>SignMessage</key>
<true/>
So when you include this tag along with your MDM payload, you would be get the signature of Identity Private key in the Header HTTP_MDM_SIGNATURE.
Then you can validate the signature using your public key.
2.) Just wondering whether to save the public keys we got in earlier stages but since at the enrollment it goes through 2 SCEP calls not sure what to use it.
Yes I mentioned in the previous answer you should save the public certificate which is issued during SCEP phase. Later you will use that public certificate to Validate the signature from Device and Encrypt the profile you are sending.
Regarding 2 SCEP calls, First SCEP call is to generate the certificate and securely transfer the MDM Payload and actual SCEP payload which will be used as Idenitity certificate for MDM.
So you should use the second one for validating the signature and encryption.
One more hint is, you would have mentioned IdentityCertificateUUID in your MDM payload. The Identity Certificate SCEP payload should have same UUID as its PayloadUUID . That SCEP payload's certificate will be used as the identity certificate for MDM.
Ok. The bottom line that you want to authenticate device.
Each device has an identity cert (a cert distributed in PKCS12 or through SCEP).
Each time when a device communicate to the server it does authentication using SSL client certs.
Most of the time there is a reverse proxy sitting upfront of your web server. It could be Apache or Nginx or anything else. This reverse proxy terminates SSL connection and checks client certificate. Usually, they are configured to pass this client certificate as a header to your web application.
This way your web app can get this header, get a certificate out of it and check against your DB whether a device with specific udid (passed to your endpoint) have a certificate (passed to your webapp in the header).
I am not sure which reverse do you use and whether it's configured properly to pass the certificate.
Related
I'm reading this article on iOS push certificates, and I'm confused about this paragraph:
Your backend sends notifications through Apple's servers to your application. To ensure that unwanted parties are not sending notifications to your application, Apple needs to know that only your servers can connect with theirs. Apple therefore requires you to create an SSL certificate to be able to send push notifications.
My understanding of SSL certificates is that if a server has one, that server is able to encrypt data that it sends to a device. But it says here Apple needs to know that only your servers can connect with theirs. I don't understand how having an SSL certificate ensures that. Does anyone have any insight?
The article shouldn't have used the term SSL Certificate. SSL is the Secure Sockets Layer (which was superseded by TLS many years ago). SSL and TLS define the handshake that is used to negotiate encryption on a connection.
Enabling SSL on a web server required you to have a certificate to verify your server's identity and so this became known colloquially as an "SSL certificate".
While it isn't often used on the web, in SSL/TLS both parties can present a certificate so that there is mutual authentication.
What you typically have is actually an x.509 certificate. This is the case with the push notification service.
An x.509 certificate contains some information including the identity of the certificate holder, their private key and a signature from a trusted party that can be used to verify the information.
For push notifications, the developer generates a certificate request and submits this to Apple who sign it with their private key. Apple is the trusted party in this case.
When this certificate is subsequently presented to Apple's server they can verify that signature using their public key to confirm the identity of the connecting party.
You have has encrypted the message with their private key (Apple can decrypt it with the public key included in the certificate).
What this means is, that as long as the developer has kept their private key secure (which is why you wouldn't connect directly to the push service from your app, for example) then Apple can be sure of the identity of the server making the connection.
If someone was trying to impersonate your server then, as long as you have kept your private key secure, they can't encrypt the data properly. If they use a forged certificate that uses a public/private key pair known to them then the signature on the certificate won't be valid and Apple will reject it.
TL;DR version: Is there any way to pass a Server certificate to an iOS client that doesn't involve also passing along the Server's private key?
I have written an iOS client app that communicates with my macOS server app (so I have control over both ends). I have implemented certificate pinning using a self-signed certificate to make things more secure. To accomplish this during development, I hardcoded the Server cert into the iOS client app and told the client to only connect to a server that gives you that exact cert during the TLS handshake. Everything is working great.
However in the real world I am selling this system as a set (1 Server, multiple clients to each customer), so I cannot hardcode a Server cert into the iOS client. My plan is to instead deliver the Server cert out of band (via email) to the iOS client like mentioned here: Making Certificates and Keys Available To Your App:
Apps can only access keychain items in their own keychain access groups.
To use digital identities in your own apps, you will need to write code to import them. This typically means reading in a PKCS#12-formatted blob and then importing the contents of the blob into the app's keychain using the function SecPKCS12Import
One way to provision an identity is via email. When you provision a device, send the associated user an email with their client identity attached as a PKCS#12 file.
My problem is that a .p12 file contains the certificate and the private key of the server - this seems very wrong to pass the private key along as well.
Is there any other way to pass the Server certificate to the iOS client that doesn't involve also passing along the Server's private key?
Thanks!!!
I was overthinking things here, the solution is actually pretty simple.
I just needed to email the Server's public certificate out of band to the client device with a custom extension like cert.myCustomExt1234. This is because the .crt extension is already claimed by iOS so you have to register your app to handle custom extensions (see apple docs here). Then in my app I can do all the logic of cert pinning using that out of band delivered Server public cert.
The key was changing the file extension to something not already claimed by iOS.
How can we retrieve identity certificates received from SCEP during enrollment in objective c.
I guess the certificates are stored in KeyChain Access of the device.
PS: I read somewhere that we cannot access other apps keychain via any 3rd party app, so is it possible to get the certificates stored during enrollment process of MDM
I think you can't access it. As you correctly mentioned, it's stored in keychain. And I believe in this case, it will be stored in keychain of Safari or mdmd. And you don't have access to either of those on your device (except, if it's jailbroken).
However, if Certificate authority in your control, potentially you can write server side code which will allow query certificate (not a private key) for your device. Your application will talk to your server and it will go to Certificate authority and get a certificate associated with your device.
I am developing mdm server and I have a problem with one of enrollment steps. The problem is scep step. I implement a scep server which handles Device CACert request and sends our server certificate in der format. After that, device sends encrypted and signed csr. But I can not verify signature of message. I think device creates a self-signed-certificate and sign message with it. We think that because signature certificate's common name is changing each "PKIOperation" request. But we must verify this signature because of security.
For example in each 3 enrollment request, certificate of csr signature changes. Their common names are:
CN=6E4F65AD-1E64-4E4D-A96E-2039EB140041
CN=2E33C2CC-14B8-47AC-938B-DCC7F8DA8715
CN=6817ED48-AB79-4FF0-A1A9-42C2AC303672
Note: The other steps of enrollment device sign messages with proper certificate and I can verify them. Only scep PKIOperation request is my problem. Is there any profile flag to set or something to solve this problem?
I may be wrong in some details, because I touched this about two years ago.
However, as I remember it's part of a protocol
If you take a look at SCEP draft: https://datatracker.ietf.org/doc/html/draft-nourse-scep-23#page-30 you will see this:
When building a pkiMessage, clients MUST have a certificate to sign
the PKCS#7 [RFC2315] signed-data (because PKCS#7 [RFC2315] requires
it). Clients MUST either use an existing certificate, or create a
self-signed certificate (see Section 2.3).
If the requester does not have an appropriate existing
certificate, then a locally generated self-signed certificate
MUST be used instead. The self-signed certificate MUST use the
same subject name as in the PKCS#10 request.
However, I was under impression that iOS device uses certificate/private keys which are built into the device. And this certificate is signed using Apple certs. And actually, as I remember they had exactly the format of CN, which you shown.
So, generally speaking it's ok if device uses self-signed certificate for first communication to the SCEP server (PKIOperation) and uses a certificate issued by your CA later on.
The Application i am working on needs to connect to a webservice over https, The certificate is trusted and valid.
I have used NSURLConnection is previous projects to use soap over http
Can anybody please point the difference between the two above mentioned scenarios,
I also need to understand what exactly happens when connecting over https, is the certificate stored automatically on the device, how does ssl handshake happen.
Any Pointers in this direction will be really helpful.
Regards,
Ishan
I need some clarification. Is the certificate signed by Apple for use with notifications or is it signed by an SSL root certificate authority (like VeriSign)?
Apple signed certificates are only to be used with WebServer to Apple Server communications like the Apple Push Notification Service. They are not intended for iOS device to WebServer.
A SSL certificate signed by a SSL root certificate authority should just work.
I think you are looking for an HTTP over SSL/TLS primer. So, here it goes.
HTTP is an unencrypted channel. The request and response are in a plain text data stream. HTTPS is an encrypted channel. The request and response are in a data stream encrypted using a shared master key. The magic of SSL/TLS is how this encrypted channel is created.
First, the client and server say hello to each other (in a clear channel).
Next, the client downloads the server's public certificate (in a clear channel).
At this point, the client has some work to do. It needs to verify the certificate. It needs to know that it understands the certificate, that the date range is valid, that the certificate is signed by a trusted certificate authority, and that the certificate has not been revoked.
Now, the client knows that it can trust the server.
Next, It sends a few short messages encrypted with the public key of the server (which is in the server's public certificate). These messages can only be decrypted by the server's private key (which only the server knows about). These messages allow the client and the server to negotiate a master key.
Finally, the client and the server begin the normal HTTP request and response using the newly created encrypted channel.
I hope this is what you are looking for. For a more detailed description see: http://www.moserware.com/2009/06/first-few-milliseconds-of-https.html
If the certificate was issued by a chain of certificate authorities whose root is trusted by Apple, then there is nothing to do. The iOS device will accept the certificate, as long as it is otherwise valid (ie not expired, not revoked, etc).
If the CA chain's root is not trusted by Apple, you will need to download the root's certificate to the phone. This can be done (I think) via the iPhone Configuration Utility. Enterprise provisioning scenarios undoubtedly support this also.