I'm setting up a server which an android app and an iPhone app will connect to. And I'm wondering what type of security is more secure for sending/requesting data?
Currently I generate a HMAC-SHA256 of the content I'm sending to the server in the header to verify its integrity.
But I'm wondering if its more secure to use a https connection instead? If I use https, could I skip the HMAC?
I would like to know the differences in security, which is more secure?
And also, if I'm using either is it better to use both for an extra layer of security?
Quick answer to your questions: SSL if used properly should give you more security guarantees than HMAC. So, usually SSL can be used in a way that removes the need for HMAC.
HMAC provides integrity as well as authenticity. Assuming the client and the server use pre-shared symmetric keys to calculate the HMACs, one side can be sure that the device on the other end has the secret key. This provides authenticity of both server and client.
What is missing in this picture (with just HMAC) is confidentiality. What is the nature of data exchanged between the server and client? Is there any sensitive user data being transferred during the communication that you don't want a man-in-the-middle to see? If so, then you may want to use SSL.
SSL gives you confidentiality (among other things). Meaning that you can be sure that you have a secured end-to-end connection and no man-in-the-middle can see what data is being exchanged between the server and client. However, common SSL usage does not include client machine authentication. Fro example, your web browser checks for Paypal's authenticity when you go to their https webpage. But the Paypal server does not ask your browser to send any certificate from your side.
Since you are comparing SSL with HMAC, I am assuming you care about authenticity of both sides. So, use SSL with both server and client authentication. This basically means that both of them would ask for each other's certificates and check different aspects of the certificates (i.e. common name, certificate issuer etc.). You can create your own certificate issuer to sign these certificates.
If you are making an app for AppStore or Google Play that users can simply install and start using, you may want to think through how the client side certificates will be generated, signed or who will sign them. You can remove the need for client side certificate (and signing) by adopting a model similar to GitHub's, where the user manually informs the server of trusted public keys to authenticate devices. But you can probably see how this process might not be user friendly.
Related
I want to authenticate a user by allowing him to create a username and password. Since I only find old posts about it, I'm creating this one.
Should I encrypt the password before sending to the server? If so, how should I do it? If not, should I use some specific configuration in my POST request to the server?
Is there any reliable third party api that I should use?
I know that Google has an androidx API for this things, but it's still in alpha.
If you use HTTPS protocol to comunicate with the server the data are already encrypted before beeing sent, anyway I suggest you to execute an additional encryption using Cipher.
PS see this question for more How to encrypt String in Java
You may make a basic obfuscation like Base64 or something like that, as Marco mentioned, HTTPS already secures the channel and information wouldn't be seen by a man in the middle.
Instead of encryption you may add a security validation that the HTTPS certificate is trusted, so that using Proxies such as Charles Proxy is also forbidden.
Encryption assumes an encryption key which needs to be securely distributed. Since the password (or a derivate of it) needs to be stored server side for subsequent authentication I would recommend to send the password in clear text at least when registering the username / password. Of course assuming that HTTPS, enforcing a secure protocol and hostname verification, is used. The benefit is that you don't add an implicit dependency to a specific algorithm to the server API. Instead the server application can hide this as an internal detail when storing the password (or a derivate) in the database. This makes API evolution less painful.
It is often recommended to use certificate pinning (i.e. "hard-coding" a server certificate client side) but this may be overengineering depending on your use case as it will require certificate lifecycle management.
All this said. You probably would benefit from using a third party service (e.g. AWS cognito) for authentication, at least in the short term. This way you can more easily implement 2-factor authentication when creating the account, login abuse prevention, password recovery, etc
I am trying to learn about making secure mobile applications. I am curious to know, do we need Certificate pinning if our network calls from mobile to server use https ?
Yes, you should save it as a raw file in the folder of your app and use it to call the server for the requests.
Pay attention, if you have a self signed certificate you should force it as made by trusted authority.
I am curious to know, do we need Certificate pinning if our network calls from mobile to server use https ?
https guarantees that the data in transit between your mobile app and API server is encrypted and cannot be spied on by third parties, thus partially preventing it against Man in the Middle attacks.
So I say partially because an attacker can induce users to install a custom ssl certificate in order for them to use a free wifi. This is usually done with fake wifi captive portals where you have to sign in in order to have free wifi, like the ones you found in airports, trains, etc. If an attacker succeeds in tricking the user then all the traffic is routed through the attackers computer and despite being https it can be decrypted once the mobile app is using the attackers custom certificate, but the attacker will always use the original certificate when communicating with the API server, thus neither the API, server, mobile app or the user are aware that the communication is being intercepted and maybe even tampered with.
So using certificate pinning will prevent any type of a Man in Middle Attack to occur, even the ones where the user of the mobile app is the attacker that intentionally decrypts is own traffic in order to reverse engineer the mobile app communication with the API server in order to gain enough knowledge to mount an attack against it.
Now is time for the bad news... Certificate pinning can be bypassed when the attacker as access or controls the mobile device. This article walks you through on how certificate pinning can be used and bypassed by using a framework like xPosed, that will intercept the calls to validate the certificate, thus bypassing the validation process.
So should I use certificate pinning? Yes you should, because is one more layer of defence and requires more effort for an attacker to reverse engineer your mobile app, that he may deem not be worthy the effort, but if he deems worthy the effort then you may want to search in google for a Mobile App Attestation solution to protect further the communication between the mobile app and the API server.
But keep in mind that while certificate pinning may be easy to implement in your mobile app it may be an operational nightmare to maintain. Be sure to read the section PINNING IS A NIGHTMARE in the link I referenced previously about bypassing certificate pinning.
Edit
You can read the article Steal that API Key with a Man in the Middle Attack to see a practical example on how a secret can be extracted from a https request sent from a mobile app to the backend API, by performing a MitM attack.
So, in this article you will learn how to setup and run a MitM attack to intercept https traffic in a mobile device under your control, so that you can steal the API key. Finally, you will see at a high level how MitM attacks can be mitigated.
While we can use advanced techniques, like JNI/NDK, to hide the API key in the mobile app code, it will not impede someone from performing a MitM attack in order to steal the API key. In fact a MitM attack is easy to the point that it can even be achieved by non developers.
Afterwards you can also take a look to the article Securing HTTPS with Certificate Pinning on Android to understand how you can implement certificate pinning to prevent a MitM attack.
In this article you have learned that certificate pinning is the act of associating a domain name with their expected X.509 certificate, and that this is necessary to protect trust based assumptions in the certificate chain. Mistakenly issued or compromised certificates are a threat, and it is also necessary to protect the mobile app against their use in hostile environments like public wifis, or against DNS Hijacking attacks.
You also learned that certificate pinning should be used anytime you deal with Personal Identifiable Information or any other sensitive data, otherwise the communication channel between the mobile app and the API server can be inspected, modified or redirected by an attacker.
Finally you learned how to prevent MitM attacks with the implementation of certificate pinning in an Android app that makes use of a network security config file for modern Android devices, and later by using TrustKit package which supports certificate pinning for both modern and old devices.
I hope that both articles have made more clear why certificate pinning is recommended to be used to secure https connections from prying eyes.
EDIT 2
If you want to implement certificate pinning but are afraid of making any mistake while creating the network_security_config.xml configuration file then just use this free Mobile Certificate Pinning Generator to create it for you:
and it will give you a network_security_config.xml configuration file ready to be copy pasted:
I have an android application that I send some information from the android device to my web server and the information has to be secure through the network till it reaches the server.
I was thinking about using HTTP SSL request, but maybe there are similar options that are free and secure as well.
So what are the options available to encrypt a HTTP POST request through the network?
Thanks in advance.
SSL is definitely the best option and can be free assuming you can install certificates on the devices in question, or prompt the user to do so. That said, it may be a red flag to users if they're prompted to install some strange certificate. You could encrypt the payload using a symmetric encryption scheme (like AES) but then the issue is either key exchange (how do you get the key onto the device) or, if you use a key coded into the app, anybody could access the key from the binary.
Alternatively you could use asymmetric encryption using a server public key that is hard coded into the app, but then you also need to provide for data integrity checks etc.
In summary, just use HTTPS. There's a 99.999999% chance whatever you write will be less secure than accepted, industry standards.
We have a web service that should only be called by a specific Android app. What solutions are there for this problem?
The requirement is to not use authentication at all.
If it's only your client and your server, you can (and should) use SSL without purchasing anything. You control the server and the client, so each should only trust one certificate, the one belonging to the other and you don't need CAs for this purpose.
Here's the high-level approach. Create a self-signed server SSL certificate and deploy on your web server. You can use the keytool included with the Android SDK for this purpose. Then create a self-signed client and deploy that within your application in a custom keystore included in your application as a resource (keytool will generate this as well). Configure the server to require client-side SSL authentication and to only accept the client certificate you generated. Configure the client to use that client-side certificate to identify itself and only accept the one server-side certificate you installed on your server for that part of it.
A step-by-step for this is a much longer answer than is warranted here. I would suggest doing this in stages as there are resources on the web about how to deal with self-signed SSL certificate in Android, both server and client side. There is also a complete walk-through in my book, Application Security for the Android Platform, published by O'Reilly.
You'll normally store that certificate/private-key in a keystore of sometype (a KeyStore if you're using Android) and that keystore will be encrypted. That encryption is based on a password, so you'll either need to (1) store that password in your client somewhere, or (2) ask the user for the password when they start your client app. What you need to do depends on your usecase. If (2) is acceptable, then you've protected your credential against reverse engineering since it will be encrypted and the password will not be stored anywhere (but the user will need to type it in everytime). If you do (1), then someone will be able to reverse engineer your client, get the password, get the keystore, decrypt the private key and certificate, and create another client that will be able to connect to the server.
There is nothing you can do to prevent this; you can make reverse engineering your code harder (by obfuscation, etc) but you cannot make it impossible. You need to determine what the risk you are trying to mitigate with these approaches is and how much work is worth doing to mitigate it.
I guess this will work with proper authentification in place. First post I just stumpled upon was this one:
Securing communication from android to a web service
Hope it helps =)
If you're absolutely certain this web service will only need to be accessed by authorized applications/devices, go with client-side SSL certificates and restrict access at the server to only clients with authorized certs. This has the bonus feature of forcing SSL at all times so you don't like auth secrets over an open channel. Here's a quick guide for Apache, but you could use nginx too:
http://it.toolbox.com/blogs/securitymonkey/howto-securing-a-website-with-client-ssl-certificates-11500
I am looking for different ways to authenticate client like android, iphone, windows and blackberry app and which one is better and why
As per my research I know of 2 way to authenticate client
1. Private key embedded inside smartphone app which will be used to sign the message : Problem with this is its easy for hacker to get access to private key
2. Client certificate
Are there other ways to authenticate these smartphone app and which one is most secured?
Both of the options you list here are really the same. A client certificate is really just the public key part of a private/public keypair that is signed by some entity along with some identification information.
The best way to authenticate the client is to use mutually authenticated SSL. You can use self-signed certificates here so you don't need to buy any from a CA, assuming you control all of the clients that you want to allow access and you control the servers they are going to talk to. This will ensure that your clients only receives data from your legitimate server (configure the SSL system for your application to only accept the self-signed certificate that your server is using) and your server only accepts data from your authorized clients (configure your server to only access the self-signed certificates deployed in your app as a resource for client authentication). There is a complete step-by-step rundown on how to do this for Android in Application Security for the Android Platform, published by O'Reilly.
You are correct in that you need to embed some secret information (a private key) in your client application and an attacker will be able to compromise it. The best solution you have within Android right now is to put the certificate and private key in a Keystore that you include in your application APK as a resource and have your application access the Keystore when it needs to use the key. That means your application will need to have the password to the Keystore. So, how you protect that password becomes important. You can obfuscate your code to make it harder for an attacker to determine that password, but that will only slow down a determine attacker who is reverse engineering your application. However, short of requiring the user of the device to type that password in every time they want to use your application, that's the best you can do. If your client app that is running on the device needs access to something that it stores, a person with access to that device will be able to access it as well. All you can do it make it more difficult.