Damn Vulnerable Android Application by Security Compass - Lab 2 Server Side Authorization Issue

 Lab 2 Server Side Authorization Issue

Welcome back my friends now we are gonna have hands on on server side authorization issue in this lab we will use burp proxy try to manipulate the parameters and will see the impact.

The server side authorization issue is in bank transfer function of an app as now a days some android apps rely on traditional architecture like REST interfaces to perform the functions.

We can intercept the server client communication in 2 ways:

1) Go to settings -->more -->mobile networks --> Access point names create one new access point change proxy option to your proxy IP and change the port to port of proxy and save it. now your communication will be intercepted by proxy.

2)Another way is to start the emulator in proxy mode by giving below command

emulator.exe @[AVD name] -http-proxy [proxy IP]:[proxy port]

so now we are ready to intercept the communication.




Lets launch the app



Now as I said the server side authorization issue is on transfer function so tap on transfer and try to trasnfer the funds




as you can see that we tried to transfer 50 bucks and intercepted the request in burp

we are having some preconfigured accounts

1. jdoe / password
   
   • Debit: 123456789
   • Credit: 987654321
2. bsmith / password
   
   • Debit: 111111111
   • Credit: 22222222

 So now we will try to change the debit account

 as you can see we changed the debit account from 123456789 to 111111111 which belongs to Bsmith.

and thats it we got the funds in our account that too even a single buck not got deducted from our debit account.

so the impact is very severe.



Solution

So the solution is that we should have some server side validation




#To validate on server side that accounts belong to user:
if to_account.user != session.user or from_account.user != session.user:
    return error("E6")

#validate that amount is positive
if total_cents < 0:
    return error("E5")

Lab 3 Insecure File Storage