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Network Services Pentesting
Frida Tutorial 3
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Solution 1

Hook the _exit()_ function and decrypt function so it print the flag in frida console when you press verify:
Java.perform(function () {
send("Starting hooks OWASP uncrackable1...");
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function getString(data){
var ret = "";
for (var i=0; i < data.length; i++){
ret += "#" + data[i].toString();
}
return ret
}
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var aes_decrypt = Java.use("sg.vantagepoint.a.a");
aes_decrypt.a.overload("[B","[B").implementation = function(var_0,var_1) {
send("sg.vantagepoint.a.a.a([B[B)[B doFinal(enc) // AES/ECB/PKCS7Padding");
send("Key : " + getString(var_0));
send("Encrypted : " + getString(var_1));
var ret = this.a.overload("[B","[B").call(this,var_0,var_1);
send("Decrypted : " + getString(ret));
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var flag = "";
for (var i=0; i < ret.length; i++){
flag += String.fromCharCode(ret[i]);
}
send("Decrypted flag: " + flag);
return ret; //[B
};
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var sysexit = Java.use("java.lang.System");
sysexit.exit.overload("int").implementation = function(var_0) {
send("java.lang.System.exit(I)V // We avoid exiting the application :)");
};
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send("Hooks installed.");
});

Solution 2

Hook rootchecks and decrypt function so it print the flag in frida console when you press verify:
Java.perform(function () {
send("Starting hooks OWASP uncrackable1...");
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function getString(data){
var ret = "";
for (var i=0; i < data.length; i++){
ret += "#" + data[i].toString();
}
return ret
}
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var aes_decrypt = Java.use("sg.vantagepoint.a.a");
aes_decrypt.a.overload("[B","[B").implementation = function(var_0,var_1) {
send("sg.vantagepoint.a.a.a([B[B)[B doFinal(enc) // AES/ECB/PKCS7Padding");
send("Key : " + getString(var_0));
send("Encrypted : " + getString(var_1));
var ret = this.a.overload("[B","[B").call(this,var_0,var_1);
send("Decrypted : " + getString(ret));
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var flag = "";
for (var i=0; i < ret.length; i++){
flag += String.fromCharCode(ret[i]);
}
send("Decrypted flag: " + flag);
return ret; //[B
};
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var rootcheck1 = Java.use("sg.vantagepoint.a.c");
rootcheck1.a.overload().implementation = function() {
send("sg.vantagepoint.a.c.a()Z Root check 1 HIT! su.exists()");
return false;
};
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var rootcheck2 = Java.use("sg.vantagepoint.a.c");
rootcheck2.b.overload().implementation = function() {
send("sg.vantagepoint.a.c.b()Z Root check 2 HIT! test-keys");
return false;
};
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var rootcheck3 = Java.use("sg.vantagepoint.a.c");
rootcheck3.c.overload().implementation = function() {
send("sg.vantagepoint.a.c.c()Z Root check 3 HIT! Root packages");
return false;
};
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var debugcheck = Java.use("sg.vantagepoint.a.b");
debugcheck.a.overload("android.content.Context").implementation = function(var_0) {
send("sg.vantagepoint.a.b.a(Landroid/content/Context;)Z Debug check HIT! ");
return false;
};
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send("Hooks installed.");
});
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