Frida: Unable to modify string passed as a const reference string

[AkhileshChaikam]

Using frida framework, I'm trying to change const reference std::string to empty value.

I've pasted my code here.

var f_log_ptr = DebugSymbol.findFunctionsMatching("OurFunction*")[0];
console.log("Log_VA is at", f_log_ptr);

var myStringBuf = Memory.allocUtf8String('');

Interceptor.attach(f_log_ptr, {
    onEnter: function (args) {
        console.log("Invoked");
        args[0] = myStringBuf;
    },

    onLeave: function (retval) {

    }
});

After I'm doing this , this is causing a undefined behaviour and my application crashes at random locations. Could anyone please help how to modify const reference string?

My CPP function is here

myFunction(const std::string &path)

std::string s = "some non empty";
myFunction(s);

My frida version is : 12.4.8

[eugenekolo]

If your function is this call then args0 is the this pointer. Perhaps you
want to modify args 1

• Sent from my iPhone 12SR.

On Fri, May 17, 2019, 8:47 AM AkhileshChaikam [e-mail]
wrote:

Using frida framework, I'm trying to change const reference std::string to
empty value.

I've pasted my code here.

var f_log_ptr = DebugSymbol.findFunctionsMatching("OurFunction*")[0];
console.log("Log_VA is at", f_log_ptr);

var myStringBuf = Memory.allocUtf8String('');

Interceptor.attach(f_log_ptr, {
onEnter: function (args) {
console.log("Invoked");
args[0] = myStringBuf;
},

onLeave: function (retval) {

}

});

After I'm doing this , this is causing a undefined behaviour and my
application crashes at random locations. Could anyone please help how to
modify const reference string?

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[eugenekolo]

Additionally you're stuffing a char* into a std::string. They're not
interchangeable. If you want to replace a std::string then you have to
craft or create one.

• Sent from my iPhone 12SR.

On Fri, May 17, 2019, 9:39 AM Eugene Kolodenker [e-mail]
wrote:

If your function is this call then args0 is the this pointer. Perhaps you
want to modify args 1

• Sent from my iPhone 12SR.

On Fri, May 17, 2019, 8:47 AM AkhileshChaikam [e-mail]
wrote:

Using frida framework, I'm trying to change const reference std::string
to empty value.

I've pasted my code here.

var f_log_ptr = DebugSymbol.findFunctionsMatching("OurFunction*")[0];
console.log("Log_VA is at", f_log_ptr);

var myStringBuf = Memory.allocUtf8String('');

Interceptor.attach(f_log_ptr, {
onEnter: function (args) {
console.log("Invoked");
args[0] = myStringBuf;
},

onLeave: function (retval) {

}

});

After I'm doing this , this is causing a undefined behaviour and my
application crashes at random locations. Could anyone please help how to
modify const reference string?

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or mute the thread
https://github.com/notifications/unsubscribe-auth/AASP42T3HP2XT6KQNCCWPA3PV2SMDANCNFSM4HNU67IQ
.

[AkhileshChaikam]

Thanks @eugenekolo for your reply, how can I create a std::string with frida. I couldn't find anywhere?

Can someone please help me how to create std::string in this case?