message::get_part_by_name causes segfault if the key it searches for does not exist

[Iuliean]

I was working with this

void Site::auth(const crow::request& req, crow::response& resp)
{
    CROW_LOG_INFO << "Login Attempt";
    crow::multipart::message msg(req);
    CROW_LOG_INFO << "Login Attempt";
    if(msg.get_part_by_name("password").body == password)
    {
        resp.body = Session::newSession();
        resp.code = 200;
        resp.end();
        return;
    }
    else
    {
        resp.code = 401;
        resp.body = "Failed login attempt";
        resp.end();
        return;
    }
}

And the server kept crashing when a request without that key was made

so i investigated

part get_part_by_name(const std::string& name)
{
    return part_map.find(name)->second;
}

this current implementation tries to imediately acces the object but if that object does not exist it tries to access part.end() which is unallocated memory.

i replaced it with

part get_part_by_name(const std::string& name)
{
    mp_map::iterator result = part_map.find(name);
    if(result != part_map.end())
        return result->second;
    else
        return {}; 
}

which seems to fix the issue and i am still able to check the body of the part or headers

please let me know if everything is correct and my fix is good :)

[The-EDev]

Your solution looks good, Feel free to open a PR with your solution (I'll do it if you don't want to :)).

Thank you for taking the time to report and investigate the issue!

[Iuliean]

is there a guide or something ?
i've never made one before and i was kinda hunting to find something to fix :))

Edit : nvm i figured it out