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POC++ Buffer Overflow
 

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    <p>I'm trying to teach myself about buffer overflows and exploitation in C++. I'm an intermediate C++ guy, at best, so bear with me. I've followed a few tutorials, but here's some example code to illustrate my question:</p> <pre><code>#include &lt;string&gt; #include &lt;iostream&gt; using namespace std; int main() { begin: int authentication = 0; char cUsername[10], cPassword[10]; char cUser[10], cPass[10]; cout &lt;&lt; "Username: "; cin &gt;&gt; cUser; cout &lt;&lt; "Pass: "; cin &gt;&gt; cPass; strcpy(cUsername, cUser); strcpy(cPassword, cPass); if(strcmp(cUsername, "admin") == 0 &amp;&amp; strcmp(cPassword, "adminpass") == 0) { authentication = 1; } if(authentication) { cout &lt;&lt; "Access granted\n"; cout &lt;&lt; (char)authentication; } else { cout &lt;&lt; "Wrong username and password\n"; } system("pause"); goto begin; } </code></pre> <p>I know there's all kinds of bad juju in here with <code>cin &lt;&lt; String</code>, etc... Anyhow, when I enter too many letters (a ton of <code>A</code>'s for instance) into <code>cUser</code> and <code>cPass</code>, I just get an Access Violation from Visual Studio. If, however, I type 20ish <code>A</code>'s, then a space, then another <code>A</code> into <code>cUser</code>, it skips asking me for <code>cPass</code> (assuming because it's been filled after the space character caused the previous call to <code>cin</code> to return) and just grants me access.</p> <p>At what point, and why, is data overflowing into "authentication" and why does it only happen when I have the space and not when I have a million <code>A</code>'s... I never get the "Access Violation" when I use a space in the input for <code>cUser</code>.</p>
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    1. USShafik Yaghmour
    1. USsraboy
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    1. COsystem("pause"); goto begin; Nope, pretty sure you are a beginner.
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      1. USFabián Heredia Montiel
    2. COAre you trying to get the overflow and wondering why it does that? Or do you want no overflow and are asking for a solution? Also you shouldn't system(). It's a huge backdoor for a hacker.
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    3. COAlso, I have a program called `pause` on my system that launches nuclear missiles. So I probably shouldn't run your program.
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      1. USDavid Schwartz
 

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