How do I make this simple shellcode c program compile from terminal?

问题

I am trying to compile this using the terminal on ubuntu 12:

#include <stdio.h>

#include <stdlib.h>

main()

{
    /*declare argument array*/
    char *args[2];

    args[0] = “/bin/bash”;
    args[1] = NULL;

    execve(args[0], args, NULL);

    exit(0);
}

I found this example on http://www.securitytube.net/video/235 which also happened to be the one Aleph One used in 'Smashing the Stack for Fun and Profit'. I am aware that much has changed since then. In more simple examples I have used:

gcc -ggdb -mpreferred-stack-boundary=2 -fno-stack-protector filename filename.c

Other times I may include the static utility. It has worked up until I have tried to compile the C code above. The message I receive from the terminal is:

ss@ss-laptop:~$ gcc -static -mpreferred-stack-boundary=2 -fno-stack-protector -o shell         shell.c
shell.c: In function ‘main’:
shell.c:9:2: error: stray ‘\342’ in program
shell.c:9:2: error: stray ‘\200’ in program
shell.c:9:2: error: stray ‘\234’ in program
shell.c:9:15: error: expected expression before ‘/’ token
shell.c:9:15: error: stray ‘\342’ in program
shell.c:9:15: error: stray ‘\200’ in program
shell.c:9:15: error: stray ‘\235’ in program
ss@ss-laptop:~$

I understand that this is a very simple example and that this error is probably caused by current standard security measures in linux but I would like to get around them to practise with this example and more in the future. If anyone can help, it would be 'smashing'.

cheers

回答1:

You have "smart" quotes around your string literal,

“/bin/bash”;

try using ordinary quotes ".

回答2:

I think that this has nothing to do with security and instead is the following line:

args[0] = “/bin/bash”;

The quote characters you're using to delimit the string are not the standard ASCII quote character; instead, they're pretty Unicode characters for quotes.

Try rewriting this as

args[0] = "/bin/bash";

by replacing the quote characters with fresh double-quotes.

As an aside - it's provably impossible for the compiler to detect all programs that might launch a shellcode. I would be shocked if any standard compiler would do anything at all to stop programs from compiling due to security holes.

Hope this helps!