[rlug] safe stub

[Mihai Marusca]

Ziceam zilele trecute ca vreau ca un user de r�nd sa execute `iptables -t
filter -L <chain> -n -v -x`.
Ionut Spirlea mi-a indicat cum sa fac setuid. Am facut stub-ul si am fost
happy. Rulez ceva de genul `iptables_mrtg acc_in` si mierje.

Dupa aia am inceput sa-mi pun probleme... Se poate executa ceva de genul:
`iptables_mrtg "; ls -l /root/;`. Nu mai sunt happy...

Drept care am facut oarece validari pe parametrul pe care-l primesc, si e
mai bine.

Asa cum am mai spus, ceva C mai stiu eu, da' programare sub Linux ioc. Drept
care supun ironiei publice codul de mai jos.

Mihai

/****************************************/
#include <stdlib.h>
#include <unistd.h>

int usage()
{
    printf(
        "iptables_mrtg ver. 0.99\n"
        "\n"
        "usage: iptables_mrtg <chain>\n"
    );
    return 1;
}

int valid_char(const char ch)
{
    return isalnum(ch) || (ch == '_');
}

int check_chain(const char * chain)
{
    int isvalid = 1;
    const char * ptr;
    if(strlen(chain) > 16)
        isvalid = 0;
    else
        for(ptr = chain; ptr && *ptr; ptr++)
        if (!valid_char(*ptr))
        {
            isvalid = 0;
            break;
        }
    return isvalid;
}

int doit(const char * chain)
{
    char buffer[1024];
    sprintf(buffer, "/sbin/iptables -t filter -L %s -n -v -x", chain);
    setuid(0);
    return system(buffer);
}

int main(int argc, char **argv)
{
    if (argc != 2)
        return usage();
    if(!check_chain(argv[1]))
    {
        printf("Invalid chain name\n");
        return 1;

    }
    return doit(argv[1]);
}



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