Codebase Security

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Revision as of 12:14, 3 March 2013 by Bradymiller (talk | contribs) (→‎Plan)

Codebase Security Vulnerability Assessment and Fixing

Assessment

  • Security analysis of OpenEMR by the OWASP team of the Technical Educational Institute of Larisa (contributed by Avantsys Informatics):
The Realsearch group at NC State has been working with OpenEMR in it's evaluation of the CCHIT security criteria. As a part of this research they've done automated testing of the application and have discovered a number of security vulnerabilities with the software. They have gone through and tried to manually verify each vulnerability. The list of actual vulnerabilities, more than 500 in total, can be found at the links below. The true vulnerabilities have a value of True in the 'Vulnerable' column.
As a summary, here are the types of issues they've found and their counts:
Fortify 360:
Cross-Site Scripting (215)
Nonexistent Access Control (129)
Dangerous Function (24)
Path Manipulation (20)
Error Information Leak (19)
Global Variable Manipulation (9)
Insecure Upload (8)
Improper Cookie Use (7)
HTTP Header Manipulation (4)
Rational AppScan:
Cross-Site Scripting (50)
Phishing Through Frames (25)
Cross-Site Request Forgery (22)
Error Message Information Leak (14)
SQL Injection (4)
JavaScript Cookie References (6)
Directory Listing (6)
Password Not Encrypted (2)
Path Disclosure (1)

Plan

  • Proposal/plan to fix. This is a specific proposal/plan which is currently underway in order to prevent sql-injection and xss attacks. This involves a per script walk-through of the code. For developers, new scripts or scripts that have been converted to this new system need to follow these steps. Not only does this secure the script from sql-injection and xss attack, but it also markedly simplifies coding since the developer does not need to deal/worry about database escaping of variables (escape for a rare case). The strategy includes the following steps; will first discuss the strategy, and then will discuss how to practically do it.
1. Remove the mechanism to fake register globals.
2. Automatically reverse magic quotes (if turned on).
3. Utilize binding/placeholders in sql calls (prevents sql-injection). If making a sql call that contains a variable in it, then use a placemaker.
  • Exception in sql queries that contain numerous variables or when placing a variable to represent a sql tabl or colum name; in this case utilize the add_escape_custom() function from the library/formdata.inc.php script.
4. Utilize htmlspecialchars function (prevent xss attacks). This function should be wrapped around all text that can potentially be "touched" by the user.
  • Exception to rule 4 for javascript literals; when using javascript literals, utilize the addslashes function instead to prevent white screen of death.


  • Below is how to practically complete the above steps:


Step 1. Remove the mechanism to fake register globals. Place the following code at top of script above the include statement for the globals.php file:
    $fake_register_globals=false;


Step 2. Automatically reverse magic quotes (if turned on). Place the following code at top of script above the include statement for the globals.php file:
    $sanitize_all_escapes=true;


Step 3. Utilize binding/placeholders in sql calls (prevents sql-injection).
    sqlStatement=("DELETE FROM immunizations WHERE id =? LIMIT 1",array($_GET['id']);
  • Exception to step 3 for when there are a large number of variable in the sql query(if do this, need to treat all variables this way; meaning do not combine the two methods in one statement to avoid the '?' character within datafields breaking things)(also ensure surround the variable with the single quotes):
        sqlStatement=("UPDATE lists SET " .
        "type = '" . add_escape_custom($text_type) . "', " .
        "title = '" . add_escape_custom($_POST['form_title']) . "', " .
        "comments = '". add_escape_custom($_POST['form_comments']) . "', " .
        ...
  • Exception to step 3 for when a variable represents a LIMIT amount(s):
        sqlStatement=("SELECT * FROM users WHERE id =1 LIMIT ".escape_limit($limit_number));
  • Exception to step 3 for when a variable represents a sort ordering sql keyword(asc or desc):
        sqlStatement=("SELECT * FROM users WHERE id =1 ORDER BY id ".escape_sort_order($sort_order_keyword));
  • Exception to step 3 for when a variable represents a sql identifier:
  • If all the possible options are known beforehand, then use:
        $options = array("users","patients",documents);
        sqlStatement=("DELETE FROM ".escape_identifier($table_name,TRUE,$options)." WHERE id =1");
  • If all the possible options are not known beforehand, then use:
        sqlStatement=("DELETE FROM ".escape_identifier($table_name)." WHERE id =1");
Step 4. Utilize htmlspecialchars function wrappers from library/htmlspecialchars.inc.php. These functions have ample documentation within that file. (prevents cross-scripting attacks)
    require_once("$srcdir/htmlspecialchars.inc.php");
    $para_class = attr($db_data); //is escaped(including quotes)
    $para_content = text($user_data); //is escaped(not including quotes)
    $title_text = xla('My Title'); //is translated and escaped(including quotes)
    $header_text = xlt('My Header'); //is translated and escaped(not including quotes)
    echo "<h3>$header_text</h3><p class='$para_class' title='$title_text'>$para_content</p>\n";
  • Exception to step 4 for javascript literals; when using javascript literals, utilize the addslashes function instead to prevent white screen of death, or for translation strings use the new (as of 12/21/2012) xls() shorthand function included in library/htmlspecialchars.inc.php
        <script LANGUAGE="JavaScript">
        alert('<?php echo addslashes($db_data)); ?>'); // escape potential quotations marks
        alert('<?php echo xls('Quotes and Apostrophes in translations may cause problems'); ?>
           // If the return value for a translation contains quotes or apostrophes using just xl
           // would result in white screen of death.  Prefer xls, but addslashes(xl('my string')) 
           // will prevent problems.
        </script>
  • Another rare exception to step 4 when further nesting php variable within a javascript literal that is nested within html code.
        "<a href='' onclick='return selcode(\"" . attr(addslashes($drug_id)) . "\")'>";

Implementation

  • Below are examples where scripts have been converted to the new security mechanism discussed above:
Layout Based Fields forms: http://github.com/openemr/openemr/commit/61c95e62f79ad2afb68a2e8b1f81e3cca20b99ea
Part of Billing Module and calendar add_edit_event.php script: http://github.com/openemr/openemr/commit/f6310936b9dbc74e591ad56a75dae80b7791639d
Drug Dispensory Module: http://github.com/openemr/openemr/commit/67c82076f8af6ca08009a8948641e57cc0b8bd90
Address Book module: http://github.com/openemr/openemr/commit/c3243ac074795657a35b04609b83dac7ed423af0
add_edit_issue.php script: http://github.com/openemr/openemr/commit/34874e7e1e4e76ec44fb62a07136121462b306e1
Messages and Pnotes (patient notes) module: http://github.com/openemr/openemr/commit/21e15cce4507d36c7ffd234f2c4f034b38d1087e
Patient searching modules: http://github.com/openemr/openemr/commit/a9aa64513e4556aeb2f36b049e86aac47b3fef42
Transactions module: http://github.com/openemr/openemr/commit/f56f469c9d2481f3d440c79db1917e0a38f076a9
Patient history module: http://github.com/openemr/openemr/commit/a4817af442d569525b24129ed75afa915030a4dd
Immunization module: http://github.com/openemr/openemr/commit/5d06c6f08d04405a80b036810a8523a7cb680a31
Authorization module: http://github.com/openemr/openemr/commit/e08e3327b83f36164db0177c9acb8b7a1c3f9ddb
demographics.php script: http://github.com/openemr/openemr/commit/c0bfa8a51106cd97842374d5ae719bb5b469b763
Language admin gui module: http://github.com/openemr/openemr/commit/28f02594d450ce1e1546557b4cee040b8bedc194

Ongoing Discussion

Other miscellaneous security fix methods

Sanitize filenames and directory names

Use the functions in the library/sanitize.inc.php script.
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