Oracle Tips by Burleson Consulting
Because APEX openly passes screen values
between screens (see
passing values between APEX screens), we need to ensure that
a malicious end-user does not have the ability to "snoop" on other
values by changing the literal values. The URL page variable
data can also be protected by using page computations in lieu of
passing them in the URL. Remember, session state is "global" for an
application and one page can set the session state for another pages
All of these APEX security exposure
vulnerabilities can be avoided by careful configuration, but there
are many potential security exposures to consider. There are
several areas of potential APEX exposure:
Search Engine vulnerability - If a
search engine indexes an Oracle APEX web site, URL's with
exposed data values become public.
Referrer statistics exposure - If an
APEX end-user clicks away from an APEX screen, the
referrer URL might send data values to the destination web site.
Hoover Bots - People can write
scripts to replicate APEX transactions, vacuuming out all
exposed Oracle data.
URL Tampering - With improper
configuration, end-users can alter their APEX URL and see
data outside the scope of the APEX application.
Search Engine Vulnerabilities
If Google indexes your APEX database you may
expose confidential data to the public. We can see all APEX pages with the Google "inurl:"
search feature to only show Google results where the URL contains
the string "f?p=".
The Google query to find pages with data
exposures might look
like this Google query that shows unintended Oracle database
values within the URL. The exposure is not just limited to
Google as many search engines (especially malicious bots) will not
honor "nofollow" tags in the pages. The DBA must be always
vigilant to ensure that all APEX details are placed in password
secured directories, unavailable to any search engine.
Permissions like 700 or 770 on the inodes (directories) will take
care of this exposure. For related details, see Finding
APEX Hacking vulnerabilities with Google.
Referrer Statistics exposures
Referrer statistics are sent as part of an HTTP
request, and there is the possibility that an end-user who navigates
directly from their APEX screen will send unencrypted data values
to the destination web site. This is especially prevalent if
the end-users have fast-access toolbars in their browser, such as
the Google Toolbar.
Any al all data exposed via an APEX
application can be hoovered off into another Oracle database.
For details, see superb
this article on how someone hoovered megabytes from Amazon's
“Using a pair
of 5-year-old computers, two home DSL connections, 42 hours of
computer time, and 5 man hours, I now had documents describing
the reading preferences of 260,000 U.S. citizens. I
downloaded all the files to an external 120 GB Firewire drive in
APEX URL Tampering
From this excellent
APEX best practices security whitepaper we see that URL
tampering can work:
"Web based applications, including those
developed in Oracle HTML DB often pass values from one page to
another through a URL. A clever enough user may observe this and
override a value by typing his own value in the location field
of his browser. For example, on a page that displays a form for
editing an employee record the value in session state of a
certain item may determine which record is displayed In HTML DB,
the session state of this item can be set in the URL containing
Where 100 is the application ID, 1 the page
ID, P1_EMPID the session state variable and 1234 represents a
primary key value in a table of employees. When a user clicks on
such a link it will appear in the browser’s location field. At
this point the user can experiment and modify the URL into:
in the hope of retrieving the employee
record with the primary key value 5678. The user in question may
or may not be allowed to look at the details for employee 5678.
If she is not allowed, appropriate authorization rules should be
applied to the logic on the page and, even better, at the
database level to prevent her from viewing this data. Obscuring
the value passed in the URL through a form of encoding or
encryption is not sufficient. Put another way, don’t attempt to
secure your application by obscuring values passed in a URL.
Rather, secure the destinations that URLs go to using database
level security policies.
In addition, you can use HTML DB
authorization schemes. Cross Site Scripting Cross site
scripting, sometimes called XSS, is a security breach that takes
advantage of dynamically generated Web pages. "
The URL page variable data can also be
protected by using page computations in lieu of passing them in the
URL, and all variables are available via the application global
session state. Here is an excerpt from the book "Easy Oracle HTML-DB Application Express
" discussing creating Page Processing Computations.
The computation locations identifies where the page item is located
that will be set by the computation.
Item on This Page – Used to set the
value of a single item on the current application page.
Item on Another Page – This type of
computation is useful when you want you are navigating to
another page and you want to set page items on that page. Using
this method you can hide the values by not having to send them
in the URL. The limitation of using this method is the page
would not provide a URL for the user to save in the browser as a
Favorite (such as a sale item on your web site).
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