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Oracle® Traffic Director Administrator's Guide
11g Release 1 (11.1.1.7.0)

Part Number E21036-04
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B.2 Rules Against Major Attacks

This section provides information about some rules that are used for preventing major attacks on Web applications.

B.2.1 Brute Force Attacks

Brute force attacks involve an attacker repeatedly trying to gain access to a resource by guessing usernames, passwords, e-mail addresses, and similar credentials. Brute force attacks can be very effective if no protection is in place, especially when users choose passwords that are short and easy to remember.

A good way to defend against brute force attacks is to allow a certain number of login attempts, after which the login is either delayed or blocked. Here is an example of how this can be accomplished using Oracle Traffic Director web application firewall.

If your login verification page is situated at yoursite.com/login and is served by the virtual server waf-vs, then the following rules, in waf-vs.conf file configured at the virtual server level, will keep track of the number of login attempts by the users:

# Block further login attempts after 3 failed attempts

# Initalize IP collection with user's IP address
SecAction "initcol:ip=%{REMOTE_ADDR},pass,nolog"

# Detect failed login attempts
SecRule RESPONSE_BODY "Unauthorized" "phase:4,pass,setvar:ip.failed_logins=+1,expirevar:ip.failed_logins=60"

# Block subsequent login attempts
SecRule IP:FAILED_LOGINS "@gt 2" deny

The rules initialize the IP collection and increment the field IP:FAILED_LOGINS after each failed login attempt. When more than three failed logins are detected, further attempts are blocked. The expirevar action is used to reset the number of failed login attempts to zero after 60 seconds, so the block will be in effect for a maximum of 60 seconds.

To use the persistent collection, IP, you should specify the path to store the persisted data using the SecDataDir directive. Since the scope of this directive is Main, it should be specified at the server level. This can be accomplished as follows:

# The name of the debug log file
SecDebugLog ../logs/brute_force_debug_log
 
# Debug log level
SecDebugLogLevel 3
 
# Enable audit logging
SecAuditEngine On
 
# The name of the audit log file
SecAuditLog ../logs/brute_force_audit_log
 
# Path where persistent data is stored
SecDataDir "/var/run/otd/waf/"

If this rules file is called waf-server.conf , <instance-dir>/config/server.xml would look like this:

<server>
...
...
   <webapp-firewall-ruleset>/waf-rules/waf-server.conf</webapp-firewall-ruleset>
...
...
    <virtual-server>
      <name>waf-vs</name>
      <host>yoursite.com</host>
      ...
      <object-file>waf-vs-obj.conf</object-file>
      <webapp-firewall-ruleset>/waf-rules/waf-vs.conf</webapp-firewall-ruleset>
    </virtual-server>
...
...
</server>

Web application firewall and response body processing (equivalent of SecResponseBodyAccess directive) should be enabled for the /login URI in waf-vs-obj.conf. waf-vs-obj.conf would look like this:

<Object name="default">
<If $uri eq "/login">
AuthTrans fn="webapp-firewall" process-response-body="on"
</If>
...
...
</Object>

After 3 failed attempts to login, audit log would have the following message:

--5c4adf36-A--
[19/Mar/2013:05:06:57 --0700] ygfh3010000000000,0 127.0.0.1 49619 127.0.0.1 5021
--5c4adf36-B--
GET /acl/acl02.html HTTP/1.1
user-agent: curl/7.15.5 (x86_64-redhat-linux-gnu) libcurl/7.15.5 OpenSSL/0.9.8b zlib/1.2.3 libidn/0.6.5
accept: */*
host: yoursite.com
authorization: Basic YWxwaGE6YmV0YQ==
 
--5c4adf36-F--
HTTP/1.1 403 Forbidden
status: 403 Forbidden
content-length: 208
content-type: text/html
 
--5c4adf36-H--
Message: Warning. Unconditional match in SecAction. [file "/waf-rules/waf-vs.conf"] [line "10"]
Message: Access denied with code 403 (phase 2). Operator GT matched 2 at IP:failed_logins. [file "/waf-rules/waf-vs.conf"] [line "25"]
Action: Intercepted (phase 2)
Stopwatch: 1363694817000000 898560 (- - -)
Stopwatch2: 1363694817000000 898560; combined=370, p1=14, p2=336, p3=0, p4=0, p5=19, sr=131, sw=1, l=0, gc=0
Producer: ModSecurity for Apache/2.6.7 (http://www.modsecurity.org/).
Server: Oracle Traffic Director/11.1.1.7
 
--5c4adf36-Z--

B.2.2 SQL Injection

SQL injection attacks can occur if an attacker is able to supply data to a Web application that is then used in unsanitized form in an SQL query. This can cause the SQL query to do something that is completely different from what was intended by the developers of the Web application. For example, an attacker can try deleting all records from a MySQL table, like this:

http://www.example.com/login.php?user=user1';DELETE%20FROM%20users--

This can be prevented by using the following directives:

SecDefaultAction "phase:2,log,auditlog,deny,status:403"
SecRule ARGS "(select|create|rename|truncate|load|alter|delete|update|insert|desc)\s*" "t:lowercase,msg:'SQL Injection'"

Whenever the web application firewall engine spots such a request, something similar to the following code is logged to audit_log:

--3923b655-A--
[20/Mar/2013:02:58:35 --0700] Xkjx6010000000000,0 127.0.0.1 35971 127.0.0.1 5021
--3923b655-B--
GET /acl/acl02.html?user=user1';DELETE%20FROM%20users-- HTTP/1.1
host: waf.test.com
connection: close
 
--3923b655-F--
HTTP/1.1 403 Forbidden
status: 403 Forbidden
content-length: 208
content-type: text/html
connection: close
 
--3923b655-H--
Message: Access denied with code 403 (phase 2). Pattern match "(select|create|rename|truncate|load|alter|delete|update|insert|desc)\\s*" at ARGS:user. [file "/waf-rules/sql_injection_attack.conf"] [line "2"] [msg "SQL Injection"]
Action: Intercepted (phase 2)
Stopwatch: 1363773515000000 668049 (- - -)
Stopwatch2: 1363773515000000 668049; combined=131, p1=8, p2=104, p3=0, p4=0, p5=19, sr=0, sw=0, l=0, gc=0
Producer: ModSecurity for Apache/2.6.7 (http://www.modsecurity.org/).
Server: Oracle Traffic Director/11.1.1.7
 
--3923b655-Z--

In response to the attack, SecDefaultAction is applied. in which case the request is denied and logged, and the attacker receives a 403 error. If you would like a different action to take place, such as redirect the request to an HTML page with a customized warning content, specify it in the rule, as follows:

SecRule ARGS "(select|create|rename|truncate|load|alter|delete|update|insert|desc)\s*" "t:lowercase,msg:'SQL Injection',redirect:http://yoursite.com/invalid_request.html

B.2.3 XSS Attacks

Cross-site scripting (XSS) attacks occur when user input is not properly sanitized and ends up in pages sent back to users. This makes it possible for an attacker to include malicious scripts in a page by providing them as input to the page. The scripts will be no different from scripts included in pages by creators of the website, and will thus have all the privileges of an ordinary script within the page, such as the ability to read cookie data and session IDs.

Here is an example of a simple rule to block <script in the request parameter:

SecDefaultAction phase:2,deny,status:403,log,auditlog
SecRule REQUEST_COOKIES|REQUEST_COOKIES_NAMES|REQUEST_FILENAME|ARGS_NAMES|ARGS|XML:/* "(?i:<script.*?>)" "phase:2,capture,t:none,t:htmlEntityDecode,t:compressWhiteSpace,t:lowercase,block,msg:'Cross-site Scripting (XSS) Attack',id:'101'"