Security Summer School

User Tools

Site Tools

session:01

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision 		Previous revision
session:01 [2020/06/22 16:50]
Rareş-Mihail VISALOM (67101) [Resources] 		session:01 [2020/07/19 12:49] (current)
Line 1: Line 1:
-= 0x01. Exploration Tools+====== 0x01. Exploration Tools ======
  
-== Resources+===== Resources =====
  
 [[https://security.cs.pub.ro/summer-school/res/slides/01-exploration-tools.pdf|Session 1 slides]] [[https://security.cs.pub.ro/summer-school/res/slides/01-exploration-tools.pdf|Session 1 slides]]
Line 7: Line 7:
 /*[[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-skel.zip|Session's tutorials and challenges archive]]*/ /*[[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-skel.zip|Session's tutorials and challenges archive]]*/
  
-[[https://security.cs.pub.ro/summer-school/wiki/_media/session/01-exploration-tools-last.zip|Session's tutorials and challenges archive]]+/*[[https://security.cs.pub.ro/summer-school/wiki/_media/session/01-exploration-tools-last.zip|Session's tutorials and challenges archive]]*/
  
 +[[https://security.cs.pub.ro/summer-school/wiki/_media/session/01-exploration-tools-last-last.zip|Session's tutorials and challenges archive]]
  
  
 /*[[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-full.zip|Session's solutions]]*/ /*[[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-full.zip|Session's solutions]]*/
  
-== Tutorials+===== Tutorials =====
  
 When faced with a binary with no source or parts of the source missing you can infer some of its functionalities based upon some basic reconnaisance techniques using various tools. When faced with a binary with no source or parts of the source missing you can infer some of its functionalities based upon some basic reconnaisance techniques using various tools.
  
  
-=== 01. Tutorial - Poor man's technique: strings +==== 01. Tutorial - Poor man's technique: strings  ====
  
 The simplest recon technique is to dump the ASCII (or Unicode) text from a binary. It doesn't offer any guarantees but sometimes you can get a lot of useful information out of it. The simplest recon technique is to dump the ASCII (or Unicode) text from a binary. It doesn't offer any guarantees but sometimes you can get a lot of useful information out of it.
Line 68: Line 69:
 </note> </note>
  
-=== 02. Tutorial - Execution tracing (ltrace and strace)+==== 02. Tutorial - Execution tracing (ltrace and strace) ====
 [[http://man7.org/linux/man-pages/man1/ltrace.1.html|ltrace(1)]] is an utility that can list the calls made to library functions made by a program, or the [[http://man7.org/linux/man-pages/man2/syscalls.2.html|syscalls]] a program makes. A syscall is a function that uses services exposed by the kernel, not by some separate library.  [[http://man7.org/linux/man-pages/man1/ltrace.1.html|ltrace(1)]] is an utility that can list the calls made to library functions made by a program, or the [[http://man7.org/linux/man-pages/man2/syscalls.2.html|syscalls]] a program makes. A syscall is a function that uses services exposed by the kernel, not by some separate library. 
  
Line 123: Line 124:
 The ''deobf()'' function calls ''strlen()'' and that's why you get such a large number of ''strlen()'' calls when running ''crackme2'' under ''ltrace''. The ''deobf()'' function calls ''strlen()'' and that's why you get such a large number of ''strlen()'' calls when running ''crackme2'' under ''ltrace''.
  
-=== 03. Tutorial - Symbols: nm+==== 03. Tutorial - Symbols: nm ====
  
 Symbols are basically tags/labels, either for functions or for variables. If you enable debugging symbols you will get information on all the variables defined but normally symbols are only defined for functions and global variables. When stripping binaries even these can be deleted without any effect on the binary behaviour. Dynamic symbols, however, have to remain so that the linker knows what functions to import: Symbols are basically tags/labels, either for functions or for variables. If you enable debugging symbols you will get information on all the variables defined but normally symbols are only defined for functions and global variables. When stripping binaries even these can be deleted without any effect on the binary behaviour. Dynamic symbols, however, have to remain so that the linker knows what functions to import:
Line 251: Line 252:
 Dealing with stripped binaries (or worse, statically linked binaries that have been stripped) is harder but can still be done. We'll see how in a future lab. Dealing with stripped binaries (or worse, statically linked binaries that have been stripped) is harder but can still be done. We'll see how in a future lab.
  
-=== 04. Tutorial - Library dependencies+==== 04. Tutorial - Library dependencies ====
  
 Most programs you will see make use of existing functionality. You don't want to always reimplement string functions or file functions. Therefore, most programs use dynamic libraries. These shared objects, as they are called alternatively, allow you to have a smaller program and also allow multiple programs to use a single copy of the code within the library. But how does that actually work? Most programs you will see make use of existing functionality. You don't want to always reimplement string functions or file functions. Therefore, most programs use dynamic libraries. These shared objects, as they are called alternatively, allow you to have a smaller program and also allow multiple programs to use a single copy of the code within the library. But how does that actually work?
Line 369: Line 370:
 As you can see, functions like ''puts()'', ''fgets()'', ''strlen()'' and ''strcmp()'' are not actually resolved until the first call to them is made. Make the loader resolve all the symbols at startup. (Hint: [[http://man7.org/linux/man-pages/man8/ld-linux.8.html|ld-linux(8)]]). As you can see, functions like ''puts()'', ''fgets()'', ''strlen()'' and ''strcmp()'' are not actually resolved until the first call to them is made. Make the loader resolve all the symbols at startup. (Hint: [[http://man7.org/linux/man-pages/man8/ld-linux.8.html|ld-linux(8)]]).
  
-==== Library Wrapper Task+=== Library Wrapper Task ===
  
 You've previously solved ''crackme2'' with the help of the ''ltrace''. Check out the files in the ''04-tutorial-library-dependencies/'' folder from the [[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-skel.zip|Session archive]]. The folders consists of a ''Makefile'' and a C source code file reimplementing the ''strcmp()'' function (library wrapper). The ''strcmp.c'' implementation uses ''LD_PRELOAD'' to wrap the actual ''strcmp()'' call to our own one. You've previously solved ''crackme2'' with the help of the ''ltrace''. Check out the files in the ''04-tutorial-library-dependencies/'' folder from the [[https://security.cs.pub.ro/summer-school/res/arc/01-exploration-tools-skel.zip|Session archive]]. The folders consists of a ''Makefile'' and a C source code file reimplementing the ''strcmp()'' function (library wrapper). The ''strcmp.c'' implementation uses ''LD_PRELOAD'' to wrap the actual ''strcmp()'' call to our own one.
Line 386: Line 387:
 </code> </code>
  
-=== 05. Tutorial - Network: netstat and netcat+==== 05. Tutorial - Network: netstat and netcat ====
  
 Services running on remote machines offer a gateway to those particular machines. Whether it's improper handling of the data received from clients, or a flaw in the protocol used between server and clients, certain privileges can be obtained if care is not taken. We'll explore some tools and approaches to analyzing remote services. To follow along, use the server and client programs in the crackme5 folder of the {{:session:tutorial_01.tgz|tutorial}} archive. Services running on remote machines offer a gateway to those particular machines. Whether it's improper handling of the data received from clients, or a flaw in the protocol used between server and clients, certain privileges can be obtained if care is not taken. We'll explore some tools and approaches to analyzing remote services. To follow along, use the server and client programs in the crackme5 folder of the {{:session:tutorial_01.tgz|tutorial}} archive.
Line 477: Line 478:
 </code> </code>
  
-==== Doing It in Python+=== Doing It in Python ===
  
 You can create a sever and a client in Python only. We can use the ''server.py'' and ''client.py'' scripts. Check them out first. You can create a sever and a client in Python only. We can use the ''server.py'' and ''client.py'' scripts. Check them out first.
Line 508: Line 509:
 </code> </code>
  
-==== Doing It Only with netcat+=== Doing It Only with netcat ===
  
 We can still simulate a network connection using ''netcat'' only, both for starting the server and for runing the client. We can still simulate a network connection using ''netcat'' only, both for starting the server and for runing the client.
Line 555: Line 556:
 </note> </note>
  
-=== 06. Tutorial - Open files+==== 06. Tutorial - Open files ====
  
 Let's remember how files and programs relate in Linux. Let's remember how files and programs relate in Linux.
Line 642: Line 643:
  
  
-=== Misc+==== Misc ====
  
 There are other sources of information available about running processes if you prefer to do things by hand such as: There are other sources of information available about running processes if you prefer to do things by hand such as:
Line 652: Line 653:
   * ''/proc/<PID>/cmdline'' : complete program commandline, with arguments   * ''/proc/<PID>/cmdline'' : complete program commandline, with arguments
  
-== Challenges+===== Challenges =====
  
-=== 07. Challenge - Perfect Answer+==== 07. Challenge - Perfect Answer ====
  
 For this task use the ''perfect'' binary from the 07-challenge-perfect-answer directory. For this task use the ''perfect'' binary from the 07-challenge-perfect-answer directory.
Line 660: Line 661:
 Can you find the flag? Can you find the flag?
  
-=== 08. Challenge - Lots of strings+==== 08. Challenge - Lots of strings ====
  
 Use the ''lots_of_files'' binary from ''08-challenge-lots-of-strings'' directory. Use the ''lots_of_files'' binary from ''08-challenge-lots-of-strings'' directory.
Line 669: Line 670:
 Hint: use the tools presented in the tutorials. Hint: use the tools presented in the tutorials.
 </note> </note>
-=== 09. Challenge - Sleepy cats+==== 09. Challenge - Sleepy cats ====
  
 For this task use the ''sleepy'' binary from the ''09-challenge-sleepy-cats'' directory. For this task use the ''sleepy'' binary from the ''09-challenge-sleepy-cats'' directory.
Line 681: Line 682:
  
 </note> </note>
-=== 10. Challenge - Hidden +==== 10. Challenge - Hidden  ====
  
 For this challenge use the ''hidden'' binary from the ''10-challenge-hidden/'' directory. For this challenge use the ''hidden'' binary from the ''10-challenge-hidden/'' directory.
Line 691: Line 692:
 </note> </note>
  
-=== 11. Challenge - Detective+==== 11. Challenge - Detective ====
  
 This challenge runs remotely at ''141.85.224.157:31337''. You can use ''netcat'' to connect to it. This challenge runs remotely at ''141.85.224.157:31337''. You can use ''netcat'' to connect to it.
Line 703: Line 704:
 </note> </note>
  
-==== Bonus: Get the Second Flag+=== Bonus: Get the Second Flag ===
  
 You can actually exploit the remote ''detective'' executable and get the second flag. Look thoroughly through the executable and craft your payload to exploit the remote service. You can actually exploit the remote ''detective'' executable and get the second flag. Look thoroughly through the executable and craft your payload to exploit the remote service.
Line 713: Line 714:
 </code> </code>
 </note> </note>
-=== Extra+==== Extra ====
 If you want some more, have a go at the bonus task included in the task archive. It is a simplified CTF task that you should be able to solve using the information learned in this lab. If you want some more, have a go at the bonus task included in the task archive. It is a simplified CTF task that you should be able to solve using the information learned in this lab.
  
Line 720: Line 721:
 </note> </note>
  
-=== Further pwning+==== Further pwning ====
  
 [[http://pwnable.kr/|pwnable.kr]] is a wargames site with fun challenges of different difficulty levels. After completing all tutorials and challenges in this session, you should be able to go there and try your hand at the following games from Toddler's bottle: ''fd'', ''collision'', ''bof'', ''passcode'', ''mistake'', ''cmd1'', ''blukat''. [[http://pwnable.kr/|pwnable.kr]] is a wargames site with fun challenges of different difficulty levels. After completing all tutorials and challenges in this session, you should be able to go there and try your hand at the following games from Toddler's bottle: ''fd'', ''collision'', ''bof'', ''passcode'', ''mistake'', ''cmd1'', ''blukat''.
  
session/01.1592833820.txt.gz · Last modified: 2020/06/22 16:50 by Rareş-Mihail VISALOM (67101)

Page Tools

Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Share Alike 4.0 International
CC Attribution-Share Alike 4.0 International Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki