Grade One Homework

Is an open source tool to help you build a valid SSL certificate chain from the root certificate to the end-user certificate. Also can help you fix the incomplete certificate chain and download all missing CA certificates.

How To Use
It's simple:

# Clone this repository
git clone https://github.com/trimstray/sslmerge

# Go into the repository
cd sslmerge

# Install
./setup.sh install

# Run the app
sslmerge -i /data/certs -o /data/certs/chain.crt

symlink to bin/sslmerge is placed in /usr/local/bin
man page is placed in /usr/local/man/man8

Parameters
Provides the following options:

  Usage:
    sslmerge <option|long-option>

  Examples:
    sslmerge --in Root.crt --in Intermediate1.crt --in Server.crt --out bundle_chain_certs.crt
    sslmerge --in /tmp/certs --out bundle_chain_certs.crt --with-root
    sslmerge -i Server.crt -o bundle_chain_certs.crt

  Options:
        --help        show this message
        --debug       displays information on the screen (debug mode)
    -i, --in          add certificates to merge (certificate file, multiple files or directory with ssl certificates)
    -o, --out         saves the result (chain) to file
        --with-root   add root certificate to the certificate chain

How it works
Let's start with ssllabs certificate chain. They are delivered together with the sslmerge and can be found in the example/ssllabs.com directory which additionally contains the all directory (containing all the certificates needed to assemble the chain) and the server_certificate directory (containing only the server certificate).
The correct chain for the ssllabs.com domain (the result of the openssl command):

Certificate chain
 0 s:/C=US/ST=California/L=Redwood City/O=Qualys, Inc./CN=ssllabs.com
   i:/C=US/O=Entrust, Inc./OU=See www.entrust.net/legal-terms/OU=(c) 2012 Entrust, Inc. - for authorized use only/CN=Entrust Certification Authority - L1K
 1 s:/C=US/O=Entrust, Inc./OU=See www.entrust.net/legal-terms/OU=(c) 2012 Entrust, Inc. - for authorized use only/CN=Entrust Certification Authority - L1K
   i:/C=US/O=Entrust, Inc./OU=See www.entrust.net/legal-terms/OU=(c) 2009 Entrust, Inc. - for authorized use only/CN=Entrust Root Certification Authority - G2
 2 s:/C=US/O=Entrust, Inc./OU=See www.entrust.net/legal-terms/OU=(c) 2009 Entrust, Inc. - for authorized use only/CN=Entrust Root Certification Authority - G2
   i:/C=US/O=Entrust, Inc./OU=www.entrust.net/CPS is incorporated by reference/OU=(c) 2006 Entrust, Inc./CN=Entrust Root Certification Authority

The above code presents a full chain consisting of:

Identity Certificate (Server Certificate)
issued for ssllabs.com by Entrust Certification Authority - L1K
Intermediate Certificate
issued for Entrust Certification Authority - L1K by Entrust Root Certification Authority - G2
Intermediate Certificate
issued for Entrust Root Certification Authority - G2 by Entrust Root Certification Authority
Root Certificate (Self-Signed Certificate)
issued for Entrust Root Certification Authority by Entrust Root Certification Authority

Scenario 1
In this scenario, we will chain all delivered certificates. Example of running the tool:

Scenario 2
In this scenario, we only use the server certificate and use it to retrieve the remaining required certificates. Then, as above, we will combine all the provided certificates. Example of running the tool:

Certificate chain
In order to create a valid chain, you must provide the tool with all the necessary certificates. It will be:

Server Certificate
Intermediate CAs and Root CAs

This is very important because without it you will not be able to determine the beginning and end of the chain.
However, if you look inside the generated chain after generating with sslmerge, you will not find the root certificate there. Why?
Because self-signed root certificates need not/should not be included in web server configuration. They serve no purpose (clients will always ignore them) and they incur a slight performance (latency) penalty because they increase the size of the SSL handshake.
If you want to add a root certificate to the certificate chain, call the utility with the --with-root parameter.

Certification Paths
Sslmerge allows use of two certification paths:

Output comments
When generating the chain of certificates, sslmerge displays comments with information about certificates, including any errors.
Here is a list of all possibilities:

not found identity (end-user, server) certificate
The message is displayed in the absence of a server certificate that is the beginning of the chain. This is a unique case because in this situation the sslmerge ends its operation displaying only this information. The server certificate is the only certificate required to correctly create a chain. Without this certificate, the correct chain will not be created.

found correct identity (end-user, server) certificate
The reverse situation here - message displayed when a valid server certificate is found.

not found first intermediate certificate
This message appears when the first of the two intermediate certificates is not found. This information does not explicitly specify the absence of a second intermediate certificate and on the other hand it allows to determine whether the intermediate certificate to which the server certificate was signed exists. Additionally, it can be displayed if the second intermediate certificate has been delivered.

not found second intermediate certificate
Similar to the above, however, it concerns the second intermediate certificate. However, it is possible to create the chain correctly using the second certification path, e.g. using the first intermediate certificate and replacing the second with the main certificate.

one or more intermediate certificate not found
This message means that one or all of the required intermediate certificates are missing and displayed in the absence of the root certificate.

found 'n' correct intermediate certificate(s)
This message indicates the number of valid intermediate certificates.

not found correct root certificate
The lack of the root certificate is treated as a warning. Of course, when configuring certificates on the server side, it is not recommended to attach a root certificate, but if you create it with the sslmerge, it treats the chain as incomplete displaying information about the incorrect creation of the chain.

an empty CN field was found in one of the certificates
This message does not inform about the error and about the lack of the CN field what can happen with some certificates (look at example/google.com). Common Name field identifies the host name associated with the certificate. There is no requirement in RFC3280 for an Issuer DN to have a CN. Most CAs do include a CN in the Issuer DN, but some don't, such as this Equifax CA.

Requirements
Sslmerge uses external utilities to be installed before running:

openssl

Other

Contributing
See this.

Project architecture
See this.

Download Sslmerge

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Are you tired of reading endless news stories about ethical hacking and not really knowing what that means? Let's change that!

This Post is for the people that:

Have No Experience With Cybersecurity (Ethical Hacking)
Have Limited Experience.
Those That Just Can't Get A Break

OK, let's dive into the post and suggest some ways that you can get ahead in Cybersecurity.

I receive many messages on how to become a hacker. "I'm a beginner in hacking, how should I start?" or "I want to be able to hack my friend's Facebook account" are some of the more frequent queries. Hacking is a skill. And you must remember that if you want to learn hacking solely for the fun of hacking into your friend's Facebook account or email, things will not work out for you. You should decide to learn hacking because of your fascination for technology and your desire to be an expert in computer systems. Its time to change the color of your hat 😀

I've had my good share of Hats. Black, white or sometimes a blackish shade of grey. The darker it gets, the more fun you have.

If you have no experience don't worry. We ALL had to start somewhere, and we ALL needed help to get where we are today. No one is an island and no one is born with all the necessary skills. Period.OK, so you have zero experience and limited skills…my advice in this instance is that you teach yourself some absolute fundamentals.

Let's get this party started.

What is hacking?

Hacking is identifying weakness and vulnerabilities of some system and gaining access with it.

Hacker gets unauthorized access by targeting system while ethical hacker have an official permission in a lawful and legitimate manner to assess the security posture of a target system(s)

There's some types of hackers, a bit of "terminology".
White hat — ethical hacker.
Black hat — classical hacker, get unauthorized access.
Grey hat — person who gets unauthorized access but reveals the weaknesses to the company.
Script kiddie — person with no technical skills just used pre-made tools.
Hacktivist — person who hacks for some idea and leaves some messages. For example strike against copyright.

Skills required to become ethical hacker.

Curosity anf exploration
Operating System
Fundamentals of Networking

*Note this sites

More info

There are many goodware and malware developed in pascal, and we will see that the binary generated by the pascal compilers is fascinating, not only because the small and clean generated binaries, or the clarity of the pascal code, but also the good performance. In Linux we have Lazarus which is a good free IDE like Delphi and Kylix the free pascal IDE for windows.

The program:

program strtest;

var
cstr: array[0..10] of char;
s, s2: ShortString;

begin
cstr := 'hello world';
s := cstr;
s2 := 'test';

WriteLn(cstr + ' ' + s + ' ' + s2);
end.

We are going to compile it with freepascal and lazarus, and just the binary size differs a lot:

lazarus 242,176 btytes 845 functions
freepascal 32,256 bytes 233 functions
turbopascal 2,928 bytes 80 functions (wow)

And surprisingly turbopascal binaries are extremely light.
Lets start with lazarus:

Logically it imports from user32.dll some display functions, it also import the kernel32.dll functions and suspiciously the string operations of oleaut32.dll

And our starting point is a function called entry that calls the console initialization and retrieve some console configurations, and then start a labyrinth of function calls.

On functions 10000e8e0 there is the function that calls the main function.

I named execute_param2 because the second param is a function pointer that is gonna be executed without parameters, it sounds like main calling typical strategy.
And here we are, it's clearly the user code pascal main function.

What it seems is that function 100001800 returns an string object, then is called its constructor to initialize the string, then the string is passed to other functions that prints it to the screen.

This function executes the method 0x1c0 of the object until the byte 0x89 is a null byte.
What the hell is doing here?
First of all let's create the function main:

Simply right button create function:

After a bit of work on Ghidra here we have the main:

Note that the struct member so high like 0x1b0 are not created by default, we should import a .h file with an struct or class definition, and locate the constructor just on that position.

The mysterious function was printing byte a byte until null byte, the algorithm the compiler implemented in asm is not as optimized as turbopascal's.

In Windbg we can see the string object in eax after being created but before being initialized:

Just before executing the print function, the RCX parameter is the string object and it still identical:

Let's see the constructor code.
The constructor address can be guessed on static walking the reverse-cross-references to main, but I located it in debugging it in dynamic analysis.

The constructor reads only a pointer stored on the string object on the position 0x98.

And we have that the pointer at 0x98 is compared with the address of the literal, so now we know that this pointer points to the string.
The sentence *string_x98 = literal confirms it, and there is not memory copy, it only points reusing the literal.

Freepascal

The starting labyrinth is bigger than Lazarus so I had to begin the maze from the end, searching the string "hello world" and then finding the string references:

There are two ways to follow the references in Ghidra, one is [ctrl] + [shift] + F but there is other trick which is simply clicking the green references texts on the disassembly.

At the beginning I doubted and put the name possible_main, but it's clearly the pascal user code main function.

The char array initialization Is converted by freepascal compiler to an runtime initialization using mov instructions.

Reducing the coverage on dynamic we arrive to the writeln function:

EAX helds a pointer to a struct, and the member 0x24 performs the printing. In this cases the function can be tracked easily in dynamic executing the sample.

And lands at 0x004059b0 where we see the WriteFile, the stdout descriptor, the text and the size supplied by parameter.

there is an interesting logic of what happens if WriteFile() couldn't write all the bytes, but this is other scope.
Lets see how this functions is called and how text and size are supplied to figure out the string object.

EBX helds the string object and there are two pointers, a pointer to the string on 0x18 and the length in 0x18, lets verify it on windbg.

And here we have the string object, 0x0000001e is the length, and 0x001de8a68 is the pointer.

Thanks @capi_x for the pascal samples.

Grade One Homework

Saturday, August 29, 2020

Sslmerge - Tool To Help You Build A Valid SSL Certificate Chain From The Root Certificate To The End-User Certificate

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How To Start | How To Become An Ethical Hacker

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Freepascal

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