[thread] Did you know that ssh tries to authenticate with stored keys BEFORE the key specified with -i in the command line ? I just noticed this, the hard way 😐.
Let's imagine you have more than 5 keys loaded in your ssh agent. When authenticating to a remote server, you get:
After this message, ssh tries to authenticate with the keys in the order listed above. Why is that a problem ?
Because most servers have a default configuration with MaxAuthTries set to 6. After 6 tries, you will get a "Too many authentication failures" error.
So, ssh tries to authenticate with the keys in the order listed above, but gets disconnected after 6 tries. This means that if your agent has more than 6 stored keys, the key specified with -i is never used. This means you can't login to a remote server and you might not know why
If you really want to use only your key without these default behaviors, you need to specify an option. (weird right?)
And now it works as expected. This option can also avoid generating 5 failed logins in the server logs each time you login.
It seems very strange and counterintuitive that SSH tries to authenticate with stored keys first when the user explicitly gave SSH a key to login with -i.
Let's just say that this default behavior wasted a lot of my time this weekend.
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On the left I have my attacking machine and on the right I have a Windows Server that I use as a Domain Controller.
[#thread 🧵] In the top left terminal of my attacking machine is the program to exploit this new vulnerability.
In the bottom left is Responder, a tool allowing to mimic the authentication step of many windows protocols in order to show the hashes (NTLMv1, NTLMv2, etc ...)
Simple! This tool mounts the ISO file to a temporary location, and extract the xml file [1].xml from the Windows imaging (WIM) image in ./sources/boot.wim:
[#thread 🧵] Last week in #Microsoft#PatchTuesday, a critical vulnerability was patched that theoretically allows attackers to achieve Remote Code Execution on a target #IIS server (CVE-2022-21907). I'll explain how it works in this thread ⬇️
First of all, it is important to know that this vulnerability is a sibling of CVE-2021-31166 disclosed in May of last year. These two vulnerabilities occur in the parsing of HTTP headers of an incoming request, within the http.sys driver.
To understand what happens in a kernel driver crash, It's important to analyze the kernel #crashdump generated at the moment of the blue screen! Let's open it in #WinDbg and analyze it!
[#thread 🧵] For this 23rd day of #CyberAdvent, we will talk about the LDAP structure and its naming contexts. 🦋
[#thread 🧵(2/10) ] LDAP is a directory structure (a tree) containing objects with their attributes:
[#thread 🧵(3/10) ] You can search for objects in the LDAP with a query on a specified base object and a search scope. In return, you will then get a list of matching objects with the attributes you selected.
[#thread 🧵] For this 20th day of #CyberAdvent we'll be talking about the Local Admin Password Solution #LAPS of Microsoft, and how it can be used to reduce the risk of network pivoting of attackers.
[#thread 🧵(2/6)] One of the common vulnerabilities found in Windows domains is a distributed local administrator on the workstations (sometimes even servers). This means that if an attacker compromises one machine, all the machines with the same administrator password are owned.
[#thread 🧵(3/6)] The attacker can then connect to all the other machines of the network using LM:NT hashes found on one compromised host! 😅
[#thread 🧵] For this third day of #CyberAdvent (3/24), I'll tell you a story. The story of how I gained root access to a server by leveraging a really fun feature in a web application. This #pentest#writeup will explain the complete process from recon to root. 🦋
[#thread 🧵(2/9)] In the recon phase of my pentest, as usual I was performing a port scan. In the output from nmap, I saw an uncommon port 86 with an HTTP server running "Micro Focus DSD 1.0.0":
[#thread 🧵(3/9)] When going on the page from a browser, surprise 🥳🎉 we have an unauthenticated access! This is cool, but I never saw this app before so I didn't know whether we could exploit it simply or not!