Administrativa

As I've mentioned to a few people, the past two posts have been the start of what I hope will become a trend: posting at least one piece of new, technically interesting content per week. With any luck, new posts will come out on Mondays (I cheated a bit this week and took Labor Day off).

Topics covered will center around memory analysis, as this is my primary area of research, but I have a few posts planned on topics like network-based exploitation and cryptography.

I hope any readers of this blog will enjoy the sudden influx of new content; don't hesitate to contact me with comments, criticisms, or ideas for new posts.

Comments

Post a Comment

Popular posts from this blog

Someone’s Been Messing With My Subnormals!

Image
TL;DR: After noticing an annoying warning, I went on an absurd yak shave, and discovered that because of a tiny handful of Python packages built with an appealing-sounding but dangerous compiler option, more than 2,500 Python packages—some with more than a million downloads per month—could end up causing any program that uses them to compute incorrect numerical results. Once Upon a Time in My Terminal Recently, whenever I tried to import certain Python packages (notably, some models from Huggingface Transformers), I would see this weird and unsightly warning: Python 3.8.10 (default, Jun 22 2022, 20:18:18)   Type 'copyright', 'credits' or 'license' for more information IPython 8.4.0 -- An enhanced Interactive Python. Type '?' for help. In [ 1 ]: from transformers import CodeGenForCausalLM /home/moyix/.virtualenvs/sfcodegen/lib/python3.8/site-packages/numpy/core/getlimits.py:498: UserWarning: The value of the smallest subnormal for <class 'numpy....
Read more

Decrypting LSA Secrets

The LSA secrets store is a protected storage area used the the Local Security Authority (LSA) system in Windows to keep important pieces of information safe from prying eyes. As with Syskey, however, we will see that these secrets are only obfuscated, and once the mechanism is known, we can extract them from the registry with ease. Even without knowing the obfuscation algorithm, however, it is possible to read the values of this data using the LsarQuerySecret function exported by lsasrv.dll, but only if one has the LocalSystem privilege (for example, if the process is running under the SYSTEM account). What kind of data is stored in these secrets? Here are a few that I've come across: $MACHINE.ACC : has to do with domain authentication, see KB175468 DefaultPassword : password used to logon to Windows if auto-logon is enabled NL$KM : secret key used to encrypt cached domain passwords L$RTMTIMEBOMB_[...] : FILETIME giving the date when an unactivated copy of Windows w...
Read more

SysKey and the SAM

The Security Accounts Manager The Security Accounts Manager , or SAM, has been used by Windows since the days of NT to store information on local user accounts (or, in the case of a domain controller, the accounts for all users on the domain). It takes the form of a registry hive, and is stored in %WINDIR%\system32\config . Generally, two types of hash are stored in the SAM: the LanMan hash and the NT hash. The LanMan hash has many flaws: It is not salted, and is thus vulnerable to precomputed dictionary attacks such as rainbow tables . The hash is split into two 7-byte pieces, which allows attacks to be performed against each piece at the same time. This also means that if the password is shorter than 7 characters, the last half of the hash will be a constant value. The password is converted to uppercase before hashing, which reduces the keyspace. The LM hash is computed by padding or truncating the password to 14 characters, splitting it into two halves, and then usin...
Read more