Can process ram be secured?

Stuffe · 01-30-2015, 04:46 PM

I would like to run a service that relies on a secret key that I really do not want to fall into the hands of hackers. That would be a complete disaster really. I am not a Linux export so this might be dumb, but this is my idea:
Have a program load the secret key from a file and into a variable (ram) and then (thoroughly) delete the file. The program would never stop running and if it did, I would have to copy the key to the server again from offline storage. But is there a way to have kernel level protection of process ram, so that no other process can read it?
The reason why I like the idea of storing it in ram is that if the computer is turned off, the data becomes unrecoverable after only a few seconds.

Again, I don't know if this is dumb. What do you guys think?

metaschima · 01-30-2015, 04:58 PM

I know libgcrypt supports secure memory:

Quote:

Libgcrypt uses a concept known as secure memory, which is a region of memory set aside for storing sensitive data. Because such memory is a scarce resource, it needs to be setup in advanced to a fixed size. Further, most operating systems have special requirements on how that secure memory can be used. For example, it might be required to install an application as “setuid(root)” to allow allocating such memory. Libgcrypt requires a sequence of initialization steps to make sure that this works correctly. The following examples show the necessary steps.

https://www.gnupg.org/documentation/...ng-the-library

You could for example use the 'gcry_malloc_secure' function to allocate secure memory.

cepheus11 · 01-30-2015, 05:10 PM

Quote:

Originally Posted by Stuffe

Have a program load the secret key from a file and into a variable (ram) and then (thoroughly) delete the file.

Why would the key be in a file in the first place? If the key has been on an unencrypted disk at some point in time, you already lost: The filesystem driver might move the file around for performance/resources/load balancing/fragmentation reasons and not sanitize the old version, and modern filesystems have a journal which contains traces of previous file operations. Do NOT allow key data to get on disk!

Persistent encryption systems work with a container header which is used to calculate the key with data provided from user-supplied password(s) and/or keyfile(s). In linux, the software is called cryptsetup-LUKS. Use it, instead of writing your own. If you are not a real security genius, chances are that your own software forgets to secure data from being written to disk (think swap...).

veerain · 01-30-2015, 10:31 PM

In linux in a c program you can lock a part of memory or whole process memory(If it is small or your are root) using mlock and mlockall functions. Then after using that memory you have to zero out it. Them unlock them. This function prevents the kernel from swapping the memory to swap also.

Stuffe · 01-31-2015, 01:20 PM

Thank you for the feedback guys. I will keep these things in mind. veerain, couldn't you theoretically just DLL inject into the program ram space though?