Re: Qemu User Space Binaries and Entropy

Good afternoon Peter, et.al. -

I have one more question:

Shouldn't I be able to see the "getrandom" syscall in the strace? I have attached a screenshot of the strace for where the server attempts to open urandom, random, then srandom. The left is 2.6.0 and the right is 3.1.1.1.

I appreciate your time, thanks for your help!

On Thu, Apr 9, 2020 at 11:48 AM Heather Eacmen <address@hidden> wrote:

No, that's fine. The explanation is good enough for me. I teach a reverse engineering course where we use both user space and system emulation.

When I have extra cycles, I might take a look.

Thank you!

On Thu, Apr 9, 2020 at 9:37 AM Peter Maydell <address@hidden> wrote:
On Thu, 9 Apr 2020 at 14:17, Heather Eacmen <address@hidden> wrote:
> Long story short, I'm trying to figure out why my "qemu-mipsel" (version 3.1.1.1) is able to start up SSL for my webserver, when the "qemu-mipsel" (version 2.6 and 2.11) both require the /dev/random or /dev/urandom to be created/generated.
>
> What is happening under the hood? I took a look at change logs between 2.11 and 3.1.1.1 - I could not ascertain what change could have allowed 3.1.1.1 to find entropy. I could have very well misinterpreted or misunderstood how things work.

My first guess was that this would have been when we
implemented the getrandom syscall, which allows applications
to get randomness without having to open /dev/random or
/dev/urandom. However that went in I think in 2.6, so it
can't be that.

If the answer matters to you you could run a git bisect to
find out which commit changed this behaviour.

thanks
-- PMM

--
Heather Eacmen

Tactical Network Solutions
8825 Stanford Blvd, Suite 308
Columbia, MD 21045-1832
www.tacnetsol.com

From:	Heather Eacmen
Subject:	Re: Qemu User Space Binaries and Entropy
Date:	Thu, 9 Apr 2020 12:51:38 -0400