Packer needs qemu-img

[M3noetius]

Good afternoon,

In order to compile QEMU-NYX the --disable--tools is disabled [here].

Am I suppose to go to QEMU-nyx master [here] and compile the tool ?
I see that the changes are at the "block-backend.c" and I guess this will have an affect on the image used. [here] [git_blame]

~/kAFL/kafl/examples/templates/windows$ make build 
make[1]: Entering directory '/home/user/kAFL/kafl/examples/templates/windows'
packer init windows.pkr.hcl
source /home/user/kAFL/kafl/examples/templates/windows/../../venv/bin/activate && packer build -var-file win10.pkrvars.hcl windows.pkr.hcl
qemu.windows: output will be in this color.

Build 'qemu.windows' errored after 571 microseconds: Failed creating Qemu driver: exec: "qemu-img": executable file not found in $PATH

==> Wait completed after 600 microseconds

==> Some builds didn't complete successfully and had errors:
--> qemu.windows: Failed creating Qemu driver: exec: "qemu-img": executable file not found in $PATH

Thank you

[Wenzel]

Hi @M3noetius and thank you for opening an issue.

I wasn't aware of the problem you are reporting, since I'm simply relying on the system package to get qemu-img tool, from /usr/bin/qemu-img (qemu-system-x86 package).

I'm not fully understanding all the QEMU-Nyx modifications at this stage.
However, the BlockBackend struct seems to be defined when QEMU_NYX is undefined.

#ifndef QEMU_NYX
struct BlockBackend {
    char *name;
    int refcnt;
    BdrvChild *root;

and judging from the blk_new functions, the only field added by Nyx is the cow_cache:
https://github.com/nyx-fuzz/QEMU-Nyx/blob/qemu-nyx-4.2.0/block/block-backend.c#L345

In any case, Packer and the Windows template here isn't configured to use the QEMU-Nyx binary that you built previously.
In fact, the PATH hasn't been modified to include kafl/kafl/qemu/x86_64-softmmu/qemu-system-x86_64.

So in my case, I also the system packaged QEMU to build the Windows template, and then fuzz it with QEMU-Nyx, doesn't seem to be a problem.

@il-steffen can you shed some lights regarding the block-backend.c modifications, and whether they are relevant for QEMU images being built ?

[Wenzel]

Closed by #234