[yocto] Set linux capabilities on binary on a recipe in meta-oe layer

[Piotr Tworek]

Hi Markus,

Have you tried doing it in the postinst step executed on your target? Try:

pkg_postinst_ontarget_${PN} () {
    setcap cap_net_raw+eip $D${bindir}/node
}

RDEPENDS_${PN} += "libcap-bin"

/ptw

> I have tested to set capabilities on the node binary within a custom recipe
> (custom layer) but that failed.
> 
> pkg_postinst_${PN} () {
>     setcap cap_net_raw+eip $D${bindir}/node
> }
> PACKAGE_WRITE_DEPS = "libcap-native"
> RDEPENDS_${PN} = "libcap"
> 
> The error message:
> 
> ERROR: core-image-full-cmdline-1.0-r0 do_rootfs: [log_check]
> core-image-full-cmdline: found 1 error message in the logfile:
> [log_check] Failed to set capabilities on file
> `/home/ubuntu/yocto-sumo/build/tmp/work/raspberrypi3-poky-linux-gnueabi/core
> -image-full-cmdline/1.0-r0/rootfs/usr/bin/node' (No such file or directory)
> 
> When I check the node binary is there in the rootfs directory. It seems
> that when the the pkg_postinst function is executed the node binary is not
> there.
> 
> What am I missing? Any answer is much appreciated!
> 
> Regards,
> Markus
> 
> On Wed, 7 Nov 2018 at 11:32, Markus W <markus4dev at gmail.com> wrote:
> > Hi!
> > 
> > Background:
> > In my raspberry project I am developing a nodejs app that needs access to
> > bluetooth/ble device. I want to run the node application as non root user
> > for security reasons. In order to get access from within the app, the node
> > binary need to have the following capability cap_net_raw+eip set. I am
> > using the nodejs recipe from meta-oe and added it in my local.conf:
> > 
> > IMAGE_INSTALL_append = " nodejs i2c-tools bluez5 kernel-image
> > kernel-devicetree"
> > 
> > Question:
> > Where should I apply the following command? setcap cap_net_raw+eip
> > /usr/bin/node
> > 
> > What are my options? Can I create a recipe in a different package that
> > will apply the above command on the meta-oe package for the nodejs recipe?
> > 
> > I have been following this thread (
> > https://lists.yoctoproject.org/pipermail/yocto/2016-June/030811.html),
> > but the node binaries and my node-app are in different layers and
> > packages.
> > 
> > Any advice how to do this is much appreciated?
> > 
> > Regards,
> > Markus