Messages in this thread | | | Subject | Re: [PATCH v4 0/3] initramfs: add support for xattrs in the initial ram disk | From | Roberto Sassu <> | Date | Mon, 15 Jul 2019 18:54:12 +0200 |
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Rob, Peter, Arvind, did you have the chance to have a look at this version of the patch set?
Thanks
Roberto
On 7/1/2019 4:31 PM, Mimi Zohar wrote: > On Mon, 2019-07-01 at 16:42 +0300, Roberto Sassu wrote: >> On 6/30/2019 6:39 PM, Mimi Zohar wrote: >>> On Wed, 2019-06-26 at 10:15 +0200, Roberto Sassu wrote: >>>> On 6/3/2019 8:32 PM, Rob Landley wrote: >>>>> On 6/3/19 4:31 AM, Roberto Sassu wrote: >>>>>>> This patch set aims at solving the following use case: appraise files from >>>>>>> the initial ram disk. To do that, IMA checks the signature/hash from the >>>>>>> security.ima xattr. Unfortunately, this use case cannot be implemented >>>>>>> currently, as the CPIO format does not support xattrs. >>>>>>> >>>>>>> This proposal consists in including file metadata as additional files named >>>>>>> METADATA!!!, for each file added to the ram disk. The CPIO parser in the >>>>>>> kernel recognizes these special files from the file name, and calls the >>>>>>> appropriate parser to add metadata to the previously extracted file. It has >>>>>>> been proposed to use bit 17:16 of the file mode as a way to recognize files >>>>>>> with metadata, but both the kernel and the cpio tool declare the file mode >>>>>>> as unsigned short. >>>>>> >>>>>> Any opinion on this patch set? >>>>>> >>>>>> Thanks >>>>>> >>>>>> Roberto >>>>> >>>>> Sorry, I've had the window open since you posted it but haven't gotten around to >>>>> it. I'll try to build it later today. >>>>> >>>>> It does look interesting, and I have no objections to the basic approach. I >>>>> should be able to add support to toybox cpio over a weekend once I've got the >>>>> kernel doing it to test against. >>>> >>>> Ok. >>>> >>>> Let me give some instructions so that people can test this patch set. >>>> >>>> To add xattrs to the ram disk embedded in the kernel it is sufficient >>>> to set CONFIG_INITRAMFS_FILE_METADATA="xattr" and >>>> CONFIG_INITRAMFS_SOURCE="<file with xattr>" in the kernel configuration. >>>> >>>> To add xattrs to the external ram disk, it is necessary to patch cpio: >>>> >>>> https://github.com/euleros/cpio/commit/531cabc88e9ecdc3231fad6e4856869baa9a91ef >>>> (xattr-v1 branch) >>>> >>>> and dracut: >>>> >>>> https://github.com/euleros/dracut/commit/a2dee56ea80495c2c1871bc73186f7b00dc8bf3b >>>> (digest-lists branch) >>>> >>>> The same modification can be done for mkinitramfs (add '-e xattr' to the >>>> cpio command line). >>>> >>>> To simplify the test, it would be sufficient to replace only the cpio >>>> binary and the dracut script with the modified versions. For dracut, the >>>> patch should be applied to the local dracut (after it has been renamed >>>> to dracut.sh). >>>> >>>> Then, run: >>>> >>>> dracut -e xattr -I <file with xattr> (add -f to overwrite the ram disk) >>>> >>>> Xattrs can be seen by stopping the boot process for example by adding >>>> rd.break to the kernel command line. >>> >>> A simple way of testing, without needing any changes other than the >>> kernel patches, is to save the dracut temporary directory by supplying >>> "--keep" on the dracut command line, calling >>> usr/gen_initramfs_list.sh, followed by usr/gen_init_cpio with the "-e >>> xattr" option. >> >> Alternatively, follow the instructions to create the embedded ram disk >> with xattrs, and use the existing external ram disk created with dracut >> to check if xattrs are created. > > True, but this alternative is for those who normally use dracut to > create an initramfs, but don't want to update cpio or dracut. > > Mimi >
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