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It was reported in the #grub IRC channel on Libera that decryption of LUKS2 partitions fails with errors about invalid digests and/or salts. In all of these cases, what failed was decoding the Base64 representation of these, where the encoded data contained invalid characters. As it turns out, the root cause is that json-c, which is used by cryptsetup to read and write the JSON header, will escape some characters by prepending a backslash when writing JSON strings by default. Most importantly, json-c also escapes the forward slash, which is part of the Base64 alphabet. Because GRUB doesn't know to unescape such characters, decoding this string will rightfully fail. Interestingly, this issue has until now only been reported by users of Ubuntu 18.04. And a bit of digging in fact reveals that cryptsetup has changed the logic in a054206d (Suppress useless slash escaping in json lib, 2018-04-20), which has been released with cryptsetup v2.0.3. Ubuntu 18.04 is still shipping with cryptsetup v2.0.2 though, which explains why this is not a more frequent issue. Fix the issue by using our new grub_json_unescape() helper function that handles unescaping for us. Reported-by: Afdal Signed-off-by: Patrick Steinhardt <ps@pks.im> Reviewed-by: Daniel Kiper <dkiper@net-space.pl>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'