kbx: Redefine the UBID which is now the primary fingerprint.
* common/util.h (UBID_LEN): New. Use it at all places. * kbx/keybox-blob.c (create_blob_finish): Do not write the UBID item. * kbx/keybox-dump.c (print_ubib): Remove. (_keybox_dump_blob): Do not print the now removed ubid flag. * kbx/keybox-search-desc.h (struct keydb_search_desc): Use constants for the size of the ubid and grip. * kbx/keybox-search.c (blob_cmp_ubid): New. (has_ubid): Make it a simple wrapper around blob_cmp_ubid. (keybox_get_data): Add arg 'r_ubid'. * kbx/frontend.h (enum kbxd_store_modes): New. * kbx/kbxserver.c (cmd_store): Add new option --insert. * kbx/backend-cache.c (be_cache_initialize): New. (be_cache_add_resource): Call it here. * kbx/backend-kbx.c (be_kbx_seek): Remove args 'fpr' and 'fprlen'. (be_kbx_search): Get the UBID from keybox_get_data. * kbx/backend-support.c (be_fingerprint_from_blob): Replace by ... (be_ubid_from_blob): new. Change all callers. * kbx/frontend.c (kbxd_add_resource): Temporary disable the cache but use the new cache init function. (kbxd_store): Replace arg 'only_update' by 'mode'. Seek using the ubid. Take care of the mode.
It turned out that using the hash of the entire blob was not helpful.
Thus we redefine the Unique-Blob-ID (UBID) as the primary fingerprint
of the blob. In case this is a v5 OpenPGP key a left truncated
version of the SHA-256 hash is used; in all other cases the full SHA-1
hash. Using a SHA-256 hash does not make sense because v4 keys are
and will for some time be the majority of keys and thus padding them
with zeroes won't make any difference. Even if fingerprint collisions
can eventually be created we will assume that the keys are bogus and
that it does not make sense to store its twin also in our key storage.
We can also easily extend the update code to detect a collision and
reject the update.
- Signed-off-by: Werner Koch <firstname.lastname@example.org>