[RFC PATCH 0/1] libselinux: Save digest of all partial matches for directory

[Richard Haines <richard_c_haines@btinternet.com>]

This patch requires that patch [1] be installed first. [1] has been
implemented on Android and was sent to the selinux list, however its
merge has been defered. It will install the core hashing of file_context
entries.

This patch updates selinux_restorecon() replacing the per-mountpoint
security.restorecon_last attribute with a per-directory security.sehash
attribute computed from only those file contexts entries that partially
match the directory. This is to avoid the need to walk the entire tree
when any part of file_contexts changes, limiting relabels to only those
parts of the tree that could have changed.

One change is to add a new selabel_get_digests_all_partial_matches(3)
function that is explained in the man page. This could replace the Android
version of selabel_hash_all_partial_matches(3), that could then be
converted into a local function.

I've not updated restorecon(8) or restorecon_xattr(8) programs as they
work okay (although I could rework the "selabel_opt_digest" stuff). However
the man pages at least will need updating.

The patch still needs more testing (I've not tried all restorecon options),
however I will send a patch for the selinux-testsuite that will perform
some simple tests on the new code.
 
[1] https://lore.kernel.org/selinux/20190311222442.49824-1-xunchang@google.com/

Richard Haines (1):
  libselinux: Save digest of all partial matches for directory

 libselinux/include/selinux/label.h            |   5 +
 .../selabel_get_digests_all_partial_matches.3 |  69 ++++++
 libselinux/src/label.c                        |  15 ++
 libselinux/src/label_file.c                   |  51 +++++
 libselinux/src/label_file.h                   |   4 +
 libselinux/src/label_internal.h               |   5 +
 libselinux/src/selinux_restorecon.c           | 204 +++++++++++++-----
 libselinux/utils/.gitignore                   |   2 +
 .../selabel_get_digests_all_partial_matches.c | 171 +++++++++++++++
 .../utils/selabel_hash_all_partial_matches.c  | 126 +++++++++++
 10 files changed, 595 insertions(+), 57 deletions(-)
 create mode 100644 libselinux/man/man3/selabel_get_digests_all_partial_matches.3
 create mode 100644 libselinux/utils/selabel_get_digests_all_partial_matches.c
 create mode 100644 libselinux/utils/selabel_hash_all_partial_matches.c

-- 
2.20.1