pgsql: Update sepgsql to add mandatory access control for TRUNCATE

Update sepgsql to add mandatory access control for TRUNCATE

Use SELinux "db_table: { truncate }" to check if permission is granted to
TRUNCATE. Update example SELinux policy to grant needed permission for
TRUNCATE. Add new regression test to demonstrate a positive and negative
cases. Test will only be run if the loaded SELinux policy has the
"db_table: { truncate }" permission. Makes use of recent commit which added
object TRUNCATE hook. Patch by Yuli Khodorkovskiy with minor
editorialization by me. Not back-patched because the object TRUNCATE hook
was not.

Author: Yuli Khodorkovskiy
Reviewed-by: Joe Conway
Discussion: https://postgr.es/m/CAFL5wJcomybj1Xdw7qWmPJRpGuFukKgNrDb6uVBaCMgYS9dkaA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4f66c93f61439b4db866b21cc1ecd5bf815564ef

Modified Files
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contrib/sepgsql/expected/truncate.out | 46 +++++++++++++++++++++++++++++++++++
contrib/sepgsql/hooks.c | 14 +++++++++++
contrib/sepgsql/relation.c | 40 ++++++++++++++++++++++++++++++
contrib/sepgsql/selinux.c | 3 +++
contrib/sepgsql/sepgsql-regtest.te | 8 ++++++
contrib/sepgsql/sepgsql.h | 2 ++
contrib/sepgsql/sql/truncate.sql | 24 ++++++++++++++++++
contrib/sepgsql/test_sepgsql | 16 +++++++++++-
8 files changed, 152 insertions(+), 1 deletion(-)