pg_logicalinspect: Fix possible crash when passing a directory path.

Previously, pg_logicalinspect functions were too trusting of their
input and blindly passed it to SnapBuildRestoreSnapshot(). If the
input pointed to a directory, the server could a PANIC error while
attempting to fsync_fname() with isdir=false on a directory.

This commit adds validation checks for input filenames and passes the
LSN extracted from the filename to SnapBuildRestoreSnapshot() instead
of the filename itself. It also adds regression tests for various
input patterns and permission checks.

Bug: #18828
Reported-by: Robins Tharakan <tharakan@gmail.com>
Co-authored-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Co-authored-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/18828-0f4701c635064211@postgresql.org

1 files changed, 48 insertions, 0 deletions

diff --git a/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql b/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql
new file mode 100644
index 00000000000..143cf45dc12
--- /dev/null
+++ b/contrib/pg_logicalinspect/sql/pg_logicalinspect.sql
@@ -0,0 +1,48 @@
+CREATE EXTENSION pg_logicalinspect;
+
+-- ===================================================================
+-- Tests for input validation
+-- ===================================================================
+
+SELECT pg_get_logical_snapshot_info('0-40796E18.foo');
+SELECT pg_get_logical_snapshot_info('0--40796E18.snap');
+SELECT pg_get_logical_snapshot_info('-1--40796E18.snap');
+SELECT pg_get_logical_snapshot_info('0/40796E18.foo.snap');
+SELECT pg_get_logical_snapshot_info('0/40796E18.snap');
+SELECT pg_get_logical_snapshot_info('');
+SELECT pg_get_logical_snapshot_info(NULL);
+SELECT pg_get_logical_snapshot_info('../snapshots');
+SELECT pg_get_logical_snapshot_info('../snapshots/0-40796E18.snap');
+
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo');
+SELECT pg_get_logical_snapshot_meta('0-40796E18.foo.snap');
+SELECT pg_get_logical_snapshot_meta('0/40796E18.snap');
+SELECT pg_get_logical_snapshot_meta('');
+SELECT pg_get_logical_snapshot_meta(NULL);
+SELECT pg_get_logical_snapshot_meta('../snapshots');
+
+-- ===================================================================
+-- Tests for permissions
+-- ===================================================================
+CREATE ROLE regress_pg_logicalinspect;
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- no
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- no
+
+-- Functions accessible by users with role pg_read_server_files.
+GRANT pg_read_server_files TO regress_pg_logicalinspect;
+
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_info(text)', 'EXECUTE'); -- yes
+SELECT has_function_privilege('regress_pg_logicalinspect',
+  'pg_get_logical_snapshot_meta(text)', 'EXECUTE'); -- yes
+
+-- ===================================================================
+-- Clean up
+-- ===================================================================
+
+DROP ROLE regress_pg_logicalinspect;
+
+DROP EXTENSION pg_logicalinspect;