Add pg_get_acl() to get the ACL for a database object

This function returns the ACL for a database object, specified by
catalog OID and object OID.  This is useful to be able to
retrieve the ACL associated to an object specified with a
(class_id,objid) couple, similarly to the other functions for object
identification, when joined with pg_depend or pg_shdepend.

Original idea by Álvaro Herrera.

Bump catalog version.

Author: Joel Jacobson
Reviewed-by: Isaac Morland, Michael Paquier, Ranier Vilela
Discussion: https://postgr.es/m/80b16434-b9b1-4c3d-8f28-569f21c2c102@app.fastmail.com

5 files changed, 89 insertions, 1 deletions

diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 7b536ac6fde..2983b9180fc 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -4363,6 +4363,54 @@ pg_identify_object_as_address(PG_FUNCTION_ARGS)
 }
 
 /*
+ * SQL-level callable function to obtain the ACL of a specified object, given
+ * its catalog OID and object OID.
+ */
+Datum
+pg_get_acl(PG_FUNCTION_ARGS)
+{
+	Oid			classId = PG_GETARG_OID(0);
+	Oid			objectId = PG_GETARG_OID(1);
+	Oid			catalogId;
+	AttrNumber	Anum_acl;
+	Relation	rel;
+	HeapTuple	tup;
+	Datum		datum;
+	bool		isnull;
+
+	/* for "pinned" items in pg_depend, return null */
+	if (!OidIsValid(classId) && !OidIsValid(objectId))
+		PG_RETURN_NULL();
+
+	/* for large objects, the catalog to look at is pg_largeobject_metadata */
+	catalogId = (classId == LargeObjectRelationId) ?
+		LargeObjectMetadataRelationId : classId;
+	Anum_acl = get_object_attnum_acl(catalogId);
+
+	/* return NULL if no ACL field for this catalog */
+	if (Anum_acl == InvalidAttrNumber)
+		PG_RETURN_NULL();
+
+	rel = table_open(catalogId, AccessShareLock);
+
+	tup = get_catalog_object_by_oid(rel, get_object_attnum_oid(catalogId),
+									objectId);
+	if (!HeapTupleIsValid(tup))
+	{
+		table_close(rel, AccessShareLock);
+		PG_RETURN_NULL();
+	}
+
+	datum = heap_getattr(tup, Anum_acl, RelationGetDescr(rel), &isnull);
+	table_close(rel, AccessShareLock);
+
+	if (isnull)
+		PG_RETURN_NULL();
+
+	PG_RETURN_DATUM(datum);
+}
+
+/*
  * Return a palloc'ed string that describes the type of object that the
  * passed address is for.
  *
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 969980afd69..be13e09fba3 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202407012
+#define CATALOG_VERSION_NO	202407041
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index d4ac578ae64..e1001a4822e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6362,6 +6362,11 @@
   proname => 'pg_describe_object', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid oid int4', prosrc => 'pg_describe_object' },
 
+{ oid => '6347', descr => 'get ACL for SQL object',
+  proname => 'pg_get_acl', provolatile => 's', prorettype => '_aclitem',
+  proargtypes => 'oid oid', proargnames => '{classid,objid}',
+  prosrc => 'pg_get_acl' },
+
 { oid => '3839',
   descr => 'get machine-parseable identification of SQL object',
   proname => 'pg_identify_object', provolatile => 's', prorettype => 'record',
diff --git a/src/test/regress/expected/privileges.out b/src/test/regress/expected/privileges.out
index eb4b762ea10..332bc584eb2 100644
--- a/src/test/regress/expected/privileges.out
+++ b/src/test/regress/expected/privileges.out
@@ -213,10 +213,39 @@ SELECT * FROM atest1;
 (0 rows)
 
 CREATE TABLE atest2 (col1 varchar(10), col2 boolean);
+SELECT pg_get_acl('pg_class'::regclass, 'atest2'::regclass::oid);
+ pg_get_acl 
+------------
+ 
+(1 row)
+
 GRANT SELECT ON atest2 TO regress_priv_user2;
 GRANT UPDATE ON atest2 TO regress_priv_user3;
 GRANT INSERT ON atest2 TO regress_priv_user4 GRANTED BY CURRENT_USER;
 GRANT TRUNCATE ON atest2 TO regress_priv_user5 GRANTED BY CURRENT_ROLE;
+SELECT unnest(pg_get_acl('pg_class'::regclass, 'atest2'::regclass::oid));
+                     unnest                     
+------------------------------------------------
+ regress_priv_user1=arwdDxtm/regress_priv_user1
+ regress_priv_user2=r/regress_priv_user1
+ regress_priv_user3=w/regress_priv_user1
+ regress_priv_user4=a/regress_priv_user1
+ regress_priv_user5=D/regress_priv_user1
+(5 rows)
+
+-- Invalid inputs
+SELECT pg_get_acl('pg_class'::regclass, 0); -- null
+ pg_get_acl 
+------------
+ 
+(1 row)
+
+SELECT pg_get_acl(0, 0); -- null
+ pg_get_acl 
+------------
+ 
+(1 row)
+
 GRANT TRUNCATE ON atest2 TO regress_priv_user4 GRANTED BY regress_priv_user5;  -- error
 ERROR:  grantor must be current user
 SET SESSION AUTHORIZATION regress_priv_user2;
diff --git a/src/test/regress/sql/privileges.sql b/src/test/regress/sql/privileges.sql
index eeb4c002926..980d19bde56 100644
--- a/src/test/regress/sql/privileges.sql
+++ b/src/test/regress/sql/privileges.sql
@@ -183,10 +183,16 @@ GRANT SELECT ON atest1 TO regress_priv_user3, regress_priv_user4;
 SELECT * FROM atest1;
 
 CREATE TABLE atest2 (col1 varchar(10), col2 boolean);
+SELECT pg_get_acl('pg_class'::regclass, 'atest2'::regclass::oid);
 GRANT SELECT ON atest2 TO regress_priv_user2;
 GRANT UPDATE ON atest2 TO regress_priv_user3;
 GRANT INSERT ON atest2 TO regress_priv_user4 GRANTED BY CURRENT_USER;
 GRANT TRUNCATE ON atest2 TO regress_priv_user5 GRANTED BY CURRENT_ROLE;
+SELECT unnest(pg_get_acl('pg_class'::regclass, 'atest2'::regclass::oid));
+
+-- Invalid inputs
+SELECT pg_get_acl('pg_class'::regclass, 0); -- null
+SELECT pg_get_acl(0, 0); -- null
 
 GRANT TRUNCATE ON atest2 TO regress_priv_user4 GRANTED BY regress_priv_user5;  -- error