A function to get the current master key info. (#150)

* A function to get the current master key info.

Commit adds tde_master_key_info() function that returns
the information about the master key for the database.

SELECT * FROM tde_master_key_info();
-[ RECORD 1 ]------------+------------------------------
master_key_name          | test-db-master-key
key_provider_name        | file-vault
key_provider_id          | 1
master_key_internal_name | test-db-master-key_7
master_key_version       | 7
key_createion_time       | 2024-03-26 22:28:20.998034+05

expected/pgtde_is_encrypted.out

@@ -1,4 +1,7 @@
 CREATE EXTENSION pg_tde;
+SELECT  * FROM tde_master_key_info();
+ERROR:  Master key does not exists for the database
+HINT:  Use set_master_key interface to set the master key
 SELECT pg_tde_add_key_provider_file('file-vault','/tmp/pg_tde_test_keyring.per');
  pg_tde_add_key_provider_file 
 ------------------------------
@@ -45,6 +48,13 @@ SELECT pgtde_is_encrypted('test_norm');
  f
 (1 row)
 
+SELECT  key_provider_id, key_provider_name, master_key_name
+		FROM tde_master_key_info();
+ key_provider_id | key_provider_name |  master_key_name   
+-----------------+-------------------+--------------------
+               1 | file-vault        | test-db-master-key
+(1 row)
+
 DROP TABLE test_enc;
 DROP TABLE test_norm;
 DROP EXTENSION pg_tde;

pg_tde--1.0.sql

@@ -113,6 +113,15 @@ RETURNS VOID
 AS 'MODULE_PATHNAME'
 LANGUAGE C;
 
+CREATE FUNCTION tde_master_key_info()
+RETURNS TABLE ( master_key_name text,
+                key_provider_name text,
+                key_provider_id integer,
+                master_key_internal_name text,
+                master_key_version integer,
+                key_createion_time timestamp with time zone)
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
 
 -- Access method
 CREATE ACCESS METHOD pg_tde TYPE TABLE HANDLER pg_tdeam_handler;

sql/pgtde_is_encrypted.sql

@@ -1,5 +1,7 @@
 CREATE EXTENSION pg_tde;
 
+SELECT  * FROM tde_master_key_info();
+
 SELECT pg_tde_add_key_provider_file('file-vault','/tmp/pg_tde_test_keyring.per');
 SELECT pg_tde_set_master_key('test-db-master-key','file-vault');
 
@@ -21,6 +23,9 @@ SELECT amname FROM pg_class INNER JOIN pg_am ON pg_am.oid = pg_class.relam WHERE
 SELECT pgtde_is_encrypted('test_enc');
 SELECT pgtde_is_encrypted('test_norm');
 
+SELECT  key_provider_id, key_provider_name, master_key_name
+		FROM tde_master_key_info();
+
 DROP TABLE test_enc;
 DROP TABLE test_norm;
 

src/catalog/tde_master_key.c

@@ -19,6 +19,7 @@
 #include "utils/palloc.h"
 #include "utils/memutils.h"
 #include "utils/wait_event.h"
+#include "utils/timestamp.h"
 #include "common/relpath.h"
 #include "miscadmin.h"
 #include "funcapi.h"
@@ -674,3 +675,66 @@ pg_tde_rotate_key(PG_FUNCTION_ARGS)
     ret = RotateMasterKey(new_master_key_name, new_provider_name, ensure_new_key);
     PG_RETURN_BOOL(ret);
 }
+
+PG_FUNCTION_INFO_V1(tde_master_key_info);
+Datum tde_master_key_info(PG_FUNCTION_ARGS)
+{
+    TupleDesc tupdesc;
+    Datum values[6];
+    bool isnull[6];
+    HeapTuple tuple;
+    Datum result;
+    TDEMasterKey *master_key;
+    TimestampTz ts;
+    GenericKeyring *keyring;
+
+    /* Build a tuple descriptor for our result type */
+    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+        ereport(ERROR,
+                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                    errmsg("function returning record called in context that cannot accept type record")));
+
+    master_key = GetMasterKey();
+    if (master_key == NULL)
+        PG_RETURN_NULL();
+
+    keyring = GetKeyProviderByID(master_key->keyInfo.keyringId);
+
+    /* Initialize the values and null flags */
+
+    /* TEXT: Master key name */
+    values[0] = CStringGetTextDatum(master_key->keyInfo.keyId.name);
+    isnull[0] = false;
+    /* TEXT: Keyring provider name */
+    if (keyring)
+    {
+        values[1] = CStringGetTextDatum(keyring->provider_name);
+        isnull[1] = false;
+    }
+    else
+        isnull[1] = true;
+
+    /* INTEGERT:  key provider id */
+    values[2] = Int32GetDatum(master_key->keyInfo.keyringId);
+    isnull[2] = false;
+
+    /* TEXT: Master key versioned name */
+    values[3] = CStringGetTextDatum(master_key->keyInfo.keyId.versioned_name);
+    isnull[3] = false;
+    /* INTEGERT: Master key version */
+    values[4] = Int32GetDatum(master_key->keyInfo.keyId.version);
+    isnull[4] = false;
+    /* TIMESTAMP TZ: Master key creation time */
+    ts = (TimestampTz)master_key->keyInfo.creationTime.tv_sec - ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);
+    ts = (ts * USECS_PER_SEC) + master_key->keyInfo.creationTime.tv_usec;
+    values[5] = TimestampTzGetDatum(ts);
+    isnull[5] = false;
+
+    /* Form the tuple */
+    tuple = heap_form_tuple(tupdesc, values, isnull);
+
+    /* Make the tuple into a datum */
+    result = HeapTupleGetDatum(tuple);
+
+    PG_RETURN_DATUM(result);
+}