SQLite/GPKG: turn on SQLite 'PRAGMA secure_delete=1' by default

unless the user specifies a value of this pragma through OGR_SQLITE_PRAGMA.

For example, Debian and Conda-Forge SQLite3 builds already turn on secure_delete.
Make sure that this is done for all SQLite3 builds.

autotest/ogr/ogr_gpkg.py

@@ -10540,3 +10540,49 @@ def test_gpkg_create_more_than_2000_fields(tmp_vsimem):
         with pytest.raises(Exception, match="Limit of 2000 columns reached"):
             lyr.CreateField(ogr.FieldDefn("foo"))
         assert lyr.GetLayerDefn().GetFieldCount() == 2000 - 2
+
+
+###############################################################################
+# Test that secure_delete is turned on
+
+
+@gdaltest.enable_exceptions()
+def test_gpkg_secure_delete(tmp_vsimem):
+
+    filename = str(tmp_vsimem / "secure_delete.gpkg")
+    with ogr.GetDriverByName("GPKG").CreateDataSource(filename) as ds:
+
+        with ds.ExecuteSQL("PRAGMA secure_delete") as sql_lyr:
+            f = sql_lyr.GetNextFeature()
+            assert f.GetField(0) == 1
+
+        lyr = ds.CreateLayer("test")
+        lyr.CreateField(ogr.FieldDefn("foo"))
+        f = ogr.Feature(lyr.GetLayerDefn())
+        f["foo"] = "very_secret"
+        lyr.CreateFeature(f)
+
+    f = gdal.VSIFOpenL(filename, "rb")
+    data = gdal.VSIFReadL(1, 100000, f)
+    gdal.VSIFCloseL(f)
+    assert b"very_secret" in data
+
+    with ogr.Open(filename, update=1) as ds:
+
+        with ds.ExecuteSQL("PRAGMA secure_delete") as sql_lyr:
+            f = sql_lyr.GetNextFeature()
+            assert f.GetField(0) == 1
+
+        lyr = ds.GetLayer(0)
+        lyr.DeleteFeature(1)
+
+    f = gdal.VSIFOpenL(filename, "rb")
+    data = gdal.VSIFReadL(1, 100000, f)
+    gdal.VSIFCloseL(f)
+    assert b"very_secret" not in data
+
+    with gdaltest.config_option("OGR_SQLITE_PRAGMA", "secure_delete=0"):
+        with ogr.Open(filename, update=1) as ds:
+            with ds.ExecuteSQL("PRAGMA secure_delete") as sql_lyr:
+                f = sql_lyr.GetNextFeature()
+                assert f.GetField(0) == 0

doc/source/drivers/vector/gpkg.rst

@@ -809,6 +809,18 @@ Examples
         -sql "SELECT poly.id, other.foo FROM poly JOIN other_schema.other USING (id)" \
         -oo PRELUDE_STATEMENTS="ATTACH DATABASE 'other.gpkg' AS other_schema"
 
+Secure deletion
+---------------
+
+Depending on how SQLite3 is built, `secure deletion <https://www.sqlite.org/pragma.html#pragma_secure_delete>`__
+might or might not be enabled.
+Starting with GDAL 3.10, secure deletion is always enabled, unless
+``SECURE_DELETE`` is specified through the :config:`OGR_SQLITE_PRAGMA`
+configuration option.
+Note that secure deletion does not recover potential lost space, so running
+a `VACUUM <https://sqlite.org/lang_vacuum.html>`__ query is recommended to fully
+optimized a database that has been subject to updates or deletions.
+
 See Also
 --------
 

doc/source/drivers/vector/sqlite.rst

@@ -556,6 +556,17 @@ and optimize it.
 
    ogrinfo db.sqlite -sql "VACUUM"
 
+Secure deletion
+---------------
+
+Depending on how SQLite3 is built, `secure deletion <https://www.sqlite.org/pragma.html#pragma_secure_delete>`__
+might or might not be enabled.
+Starting with GDAL 3.10, secure deletion is always enabled, unless
+``SECURE_DELETE`` is specified through the :config:`OGR_SQLITE_PRAGMA`
+configuration option.
+Note that secure deletion does not recover potential lost space, so running
+a `VACUUM <https://sqlite.org/lang_vacuum.html>`__ query is recommended to fully
+optimized a database that has been subject to updates or deletions.
 
 Example
 -------

ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp

@@ -1372,6 +1372,7 @@ bool OGRSQLiteBaseDataSource::OpenOrCreateDB(int flagsIn,
 #endif
 
     bool bPageSizeFound = false;
+    bool bSecureDeleteFound = false;
 
     const char *pszSqlitePragma =
         CPLGetConfigOption("OGR_SQLITE_PRAGMA", nullptr);
@@ -1456,7 +1457,7 @@ bool OGRSQLiteBaseDataSource::OpenOrCreateDB(int flagsIn,
             {
                 if (STARTS_WITH_CI(papszTokens[i], "PAGE_SIZE"))
                     bPageSizeFound = true;
-                if (STARTS_WITH_CI(papszTokens[i], "JOURNAL_MODE"))
+                else if (STARTS_WITH_CI(papszTokens[i], "JOURNAL_MODE"))
                 {
                     const char *pszEqual = strchr(papszTokens[i], '=');
                     if (pszEqual)
@@ -1467,6 +1468,8 @@ bool OGRSQLiteBaseDataSource::OpenOrCreateDB(int flagsIn,
                         continue;
                     }
                 }
+                else if (STARTS_WITH_CI(papszTokens[i], "SECURE_DELETE"))
+                    bSecureDeleteFound = true;
 
                 const char *pszSQL = CPLSPrintf("PRAGMA %s", papszTokens[i]);
 
@@ -1646,6 +1649,16 @@ bool OGRSQLiteBaseDataSource::OpenOrCreateDB(int flagsIn,
             sqlite3_exec(hDB, pszSQL, nullptr, nullptr, nullptr));
     }
 
+    if (!bSecureDeleteFound)
+    {
+        // Turn on secure_delete by default (unless the user specifies a
+        // value of this pragma through OGR_SQLITE_PRAGMA)
+        // For example, Debian and Conda-Forge SQLite3 builds already turn on
+        // secure_delete.
+        CPL_IGNORE_RET_VAL(sqlite3_exec(hDB, "PRAGMA secure_delete = 1",
+                                        nullptr, nullptr, nullptr));
+    }
+
     SetCacheSize();
     SetSynchronous();
     if (bLoadExtensions)