storage_backend/attachment_db_by_checksum/security/ir.model.access.csv

1	id	name	model_id:id	group_id:id	perm_read	perm_write	perm_create	perm_unlink
2	access_ir_attachment_all	Everyone can read Attachment Contents	model_ir_attachment_content		1	0	0	0
3	access_ir_attachment_group_user	Internal Users can manage Attachment Contents	model_ir_attachment_content	base.group_user	1	1	1	1
4	access_ir_attachment_portal	Portal Users can read and create Attachment Contents	model_ir_attachment_content	base.group_portal	1	0	1	0