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openssl-1.0.2f/crypto/store/README

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+The STORE type
+==============
+
+A STORE, as defined in this code section, is really a rather simple
+thing which stores objects and per-object associations to a number
+of attributes.  What attributes are supported entirely depends on
+the particular implementation of a STORE.  It has some support for
+generation of certain objects (for example, keys and CRLs).
+
+
+Supported object types
+----------------------
+
+For now, the objects that are supported are the following:
+
+X.509 certificate
+X.509 CRL
+private key
+public key
+number
+arbitrary (application) data
+
+The intention is that a STORE should be able to store everything
+needed by an application that wants a cert/key store, as well as
+the data a CA might need to store (this includes the serial number
+counter, which explains the support for numbers).
+
+
+Supported attribute types
+-------------------------
+
+For now, the following attributes are supported:
+
+Friendly Name		- the value is a normal C string
+Key ID			- the value is a 160 bit SHA1 hash
+Issuer Key ID		- the value is a 160 bit SHA1 hash
+Subject Key ID		- the value is a 160 bit SHA1 hash
+Issuer/Serial Hash	- the value is a 160 bit SHA1 hash
+Issuer			- the value is a X509_NAME
+Serial			- the value is a BIGNUM
+Subject			- the value is a X509_NAME
+Certificate Hash	- the value is a 160 bit SHA1 hash
+Email			- the value is a normal C string
+Filename		- the value is a normal C string
+
+It is expected that these attributes should be enough to support
+the need from most, if not all, current applications.  Applications
+that need to do certificate verification would typically use Subject
+Key ID, Issuer/Serial Hash or Subject to look up issuer certificates.
+S/MIME applications would typically use Email to look up recipient
+and signer certificates.
+
+There's added support for combined sets of attributes to search for,
+with the special OR attribute.
+
+
+Supported basic functionality
+-----------------------------
+
+The functions that are supported through the STORE type are these:
+
+generate_object		- for example to generate keys and CRLs
+get_object		- to look up one object
+			  NOTE: this function is really rather
+			  redundant and probably of lesser usage
+			  than the list functions
+store_object		- store an object and the attributes
+			  associated with it
+modify_object		- modify the attributes associated with
+			  a specific object
+revoke_object		- revoke an object
+			  NOTE: this only marks an object as
+			  invalid, it doesn't remove the object
+			  from the database
+delete_object		- remove an object from the database
+list_object		- list objects associated with a given
+			  set of attributes
+			  NOTE: this is really four functions:
+			  list_start, list_next, list_end and
+			  list_endp
+update_store		- update the internal data of the store
+lock_store		- lock the store
+unlock_store		- unlock the store
+
+The list functions need some extra explanation: list_start is
+used to set up a lookup.  That's where the attributes to use in
+the search are set up.  It returns a search context.  list_next
+returns the next object searched for.  list_end closes the search.
+list_endp is used to check if we have reached the end.
+
+A few words on the store functions as well: update_store is
+typically used by a CA application to update the internal
+structure of a database.  This may for example involve automatic
+removal of expired certificates.  lock_store and unlock_store
+are used for locking a store to allow exclusive writes.