HP Open Source Security for OpenVMS Volume 2: HP SSL for OpenVMS > CRYPTO Application
Programming Interface (API) Reference
ASN1_OBJECT * OBJ_nid2obj(int n);
The ASN1 object utility functions process ASN1_OBJECT structures which are a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID n to an ASN1_OBJECT structure, its long name and its short name respectively, or NULL is an error occurred.
OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID for the object o, the long name <ln> or the short name <sn> respectively or NID_undef if an error occurred.
OBJ_txt2nid() returns NID corresponding to text string <s>. s can be a long name, a short name or the numerical respresentation of an object.
OBJ_txt2obj() converts the text string s into an ASN1_OBJECT structure. If no_name is 0 then long names and short names will be interpreted as well as numerical forms. If no_name is 1 only the numerical form is acceptable.
OBJ_obj2txt() converts the ASN1_OBJECT a into a textual representation. The representation is written as a null terminated string to buf at most buf_len bytes are written, truncating the result if necessary. The total amount of space required is returned. If no_name is 0 then if the object has a long or short name then that will be used, otherwise the numerical form will be used. If no_name is 1 then the numerical form will always be used.
OBJ_cmp() compares a to b. If the two are identical 0 is returned.
OBJ_dup() returns a copy of o.
OBJ_create() adds a new object to the internal table. oid is the numerical form of the object, sn the short name and ln the long name. A new NID is returned for the created object.
OBJ_cleanup() cleans up OpenSSLs internal object table: this should be called before an application exits if any new objects were added using OBJ_create().
Objects in OpenSSL can have a short name, a long name and a numerical identifier (NID) associated with them. A standard set of objects is represented in an internal table. The appropriate values are defined in the header file objects.h.
For example the OID for commonName has the following definitions:
New objects can be added by calling OBJ_create().
Table objects have certain advantages over other objects: for example their NIDs can be used in a C language switch statement. They are also static constant structures which are shared: that is there is only a single constant structure for each table object.
Objects which are not in the table have the NID value NID_undef.
Objects do not need to be in the internal tables to be processed, the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical form of an OID.
Create an object for commonName:
Check if an object is commonName
Create a new NID and initialize an object from it:
OBJ_obj2txt() is awkward and messy to use: it doesn't follow the convention of other OpenSSL functions where the buffer can be set to NULL to determine the amount of data that should be written. Instead buf must point to a valid buffer and buf_len should be set to a positive value. A buffer length of 80 should be more than enough to handle any OID encountered in practice.
OBJ_nid2obj() returns an ASN1_OBJECT structure or NULL is an error occurred.
OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or NULL on error.
OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return a NID or NID_undef on error.