NAME

       i2t_ASN1_OBJECT, OBJ_length, OBJ_get0_data, OBJ_nid2obj, OBJ_nid2ln, OBJ_nid2sn,
       OBJ_obj2nid, OBJ_txt2nid, OBJ_ln2nid, OBJ_sn2nid, OBJ_cmp, OBJ_dup, OBJ_txt2obj,
       OBJ_obj2txt, OBJ_create, OBJ_cleanup - ASN1 object utility functions

SYNOPSIS

        #include <openssl/objects.h>

        ASN1_OBJECT *OBJ_nid2obj(int n);
        const char *OBJ_nid2ln(int n);
        const char *OBJ_nid2sn(int n);

        int OBJ_obj2nid(const ASN1_OBJECT *o);
        int OBJ_ln2nid(const char *ln);
        int OBJ_sn2nid(const char *sn);

        int OBJ_txt2nid(const char *s);

        ASN1_OBJECT *OBJ_txt2obj(const char *s, int no_name);
        int OBJ_obj2txt(char *buf, int buf_len, const ASN1_OBJECT *a, int no_name);

        int i2t_ASN1_OBJECT(char *buf, int buf_len, const ASN1_OBJECT *a);

        int OBJ_cmp(const ASN1_OBJECT *a, const ASN1_OBJECT *b);
        ASN1_OBJECT *OBJ_dup(const ASN1_OBJECT *o);

        int OBJ_create(const char *oid, const char *sn, const char *ln);

        size_t OBJ_length(const ASN1_OBJECT *obj);
        const unsigned char *OBJ_get0_data(const ASN1_OBJECT *obj);

       Deprecated:

        #if OPENSSL_API_COMPAT < 0x10100000L
        void OBJ_cleanup(void)
        #endif

DESCRIPTION

       The ASN1 object utility functions process ASN1_OBJECT structures which are a
       representation of the ASN1 OBJECT IDENTIFIER (OID) type.  For convenience, OIDs are
       usually represented in source code as numeric identifiers, or NIDs.  OpenSSL has an
       internal table of OIDs that are generated when the library is built, and their
       corresponding NIDs are available as defined constants.  For the functions below,
       application code should treat all returned values -- OIDs, NIDs, or names -- as constants.

       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 if 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 representation 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.

       i2t_ASN1_OBJECT() is the same as OBJ_obj2txt() with the no_name set to zero.

       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 in case of success and NID_undef in case of failure.

       OBJ_length() returns the size of the content octets of obj.

       OBJ_get0_data() returns a pointer to the content octets of obj.  The returned pointer is
       an internal pointer which must not be freed.

       OBJ_cleanup() releases any resources allocated by creating new objects.

NOTES

       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:

        #define SN_commonName                   "CN"
        #define LN_commonName                   "commonName"
        #define NID_commonName                  13

       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.

       Some objects are used to represent algorithms which do not have a corresponding ASN.1
       OBJECT IDENTIFIER encoding (for example no OID currently exists for a particular
       algorithm). As a result they cannot be encoded or decoded as part of ASN.1 structures.
       Applications can determine if there is a corresponding OBJECT IDENTIFIER by checking
       OBJ_length() is not zero.

       These functions cannot return const because an ASN1_OBJECT can represent both an internal,
       constant, OID and a dynamically-created one.  The latter cannot be constant because it
       needs to be freed after use.

EXAMPLES

       Create an object for commonName:

        ASN1_OBJECT *o = OBJ_nid2obj(NID_commonName);

       Check if an object is commonName

        if (OBJ_obj2nid(obj) == NID_commonName)
            /* Do something */

       Create a new NID and initialize an object from it:

        int new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
        ASN1_OBJECT *obj = OBJ_nid2obj(new_nid);

       Create a new object directly:

        obj = OBJ_txt2obj("1.2.3.4", 1);

BUGS

       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.

RETURN VALUES

       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.

SEE ALSO

       ERR_get_error(3)

HISTORY

       OBJ_cleanup() was deprecated in OpenSSL 1.1.0 by OPENSSL_init_crypto(3) and should not be
       used.

COPYRIGHT

       Copyright 2002-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.