|OBJ_NID2OBJ(3)||Library Functions Manual||OBJ_NID2OBJ(3)|
i2t_ASN1_OBJECT — inspect
and create ASN.1 object identifiers
const char *
const char *
OBJ_ln2nid(const char *ln);
OBJ_sn2nid(const char *sn);
OBJ_txt2nid(const char *s);
OBJ_txt2obj(const char *s,
int buf_len, const ASN1_OBJECT
*a, int no_name);
OBJ_cmp(const ASN1_OBJECT *a,
const ASN1_OBJECT *b);
OBJ_create(const char *oid,
const char *sn, const char
int buf_len, const ASN1_OBJECT
The ASN.1 object utility functions process ASN1_OBJECT structures which are a representation of the ASN.1 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_nid2sn() convert the NID n
to an ASN1_OBJECT structure, its long name, and its
short name, respectively, or return
NULL if an error
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 the 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 NUL 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 and the object
has a long or short name, then that will be used, otherwise the numerical
form will be used.
i2t_ASN1_OBJECT() is the same as
OBJ_obj2txt() with no_name set
OBJ_cmp() compares a
to b. If the two are identical, 0 is returned.
OBJ_dup() returns a deep copy of
o if o is marked as dynamically
allocated. The new object and all data contained in it is marked as
dynamically allocated. If o is not marked as
OBJ_dup() just returns
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.
The new object added to the internal table and all the data
contained in it is marked as not dynamically allocated. Consequently,
retrieving it with
OBJ_nid2obj() or a similar
function and then calling
ASN1_OBJECT_free(3) on the
returned pointer will have no effect.
OBJ_cleanup() cleans up the internal
object table: this should be called before an application exits if any new
objects were added using
Objects 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
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
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
Objects do not need to be in the internal tables to be processed:
OBJ_obj2txt() can process the numerical form of an
OBJ_dup() return an
ASN1_OBJECT object or
an error occurs.
OBJ_nid2sn() return a valid string or
NULL on error.
OBJ_txt2nid() return a NID or
NID_undef on error.
OBJ_create() returns the new NID or
NID_undef if an error occurs.
In some cases of failure of
i2t_ASN1_OBJECT(), the reason can be determined with
Create an object for commonName:
ASN1_OBJECT *o; 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; ASN1_OBJECT *obj; new_nid = OBJ_create("126.96.36.199", "NewOID", "New Object Identifier"); obj = OBJ_nid2obj(new_nid);
Create a new object directly:
obj = OBJ_txt2obj("188.8.131.52", 1);
first appeared in SSLeay 0.5.1.
appeared in SSLeay 0.8.0.
i2t_ASN1_OBJECT() first appeared in SSLeay 0.9.0.
All these functions have been available since OpenBSD
OBJ_txt2obj() first appeared in OpenSSL
OBJ_obj2txt() first appeared in OpenSSL
0.9.4. Both functions have been available since OpenBSD
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.
|June 14, 2019||OpenBSD-current|