mirror of https://github.com/openssl/openssl.git
192 lines
6.7 KiB
Plaintext
192 lines
6.7 KiB
Plaintext
=pod
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=head1 NAME
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i2t_ASN1_OBJECT,
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OBJ_length, OBJ_get0_data, OBJ_nid2obj, OBJ_nid2ln,
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OBJ_nid2sn, OBJ_obj2nid, OBJ_txt2nid, OBJ_ln2nid, OBJ_sn2nid, OBJ_cmp,
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OBJ_dup, OBJ_txt2obj, OBJ_obj2txt, OBJ_create, OBJ_cleanup
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- ASN1 object utility functions
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=head1 SYNOPSIS
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#include <openssl/objects.h>
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ASN1_OBJECT *OBJ_nid2obj(int n);
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const char *OBJ_nid2ln(int n);
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const char *OBJ_nid2sn(int n);
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int OBJ_obj2nid(const ASN1_OBJECT *o);
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int OBJ_ln2nid(const char *ln);
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int OBJ_sn2nid(const char *sn);
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int OBJ_txt2nid(const char *s);
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ASN1_OBJECT *OBJ_txt2obj(const char *s, int no_name);
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int OBJ_obj2txt(char *buf, int buf_len, const ASN1_OBJECT *a, int no_name);
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int i2t_ASN1_OBJECT(char *buf, int buf_len, const ASN1_OBJECT *a);
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int OBJ_cmp(const ASN1_OBJECT *a, const ASN1_OBJECT *b);
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ASN1_OBJECT *OBJ_dup(const ASN1_OBJECT *o);
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int OBJ_create(const char *oid, const char *sn, const char *ln);
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size_t OBJ_length(const ASN1_OBJECT *obj);
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const unsigned char *OBJ_get0_data(const ASN1_OBJECT *obj);
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Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
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B<OPENSSL_API_COMPAT> with a suitable version value, see
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L<openssl_user_macros(7)>:
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void OBJ_cleanup(void);
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=head1 DESCRIPTION
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The ASN1 object utility functions process ASN1_OBJECT structures which are
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a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
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For convenience, OIDs are usually represented in source code as numeric
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identifiers, or B<NID>s. OpenSSL has an internal table of OIDs that
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are generated when the library is built, and their corresponding NIDs
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are available as defined constants. For the functions below, application
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code should treat all returned values -- OIDs, NIDs, or names -- as
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constants.
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OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID B<n> to
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an ASN1_OBJECT structure, its long name and its short name respectively,
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or B<NULL> if an error occurred.
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OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
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for the object B<o>, the long name <ln> or the short name <sn> respectively
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or NID_undef if an error occurred.
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OBJ_txt2nid() returns NID corresponding to text string <s>. B<s> can be
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a long name, a short name or the numerical representation of an object.
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OBJ_txt2obj() converts the text string B<s> into an ASN1_OBJECT structure.
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If B<no_name> is 0 then long names and short names will be interpreted
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as well as numerical forms. If B<no_name> is 1 only the numerical form
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is acceptable.
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OBJ_obj2txt() converts the B<ASN1_OBJECT> B<a> into a textual representation.
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The representation is written as a null terminated string to B<buf>
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at most B<buf_len> bytes are written, truncating the result if necessary.
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The total amount of space required is returned. If B<no_name> is 0 then
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if the object has a long or short name then that will be used, otherwise
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the numerical form will be used. If B<no_name> is 1 then the numerical
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form will always be used.
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i2t_ASN1_OBJECT() is the same as OBJ_obj2txt() with the B<no_name> set to zero.
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OBJ_cmp() compares B<a> to B<b>. If the two are identical 0 is returned.
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OBJ_dup() returns a copy of B<o>.
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OBJ_create() adds a new object to the internal table. B<oid> is the
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numerical form of the object, B<sn> the short name and B<ln> the
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long name. A new NID is returned for the created object in case of
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success and NID_undef in case of failure.
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OBJ_length() returns the size of the content octets of B<obj>.
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OBJ_get0_data() returns a pointer to the content octets of B<obj>.
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The returned pointer is an internal pointer which B<must not> be freed.
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OBJ_cleanup() releases any resources allocated by creating new objects.
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=head1 NOTES
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Objects in OpenSSL can have a short name, a long name and a numerical
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identifier (NID) associated with them. A standard set of objects is
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represented in an internal table. The appropriate values are defined
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in the header file B<objects.h>.
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For example the OID for commonName has the following definitions:
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#define SN_commonName "CN"
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#define LN_commonName "commonName"
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#define NID_commonName 13
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New objects can be added by calling OBJ_create().
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Table objects have certain advantages over other objects: for example
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their NIDs can be used in a C language switch statement. They are
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also static constant structures which are shared: that is there
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is only a single constant structure for each table object.
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Objects which are not in the table have the NID value NID_undef.
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Objects do not need to be in the internal tables to be processed,
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the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
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form of an OID.
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Some objects are used to represent algorithms which do not have a
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corresponding ASN.1 OBJECT IDENTIFIER encoding (for example no OID currently
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exists for a particular algorithm). As a result they B<cannot> be encoded or
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decoded as part of ASN.1 structures. Applications can determine if there
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is a corresponding OBJECT IDENTIFIER by checking OBJ_length() is not zero.
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These functions cannot return B<const> because an B<ASN1_OBJECT> can
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represent both an internal, constant, OID and a dynamically-created one.
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The latter cannot be constant because it needs to be freed after use.
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=head1 RETURN VALUES
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OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
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error occurred.
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OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
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on error.
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OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
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a NID or B<NID_undef> on error.
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=head1 EXAMPLES
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Create an object for B<commonName>:
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ASN1_OBJECT *o = OBJ_nid2obj(NID_commonName);
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Check if an object is B<commonName>
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if (OBJ_obj2nid(obj) == NID_commonName)
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/* Do something */
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Create a new NID and initialize an object from it:
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int new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
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ASN1_OBJECT *obj = OBJ_nid2obj(new_nid);
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Create a new object directly:
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obj = OBJ_txt2obj("1.2.3.4", 1);
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=head1 BUGS
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OBJ_obj2txt() is awkward and messy to use: it doesn't follow the
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convention of other OpenSSL functions where the buffer can be set
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to B<NULL> to determine the amount of data that should be written.
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Instead B<buf> must point to a valid buffer and B<buf_len> should
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be set to a positive value. A buffer length of 80 should be more
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than enough to handle any OID encountered in practice.
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=head1 SEE ALSO
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L<ERR_get_error(3)>
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=head1 HISTORY
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OBJ_cleanup() was deprecated in OpenSSL 1.1.0 by L<OPENSSL_init_crypto(3)>
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and should not be used.
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=head1 COPYRIGHT
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Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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