1.\" $OpenBSD: d2i_ASN1_OBJECT.3,v 1.14 2023/08/09 17:27:26 schwarze Exp $ 2.\" 3.\" Copyright (c) 2017, 2022, 2023 Ingo Schwarze <schwarze@openbsd.org> 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd $Mdocdate: August 9 2023 $ 18.Dt D2I_ASN1_OBJECT 3 19.Os 20.Sh NAME 21.Nm d2i_ASN1_OBJECT , 22.Nm i2d_ASN1_OBJECT , 23.Nm OBJ_get0_data , 24.Nm OBJ_length 25.Nd decode and encode ASN.1 object identifiers 26.Sh SYNOPSIS 27.In openssl/asn1.h 28.Ft ASN1_OBJECT * 29.Fo d2i_ASN1_OBJECT 30.Fa "ASN1_OBJECT **val_out" 31.Fa "unsigned char **der_in" 32.Fa "long length" 33.Fc 34.Ft int 35.Fo i2d_ASN1_OBJECT 36.Fa "const ASN1_OBJECT *val_in" 37.Fa "unsigned char **der_out" 38.Fc 39.In openssl/objects.h 40.Ft const unsigned char * 41.Fn OBJ_get0_data "const ASN1_OBJECT *val_in" 42.Ft size_t 43.Fn OBJ_length "const ASN1_OBJECT *val_in" 44.Sh DESCRIPTION 45These functions decode and encode ASN.1 object identifiers. 46For details about the semantics, examples, caveats, and bugs, see 47.Xr ASN1_item_d2i 3 . 48.Pp 49The LibreSSL implementation of 50.Fn d2i_ASN1_OBJECT 51always calls 52.Xr ASN1_OBJECT_free 3 53if an existing object is passed in via 54.Fa val_out 55and it always creates a new object from scratch. 56Other implementations may attempt to reuse an existing object, 57which is fragile and prone to bugs. 58Consequently, always passing 59.Dv NULL 60for the 61.Fa val_out 62argument is recommended. 63.Pp 64The objects returned from 65.Fn d2i_ASN1_OBJECT 66and the data contained in them are always marked as dynamically 67allocated, so when they are no longer needed, 68.Xr ASN1_OBJECT_free 3 69can be called on them. 70.Pp 71.Fn i2d_ASN1_OBJECT 72encodes the object identifier pointed to by 73.Fa val_in 74into DER format. 75.Fn OBJ_get0_data 76and 77.Fn OBJ_length 78only deal with the content octets of that DER encoding, 79without taking the identifier and length octets into account. 80.Sh RETURN VALUES 81.Fn d2i_ASN1_OBJECT 82returns a pointer to the new 83.Vt ASN1_OBJECT 84object or 85.Dv NULL 86if an error occurs. 87With other implementations, it might return a pointer to the reused 88.Vt ASN1_OBJECT . 89.Pp 90.Fn i2d_ASN1_OBJECT 91returns the number of octets successfully encoded 92or a value <= 0 if an error occurs. 93.Pp 94.Fn OBJ_get0_data 95returns an internal pointer to the first content octet of the DER 96encoding of 97.Fa val_in . 98The other content octets follow the returned pointer contiguously. 99.Fn OBJ_length 100returns the number of content octets contained in the DER encoding of 101.Fa val_in . 102This number is always smaller than the total length of the encoding 103returned by 104.Xr ASN1_object_size 3 . 105.Pp 106If 107.Fa val_in 108is a 109.Dv NULL 110pointer or points to an empty object, for example one freshly created with 111.Xr ASN1_OBJECT_new 3 , 112.Fn OBJ_get0_data 113returns 114.Dv NULL 115and 116.Fn OBJ_length 117returns zero. 118.Sh SEE ALSO 119.Xr a2d_ASN1_OBJECT 3 , 120.Xr ASN1_item_d2i 3 , 121.Xr ASN1_OBJECT_new 3 , 122.Xr ASN1_put_object 3 , 123.Xr OBJ_nid2obj 3 124.Sh STANDARDS 125ITU-T Recommendation X.690, also known as ISO/IEC 8825-1: 126Information technology - ASN.1 encoding rules: 127Specification of Basic Encoding Rules (BER), Canonical Encoding 128Rules (CER) and Distinguished Encoding Rules (DER), 129section 8.19: Encoding of an object identifier value 130.Sh HISTORY 131.Fn d2i_ASN1_OBJECT 132and 133.Fn i2d_ASN1_OBJECT 134first appeared in SSLeay 0.5.1 and have been available since 135.Ox 2.4 . 136.Pp 137.Fn OBJ_get0_data 138and 139.Fn OBJ_length 140first appeared in OpenSSL 1.1.0 and have been available since 141.Ox 7.1 . 142.Sh CAVEATS 143.Fn d2i_ASN1_OBJECT 144never sets the long and short names of the object, not even if the 145object identifier matches one that is built into the library. 146To find the names of an object identifier parsed from DER or BER 147input, call 148.Xr OBJ_obj2nid 3 149on the returned object, and then 150.Xr OBJ_nid2sn 3 151and 152.Xr OBJ_nid2ln 3 153on the result. 154.Pp 155Calling 156.Fn OBJ_get0_data 157and then accessing memory in front of the returned pointer 158results in undefined behaviour. 159In particular, it is not possible to find the identifier or 160length octets in that way; use 161.Xr ASN1_put_object 3 162or 163.Fn i2d_ASN1_OBJECT 164instead. 165