openssl/doc/internal/man3/DER_w_bn.pod
Richard Levitte 1d39620b34 PROV: Add the beginning of a DER writing library
This library is meant to be small and quick.  It's based on WPACKET,
which was extended to support DER writing.  The way it's used is a
bit unusual, as it's used to write the structures backward into a
given buffer.  A typical quick call looks like this:

    /*
     * Fill in this structure:
     *
     * something ::= SEQUENCE {
     *     id OBJECT IDENTIFIER,
     *     x [0] INTEGER OPTIONAL,
     *     y [1] BOOLEAN OPTIONAL,
     *     n INTEGER
     * }
     */
    unsigned char buf[nnnn], *p = NULL;
    size_t encoded_len = 0;
    WPACKET pkt;
    int ok;

    ok =   WPACKET_init_der(&pkt, buf, sizeof(buf)
        && DER_w_start_sequence(&pkt, -1)
        && DER_w_bn(&pkt, -1, bn)
        && DER_w_boolean(&pkt, 1, bool)
        && DER_w_precompiled(&pkt, -1, OID, sizeof(OID))
        && DER_w_end_sequence(&pkt, -1)
        && WPACKET_finish(&pkt)
        && WPACKET_get_total_written(&pkt, &encoded_len)
        && (p = WPACKET_get_curr(&pkt)) != NULL;

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11450)
2020-04-07 11:16:56 +02:00

57 lines
1.6 KiB
Plaintext

=pod
=head1 NAME
DER_w_boolean, DER_w_ulong, DER_w_bn, DER_w_null
- internal DER writers for DER primitives
=head1 SYNOPSIS
#include "internal/der.h"
int DER_w_boolean(WPACKET *pkt, int tag, int b);
int DER_w_ulong(WPACKET *pkt, int tag, unsigned long v);
int DER_w_bn(WPACKET *pkt, int tag, const BIGNUM *v);
int DER_w_null(WPACKET *pkt, int tag);
=head1 DESCRIPTION
All functions described here behave the same way, they prepend
(remember that DER writers are used backwards) the DER encoding of
their respective value to the already written output buffer held by
I<pkt>.
DER_w_boolean() writes the primitive BOOLEAN using the value I<b>.
Any value that evaluates as true will render a B<true> BOOLEAN,
otherwise a B<false> BOOLEAN.
DER_w_ulong() and DER_w_bn() both write the primitive INTEGER using
the value I<v>.
=for comment Other similar functions for diverse C integers should be
added.
DER_w_null() writes the primitive NULL.
=head1 RETURN VALUES
All the functions return 1 on success and 0 on failure. Failure may
mean that the buffer held by the I<pkt> is too small, but may also
mean that the values given to the functions are invalid, such as the provided
I<tag> value being too large for the implementation.
=head1 SEE ALSO
L<DERlib(7)>
=head1 COPYRIGHT
Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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
L<https://www.openssl.org/source/license.html>.
=cut