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1d39620b34
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)
143 lines
3.8 KiB
C
143 lines
3.8 KiB
C
/*
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* Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
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*
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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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* https://www.openssl.org/source/license.html
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "internal/cryptlib.h"
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#include "internal/der.h"
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#include "crypto/bn.h"
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static int int_start_context(WPACKET *pkt, int tag)
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{
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if (tag < 0)
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return 1;
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if (!ossl_assert(tag <= 30))
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return 0;
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return WPACKET_start_sub_packet(pkt);
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}
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static int int_end_context(WPACKET *pkt, int tag)
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{
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if (tag < 0)
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return 1;
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if (!ossl_assert(tag <= 30))
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return 0;
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return WPACKET_close(pkt)
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&& WPACKET_put_bytes_u8(pkt, DER_C_CONTEXT | tag);
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}
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int DER_w_precompiled(WPACKET *pkt, int tag,
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const unsigned char *precompiled, size_t precompiled_n)
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{
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return int_start_context(pkt, tag)
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&& WPACKET_memcpy(pkt, precompiled, precompiled_n)
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&& int_end_context(pkt, tag);
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}
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int DER_w_boolean(WPACKET *pkt, int tag, int b)
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{
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return int_start_context(pkt, tag)
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&& WPACKET_start_sub_packet(pkt)
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&& (!b || WPACKET_put_bytes_u8(pkt, 0xFF))
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&& !WPACKET_close(pkt)
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&& !WPACKET_put_bytes_u8(pkt, DER_P_BOOLEAN)
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&& int_end_context(pkt, tag);
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}
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static int int_der_w_integer(WPACKET *pkt, int tag,
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int (*put_bytes)(WPACKET *pkt, const void *v,
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unsigned int *top_byte),
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const void *v)
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{
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unsigned int top_byte = 0;
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return int_start_context(pkt, tag)
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&& WPACKET_start_sub_packet(pkt)
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&& put_bytes(pkt, v, &top_byte)
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&& ((top_byte & 0x80) == 0 || WPACKET_put_bytes_u8(pkt, 0))
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&& WPACKET_close(pkt)
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&& WPACKET_put_bytes_u8(pkt, DER_P_INTEGER)
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&& int_end_context(pkt, tag);
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}
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static int int_put_bytes_ulong(WPACKET *pkt, const void *v,
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unsigned int *top_byte)
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{
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const unsigned long *value = v;
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unsigned long tmp = *value;
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size_t n = 0;
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while (tmp != 0) {
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n++;
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*top_byte = (tmp & 0xFF);
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tmp >>= 8;
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}
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if (n == 0)
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n = 1;
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return WPACKET_put_bytes__(pkt, *value, n);
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}
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/* For integers, we only support unsigned values for now */
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int DER_w_ulong(WPACKET *pkt, int tag, unsigned long v)
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{
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return int_der_w_integer(pkt, tag, int_put_bytes_ulong, &v);
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}
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static int int_put_bytes_bn(WPACKET *pkt, const void *v,
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unsigned int *top_byte)
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{
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unsigned char *p = NULL;
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size_t n = BN_num_bytes(v);
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/* The BIGNUM limbs are in LE order */
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*top_byte =
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((bn_get_words(v) [(n - 1) / BN_BYTES]) >> (8 * ((n - 1) % BN_BYTES)))
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& 0xFF;
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if (!WPACKET_allocate_bytes(pkt, n, &p))
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return 0;
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if (p != NULL)
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BN_bn2bin(v, p);
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return 1;
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}
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int DER_w_bn(WPACKET *pkt, int tag, const BIGNUM *v)
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{
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if (v == NULL || BN_is_negative(v))
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return 0;
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if (BN_is_zero(v))
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return DER_w_ulong(pkt, tag, 0);
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return int_der_w_integer(pkt, tag, int_put_bytes_bn, v);
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}
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int DER_w_null(WPACKET *pkt, int tag)
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{
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return int_start_context(pkt, tag)
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&& WPACKET_start_sub_packet(pkt)
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&& WPACKET_close(pkt)
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&& WPACKET_put_bytes_u8(pkt, DER_P_NULL)
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&& int_end_context(pkt, tag);
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}
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/* Constructed things need a start and an end */
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int DER_w_begin_sequence(WPACKET *pkt, int tag)
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{
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return int_start_context(pkt, tag)
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&& WPACKET_start_sub_packet(pkt);
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}
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int DER_w_end_sequence(WPACKET *pkt, int tag)
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{
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return WPACKET_close(pkt)
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&& WPACKET_put_bytes_u8(pkt, DER_F_CONSTRUCTED | DER_P_SEQUENCE)
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&& int_end_context(pkt, tag);
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}
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