A local copy of OpenSSL from GitHub
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/*
* 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
* https://www.openssl.org/source/license.html
*/
#include <stdlib.h>
#include <string.h>
#include "internal/cryptlib.h"
#include "internal/der.h"
#include "crypto/bn.h"
static int int_start_context(WPACKET *pkt, int tag)
{
if (tag < 0)
return 1;
if (!ossl_assert(tag <= 30))
return 0;
return WPACKET_start_sub_packet(pkt);
}
static int int_end_context(WPACKET *pkt, int tag)
{
/*
* If someone set the flag WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH on this
* sub-packet and this sub-packet has nothing written to it, the DER length
* will not be written, and the total written size will be unchanged before
* and after WPACKET_close(). We use size1 and size2 to determine if
* anything was written, and only write our tag if it has.
*
*/
size_t size1, size2;
if (tag < 0)
return 1;
if (!ossl_assert(tag <= 30))
return 0;
/* Context specific are normally (?) constructed */
tag |= DER_F_CONSTRUCTED | DER_C_CONTEXT;
return WPACKET_get_total_written(pkt, &size1)
&& WPACKET_close(pkt)
&& WPACKET_get_total_written(pkt, &size2)
&& (size1 == size2 || WPACKET_put_bytes_u8(pkt, tag));
}
int ossl_DER_w_precompiled(WPACKET *pkt, int tag,
const unsigned char *precompiled,
size_t precompiled_n)
{
return int_start_context(pkt, tag)
&& WPACKET_memcpy(pkt, precompiled, precompiled_n)
&& int_end_context(pkt, tag);
}
int ossl_DER_w_boolean(WPACKET *pkt, int tag, int b)
{
return int_start_context(pkt, tag)
&& WPACKET_start_sub_packet(pkt)
&& (!b || WPACKET_put_bytes_u8(pkt, 0xFF))
&& !WPACKET_close(pkt)
&& !WPACKET_put_bytes_u8(pkt, DER_P_BOOLEAN)
&& int_end_context(pkt, tag);
}
int ossl_DER_w_octet_string(WPACKET *pkt, int tag,
const unsigned char *data, size_t data_n)
{
return int_start_context(pkt, tag)
&& WPACKET_start_sub_packet(pkt)
&& WPACKET_memcpy(pkt, data, data_n)
&& WPACKET_close(pkt)
&& WPACKET_put_bytes_u8(pkt, DER_P_OCTET_STRING)
&& int_end_context(pkt, tag);
}
int ossl_DER_w_octet_string_uint32(WPACKET *pkt, int tag, uint32_t value)
{
unsigned char tmp[4] = { 0, 0, 0, 0 };
unsigned char *pbuf = tmp + (sizeof(tmp) - 1);
while (value > 0) {
*pbuf-- = (value & 0xFF);
value >>= 8;
}
return ossl_DER_w_octet_string(pkt, tag, tmp, sizeof(tmp));
}
static int int_der_w_integer(WPACKET *pkt, int tag,
int (*put_bytes)(WPACKET *pkt, const void *v,
unsigned int *top_byte),
const void *v)
{
unsigned int top_byte = 0;
return int_start_context(pkt, tag)
&& WPACKET_start_sub_packet(pkt)
&& put_bytes(pkt, v, &top_byte)
&& ((top_byte & 0x80) == 0 || WPACKET_put_bytes_u8(pkt, 0))
&& WPACKET_close(pkt)
&& WPACKET_put_bytes_u8(pkt, DER_P_INTEGER)
&& int_end_context(pkt, tag);
}
static int int_put_bytes_ulong(WPACKET *pkt, const void *v,
unsigned int *top_byte)
{
const unsigned long *value = v;
unsigned long tmp = *value;
size_t n = 0;
while (tmp != 0) {
n++;
*top_byte = (tmp & 0xFF);
tmp >>= 8;
}
if (n == 0)
n = 1;
return WPACKET_put_bytes__(pkt, *value, n);
}
/* For integers, we only support unsigned values for now */
int ossl_DER_w_ulong(WPACKET *pkt, int tag, unsigned long v)
{
return int_der_w_integer(pkt, tag, int_put_bytes_ulong, &v);
}
static int int_put_bytes_bn(WPACKET *pkt, const void *v,
unsigned int *top_byte)
{
unsigned char *p = NULL;
size_t n = BN_num_bytes(v);
/* The BIGNUM limbs are in LE order */
*top_byte =
((bn_get_words(v) [(n - 1) / BN_BYTES]) >> (8 * ((n - 1) % BN_BYTES)))
& 0xFF;
if (!WPACKET_allocate_bytes(pkt, n, &p))
return 0;
if (p != NULL)
BN_bn2bin(v, p);
return 1;
}
int ossl_DER_w_bn(WPACKET *pkt, int tag, const BIGNUM *v)
{
if (v == NULL || BN_is_negative(v))
return 0;
if (BN_is_zero(v))
return ossl_DER_w_ulong(pkt, tag, 0);
return int_der_w_integer(pkt, tag, int_put_bytes_bn, v);
}
int ossl_DER_w_null(WPACKET *pkt, int tag)
{
return int_start_context(pkt, tag)
&& WPACKET_start_sub_packet(pkt)
&& WPACKET_close(pkt)
&& WPACKET_put_bytes_u8(pkt, DER_P_NULL)
&& int_end_context(pkt, tag);
}
/* Constructed things need a start and an end */
int ossl_DER_w_begin_sequence(WPACKET *pkt, int tag)
{
return int_start_context(pkt, tag)
&& WPACKET_start_sub_packet(pkt);
}
int ossl_DER_w_end_sequence(WPACKET *pkt, int tag)
{
/*
* If someone set the flag WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH on this
* sub-packet and this sub-packet has nothing written to it, the DER length
* will not be written, and the total written size will be unchanged before
* and after WPACKET_close(). We use size1 and size2 to determine if
* anything was written, and only write our tag if it has.
*
* Because we know that int_end_context() needs to do the same check,
* we reproduce this flag if the written length was unchanged, or we will
* have an erroneous context tag.
*/
size_t size1, size2;
return WPACKET_get_total_written(pkt, &size1)
&& WPACKET_close(pkt)
&& WPACKET_get_total_written(pkt, &size2)
&& (size1 == size2
? WPACKET_set_flags(pkt, WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH)
: WPACKET_put_bytes_u8(pkt, DER_F_CONSTRUCTED | DER_P_SEQUENCE))
&& int_end_context(pkt, tag);
}