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mbedtls/library/asn1write.c
Gilles Peskine 1b6c09a62e Switch to the new code style 
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2023-01-11 14:52:35 +01:00

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/*
* ASN.1 buffer writing functionality
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "common.h"
#if defined(MBEDTLS_ASN1_WRITE_C)
#include "mbedtls/asn1write.h"
#include "mbedtls/error.h"
#include <string.h>
#include "mbedtls/platform.h"
int mbedtls_asn1_write_len(unsigned char **p, unsigned char *start, size_t len)
{
if (len < 0x80) {
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = (unsigned char) len;
return 1;
}
if (len <= 0xFF) {
if (*p - start < 2) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = (unsigned char) len;
*--(*p) = 0x81;
return 2;
}
if (len <= 0xFFFF) {
if (*p - start < 3) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = MBEDTLS_BYTE_0(len);
*--(*p) = MBEDTLS_BYTE_1(len);
*--(*p) = 0x82;
return 3;
}
if (len <= 0xFFFFFF) {
if (*p - start < 4) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = MBEDTLS_BYTE_0(len);
*--(*p) = MBEDTLS_BYTE_1(len);
*--(*p) = MBEDTLS_BYTE_2(len);
*--(*p) = 0x83;
return 4;
}
int len_is_valid = 1;
#if SIZE_MAX > 0xFFFFFFFF
len_is_valid = (len <= 0xFFFFFFFF);
#endif
if (len_is_valid) {
if (*p - start < 5) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = MBEDTLS_BYTE_0(len);
*--(*p) = MBEDTLS_BYTE_1(len);
*--(*p) = MBEDTLS_BYTE_2(len);
*--(*p) = MBEDTLS_BYTE_3(len);
*--(*p) = 0x84;
return 5;
}
return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
}
int mbedtls_asn1_write_tag(unsigned char **p, unsigned char *start, unsigned char tag)
{
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = tag;
return 1;
}
int mbedtls_asn1_write_raw_buffer(unsigned char **p, unsigned char *start,
const unsigned char *buf, size_t size)
{
size_t len = 0;
if (*p < start || (size_t) (*p - start) < size) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
len = size;
(*p) -= len;
memcpy(*p, buf, len);
return (int) len;
}
#if defined(MBEDTLS_BIGNUM_C)
int mbedtls_asn1_write_mpi(unsigned char **p, unsigned char *start, const mbedtls_mpi *X)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
// Write the MPI
//
len = mbedtls_mpi_size(X);
/* DER represents 0 with a sign bit (0=nonnegative) and 7 value bits, not
* as 0 digits. We need to end up with 020100, not with 0200. */
if (len == 0) {
len = 1;
}
if (*p < start || (size_t) (*p - start) < len) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
(*p) -= len;
MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(X, *p, len));
// DER format assumes 2s complement for numbers, so the leftmost bit
// should be 0 for positive numbers and 1 for negative numbers.
//
if (X->s == 1 && **p & 0x80) {
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = 0x00;
len += 1;
}
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_INTEGER));
ret = (int) len;
cleanup:
return ret;
}
#endif /* MBEDTLS_BIGNUM_C */
int mbedtls_asn1_write_null(unsigned char **p, unsigned char *start)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
// Write NULL
//
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, 0));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_NULL));
return (int) len;
}
int mbedtls_asn1_write_oid(unsigned char **p, unsigned char *start,
const char *oid, size_t oid_len)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start,
(const unsigned char *) oid, oid_len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OID));
return (int) len;
}
int mbedtls_asn1_write_algorithm_identifier(unsigned char **p, unsigned char *start,
const char *oid, size_t oid_len,
size_t par_len)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
if (par_len == 0) {
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_null(p, start));
} else {
len += par_len;
}
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid, oid_len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start,
MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE));
return (int) len;
}
int mbedtls_asn1_write_bool(unsigned char **p, unsigned char *start, int boolean)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = (boolean) ? 255 : 0;
len++;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_BOOLEAN));
return (int) len;
}
static int asn1_write_tagged_int(unsigned char **p, unsigned char *start, int val, int tag)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
do {
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
len += 1;
*--(*p) = val & 0xff;
val >>= 8;
} while (val > 0);
if (**p & 0x80) {
if (*p - start < 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
*--(*p) = 0x00;
len += 1;
}
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, tag));
return (int) len;
}
int mbedtls_asn1_write_int(unsigned char **p, unsigned char *start, int val)
{
return asn1_write_tagged_int(p, start, val, MBEDTLS_ASN1_INTEGER);
}
int mbedtls_asn1_write_enum(unsigned char **p, unsigned char *start, int val)
{
return asn1_write_tagged_int(p, start, val, MBEDTLS_ASN1_ENUMERATED);
}
int mbedtls_asn1_write_tagged_string(unsigned char **p, unsigned char *start, int tag,
const char *text, size_t text_len)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start,
(const unsigned char *) text,
text_len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, tag));
return (int) len;
}
int mbedtls_asn1_write_utf8_string(unsigned char **p, unsigned char *start,
const char *text, size_t text_len)
{
return mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len);
}
int mbedtls_asn1_write_printable_string(unsigned char **p, unsigned char *start,
const char *text, size_t text_len)
{
return mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text,
text_len);
}
int mbedtls_asn1_write_ia5_string(unsigned char **p, unsigned char *start,
const char *text, size_t text_len)
{
return mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len);
}
int mbedtls_asn1_write_named_bitstring(unsigned char **p,
unsigned char *start,
const unsigned char *buf,
size_t bits)
{
size_t unused_bits, byte_len;
const unsigned char *cur_byte;
unsigned char cur_byte_shifted;
unsigned char bit;
byte_len = (bits + 7) / 8;
unused_bits = (byte_len * 8) - bits;
/*
* Named bitstrings require that trailing 0s are excluded in the encoding
* of the bitstring. Trailing 0s are considered part of the 'unused' bits
* when encoding this value in the first content octet
*/
if (bits != 0) {
cur_byte = buf + byte_len - 1;
cur_byte_shifted = *cur_byte >> unused_bits;
for (;;) {
bit = cur_byte_shifted & 0x1;
cur_byte_shifted >>= 1;
if (bit != 0) {
break;
}
bits--;
if (bits == 0) {
break;
}
if (bits % 8 == 0) {
cur_byte_shifted = *--cur_byte;
}
}
}
return mbedtls_asn1_write_bitstring(p, start, buf, bits);
}
int mbedtls_asn1_write_bitstring(unsigned char **p, unsigned char *start,
const unsigned char *buf, size_t bits)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
size_t unused_bits, byte_len;
byte_len = (bits + 7) / 8;
unused_bits = (byte_len * 8) - bits;
if (*p < start || (size_t) (*p - start) < byte_len + 1) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
}
len = byte_len + 1;
/* Write the bitstring. Ensure the unused bits are zeroed */
if (byte_len > 0) {
byte_len--;
*--(*p) = buf[byte_len] & ~((0x1 << unused_bits) - 1);
(*p) -= byte_len;
memcpy(*p, buf, byte_len);
}
/* Write unused bits */
*--(*p) = (unsigned char) unused_bits;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_BIT_STRING));
return (int) len;
}
int mbedtls_asn1_write_octet_string(unsigned char **p, unsigned char *start,
const unsigned char *buf, size_t size)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, buf, size));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OCTET_STRING));
return (int) len;
}
/* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
* which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
static mbedtls_asn1_named_data *asn1_find_named_data(
mbedtls_asn1_named_data *list,
const char *oid, size_t len)
{
while (list != NULL) {
if (list->oid.len == len &&
memcmp(list->oid.p, oid, len) == 0) {
break;
}
list = list->next;
}
return list;
}
mbedtls_asn1_named_data *mbedtls_asn1_store_named_data(
mbedtls_asn1_named_data **head,
const char *oid, size_t oid_len,
const unsigned char *val,
size_t val_len)
{
mbedtls_asn1_named_data *cur;
if ((cur = asn1_find_named_data(*head, oid, oid_len)) == NULL) {
// Add new entry if not present yet based on OID
//
cur = (mbedtls_asn1_named_data *) mbedtls_calloc(1,
sizeof(mbedtls_asn1_named_data));
if (cur == NULL) {
return NULL;
}
cur->oid.len = oid_len;
cur->oid.p = mbedtls_calloc(1, oid_len);
if (cur->oid.p == NULL) {
mbedtls_free(cur);
return NULL;
}
memcpy(cur->oid.p, oid, oid_len);
cur->val.len = val_len;
if (val_len != 0) {
cur->val.p = mbedtls_calloc(1, val_len);
if (cur->val.p == NULL) {
mbedtls_free(cur->oid.p);
mbedtls_free(cur);
return NULL;
}
}
cur->next = *head;
*head = cur;
} else if (val_len == 0) {
mbedtls_free(cur->val.p);
cur->val.p = NULL;
} else if (cur->val.len != val_len) {
/*
* Enlarge existing value buffer if needed
* Preserve old data until the allocation succeeded, to leave list in
* a consistent state in case allocation fails.
*/
void *p = mbedtls_calloc(1, val_len);
if (p == NULL) {
return NULL;
}
mbedtls_free(cur->val.p);
cur->val.p = p;
cur->val.len = val_len;
}
if (val != NULL && val_len != 0) {
memcpy(cur->val.p, val, val_len);
}
return cur;
}
#endif /* MBEDTLS_ASN1_WRITE_C */
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