Commit c87cc07a authored by Niels Möller's avatar Niels Möller

* der-iterator.c: New file.

* asn1.h: New file.

Rev: src/nettle/asn1.h:1.1
Rev: src/nettle/der-iterator.c:1.1
parent 9b7af408
/* asn1.h
*
* Some very limited asn.1 support.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2005 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#ifndef NETTLE_ASN1_H_INCLUDED
#define NETTLE_ASN1_H_INCLUDED
#include "nettle-types.h"
/* enum asn1_type keeps the class number and the constructive in bits
13-14, and the constructive flag in bit 12. The remaining 14 bits
are the tag (although currently, only tags in the range 0-30 are
supported). */
enum
{
ASN1_TYPE_CONSTRUCTED = 1 << 12,
ASN1_CLASS_UNIVERSAL = 0,
ASN1_CLASS_APPLICATION = 1 << 13,
ASN1_CLASS_CONTEXT_SPECIFIC = 2 << 13,
ASN1_CLASS_PRIVATE = 3 << 13,
ASN1_CLASS_MASK = 3 << 13,
ASN1_CLASS_SHIFT = 13,
};
enum asn1_type
{
ASN1_BOOLEAN = 1,
ASN1_INTEGER = 2,
ASN1_BITSTRING = 3,
ASN1_OCTETSTRING = 4,
ASN1_NULL = 5,
ASN1_IDENTIFIER = 6,
ASN1_REAL = 9,
ASN1_ENUMERATED = 10,
ASN1_UTF8STRING = 12,
ASN1_SEQUENCE = 16 | ASN1_TYPE_CONSTRUCTED,
ASN1_SET = 17 | ASN1_TYPE_CONSTRUCTED,
ASN1_PRINTABLESTRING = 19,
ASN1_TELETEXSTRING = 20,
ASN1_IA5STRING = 22,
ASN1_UTC = 23,
ASN1_UNIVERSALSTRING = 28,
ASN1_BMPSTRING = 30,
};
enum asn1_iterator_result
{
ASN1_ITERATOR_ERROR,
ASN1_ITERATOR_PRIMITIVE,
ASN1_ITERATOR_CONSTRUCTED,
ASN1_ITERATOR_END,
};
/* Parsing DER objects. */
struct asn1_der_iterator
{
unsigned buffer_length;
const uint8_t *buffer;
/* Next object to parse. */
unsigned pos;
enum asn1_type type;
/* Pointer to the current object */
unsigned length;
const uint8_t *data;
};
/* Initializes the iterator. */
enum asn1_iterator_result
asn1_der_iterator_first(struct asn1_der_iterator *iterator,
unsigned length, const uint8_t *input);
enum asn1_iterator_result
asn1_der_iterator_next(struct asn1_der_iterator *iterator);
/* Starts parsing of a constructed object. */
enum asn1_iterator_result
asn1_der_decode_constructed(struct asn1_der_iterator *i,
struct asn1_der_iterator *contents);
/* All these functions return 1 on success, 0 on failure */
int
asn1_der_get_uint32(struct asn1_der_iterator *i,
uint32_t *x);
#endif /* NETTLE_ASN1_H_INCLUDED */
/* der-iterator.c
*
* Parses DER encoded objects.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2005 Niels Mller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#if HAVE_LIBGMP
#include "bignum.h"
#endif
#include "asn1.h"
#include "macros.h"
/* Basic DER syntax: (reference: A Layman's Guide to a Subset of ASN.1, BER, and DER,
http://luca.ntop.org/Teaching/Appunti/asn1.html)
The DER header contains a tag and a length. First, the tag. cls is
the class number, c is one if the object is "constructed" and zero
if it is primitive. The tag is represented either using a single
byte,
7 6 5 4 3 2 1 0
_____________________
|_cls_|_c_|_______tag_| 0 <= tag <= 30
or multiple bytes
7 6 5 4 3 2 1 0
_____________________
|_cls_|_c_|_1_1_1_1_1_|
followed by the real tag number, in base 128, with all but the
final byte having the most significant bit set. The tag must be
represented with as few bytes as possible. High tag numbers are
currently *not* supported.
Next, the length, either a single byte with the most significant bit clear, or
7 6 5 4 3 2 1 0
_________________
|_1_|___________k_|
followed by k additional bytes that gice the length, in network
byte order. The length must be encoded using as few bytes as
possible, and k = 0 is reserved for the "indefinite length form"
which is not supported.
After the length comes the contets. For primitive objects (c == 0),
it's depends on the type. For constructed objects, it's a
concatenation of the DER encodings of zero or more other objects.
*/
enum {
TAG_MASK = 0x1f,
CLASS_MASK = 0xc0,
CONSTRUCTED_MASK = 0x20,
};
/* Initializes the iterator, but one has to call next to get to the
* first element. */
static void
asn1_der_iterator_init(struct asn1_der_iterator *iterator,
unsigned length, const uint8_t *input)
{
iterator->buffer_length = length;
iterator->buffer = input;
iterator->pos = 0;
iterator->type = 0;
}
#define LEFT(i) ((i)->buffer_length - (i)->pos)
#define NEXT(i) ((i)->buffer[(i)->pos++])
/* Gets type and length of the next object. */
enum asn1_iterator_result
asn1_der_iterator_next(struct asn1_der_iterator *i)
{
uint8_t tag;
if (!LEFT(i))
return ASN1_ITERATOR_END;
tag = NEXT(i);
if (!LEFT(i))
return ASN1_ITERATOR_ERROR;
if ( (tag & TAG_MASK) == TAG_MASK)
{
/* FIXME: Long tags not supported */
return ASN1_ITERATOR_ERROR;
}
i->length = NEXT(i);
if (i->length & 0x80)
{
/* FIXME: Large objects not yet supported. */
return ASN1_ITERATOR_ERROR;
}
if (LEFT(i) < i->length)
return ASN1_ITERATOR_ERROR;
i->data = i->buffer + i->pos;
i->pos += i->length;
i->type = tag & TAG_MASK;
i->type |= (tag & CLASS_MASK) << (ASN1_CLASS_SHIFT - 6);
if (tag & CONSTRUCTED_MASK)
{
i->type |= ASN1_TYPE_CONSTRUCTED;
return ASN1_ITERATOR_CONSTRUCTED;
}
else
return ASN1_ITERATOR_PRIMITIVE;
}
enum asn1_iterator_result
asn1_der_iterator_first(struct asn1_der_iterator *i,
unsigned length, const uint8_t *input)
{
asn1_der_iterator_init(i, length, input);
return asn1_der_iterator_next(i);
}
enum asn1_iterator_result
asn1_der_decode_constructed(struct asn1_der_iterator *i,
struct asn1_der_iterator *contents)
{
assert(i->type & ASN1_TYPE_CONSTRUCTED);
return asn1_der_iterator_first(contents, i->length, i->data);
}
int
asn1_der_get_uint32(struct asn1_der_iterator *i,
uint32_t *x)
{
/* Big endian, two's complement, minimum number of octets (except 0,
which is encoded as a single octet */
uint32_t value = 0;
unsigned length = i->length;
unsigned k;
if (!length || length > 5)
return 0;
if (i->data[length - 1] >= 0x80)
/* Signed number */
return 0;
if (length > 1
&& i->data[length -1] == 0
&& i->data[length -2] < 0x80)
/* Non-minimal number of digits */
return 0;
if (length == 5)
{
if (i->data[4])
return 0;
length--;
}
for (value = k = 0; k < length; k++)
value = (value << 8) | i->data[k];
*x = value;
return 1;
}
#if HAVE_LIBGMP
int
asn1_der_get_bignum(struct asn1_der_iterator *i,
mpz_t x, unsigned limit)
{
/* Allow some extra here, for leading sign octets. */
if (limit && (8 * i->length > (16 + limit)))
return 0;
nettle_mpz_set_str_256_s(x, i->length, i->data);
/* FIXME: How to interpret a limit for negative numbers? */
if (limit && mpz_sizeinbase(x, 2) > limit)
return 0;
return 1;
}
#endif /* HAVE_LIBGMP */
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