asn1.c

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/* read from a ASN1 buffer, advancing the buffer pointer */
bool asn1_read(struct asn1_data *data, void *p, int len)
{
	if (!asn1_peek(data, p, len)) {
		data->has_error = true;
		return false;
	}

	data->ofs += len;
	return true;
}

/* read a uint8_t from a ASN1 buffer */
bool asn1_read_uint8(struct asn1_data *data, uint8_t *v)
{
	return asn1_read(data, v, 1);
}

bool asn1_peek_uint8(struct asn1_data *data, uint8_t *v)
{
	return asn1_peek(data, v, 1);
}

bool asn1_peek_tag(struct asn1_data *data, uint8_t tag)
{
	uint8_t b;

	if (asn1_tag_remaining(data) <= 0) {
		return false;
	}

	if (!asn1_peek_uint8(data, &b))
		return false;

	return (b == tag);
}

/* start reading a nested asn1 structure */
bool asn1_start_tag(struct asn1_data *data, uint8_t tag)
{
	uint8_t b;
	struct nesting *nesting;
	
	if (!asn1_read_uint8(data, &b))
		return false;

	if (b != tag) {
		data->has_error = true;
		return false;
	}
	nesting = talloc(data, struct nesting);
	if (!nesting) {
		data->has_error = true;
		return false;
	}

	if (!asn1_read_uint8(data, &b)) {
		return false;
	}

	if (b & 0x80) {
		int n = b & 0x7f;
		if (!asn1_read_uint8(data, &b))
			return false;
		nesting->taglen = b;
		while (n > 1) {
			if (!asn1_read_uint8(data, &b)) 
				return false;
			nesting->taglen = (nesting->taglen << 8) | b;
			n--;
		}
	} else {
		nesting->taglen = b;
	}
	nesting->start = data->ofs;
	nesting->next = data->nesting;
	data->nesting = nesting;
	if (asn1_tag_remaining(data) == -1) {
		return false;
	}
	return !data->has_error;
}

/* stop reading a tag */
bool asn1_end_tag(struct asn1_data *data)
{
	struct nesting *nesting;

	/* make sure we read it all */
	if (asn1_tag_remaining(data) != 0) {
		data->has_error = true;
		return false;
	}

	nesting = data->nesting;

	if (!nesting) {
		data->has_error = true;
		return false;
	}

	data->nesting = nesting->next;
	talloc_free(nesting);
	return true;
}

/* work out how many bytes are left in this nested tag */
int asn1_tag_remaining(struct asn1_data *data)
{
	int remaining;
	if (data->has_error) {
		return -1;
	}

	if (!data->nesting) {
		data->has_error = true;
		return -1;
	}
	remaining = data->nesting->taglen - (data->ofs - data->nesting->start);
	if (remaining > (data->length - data->ofs)) {
		data->has_error = true;
		return -1;
	}
	return remaining;
}

/* read an object ID from a data blob */
bool ber_read_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB blob, const char **OID)
{
	int i;
	uint8_t *b;
	uint_t v;
	char *tmp_oid = NULL;

	if (blob.length < 2) return false;

	b = blob.data;

	tmp_oid = talloc_asprintf(mem_ctx, "%u",  b[0]/40);
	if (!tmp_oid) goto nomem;
	tmp_oid = talloc_asprintf_append_buffer(tmp_oid, ".%u",  b[0]%40);
	if (!tmp_oid) goto nomem;

	for(i = 1, v = 0; i < blob.length; i++) {
		v = (v<<7) | (b[i]&0x7f);
		if ( ! (b[i] & 0x80)) {
			tmp_oid = talloc_asprintf_append_buffer(tmp_oid, ".%u",  v);
			v = 0;
		}
		if (!tmp_oid) goto nomem;
	}

	if (v != 0) {
		talloc_free(tmp_oid);
		return false;
	}

	*OID = tmp_oid;
	return true;

nomem:	
	return false;
}

/* read an object ID from a ASN1 buffer */
bool asn1_read_OID(struct asn1_data *data, TALLOC_CTX *mem_ctx, const char **OID)
{
	DATA_BLOB blob;
	int len;

	if (!asn1_start_tag(data, ASN1_OID)) return false;

	len = asn1_tag_remaining(data);
	if (len < 0) {
		data->has_error = true;
		return false;
	}

	blob = data_blob(NULL, len);
	if (!blob.data) {
		data->has_error = true;
		return false;
	}

	asn1_read(data, blob.data, len);
	asn1_end_tag(data);
	if (data->has_error) {
		data_blob_free(&blob);
		return false;
	}

	if (!ber_read_OID_String(mem_ctx, blob, OID)) {
		data->has_error = true;
		data_blob_free(&blob);
		return false;
	}

	data_blob_free(&blob);
	return true;
}

/* check that the next object ID is correct */
bool asn1_check_OID(struct asn1_data *data, const char *OID)
{
	const char *id;

	if (!asn1_read_OID(data, data, &id)) return false;

	if (strcmp(id, OID) != 0) {
		talloc_free(discard_const(id));
		data->has_error = true;
		return false;
	}
	talloc_free(discard_const(id));
	return true;
}

/* read a LDAPString from a ASN1 buffer */
bool asn1_read_LDAPString(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **s)
{
	int len;
	len = asn1_tag_remaining(data);
	if (len < 0) {
		data->has_error = true;
		return false;
	}
	*s = talloc_array(mem_ctx, char, len+1);
	if (! *s) {
		data->has_error = true;
		return false;
	}
	asn1_read(data, *s, len);
	(*s)[len] = 0;
	return !data->has_error;
}


/* read a GeneralString from a ASN1 buffer */
bool asn1_read_GeneralString(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **s)
{
	if (!asn1_start_tag(data, ASN1_GENERAL_STRING)) return false;
	if (!asn1_read_LDAPString(data, mem_ctx, s)) return false;
	return asn1_end_tag(data);
}


/* read a octet string blob */
bool asn1_read_OctetString(struct asn1_data *data, TALLOC_CTX *mem_ctx, DATA_BLOB *blob)
{
	int len;
	ZERO_STRUCTP(blob);
	if (!asn1_start_tag(data, ASN1_OCTET_STRING)) return false;
	len = asn1_tag_remaining(data);
	if (len < 0) {
		data->has_error = true;
		return false;
	}
	*blob = data_blob_talloc(mem_ctx, NULL, len+1);
	if (!blob->data) {
		data->has_error = true;
		return false;
	}
	asn1_read(data, blob->data, len);
	asn1_end_tag(data);
	blob->length--;
	blob->data[len] = 0;
	
	if (data->has_error) {
		data_blob_free(blob);
		*blob = data_blob(NULL, 0);
		return false;
	}
	return true;
}

bool asn1_read_ContextSimple(struct asn1_data *data, uint8_t num, DATA_BLOB *blob)
{
	int len;
	ZERO_STRUCTP(blob);
	if (!asn1_start_tag(data, ASN1_CONTEXT_SIMPLE(num))) return false;
	len = asn1_tag_remaining(data);
	if (len < 0) {
		data->has_error = true;
		return false;
	}
	*blob = data_blob(NULL, len);
	if ((len != 0) && (!blob->data)) {
		data->has_error = true;
		return false;
	}
	asn1_read(data, blob->data, len);
	asn1_end_tag(data);
	return !data->has_error;
}

/* read an integer without tag*/
bool asn1_read_implicit_Integer(struct asn1_data *data, int *i)
{
	uint8_t b;
	*i = 0;

	while (!data->has_error && asn1_tag_remaining(data)>0) {
		if (!asn1_read_uint8(data, &b)) return false;
		*i = (*i << 8) + b;
	}
	return !data->has_error;	
	
}

/* read an integer */
bool asn1_read_Integer(struct asn1_data *data, int *i)
{
	*i = 0;

	if (!asn1_start_tag(data, ASN1_INTEGER)) return false;
	if (!asn1_read_implicit_Integer(data, i)) return false;
	return asn1_end_tag(data);	
}

/* read an integer */
bool asn1_read_enumerated(struct asn1_data *data, int *v)
{
	*v = 0;
	
	if (!asn1_start_tag(data, ASN1_ENUMERATED)) return false;
	while (!data->has_error && asn1_tag_remaining(data)>0) {
		uint8_t b;
		asn1_read_uint8(data, &b);
		*v = (*v << 8) + b;
	}
	return asn1_end_tag(data);	
}

/* check a enumerated value is correct */
bool asn1_check_enumerated(struct asn1_data *data, int v)
{
	uint8_t b;
	if (!asn1_start_tag(data, ASN1_ENUMERATED)) return false;
	asn1_read_uint8(data, &b);
	asn1_end_tag(data);

	if (v != b)
		data->has_error = false;

	return !data->has_error;
}

/* write an enumerated value to the stream */
bool asn1_write_enumerated(struct asn1_data *data, uint8_t v)
{
	if (!asn1_push_tag(data, ASN1_ENUMERATED)) return false;
	asn1_write_uint8(data, v);
	asn1_pop_tag(data);
	return !data->has_error;
}

/*
  check if a ASN.1 blob is a full tag
*/
NTSTATUS asn1_full_tag(DATA_BLOB blob, uint8_t tag, size_t *packet_size)
{
	struct asn1_data *asn1 = asn1_init(NULL);
	int size;

	NT_STATUS_HAVE_NO_MEMORY(asn1);

	asn1->data = blob.data;
	asn1->length = blob.length;
	asn1_start_tag(asn1, tag);
	if (asn1->has_error) {
		talloc_free(asn1);
		return STATUS_MORE_ENTRIES;
	}
	size = asn1_tag_remaining(asn1) + asn1->ofs;

	talloc_free(asn1);

	if (size > blob.length) {
		return STATUS_MORE_ENTRIES;
	}		

	*packet_size = size;
	return NT_STATUS_OK;
}