Use a compiler to marshall/unmarshall the sessions

This way changes are easier, all is needed is to change the session.asn1
file to add or remove elements, and different session types can also be
supported at the same time.

1 files changed, 199 insertions, 0 deletions

diff --git a/src/asn1c/der_encoder.c b/src/asn1c/der_encoder.c
new file mode 100644
index 0000000..6c859e1
--- /dev/null
+++ b/src/asn1c/der_encoder.c
@@ -0,0 +1,199 @@
+/*-
+ * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include <asn_internal.h>
+#include <errno.h>
+
+static ssize_t der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
+	asn_app_consume_bytes_f *cb, void *app_key, int constructed);
+
+/*
+ * The DER encoder of any type.
+ */
+asn_enc_rval_t
+der_encode(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr,
+	asn_app_consume_bytes_f *consume_bytes, void *app_key) {
+
+	ASN_DEBUG("DER encoder invoked for %s",
+		type_descriptor->name);
+
+	/*
+	 * Invoke type-specific encoder.
+	 */
+	return type_descriptor->der_encoder(type_descriptor,
+		struct_ptr,	/* Pointer to the destination structure */
+		0, 0,
+		consume_bytes, app_key);
+}
+
+/*
+ * Argument type and callback necessary for der_encode_to_buffer().
+ */
+typedef struct enc_to_buf_arg {
+	void *buffer;
+	size_t left;
+} enc_to_buf_arg;
+static int encode_to_buffer_cb(const void *buffer, size_t size, void *key) {
+	enc_to_buf_arg *arg = (enc_to_buf_arg *)key;
+
+	if(arg->left < size)
+		return -1;	/* Data exceeds the available buffer size */
+
+	memcpy(arg->buffer, buffer, size);
+	arg->buffer = ((char *)arg->buffer) + size;
+	arg->left -= size;
+
+	return 0;
+}
+
+/*
+ * A variant of the der_encode() which encodes the data into the provided buffer
+ */
+asn_enc_rval_t
+der_encode_to_buffer(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr,
+	void *buffer, size_t buffer_size) {
+	enc_to_buf_arg arg;
+	asn_enc_rval_t ec;
+
+	arg.buffer = buffer;
+	arg.left = buffer_size;
+
+	ec = type_descriptor->der_encoder(type_descriptor,
+		struct_ptr,	/* Pointer to the destination structure */
+		0, 0, encode_to_buffer_cb, &arg);
+	if(ec.encoded != -1) {
+		assert(ec.encoded == (ssize_t)(buffer_size - arg.left));
+		/* Return the encoded contents size */
+	}
+	return ec;
+}
+
+
+/*
+ * Write out leading TL[v] sequence according to the type definition.
+ */
+ssize_t
+der_write_tags(asn_TYPE_descriptor_t *sd,
+		size_t struct_length,
+		int tag_mode, int last_tag_form,
+		ber_tlv_tag_t tag,	/* EXPLICIT or IMPLICIT tag */
+		asn_app_consume_bytes_f *cb,
+		void *app_key) {
+	ber_tlv_tag_t *tags;	/* Copy of tags stream */
+	int tags_count;		/* Number of tags */
+	size_t overall_length;
+	ssize_t *lens;
+	int i;
+
+	ASN_DEBUG("Writing tags (%s, tm=%d, tc=%d, tag=%s, mtc=%d)",
+		sd->name, tag_mode, sd->tags_count,
+		ber_tlv_tag_string(tag),
+		tag_mode
+			?(sd->tags_count+1
+				-((tag_mode == -1) && sd->tags_count))
+			:sd->tags_count
+	);
+
+	if(tag_mode) {
+		/*
+		 * Instead of doing shaman dance like we do in ber_check_tags(),
+		 * allocate a small array on the stack
+		 * and initialize it appropriately.
+		 */
+		int stag_offset;
+		tags = (ber_tlv_tag_t *)alloca((sd->tags_count + 1) * sizeof(ber_tlv_tag_t));
+		if(!tags) {	/* Can fail on !x86 */
+			errno = ENOMEM;
+			return -1;
+		}
+		tags_count = sd->tags_count
+			+ 1	/* EXPLICIT or IMPLICIT tag is given */
+			- ((tag_mode == -1) && sd->tags_count);
+		/* Copy tags over */
+		tags[0] = tag;
+		stag_offset = -1 + ((tag_mode == -1) && sd->tags_count);
+		for(i = 1; i < tags_count; i++)
+			tags[i] = sd->tags[i + stag_offset];
+	} else {
+		tags = sd->tags;
+		tags_count = sd->tags_count;
+	}
+
+	/* No tags to write */
+	if(tags_count == 0)
+		return 0;
+
+	lens = (ssize_t *)alloca(tags_count * sizeof(lens[0]));
+	if(!lens) {
+		errno = ENOMEM;
+		return -1;
+	}
+
+	/*
+	 * Array of tags is initialized.
+	 * Now, compute the size of the TLV pairs, from right to left.
+	 */
+	overall_length = struct_length;
+	for(i = tags_count - 1; i >= 0; --i) {
+		lens[i] = der_write_TL(tags[i], overall_length, 0, 0, 0);
+		if(lens[i] == -1) return -1;
+		overall_length += lens[i];
+		lens[i] = overall_length - lens[i];
+	}
+
+	if(!cb) return overall_length - struct_length;
+
+	ASN_DEBUG("%s %s TL sequence (%d elements)",
+		cb?"Encoding":"Estimating", sd->name, tags_count);
+
+	/*
+	 * Encode the TL sequence for real.
+	 */
+	for(i = 0; i < tags_count; i++) {
+		ssize_t len;
+		int _constr;
+
+		/* Check if this tag happens to be constructed */
+		_constr = (last_tag_form || i < (tags_count - 1));
+
+		len = der_write_TL(tags[i], lens[i], cb, app_key, _constr);
+		if(len == -1) return -1;
+	}
+
+	return overall_length - struct_length;
+}
+
+static ssize_t
+der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
+		asn_app_consume_bytes_f *cb, void *app_key,
+		int constructed) {
+	uint8_t buf[32];
+	size_t size = 0;
+	int buf_size = cb?sizeof(buf):0;
+	ssize_t tmp;
+
+	/* Serialize tag (T from TLV) into possibly zero-length buffer */
+	tmp = ber_tlv_tag_serialize(tag, buf, buf_size);
+	if(tmp == -1 || tmp > (ssize_t)sizeof(buf)) return -1;
+	size += tmp;
+
+	/* Serialize length (L from TLV) into possibly zero-length buffer */
+	tmp = der_tlv_length_serialize(len, buf+size, buf_size?buf_size-size:0);
+	if(tmp == -1) return -1;
+	size += tmp;
+
+	if(size > sizeof(buf))
+		return -1;
+
+	/*
+	 * If callback is specified, invoke it, and check its return value.
+	 */
+	if(cb) {
+		if(constructed) *buf |= 0x20;
+		if(cb(buf, size, app_key) < 0)
+			return -1;
+	}
+
+	return size;
+}