X-Git-Url: https://git.stg.codes/stg.git/blobdiff_plain/8c6fa3fbaccc22127280bf77a48fab5a3ee0716e..46b0747592074017ff0ea4b33d4a7194235886e5:/libs/smux/der_encoder.c

diff --git a/libs/smux/der_encoder.c b/libs/smux/der_encoder.c
new file mode 100644
index 00000000..6c859e1b
--- /dev/null
+++ b/libs/smux/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;
+}