psbt: utilities for adding unknown info / proprietary c-lightning keydata

bitcoin/psbt.c

@@ -6,6 +6,7 @@
 #include <bitcoin/signature.h>
 #include <ccan/cast/cast.h>
 #include <ccan/ccan/array_size/array_size.h>
+#include <ccan/ccan/mem/mem.h>
 #include <ccan/tal/str/str.h>
 #include <common/amount.h>
 #include <common/type_to_string.h>
@@ -420,6 +421,105 @@ struct amount_sat psbt_output_get_amount(struct wally_psbt *psbt,
 	assert(amount_asset_is_main(&asset));
 	return amount_asset_to_sat(&asset);
 }
+
+static void add(u8 **key, const void *mem, size_t len)
+{
+	size_t oldlen = tal_count(*key);
+	tal_resize(key, oldlen + len);
+	memcpy(*key + oldlen, memcheck(mem, len), len);
+}
+
+static void add_type(u8 **key, const u8 num)
+{
+	add(key, &num, 1);
+}
+
+static void add_varint(u8 **key, size_t val)
+{
+	u8 vt[VARINT_MAX_LEN];
+	size_t vtlen;
+	vtlen = varint_put(vt, val);
+	add(key, vt, vtlen);
+}
+
+#define LIGHTNING_PROPRIETARY_PREFIX "lightning"
+
+u8 *psbt_make_key(const tal_t *ctx, u8 key_subtype, const u8 *key_data)
+{
+	/**
+	 * BIP174:
+	 * Type: Proprietary Use Type <tt>PSBT_GLOBAL_PROPRIETARY = 0xFC</tt>
+	 ** Key: Variable length identifier prefix, followed
+	 *       by a subtype, followed by the key data itself.
+	 *** <tt>{0xFC}|<prefix>|{subtype}|{key data}</tt>
+	 ** Value: Any value data as defined by the proprietary type user.
+	 *** <tt><data></tt>
+	 */
+	u8 *key = tal_arr(ctx, u8, 0);
+	add_type(&key, PSBT_PROPRIETARY_TYPE);
+	add_varint(&key, strlen(LIGHTNING_PROPRIETARY_PREFIX));
+	add(&key, LIGHTNING_PROPRIETARY_PREFIX,
+	    strlen(LIGHTNING_PROPRIETARY_PREFIX));
+	add_type(&key, key_subtype);
+	if (key_data)
+		add(&key, key_data, tal_bytelen(key_data));
+	return key;
+}
+
+void psbt_input_add_unknown(struct wally_psbt_input *in,
+			    const u8 *key,
+			    const void *value,
+			    size_t value_len)
+{
+	if (wally_map_add(&in->unknowns,
+			  cast_const(unsigned char *, key), tal_bytelen(key),
+			  (unsigned char *) memcheck(value, value_len), value_len)
+			!= WALLY_OK)
+		abort();
+}
+
+void *psbt_get_unknown(const struct wally_map *map,
+		       const u8 *key,
+		       size_t *val_len)
+{
+	size_t index;
+
+	if (wally_map_find(map, key, tal_bytelen(key), &index) != WALLY_OK)
+		return NULL;
+
+	/* Zero: item not found. */
+	if (index == 0)
+		return NULL;
+
+	/* ++: item is at this index minus 1 */
+	*val_len = map->items[index - 1].value_len;
+	return map->items[index - 1].value;
+}
+
+void *psbt_get_lightning(const struct wally_map *map,
+			 const u8 proprietary_type,
+			 size_t *val_len)
+{
+	void *res;
+	u8 *key = psbt_make_key(NULL, proprietary_type, NULL);
+	res = psbt_get_unknown(map, key, val_len);
+	tal_free(key);
+	return res;
+}
+
+
+void psbt_output_add_unknown(struct wally_psbt_output *out,
+			     const u8 *key,
+			     const void *value,
+			     size_t value_len)
+{
+	if (wally_map_add(&out->unknowns,
+			  cast_const(unsigned char *, key), tal_bytelen(key),
+			  (unsigned char *) memcheck(value, value_len), value_len)
+			!= WALLY_OK)
+		abort();
+}
+
 struct wally_tx *psbt_finalize(struct wally_psbt *psbt, bool finalize_in_place)
 {
 	struct wally_psbt *tmppsbt;
@@ -518,6 +618,8 @@ char *psbt_to_b64(const tal_t *ctx, const struct wally_psbt *psbt)
 	wally_free_string(serialized_psbt);
 	return ret_val;
 }
+
+/* Do not remove this line, it is magic */
 REGISTER_TYPE_TO_STRING(wally_psbt, psbt_to_b64);
 
 const u8 *psbt_get_bytes(const tal_t *ctx, const struct wally_psbt *psbt,

bitcoin/psbt.h

@@ -10,6 +10,7 @@ struct wally_psbt_input;
 struct wally_tx;
 struct wally_tx_input;
 struct wally_tx_output;
+struct wally_map;
 struct amount_asset;
 struct amount_sat;
 struct bitcoin_signature;
@@ -59,6 +60,16 @@ void psbt_txid(const struct wally_psbt *psbt, struct bitcoin_txid *txid,
 
 struct wally_tx *psbt_finalize(struct wally_psbt *psbt, bool finalize_in_place);
 
+/* psbt_make_key - Create a new, proprietary c-lightning key
+ *
+ * @ctx - allocation context
+ * @key_subtype - type for this key
+ * @key_data - any extra data to append to the key
+ *
+ * Returns a proprietary-prefixed key.
+ */
+u8 *psbt_make_key(const tal_t *ctx, u8 key_subtype, const u8 *key_data);
+
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
 					struct wally_tx_input *input,
 					size_t insert_at);
@@ -112,6 +123,49 @@ void psbt_elements_input_init_witness(struct wally_psbt *psbt, size_t in,
 				      const u8 *nonce);
 bool psbt_input_set_redeemscript(struct wally_psbt *psbt, size_t in,
 				 const u8 *redeemscript);
+/* psbt_input_add_unknown - Add the given Key-Value to the psbt's input keymap
+ * @in - psbt input to add key-value to
+ * @key - key for key-value pair
+ * @value - value to add
+ * @value_len - length of {@value}
+ */
+void psbt_input_add_unknown(struct wally_psbt_input *in,
+			    const u8 *key,
+			    const void *value,
+			    size_t value_len);
+/* psbt_get_unknown - Fetch the value from the given map at key
+ *
+ * @map - map of unknowns to search for key
+ * @key - key of key-value pair to return value for
+ * @value_len - (out) length of value (if found)
+ *
+ * Returns: value at @key, or NULL if not found */
+void *psbt_get_unknown(const struct wally_map *map,
+		       const u8 *key,
+		       size_t *val_len);
+
+/* psbt_get_lightning - Fetch a proprietary lightning value from the given map
+ *
+ * @map - map of unknowns to search for key
+ * @proprietary_type - type no. to look for
+ * @val_len - (out) length of value (if found)
+ *
+ * Returns: value of type {proprietary_type}, or NULL if not found */
+void *psbt_get_lightning(const struct wally_map *map,
+			 const u8 proprietary_type,
+			 size_t *val_len);
+
+/* psbt_output_add_unknown - Add the given Key-Value to the psbt's output keymap
+ *
+ * @out - psbt output to add key-value to
+ * @key - key for key-value pair
+ * @value - value to add
+ * @value_len - length of {@value}
+ */
+void psbt_output_add_unknown(struct wally_psbt_output *out,
+			     const u8 *key, const void *value,
+			     size_t value_len);
+
 /* psbt_input_get_amount - Returns the value of this input
  *
  * @psbt - psbt