bolt11: support for encoding/decoding and checking.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/Makefile

@@ -20,6 +20,7 @@ LIGHTNINGD_COMMON_OBJS :=			\
 	common/crypto_state.o			\
 	common/derive_basepoints.o		\
 	common/funding_tx.o			\
+	common/hash_u5.o			\
 	common/htlc_state.o			\
 	common/htlc_wire.o			\
 	common/io_debug.o			\
@@ -41,6 +42,7 @@ LIGHTNINGD_COMMON_OBJS :=			\
 LIGHTNINGD_SRC :=				\
 	lightningd/bech32.c			\
 	lightningd/bitcoind.c			\
+	lightningd/bolt11.c			\
 	lightningd/build_utxos.c		\
 	lightningd/chaintopology.c		\
 	lightningd/gossip_control.c		\

lightningd/bolt11.h

@@ -0,0 +1,93 @@
+#ifndef LIGHTNING_LIGHTNINGD_BOLT11_H
+#define LIGHTNING_LIGHTNINGD_BOLT11_H
+#include "config.h"
+
+#include <bitcoin/pubkey.h>
+#include <bitcoin/short_channel_id.h>
+#include <ccan/list/list.h>
+#include <ccan/short_types/short_types.h>
+#include <common/hash_u5.h>
+
+struct lightningd;
+
+/* We only have 10 bits for the field length, meaning < 640 bytes */
+#define BOLT11_FIELD_BYTE_LIMIT ((1 << 10) * 5 / 8)
+
+struct bolt11_field {
+	struct list_node list;
+
+	char tag;
+	u5 *data;
+};
+
+/* BOLT #11:
+ *   * `pubkey` (264 bits)
+ *   * `short_channel_id` (64 bits)
+ *   * `fee` (64 bits, big-endian)
+ *   * `cltv_expiry_delta` (16 bits, big-endian)
+ */
+
+struct route_info {
+	struct pubkey pubkey;
+	struct short_channel_id short_channel_id;
+	u64 fee;
+	u16 cltv_expiry_delta;
+};
+
+struct bolt11 {
+	const struct chainparams *chain;
+	u64 timestamp;
+	u64 *msatoshi; /* NULL if not specified. */
+
+	struct sha256 payment_hash;
+	struct pubkey receiver_id;
+
+	/* description_hash valid iff description is NULL. */
+	const char *description;
+	struct sha256 *description_hash;
+
+	/* How many seconds to pay from @timestamp above. */
+	u64 expiry;
+
+	/* If non-NULL, indicates a fallback address to pay to. */
+	const u8 *fallback;
+
+	/* If non-NULL: array of route arrays */
+	struct route_info **routes;
+
+	/* signature of sha256 of entire thing. */
+	secp256k1_ecdsa_signature sig;
+
+	struct list_head extra_fields;
+};
+
+/* Decodes and checks signature; returns NULL on error; description is
+ * (optional) out-of-band description of payment, for `h` field. */
+struct bolt11 *bolt11_decode(const tal_t *ctx, const char *str,
+			     const char *description, char **fail);
+
+/* Initialize an empty bolt11 struct with optional amount */
+struct bolt11 *new_bolt11(const tal_t *ctx, u64 *msatoshi);
+
+/* Encodes and signs, even if it's nonsense. */
+char *bolt11_encode(const tal_t *ctx,
+                    struct lightningd *ld,
+                    const struct bolt11 *b11, bool n_field);
+
+/**
+ * bolt11_out_check - check a bolt11 struct for validity and consistency
+ * @bolt11: the bolt11
+ * @abortstr: the location to print on aborting, or NULL.
+ *
+ * Note this does not apply to bolt11's we decoded, which may not be spec
+ * compliant.
+ *
+ * If @abortstr is non-NULL, that will be printed in a diagnostic if the bolt11
+ * is invalid, and the function will abort.
+ *
+ * Returns @bolt11 if all OK, NULL if not (it can never return NULL if
+ * @abortstr is set).
+ */
+struct bolt11 *bolt11_out_check(const struct bolt11 *bolt11,
+				const char *abortstr);
+#endif /* LIGHTNING_LIGHTNINGD_BOLT11_H */