lightningd: have makesecret take hex or string (just like datastore)

Changelog-Added: JSON-RPC: `makesecret` can take a string argument instead of hex.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

doc/lightning-makesecret.7.md

@@ -4,14 +4,15 @@ lightning-makesecret -- Command for deriving pseudorandom key from HSM
 SYNOPSIS
 --------
 
-**makesecret** *hex*
+**makesecret** [*hex*] [*string*]
 
 DESCRIPTION
 -----------
 
 The **makesecret** RPC command derives a secret key from the HSM_secret.
 
-The *hex* can be any hex data.
+One of *hex* or *string* must be specified: *hex* can be any hex data,
+*string* is a UTF-8 string interpreted literally.
 
 RETURN VALUE
 ------------
@@ -32,11 +33,6 @@ AUTHOR
 
 Aditya <<aditya.sharma20111@gmail.com>> is mainly responsible.
 
-SEE ALSO
---------
-
-lightning-getsharedsecret(7)
-
 RESOURCES
 ---------
 

doc/schemas/makesecret.request.json

@@ -2,13 +2,15 @@
   "$schema": "http://json-schema.org/draft-07/schema#",
   "type": "object",
   "additionalProperties": false,
-  "required": [
+  "required": [],
-    "hex"
-  ],
   "properties": {
     "hex": {
       "type": "hex",
       "description": "This will be used for deriving the secret"
+    },
+    "string": {
+      "type": "string",
+      "description": "This will be used for deriving the secret"
     }
   }
 }

lightningd/hsm_control.c

@@ -131,16 +131,30 @@ static struct command_result *json_makesecret(struct command *cmd,
 					   const jsmntok_t *obj UNNEEDED,
 					   const jsmntok_t *params)
 {
-	u8 *info;
+	u8 *data;
+	const char *strdata;
 	struct json_stream *response;
 	struct secret secret;
 
 	if (!param(cmd, buffer, params,
-		   p_req("hex", param_bin_from_hex, &info),
+		   p_opt("hex", param_bin_from_hex, &data),
+		   p_opt("string", param_string, &strdata),
 		   NULL))
 		return command_param_failed();
 
-	u8 *msg = towire_hsmd_derive_secret(cmd, info);
+	if (strdata) {
+		if (data)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "Cannot have both hex and string");
+		data = tal_dup_arr(cmd, u8, (u8 *)strdata, strlen(strdata), 0);
+	} else {
+		if (!data)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "Must have either hex or string");
+	}
+
+
+	u8 *msg = towire_hsmd_derive_secret(cmd, data);
 	if (!wire_sync_write(cmd->ld->hsm_fd, take(msg)))
 		return command_fail(cmd, LIGHTNINGD,
                      "Could not write to HSM: %s", strerror(errno));

tests/test_misc.py

@@ -2281,6 +2281,10 @@ def test_makesecret(node_factory):
     assert l1.rpc.makesecret(hex="736362207365637265")["secret"] != secret
     assert l1.rpc.makesecret(hex="7363622073656372657401")["secret"] != secret
 
+    # Using string works!
+    assert l1.rpc.makesecret(string="scb secret")["secret"] == secret
+    assert l1.rpc.makesecret(None, "scb secret")["secret"] == secret
+
 
 def test_staticbackup(node_factory):
     """