Incorrect validation on keysend route hints

[Evanfeenstra]

Issue and Steps to Reproduce

The param_routehint_array function here https://github.com/ElementsProject/lightning/blob/master/common/json_param.c#L953 checks if the RoutehintList is an array (JSMN_ARRAY). However the RoutehintList is actually an object that has the array of hints inside a hints field https://github.com/ElementsProject/lightning/blob/master/cln-grpc/proto/primitives.proto#L73. The param_routehint function looks like it has the same problem.

You can try it using a cln-grpc client, like in this example https://github.com/Evanfeenstra/cln-grpc-routehints-test/blob/master/src/cln.rs#L50. The exact error message is:

Routehint array routehints (\\"{\\"hints\\":[{\\"hops\\":[{\\"expirydelta\\":40,\\"feebase\\":\\"1000msat\\",\\"feeprop\\":1,\\"id\\":\\"02c7046d20f62012362ccf835fe5b4d4a1708e518592f216afeefabeadfc20154b\\",\\"scid\\":\\"1x5x1\\"}]}]}\\") is not an array

[cdecker]

Hm, that's definitely wrong on my side. Seems like this is the only case of a 2D array, which is treated a bit differently in the code generation tool. I will:

• Add a custom conversion for routehints if not already present
• Amend the msggen to either not handle 2D arrays or fix its behavior
• Publish a new version to crates.io

However I am going to be offline till end of month, hopefully that is not too late :-)

[cdecker]

Hi @Evanfeenstra, I pushed a preliminary fix as #6154. It converts the custom types correctly to the 2d array now. For cln-grpc the inverse conversion is not required but we may want it at some time in the future, hence why there are the todo!() markers. I'll push the new version to crate.io as soon as the PR is merged ^^

[Evanfeenstra]

thanks for working on it @cdecker !