Add an optional verifier to crowdloan

[xlc]

This will allow crowd loan owner to enforce any custom policy offchain for contributors by requiring a valid signature before accept a contribution.

TODOs:

• docs
• test
• think about replay attack

Replaces #2230

[xlc]

I've update the code so it benchmark with the signature case, so it will overestimate for non signature case but I think that's fine.

But because crowdloan is not added to any runtime so I can't run the benchmark code to verify if my change actually works.

[xlc]

Actually my benchmark code doesn't work because the signing API is not available in wasm unless full_crypto feature is enabled. Is there any workaround or we just need to enable full_crypto when benchmarking? @shawntabrizi

[bkchr]

Actually my benchmark code doesn't work because the signing API is not available in wasm unless full_crypto feature is enabled. Is there any workaround or we just need to enable full_crypto when benchmarking? @shawntabrizi

What signing api do you need?

[xlc]

https://github.com/paritytech/substrate/blob/26f3d6826a181674257b8e9fc708aa04b49dc73c/primitives/core/src/ed25519.rs#L424-L425

So I can sign something and get it verified in the benchmarked code

[bkchr]

Why don't you use https://github.com/paritytech/substrate/blob/26f3d6826a181674257b8e9fc708aa04b49dc73c/primitives/io/src/lib.rs#L468?

[xlc]

How do I inject key into the crypto store?

[bkchr]

https://github.com/paritytech/substrate/blob/26f3d6826a181674257b8e9fc708aa04b49dc73c/primitives/io/src/lib.rs#L456

[xlc]

@bkchr CI failed with error:

---- crowdloan::benchmarking::tests::test_benchmarks stdout ----
783thread 'crowdloan::benchmarking::tests::test_benchmarks' panicked at 'No `keystore` associated for the current context!', /usr/local/cargo/git/checkouts/substrate-7e08433d4c370a21/09ba69f/primitives/io/src/lib.rs:459:14
784stack backtrace:
785   0: rust_begin_unwind
786             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/std/src/panicking.rs:495:5
787   1: core::panicking::panic_fmt
788             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/core/src/panicking.rs:92:14
789   2: core::option::expect_failed
790             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/core/src/option.rs:1260:5
791   3: <&mut dyn sp_externalities::Externalities as sp_io::crypto::Crypto>::ed25519_generate_version_1
792   4: std::thread::local::LocalKey<T>::with
793   5: tracing::span::Span::in_scope
794   6: sp_io::crypto::ed25519_generate_version_1
795   7: sp_io::crypto::ed25519_generate
796   8: polkadot_runtime_common::crowdloan::benchmarking::create_fund
797   9: <polkadot_runtime_common::crowdloan::benchmarking::SelectedBenchmark as frame_benchmarking::utils::BenchmarkingSetup<T>>::instance
798  10: polkadot_runtime_common::crowdloan::benchmarking::test_benchmark_create::{{closure}}
799  11: std::thread::local::LocalKey<T>::with
800  12: polkadot_runtime_common::crowdloan::benchmarking::tests::test_benchmarks
801  13: core::ops::function::FnOnce::call_once
802             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/core/src/ops/function.rs:227:5

[xlc]

I have the keystone working in test but not sure if it will work in runtime benchmark.

Also another issue is in the real runtime, we will likely be using MultiSignature but TestSignature is used in mock.

But there is no appropriate interface to create signature so I am using let sig = T::ContributionSignature::decode(&mut &sig.encode()[..]).unwrap(); but it only works for MultiSignature, not TestSignature.

Maybe we need to add some new benchmarking only method to trait Verify? @shawntabrizi

[xlc]

Updated to only support ed25519 to make it simpler

[xlc]

This is ready for review

[gavofyork]

@shawntabrizi you ok with this?

[shawntabrizi]

@xlc ive made it support MultiSigner and MultiSignature for ed25519, sr25519, and edcsa