lib/signature: implement personal_recover (eip 191) (#21)

* lib/signature: implement personal_recover (eip 191)

* eth/chains: add edge case for ledger wallets

* spec: add another test case for mycrypto

* lib: clean up

* spec: clean up

lib/eth.rb

@@ -20,5 +20,6 @@ module Eth
 require 'eth/address'
 require 'eth/chains'
 require 'eth/key'
+require 'eth/signature'
 require 'eth/utils'
 require 'eth/version'

lib/eth/address.rb

@@ -54,13 +54,7 @@ def checksummed
 
       Utils.prefix_hex(cased.join)
     end
-
-    # Generate a checksummed address string. Alias for `checksummed`.
-    #
-    # @return [String] prefixed hexstring representing an checksummed address.
-    def to_s
-      checksummed
-    end
+    alias :to_s :checksummed
 
     private
 

lib/eth/chains.rb

@@ -93,28 +93,36 @@ def is_legacy? v
     # EIP-155 chain ID.
     #
     # @param v [Integer] the signature's `v` value
-    # @param chain [Integer] the chain id the signature was generated on.
+    # @param chain_id [Integer] the chain id the signature was generated on.
     # @return [Integer] the recovery id corresponding to `v`.
     # @raise [ArgumentError] if the given `v` is invalid.
-    def to_recov v, chain = ETHEREUM
-      x = 0 + 2 * chain + 35
-      y = 1 + 2 * chain + 35
-      if  is_legacy? v
+    def to_recovery_id v, chain_id = ETHEREUM
+      e = 0 + 2 * chain_id + 35
+      i = 1 + 2 * chain_id + 35
+      if [0, 1].include? v
+
+        # some wallets are using a `v` of 0 or 1 (ledger)
+        return v
+      elsif is_legacy? v
+
+        # this is the pre-EIP-155 legacy case
         return v - 27
-      elsif [x, y].include? v
-        return v - 35 - 2 * chain
+      elsif [e, i].include? v
+
+        # this is the EIP-155 case
+        return v - 35 - 2 * chain_id
       else
-        raise ArgumentError, "Invalid v value for chain #{chain}. Invalid chain ID?"
+        raise ArgumentError, "Invalid v value for chain ID #{chain_id}. Invalid chain ID?"
       end
     end
 
     # Converts a recovery ID into the expected `v` on a given chain.
     #
-    # @param recov [Integer] signature recovery id.
-    # @param chain [Integer] the chain id the signature was generated on.
+    # @param recovery_id [Integer] signature recovery id.
+    # @param chain_id [Integer] the chain id the signature was generated on.
     # @return [Integer] the signature's `v` value.
-    def to_v recov, chain = ETHEREUM
-      v = 2 * chain + 35 + recov
+    def to_v recovery_id, chain_id = ETHEREUM
+      v = 2 * chain_id + 35 + recovery_id
     end
   end
 end

lib/eth/signature.rb

@@ -0,0 +1,55 @@
+# Copyright (c) 2016-2022 The Ruby-Eth Contributors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require 'rbsecp256k1'
+
+# Provides the `Eth` module.
+module Eth
+
+  # Defines handy tools for verifying and recovering signatures.
+  module Signature
+    extend self
+
+    # Prefix message as per EIP-191 with 0x19 to ensure the data is not
+    # valid RLP and thus not mistaken for a transaction.
+    # EIP-191 Version byte: 0x45 (E)
+    # ref: https://eips.ethereum.org/EIPS/eip-191
+    #
+    # @param message [String] the message string to be prefixed.
+    # @return [String] an EIP-191 prefixed string
+    def prefix_message message
+      "\x19Ethereum Signed Message:\n#{message.size}#{message}"
+    end
+
+    # Recovers a uncompressed public key from a message and a signature
+    # on a given chain.
+    #
+    # @param message [String] the message string.
+    # @param signature [String] the hex string containing the signature.
+    # @param chain_id [Integer] the chain ID used to sign.
+    # @return [String] an uncompressed public key hex.
+    def personal_recover message, signature, chain_id = Chains::ETHEREUM
+      context = Secp256k1::Context.new
+      rotated_signature = Utils.hex_to_bin(signature).bytes.rotate -1
+      signature = rotated_signature[1..-1].pack 'c*'
+      v = rotated_signature.first
+      recovery_id = Chains.to_recovery_id v, chain_id
+      recoverable_signature = context.recoverable_signature_from_compact signature, recovery_id
+      prefixed_message = prefix_message message
+      hashed_message = Utils.keccak256 prefixed_message
+      public_key = recoverable_signature.recover_public_key hashed_message
+      Utils.bin_to_hex public_key.uncompressed
+    end
+  end
+end

spec/eth/chains_spec.rb

@@ -57,26 +57,28 @@
       expect(Eth::Chains.to_v 0, Eth::Chains::PRIVATE_GETH).to be 2709
     end
     it "can recover v from ethereum recovery id" do
-      expect(Eth::Chains.to_recov 37).to be 0
-      expect(Eth::Chains.to_recov 38).to be 1
+      expect(Eth::Chains.to_recovery_id 37).to be 0
+      expect(Eth::Chains.to_recovery_id 38).to be 1
 
       # legacy v
-      expect(Eth::Chains.to_recov 27).to be 0
-      expect(Eth::Chains.to_recov 28).to be 1
+      expect(Eth::Chains.to_recovery_id 0).to be 0
+      expect(Eth::Chains.to_recovery_id 1).to be 1
+      expect(Eth::Chains.to_recovery_id 27).to be 0
+      expect(Eth::Chains.to_recovery_id 28).to be 1
     end
     it "can recover v from other chain's recovery id" do
-      expect(Eth::Chains.to_recov 157, Eth::Chains::CLASSIC).to be 0
-      expect(Eth::Chains.to_recov 236, Eth::Chains::XDAI).to be 1
-      expect(Eth::Chains.to_recov 84357, Eth::Chains::ARBITRUM).to be 0
-      expect(Eth::Chains.to_recov 160, Eth::Chains::MORDEN_CLASSIC).to be 1
-      expect(Eth::Chains.to_recov 875, Eth::Chains::GOERLI_OPTIMISM).to be 0
-      expect(Eth::Chains.to_recov 843258, Eth::Chains::RINKEBY_ARBITRUM).to be 1
-      expect(Eth::Chains.to_recov 2709, Eth::Chains::PRIVATE_GETH).to be 0
+      expect(Eth::Chains.to_recovery_id 157, Eth::Chains::CLASSIC).to be 0
+      expect(Eth::Chains.to_recovery_id 236, Eth::Chains::XDAI).to be 1
+      expect(Eth::Chains.to_recovery_id 84357, Eth::Chains::ARBITRUM).to be 0
+      expect(Eth::Chains.to_recovery_id 160, Eth::Chains::MORDEN_CLASSIC).to be 1
+      expect(Eth::Chains.to_recovery_id 875, Eth::Chains::GOERLI_OPTIMISM).to be 0
+      expect(Eth::Chains.to_recovery_id 843258, Eth::Chains::RINKEBY_ARBITRUM).to be 1
+      expect(Eth::Chains.to_recovery_id 2709, Eth::Chains::PRIVATE_GETH).to be 0
     end
     it "raises an error for invalid v on chain ids" do
-      expect {Eth::Chains.to_recov 0}.to raise_error ArgumentError
-      expect {Eth::Chains.to_recov 36}.to raise_error ArgumentError
-      expect {Eth::Chains.to_recov 843258, Eth::Chains::PRIVATE_GETH}.to raise_error ArgumentError
+      expect {Eth::Chains.to_recovery_id -1}.to raise_error ArgumentError
+      expect {Eth::Chains.to_recovery_id 36}.to raise_error ArgumentError
+      expect {Eth::Chains.to_recovery_id 843258, Eth::Chains::PRIVATE_GETH}.to raise_error ArgumentError
     end
   end
 end

spec/eth/signature_spec.rb

@@ -0,0 +1,33 @@
+require 'spec_helper'
+
+describe Eth::Signature do
+  describe ".personal_recover" do
+
+    it "can recover a public key from a signature generated with metamask" do
+      message = "test"
+      signature = "3eb24bd327df8c2b614c3f652ec86efe13aa721daf203820241c44861a26d37f2bffc6e03e68fc4c3d8d967054c9cb230ed34339b12ef89d512b42ae5bf8c2ae1c"
+      public_hex = "043e5b33f0080491e21f9f5f7566de59a08faabf53edbc3c32aaacc438552b25fdde531f8d1053ced090e9879cbf2b0d1c054e4b25941dab9254d2070f39418afc"
+      expect(Eth::Signature.personal_recover(message, signature).to_s).to eq public_hex
+    end
+
+    it "can recover a public key from a signature generated with ledger" do
+      message = "test"
+      signature = "0x5c433983b23738940ce256c59d5bc6a3d5fd12c5bc9bdbf0ffdffb7be1a09d1815ca1db167c61a10945837f3fb4821086d6656b4fa6ede9c4d1aeaf07e2b0adf01"
+      public_hex = "04e51ff5abc511f2fda0f893c10054123e92527b5e69e24cca538e74edbd604508259e1b265b54628bc8024fb791e459f67adb770b20962eb38fabe8b86f2aebaa"
+      expect(Eth::Signature.personal_recover message, signature).to eq public_hex
+    end
+
+    it "can recover an address from a signature generated with mycrypto" do
+      alice = Eth::Address.new '0x4fCA53a6658648060e0a1Ca8427Abdd6063eDf6A'
+      message = "Hello World!"
+      signature = "0x21fbf0696d5e0aa2ef41a2b4ffb623bcaf070461d61cf7251c74161f82fec3a4370854bc0a34b3ab487c1bc021cd318c734c51ae29374f2beb0e6f2dd49b4bf41c"
+      expect(Eth::Utils.public_key_to_address(Eth::Signature.personal_recover(message, signature)).to_s).to eq alice.to_s
+
+      # ref: https://support.mycrypto.com/how-to/getting-started/how-to-sign-and-verify-messages-on-ethereum/
+      bob = Eth::Address.new '0x2a3052ef570a031400BffD61438b2D19e0E8abef'
+      message = "This is proof that I, user A, have access to this address."
+      signature = "0x4e1ce8ea60bc6dfd4068a35462612495850cb645a1c9f475eb969bff21d0b0fb414112aaf13f01dd18a3527cb648cdd51b618ae49d4999112c33f86b7b26e9731b"
+      expect(Eth::Utils.public_key_to_address(Eth::Signature.personal_recover(message, signature)).to_s).to eq bob.to_s
+    end
+  end
+end