cmd/clef, signer: initial poc of the standalone signer (#16154)

* signer: introduce external signer command

* cmd/signer, rpc: Implement new signer. Add info about remote user to Context

* signer: refactored request/response, made use of urfave.cli

* cmd/signer: Use common flags

* cmd/signer: methods to validate calldata against abi

* cmd/signer: work on abi parser

* signer: add mutex around UI

* cmd/signer: add json 4byte directory, remove passwords from api

* cmd/signer: minor changes

* cmd/signer: Use ErrRequestDenied, enable lightkdf

* cmd/signer: implement tests

* cmd/signer: made possible for UI to modify tx parameters

* cmd/signer: refactors, removed channels in ui comms, added UI-api via stdin/out

* cmd/signer: Made lowercase json-definitions, added UI-signer test functionality

* cmd/signer: update documentation

* cmd/signer: fix bugs, improve abi detection, abi argument display

* cmd/signer: minor change in json format

* cmd/signer: rework json communication

* cmd/signer: implement mixcase addresses in API, fix json id bug

* cmd/signer: rename fromaccount, update pythonpoc with new json encoding format

* cmd/signer: make use of new abi interface

* signer: documentation

* signer/main: remove redundant  option

* signer: implement audit logging

* signer: create package 'signer', minor changes

* common: add 0x-prefix to mixcaseaddress in json marshalling + validation

* signer, rules, storage: implement rules + ephemeral storage for signer rules

* signer: implement OnApprovedTx, change signing response (API BREAKAGE)

* signer: refactoring + documentation

* signer/rules: implement dispatching to next handler

* signer: docs

* signer/rules: hide json-conversion from users, ensure context is cleaned

* signer: docs

* signer: implement validation rules, change signature of call_info

* signer: fix log flaw with string pointer

* signer: implement custom 4byte databsae that saves submitted signatures

* signer/storage: implement aes-gcm-backed credential storage

* accounts: implement json unmarshalling of url

* signer: fix listresponse, fix gas->uint64

* node: make http/ipc start methods public

* signer: add ipc capability+review concerns

* accounts: correct docstring

* signer: address review concerns

* rpc: go fmt -s

* signer: review concerns+ baptize Clef

* signer,node: move Start-functions to separate file

* signer: formatting

signer/storage/storage.go

@@ -0,0 +1,62 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+//
+
+package storage
+
+import (
+	"fmt"
+)
+
+type Storage interface {
+	// Put stores a value by key. 0-length keys results in no-op
+	Put(key, value string)
+	// Get returns the previously stored value, or the empty string if it does not exist or key is of 0-length
+	Get(key string) string
+}
+
+// EphemeralStorage is an in-memory storage that does
+// not persist values to disk. Mainly used for testing
+type EphemeralStorage struct {
+	data      map[string]string
+	namespace string
+}
+
+func (s *EphemeralStorage) Put(key, value string) {
+	if len(key) == 0 {
+		return
+	}
+	fmt.Printf("storage: put %v -> %v\n", key, value)
+	s.data[key] = value
+}
+
+func (s *EphemeralStorage) Get(key string) string {
+	if len(key) == 0 {
+		return ""
+	}
+	fmt.Printf("storage: get %v\n", key)
+	if v, exist := s.data[key]; exist {
+		return v
+	}
+	return ""
+}
+
+func NewEphemeralStorage() Storage {
+	s := &EphemeralStorage{
+		data: make(map[string]string),
+	}
+	return s
+}