Always sign transactions and messages with the correct account (#14)

The account used to sign transactions and messages should be the one
the transaction or message is from. Instead, the last connected account
was being used to sign any messages or transactions.

This was especially problematic considering the last connected account
was not persisted, meaning that signatures were being performed with
the wrong account after a reset (unless the last connected account
happened to be account 0, which was the default).

A mapping of addresses to indexes as been added to the keyring state,
and this mapping has been persisted. This should ensure the correct
account index is used, and thus the correct hd path, each time this
keyring is used for signing.

index.js

@@ -18,6 +18,7 @@ const NETWORK_API_URLS = {
 class LedgerBridgeKeyring extends EventEmitter {
   constructor (opts = {}) {
     super()
+    this.accountIndexes = {}
     this.bridgeUrl = null
     this.type = type
     this.page = 0
@@ -36,6 +37,7 @@ class LedgerBridgeKeyring extends EventEmitter {
     return Promise.resolve({
       hdPath: this.hdPath,
       accounts: this.accounts,
+      accountIndexes: this.accountIndexes,
       bridgeUrl: this.bridgeUrl,
       implementFullBIP44: false,
     })
@@ -45,6 +47,7 @@ class LedgerBridgeKeyring extends EventEmitter {
     this.hdPath = opts.hdPath || hdPathString
     this.bridgeUrl = opts.bridgeUrl || BRIDGE_URL
     this.accounts = opts.accounts || []
+    this.accountIndexes = opts.accountIndexes || {}
     this.implementFullBIP44 = opts.implementFullBIP44 || false
     return Promise.resolve()
   }
@@ -100,6 +103,7 @@ class LedgerBridgeKeyring extends EventEmitter {
             if (this._isBIP44()) {
               const path = this._getPathForIndex(i)
               address = await this.unlock(path)
+              this.accountIndexes[ethUtil.toChecksumAddress(address)] = i
             } else {
               address = this._addressFromIndex(pathBase, i)
             }
@@ -136,6 +140,7 @@ class LedgerBridgeKeyring extends EventEmitter {
       throw new Error(`Address ${address} not found in this keyring`)
     }
     this.accounts = this.accounts.filter(a => a.toLowerCase() !== address.toLowerCase())
+    delete this.accountIndexes[ethUtil.toChecksumAddress(address)]
   }
 
   // tx is an instance of the ethereumjs-transaction class.
@@ -150,7 +155,11 @@ class LedgerBridgeKeyring extends EventEmitter {
 
           let hdPath
           if (this._isBIP44()) {
-            hdPath = this._getPathForIndex(this.unlockedAccount)
+            const checksummedAddress = ethUtil.toChecksumAddress(address)
+            if (!this.accountIndexes[checksummedAddress]) {
+              reject(new Error(`Ledger: Index for address '${checksummedAddress}' not found`))
+            }
+            hdPath = this._getPathForIndex(this.accountIndexes[checksummedAddress])
           } else {
             hdPath = this._toLedgerPath(this._pathFromAddress(address))
           }
@@ -195,7 +204,11 @@ class LedgerBridgeKeyring extends EventEmitter {
         .then(_ => {
           let hdPath
           if (this._isBIP44()) {
-            hdPath = this._getPathForIndex(this.unlockedAccount)
+            const checksummedAddress = ethUtil.toChecksumAddress(withAccount)
+            if (!this.accountIndexes[checksummedAddress]) {
+              reject(new Error(`Ledger: Index for address '${checksummedAddress}' not found`))
+            }
+            hdPath = this._getPathForIndex(this.accountIndexes[checksummedAddress])
           } else {
             hdPath = this._toLedgerPath(this._pathFromAddress(withAccount))
           }