From de670bd5b2b1dff06b09d4e0b7b6bcb6f5cce93a Mon Sep 17 00:00:00 2001
From: "Owain G. Ainsworth" <oga@conformal.com>
Date: Mon, 17 Mar 2014 17:47:27 +0000
Subject: [PATCH] check for 0 length strings in pubkey parser.

We check length later, but we assumed it was always 1 bytes long. Not
always the case. I'm a little depressed that this bug was there.
---
 pubkey.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/pubkey.go b/pubkey.go
index 070bbc295..72772809c 100644
--- a/pubkey.go
+++ b/pubkey.go
@@ -6,6 +6,7 @@ package btcec
 
 import (
 	"crypto/ecdsa"
+	"errors"
 	"fmt"
 	"math/big"
 )
@@ -53,6 +54,10 @@ func ParsePubKey(pubKeyStr []byte, curve *KoblitzCurve) (key *ecdsa.PublicKey, e
 	pubkey := ecdsa.PublicKey{}
 	pubkey.Curve = curve
 
+	if len(pubKeyStr) == 0 {
+		return nil, errors.New("pubkey string is empty")
+	}
+
 	format := pubKeyStr[0]
 	ybit := (format & 0x1) == 0x1
 	format &= ^byte(0x1)