From 162bff99b2eca4716c9617415dfe6825292552d1 Mon Sep 17 00:00:00 2001
From: Jae Kwon <jkwon.work@gmail.com>
Date: Wed, 16 Jul 2014 17:23:13 -0700
Subject: [PATCH] addrbook key is more secure

---
 common/random.go | 32 +++++++++++++++++++++++++++++++-
 p2p/addrbook.go  |  2 +-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/common/random.go b/common/random.go
index 6e92d96df..d68ac6da5 100644
--- a/common/random.go
+++ b/common/random.go
@@ -1,6 +1,8 @@
 package common
 
 import (
+	crand "crypto/rand"
+	"encoding/hex"
 	"math/rand"
 )
 
@@ -8,7 +10,19 @@ const (
 	strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters
 )
 
-// Construts an alphanumeric string of given length.
+func init() {
+	// Seed math/rand with "secure" int64
+	b := RandBytes(8)
+	var seed uint64
+	for i := 0; i < 8; i++ {
+		seed |= uint64(b[i])
+		seed <<= 8
+	}
+	rand.Seed(int64(seed))
+}
+
+// Constructs an alphanumeric string of given length.
+// Not crypto safe
 func RandStr(length int) string {
 	chars := []byte{}
 MAIN_LOOP:
@@ -31,3 +45,19 @@ MAIN_LOOP:
 
 	return string(chars)
 }
+
+// Crypto safe
+func RandBytes(numBytes int) []byte {
+	b := make([]byte, numBytes)
+	_, err := crand.Read(b)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+// Crypto safe
+// RandHex(24) gives 96 bits of randomness, strong enough for most purposes.
+func RandHex(numDigits int) string {
+	return hex.EncodeToString(RandBytes(numDigits / 2))
+}
diff --git a/p2p/addrbook.go b/p2p/addrbook.go
index 9e9c845c7..584da1173 100644
--- a/p2p/addrbook.go
+++ b/p2p/addrbook.go
@@ -106,7 +106,7 @@ func NewAddrBook(filePath string) *AddrBook {
 
 // When modifying this, don't forget to update loadFromFile()
 func (a *AddrBook) init() {
-	a.key = RandStr(12)
+	a.key = RandHex(24) // 24/2 * 8 = 96 bits
 	// addr -> ka index
 	a.addrLookup = make(map[string]*knownAddress)
 	// New addr buckets