From e65e2d104afa8ed5e1846579c9bede7676d5518b Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 8 Jun 2015 20:41:39 -0700
Subject: [PATCH 1/2] common: StepDownload can force an extension

---
 common/step_download.go | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/common/step_download.go b/common/step_download.go
index 8d6378adc..b8bd60b5e 100644
--- a/common/step_download.go
+++ b/common/step_download.go
@@ -1,6 +1,7 @@
 package common
 
 import (
+	"crypto/sha1"
 	"encoding/hex"
 	"fmt"
 	"log"
@@ -36,6 +37,12 @@ type StepDownload struct {
 
 	// A list of URLs to attempt to download this thing.
 	Url []string
+
+	// Extension is the extension to force for the file that is downloaded.
+	// Some systems require a certain extension. If this isn't set, the
+	// extension on the URL is used. Otherwise, this will be forced
+	// on the downloaded file for every URL.
+	Extension string
 }
 
 func (s *StepDownload) Run(state multistep.StateBag) multistep.StepAction {
@@ -60,9 +67,19 @@ func (s *StepDownload) Run(state multistep.StateBag) multistep.StepAction {
 
 		targetPath := s.TargetPath
 		if targetPath == "" {
+			// Determine a cache key. This is normally just the URL but
+			// if we force a certain extension we hash the URL and add
+			// the extension to force it.
+			cacheKey := url
+			if s.Extension != "" {
+				hash := sha1.Sum([]byte(url))
+				cacheKey = fmt.Sprintf(
+					"%s.%s", hex.EncodeToString(hash[:]), s.Extension)
+			}
+
 			log.Printf("Acquiring lock to download: %s", url)
-			targetPath = cache.Lock(url)
-			defer cache.Unlock(url)
+			targetPath = cache.Lock(cacheKey)
+			defer cache.Unlock(cacheKey)
 		}
 
 		config := &DownloadConfig{

From 9ea34d4ea85d469272a12dc0ab6fe6837128e382 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 8 Jun 2015 20:42:16 -0700
Subject: [PATCH 2/2] virtualbox/iso: force iso extension for downloads

---
 builder/virtualbox/iso/builder.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/builder/virtualbox/iso/builder.go b/builder/virtualbox/iso/builder.go
index d095eae2d..b6ca982fd 100644
--- a/builder/virtualbox/iso/builder.go
+++ b/builder/virtualbox/iso/builder.go
@@ -230,6 +230,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			Description:  "ISO",
 			ResultKey:    "iso_path",
 			Url:          b.config.ISOUrls,
+			Extension:    "iso",
 		},
 		&vboxcommon.StepOutputDir{
 			Force: b.config.PackerForce,