From 113dc1234617d748152fe039c24511de3cf3e2fc Mon Sep 17 00:00:00 2001
From: Paul Meyer <paulmey@microsoft.com>
Date: Wed, 25 Sep 2019 21:15:25 +0000
Subject: [PATCH] Add function to detect whether Packer is running on Azure

---
 builder/azure/common/detect_azure.go          |  8 +++++
 builder/azure/common/detect_azure_linux.go    | 23 +++++++++++++++
 .../azure/common/detect_azure_linux_test.go   | 29 +++++++++++++++++++
 3 files changed, 60 insertions(+)
 create mode 100644 builder/azure/common/detect_azure.go
 create mode 100644 builder/azure/common/detect_azure_linux.go
 create mode 100644 builder/azure/common/detect_azure_linux_test.go

diff --git a/builder/azure/common/detect_azure.go b/builder/azure/common/detect_azure.go
new file mode 100644
index 000000000..001ca1b4f
--- /dev/null
+++ b/builder/azure/common/detect_azure.go
@@ -0,0 +1,8 @@
+// +build !linux
+
+package common
+
+// IsAzure returns true if Packer is running on Azure (currently only works on Linux)
+func IsAzure() bool {
+	return false
+}
diff --git a/builder/azure/common/detect_azure_linux.go b/builder/azure/common/detect_azure_linux.go
new file mode 100644
index 000000000..f57eb42b9
--- /dev/null
+++ b/builder/azure/common/detect_azure_linux.go
@@ -0,0 +1,23 @@
+package common
+
+import (
+	"bytes"
+	"io/ioutil"
+)
+
+var (
+	smbiosAssetTagFile = "/sys/class/dmi/id/chassis_asset_tag"
+	azureAssetTag      = []byte("7783-7084-3265-9085-8269-3286-77\n")
+)
+
+// IsAzure returns true if Packer is running on Azure
+func IsAzure() bool {
+	return isAzureAssetTag(smbiosAssetTagFile)
+}
+
+func isAzureAssetTag(filename string) bool {
+	if d, err := ioutil.ReadFile(filename); err == nil {
+		return bytes.Compare(d, azureAssetTag) == 0
+	}
+	return false
+}
diff --git a/builder/azure/common/detect_azure_linux_test.go b/builder/azure/common/detect_azure_linux_test.go
new file mode 100644
index 000000000..9d755cfd9
--- /dev/null
+++ b/builder/azure/common/detect_azure_linux_test.go
@@ -0,0 +1,29 @@
+package common
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsAzure(t *testing.T) {
+	f, err := ioutil.TempFile("", "TestIsAzure*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(f.Name())
+
+	f.Seek(0, 0)
+	f.Truncate(0)
+	f.Write([]byte("not the azure assettag"))
+
+	assert.False(t, isAzureAssetTag(f.Name()), "asset tag is not Azure's")
+
+	f.Seek(0, 0)
+	f.Truncate(0)
+	f.Write(azureAssetTag)
+
+	assert.True(t, isAzureAssetTag(f.Name()), "asset tag is Azure's")
+}