provider/azurerm: Auto base64encode virtual_machine custom data

Reported by @sethvargo - we auto encode for AWS, we should follow a
similar pattern for Azure.

In order to escape the double encoding, we check that it's not already
encoded before encoding

builtin/providers/azurerm/resource_arm_virtual_machine.go

@@ -2,6 +2,7 @@ package azurerm
 
 import (
 	"bytes"
+	"encoding/base64"
 	"fmt"
 	"log"
 	"net/http"
@@ -886,7 +887,14 @@ func flattenAzureRmVirtualMachineOsProfile(osProfile *compute.OSProfile) []inter
 	result["computer_name"] = *osProfile.ComputerName
 	result["admin_username"] = *osProfile.AdminUsername
 	if osProfile.CustomData != nil {
-		result["custom_data"] = *osProfile.CustomData
+		var data string
+		if isBase64Encoded(*osProfile.CustomData) {
+			decodedData, _ := base64.StdEncoding.DecodeString(*osProfile.CustomData)
+			data = string(decodedData)
+		} else {
+			data = *osProfile.CustomData
+		}
+		result["custom_data"] = data
 	}
 
 	return []interface{}{result}
@@ -1039,6 +1047,12 @@ func expandAzureRmVirtualMachineOsProfile(d *schema.ResourceData) (*compute.OSPr
 	}
 
 	if v := osProfile["custom_data"].(string); v != "" {
+		if isBase64Encoded(v) {
+			log.Printf("[WARN] Future Versions of Terraform will automatically base64encode custom_data")
+		} else {
+			v = base64Encode(v)
+		}
+
 		profile.CustomData = &v
 	}
 

builtin/providers/azurerm/resource_arm_virtual_machine_scale_set.go

@@ -2,6 +2,7 @@ package azurerm
 
 import (
 	"bytes"
+	"encoding/base64"
 	"fmt"
 	"log"
 	"net/http"
@@ -651,7 +652,14 @@ func flattenAzureRMVirtualMachineScaleSetOsProfile(profile *compute.VirtualMachi
 	result["admin_username"] = *profile.AdminUsername
 
 	if profile.CustomData != nil {
-		result["custom_data"] = *profile.CustomData
+		var data string
+		if isBase64Encoded(*profile.CustomData) {
+			decodedData, _ := base64.StdEncoding.DecodeString(*profile.CustomData)
+			data = string(decodedData)
+		} else {
+			data = *profile.CustomData
+		}
+		result["custom_data"] = data
 	}
 
 	return []interface{}{result}
@@ -853,6 +861,15 @@ func expandAzureRmVirtualMachineScaleSetNetworkProfile(d *schema.ResourceData) *
 	}
 }
 
+func base64Encode(data string) string {
+	return base64.StdEncoding.EncodeToString([]byte(data))
+}
+
+func isBase64Encoded(data string) bool {
+	_, err := base64.StdEncoding.DecodeString(data)
+	return err == nil
+}
+
 func expandAzureRMVirtualMachineScaleSetsOsProfile(d *schema.ResourceData) (*compute.VirtualMachineScaleSetOSProfile, error) {
 	osProfileConfigs := d.Get("os_profile").(*schema.Set).List()
 
@@ -872,6 +889,11 @@ func expandAzureRMVirtualMachineScaleSetsOsProfile(d *schema.ResourceData) (*com
 	}
 
 	if customData != "" {
+		if isBase64Encoded(customData) {
+			log.Printf("[WARN] Future Versions of Terraform will automatically base64encode custom_data")
+		} else {
+			customData = base64Encode(customData)
+		}
 		osProfile.CustomData = &customData
 	}
 

website/source/docs/providers/azurerm/r/virtual_machine.html.markdown

@@ -266,7 +266,7 @@ For more information on the different example configurations, please check out t
 * `computer_name` - (Required) Specifies the name of the virtual machine.
 * `admin_username` - (Required) Specifies the name of the administrator account.
 * `admin_password` - (Required) Specifies the password of the administrator account.
-* `custom_data` - (Optional) Specifies a base-64 encoded string of custom data. The base-64 encoded string is decoded to a binary array that is saved as a file on the Virtual Machine. The maximum length of the binary array is 65535 bytes.
+* `custom_data` - (Optional) Specifies custom data to supply to the machine. On linux-based systems, this can be used as a cloud-init script. On other systems, this will be copied as a file on disk. Internally, Terraform will base64 encode this value before sending it to the API. The maximum length of the binary array is 65535 bytes.
 
 ~> **NOTE:** `admin_password` must be between 6-72 characters long and must satisfy at least 3 of password complexity requirements from the following:
 1. Contains an uppercase character

website/source/docs/providers/azurerm/r/virtual_machine_scale_sets.html.markdown

@@ -136,7 +136,7 @@ The following arguments are supported:
 * `computer_name_prefix` - (Required) Specifies the computer name prefix for all of the virtual machines in the scale set. Computer name prefixes must be 1 to 15 characters long.
 * `admin_username` - (Required) Specifies the administrator account name to use for all the instances of virtual machines in the scale set.
 * `admin_password` - (Required) Specifies the administrator password to use for all the instances of virtual machines in a scale set..
-* `custom_data` - (Optional) Specifies a base-64 encoded string of custom data. The base-64 encoded string is decoded to a binary array that is saved as a file on all the Virtual Machines in the scale set. The maximum length of the binary array is 65535 bytes.
+* `custom_data` - (Optional) Specifies custom data to supply to the machine. On linux-based systems, this can be used as a cloud-init script. On other systems, this will be copied as a file on disk. Internally, Terraform will base64 encode this value before sending it to the API. The maximum length of the binary array is 65535 bytes.
 
 `os_profile_secrets` supports the following: