From b5c7521f52b72493eceeb3b3be2024c559b74511 Mon Sep 17 00:00:00 2001
From: Chris Marchesi <cmarchesi@paybyphone.com>
Date: Wed, 9 Dec 2015 17:42:12 -0800
Subject: [PATCH] aws_lambda_function: Force code update on SHA sum mismatch

---
 .../aws/resource_aws_lambda_function.go       | 43 ++++++++++++++++++-
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/builtin/providers/aws/resource_aws_lambda_function.go b/builtin/providers/aws/resource_aws_lambda_function.go
index 8da45720e..178b0d88f 100644
--- a/builtin/providers/aws/resource_aws_lambda_function.go
+++ b/builtin/providers/aws/resource_aws_lambda_function.go
@@ -2,6 +2,7 @@ package aws
 
 import (
 	"crypto/sha256"
+	"encoding/base64"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -102,6 +103,11 @@ func resourceAwsLambdaFunction() *schema.Resource {
 					},
 				},
 			},
+			"update_code": &schema.Schema{
+				Type:     schema.TypeBool,
+				Optional: true,
+				Default:  false,
+			},
 			"arn": &schema.Schema{
 				Type:     schema.TypeString,
 				Computed: true,
@@ -113,7 +119,10 @@ func resourceAwsLambdaFunction() *schema.Resource {
 			"source_code_hash": &schema.Schema{
 				Type:     schema.TypeString,
 				Computed: true,
-				ForceNew: true,
+			},
+			"remote_code_hash": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
 			},
 		},
 	}
@@ -249,6 +258,26 @@ func resourceAwsLambdaFunctionRead(d *schema.ResourceData, meta interface{}) err
 		d.Set("vpc_config", config)
 	}
 
+	// Compare code hashes, and see if an update is required to code. If there
+	// is, set the "update_code" attribute.
+
+	remoteSum, err := decodeBase64(*function.CodeSha256)
+	if err != nil {
+		return err
+	}
+	_, localSum, err := loadLocalZipFile(d.Get("filename").(string))
+	if err != nil {
+		return err
+	}
+	d.Set("remote_code_hash", remoteSum)
+	d.Set("source_code_hash", localSum)
+
+	if remoteSum != localSum {
+		d.Set("update_code", true)
+	} else {
+		d.Set("update_code", false)
+	}
+
 	return nil
 }
 
@@ -361,6 +390,7 @@ func resourceAwsLambdaFunctionUpdate(d *schema.ResourceData, meta interface{}) e
 	return resourceAwsLambdaFunctionRead(d, meta)
 }
 
+// loads the local ZIP data and the SHA sum of the data.
 func loadLocalZipFile(v string) ([]byte, string, error) {
 	filename, err := homedir.Expand(v)
 	if err != nil {
@@ -371,7 +401,16 @@ func loadLocalZipFile(v string) ([]byte, string, error) {
 		return nil, "", err
 	}
 	sum := sha256.Sum256(zipfile)
-	return zipfile, string(sum[:32]), nil
+	return zipfile, fmt.Sprintf("%x", sum), nil
+}
+
+// Decodes a base64 string to a string.
+func decodeBase64(s string) (string, error) {
+	sum, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%x", sum), nil
 }
 
 func validateVPCConfig(v interface{}) (map[string]interface{}, error) {