Merge pull request #4812 from hashicorp/checksumfix

post-processor/checksum: fix crash when invalid checksum is used

post-processor/checksum/post-processor.go

@@ -30,6 +30,31 @@ type PostProcessor struct {
 	config Config
 }
 
+type outputPathTemplate struct {
+	BuildName    string
+	BuilderType  string
+	ChecksumType string
+}
+
+func getHash(t string) hash.Hash {
+	var h hash.Hash
+	switch t {
+	case "md5":
+		h = md5.New()
+	case "sha1":
+		h = sha1.New()
+	case "sha224":
+		h = sha256.New224()
+	case "sha256":
+		h = sha256.New()
+	case "sha384":
+		h = sha512.New384()
+	case "sha512":
+		h = sha512.New()
+	}
+	return h
+}
+
 func (p *PostProcessor) Configure(raws ...interface{}) error {
 	err := config.Decode(&p.config, &config.DecodeOpts{
 		Interpolate: true,
@@ -40,16 +65,22 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 	if err != nil {
 		return err
 	}
+	errs := new(packer.MultiError)
 
 	if p.config.ChecksumTypes == nil {
 		p.config.ChecksumTypes = []string{"md5"}
 	}
 
-	if p.config.OutputPath == "" {
-		p.config.OutputPath = "packer_{{.BuildName}}_{{.BuilderType}}" + ".checksum"
+	for _, k := range p.config.ChecksumTypes {
+		if h := getHash(k); h == nil {
+			errs = packer.MultiErrorAppend(errs,
+				fmt.Errorf("Unrecognized checksum type: %s", k))
+		}
 	}
 
-	errs := new(packer.MultiError)
+	if p.config.OutputPath == "" {
+		p.config.OutputPath = "packer_{{.BuildName}}_{{.BuilderType}}_{{.ChecksumType}}.checksum"
+	}
 
 	if err = interpolate.Validate(p.config.OutputPath, &p.config.ctx); err != nil {
 		errs = packer.MultiErrorAppend(
@@ -63,37 +94,26 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 	return nil
 }
 
-func getHash(t string) hash.Hash {
-	var h hash.Hash
-	switch t {
-	case "md5":
-		h = md5.New()
-	case "sha1":
-		h = sha1.New()
-	case "sha224":
-		h = sha256.New224()
-	case "sha256":
-		h = sha256.New()
-	case "sha384":
-		h = sha512.New384()
-	case "sha512":
-		h = sha512.New()
-	}
-	return h
-}
-
 func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, error) {
 	files := artifact.Files()
 	var h hash.Hash
-	var checksumFile string
 
 	newartifact := NewArtifact(artifact.Files())
+	opTpl := &outputPathTemplate{
+		BuildName:   p.config.PackerBuildName,
+		BuilderType: p.config.PackerBuilderType,
+	}
 
 	for _, ct := range p.config.ChecksumTypes {
 		h = getHash(ct)
+		opTpl.ChecksumType = ct
+		p.config.ctx.Data = &opTpl
 
 		for _, art := range files {
-			checksumFile = p.config.OutputPath
+			checksumFile, err := interpolate.Render(p.config.OutputPath, &p.config.ctx)
+			if err != nil {
+				return nil, false, err
+			}
 
 			if _, err := os.Stat(checksumFile); err != nil {
 				newartifact.files = append(newartifact.files, checksumFile)

website/source/docs/post-processors/checksum.html.md

@@ -44,4 +44,13 @@ Optional parameters:
 
 - `checksum_types` (array of strings) - An array of strings of checksum types
 to compute. Allowed values are md5, sha1, sha224, sha256, sha384, sha512.
-- `output` (string) - Specify filename to store checksums.
+- `output` (string) - Specify filename to store checksums. This defaults to
+    `packer_{{.BuildName}}_{{.BuilderType}}_{{.ChecksumType}}.checksum`. For
+    example, if you had a builder named `database`, you might see the file
+    written as `packer_database_docker_md5.checksum`. The following variables are
+    available to use in the output template:
+
+    * `BuildName`: The name of the builder that produced the artifact.
+    * `BuilderType`: The type of builder used to produce the artifact.
+    * `ChecksumType`: The type of checksums the file contains. This should be
+        used if you have more than one value in `checksum_types`.