From 0904b472184cd9a1f31fc436a5bc97fec96f934f Mon Sep 17 00:00:00 2001
From: Ian Kaneshiro <iankane@umich.edu>
Date: Fri, 16 Aug 2019 16:36:02 -0400
Subject: [PATCH] Extend helpers and siftool for CryptoMessage type

This adds helpers to deserialize the data stored within the Extra field.
And updates siftool to give useful information about this new type.

Signed-off-by: Ian Kaneshiro <iankane@umich.edu>
---
 internal/app/siftool/modif.go |  2 ++
 pkg/sif/fmt.go                | 33 +++++++++++++++++++++++++++++++++
 pkg/sif/lookup.go             | 30 ++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/internal/app/siftool/modif.go b/internal/app/siftool/modif.go
index 04009957..3070e127 100644
--- a/internal/app/siftool/modif.go
+++ b/internal/app/siftool/modif.go
@@ -69,6 +69,8 @@ func Add(containerFile, dataFile string, opts AddOptions) error {
 		d = sif.DataGenericJSON
 	case 7:
 		d = sif.DataGeneric
+	case 8:
+		d = sif.DataCryptoMessage
 	default:
 		log.Printf("error: -datatype flag is required with a valid range\n\n")
 		return fmt.Errorf("usage")
diff --git a/pkg/sif/fmt.go b/pkg/sif/fmt.go
index b416a555..b5659f89 100644
--- a/pkg/sif/fmt.go
+++ b/pkg/sif/fmt.go
@@ -74,6 +74,8 @@ func datatypeStr(dtype Datatype) string {
 		return "JSON.Generic"
 	case DataGeneric:
 		return "Generic/Raw"
+	case DataCryptoMessage:
+		return "Cryptographic Message"
 	}
 	return "Unknown data-type"
 }
@@ -127,6 +129,28 @@ func hashtypeStr(htype Hashtype) string {
 	return "Unknown hash-type"
 }
 
+// formattypeStr returns a string representation of a format type
+func formattypeStr(ftype Formattype) string {
+	switch ftype {
+	case FormatOpenPGP:
+		return "OpenPGP"
+	case FormatPEM:
+		return "PEM"
+	}
+	return "Unknown format-type"
+}
+
+// messagetypeStr returns a string representation of a message type
+func messagetypeStr(mtype Messagetype) string {
+	switch mtype {
+	case MessageClearSignature:
+		return "Clear Signature"
+	case MessageRSAOAEP:
+		return "RSA-OAEP"
+	}
+	return "Unknown message-type"
+}
+
 // FmtDescrList formats the output of a list of all active descriptors from a SIF file
 func (fimg *FileImage) FmtDescrList() string {
 	s := fmt.Sprintf("%-4s %-8s %-8s %-26s %s\n", "ID", "|GROUP", "|LINK", "|SIF POSITION (start-end)", "|TYPE")
@@ -164,6 +188,10 @@ func (fimg *FileImage) FmtDescrList() string {
 			case DataSignature:
 				h, _ := v.GetHashType()
 				s += fmt.Sprintf("|%s (%s)\n", datatypeStr(v.Datatype), hashtypeStr(h))
+			case DataCryptoMessage:
+				f, _ := v.GetFormatType()
+				m, _ := v.GetMessageType()
+				s += fmt.Sprintf("|%s (%s/%s)\n", datatypeStr(v.Datatype), formattypeStr(f), messagetypeStr(m))
 			default:
 				s += fmt.Sprintf("|%s\n", datatypeStr(v.Datatype))
 			}
@@ -219,6 +247,11 @@ func (fimg *FileImage) FmtDescrInfo(id uint32) string {
 				e, _ := v.GetEntityString()
 				s += fmt.Sprintln("  Hashtype: ", hashtypeStr(h))
 				s += fmt.Sprintln("  Entity:   ", e)
+			case DataCryptoMessage:
+				f, _ := v.GetFormatType()
+				m, _ := v.GetMessageType()
+				s += fmt.Sprintln("  Fmttype:  ", formattypeStr(f))
+				s += fmt.Sprintln("  Msgtype:  ", messagetypeStr(m))
 			}
 
 			return s
diff --git a/pkg/sif/lookup.go b/pkg/sif/lookup.go
index 40695308..c9fca8ad 100644
--- a/pkg/sif/lookup.go
+++ b/pkg/sif/lookup.go
@@ -375,6 +375,36 @@ func (descr *Descriptor) GetEntityString() (string, error) {
 	return fmt.Sprintf("%0X", fingerprint[:20]), nil
 }
 
+// GetFormatType extracts the Formattype field from the Extra field of a Cryptographic Message Descriptor
+func (descr *Descriptor) GetFormatType() (Formattype, error) {
+	if descr.Datatype != DataCryptoMessage {
+		return -1, fmt.Errorf("expected DataCryptoMessage, got %v", descr.Datatype)
+	}
+
+	var cinfo CryptoMessage
+	b := bytes.NewReader(descr.Extra[:])
+	if err := binary.Read(b, binary.LittleEndian, &cinfo); err != nil {
+		return -1, fmt.Errorf("while extracting Crypto extra info: %s", err)
+	}
+
+	return cinfo.Formattype, nil
+}
+
+// GetMessageType extracts the Messagetype field from the Extra field of a Cryptographic Message Descriptor
+func (descr *Descriptor) GetMessageType() (Messagetype, error) {
+	if descr.Datatype != DataCryptoMessage {
+		return -1, fmt.Errorf("expected DataCryptoMessage, got %v", descr.Datatype)
+	}
+
+	var cinfo CryptoMessage
+	b := bytes.NewReader(descr.Extra[:])
+	if err := binary.Read(b, binary.LittleEndian, &cinfo); err != nil {
+		return -1, fmt.Errorf("while extracting Crypto extra info: %s", err)
+	}
+
+	return cinfo.Messagetype, nil
+}
+
 // GetPartPrimSys returns the primary system partition if present. There should
 // be only one primary system partition in a SIF file.
 func (fimg *FileImage) GetPartPrimSys() (*Descriptor, int, error) {