3 files changed, 36 insertions, 1 deletions
diff --git a/cryptfs/cryptfs.go b/cryptfs/cryptfs.go
index 71ec996..46f5b65 100644
--- a/cryptfs/cryptfs.go
+++ b/cryptfs/cryptfs.go
@@ -58,6 +58,12 @@ func NewCryptFS(key []byte, useOpenssl bool) *CryptFS {
 	}
 }
 
+// Get plaintext block size
 func (be *CryptFS) PlainBS() uint64 {
 	return be.plainBS
 }
+
+// Get ciphertext block size
+func (be *CryptFS) CipherBS() uint64 {
+	return be.cipherBS
+}
diff --git a/cryptfs/cryptfs_content.go b/cryptfs/cryptfs_content.go
index e42011a..a4dc78a 100644
--- a/cryptfs/cryptfs_content.go
+++ b/cryptfs/cryptfs_content.go
@@ -7,8 +7,22 @@ import (
 	"os"
 	"errors"
 	"crypto/cipher"
+	"crypto/md5"
+	"encoding/hex"
 )
 
+const (
+	// A block of 4124 zero bytes has this md5
+	ZeroBlockMd5 = "64331af89bd15a987b39855338336237"
+)
+
+// md5sum - debug helper, return md5 hex string
+func md5sum(buf []byte) string {
+	rawHash := md5.Sum(buf)
+	hash := hex.EncodeToString(rawHash[:])
+	return hash
+}
+
 type CryptFile struct {
 	file *os.File
 	gcm cipher.AEAD
@@ -55,6 +69,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
 
 	// Extract nonce
 	nonce := ciphertext[:NONCE_LEN]
+	ciphertextOrig := ciphertext
 	ciphertext = ciphertext[NONCE_LEN:]
 
 	// Decrypt
@@ -63,7 +78,7 @@ func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
 	plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
 
 	if err != nil {
-		Warn.Printf("DecryptBlock: %s\n", err.Error())
+		Warn.Printf("DecryptBlock: %s, len=%d, md5=%s\n", err.Error(), len(ciphertextOrig), Warn.Md5sum(ciphertextOrig))
 		return nil, err
 	}
 
diff --git a/cryptfs/log.go b/cryptfs/log.go
index d40aa3f..850ec9e 100644
--- a/cryptfs/log.go
+++ b/cryptfs/log.go
@@ -15,6 +15,12 @@ func (l *logChannel) Printf(format string, args ...interface{}) {
 	}
 }
 
+func (l *logChannel) Println(s string) {
+	if l.enabled == true {
+		fmt.Println(s)
+	}
+}
+
 func (l *logChannel) Dump(d []byte) {
 	s := string(d)
 	fmt.Println(strings.Replace(s, "\000", "\\0", -1))
@@ -24,6 +30,14 @@ func (l *logChannel) Enable() {
 	l.enabled = true
 }
 
+// Only actually calculate the md5sum if the log channel is enabled to save
+// CPU cycles
+func (l *logChannel) Md5sum(buf []byte) string {
+	if l.enabled == false {
+		return ""
+	}
+	return md5sum(buf)
+}
 
 var Debug = logChannel{false}
 var Notice = logChannel{true}