2 files changed, 19 insertions, 9 deletions
diff --git a/internal/contentenc/content.go b/internal/contentenc/content.go
index a2a263c..9998c06 100644
--- a/internal/contentenc/content.go
+++ b/internal/contentenc/content.go
@@ -9,6 +9,7 @@ import (
 	"log"
 
 	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+	"github.com/rfjakob/gocryptfs/internal/stupidgcm"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
@@ -46,10 +47,12 @@ type ContentEnc struct {
 	allZeroBlock []byte
 	// All-zero block of size IVBitLen/8, for fast compares
 	allZeroNonce []byte
+	// Force decode even if integrity check fails (openSSL only)
+	forceDecode bool
 }
 
 // New returns an initialized ContentEnc instance.
-func New(cc *cryptocore.CryptoCore, plainBS uint64) *ContentEnc {
+func New(cc *cryptocore.CryptoCore, plainBS uint64, forceDecode bool) *ContentEnc {
 	cipherBS := plainBS + uint64(cc.IVLen) + cryptocore.AuthTagLen
 
 	return &ContentEnc{
@@ -58,6 +61,7 @@ func New(cc *cryptocore.CryptoCore, plainBS uint64) *ContentEnc {
 		cipherBS:     cipherBS,
 		allZeroBlock: make([]byte, cipherBS),
 		allZeroNonce: make([]byte, cc.IVLen),
+		forceDecode:  forceDecode,
 	}
 }
 
@@ -82,7 +86,9 @@ func (be *ContentEnc) DecryptBlocks(ciphertext []byte, firstBlockNo uint64, file
 		var pBlock []byte
 		pBlock, err = be.DecryptBlock(cBlock, firstBlockNo, fileID)
 		if err != nil {
-			break
+			if be.forceDecode == false || (be.forceDecode == true && stupidgcm.AuthError != err) {
+				break
+			}
 		}
 		pBuf.Write(pBlock)
 		firstBlockNo++
@@ -133,7 +139,11 @@ func (be *ContentEnc) DecryptBlock(ciphertext []byte, blockNo uint64, fileID []b
 	if err != nil {
 		tlog.Warn.Printf("DecryptBlock: %s, len=%d", err.Error(), len(ciphertextOrig))
 		tlog.Debug.Println(hex.Dump(ciphertextOrig))
-		return nil, err
+		if be.forceDecode == true {
+			return plaintext, err
+		} else {
+			return nil, err
+		}
 	}
 
 	return plaintext, nil
diff --git a/internal/contentenc/content_test.go b/internal/contentenc/content_test.go
index 8ce496d..e4d4a3e 100644
--- a/internal/contentenc/content_test.go
+++ b/internal/contentenc/content_test.go
@@ -23,8 +23,8 @@ func TestSplitRange(t *testing.T) {
 		testRange{6654, 8945})
 
 	key := make([]byte, cryptocore.KeyLen)
-	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true)
-	f := New(cc, DefaultBS)
+	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true, false)
+	f := New(cc, DefaultBS, false)
 
 	for _, r := range ranges {
 		parts := f.ExplodePlainRange(r.offset, r.length)
@@ -51,8 +51,8 @@ func TestCiphertextRange(t *testing.T) {
 		testRange{6654, 8945})
 
 	key := make([]byte, cryptocore.KeyLen)
-	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true)
-	f := New(cc, DefaultBS)
+	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true, false)
+	f := New(cc, DefaultBS, false)
 
 	for _, r := range ranges {
 
@@ -74,8 +74,8 @@ func TestCiphertextRange(t *testing.T) {
 
 func TestBlockNo(t *testing.T) {
 	key := make([]byte, cryptocore.KeyLen)
-	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true)
-	f := New(cc, DefaultBS)
+	cc := cryptocore.New(key, cryptocore.BackendOpenSSL, DefaultIVBits, true, false)
+	f := New(cc, DefaultBS, false)
 
 	b := f.CipherOffToBlockNo(788)
 	if b != 0 {