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-rw-r--r--internal/pathiv/pathiv.go26
1 files changed, 23 insertions, 3 deletions
diff --git a/internal/pathiv/pathiv.go b/internal/pathiv/pathiv.go
index d2d90a2..aa11b75 100644
--- a/internal/pathiv/pathiv.go
+++ b/internal/pathiv/pathiv.go
@@ -6,13 +6,19 @@ import (
"github.com/rfjakob/gocryptfs/internal/nametransform"
)
+// Purpose identifies for which purpose the IV will be used. This is mixed into the
+// derivation.
type Purpose string
const (
- PurposeDirIV Purpose = "DIRIV"
- PurposeFileID Purpose = "FILEID"
+ // PurposeDirIV means the value will be used as a directory IV
+ PurposeDirIV Purpose = "DIRIV"
+ // PurposeFileID means the value will be used as the file ID in the file header
+ PurposeFileID Purpose = "FILEID"
+ // PurposeSymlinkIV means the value will be used as the IV for symlink encryption
PurposeSymlinkIV Purpose = "SYMLINKIV"
- PurposeBlock0IV Purpose = "BLOCK0IV"
+ // PurposeBlock0IV means the value will be used as the IV of ciphertext block #0.
+ PurposeBlock0IV Purpose = "BLOCK0IV"
)
// Derive derives an IV from an encrypted path by hashing it with sha256
@@ -22,3 +28,17 @@ func Derive(path string, purpose Purpose) []byte {
hash := sha256.Sum256(extended)
return hash[:nametransform.DirIVLen]
}
+
+// FileIVs contains both IVs that are needed to create a file.
+type FileIVs struct {
+ ID []byte
+ Block0IV []byte
+}
+
+// DeriveFile derives both IVs that are needed to create a file and returns them
+// in a container struct.
+func DeriveFile(path string) (fileIVs FileIVs) {
+ fileIVs.ID = Derive(path, PurposeFileID)
+ fileIVs.Block0IV = Derive(path, PurposeBlock0IV)
+ return fileIVs
+}