From d3b78fea959dfb0e1c1f5079ae516303bdb9a0f8 Mon Sep 17 00:00:00 2001 From: Jakob Unterwurzacher Date: Sun, 9 Oct 2016 17:05:12 +0200 Subject: [PATCH] reverse: add panics against API abuse These should help prevent later programming errors. --- internal/cryptocore/cryptocore.go | 4 ++++ internal/fusefrontend_reverse/rfs.go | 8 ++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/internal/cryptocore/cryptocore.go b/internal/cryptocore/cryptocore.go index 7cb5c95..db82f56 100644 --- a/internal/cryptocore/cryptocore.go +++ b/internal/cryptocore/cryptocore.go @@ -72,6 +72,10 @@ func New(key []byte, backend BackendTypeEnum, IVBitLen int) *CryptoCore { case BackendGoGCM: aeadCipher, err = goGCMWrapper(blockCipher, IVLen) case BackendAESSIV: + if IVLen != 16 { + // SIV supports any nonce size, but we only use 16. + panic("AES-SIV must use 16-byte nonces") + } // AES-SIV uses 1/2 of the key for authentication, 1/2 for // encryption, so we need a 64-bytes key for AES-256. Derive it from // the master key by hashing it with SHA-512. diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go index bc8a535..35e9e50 100644 --- a/internal/fusefrontend_reverse/rfs.go +++ b/internal/fusefrontend_reverse/rfs.go @@ -46,10 +46,14 @@ type reverseFS struct { var _ pathfs.FileSystem = &reverseFS{} -// NewFS returns an encrypted FUSE overlay filesystem +// NewFS returns an encrypted FUSE overlay filesystem. +// In this case (reverse mode) the backing directory is plain-text and +// reverseFS provides an encrypted view. func NewFS(args fusefrontend.Args) pathfs.FileSystem { + if args.CryptoBackend != cryptocore.BackendAESSIV { + panic("reverse mode must use AES-SIV, everything else is insecure") + } initLongnameCache() - cryptoCore := cryptocore.New(args.Masterkey, args.CryptoBackend, contentenc.DefaultIVBits) contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS) nameTransform := nametransform.New(cryptoCore, args.LongNames)