Major refactoring: Split up "cryptfs" into several internal packages

"git status" for reference:

deleted:    cryptfs/cryptfs.go
deleted:    cryptfs/names_core.go
modified:   integration_tests/cli_test.go
modified:   integration_tests/helpers.go
renamed:    cryptfs/config_file.go -> internal/configfile/config_file.go
renamed:    cryptfs/config_test.go -> internal/configfile/config_test.go
renamed:    cryptfs/config_test/.gitignore -> internal/configfile/config_test/.gitignore
renamed:    cryptfs/config_test/PlaintextNames.conf -> internal/configfile/config_test/PlaintextNames.conf
renamed:    cryptfs/config_test/StrangeFeature.conf -> internal/configfile/config_test/StrangeFeature.conf
renamed:    cryptfs/config_test/v1.conf -> internal/configfile/config_test/v1.conf
renamed:    cryptfs/config_test/v2.conf -> internal/configfile/config_test/v2.conf
renamed:    cryptfs/kdf.go -> internal/configfile/kdf.go
renamed:    cryptfs/kdf_test.go -> internal/configfile/kdf_test.go
renamed:    cryptfs/cryptfs_content.go -> internal/contentenc/content.go
new file:   internal/contentenc/content_api.go
renamed:    cryptfs/content_test.go -> internal/contentenc/content_test.go
renamed:    cryptfs/file_header.go -> internal/contentenc/file_header.go
renamed:    cryptfs/intrablock.go -> internal/contentenc/intrablock.go
renamed:    cryptfs/address_translation.go -> internal/contentenc/offsets.go
new file:   internal/cryptocore/crypto_api.go
renamed:    cryptfs/gcm_go1.4.go -> internal/cryptocore/gcm_go1.4.go
renamed:    cryptfs/gcm_go1.5.go -> internal/cryptocore/gcm_go1.5.go
renamed:    cryptfs/nonce.go -> internal/cryptocore/nonce.go
renamed:    cryptfs/openssl_aead.go -> internal/cryptocore/openssl_aead.go
renamed:    cryptfs/openssl_benchmark.bash -> internal/cryptocore/openssl_benchmark.bash
renamed:    cryptfs/openssl_test.go -> internal/cryptocore/openssl_test.go
new file:   internal/nametransform/name_api.go
new file:   internal/nametransform/names_core.go
renamed:    cryptfs/names_diriv.go -> internal/nametransform/names_diriv.go
renamed:    cryptfs/names_noiv.go -> internal/nametransform/names_noiv.go
renamed:    cryptfs/names_test.go -> internal/nametransform/names_test.go
new file:   internal/nametransform/pad16.go
renamed:    cryptfs/log.go -> internal/toggledlog/log.go
renamed:    cryptfs/log_go1.4.go -> internal/toggledlog/log_go1.4.go
renamed:    cryptfs/log_go1.5.go -> internal/toggledlog/log_go1.5.go
modified:   main.go
modified:   masterkey.go
modified:   pathfs_frontend/file.go
modified:   pathfs_frontend/file_holes.go
modified:   pathfs_frontend/fs.go
modified:   pathfs_frontend/fs_dir.go
modified:   pathfs_frontend/names.go
modified:   test.bash

1 files changed, 60 insertions, 0 deletions

diff --git a/internal/nametransform/pad16.go b/internal/nametransform/pad16.go
new file mode 100644
index 0000000..c15160e
--- /dev/null
+++ b/internal/nametransform/pad16.go
@@ -0,0 +1,60 @@
+package nametransform
+
+import (
+	"fmt"
+	"crypto/aes"
+	"errors"
+)
+
+// pad16 - pad data to AES block size (=16 byte) using standard PKCS#7 padding
+// https://tools.ietf.org/html/rfc5652#section-6.3
+func pad16(orig []byte) (padded []byte) {
+	oldLen := len(orig)
+	if oldLen == 0 {
+		panic("Padding zero-length string makes no sense")
+	}
+	padLen := aes.BlockSize - oldLen%aes.BlockSize
+	if padLen == 0 {
+		padLen = aes.BlockSize
+	}
+	newLen := oldLen + padLen
+	padded = make([]byte, newLen)
+	copy(padded, orig)
+	padByte := byte(padLen)
+	for i := oldLen; i < newLen; i++ {
+		padded[i] = padByte
+	}
+	return padded
+}
+
+// unPad16 - remove padding
+func unPad16(padded []byte) ([]byte, error) {
+	oldLen := len(padded)
+	if oldLen%aes.BlockSize != 0 {
+		return nil, errors.New("Unaligned size")
+	}
+	// The last byte is always a padding byte
+	padByte := padded[oldLen-1]
+	// The padding byte's value is the padding length
+	padLen := int(padByte)
+	// Padding must be at least 1 byte
+	if padLen <= 0 {
+		return nil, errors.New("Padding cannot be zero-length")
+	}
+	// Larger paddings make no sense
+	if padLen > aes.BlockSize {
+		return nil, fmt.Errorf("Padding too long, padLen = %d > 16", padLen)
+	}
+	// All padding bytes must be identical
+	for i := oldLen - padLen; i < oldLen; i++ {
+		if padded[i] != padByte {
+			return nil, fmt.Errorf("Padding byte at i=%d is invalid", i)
+		}
+	}
+	newLen := oldLen - padLen
+	// Padding an empty string makes no sense
+	if newLen == 0 {
+		return nil, errors.New("Unpadded length is zero")
+	}
+	return padded[0:newLen], nil
+}