Simplify choosing the key description prefix

There's no real need to allow users to choose the key description prefix
(a.k.a. the "service"), since on ext4 and f2fs we can just use "ext4"
and "f2fs" for compatibility with all kernels both old and new, and on
other filesystems we can just use "fscrypt".  So, let's do that.

Since this removes the point of the "--legacy" option to 'fscrypt setup'
and the "compatibility" field in /etc/fscrypt.conf, remove those too.

Specifically, we start ignoring the "compatibility" in existing config
files and not writing it to new ones.  The corresponding protobuf field
number and name are reserved.  We stop accepting the "--legacy" option
at all, although since it was default true and there was no real reason
for anyone to change it to false, probably no one will notice.  If
anyone does, they should just stop specifying the option.

Note that this change only affects user keyrings and thus only affects
v1 encryption policies, which are deprecated in favor of v2 anyway.

1 files changed, 0 insertions, 19 deletions

diff --git a/actions/context.go b/actions/context.go
index f07f225..0db0671 100644
--- a/actions/context.go
+++ b/actions/context.go
@@ -32,8 +32,6 @@ import (
 	"log"
 	"os/user"
 
-	"golang.org/x/sys/unix"
-
 	"github.com/pkg/errors"
 
 	"github.com/google/fscrypt/filesystem"
@@ -133,27 +131,10 @@ func (ctx *Context) checkContext() error {
 	return ctx.Mount.CheckSetup()
 }
 
-// getService returns the keyring service for this context. We use the presence
-// of the LegacyConfig flag to determine if we should use the legacy services.
-// For ext4 systems before v4.8 and f2fs systems before v4.6, filesystem
-// specific services must be used (these legacy services will still work with
-// later kernels).
-func (ctx *Context) getService() string {
-	// For legacy configurations, we may need non-standard services
-	if ctx.Config.HasCompatibilityOption(LegacyConfig) {
-		switch ctx.Mount.FilesystemType {
-		case "ext4", "f2fs":
-			return ctx.Mount.FilesystemType + ":"
-		}
-	}
-	return unix.FSCRYPT_KEY_DESC_PREFIX
-}
-
 func (ctx *Context) getKeyringOptions() *keyring.Options {
 	return &keyring.Options{
 		Mount:                     ctx.Mount,
 		User:                      ctx.TargetUser,
-		Service:                   ctx.getService(),
 		UseFsKeyringForV1Policies: ctx.Config.GetUseFsKeyringForV1Policies(),
 	}
 }