Ran the following commands, using Go 1.23.12:

    go get google.golang.org/protobuf
    go mod tidy
    make gen

Since opening an encrypted regular file that is locked fails with
ENOKEY, getting the encryption policy of such a file is not possible.
As a result, 'fscrypt status' and 'fscrypt lock' fail on such files.
Provide a better error message that tries to explain what is going on.

Resolves https://github.com/google/fscrypt/issues/393

Signed-off-by: Joe Richey <joerichey@google.com>
[ebiggers: moved the new checks from PassphraseHash to CheckValidity]
Signed-off-by: Eric Biggers <ebiggers@google.com>

This allows us to fix the bug where Parallelism is inadvertantly
truncated to 8 bits in a backwards compatible way.

Signed-off-by: Joe Richey <joerichey@google.com>

We now create the `*pb.go` files via the makefile instead of though
`go generate`.

Signed-off-by: Joe Richey <joerichey@google.com>

Since Go 1.16 (which recently became the minimum supported Go version
for this project), the package io/ioutil is deprecated in favor of
equivalent functionality in the io and os packages.  staticcheck warns
about this.  Address all the warnings by switching to the non-deprecated
replacement functions.

Support for AES_256_HCTR2 filenames encryption was added in kernel
version 6.0.  The kernel doesn't yet support AES_256_HCTR2 for contents
encryption.