As we continue iterating towards saving valid hashes for a package in a
depsfile lock file after installation and verifying them on future
installation, this prepares getproviders for the possibility of having
multiple valid hashes per package.
This will arise in future commits for two reasons:
- We will need to support both the legacy "zip hash" hashing scheme and
the new-style content-based hashing scheme because currently the
registry protocol is only able to produce the legacy scheme, but our
other installation sources prefer the content-based scheme. Therefore
packages will typically have a mixture of hashes of both types.
- Installing from an upstream registry will save the hashes for the
packages across all supported platforms, rather than just the current
platform, and we'll consider all of those valid for future installation
if we see both successful matching of the current platform checksum and
a signature verification for the checksums file as a whole.
This also includes some more preparation for the second case above in that
signatureAuthentication now supports AcceptableHashes and returns all of
the zip-based hashes it can find in the checksums file. This is a bit of
an abstraction leak because previously that authenticator considered its
"document" to just be opaque bytes, but we want to make sure that we can
only end up trusting _all_ of the hashes if we've verified that the
document is signed. Hopefully we'll make this better in a future commit
with some refactoring, but that's deferred for now in order to minimize
disruption to existing codepaths while we work towards a provider locking
MVP.
The logic for what constitutes a valid hash and how different hash schemes
are represented was starting to get sprawled over many different files and
packages.
Consistently with other cases where we've used named types to gather the
definition of a particular string into a single place and have the Go
compiler help us use it properly, this introduces both getproviders.Hash
representing a hash value and getproviders.HashScheme representing the
idea of a particular hash scheme.
Most of this changeset is updating existing uses of primitive strings to
uses of getproviders.Hash. The new type definitions are in
internal/getproviders/hash.go.
The "acceptable hashes" for a package is a set of hashes that the upstream
source considers to be good hashes for checking whether future installs
of the same provider version are considered to match this one.
Because the acceptable hashes are a package authentication concern and
they already need to be known (at least in part) to implement the
authenticators, here we add AcceptableHashes as an optional extra method
that an authenticator can implement.
Because these are hashes chosen by the upstream system, the caller must
make its own determination about their trustworthiness. The result of
authentication is likely to be an input to that, for example by
distrusting hashes produced by an authenticator that succeeds but doesn't
report having validated anything.
Earlier we introduced a new package hashing mechanism that is compatible
with both packed and unpacked packages, because it's a hash of the
contents of the package rather than of the archive it's delivered in.
However, we were using that only for the local selections file and not
for any remote package authentication yet.
The provider network mirrors protocol includes new-style hashes as a step
towards transitioning over to the new hash format in all cases, so this
new authenticator is here in preparation for verifying the checksums of
packages coming from network mirrors, for mirrors that support them.
For now this leaves us in a kinda confusing situation where we have both
NewPackageHashAuthentication for the new style and
NewArchiveChecksumAuthentication for the old style, which for the moment
is represented only by a doc comment on the latter. Hopefully we can
remove NewArchiveChecksumAuthentication in a future commit, if we can
get the registry updated to use the new hashing format.
Providers installed from the registry are accompanied by a list of
checksums (the "SHA256SUMS" file), which is cryptographically signed to
allow package authentication. The process of verifying this has multiple
steps:
- First we must verify that the SHA256 hash of the package archive
matches the expected hash. This could be done for local installations
too, in the future.
- Next we ensure that the expected hash returned as part of the registry
API response matches an entry in the checksum list.
- Finally we verify the cryptographic signature of the checksum list,
using the public keys provided by the registry.
Each of these steps is implemented as a separate PackageAuthentication
type. The local archive installation mechanism uses only the archive
checksum authenticator, and the HTTP installation uses all three in the
order given.
The package authentication system now also returns a result value, which
is used by command/init to display the result of the authentication
process.
There are three tiers of signature, each of which is presented
differently to the user:
- Signatures from the embedded HashiCorp public key indicate that the
provider is officially supported by HashiCorp;
- If the signing key is not from HashiCorp, it may have an associated
trust signature, which indicates that the provider is from one of
HashiCorp's trusted partners;
- Otherwise, if the signature is valid, this is a community provider.
Martin Atkins