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.
Earlier on in the stubbing of this package we realized that it wasn't
going to be possible to populate the authentication-related bits for all
packages because the relevant metadata just isn't available for packages
that are already local.
However, we just moved ahead with that awkward design at the time because
we needed to get other work done, and so we've been mostly producing
PackageMeta values with all-zeros hashes and just ignoring them entirely
as a temporary workaround.
This is a first step towards what is hopefully a more intuitive model:
authentication is an optional thing in a PackageMeta that is currently
populated only for packages coming from a registry.
So far this still just models checking a SHA256 hash, which is not a
sufficient set of checks for a real release but hopefully the "real"
implementation is a natural iteration of this starting point, and if not
then at least this interim step is a bit more honest about the fact that
Authentication will not be populated on every PackageMeta.
Built-in providers are special providers that are distributed as part of
Terraform CLI itself, rather than being installed separately. They always
live in the terraform.io/builtin/... namespace so it's easier to see that
they are special, and currently there is only one built-in provider named
"terraform".
Previous commits established the addressing scheme for built-in providers.
This commit makes the installer aware of them to the extent that it knows
not to try to install them the usual way and it's able to report an error
if the user requests a built-in provider that doesn't exist or tries to
impose a particular version constraint for a built-in provider.
For the moment the tests for this are the ones in the "command" package
because that's where the existing testing infrastructure for this
functionality lives. A later commit should add some more focused unit
tests here in the internal/providercache package, too.
Due to some incomplete rework of this function in an earlier commit, the
safety check for using the same directory as both the target and the
cache was inverted and was raising an error _unless_ they matched, rather
than _if_ they matched.
This change is verified by the e2etest TestInitProviders_pluginCache,
which is also updated to use the new-style cache directory layout as part
of this commit.
We previously skipped this one because it wasn't strictly necessary for
replicating the old "terraform init" behavior, but we do need it to work
so that things like the -plugin-dir option can behave correctly.
Linking packages from other cache directories and installing from unpacked
directories are fundamentally the same operation because a cache directory
is really just a collection of unpacked packages, so here we refactor
the LinkFromOtherCache functionality to actually be in
installFromLocalDir, and LinkFromOtherCache becomes a wrapper for
the installFromLocalDir function that just calculates the source and
target directories automatically and invalidates the metaCache.
On Unix-derived systems a directory must be marked as "executable" in
order to be accessible, so our previous mode of 0660 here was unsufficient
and would cause a failure if it happened to be the installer that was
creating the plugins directory for the first time here.
Now we'll make it executable and readable for all but only writable by
the same user/group. For consistency, we also make the selections file
itself readable by everyone. In both cases, the umask we are run with may
further constrain these modes.
Just as with the old installer mechanism, our goal is that explicit
provider installation is the only way that new provider versions can be
selected.
To achieve that, we conclude each call to EnsureProviderVersions by
writing a selections lock file into the target directory. A later caller
can then recall the selections from that file by calling SelectedPackages,
which both ensures that it selects the same set of versions and also
verifies that the checksums recorded by the installer still match.
This new selections.json file has a different layout than our old
plugins.json lock file. Not only does it use a different hashing algorithm
than before, we also record explicitly which version of each provider
was selected. In the old model, we'd repeat normal discovery when
reloading the lock file and then fail with a confusing error message if
discovery happened to select a different version, but now we'll be able
to distinguish between a package that's gone missing since installation
(which could previously have then selected a different available version)
from a package that has been modified.
For the old-style provider cache directory model we hashed the individual
executable file for each provider. That's no longer appropriate because
we're giving each provider package a whole directory to itself where it
can potentially have many files.
This therefore introduces a new directory-oriented hashing algorithm, and
it's just using the Go Modules directory hashing algorithm directly
because that's already had its cross-platform quirks and other wrinkles
addressed during the Go Modules release process, and is now used
prolifically enough in Go codebases that breaking changes to the upstream
algorithm would be very expensive to the Go ecosystem.
This is also a bit of forward planning, anticipating that later we'll use
hashes in a top-level lock file intended to be checked in to user version
control, and then use those hashes also to verify packages _during_
installation, where we'd need to be able to hash unpacked zip files. The
Go Modules hashing algorithm is already implemented to consistently hash
both a zip file and an unpacked version of that zip file.
We've been using the models from the "moduledeps" package to represent our
provider dependencies everywhere since the idea of provider dependencies
was introduced in Terraform 0.10, but that model is not convenient to use
for any use-case other than the "terraform providers" command that needs
individual-module-level detail.
To make things easier for new codepaths working with the new-style
provider installer, here we introduce a new model type
getproviders.Requirements which is based on the type the new installer was
already taking as its input. We have new methods in the states, configs,
and earlyconfig packages to produce values of this type, and a helper
to merge Requirements together so we can combine config-derived and
state-derived requirements together during installation.
The advantage of this new model over the moduledeps one is that all of
recursive module walking is done up front and we produce a simple, flat
structure that is more convenient for the main use-cases of selecting
providers for installation and then finding providers in the local cache
to use them for other operations.
This new model is _not_ suitable for implementing "terraform providers"
because it does not retain module-specific requirement details. Therefore
we will likely keep using moduledeps for "terraform providers" for now,
and then possibly at a later time consider specializing the moduledeps
logic for only what "terraform providers" needs, because it seems to be
the only use-case that needs to retain that level of detail.
This was incorrectly removing the _source_ entry prior to creating the
symlink, therefore ending up with a dangling symlink and no source file.
This wasn't obvious before because the test case for LinkFromOtherCache
was also incorrectly named and therefore wasn't running. Fixing the name
of that test made this problem apparent.
The TestLinkFromOtherCache test case now ends up seeing the final resolved
directory rather than the symlink target, because of upstream changes
to the internal/getproviders filesystem scanning logic to handle symlinks
properly.
There's a lot going on in these functions that can be hard to follow from
the outside, so we'll add some additional trace logging so that we can
more easily understand why things are behaving the way they are.
When a provider source produces an HTTP URL location we'll expect it to
resolve to a zip file, which we'll first download to a temporary
directory and then treat it like a local archive.
When a provider source produces a local archive path we'll expect it to
be a zip file and extract it into the target directory.
This does not yet include an implementation of installing from an
already-unpacked local directory. That will follow in a subsequent commit,
likely following a similar principle as in Dir.LinkFromOtherCache.
These new functions allow command implementations to get hold of the
providercache objects and installation source object derived from the
current CLI configuration.
This is not tested yet, but it's a compilable strawman implementation of
the necessary sequence of events to coordinate all of the moving parts
of running a provider installation operation.
This will inevitably see more iteration in later commits as we complete
the surrounding parts and wire it up to be used by "terraform init". So
far, it's just dead code not called by any other package.
The Installer type will encapsulate the logic for running an entire
provider installation request: given a set of providers to install, it
will determine a method to obtain each of them (or detect that they are
already installed) and then take the necessary actions.
So far it doesn't do anything, but this stubs out an interface by which
the caller can request ongoing notifications during an installation
operation.
This will eventually be responsible for actually retrieving a package from
a source and then installing it into the cache directory, but for the
moment it's just a stub to complete the proposed API, which I intend to
test in a subsequent commit by writing the full "Installer" API that will
encapsulate the full installation logic.
When a system-wide shared plugin cache is configured, we'll want to make
use of entries already in the shared cache when populating a local
(configuration-specific) cache.
This new method LinkFromOtherCache encapsulates the work of placing a link
from one cache to another. If possible it will create a symlink, therefore
retaining a key advantage of configuring a shared plugin cache, but
otherwise we'll do a deep copy of the package directory from one cache
to the other.
Our old provider installer would always skip trying to create symlinks on
Windows because Go standard library support for os.Symlink on Windows
was inconsistent in older versions. However, os.Symlink can now create
symlinks using a new API introduced in a Windows 10 update and cleanly
fail if symlink creation is impossible, so it's safe for us to just
try to create the symlink and react if that produces an error, just as we
used to do on non-Windows systems when possibly creating symlinks on
filesystems that cannot support them.
Historically our logic to handle discovering and installing providers has
been spread across several different packages. This package is intended
to become the home of all logic related to what is now called "provider
cache directories", which means directories on local disk where Terraform
caches providers in a form that is ready to run.
That includes both logic related to interrogating items already in a cache
(included in this commit) and logic related to inserting new items into
the cache from upstream provider sources (to follow in later commits).
These new codepaths are focused on providers and do not include other
plugin types (provisioners and credentials helpers), because providers are
the only plugin type that is represented by a heirarchical, decentralized
namespace and the only plugin type that has an auto-installation protocol
defined. The existing codepaths will remain to support the handling of
the other plugin types that require manual installation and that use only
a flat, locally-defined namespace.
Alisdair McDiarmid