api: rename /api/versions to versionsapi and /api/attestationcfig to attestationconfigapi (#1876)

* rename to attestationconfigapi + put client and fetcher inside pkg

* rename api/version to versionsapi and put fetcher + client inside pkg

* rename AttestationConfigAPIFetcher to Fetcher

internal/api/attestationconfigapi/fetcher.go

@@ -0,0 +1,86 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package attestationconfigapi
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	apifetcher "github.com/edgelesssys/constellation/v2/internal/api/fetcher"
+	"github.com/edgelesssys/constellation/v2/internal/constants"
+	"github.com/edgelesssys/constellation/v2/internal/sigstore"
+)
+
+const cosignPublicKey = constants.CosignPublicKeyReleases
+
+// Fetcher fetches config API resources without authentication.
+type Fetcher interface {
+	FetchAzureSEVSNPVersion(ctx context.Context, azureVersion AzureSEVSNPVersionAPI) (AzureSEVSNPVersionAPI, error)
+	FetchAzureSEVSNPVersionList(ctx context.Context, attestation AzureSEVSNPVersionList) (AzureSEVSNPVersionList, error)
+	FetchAzureSEVSNPVersionLatest(ctx context.Context) (AzureSEVSNPVersionAPI, error)
+}
+
+// fetcher fetches AttestationCfg API resources without authentication.
+type fetcher struct {
+	apifetcher.HTTPClient
+}
+
+// NewFetcher returns a new apifetcher.
+func NewFetcher() Fetcher {
+	return NewFetcherWithClient(apifetcher.NewHTTPClient())
+}
+
+// NewFetcherWithClient returns a new fetcher with custom http client.
+func NewFetcherWithClient(client apifetcher.HTTPClient) Fetcher {
+	return &fetcher{client}
+}
+
+// FetchAzureSEVSNPVersionList fetches the version list information from the config API.
+func (f *fetcher) FetchAzureSEVSNPVersionList(ctx context.Context, attestation AzureSEVSNPVersionList) (AzureSEVSNPVersionList, error) {
+	return apifetcher.Fetch(ctx, f.HTTPClient, attestation)
+}
+
+// FetchAzureSEVSNPVersion fetches the version information from the config API.
+func (f *fetcher) FetchAzureSEVSNPVersion(ctx context.Context, azureVersion AzureSEVSNPVersionAPI) (AzureSEVSNPVersionAPI, error) {
+	fetchedVersion, err := apifetcher.Fetch(ctx, f.HTTPClient, azureVersion)
+	if err != nil {
+		return fetchedVersion, fmt.Errorf("fetch version %s: %w", fetchedVersion.Version, err)
+	}
+	versionBytes, err := json.Marshal(fetchedVersion)
+	if err != nil {
+		return fetchedVersion, fmt.Errorf("marshal version for verify %s: %w", azureVersion.Version, err)
+	}
+
+	signature, err := apifetcher.Fetch(ctx, f.HTTPClient, AzureSEVSNPVersionSignature{
+		Version: azureVersion.Version,
+	})
+	if err != nil {
+		return fetchedVersion, fmt.Errorf("fetch version %s signature: %w", azureVersion.Version, err)
+	}
+
+	err = sigstore.CosignVerifier{}.VerifySignature(versionBytes, signature.Signature, []byte(cosignPublicKey))
+	if err != nil {
+		return fetchedVersion, fmt.Errorf("verify version %s signature: %w", azureVersion.Version, err)
+	}
+	return fetchedVersion, nil
+}
+
+// FetchAzureSEVSNPVersionLatest returns the latest versions of the given type.
+func (f *fetcher) FetchAzureSEVSNPVersionLatest(ctx context.Context) (res AzureSEVSNPVersionAPI, err error) {
+	var list AzureSEVSNPVersionList
+	list, err = f.FetchAzureSEVSNPVersionList(ctx, list)
+	if err != nil {
+		return res, fmt.Errorf("fetching versions list: %w", err)
+	}
+	get := AzureSEVSNPVersionAPI{Version: list[0]} // get latest version (as sorted reversely alphanumerically)
+	get, err = f.FetchAzureSEVSNPVersion(ctx, get)
+	if err != nil {
+		return res, fmt.Errorf("fetching version: %w", err)
+	}
+	return get, nil
+}