config: dynamic attestation configuration through S3 backed API (#1808)

internal/api/fetcher/configapi.go

@@ -0,0 +1,55 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package fetcher
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/edgelesssys/constellation/v2/internal/api/configapi"
+)
+
+// ConfigAPIFetcher fetches config API resources without authentication.
+type ConfigAPIFetcher struct {
+	*fetcher
+}
+
+// NewConfigAPIFetcher returns a new Fetcher.
+func NewConfigAPIFetcher() *ConfigAPIFetcher {
+	return &ConfigAPIFetcher{newFetcher()}
+}
+
+// NewConfigAPIFetcherWithClient returns a new Fetcher with custom http client.
+func NewConfigAPIFetcherWithClient(client HTTPClient) *ConfigAPIFetcher {
+	return &ConfigAPIFetcher{newFetcherWith(client)}
+}
+
+// FetchAzureSEVSNPVersionList fetches the version list information from the config API.
+func (f *ConfigAPIFetcher) FetchAzureSEVSNPVersionList(ctx context.Context, attestation configapi.AzureSEVSNPVersionList) (configapi.AzureSEVSNPVersionList, error) {
+	return fetch(ctx, f.httpc, attestation)
+}
+
+// FetchAzureSEVSNPVersion fetches the version information from the config API.
+func (f *ConfigAPIFetcher) FetchAzureSEVSNPVersion(ctx context.Context, attestation configapi.AzureSEVSNPVersionGet) (configapi.AzureSEVSNPVersionGet, error) {
+	// TODO(elchead): follow-up PR for AB#3045 to check signature (sigstore.VerifySignature)
+	return fetch(ctx, f.httpc, attestation)
+}
+
+// FetchLatestAzureSEVSNPVersion returns the latest versions of the given type.
+func (f *ConfigAPIFetcher) FetchLatestAzureSEVSNPVersion(ctx context.Context) (res configapi.AzureSEVSNPVersion, err error) {
+	var versions configapi.AzureSEVSNPVersionList
+	versions, err = f.FetchAzureSEVSNPVersionList(ctx, versions)
+	if err != nil {
+		return res, fmt.Errorf("fetching versions list: %w", err)
+	}
+	get := configapi.AzureSEVSNPVersionGet{Version: versions[0]} // get latest version (as sorted reversely alphanumerically)
+	get, err = f.FetchAzureSEVSNPVersion(ctx, get)
+	if err != nil {
+		return res, fmt.Errorf("failed fetching version: %w", err)
+	}
+	return get.AzureSEVSNPVersion, nil
+}