Put back findRelease for now

pkg/autoupdate/tuf/autoupdate.go

@@ -5,10 +5,12 @@ package tuf
 
 import (
 	_ "embed"
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strconv"
 	"time"
 
@@ -25,9 +27,8 @@ var rootJson []byte
 
 // Configuration defaults
 const (
-	DefaultTufServer            = "https://tuf.kolide.com"
-	tufDirectoryName            = "tuf"
-	genericReleaseVersionFormat = "%s/%s/%s/release.json" // <binary>/<os>/<channel>/release.json
+	DefaultTufServer = "https://tuf.kolide.com"
+	tufDirectoryName = "tuf"
 )
 
 // Binaries handled by autoupdater
@@ -238,7 +239,7 @@ func (ta *TufAutoupdater) checkForUpdate() error {
 // downloadUpdate will download a new release for the given binary, if available from TUF
 // and not already downloaded.
 func (ta *TufAutoupdater) downloadUpdate(binary autoupdatableBinary, targets data.TargetFiles) (string, error) {
-	release, releaseMetadata, err := findRelease(binary, targets, ta.channel)
+	release, releaseMetadata, err := ta.findRelease(binary, targets)
 	if err != nil {
 		return "", fmt.Errorf("could not find release: %w", err)
 	}
@@ -258,6 +259,45 @@ func (ta *TufAutoupdater) downloadUpdate(binary autoupdatableBinary, targets dat
 	return release, nil
 }
 
+// findRelease checks the latest data from TUF (in `targets`) to see whether a new release
+// has been published for our channel. If it has, it returns the target for that release
+// and its associated metadata.
+func (ta *TufAutoupdater) findRelease(binary autoupdatableBinary, targets data.TargetFiles) (string, data.TargetFileMeta, error) {
+	// First, find the target that the channel release file is pointing to
+	var releaseTarget string
+	targetReleaseFile := fmt.Sprintf("%s/%s/%s/release.json", binary, runtime.GOOS, ta.channel)
+	for targetName, target := range targets {
+		if targetName != targetReleaseFile {
+			continue
+		}
+
+		// We found the release file that matches our OS and binary. Evaluate it
+		// to see if we're on this latest version.
+		var custom ReleaseFileCustomMetadata
+		if err := json.Unmarshal(*target.Custom, &custom); err != nil {
+			return "", data.TargetFileMeta{}, fmt.Errorf("could not unmarshal release file custom metadata: %w", err)
+		}
+
+		releaseTarget = custom.Target
+		break
+	}
+
+	if releaseTarget == "" {
+		return "", data.TargetFileMeta{}, fmt.Errorf("expected release file %s for binary %s to be in targets but it was not", targetReleaseFile, binary)
+	}
+
+	// Now, get the metadata for our release target
+	for targetName, target := range targets {
+		if targetName != releaseTarget {
+			continue
+		}
+
+		return filepath.Base(releaseTarget), target, nil
+	}
+
+	return "", data.TargetFileMeta{}, fmt.Errorf("could not find metadata for release target %s for binary %s", targetReleaseFile, binary)
+}
+
 // storeError saves errors that occur during the periodic check for updates, so that they
 // can be queryable via the `kolide_tuf_autoupdater_errors` table.
 func (ta *TufAutoupdater) storeError(autoupdateErr error) {