1 files changed, 126 insertions, 0 deletions
diff --git a/pkg/trust/registries.go b/pkg/trust/registries.go
new file mode 100644
index 000000000..0adc38232
--- /dev/null
+++ b/pkg/trust/registries.go
@@ -0,0 +1,126 @@
+package trust
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/containers/image/v5/types"
+	"github.com/docker/docker/pkg/homedir"
+	"github.com/ghodss/yaml"
+)
+
+// registryConfiguration is one of the files in registriesDirPath configuring lookaside locations, or the result of merging them all.
+// NOTE: Keep this in sync with docs/registries.d.md!
+type registryConfiguration struct {
+	DefaultDocker *registryNamespace `json:"default-docker"`
+	// The key is a namespace, using fully-expanded Docker reference format or parent namespaces (per dockerReference.PolicyConfiguration*),
+	Docker map[string]registryNamespace `json:"docker"`
+}
+
+// registryNamespace defines lookaside locations for a single namespace.
+type registryNamespace struct {
+	Lookaside        string `json:"lookaside"`         // For reading, and if LookasideStaging is not present, for writing.
+	LookasideStaging string `json:"lookaside-staging"` // For writing only.
+	SigStore         string `json:"sigstore"`          // For reading, and if SigStoreStaging is not present, for writing.
+	SigStoreStaging  string `json:"sigstore-staging"`  // For writing only.
+}
+
+// systemRegistriesDirPath is the path to registries.d.
+const systemRegistriesDirPath = "/etc/containers/registries.d"
+
+// userRegistriesDir is the path to the per user registries.d.
+var userRegistriesDir = filepath.FromSlash(".config/containers/registries.d")
+
+// RegistriesDirPath returns a path to registries.d
+func RegistriesDirPath(sys *types.SystemContext) string {
+	if sys != nil && sys.RegistriesDirPath != "" {
+		return sys.RegistriesDirPath
+	}
+	userRegistriesDirPath := filepath.Join(homedir.Get(), userRegistriesDir)
+	if _, err := os.Stat(userRegistriesDirPath); err == nil {
+		return userRegistriesDirPath
+	}
+	if sys != nil && sys.RootForImplicitAbsolutePaths != "" {
+		return filepath.Join(sys.RootForImplicitAbsolutePaths, systemRegistriesDirPath)
+	}
+
+	return systemRegistriesDirPath
+}
+
+// loadAndMergeConfig loads registries.d configuration files in dirPath
+func loadAndMergeConfig(dirPath string) (*registryConfiguration, error) {
+	mergedConfig := registryConfiguration{Docker: map[string]registryNamespace{}}
+	dockerDefaultMergedFrom := ""
+	nsMergedFrom := map[string]string{}
+
+	dir, err := os.Open(dirPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return &mergedConfig, nil
+		}
+		return nil, err
+	}
+	configNames, err := dir.Readdirnames(0)
+	if err != nil {
+		return nil, err
+	}
+	for _, configName := range configNames {
+		if !strings.HasSuffix(configName, ".yaml") {
+			continue
+		}
+		configPath := filepath.Join(dirPath, configName)
+		configBytes, err := ioutil.ReadFile(configPath)
+		if err != nil {
+			return nil, err
+		}
+		var config registryConfiguration
+		err = yaml.Unmarshal(configBytes, &config)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing %s: %w", configPath, err)
+		}
+		if config.DefaultDocker != nil {
+			if mergedConfig.DefaultDocker != nil {
+				return nil, fmt.Errorf(`error parsing signature storage configuration: "default-docker" defined both in "%s" and "%s"`,
+					dockerDefaultMergedFrom, configPath)
+			}
+			mergedConfig.DefaultDocker = config.DefaultDocker
+			dockerDefaultMergedFrom = configPath
+		}
+		for nsName, nsConfig := range config.Docker { // includes config.Docker == nil
+			if _, ok := mergedConfig.Docker[nsName]; ok {
+				return nil, fmt.Errorf(`error parsing signature storage configuration: "docker" namespace "%s" defined both in "%s" and "%s"`,
+					nsName, nsMergedFrom[nsName], configPath)
+			}
+			mergedConfig.Docker[nsName] = nsConfig
+			nsMergedFrom[nsName] = configPath
+		}
+	}
+	return &mergedConfig, nil
+}
+
+// registriesDConfigurationForScope returns registries.d configuration for the provided scope.
+// scope can be "" to return only the global default configuration entry.
+func registriesDConfigurationForScope(registryConfigs *registryConfiguration, scope string) *registryNamespace {
+	searchScope := scope
+	if searchScope != "" {
+		if !strings.Contains(searchScope, "/") {
+			val, exists := registryConfigs.Docker[searchScope]
+			if exists {
+				return &val
+			}
+		}
+		for range strings.Split(scope, "/") {
+			val, exists := registryConfigs.Docker[searchScope]
+			if exists {
+				return &val
+			}
+			if strings.Contains(searchScope, "/") {
+				searchScope = searchScope[:strings.LastIndex(searchScope, "/")]
+			}
+		}
+	}
+	return registryConfigs.DefaultDocker
+}