[Additional Layer Store] Enable Additional Layer Store to perform registry authentication

docker/docker_image_src.go

@@ -1,7 +1,9 @@
 package docker
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -11,6 +13,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"os/exec"
 	"strings"
 	"sync"
 
@@ -162,6 +165,34 @@ func newImageSourceAttempt(ctx context.Context, sys *types.SystemContext, logica
 		client.Close()
 		return nil, err
 	}
+
+	if h, err := sysregistriesv2.AdditionalLayerStoreAuthHelper(endpointSys); err == nil && h != "" {
+		acf := map[string]struct {
+			Username      string `json:"username,omitempty"`
+			Password      string `json:"password,omitempty"`
+			IdentityToken string `json:"identityToken,omitempty"`
+		}{
+			physicalRef.ref.String(): {
+				Username:      client.auth.Username,
+				Password:      client.auth.Password,
+				IdentityToken: client.auth.IdentityToken,
+			},
+		}
+		acfD, err := json.Marshal(acf)
+		if err != nil {
+			logrus.Warnf("failed to marshal auth config: %v", err)
+		} else {
+			cmd := exec.Command(h)
+			cmd.Stdin = bytes.NewReader(acfD)
+			if err := cmd.Run(); err != nil {
+				var stderr string
+				if ee, ok := err.(*exec.ExitError); ok {
+					stderr = string(ee.Stderr)
+				}
+				logrus.Warnf("Failed to call additional-layer-store-auth-helper (stderr:%s): %v", stderr, err)
+			}
+		}
+	}
 	return s, nil
 }
 

docs/containers-registries.conf.5.md

@@ -19,6 +19,12 @@ Container engines will use the `$HOME/.config/containers/registries.conf` if it
 `credential-helpers`
 : An array of default credential helpers used as external credential stores.  Note that "containers-auth.json" is a reserved value to use auth files as specified in containers-auth.json(5).  The credential helpers are set to `["containers-auth.json"]` if none are specified.
 
+`additional-layer-store-auth-helper`
+: A string containing the helper binary name. This enables passing registry credentials to an
+  Additional Layer Store every time an image is read using the `docker://`
+  transport so that it can access private registries. See the 'Enabling Additional Layer Store to access to private registries' section below for
+  more details.
+
 ### NAMESPACED `[[registry]]` SETTINGS
 
 The bulk of the configuration is represented as an array of `[[registry]]`
@@ -254,6 +260,30 @@ in order, and use the first one that exists.
 
 Note that a mirror is associated only with the current `[[registry]]` TOML table. If using the example above, pulling the image `registry.com/image:latest` will hence only reach out to `mirror.registry.com`, and the mirrors associated with `example.com/foo` will not be considered.
 
+### Enabling Additional Layer Store to access to private registries
+
+The `additional-layer-store-auth-helper` option enables passing registry
+credentials to an Additional Layer Store so that it can access private registries.
+
+When accessing a private registry via an Additional Layer Store, a helper binary needs to be provided. This helper binary is
+registered via the `additional-layer-store-auth-helper` option. Every time an image
+is read using the `docker://` transport, the specified helper binary is executed
+and receives registry credentials from stdin in the following format.
+
+```json
+{
+  "$image_reference": {
+    "username": "$username",
+    "password": "$password",
+    "identityToken": "$identityToken"
+  }
+}
+```
+
+The format of `$image_reference` is `$repo{:$tag|@$digest}`.
+
+Additional Layer Stores can use this helper binary to access the private registry.
+
 ## VERSION 1 FORMAT - DEPRECATED
 VERSION 1 format is still supported but it does not support
 using registry mirrors, longest-prefix matches, or location rewriting.

pkg/sysregistriesv2/system_registries_v2.go

@@ -248,6 +248,11 @@ type V2RegistriesConf struct {
 	// potentially use all unqualified-search registries
 	ShortNameMode string `toml:"short-name-mode"`
 
+	// AdditionalLayerStoreAuthHelper is a helper binary that receives
+	// registry credentials pass them to Additional Layer Store for
+	// registry authentication. These credentials are only collected when pulling (not pushing).
+	AdditionalLayerStoreAuthHelper string `toml:"additional-layer-store-auth-helper"`
+
 	shortNameAliasConf
 
 	// If you add any field, make sure to update Nonempty() below.
@@ -825,6 +830,16 @@ func CredentialHelpers(sys *types.SystemContext) ([]string, error) {
 	return config.partialV2.CredentialHelpers, nil
 }
 
+// AdditionalLayerStoreAuthHelper returns the helper for passing registry
+// credentials to Additional Layer Store.
+func AdditionalLayerStoreAuthHelper(sys *types.SystemContext) (string, error) {
+	config, err := getConfig(sys)
+	if err != nil {
+		return "", err
+	}
+	return config.partialV2.AdditionalLayerStoreAuthHelper, nil
+}
+
 // refMatchingSubdomainPrefix returns the length of ref
 // iff ref, which is a registry, repository namespace, repository or image reference (as formatted by
 // reference.Domain(), reference.Named.Name() or reference.Reference.String()
@@ -1051,6 +1066,11 @@ func (c *parsedConfig) updateWithConfigurationFrom(updates *parsedConfig) {
 		c.shortNameMode = updates.shortNameMode
 	}
 
+	// == Merge AdditionalLayerStoreAuthHelper:
+	if updates.partialV2.AdditionalLayerStoreAuthHelper != "" {
+		c.partialV2.AdditionalLayerStoreAuthHelper = updates.partialV2.AdditionalLayerStoreAuthHelper
+	}
+
 	// == Merge aliasCache:
 	// We don’t maintain (in fact we actively clear) c.partialV2.shortNameAliasConf.
 	c.aliasCache.updateWithConfigurationFrom(updates.aliasCache)

pkg/sysregistriesv2/system_registries_v2_test.go

@@ -57,6 +57,7 @@ var v2RegistriesConfEmptyTestData = []struct {
 	{nonempty: true, hasSetField: true, v: V2RegistriesConf{CredentialHelpers: []string{"a"}}},
 	{nonempty: true, hasSetField: true, v: V2RegistriesConf{ShortNameMode: "enforcing"}},
 	{nonempty: true, hasSetField: true, v: V2RegistriesConf{shortNameAliasConf: shortNameAliasConf{Aliases: map[string]string{"a": "example.com/b"}}}},
+	{nonempty: true, hasSetField: true, v: V2RegistriesConf{AdditionalLayerStoreAuthHelper: "example"}},
 }
 
 func TestV2RegistriesConfNonempty(t *testing.T) {