Merge pull request #15466 from mtrmac/image-trust-sigstore

podman image trust overhaul, incl. sigstore

12 files changed, 1086 insertions, 355 deletions

diff --git a/cmd/podman/images/trust_set.go b/cmd/podman/images/trust_set.go
index 832e9f724..e7339f0b1 100644
--- a/cmd/podman/images/trust_set.go
+++ b/cmd/podman/images/trust_set.go
@@ -53,7 +53,7 @@ File(s) must exist before using this command`)
 }
 
 func setTrust(cmd *cobra.Command, args []string) error {
-	validTrustTypes := []string{"accept", "insecureAcceptAnything", "reject", "signedBy"}
+	validTrustTypes := []string{"accept", "insecureAcceptAnything", "reject", "signedBy", "sigstoreSigned"}
 
 	valid, err := isValidImageURI(args[0])
 	if err != nil || !valid {
@@ -61,7 +61,7 @@ func setTrust(cmd *cobra.Command, args []string) error {
 	}
 
 	if !util.StringInSlice(setOptions.Type, validTrustTypes) {
-		return fmt.Errorf("invalid choice: %s (choose from 'accept', 'reject', 'signedBy')", setOptions.Type)
+		return fmt.Errorf("invalid choice: %s (choose from 'accept', 'reject', 'signedBy', 'sigstoreSigned')", setOptions.Type)
 	}
 	return registry.ImageEngine().SetTrust(registry.Context(), args, setOptions)
 }
diff --git a/docs/source/markdown/podman-image-trust.1.md b/docs/source/markdown/podman-image-trust.1.md
index 4e80bdcf5..2a7da82cc 100644
--- a/docs/source/markdown/podman-image-trust.1.md
+++ b/docs/source/markdown/podman-image-trust.1.md
@@ -32,7 +32,8 @@ Trust **type** provides a way to:
 
 Allowlist ("accept") or
 Denylist ("reject") registries or
-Require signature (“signedBy”).
+Require a simple signing signature (“signedBy”),
+Require a sigstore signature ("sigstoreSigned").
 
 Trust may be updated using the command **podman image trust set** for an existing trust scope.
 
@@ -45,12 +46,14 @@ Trust may be updated using the command **podman image trust set** for an existin
 #### **--pubkeysfile**, **-f**=*KEY1*
   A path to an exported public key on the local system. Key paths
   will be referenced in policy.json. Any path to a file may be used but locating the file in **/etc/pki/containers** is recommended. Options may be used multiple times to
-  require an image be signed by multiple keys.  The **--pubkeysfile** option is required for the **signedBy** type.
+  require an image be signed by multiple keys.  The **--pubkeysfile** option is required for the **signedBy** and **sigstoreSigned** types.
 
 #### **--type**, **-t**=*value*
   The trust type for this policy entry.
   Accepted values:
-    **signedBy** (default): Require signatures with corresponding list of
+    **signedBy** (default): Require simple signing signatures with corresponding list of
+                        public keys
+    **sigstoreSigned**: Require sigstore signatures with corresponding list of
                         public keys
     **accept**: do not require any signatures for this
             registry scope
diff --git a/pkg/domain/infra/abi/trust.go b/pkg/domain/infra/abi/trust.go
index 0e3d8fad9..c58ddff06 100644
--- a/pkg/domain/infra/abi/trust.go
+++ b/pkg/domain/infra/abi/trust.go
@@ -2,16 +2,11 @@ package abi
 
 import (
 	"context"
-	"encoding/json"
-	"errors"
 	"fmt"
 	"io/ioutil"
-	"os"
-	"strings"
 
 	"github.com/containers/podman/v4/pkg/domain/entities"
 	"github.com/containers/podman/v4/pkg/trust"
-	"github.com/sirupsen/logrus"
 )
 
 func (ir *ImageEngine) ShowTrust(ctx context.Context, args []string, options entities.ShowTrustOptions) (*entities.ShowTrustReport, error) {
@@ -34,11 +29,7 @@ func (ir *ImageEngine) ShowTrust(ctx context.Context, args []string, options ent
 	if len(options.RegistryPath) > 0 {
 		report.SystemRegistriesDirPath = options.RegistryPath
 	}
-	policyContentStruct, err := trust.GetPolicy(policyPath)
-	if err != nil {
-		return nil, fmt.Errorf("could not read trust policies: %w", err)
-	}
-	report.Policies, err = getPolicyShowOutput(policyContentStruct, report.SystemRegistriesDirPath)
+	report.Policies, err = trust.PolicyDescription(policyPath, report.SystemRegistriesDirPath)
 	if err != nil {
 		return nil, fmt.Errorf("could not show trust policies: %w", err)
 	}
@@ -46,133 +37,19 @@ func (ir *ImageEngine) ShowTrust(ctx context.Context, args []string, options ent
 }
 
 func (ir *ImageEngine) SetTrust(ctx context.Context, args []string, options entities.SetTrustOptions) error {
-	var (
-		policyContentStruct trust.PolicyContent
-		newReposContent     []trust.RepoContent
-	)
-	trustType := options.Type
-	if trustType == "accept" {
-		trustType = "insecureAcceptAnything"
-	}
-
-	pubkeysfile := options.PubKeysFile
-	if len(pubkeysfile) == 0 && trustType == "signedBy" {
-		return errors.New("at least one public key must be defined for type 'signedBy'")
+	if len(args) != 1 {
+		return fmt.Errorf("SetTrust called with unexpected %d args", len(args))
 	}
+	scope := args[0]
 
 	policyPath := trust.DefaultPolicyPath(ir.Libpod.SystemContext())
 	if len(options.PolicyPath) > 0 {
 		policyPath = options.PolicyPath
 	}
-	_, err := os.Stat(policyPath)
-	if !os.IsNotExist(err) {
-		policyContent, err := ioutil.ReadFile(policyPath)
-		if err != nil {
-			return err
-		}
-		if err := json.Unmarshal(policyContent, &policyContentStruct); err != nil {
-			return errors.New("could not read trust policies")
-		}
-	}
-	if len(pubkeysfile) != 0 {
-		for _, filepath := range pubkeysfile {
-			newReposContent = append(newReposContent, trust.RepoContent{Type: trustType, KeyType: "GPGKeys", KeyPath: filepath})
-		}
-	} else {
-		newReposContent = append(newReposContent, trust.RepoContent{Type: trustType})
-	}
-	if args[0] == "default" {
-		policyContentStruct.Default = newReposContent
-	} else {
-		if len(policyContentStruct.Default) == 0 {
-			return errors.New("default trust policy must be set")
-		}
-		registryExists := false
-		for transport, transportval := range policyContentStruct.Transports {
-			_, registryExists = transportval[args[0]]
-			if registryExists {
-				policyContentStruct.Transports[transport][args[0]] = newReposContent
-				break
-			}
-		}
-		if !registryExists {
-			if policyContentStruct.Transports == nil {
-				policyContentStruct.Transports = make(map[string]trust.RepoMap)
-			}
-			if policyContentStruct.Transports["docker"] == nil {
-				policyContentStruct.Transports["docker"] = make(map[string][]trust.RepoContent)
-			}
-			policyContentStruct.Transports["docker"][args[0]] = append(policyContentStruct.Transports["docker"][args[0]], newReposContent...)
-		}
-	}
-
-	data, err := json.MarshalIndent(policyContentStruct, "", "    ")
-	if err != nil {
-		return fmt.Errorf("error setting trust policy: %w", err)
-	}
-	return ioutil.WriteFile(policyPath, data, 0644)
-}
-
-func getPolicyShowOutput(policyContentStruct trust.PolicyContent, systemRegistriesDirPath string) ([]*trust.Policy, error) {
-	var output []*trust.Policy
-
-	registryConfigs, err := trust.LoadAndMergeConfig(systemRegistriesDirPath)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(policyContentStruct.Default) > 0 {
-		defaultPolicyStruct := trust.Policy{
-			Transport: "all",
-			Name:      "* (default)",
-			RepoName:  "default",
-			Type:      trustTypeDescription(policyContentStruct.Default[0].Type),
-		}
-		output = append(output, &defaultPolicyStruct)
-	}
-	for transport, transval := range policyContentStruct.Transports {
-		if transport == "docker" {
-			transport = "repository"
-		}
 
-		for repo, repoval := range transval {
-			tempTrustShowOutput := trust.Policy{
-				Name:      repo,
-				RepoName:  repo,
-				Transport: transport,
-				Type:      trustTypeDescription(repoval[0].Type),
-			}
-			// TODO - keyarr is not used and I don't know its intent; commenting out for now for someone to fix later
-			// keyarr := []string{}
-			uids := []string{}
-			for _, repoele := range repoval {
-				if len(repoele.KeyPath) > 0 {
-					// keyarr = append(keyarr, repoele.KeyPath)
-					uids = append(uids, trust.GetGPGIdFromKeyPath(repoele.KeyPath)...)
-				}
-				if len(repoele.KeyData) > 0 {
-					// keyarr = append(keyarr, string(repoele.KeyData))
-					uids = append(uids, trust.GetGPGIdFromKeyData(repoele.KeyData)...)
-				}
-			}
-			tempTrustShowOutput.GPGId = strings.Join(uids, ", ")
-
-			registryNamespace := trust.HaveMatchRegistry(repo, registryConfigs)
-			if registryNamespace != nil {
-				tempTrustShowOutput.SignatureStore = registryNamespace.SigStore
-			}
-			output = append(output, &tempTrustShowOutput)
-		}
-	}
-	return output, nil
-}
-
-var typeDescription = map[string]string{"insecureAcceptAnything": "accept", "signedBy": "signed", "reject": "reject"}
-
-func trustTypeDescription(trustType string) string {
-	trustDescription, exist := typeDescription[trustType]
-	if !exist {
-		logrus.Warnf("Invalid trust type %s", trustType)
-	}
-	return trustDescription
+	return trust.AddPolicyEntries(policyPath, trust.AddPolicyEntriesInput{
+		Scope:       scope,
+		Type:        options.Type,
+		PubKeyFiles: options.PubKeysFile,
+	})
 }
diff --git a/pkg/trust/config.go b/pkg/trust/config.go
deleted file mode 100644
index 6186d4cbd..000000000
--- a/pkg/trust/config.go
+++ /dev/null
@@ -1,12 +0,0 @@
-package trust
-
-// Policy describes a basic trust policy configuration
-type Policy struct {
-	Transport      string   `json:"transport"`
-	Name           string   `json:"name,omitempty"`
-	RepoName       string   `json:"repo_name,omitempty"`
-	Keys           []string `json:"keys,omitempty"`
-	SignatureStore string   `json:"sigstore,omitempty"`
-	Type           string   `json:"type"`
-	GPGId          string   `json:"gpg_id,omitempty"`
-}
diff --git a/pkg/trust/policy.go b/pkg/trust/policy.go
new file mode 100644
index 000000000..326fe17af
--- /dev/null
+++ b/pkg/trust/policy.go
@@ -0,0 +1,248 @@
+package trust
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/containers/image/v5/types"
+	"github.com/sirupsen/logrus"
+)
+
+// policyContent is the overall structure of a policy.json file (= c/image/v5/signature.Policy)
+type policyContent struct {
+	Default    []repoContent     `json:"default"`
+	Transports transportsContent `json:"transports,omitempty"`
+}
+
+// transportsContent contains policies for individual transports (= c/image/v5/signature.Policy.Transports)
+type transportsContent map[string]repoMap
+
+// repoMap maps a scope name to requirements that apply to that scope (= c/image/v5/signature.PolicyTransportScopes)
+type repoMap map[string][]repoContent
+
+// repoContent is a single policy requirement (one of possibly several for a scope), representing all of the individual alternatives in a single merged struct
+// (= c/image/v5/signature.{PolicyRequirement,pr*})
+type repoContent struct {
+	Type           string          `json:"type"`
+	KeyType        string          `json:"keyType,omitempty"`
+	KeyPath        string          `json:"keyPath,omitempty"`
+	KeyPaths       []string        `json:"keyPaths,omitempty"`
+	KeyData        string          `json:"keyData,omitempty"`
+	SignedIdentity json.RawMessage `json:"signedIdentity,omitempty"`
+}
+
+// genericPolicyContent is the overall structure of a policy.json file (= c/image/v5/signature.Policy), using generic data for individual requirements.
+type genericPolicyContent struct {
+	Default    json.RawMessage          `json:"default"`
+	Transports genericTransportsContent `json:"transports,omitempty"`
+}
+
+// genericTransportsContent contains policies for individual transports (= c/image/v5/signature.Policy.Transports), using generic data for individual requirements.
+type genericTransportsContent map[string]genericRepoMap
+
+// genericRepoMap maps a scope name to requirements that apply to that scope (= c/image/v5/signature.PolicyTransportScopes)
+type genericRepoMap map[string]json.RawMessage
+
+// DefaultPolicyPath returns a path to the default policy of the system.
+func DefaultPolicyPath(sys *types.SystemContext) string {
+	systemDefaultPolicyPath := "/etc/containers/policy.json"
+	if sys != nil {
+		if sys.SignaturePolicyPath != "" {
+			return sys.SignaturePolicyPath
+		}
+		if sys.RootForImplicitAbsolutePaths != "" {
+			return filepath.Join(sys.RootForImplicitAbsolutePaths, systemDefaultPolicyPath)
+		}
+	}
+	return systemDefaultPolicyPath
+}
+
+// gpgIDReader returns GPG key IDs of keys stored at the provided path.
+// It exists only for tests, production code should always use getGPGIdFromKeyPath.
+type gpgIDReader func(string) []string
+
+// createTmpFile creates a temp file under dir and writes the content into it
+func createTmpFile(dir, pattern string, content []byte) (string, error) {
+	tmpfile, err := ioutil.TempFile(dir, pattern)
+	if err != nil {
+		return "", err
+	}
+	defer tmpfile.Close()
+
+	if _, err := tmpfile.Write(content); err != nil {
+		return "", err
+	}
+	return tmpfile.Name(), nil
+}
+
+// getGPGIdFromKeyPath returns GPG key IDs of keys stored at the provided path.
+func getGPGIdFromKeyPath(path string) []string {
+	cmd := exec.Command("gpg2", "--with-colons", path)
+	results, err := cmd.Output()
+	if err != nil {
+		logrus.Errorf("Getting key identity: %s", err)
+		return nil
+	}
+	return parseUids(results)
+}
+
+// getGPGIdFromKeyData returns GPG key IDs of keys in the provided keyring.
+func getGPGIdFromKeyData(idReader gpgIDReader, key string) []string {
+	decodeKey, err := base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		logrus.Errorf("%s, error decoding key data", err)
+		return nil
+	}
+	tmpfileName, err := createTmpFile("", "", decodeKey)
+	if err != nil {
+		logrus.Errorf("Creating key date temp file %s", err)
+	}
+	defer os.Remove(tmpfileName)
+	return idReader(tmpfileName)
+}
+
+func parseUids(colonDelimitKeys []byte) []string {
+	var parseduids []string
+	scanner := bufio.NewScanner(bytes.NewReader(colonDelimitKeys))
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "uid:") || strings.HasPrefix(line, "pub:") {
+			uid := strings.Split(line, ":")[9]
+			if uid == "" {
+				continue
+			}
+			parseduid := uid
+			if strings.Contains(uid, "<") && strings.Contains(uid, ">") {
+				parseduid = strings.SplitN(strings.SplitAfterN(uid, "<", 2)[1], ">", 2)[0]
+			}
+			parseduids = append(parseduids, parseduid)
+		}
+	}
+	return parseduids
+}
+
+// getPolicy parses policy.json into policyContent.
+func getPolicy(policyPath string) (policyContent, error) {
+	var policyContentStruct policyContent
+	policyContent, err := ioutil.ReadFile(policyPath)
+	if err != nil {
+		return policyContentStruct, fmt.Errorf("unable to read policy file: %w", err)
+	}
+	if err := json.Unmarshal(policyContent, &policyContentStruct); err != nil {
+		return policyContentStruct, fmt.Errorf("could not parse trust policies from %s: %w", policyPath, err)
+	}
+	return policyContentStruct, nil
+}
+
+var typeDescription = map[string]string{"insecureAcceptAnything": "accept", "signedBy": "signed", "sigstoreSigned": "sigstoreSigned", "reject": "reject"}
+
+func trustTypeDescription(trustType string) string {
+	trustDescription, exist := typeDescription[trustType]
+	if !exist {
+		logrus.Warnf("Invalid trust type %s", trustType)
+	}
+	return trustDescription
+}
+
+// AddPolicyEntriesInput collects some parameters to AddPolicyEntries,
+// primarily so that the callers use named values instead of just strings in a sequence.
+type AddPolicyEntriesInput struct {
+	Scope       string // "default" or a docker/atomic scope name
+	Type        string
+	PubKeyFiles []string // For signature enforcement types, paths to public keys files (where the image needs to be signed by at least one key from _each_ of the files). File format depends on Type.
+}
+
+// AddPolicyEntries adds one or more policy entries necessary to implement AddPolicyEntriesInput.
+func AddPolicyEntries(policyPath string, input AddPolicyEntriesInput) error {
+	var (
+		policyContentStruct genericPolicyContent
+		newReposContent     []repoContent
+	)
+	trustType := input.Type
+	if trustType == "accept" {
+		trustType = "insecureAcceptAnything"
+	}
+	pubkeysfile := input.PubKeyFiles
+
+	// The error messages in validation failures use input.Type instead of trustType to match the user’s input.
+	switch trustType {
+	case "insecureAcceptAnything", "reject":
+		if len(pubkeysfile) != 0 {
+			return fmt.Errorf("%d public keys unexpectedly provided for trust type %v", len(pubkeysfile), input.Type)
+		}
+		newReposContent = append(newReposContent, repoContent{Type: trustType})
+
+	case "signedBy":
+		if len(pubkeysfile) == 0 {
+			return errors.New("at least one public key must be defined for type 'signedBy'")
+		}
+		for _, filepath := range pubkeysfile {
+			newReposContent = append(newReposContent, repoContent{Type: trustType, KeyType: "GPGKeys", KeyPath: filepath})
+		}
+
+	case "sigstoreSigned":
+		if len(pubkeysfile) == 0 {
+			return errors.New("at least one public key must be defined for type 'sigstoreSigned'")
+		}
+		for _, filepath := range pubkeysfile {
+			newReposContent = append(newReposContent, repoContent{Type: trustType, KeyPath: filepath})
+		}
+
+	default:
+		return fmt.Errorf("unknown trust type %q", input.Type)
+	}
+	newReposJSON, err := json.Marshal(newReposContent)
+	if err != nil {
+		return err
+	}
+
+	_, err = os.Stat(policyPath)
+	if !os.IsNotExist(err) {
+		policyContent, err := ioutil.ReadFile(policyPath)
+		if err != nil {
+			return err
+		}
+		if err := json.Unmarshal(policyContent, &policyContentStruct); err != nil {
+			return errors.New("could not read trust policies")
+		}
+	}
+	if input.Scope == "default" {
+		policyContentStruct.Default = json.RawMessage(newReposJSON)
+	} else {
+		if len(policyContentStruct.Default) == 0 {
+			return errors.New("default trust policy must be set")
+		}
+		registryExists := false
+		for transport, transportval := range policyContentStruct.Transports {
+			_, registryExists = transportval[input.Scope]
+			if registryExists {
+				policyContentStruct.Transports[transport][input.Scope] = json.RawMessage(newReposJSON)
+				break
+			}
+		}
+		if !registryExists {
+			if policyContentStruct.Transports == nil {
+				policyContentStruct.Transports = make(map[string]genericRepoMap)
+			}
+			if policyContentStruct.Transports["docker"] == nil {
+				policyContentStruct.Transports["docker"] = make(map[string]json.RawMessage)
+			}
+			policyContentStruct.Transports["docker"][input.Scope] = json.RawMessage(newReposJSON)
+		}
+	}
+
+	data, err := json.MarshalIndent(policyContentStruct, "", "    ")
+	if err != nil {
+		return fmt.Errorf("error setting trust policy: %w", err)
+	}
+	return ioutil.WriteFile(policyPath, data, 0644)
+}
diff --git a/pkg/trust/policy_test.go b/pkg/trust/policy_test.go
new file mode 100644
index 000000000..3952b72c3
--- /dev/null
+++ b/pkg/trust/policy_test.go
@@ -0,0 +1,196 @@
+package trust
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/containers/image/v5/signature"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAddPolicyEntries(t *testing.T) {
+	tempDir := t.TempDir()
+	policyPath := filepath.Join(tempDir, "policy.json")
+
+	minimalPolicy := &signature.Policy{
+		Default: []signature.PolicyRequirement{
+			signature.NewPRInsecureAcceptAnything(),
+		},
+	}
+	minimalPolicyJSON, err := json.Marshal(minimalPolicy)
+	require.NoError(t, err)
+	err = os.WriteFile(policyPath, minimalPolicyJSON, 0600)
+	require.NoError(t, err)
+
+	// Invalid input:
+	for _, invalid := range []AddPolicyEntriesInput{
+		{
+			Scope:       "default",
+			Type:        "accept",
+			PubKeyFiles: []string{"/does-not-make-sense"},
+		},
+		{
+			Scope:       "default",
+			Type:        "insecureAcceptAnything",
+			PubKeyFiles: []string{"/does-not-make-sense"},
+		},
+		{
+			Scope:       "default",
+			Type:        "reject",
+			PubKeyFiles: []string{"/does-not-make-sense"},
+		},
+		{
+			Scope:       "default",
+			Type:        "signedBy",
+			PubKeyFiles: []string{}, // A key is missing
+		},
+		{
+			Scope:       "default",
+			Type:        "sigstoreSigned",
+			PubKeyFiles: []string{}, // A key is missing
+		},
+		{
+			Scope:       "default",
+			Type:        "this-is-unknown",
+			PubKeyFiles: []string{},
+		},
+	} {
+		err := AddPolicyEntries(policyPath, invalid)
+		assert.Error(t, err, "%#v", invalid)
+	}
+
+	err = AddPolicyEntries(policyPath, AddPolicyEntriesInput{
+		Scope: "default",
+		Type:  "reject",
+	})
+	assert.NoError(t, err)
+	err = AddPolicyEntries(policyPath, AddPolicyEntriesInput{
+		Scope: "quay.io/accepted",
+		Type:  "accept",
+	})
+	assert.NoError(t, err)
+	err = AddPolicyEntries(policyPath, AddPolicyEntriesInput{
+		Scope:       "quay.io/multi-signed",
+		Type:        "signedBy",
+		PubKeyFiles: []string{"/1.pub", "/2.pub"},
+	})
+	assert.NoError(t, err)
+	err = AddPolicyEntries(policyPath, AddPolicyEntriesInput{
+		Scope:       "quay.io/sigstore-signed",
+		Type:        "sigstoreSigned",
+		PubKeyFiles: []string{"/1.pub", "/2.pub"},
+	})
+	assert.NoError(t, err)
+
+	// Test that the outcome is consumable, and compare it with the expected values.
+	parsedPolicy, err := signature.NewPolicyFromFile(policyPath)
+	require.NoError(t, err)
+	assert.Equal(t, &signature.Policy{
+		Default: signature.PolicyRequirements{
+			signature.NewPRReject(),
+		},
+		Transports: map[string]signature.PolicyTransportScopes{
+			"docker": {
+				"quay.io/accepted": {
+					signature.NewPRInsecureAcceptAnything(),
+				},
+				"quay.io/multi-signed": {
+					xNewPRSignedByKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+					xNewPRSignedByKeyPath(t, "/2.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				},
+				"quay.io/sigstore-signed": {
+					xNewPRSigstoreSignedKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+					xNewPRSigstoreSignedKeyPath(t, "/2.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				},
+			},
+		},
+	}, parsedPolicy)
+
+	// Test that completely unknown JSON is preserved
+	jsonWithUnknownData := `{
+    "default": [
+        {
+            "type": "this is unknown",
+			"unknown field": "should be preserved"
+        }
+    ],
+    "transports":
+        {
+            "docker-daemon":
+                {
+                    "": [{
+						"type":"this is unknown 2",
+						"unknown field 2": "should be preserved 2"
+						}]
+                }
+        }
+}`
+	err = os.WriteFile(policyPath, []byte(jsonWithUnknownData), 0600)
+	require.NoError(t, err)
+	err = AddPolicyEntries(policyPath, AddPolicyEntriesInput{
+		Scope:       "quay.io/innocuous",
+		Type:        "signedBy",
+		PubKeyFiles: []string{"/1.pub"},
+	})
+	require.NoError(t, err)
+	updatedJSONWithUnknownData, err := os.ReadFile(policyPath)
+	require.NoError(t, err)
+	// Decode updatedJSONWithUnknownData so that this test does not depend on details of the encoding.
+	// To reduce noise in the constants below:
+	type a = []interface{}
+	type m = map[string]interface{}
+	var parsedUpdatedJSON m
+	err = json.Unmarshal(updatedJSONWithUnknownData, &parsedUpdatedJSON)
+	require.NoError(t, err)
+	assert.Equal(t, m{
+		"default": a{
+			m{
+				"type":          "this is unknown",
+				"unknown field": "should be preserved",
+			},
+		},
+		"transports": m{
+			"docker-daemon": m{
+				"": a{
+					m{
+						"type":            "this is unknown 2",
+						"unknown field 2": "should be preserved 2",
+					},
+				},
+			},
+			"docker": m{
+				"quay.io/innocuous": a{
+					m{
+						"type":    "signedBy",
+						"keyType": "GPGKeys",
+						"keyPath": "/1.pub",
+					},
+				},
+			},
+		},
+	}, parsedUpdatedJSON)
+}
+
+// xNewPRSignedByKeyPath is a wrapper for NewPRSignedByKeyPath which must not fail.
+func xNewPRSignedByKeyPath(t *testing.T, keyPath string, signedIdentity signature.PolicyReferenceMatch) signature.PolicyRequirement {
+	pr, err := signature.NewPRSignedByKeyPath(signature.SBKeyTypeGPGKeys, keyPath, signedIdentity)
+	require.NoError(t, err)
+	return pr
+}
+
+// xNewPRSignedByKeyPaths is a wrapper for NewPRSignedByKeyPaths which must not fail.
+func xNewPRSignedByKeyPaths(t *testing.T, keyPaths []string, signedIdentity signature.PolicyReferenceMatch) signature.PolicyRequirement {
+	pr, err := signature.NewPRSignedByKeyPaths(signature.SBKeyTypeGPGKeys, keyPaths, signedIdentity)
+	require.NoError(t, err)
+	return pr
+}
+
+// xNewPRSigstoreSignedKeyPath is a wrapper for NewPRSigstoreSignedKeyPath which must not fail.
+func xNewPRSigstoreSignedKeyPath(t *testing.T, keyPath string, signedIdentity signature.PolicyReferenceMatch) signature.PolicyRequirement {
+	pr, err := signature.NewPRSigstoreSignedKeyPath(keyPath, signedIdentity)
+	require.NoError(t, err)
+	return pr
+}
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
+}
diff --git a/pkg/trust/testdata/default.yaml b/pkg/trust/testdata/default.yaml
new file mode 100644
index 000000000..31bcd35ef
--- /dev/null
+++ b/pkg/trust/testdata/default.yaml
@@ -0,0 +1,25 @@
+# This is a default registries.d configuration file.  You may
+# add to this file or create additional files in registries.d/.
+#
+# lookaside: indicates a location that is read and write
+# lookaside-staging: indicates a location that is only for write
+#
+# lookaside and lookaside-staging take a value of the following:
+#   lookaside:  {schema}://location
+#
+# For reading signatures, schema may be http, https, or file.
+# For writing signatures, schema may only be file.
+
+# This is the default signature write location for docker registries.
+default-docker:
+#  lookaside: file:///var/lib/containers/sigstore
+  lookaside-staging: file:///var/lib/containers/sigstore
+
+# The 'docker' indicator here is the start of the configuration
+# for docker registries.
+#
+# docker:
+#
+#   privateregistry.com:
+#    lookaside: http://privateregistry.com/sigstore/
+#    lookaside-staging: /mnt/nfs/privateregistry/sigstore
diff --git a/pkg/trust/testdata/quay.io.yaml b/pkg/trust/testdata/quay.io.yaml
new file mode 100644
index 000000000..80071596d
--- /dev/null
+++ b/pkg/trust/testdata/quay.io.yaml
@@ -0,0 +1,3 @@
+docker:
+     quay.io/multi-signed:
+         lookaside: https://quay.example.com/sigstore
diff --git a/pkg/trust/testdata/redhat.yaml b/pkg/trust/testdata/redhat.yaml
new file mode 100644
index 000000000..8e40a4174
--- /dev/null
+++ b/pkg/trust/testdata/redhat.yaml
@@ -0,0 +1,5 @@
+docker:
+     registry.redhat.io:
+         sigstore: https://registry.redhat.io/containers/sigstore
+     registry.access.redhat.com:
+         sigstore: https://registry.redhat.io/containers/sigstore
diff --git a/pkg/trust/trust.go b/pkg/trust/trust.go
index 663a1b5e2..07d144bc1 100644
--- a/pkg/trust/trust.go
+++ b/pkg/trust/trust.go
@@ -1,243 +1,127 @@
 package trust
 
 import (
-	"bufio"
-	"bytes"
-	"encoding/base64"
-	"encoding/json"
 	"fmt"
-	"io/ioutil"
-	"os"
-	"os/exec"
-	"path/filepath"
+	"sort"
 	"strings"
-
-	"github.com/containers/image/v5/types"
-	"github.com/docker/docker/pkg/homedir"
-	"github.com/ghodss/yaml"
-	"github.com/sirupsen/logrus"
 )
 
-// PolicyContent struct for policy.json file
-type PolicyContent struct {
-	Default    []RepoContent     `json:"default"`
-	Transports TransportsContent `json:"transports,omitempty"`
-}
-
-// RepoContent struct used under each repo
-type RepoContent struct {
-	Type           string          `json:"type"`
-	KeyType        string          `json:"keyType,omitempty"`
-	KeyPath        string          `json:"keyPath,omitempty"`
-	KeyData        string          `json:"keyData,omitempty"`
-	SignedIdentity json.RawMessage `json:"signedIdentity,omitempty"`
-}
-
-// RepoMap map repo name to policycontent for each repo
-type RepoMap map[string][]RepoContent
-
-// TransportsContent struct for content under "transports"
-type TransportsContent map[string]RepoMap
-
-// 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"`
+// Policy describes a basic trust policy configuration
+type Policy struct {
+	Transport      string   `json:"transport"`
+	Name           string   `json:"name,omitempty"`
+	RepoName       string   `json:"repo_name,omitempty"`
+	Keys           []string `json:"keys,omitempty"`
+	SignatureStore string   `json:"sigstore,omitempty"`
+	Type           string   `json:"type"`
+	GPGId          string   `json:"gpg_id,omitempty"`
 }
 
-// RegistryNamespace defines lookaside locations for a single namespace.
-type RegistryNamespace struct {
-	SigStore        string `json:"sigstore"`         // For reading, and if SigStoreStaging is not present, for writing.
-	SigStoreStaging string `json:"sigstore-staging"` // For writing only.
+// PolicyDescription returns an user-focused description of the policy in policyPath and registries.d data from registriesDirPath.
+func PolicyDescription(policyPath, registriesDirPath string) ([]*Policy, error) {
+	return policyDescriptionWithGPGIDReader(policyPath, registriesDirPath, getGPGIdFromKeyPath)
 }
 
-// ShowOutput keep the fields for image trust show command
-type ShowOutput struct {
-	Repo      string
-	Trusttype string
-	GPGid     string
-	Sigstore  string
-}
-
-// 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")
-
-// DefaultPolicyPath returns a path to the default policy of the system.
-func DefaultPolicyPath(sys *types.SystemContext) string {
-	systemDefaultPolicyPath := "/etc/containers/policy.json"
-	if sys != nil {
-		if sys.SignaturePolicyPath != "" {
-			return sys.SignaturePolicyPath
-		}
-		if sys.RootForImplicitAbsolutePaths != "" {
-			return filepath.Join(sys.RootForImplicitAbsolutePaths, systemDefaultPolicyPath)
-		}
-	}
-	return systemDefaultPolicyPath
-}
-
-// 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
+// policyDescriptionWithGPGIDReader is PolicyDescription with a gpgIDReader parameter. It exists only to make testing easier.
+func policyDescriptionWithGPGIDReader(policyPath, registriesDirPath string, idReader gpgIDReader) ([]*Policy, error) {
+	policyContentStruct, err := getPolicy(policyPath)
+	if err != nil {
+		return nil, fmt.Errorf("could not read trust policies: %w", err)
 	}
-	if sys != nil && sys.RootForImplicitAbsolutePaths != "" {
-		return filepath.Join(sys.RootForImplicitAbsolutePaths, systemRegistriesDirPath)
+	res, err := getPolicyShowOutput(policyContentStruct, registriesDirPath, idReader)
+	if err != nil {
+		return nil, fmt.Errorf("could not show trust policies: %w", err)
 	}
-
-	return systemRegistriesDirPath
+	return res, nil
 }
 
-// LoadAndMergeConfig loads configuration files in dirPath
-func LoadAndMergeConfig(dirPath string) (*RegistryConfiguration, error) {
-	mergedConfig := RegistryConfiguration{Docker: map[string]RegistryNamespace{}}
-	dockerDefaultMergedFrom := ""
-	nsMergedFrom := map[string]string{}
+func getPolicyShowOutput(policyContentStruct policyContent, systemRegistriesDirPath string, idReader gpgIDReader) ([]*Policy, error) {
+	var output []*Policy
 
-	dir, err := os.Open(dirPath)
+	registryConfigs, err := loadAndMergeConfig(systemRegistriesDirPath)
 	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
+
+	if len(policyContentStruct.Default) > 0 {
+		template := Policy{
+			Transport: "all",
+			Name:      "* (default)",
+			RepoName:  "default",
 		}
-		var config RegistryConfiguration
-		err = yaml.Unmarshal(configBytes, &config)
-		if err != nil {
-			return nil, fmt.Errorf("error parsing %s: %w", configPath, err)
+		output = append(output, descriptionsOfPolicyRequirements(policyContentStruct.Default, template, registryConfigs, "", idReader)...)
+	}
+	// FIXME: This should use x/exp/maps.Keys after we update to Go 1.18.
+	transports := []string{}
+	for t := range policyContentStruct.Transports {
+		transports = append(transports, t)
+	}
+	sort.Strings(transports)
+	for _, transport := range transports {
+		transval := policyContentStruct.Transports[transport]
+		if transport == "docker" {
+			transport = "repository"
 		}
-		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
+
+		// FIXME: This should use x/exp/maps.Keys after we update to Go 1.18.
+		scopes := []string{}
+		for s := range transval {
+			scopes = append(scopes, s)
 		}
-		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)
+		sort.Strings(scopes)
+		for _, repo := range scopes {
+			repoval := transval[repo]
+			template := Policy{
+				Transport: transport,
+				Name:      repo,
+				RepoName:  repo,
 			}
-			mergedConfig.Docker[nsName] = nsConfig
-			nsMergedFrom[nsName] = configPath
+			output = append(output, descriptionsOfPolicyRequirements(repoval, template, registryConfigs, repo, idReader)...)
 		}
 	}
-	return &mergedConfig, nil
+	return output, nil
 }
 
-// HaveMatchRegistry checks if trust settings for the registry have been configured in yaml file
-func HaveMatchRegistry(key string, registryConfigs *RegistryConfiguration) *RegistryNamespace {
-	searchKey := key
-	if !strings.Contains(searchKey, "/") {
-		val, exists := registryConfigs.Docker[searchKey]
-		if exists {
-			return &val
-		}
-	}
-	for range strings.Split(key, "/") {
-		val, exists := registryConfigs.Docker[searchKey]
-		if exists {
-			return &val
-		}
-		if strings.Contains(searchKey, "/") {
-			searchKey = searchKey[:strings.LastIndex(searchKey, "/")]
+// descriptionsOfPolicyRequirements turns reqs into user-readable policy entries, with Transport/Name/Reponame coming from template, potentially looking up scope (which may be "") in registryConfigs.
+func descriptionsOfPolicyRequirements(reqs []repoContent, template Policy, registryConfigs *registryConfiguration, scope string, idReader gpgIDReader) []*Policy {
+	res := []*Policy{}
+
+	var lookasidePath string
+	registryNamespace := registriesDConfigurationForScope(registryConfigs, scope)
+	if registryNamespace != nil {
+		if registryNamespace.Lookaside != "" {
+			lookasidePath = registryNamespace.Lookaside
+		} else { // incl. registryNamespace.SigStore == ""
+			lookasidePath = registryNamespace.SigStore
 		}
 	}
-	return registryConfigs.DefaultDocker
-}
-
-// CreateTmpFile creates a temp file under dir and writes the content into it
-func CreateTmpFile(dir, pattern string, content []byte) (string, error) {
-	tmpfile, err := ioutil.TempFile(dir, pattern)
-	if err != nil {
-		return "", err
-	}
-	defer tmpfile.Close()
-
-	if _, err := tmpfile.Write(content); err != nil {
-		return "", err
-	}
-	return tmpfile.Name(), nil
-}
-
-// GetGPGIdFromKeyPath return user keyring from key path
-func GetGPGIdFromKeyPath(path string) []string {
-	cmd := exec.Command("gpg2", "--with-colons", path)
-	results, err := cmd.Output()
-	if err != nil {
-		logrus.Errorf("Getting key identity: %s", err)
-		return nil
-	}
-	return parseUids(results)
-}
 
-// GetGPGIdFromKeyData return user keyring from keydata
-func GetGPGIdFromKeyData(key string) []string {
-	decodeKey, err := base64.StdEncoding.DecodeString(key)
-	if err != nil {
-		logrus.Errorf("%s, error decoding key data", err)
-		return nil
-	}
-	tmpfileName, err := CreateTmpFile("", "", decodeKey)
-	if err != nil {
-		logrus.Errorf("Creating key date temp file %s", err)
-	}
-	defer os.Remove(tmpfileName)
-	return GetGPGIdFromKeyPath(tmpfileName)
-}
+	for _, repoele := range reqs {
+		entry := template
+		entry.Type = trustTypeDescription(repoele.Type)
 
-func parseUids(colonDelimitKeys []byte) []string {
-	var parseduids []string
-	scanner := bufio.NewScanner(bytes.NewReader(colonDelimitKeys))
-	for scanner.Scan() {
-		line := scanner.Text()
-		if strings.HasPrefix(line, "uid:") || strings.HasPrefix(line, "pub:") {
-			uid := strings.Split(line, ":")[9]
-			if uid == "" {
-				continue
+		var gpgIDString string
+		switch repoele.Type {
+		case "signedBy":
+			uids := []string{}
+			if len(repoele.KeyPath) > 0 {
+				uids = append(uids, idReader(repoele.KeyPath)...)
 			}
-			parseduid := uid
-			if strings.Contains(uid, "<") && strings.Contains(uid, ">") {
-				parseduid = strings.SplitN(strings.SplitAfterN(uid, "<", 2)[1], ">", 2)[0]
+			for _, path := range repoele.KeyPaths {
+				uids = append(uids, idReader(path)...)
 			}
-			parseduids = append(parseduids, parseduid)
+			if len(repoele.KeyData) > 0 {
+				uids = append(uids, getGPGIdFromKeyData(idReader, repoele.KeyData)...)
+			}
+			gpgIDString = strings.Join(uids, ", ")
+
+		case "sigstoreSigned":
+			gpgIDString = "N/A" // We could potentially return key fingerprints here, but they would not be _GPG_ fingerprints.
 		}
+		entry.GPGId = gpgIDString
+		entry.SignatureStore = lookasidePath // We do this even for sigstoreSigned and things like type: reject, to show that the sigstore is being read.
+		res = append(res, &entry)
 	}
-	return parseduids
-}
 
-// GetPolicy parse policy.json into PolicyContent struct
-func GetPolicy(policyPath string) (PolicyContent, error) {
-	var policyContentStruct PolicyContent
-	policyContent, err := ioutil.ReadFile(policyPath)
-	if err != nil {
-		return policyContentStruct, fmt.Errorf("unable to read policy file: %w", err)
-	}
-	if err := json.Unmarshal(policyContent, &policyContentStruct); err != nil {
-		return policyContentStruct, fmt.Errorf("could not parse trust policies from %s: %w", policyPath, err)
-	}
-	return policyContentStruct, nil
+	return res
 }
diff --git a/pkg/trust/trust_test.go b/pkg/trust/trust_test.go
new file mode 100644
index 000000000..22b780fc9
--- /dev/null
+++ b/pkg/trust/trust_test.go
@@ -0,0 +1,376 @@
+package trust
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/containers/image/v5/signature"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPolicyDescription(t *testing.T) {
+	tempDir := t.TempDir()
+	policyPath := filepath.Join(tempDir, "policy.json")
+
+	// Override getGPGIdFromKeyPath because we don't want to bother with (and spend the unit-test time on) generating valid GPG keys, and running the real GPG binary.
+	// Instead of reading the files at all, just expect file names like /id1,id2,...,idN.pub
+	idReader := func(keyPath string) []string {
+		require.True(t, strings.HasPrefix(keyPath, "/"))
+		require.True(t, strings.HasSuffix(keyPath, ".pub"))
+		return strings.Split(keyPath[1:len(keyPath)-4], ",")
+	}
+
+	for _, c := range []struct {
+		policy   *signature.Policy
+		expected []*Policy
+	}{
+		{
+			&signature.Policy{
+				Default: signature.PolicyRequirements{
+					signature.NewPRReject(),
+				},
+				Transports: map[string]signature.PolicyTransportScopes{
+					"docker": {
+						"quay.io/accepted": {
+							signature.NewPRInsecureAcceptAnything(),
+						},
+						"registry.redhat.io": {
+							xNewPRSignedByKeyPath(t, "/redhat.pub", signature.NewPRMMatchRepoDigestOrExact()),
+						},
+						"registry.access.redhat.com": {
+							xNewPRSignedByKeyPaths(t, []string{"/redhat.pub", "/redhat-beta.pub"}, signature.NewPRMMatchRepoDigestOrExact()),
+						},
+						"quay.io/multi-signed": {
+							xNewPRSignedByKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+							xNewPRSignedByKeyPath(t, "/2,3.pub", signature.NewPRMMatchRepoDigestOrExact()),
+						},
+						"quay.io/sigstore-signed": {
+							xNewPRSigstoreSignedKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+							xNewPRSigstoreSignedKeyPath(t, "/2.pub", signature.NewPRMMatchRepoDigestOrExact()),
+						},
+					},
+				},
+			},
+			[]*Policy{
+				{
+					Transport: "all",
+					Name:      "* (default)",
+					RepoName:  "default",
+					Type:      "reject",
+				},
+				{
+					Transport: "repository",
+					Name:      "quay.io/accepted",
+					RepoName:  "quay.io/accepted",
+					Type:      "accept",
+				},
+				{
+					Transport:      "repository",
+					Name:           "quay.io/multi-signed",
+					RepoName:       "quay.io/multi-signed",
+					Type:           "signed",
+					SignatureStore: "https://quay.example.com/sigstore",
+					GPGId:          "1",
+				},
+				{
+					Transport:      "repository",
+					Name:           "quay.io/multi-signed",
+					RepoName:       "quay.io/multi-signed",
+					Type:           "signed",
+					SignatureStore: "https://quay.example.com/sigstore",
+					GPGId:          "2, 3",
+				},
+				{
+					Transport:      "repository",
+					Name:           "quay.io/sigstore-signed",
+					RepoName:       "quay.io/sigstore-signed",
+					Type:           "sigstoreSigned",
+					SignatureStore: "",
+					GPGId:          "N/A",
+				},
+				{
+					Transport:      "repository",
+					Name:           "quay.io/sigstore-signed",
+					RepoName:       "quay.io/sigstore-signed",
+					Type:           "sigstoreSigned",
+					SignatureStore: "",
+					GPGId:          "N/A",
+				},
+				{
+					Transport:      "repository",
+					Name:           "registry.access.redhat.com",
+					RepoName:       "registry.access.redhat.com",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat, redhat-beta",
+				}, {
+					Transport:      "repository",
+					Name:           "registry.redhat.io",
+					RepoName:       "registry.redhat.io",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat",
+				},
+			},
+		},
+		{
+			&signature.Policy{
+				Default: signature.PolicyRequirements{
+					xNewPRSignedByKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+					xNewPRSignedByKeyPath(t, "/2,3.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				},
+			},
+			[]*Policy{
+				{
+					Transport:      "all",
+					Name:           "* (default)",
+					RepoName:       "default",
+					Type:           "signed",
+					SignatureStore: "",
+					GPGId:          "1",
+				},
+				{
+					Transport:      "all",
+					Name:           "* (default)",
+					RepoName:       "default",
+					Type:           "signed",
+					SignatureStore: "",
+					GPGId:          "2, 3",
+				},
+			},
+		},
+	} {
+		policyJSON, err := json.Marshal(c.policy)
+		require.NoError(t, err)
+		err = os.WriteFile(policyPath, policyJSON, 0600)
+		require.NoError(t, err)
+
+		res, err := policyDescriptionWithGPGIDReader(policyPath, "./testdata", idReader)
+		require.NoError(t, err)
+		assert.Equal(t, c.expected, res)
+	}
+}
+
+func TestDescriptionsOfPolicyRequirements(t *testing.T) {
+	// Override getGPGIdFromKeyPath because we don't want to bother with (and spend the unit-test time on) generating valid GPG keys, and running the real GPG binary.
+	// Instead of reading the files at all, just expect file names like /id1,id2,...,idN.pub
+	idReader := func(keyPath string) []string {
+		require.True(t, strings.HasPrefix(keyPath, "/"))
+		require.True(t, strings.HasSuffix(keyPath, ".pub"))
+		return strings.Split(keyPath[1:len(keyPath)-4], ",")
+	}
+
+	template := Policy{
+		Transport: "transport",
+		Name:      "name",
+		RepoName:  "repoName",
+	}
+	registryConfigs, err := loadAndMergeConfig("./testdata")
+	require.NoError(t, err)
+
+	for _, c := range []struct {
+		scope    string
+		reqs     signature.PolicyRequirements
+		expected []*Policy
+	}{
+		{
+			"",
+			signature.PolicyRequirements{
+				signature.NewPRReject(),
+			},
+			[]*Policy{
+				{
+					Transport: "transport",
+					Name:      "name",
+					RepoName:  "repoName",
+					Type:      "reject",
+				},
+			},
+		},
+		{
+			"quay.io/accepted",
+			signature.PolicyRequirements{
+				signature.NewPRInsecureAcceptAnything(),
+			},
+			[]*Policy{
+				{
+					Transport: "transport",
+					Name:      "name",
+					RepoName:  "repoName",
+					Type:      "accept",
+				},
+			},
+		},
+		{
+			"registry.redhat.io",
+			signature.PolicyRequirements{
+				xNewPRSignedByKeyPath(t, "/redhat.pub", signature.NewPRMMatchRepoDigestOrExact()),
+			},
+			[]*Policy{
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat",
+				},
+			},
+		},
+		{
+			"registry.access.redhat.com",
+			signature.PolicyRequirements{
+				xNewPRSignedByKeyPaths(t, []string{"/redhat.pub", "/redhat-beta.pub"}, signature.NewPRMMatchRepoDigestOrExact()),
+			},
+			[]*Policy{
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat, redhat-beta",
+				},
+			},
+		},
+		{
+			"quay.io/multi-signed",
+			signature.PolicyRequirements{
+				xNewPRSignedByKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSignedByKeyPath(t, "/2,3.pub", signature.NewPRMMatchRepoDigestOrExact()),
+			},
+			[]*Policy{
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://quay.example.com/sigstore",
+					GPGId:          "1",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://quay.example.com/sigstore",
+					GPGId:          "2, 3",
+				},
+			},
+		}, {
+			"quay.io/sigstore-signed",
+			signature.PolicyRequirements{
+				xNewPRSigstoreSignedKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSigstoreSignedKeyPath(t, "/2.pub", signature.NewPRMMatchRepoDigestOrExact()),
+			},
+			[]*Policy{
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "sigstoreSigned",
+					SignatureStore: "",
+					GPGId:          "N/A",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "sigstoreSigned",
+					SignatureStore: "",
+					GPGId:          "N/A",
+				},
+			},
+		},
+		{ // Multiple kinds of requirements are represented individually.
+			"registry.redhat.io",
+			signature.PolicyRequirements{
+				signature.NewPRReject(),
+				signature.NewPRInsecureAcceptAnything(),
+				xNewPRSignedByKeyPath(t, "/redhat.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSignedByKeyPaths(t, []string{"/redhat.pub", "/redhat-beta.pub"}, signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSignedByKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSignedByKeyPath(t, "/2,3.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSigstoreSignedKeyPath(t, "/1.pub", signature.NewPRMMatchRepoDigestOrExact()),
+				xNewPRSigstoreSignedKeyPath(t, "/2.pub", signature.NewPRMMatchRepoDigestOrExact()),
+			},
+			[]*Policy{
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					Type:           "reject",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					Type:           "accept",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "redhat, redhat-beta",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "1",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "signed",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "2, 3",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "sigstoreSigned",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "N/A",
+				},
+				{
+					Transport:      "transport",
+					Name:           "name",
+					RepoName:       "repoName",
+					Type:           "sigstoreSigned",
+					SignatureStore: "https://registry.redhat.io/containers/sigstore",
+					GPGId:          "N/A",
+				},
+			},
+		},
+	} {
+		reqsJSON, err := json.Marshal(c.reqs)
+		require.NoError(t, err)
+		var parsedRegs []repoContent
+		err = json.Unmarshal(reqsJSON, &parsedRegs)
+		require.NoError(t, err)
+
+		res := descriptionsOfPolicyRequirements(parsedRegs, template, registryConfigs, c.scope, idReader)
+		assert.Equal(t, c.expected, res)
+	}
+}