Add proper mirror support (#74)

* Add rewrite support and fix existing tests

* Add unit tests for policy matching

* Compile regexes up front and store policies in map

* Add test for verify flow with mirror

* Rename ImageName -> ResolvedName

And only set it when necessary

* Rename Rewrite -> Replacement

but keep it as rewrite in the yaml

pkg/attest/sign_test.go

@@ -22,12 +22,13 @@ import (
 )
 
 var (
-	UnsignedTestImage = filepath.Join("..", "..", "test", "testdata", "unsigned-test-image")
-	NoProvenanceImage = filepath.Join("..", "..", "test", "testdata", "no-provenance-image")
-	PassPolicyDir     = filepath.Join("..", "..", "test", "testdata", "local-policy-pass")
-	PassNoTLPolicyDir = filepath.Join("..", "..", "test", "testdata", "local-policy-no-tl")
-	FailPolicyDir     = filepath.Join("..", "..", "test", "testdata", "local-policy-fail")
-	TestTempDir       = "attest-sign-test"
+	UnsignedTestImage   = filepath.Join("..", "..", "test", "testdata", "unsigned-test-image")
+	NoProvenanceImage   = filepath.Join("..", "..", "test", "testdata", "no-provenance-image")
+	PassPolicyDir       = filepath.Join("..", "..", "test", "testdata", "local-policy-pass")
+	PassMirrorPolicyDir = filepath.Join("..", "..", "test", "testdata", "local-policy-mirror")
+	PassNoTLPolicyDir   = filepath.Join("..", "..", "test", "testdata", "local-policy-no-tl")
+	FailPolicyDir       = filepath.Join("..", "..", "test", "testdata", "local-policy-fail")
+	TestTempDir         = "attest-sign-test"
 )
 
 func TestSignVerifyOCILayout(t *testing.T) {

pkg/attest/verify.go

@@ -3,8 +3,10 @@ package attest
 import (
 	"context"
 	"fmt"
+	"strings"
 	"time"
 
+	"github.com/distribution/reference"
 	"github.com/docker/attest/pkg/attestation"
 	"github.com/docker/attest/pkg/config"
 	"github.com/docker/attest/pkg/oci"
@@ -36,12 +38,12 @@ func Verify(ctx context.Context, src *oci.ImageSpec, opts *policy.PolicyOptions)
 	}
 	// this is overriding the mapping with a referrers config. Useful for testing if nothing else
 	if opts.ReferrersRepo != "" {
-		pctx.Mapping.Attestations = &config.ReferrersConfig{
+		pctx.Mapping.Attestations = &config.AttestationConfig{
 			Repo:  opts.ReferrersRepo,
 			Style: config.AttestationStyleReferrers,
 		}
 	} else if opts.AttestationStyle == config.AttestationStyleAttached {
-		pctx.Mapping.Attestations = &config.ReferrersConfig{
+		pctx.Mapping.Attestations = &config.AttestationConfig{
 			Repo:  opts.ReferrersRepo,
 			Style: config.AttestationStyleAttached,
 		}
@@ -122,6 +124,19 @@ func VerifyAttestations(ctx context.Context, resolver oci.AttestationResolver, p
 	if err != nil {
 		return nil, err
 	}
+
+	if pctx.ResolvedName != "" {
+		// this means the name we have is not the one we want to use for policy evaluation
+		// so we need to replace it with the one we resolved during policy resolution.
+		// this can happen if the name is an alias for another image, e.g. if it is a mirror
+		ref, err := reference.ParseNormalizedNamed(name)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse image name: %w", err)
+		}
+		oldName := ref.Name()
+		name = strings.Replace(name, oldName, pctx.ResolvedName, 1)
+	}
+
 	purl, canonical, err := oci.RefToPURL(name, platform)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert ref to purl: %w", err)

pkg/attest/verify_test.go

@@ -59,7 +59,7 @@ func TestVerifyAttestations(t *testing.T) {
 			}
 
 			ctx := policy.WithPolicyEvaluator(context.Background(), &mockPE)
-			_, err := VerifyAttestations(ctx, resolver, nil)
+			_, err := VerifyAttestations(ctx, resolver, &policy.Policy{ResolvedName: ""})
 			if tc.expectedError != nil {
 				if assert.Error(t, err) {
 					assert.Equal(t, tc.expectedError.Error(), err.Error())
@@ -189,22 +189,24 @@ func TestVerificationFailure(t *testing.T) {
 	assert.Equal(t, "https://docker.com/official/policy/v0.1", attestationPredicate.Policy.URI)
 }
 
-// test signing without a TL entry
-func TestSignVerifyNoTL(t *testing.T) {
+func TestSignVerify(t *testing.T) {
 	ctx, signer := test.Setup(t)
 	ctx = policy.WithPolicyEvaluator(ctx, policy.NewRegoEvaluator(true))
 	// setup an image with signed attestations
 	outputLayout := test.CreateTempDir(t, "", TestTempDir)
 
 	testCases := []struct {
-		name      string
-		signTL    bool
-		policyDir string
-		success   bool
+		name        string
+		signTL      bool
+		policyDir   string
+		imageName   string
+		expectError bool
 	}{
-		{name: "happy path", signTL: true, policyDir: PassNoTLPolicyDir, success: true},
-		{name: "sign tl, verify no tl", signTL: true, policyDir: PassPolicyDir, success: false},
-		{name: "no tl", signTL: false, policyDir: PassPolicyDir, success: false},
+		{name: "happy path", signTL: true, policyDir: PassNoTLPolicyDir},
+		{name: "sign tl, verify no tl", signTL: true, policyDir: PassPolicyDir},
+		{name: "no tl", signTL: false, policyDir: PassPolicyDir},
+		{name: "mirror", signTL: true, policyDir: PassMirrorPolicyDir, imageName: "mirror.org/library/test-image:test"},
+		{name: "mirror no match", signTL: true, policyDir: PassMirrorPolicyDir, imageName: "incorrect.org/library/test-image:test", expectError: true},
 	}
 
 	attIdx, err := oci.IndexFromPath(UnsignedTestImage)
@@ -222,13 +224,18 @@ func TestSignVerifyNoTL(t *testing.T) {
 			signedIndex := attIdx.Index
 			signedIndex, err = attestation.AddImagesToIndex(signedIndex, signedManifests)
 			require.NoError(t, err)
+
+			imageName := tc.imageName
+			if imageName == "" {
+				imageName = attIdx.Name
+			}
 			// output signed attestations
 			idx := v1.ImageIndex(empty.Index)
 			idx = mutate.AppendManifests(idx, mutate.IndexAddendum{
 				Add: signedIndex,
 				Descriptor: v1.Descriptor{
 					Annotations: map[string]string{
-						oci.OciReferenceTarget: attIdx.Name,
+						oci.OciReferenceTarget: imageName,
 					},
 				},
 			})
@@ -241,8 +248,17 @@ func TestSignVerifyNoTL(t *testing.T) {
 			src, err := oci.ParseImageSpec("oci://"+outputLayout, oci.WithPlatform(LinuxAMD64))
 			require.NoError(t, err)
 			results, err := Verify(ctx, src, policyOpts)
+			if tc.expectError {
+				require.Error(t, err)
+				return
+			}
 			require.NoError(t, err)
 			assert.Equal(t, OutcomeSuccess, results.Outcome)
+			platform, err := oci.ParsePlatform(LinuxAMD64)
+			require.NoError(t, err)
+			expectedPURL, _, err := oci.RefToPURL(attIdx.Name, platform)
+			require.NoError(t, err)
+			assert.Equal(t, expectedPURL, results.Input.Purl)
 		})
 	}
 }

pkg/attestation/referrers_test.go

@@ -37,6 +37,7 @@ func TestAttestationReferenceTypes(t *testing.T) {
 	ctx = policy.WithPolicyEvaluator(ctx, policy.NewRegoEvaluator(true))
 	platforms := []string{"linux/amd64", "linux/arm64"}
 	for _, tc := range []struct {
+		name              string
 		server            *httptest.Server
 		referrersServer   *httptest.Server
 		skipSubject       bool
@@ -44,46 +45,53 @@ func TestAttestationReferenceTypes(t *testing.T) {
 		referrersRepo     string
 		attestationSource config.AttestationStyle
 		expectFailure     bool
-		policyDir         string
 	}{
 		{
+			name:   "referrers support, defaults",
 			server: httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 		},
 		{
+			name:   "no referrers support",
 			server: httptest.NewServer(registry.New()),
 		},
 		{
+			name:              "attached attestations",
 			server:            httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			skipSubject:       true,
 			attestationSource: config.AttestationStyleAttached,
 		},
 		{
+			name:      "use digest",
 			server:    httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			useDigest: true,
 		},
 		{
+			name:              "attached attestations, referrers repo (mismatched args)",
 			server:            httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			expectFailure:     true, //mismatched args
 			attestationSource: config.AttestationStyleAttached,
 			referrersRepo:     "referrers",
 		},
 		{
+			name:              "referrers attestations, referrers repo (no policy)",
 			server:            httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			expectFailure:     true, // no policy
 			attestationSource: config.AttestationStyleReferrers,
 			referrersRepo:     "referrers",
 		},
 		{
+			name:              "referrers attestations",
 			server:            httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			attestationSource: config.AttestationStyleReferrers,
 		},
 		{
+			name:              "referrers attestations, no referrers support on server",
 			server:            httptest.NewServer(registry.New(registry.WithReferrersSupport(false))),
 			attestationSource: config.AttestationStyleReferrers,
 			referrersServer:   httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 		},
 	} {
-		t.Run(fmt.Sprint(tc), func(t *testing.T) {
+		t.Run(tc.name, func(t *testing.T) {
 			s := tc.server
 			defer s.Close()
 
@@ -111,6 +119,7 @@ func TestAttestationReferenceTypes(t *testing.T) {
 				signedManifests, err := attest.SignStatements(ctx, attIdx.Index, signer, opts)
 				require.NoError(t, err)
 				err = mirror.PushIndexToRegistry(attIdx.Index, indexName)
+				require.NoError(t, err)
 				for _, img := range signedManifests {
 					err = mirror.PushImageToRegistry(img.Attestation.Image, fmt.Sprintf("%s:tag-does-not-matter", repo))
 					require.NoError(t, err)
@@ -142,9 +151,6 @@ func TestAttestationReferenceTypes(t *testing.T) {
 				policyOpts := &policy.PolicyOptions{
 					LocalPolicyDir: LocalPolicy,
 				}
-				if tc.policyDir != "" {
-					policyOpts.LocalPolicyDir = tc.policyDir
-				}
 
 				if tc.referrersRepo != "" {
 					policyOpts.ReferrersRepo = tc.referrersRepo
@@ -192,65 +198,70 @@ func TestReferencesInDifferentRepo(t *testing.T) {
 	ctx, signer := test.Setup(t)
 	repoName := "repo"
 	for _, tc := range []struct {
+		name      string
 		server    *httptest.Server
 		refServer *httptest.Server
 	}{
 		{
+			name:      "referrers support",
 			server:    httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 			refServer: httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 		},
 		{
+			name:      "no referrers support",
 			server:    httptest.NewServer(registry.New()),
 			refServer: httptest.NewServer(registry.New(registry.WithReferrersSupport(true))),
 		},
 	} {
-		server := tc.server
-		defer server.Close()
-		serverUrl, err := url.Parse(server.URL)
-		require.NoError(t, err)
-
-		refServer := tc.refServer
-		defer refServer.Close()
-		refServerUrl, err := url.Parse(refServer.URL)
-		require.NoError(t, err)
-
-		opts := &attestation.SigningOptions{
-			Replace: true,
-			SkipTL:  true,
-		}
-		attIdx, err := oci.IndexFromPath(UnsignedTestImage)
-		require.NoError(t, err)
-
-		indexName := fmt.Sprintf("%s/%s:latest", serverUrl.Host, repoName)
-		err = mirror.PushIndexToRegistry(attIdx.Index, indexName)
-		require.NoError(t, err)
-
-		signedManifests, err := attest.SignStatements(ctx, attIdx.Index, signer, opts)
-		require.NoError(t, err)
-
-		// push signed attestation image to the ref server
-		for _, img := range signedManifests {
-			// push references using subject-digest.att convention
-			err = mirror.PushImageToRegistry(img.Attestation.Image, fmt.Sprintf("%s/%s:tag-does-not-matter", refServerUrl.Host, repoName))
+		t.Run(tc.name, func(t *testing.T) {
+			server := tc.server
+			defer server.Close()
+			serverUrl, err := url.Parse(server.URL)
 			require.NoError(t, err)
-		}
-		mfs2, err := attIdx.Index.IndexManifest()
-		require.NoError(t, err)
-		for _, mf := range mfs2.Manifests {
-			//skip signed/unsigned attestations
-			if mf.Annotations[attestation.DockerReferenceType] == attestation.AttestationManifestType {
-				continue
+
+			refServer := tc.refServer
+			defer refServer.Close()
+			refServerUrl, err := url.Parse(refServer.URL)
+			require.NoError(t, err)
+
+			opts := &attestation.SigningOptions{
+				Replace: true,
+				SkipTL:  true,
 			}
-			// can evaluate policy using referrers in a different repo
-			referencedImage := fmt.Sprintf("%s@%s", indexName, mf.Digest.String())
-			policyOpts := &policy.PolicyOptions{
-				LocalPolicyDir: PassPolicyDir,
+			attIdx, err := oci.IndexFromPath(UnsignedTestImage)
+			require.NoError(t, err)
+
+			indexName := fmt.Sprintf("%s/%s:latest", serverUrl.Host, repoName)
+			err = mirror.PushIndexToRegistry(attIdx.Index, indexName)
+			require.NoError(t, err)
+
+			signedManifests, err := attest.SignStatements(ctx, attIdx.Index, signer, opts)
+			require.NoError(t, err)
+
+			// push signed attestation image to the ref server
+			for _, img := range signedManifests {
+				// push references using subject-digest.att convention
+				err = mirror.PushImageToRegistry(img.Attestation.Image, fmt.Sprintf("%s/%s:tag-does-not-matter", refServerUrl.Host, repoName))
+				require.NoError(t, err)
 			}
-			src, err := oci.ParseImageSpec(referencedImage)
+			mfs2, err := attIdx.Index.IndexManifest()
 			require.NoError(t, err)
-			results, err := attest.Verify(ctx, src, policyOpts)
-			require.NoError(t, err)
-			assert.Equal(t, attest.OutcomeSuccess, results.Outcome)
-		}
+			for _, mf := range mfs2.Manifests {
+				//skip signed/unsigned attestations
+				if mf.Annotations[attestation.DockerReferenceType] == attestation.AttestationManifestType {
+					continue
+				}
+				// can evaluate policy using referrers in a different repo
+				referencedImage := fmt.Sprintf("%s@%s", indexName, mf.Digest.String())
+				policyOpts := &policy.PolicyOptions{
+					LocalPolicyDir: PassPolicyDir,
+				}
+				src, err := oci.ParseImageSpec(referencedImage)
+				require.NoError(t, err)
+				results, err := attest.Verify(ctx, src, policyOpts)
+				require.NoError(t, err)
+				assert.Equal(t, attest.OutcomeSuccess, results.Outcome)
+			}
+		})
 	}
 }

pkg/config/config.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 
 	"github.com/docker/attest/pkg/tuf"
 	goyaml "gopkg.in/yaml.v3"
@@ -17,7 +18,7 @@ func LoadLocalMappings(configDir string) (*PolicyMappings, error) {
 	if configDir == "" {
 		return nil, nil
 	}
-	mappings := &PolicyMappings{}
+	mappings := &policyMappingsFile{}
 	path := filepath.Join(configDir, MappingFilename)
 	mappingFile, err := os.ReadFile(path)
 	if err != nil {
@@ -27,7 +28,7 @@ func LoadLocalMappings(configDir string) (*PolicyMappings, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to unmarshal policy mapping file %s: %w", path, err)
 	}
-	return mappings, nil
+	return expandMappingFile(mappings)
 }
 
 func LoadTufMappings(tufClient tuf.TUFClient, localTargetsDir string) (*PolicyMappings, error) {
@@ -39,11 +40,38 @@ func LoadTufMappings(tufClient tuf.TUFClient, localTargetsDir string) (*PolicyMa
 	if err != nil {
 		return nil, fmt.Errorf("failed to download policy mapping file %s: %w", filename, err)
 	}
-	mappings := &PolicyMappings{}
+	mappings := &policyMappingsFile{}
 
 	err = goyaml.Unmarshal(fileContents, mappings)
 	if err != nil {
 		return nil, fmt.Errorf("failed to unmarshal policy mapping file %s: %w", filename, err)
 	}
-	return mappings, nil
+	return expandMappingFile(mappings)
+}
+
+func expandMappingFile(mappingFile *policyMappingsFile) (*PolicyMappings, error) {
+	policies := make(map[string]*PolicyMapping)
+	for _, policy := range mappingFile.Policies {
+		policies[policy.Id] = policy
+	}
+
+	var rules []*PolicyRule
+	for _, rule := range mappingFile.Rules {
+		r, err := regexp.Compile(rule.Pattern)
+		if err != nil {
+			return nil, err
+		}
+		rules = append(rules, &PolicyRule{
+			Pattern:     r,
+			PolicyId:    rule.PolicyId,
+			Replacement: rule.Replacement,
+		})
+	}
+
+	return &PolicyMappings{
+		Version:  mappingFile.Version,
+		Kind:     mappingFile.Kind,
+		Policies: policies,
+		Rules:    rules,
+	}, nil
 }

pkg/config/types.go

@@ -1,10 +1,25 @@
 package config
 
+import "regexp"
+
+type policyMappingsFile struct {
+	Version  string            `yaml:"version"`
+	Kind     string            `yaml:"kind"`
+	Policies []*PolicyMapping  `yaml:"policies"`
+	Rules    []*policyRuleFile `yaml:"rules"`
+}
+
+type policyRuleFile struct {
+	Pattern     string `yaml:"pattern"`
+	PolicyId    string `yaml:"policy-id"`
+	Replacement string `yaml:"rewrite"`
+}
+
 type PolicyMappings struct {
-	Version  string           `json:"version"`
-	Kind     string           `json:"kind"`
-	Policies []*PolicyMapping `json:"policies"`
-	Mirrors  []*PolicyMirror  `json:"mirrors"`
+	Version  string
+	Kind     string
+	Policies map[string]*PolicyMapping
+	Rules    []*PolicyRule
 }
 
 type AttestationStyle string
@@ -15,34 +30,23 @@ const (
 )
 
 type PolicyMapping struct {
-	Id           string              `json:"id"`
-	Description  string              `json:"description"`
-	Origin       *PolicyOrigin       `json:"origin"`
-	Files        []PolicyMappingFile `json:"files"`
-	Attestations *ReferrersConfig    `json:"attestations"`
+	Id           string              `yaml:"id"`
+	Description  string              `yaml:"description"`
+	Files        []PolicyMappingFile `yaml:"files"`
+	Attestations *AttestationConfig  `yaml:"attestations"`
 }
 
-type ReferrersConfig struct {
-	Style AttestationStyle `json:"style"`
-	Repo  string           `json:"repo"`
+type AttestationConfig struct {
+	Style AttestationStyle `yaml:"style"`
+	Repo  string           `yaml:"repo"`
 }
 
 type PolicyMappingFile struct {
-	Path string `json:"path"`
+	Path string `yaml:"path"`
 }
 
-type PolicyMirror struct {
-	PolicyId string     `yaml:"policy-id"`
-	Mirror   MirrorSpec `json:"mirror"`
-}
-
-type MirrorSpec struct {
-	Domains []string `json:"domains"`
-	Prefix  string   `json:"prefix"`
-}
-
-type PolicyOrigin struct {
-	Name   string `json:"name"`
-	Prefix string `json:"prefix"`
-	Domain string `json:"domain"`
+type PolicyRule struct {
+	Pattern     *regexp.Regexp
+	PolicyId    string
+	Replacement string
 }

pkg/policy/policy.go

@@ -6,15 +6,13 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"slices"
-	"strings"
 
 	"github.com/distribution/reference"
 	"github.com/docker/attest/pkg/config"
 	"github.com/docker/attest/pkg/oci"
 )
 
-func resolveLocalPolicy(opts *PolicyOptions, mapping *config.PolicyMapping) (*Policy, error) {
+func resolveLocalPolicy(opts *PolicyOptions, mapping *config.PolicyMapping, imageName string, matchedName string) (*Policy, error) {
 	if opts.LocalPolicyDir == "" {
 		return nil, fmt.Errorf("local policy dir not set")
 	}
@@ -35,10 +33,13 @@ func resolveLocalPolicy(opts *PolicyOptions, mapping *config.PolicyMapping) (*Po
 		InputFiles: files,
 		Mapping:    mapping,
 	}
+	if imageName != matchedName {
+		policy.ResolvedName = matchedName
+	}
 	return policy, nil
 }
 
-func resolveTufPolicy(opts *PolicyOptions, mapping *config.PolicyMapping) (*Policy, error) {
+func resolveTufPolicy(opts *PolicyOptions, mapping *config.PolicyMapping, imageName string, matchedName string) (*Policy, error) {
 	files := make([]*PolicyFile, 0, len(mapping.Files))
 	for _, f := range mapping.Files {
 		filename := f.Path
@@ -55,32 +56,68 @@ func resolveTufPolicy(opts *PolicyOptions, mapping *config.PolicyMapping) (*Poli
 		InputFiles: files,
 		Mapping:    mapping,
 	}
+	if imageName != matchedName {
+		policy.ResolvedName = matchedName
+	}
 	return policy, nil
 }
 
-func findPolicyMatch(named reference.Named, mappings *config.PolicyMappings) (*config.PolicyMapping, *config.PolicyMirror) {
-	if mappings != nil {
-		for _, mapping := range mappings.Policies {
-			if mapping.Origin.Domain == reference.Domain(named) &&
-				strings.HasPrefix(reference.Path(named), mapping.Origin.Prefix) {
-				return mapping, nil
-			}
-		}
-		// now search mirrors
-		for _, mirror := range mappings.Mirrors {
-			if (slices.Contains(mirror.Mirror.Domains, reference.Domain(named)) ||
-				slices.Contains(mirror.Mirror.Domains, "*")) &&
-				strings.HasPrefix(reference.Path(named), mirror.Mirror.Prefix) {
-				for _, mapping := range mappings.Policies {
-					if mapping.Id == mirror.PolicyId {
-						return mapping, nil
-					}
+type matchType string
+
+const (
+	matchTypePolicy        matchType = "policy"
+	matchTypeMatchNoPolicy matchType = "match_no_policy"
+	matchTypeNoMatch       matchType = "no_match"
+)
+
+type policyMatch struct {
+	matchType   matchType
+	policy      *config.PolicyMapping
+	rule        *config.PolicyRule
+	matchedName string
+}
+
+func findPolicyMatch(imageName string, mappings *config.PolicyMappings) (*policyMatch, error) {
+	if mappings == nil {
+		return &policyMatch{matchType: matchTypeNoMatch, matchedName: imageName}, nil
+	}
+	return findPolicyMatchImpl(imageName, mappings, make(map[*config.PolicyRule]bool))
+}
+
+func findPolicyMatchImpl(imageName string, mappings *config.PolicyMappings, matched map[*config.PolicyRule]bool) (*policyMatch, error) {
+	for _, rule := range mappings.Rules {
+		if rule.Pattern.MatchString(imageName) {
+			switch {
+			case rule.PolicyId == "" && rule.Replacement == "":
+				return nil, fmt.Errorf("rule %s has neither policy-id nor rewrite", rule.Pattern)
+			case rule.PolicyId != "" && rule.Replacement != "":
+				return nil, fmt.Errorf("rule %s has both policy-id and rewrite", rule.Pattern)
+			case rule.PolicyId != "":
+				policy := mappings.Policies[rule.PolicyId]
+				if policy != nil {
+					return &policyMatch{
+						matchType:   matchTypePolicy,
+						policy:      policy,
+						rule:        rule,
+						matchedName: imageName,
+					}, nil
 				}
-				return nil, mirror
+				return &policyMatch{
+					matchType:   matchTypeMatchNoPolicy,
+					rule:        rule,
+					matchedName: imageName,
+				}, nil
+			case rule.Replacement != "":
+				if matched[rule] {
+					return nil, fmt.Errorf("rewrite loop detected")
+				}
+				matched[rule] = true
+				imageName = rule.Pattern.ReplaceAllString(imageName, rule.Replacement)
+				return findPolicyMatchImpl(imageName, mappings, matched)
 			}
 		}
 	}
-	return nil, nil
+	return &policyMatch{matchType: matchTypeNoMatch, matchedName: imageName}, nil
 }
 
 func resolvePolicyById(opts *PolicyOptions) (*Policy, error) {
@@ -90,10 +127,9 @@ func resolvePolicyById(opts *PolicyOptions) (*Policy, error) {
 			return nil, fmt.Errorf("failed to load local policy mappings: %w", err)
 		}
 		if localMappings != nil {
-			for _, mapping := range localMappings.Policies {
-				if mapping.Id == opts.PolicyId {
-					return resolveLocalPolicy(opts, mapping)
-				}
+			policy := localMappings.Policies[opts.PolicyId]
+			if policy != nil {
+				return resolveLocalPolicy(opts, policy, "", "")
 			}
 		}
 
@@ -102,10 +138,9 @@ func resolvePolicyById(opts *PolicyOptions) (*Policy, error) {
 		if err != nil {
 			return nil, fmt.Errorf("failed to load tuf policy mappings by id: %w", err)
 		}
-		for _, mapping := range tufMappings.Policies {
-			if mapping.Id == opts.PolicyId {
-				return resolveTufPolicy(opts, mapping)
-			}
+		policy := tufMappings.Policies[opts.PolicyId]
+		if policy != nil {
+			return resolveTufPolicy(opts, policy, "", "")
 		}
 		return nil, fmt.Errorf("policy with id %s not found", opts.PolicyId)
 	}
@@ -124,7 +159,7 @@ func ResolvePolicy(ctx context.Context, detailsResolver oci.ImageDetailsResolver
 	if err != nil {
 		return nil, fmt.Errorf("failed to get image name: %w", err)
 	}
-	named, err := reference.ParseNormalizedNamed(imageName)
+	imageName, err = normalizeImageName(imageName)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse image name: %w", err)
 	}
@@ -132,9 +167,12 @@ func ResolvePolicy(ctx context.Context, detailsResolver oci.ImageDetailsResolver
 	if err != nil {
 		return nil, fmt.Errorf("failed to load local policy mappings: %w", err)
 	}
-	mapping, mirror := findPolicyMatch(named, localMappings)
-	if mapping != nil {
-		return resolveLocalPolicy(opts, mapping)
+	match, err := findPolicyMatch(imageName, localMappings)
+	if err != nil {
+		return nil, err
+	}
+	if match.matchType == matchTypePolicy {
+		return resolveLocalPolicy(opts, match.policy, imageName, match.matchedName)
 	}
 	// must check tuf
 	tufMappings, err := config.LoadTufMappings(opts.TufClient, opts.LocalTargetsDir)
@@ -143,20 +181,31 @@ func ResolvePolicy(ctx context.Context, detailsResolver oci.ImageDetailsResolver
 	}
 
 	// it's a mirror of a tuf policy
-	if mirror != nil {
+	if match.matchType == matchTypeMatchNoPolicy {
 		for _, mapping := range tufMappings.Policies {
-			if mapping.Id == mirror.PolicyId {
-				return resolveTufPolicy(opts, mapping)
+			if mapping.Id == match.rule.PolicyId {
+				return resolveTufPolicy(opts, mapping, imageName, match.matchedName)
 			}
 		}
 	}
 
 	// try to resolve a tuf policy directly
-	mapping, _ = findPolicyMatch(named, tufMappings)
-	if mapping == nil {
-		return nil, nil
+	match, err = findPolicyMatch(imageName, tufMappings)
+	if err != nil {
+		return nil, err
 	}
-	return resolveTufPolicy(opts, mapping)
+	if match.matchType == matchTypePolicy {
+		return resolveTufPolicy(opts, match.policy, imageName, match.matchedName)
+	}
+	return nil, nil
+}
+
+func normalizeImageName(imageName string) (string, error) {
+	named, err := reference.ParseNormalizedNamed(imageName)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse image name: %w", err)
+	}
+	return named.Name(), nil
 }
 
 func CreateImageDetailsResolver(imageSource *oci.ImageSpec) (oci.ImageDetailsResolver, error) {

pkg/policy/policy_match_test.go

@@ -0,0 +1,121 @@
+package policy
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/docker/attest/pkg/config"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFindPolicyMatch(t *testing.T) {
+	testCases := []struct {
+		name       string
+		imageName  string
+		mappingDir string
+
+		expectError       bool
+		expectedMatchType matchType
+		expectedPolicyID  string
+		expectedImageName string
+	}{
+		{
+			name:       "alpine",
+			mappingDir: "doi",
+			imageName:  "docker.io/library/alpine",
+
+			expectedMatchType: matchTypePolicy,
+			expectedPolicyID:  "docker-official-images",
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "no match",
+			mappingDir: "doi",
+			imageName:  "docker.io/something/else",
+
+			expectedMatchType: matchTypeNoMatch,
+			expectedImageName: "docker.io/something/else",
+		},
+		{
+			name:       "match, no policy",
+			mappingDir: "local",
+			imageName:  "docker.io/library/alpine",
+
+			expectedMatchType: matchTypeMatchNoPolicy,
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "simple rewrite",
+			mappingDir: "simple-rewrite",
+			imageName:  "mycoolmirror.org/library/alpine",
+
+			expectedMatchType: matchTypePolicy,
+			expectedPolicyID:  "docker-official-images",
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "rewrite no match",
+			mappingDir: "rewrite-to-no-match",
+			imageName:  "mycoolmirror.org/library/alpine",
+
+			expectedMatchType: matchTypeNoMatch,
+			expectedImageName: "badredirect.org/alpine",
+		},
+		{
+			name:       "rewrite to match, no policy",
+			mappingDir: "rewrite-to-local",
+			imageName:  "mycoolmirror.org/library/alpine",
+
+			expectedMatchType: matchTypeMatchNoPolicy,
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "multiple rewrites",
+			mappingDir: "rewrite-multiple",
+			imageName:  "myevencoolermirror.org/library/alpine",
+
+			expectedMatchType: matchTypePolicy,
+			expectedPolicyID:  "docker-official-images",
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "invalid rewrites",
+			mappingDir: "rewrite-invalid",
+			imageName:  "mycoolmirror.org/library/alpine",
+
+			expectError:       true,
+			expectedMatchType: matchTypePolicy,
+			expectedPolicyID:  "docker-official-images",
+			expectedImageName: "docker.io/library/alpine",
+		},
+		{
+			name:       "rewrite loop",
+			mappingDir: "rewrite-loop",
+			imageName:  "yin/alpine",
+
+			expectError: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			mappings, err := config.LoadLocalMappings(filepath.Join("testdata", "mappings", tc.mappingDir))
+			require.NoError(t, err)
+			match, err := findPolicyMatch(tc.imageName, mappings)
+			if tc.expectError {
+				require.Error(t, err)
+				// TODO: check error matches expected error message
+				return
+			}
+			require.NoError(t, err)
+			assert.Equal(t, tc.expectedMatchType, match.matchType)
+			if match.matchType == matchTypePolicy {
+				if assert.NotNil(t, match.policy) {
+					assert.Equal(t, tc.expectedPolicyID, match.policy.Id)
+				}
+			}
+			assert.Equal(t, tc.expectedImageName, match.matchedName)
+		})
+	}
+}

pkg/policy/policy_test.go

@@ -84,6 +84,7 @@ func TestRegoEvaluator_Evaluate(t *testing.T) {
 			src, err := oci.ParseImageSpec(imageName, oci.WithPlatform(platform.String()))
 			require.NoError(t, err)
 			resolver, err := policy.CreateImageDetailsResolver(src)
+			require.NoError(t, err)
 			policy, err := policy.ResolvePolicy(ctx, resolver, tc.policy)
 			if tc.errorStr != "" {
 				require.Error(t, err)
@@ -91,6 +92,7 @@ func TestRegoEvaluator_Evaluate(t *testing.T) {
 				return
 			}
 			require.NoErrorf(t, err, "failed to resolve policy")
+			require.NotNil(t, policy, "policy should not be nil")
 			result, err := re.Evaluate(ctx, tc.resolver, policy, input)
 			require.NoErrorf(t, err, "Evaluate failed")
 
@@ -107,8 +109,10 @@ func TestRegoEvaluator_Evaluate(t *testing.T) {
 func TestLoadingMappings(t *testing.T) {
 	policyMappings, err := config.LoadLocalMappings(filepath.Join("testdata", "mock-tuf-allow"))
 	require.NoError(t, err)
-	assert.Equal(t, len(policyMappings.Mirrors), 1)
-	for _, mirror := range policyMappings.Mirrors {
-		assert.Equal(t, "docker-official-images", mirror.PolicyId)
+	assert.Equal(t, len(policyMappings.Rules), 3)
+	for _, mirror := range policyMappings.Rules {
+		if mirror.PolicyId != "" {
+			assert.Equal(t, "docker-official-images", mirror.PolicyId)
+		}
 	}
 }

pkg/policy/testdata/mappings/doi/mapping.yaml

@@ -0,0 +1,10 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images

pkg/policy/testdata/mappings/local/mapping.yaml

@@ -0,0 +1,10 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: local-policy
+    description: Local Policy
+    files:
+      - path: local-policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images # note this policy does not exist in this file

pkg/policy/testdata/mappings/rewrite-invalid/mapping.yaml

@@ -0,0 +1,13 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "^mycoolmirror[.]org/library/(.*)$"
+    rewrite: "docker.io/library/$1"
+    policy-id: docker-official-images # invalid to specify both rewrite and policy-id

pkg/policy/testdata/mappings/rewrite-loop/mapping.yaml

@@ -0,0 +1,14 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "^yin/(.*)$"
+    rewrite: "yang/$1"
+  - pattern: "^yang/(.*)$"
+    rewrite: "yin/$1"

pkg/policy/testdata/mappings/rewrite-multiple/mapping.yaml

@@ -0,0 +1,14 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "^mycoolmirror[.]org/library/(.*)$"
+    rewrite: "docker.io/library/$1"
+  - pattern: "^myevencoolermirror[.]org/library/(.*)$"
+    rewrite: "mycoolmirror.org/library/$1"

pkg/policy/testdata/mappings/rewrite-to-local/mapping.yaml

@@ -0,0 +1,12 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: local-policy
+    description: Local Policy
+    files:
+      - path: local-policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images # note this policy does not exist in this file
+  - pattern: "^mycoolmirror[.]org/library/(.*)$"
+    rewrite: "docker.io/library/$1"

pkg/policy/testdata/mappings/rewrite-to-no-match/mapping.yaml

@@ -0,0 +1,12 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "^mycoolmirror[.]org/library/(.*)$"
+    rewrite: "badredirect.org/$1" # no matching rule for this rewrite

pkg/policy/testdata/mappings/simple-rewrite/mapping.yaml

@@ -0,0 +1,12 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: docker-official-images
+    description: Docker Official Images
+    files:
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "^mycoolmirror[.]org/library/(.*)$"
+    rewrite: "docker.io/library/$1"

pkg/policy/testdata/mock-tuf-allow-canonical/mapping.yaml

@@ -2,15 +2,16 @@
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: docker-official-images
+  - id: docker-official-images
     description: Docker Official Images
+    attestations:
+      repo: "localhost:5001/library-refs"
     files:
       - path: doi/policy.rego
-mirrors:
-  - policy-id: docker-official-images
-    mirror:
-      domains: [localhost:5001, registry.local:5000]
-      prefix: ""
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: ^localhost:5001/(.*)$
+    rewrite: docker.io/library/$1
+  - pattern: ^registry[.]local:5000/(.*)$
+    rewrite: docker.io/library/$1

pkg/policy/testdata/mock-tuf-allow/mapping.yaml

@@ -2,17 +2,16 @@
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: docker-official-images
+  - id: docker-official-images
     description: Docker Official Images
     attestations:
       repo: "localhost:5001/library-refs"
     files:
       - path: doi/policy.rego
-mirrors:
-  - policy-id: docker-official-images
-    mirror:
-      domains: [localhost:5001, registry.local:5000]
-      prefix: ""
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: ^localhost:5001/(.*)$
+    rewrite: docker.io/library/$1
+  - pattern: ^registry[.]local:5000/(.*)$
+    rewrite: docker.io/library/$1

pkg/policy/testdata/mock-tuf-deny/mapping.yaml

@@ -2,10 +2,10 @@
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: docker-official-images
+  - id: docker-official-images
     description: Docker Official Images
     files:
       - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images

pkg/policy/testdata/mock-tuf-verify-sig/mapping.yaml

@@ -2,10 +2,10 @@
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: docker-official-images
+  - id: docker-official-images
     description: Docker Official Images
     files:
       - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images

pkg/policy/testdata/mock-tuf-wrong-key/mapping.yaml

@@ -2,10 +2,10 @@
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: docker-official-images
+  - id: docker-official-images
     description: Docker Official Images
     files:
       - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images

pkg/policy/types.go

@@ -36,9 +36,10 @@ type PolicyOptions struct {
 }
 
 type Policy struct {
-	InputFiles []*PolicyFile
-	Query      string
-	Mapping    *config.PolicyMapping
+	InputFiles   []*PolicyFile
+	Query        string
+	Mapping      *config.PolicyMapping
+	ResolvedName string
 }
 
 type PolicyInput struct {

test/testdata/local-policy-fail/mapping.yaml

@@ -1,11 +1,10 @@
-# map repos to policies
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: test-images
+  - id: test-images
     description: Local test images
     files:
-      - path: doi/policy.rego
+      - path: policy.rego
+rules:
+  - pattern: ".*"
+    policy-id: test-images

test/testdata/local-policy-mirror/mapping.yaml

@@ -0,0 +1,12 @@
+version: v1
+kind: policy-mapping
+policies:
+  - id: test-images
+    description: Local test images
+    files:
+      - path: policy.rego
+rules:
+  - pattern: "^docker[.]io/library/test-image$"
+    policy-id: test-images
+  - pattern: "^mirror[.]org/library/(.*)$"
+    rewrite: docker.io/library/$1

test/testdata/local-policy-mirror/policy.rego

@@ -0,0 +1,54 @@
+package attest
+
+import rego.v1
+
+keys := [{
+	"id": "6b241993defaba26558c64f94a94303ce860e7ad9163d801495c91cf57197c75",
+	"key": "-----BEGIN PUBLIC KEY-----\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEZmicqYSY38DprGr42jU0V3ND0ROj\nzSRH1+yjsxhh0bi52Hh/DuOhrSq2KJ5a09lW3ybnDjljowbkof0Y1i9Oow==\n-----END PUBLIC KEY-----",
+	"from": "2023-12-15T14:00:00Z",
+	"to": null,
+	# this key is still active
+	"status": "active",
+	"signing-format": "dssev1",
+}]
+
+provs(pred) := p if {
+	res := attest.fetch(pred)
+	not res.error
+	p := res.value
+}
+
+atts := union({
+	provs("https://slsa.dev/provenance/v0.2"),
+	provs("https://spdx.dev/Document"),
+})
+
+opts := {"keys": keys}
+
+statements contains s if {
+	some att in atts
+	res := attest.verify(att, opts)
+	not res.error
+	s := res.value
+}
+
+subjects contains subject if {
+	some statement in statements
+	some subject in statement.subject
+}
+
+success if {
+	print("input:",input)
+	true
+}
+
+result := {
+	"success": success,
+	"violations": set(),
+	"summary": {
+		"subjects": subjects,
+		"slsa_levels": ["SLSA_BUILD_LEVEL_3"],
+		"verifier": "docker-official-images",
+		"policy_uri": "https://docker.com/official/policy/v0.1",
+	},
+}

test/testdata/local-policy-no-tl/mapping.yaml

@@ -1,11 +1,10 @@
-# map repos to policies
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: test-images
+  - id: test-images
     description: Local test images
     files:
-      - path: doi/policy.rego
+      - path: policy.rego
+rules:
+  - pattern: ".*"
+    policy-id: test-images

test/testdata/local-policy-pass/mapping.yaml

@@ -1,16 +1,10 @@
-# map repos to policies
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: test-images
+  - id: test-images
     description: Local test images
     files:
-      - path: doi/policy.rego
-mirrors:
-  - policy-id: test-images
-    mirror:
-      domains: ["*"]
-      prefix: ""
+      - path: policy.rego
+rules:
+  - pattern: ".*"
+    policy-id: test-images

test/testdata/local-policy/mapping.yaml

@@ -1,29 +1,18 @@
-# map repos to policies
 version: v1
 kind: policy-mapping
 policies:
-  - origin:
-      domain: docker.io
-      prefix: library/
-    id: test-images
-    description: Local test images
+  - id: docker-official-images
+    description: Docker Official Images
     files:
-      - path: "doi/policy.rego"
-
-mirrors:
-  - policy-id: test-images
-    mirror:
-      domains: ["*"]
-      prefix: "repo"
-  - policy-id: test-images
-    mirror:
-      domains: ["*"]
-      prefix: "library/"
-  - policy-id: test-images
-    mirror:
-      domains: ["*"]
-      prefix: "test-image"
-  - policy-id: test-images
-    mirror:
-      domains: ["*"]
-      prefix: "image-signer-verifier-test"
+      - path: doi/policy.rego
+rules:
+  - pattern: "^docker[.]io/library/(.*)$"
+    policy-id: docker-official-images
+  - pattern: "repo$"
+    policy-id: docker-official-images
+  - pattern: "test-image$"
+    policy-id: docker-official-images
+  - pattern: "image-signer-verifier-test$"
+    policy-id: docker-official-images
+  - pattern: "library/(.*)$"
+    rewrite: docker.io/library/$1