fix: remove CUE workflow-contract support

- unmarshal: drop all CUE compilation. IdentifyFormat no longer detects CUE,
  FromRaw and LoadJSONBytes reject the CUE format with a clear error, and the
  cuelang.org/go dependency is removed.
- The RawFormatCUE constant and the wire enum value are retained (unused) so
  contracts already stored with that format and the existing API stay valid; no
  database migration is required.
- Remove CUE test cases and fixtures across unmarshal, biz and crafter, and the
  CUE contract example under docs.

Signed-off-by: Matías Insaurralde <matias@chainloop.dev>

Author: matiasinsaurralde

app/cli/pkg/action/util.go

@@ -123,11 +123,6 @@ func extractNameFromMetadata(content []byte) (string, error) {
 		if err != nil {
 			return "", err
 		}
-	case unmarshal.RawFormatCUE:
-		jsonData, err = unmarshal.LoadJSONBytes(content, ".cue")
-		if err != nil {
-			return "", err
-		}
 	default:
 		return "", fmt.Errorf("unsupported format: %s", format)
 	}

app/controlplane/pkg/biz/testdata/contracts/contract.cue

@@ -349,11 +349,6 @@ func (s *workflowContractIntegrationTestSuite) TestCreateWithCustomContract() {
 		wantErrMsg   string
 		format       unmarshal.RawFormat
 	}{
-		{
-			name:         "from-cue",
-			contractPath: "testdata/contracts/contract.cue",
-			format:       unmarshal.RawFormatCUE,
-		},
 		{
 			name:         "from-yaml",
 			contractPath: "testdata/contracts/contract.yaml",

app/controlplane/pkg/biz/workflowcontract_integration_test.go

@@ -31,10 +31,6 @@ func TestIdentifyAndValidateRawContract(t *testing.T) {
 		wantValidationErr bool
 		wantFormatErr     bool
 	}{
-		{
-			filename:   "contract.cue",
-			wantFormat: unmarshal.RawFormatCUE,
-		},
 		{
 			filename:   "contract.json",
 			wantFormat: unmarshal.RawFormatJSON,

app/controlplane/pkg/biz/workflowcontract_test.go

@@ -22,7 +22,6 @@ import (
 
 	"buf.build/go/protovalidate"
 	"buf.build/go/protoyaml"
-	"cuelang.org/go/cue/cuecontext"
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/proto"
 	"gopkg.in/yaml.v2"
@@ -34,9 +33,18 @@ type RawFormat string
 const (
 	RawFormatJSON RawFormat = "json"
 	RawFormatYAML RawFormat = "yaml"
-	RawFormatCUE  RawFormat = "cue"
+	// RawFormatCUE is retained only so contracts already stored with this format
+	// (and the wire enum) remain valid. CUE is no longer accepted or evaluated:
+	// evaluating attacker-supplied CUE server-side is an unbounded, uncancellable
+	// operation and was a DoS vector. New contracts must be JSON or YAML.
+	RawFormatCUE RawFormat = "cue"
 )
 
+// errCUENotSupported is returned wherever a CUE document would previously have
+// been compiled and evaluated. CUE support was removed to close the unbounded
+// server-side evaluation DoS.
+var errCUENotSupported = errors.New("CUE contract format is no longer supported; use JSON or YAML")
+
 // Implements https://pkg.go.dev/entgo.io/ent/schema/field#EnumValues
 func (RawFormat) Values() (kinds []string) {
 	for _, s := range []RawFormat{RawFormatJSON, RawFormatYAML, RawFormatCUE} {
@@ -82,16 +90,7 @@ func FromRaw(body []byte, format RawFormat, out proto.Message, doValidate bool)
 			return fmt.Errorf("error unmarshalling raw message: %w", err)
 		}
 	case RawFormatCUE:
-		ctx := cuecontext.New()
-		v := ctx.CompileBytes(body)
-		jsonRawData, err := v.MarshalJSON()
-		if err != nil {
-			return fmt.Errorf("error unmarshalling raw message: %w", err)
-		}
-
-		if err := jsonOpts.Unmarshal(jsonRawData, out); err != nil {
-			return fmt.Errorf("error unmarshalling raw message: %w", err)
-		}
+		return errCUENotSupported
 	default:
 		return fmt.Errorf("unsupported format: %s", format)
 	}
@@ -106,23 +105,17 @@ func FromRaw(body []byte, format RawFormat, out proto.Message, doValidate bool)
 }
 
 // IdentifyFormat does best effort to identify the format of the raw contract
-// by going the unmarshalling path in the following order: json, cue, yaml
+// by going the unmarshalling path in the following order: json, yaml.
 // NOTE that we are just validating the format, not the content using regular marshalling
-// not even proto marshalling, that comes later once we know the format
+// not even proto marshalling, that comes later once we know the format.
+// CUE is intentionally not detected: it is no longer a supported contract format.
 func IdentifyFormat(raw []byte) (RawFormat, error) {
 	// json marshalling first
 	var sink any
 	if err := json.Unmarshal(raw, &sink); err == nil {
 		return RawFormatJSON, nil
 	}
 
-	// cue marshalling next
-	ctx := cuecontext.New()
-	v := ctx.CompileBytes(raw)
-	if _, err := v.MarshalJSON(); err == nil {
-		return RawFormatCUE, nil
-	}
-
 	// yaml marshalling last
 	if err := yaml.Unmarshal(raw, &sink); err == nil {
 		return RawFormatYAML, nil
@@ -131,7 +124,7 @@ func IdentifyFormat(raw []byte) (RawFormat, error) {
 	return "", errors.New("format not found")
 }
 
-// LoadJSONBytes Extracts raw data in JSON format from different sources, i.e cue or yaml files
+// LoadJSONBytes Extracts raw data in JSON format from different sources, i.e yaml or json files
 func LoadJSONBytes(rawData []byte, extension string) ([]byte, error) {
 	var jsonRawData []byte
 	var err error
@@ -143,12 +136,7 @@ func LoadJSONBytes(rawData []byte, extension string) ([]byte, error) {
 			return nil, err
 		}
 	case ".cue":
-		ctx := cuecontext.New()
-		v := ctx.CompileBytes(rawData)
-		jsonRawData, err = v.MarshalJSON()
-		if err != nil {
-			return nil, err
-		}
+		return nil, errCUENotSupported
 	case ".json":
 		jsonRawData = rawData
 	default:

app/controlplane/pkg/unmarshal/testdata/contracts/contract.cue

@@ -48,23 +48,13 @@ spec:
     {"name": "b", "type": "ARTIFACT", "group": "choice"}
   ]}
 }`)
-	cueContract := []byte(`apiVersion: "chainloop.dev/v1"
-kind: "Contract"
-metadata: name: "test-contract"
-spec: materials: [
-	{name: "a", type: "ARTIFACT", group: "choice"},
-	{name: "b", type: "ARTIFACT", group: "choice"},
-]
-`)
-
 	formats := []struct {
 		name   string
 		format RawFormat
 		body   []byte
 	}{
 		{"yaml", RawFormatYAML, yamlContract},
 		{"json", RawFormatJSON, jsonContract},
-		{"cue", RawFormatCUE, cueContract},
 	}
 
 	t.Run("group round-trips", func(t *testing.T) {
@@ -123,10 +113,6 @@ func TestIdentifyFormat(t *testing.T) {
 		wantFormat RawFormat
 		wantErr    bool
 	}{
-		{
-			filename:   "contract.cue",
-			wantFormat: RawFormatCUE,
-		},
 		{
 			filename:   "contract.json",
 			wantFormat: RawFormatJSON,
@@ -166,3 +152,27 @@ func TestIdentifyFormat(t *testing.T) {
 		})
 	}
 }
+
+// TestCUEIsRejected locks in the removal of CUE support: the DoS payload from the
+// security finding (a tiny CUE document whose evaluation is unbounded) must be
+// rejected immediately, without ever being compiled or evaluated.
+func TestCUEIsRejected(t *testing.T) {
+	// ~55-byte CUE bomb: evaluating it used to allocate a multi-million-element list.
+	cuePayload := []byte("import \"list\"\na: [for x in list.Range(0,1000000,1) {x}]\n")
+
+	t.Run("IdentifyFormat no longer detects CUE", func(t *testing.T) {
+		_, err := IdentifyFormat(cuePayload)
+		require.Error(t, err)
+	})
+
+	t.Run("FromRaw rejects the CUE format", func(t *testing.T) {
+		out := &schemav1.CraftingSchemaV2{}
+		err := FromRaw(cuePayload, RawFormatCUE, out, false)
+		require.ErrorIs(t, err, errCUENotSupported)
+	})
+
+	t.Run("LoadJSONBytes rejects .cue", func(t *testing.T) {
+		_, err := LoadJSONBytes(cuePayload, ".cue")
+		require.ErrorIs(t, err, errCUENotSupported)
+	})
+}

app/controlplane/pkg/unmarshal/unmarshal.go

@@ -5,7 +5,6 @@ go 1.26.4
 require (
 	cloud.google.com/go/secretmanager v1.20.0
 	code.cloudfoundry.org/bytefmt v0.75.0
-	cuelang.org/go v0.16.1
 	entgo.io/ent v0.14.6
 	github.com/adrg/xdg v0.5.3
 	github.com/aws/aws-sdk-go-v2 v1.41.11
@@ -164,7 +163,6 @@ require (
 	github.com/charmbracelet/lipgloss v0.5.0 // indirect
 	github.com/clipperhouse/uax29/v2 v2.6.0 // indirect
 	github.com/cncf/xds/go v0.0.0-20260202195803-dba9d589def2 // indirect
-	github.com/cockroachdb/apd/v3 v3.2.1 // indirect
 	github.com/containerd/errdefs v1.0.0 // indirect
 	github.com/containerd/errdefs/pkg v0.3.0 // indirect
 	github.com/containerd/log v0.1.0 // indirect
@@ -180,7 +178,6 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/dylibso/observe-sdk/go v0.0.0-20240819160327-2d926c5d788a // indirect
 	github.com/ebitengine/purego v0.8.4 // indirect
-	github.com/emicklei/proto v1.14.3 // indirect
 	github.com/emirpasic/gods v1.18.1 // indirect
 	github.com/envoyproxy/go-control-plane/envoy v1.37.0 // indirect
 	github.com/envoyproxy/protoc-gen-validate v1.3.3 // indirect
@@ -274,7 +271,6 @@ require (
 	github.com/pkg/xattr v0.4.12 // indirect
 	github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
 	github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55 // indirect
-	github.com/protocolbuffers/txtpbfmt v0.0.0-20260217160748-a481f6a22f94 // indirect
 	github.com/rcrowley/go-metrics v0.0.0-20250401214520-65e299d6c5c9 // indirect
 	github.com/rs/xid v1.6.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
@@ -358,7 +354,7 @@ require (
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/desertbit/timer v0.0.0-20180107155436-c41aec40b27f // indirect
 	github.com/digitorus/pkcs7 v0.0.0-20230818184609-3a137a874352 // indirect
-	github.com/digitorus/timestamp v0.0.0-20231217203849-220c5c2851b7 // indirect
+	github.com/digitorus/timestamp v0.0.0-20231217203849-220c5c2851b7
 	github.com/docker/cli v29.4.3+incompatible // indirect
 	github.com/docker/docker v28.5.2+incompatible // indirect
 	github.com/docker/docker-credential-helpers v0.9.5 // indirect