Add JSON schema for the JSON embedded inside signatures

docs/atomic-signature-embedded-json.json

@@ -0,0 +1,66 @@
+{
+    "title": "JSON embedded in an atomic container signature",
+    "description": "This schema is a supplement to atomic-signature.md in this directory.\n\nConsumers of the JSON MUST use the processing rules documented in atomic-signature.md, especially the requirements for the 'critical' subjobject.\n\nWhenever this schema and atomic-signature.md, or the github.com/containers/image/signature implementation, differ,\nit is the atomic-signature.md document, or the github.com/containers/image/signature implementation, which governs.\n\nUsers are STRONGLY RECOMMENDED to use the github.com/containeres/image/signature implementation instead of writing\ntheir own, ESPECIALLY when consuming signatures, so that the policy.json format can be shared by all image consumers.\n",
+    "type": "object",
+    "required": [
+        "critical",
+        "optional"
+    ],
+    "additionalProperties": false,
+    "properties": {
+        "critical": {
+            "type": "object",
+            "required": [
+                "type",
+                "image",
+                "identity"
+            ],
+            "additionalProperties": false,
+            "properties": {
+                "type": {
+                    "type": "string",
+                    "enum": [
+                        "atomic container signature"
+                    ]
+                },
+                "image": {
+                    "type": "object",
+                    "required": [
+                        "docker-manifest-digest"
+                    ],
+                    "additionalProperties": false,
+                    "properties": {
+                        "docker-manifest-digest": {
+                            "type": "string"
+                        }
+                    }
+                },
+                "identity": {
+                    "type": "object",
+                    "required": [
+                        "docker-reference"
+                    ],
+                    "additionalProperties": false,
+                    "properties": {
+                        "docker-reference": {
+                            "type": "string"
+                        }
+                    }
+                }
+            }
+        },
+        "optional": {
+            "type": "object",
+            "description": "All members are optional, but if they are included, they must be valid.",
+            "additionalProperties": true,
+            "properties": {
+                "creator": {
+                    "type": "string"
+                },
+                "timestamp": {
+                    "type": "integer"
+                }
+            }
+        }
+    }
+}

signature/signature.go

@@ -1,6 +1,6 @@
 // Note: Consider the API unstable until the code supports at least three different image formats or transports.
 
-// NOTE: Keep this in sync with docs/atomic-signature.md!
+// NOTE: Keep this in sync with docs/atomic-signature.md and docs/atomic-signature-embedded.json!
 
 package signature
 

signature/signature_test.go

@@ -3,6 +3,7 @@ package signature
 import (
 	"encoding/json"
 	"io/ioutil"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -11,6 +12,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/xeipuuv/gojsonschema"
 )
 
 func TestInvalidSignatureError(t *testing.T) {
@@ -78,43 +80,71 @@ func TestMarshalJSON(t *testing.T) {
 	}
 }
 
-// Return the result of modifying validJSON with fn and unmarshaling it into *sig
-func tryUnmarshalModifiedSignature(t *testing.T, sig *untrustedSignature, validJSON []byte, modifyFn func(mSI)) error {
+// Return the result of modifying validJSON with fn
+func modifiedUntrustedSignatureJSON(t *testing.T, validJSON []byte, modifyFn func(mSI)) []byte {
 	var tmp mSI
 	err := json.Unmarshal(validJSON, &tmp)
 	require.NoError(t, err)
 
 	modifyFn(tmp)
 
-	testJSON, err := json.Marshal(tmp)
+	modifiedJSON, err := json.Marshal(tmp)
 	require.NoError(t, err)
+	return modifiedJSON
+}
+
+// Verify that input can be unmarshaled as an untrustedSignature, and that it passes JSON schema validation, and return the unmarshaled untrustedSignature.
+func succesfullyUnmarshalUntrustedSignature(t *testing.T, schemaLoader gojsonschema.JSONLoader, input []byte) untrustedSignature {
+	inputString := string(input)
+
+	var s untrustedSignature
+	err := json.Unmarshal(input, &s)
+	require.NoError(t, err, inputString)
+
+	res, err := gojsonschema.Validate(schemaLoader, gojsonschema.NewStringLoader(inputString))
+	assert.True(t, err == nil, inputString)
+	assert.True(t, res.Valid(), inputString)
 
-	*sig = untrustedSignature{}
-	return json.Unmarshal(testJSON, sig)
+	return s
 }
 
-func TestUnmarshalJSON(t *testing.T) {
+// Verify that input can't be unmashaled as an untrusted signature, and that it fails JSON schema validation.
+func assertUnmarshalUntrustedSignatureFails(t *testing.T, schemaLoader gojsonschema.JSONLoader, input []byte) {
+	inputString := string(input)
+
 	var s untrustedSignature
+	err := json.Unmarshal(input, &s)
+	assert.Error(t, err, inputString)
+
+	res, err := gojsonschema.Validate(schemaLoader, gojsonschema.NewStringLoader(inputString))
+	assert.True(t, err != nil || !res.Valid(), inputString)
+}
+
+func TestUnmarshalJSON(t *testing.T) {
+	// NOTE: The schema at schemaPath is NOT authoritative; docs/atomic-signature.json and the code is, rather!
+	// The schemaPath references are not testing that the code follows the behavior declared by the schema,
+	// they are testing that the schema follows the behavior of the code!
+	schemaPath, err := filepath.Abs("../docs/atomic-signature-embedded-json.json")
+	require.NoError(t, err)
+	schemaLoader := gojsonschema.NewReferenceLoader("file://" + schemaPath)
+
 	// Invalid input. Note that json.Unmarshal is guaranteed to validate input before calling our
 	// UnmarshalJSON implementation; so test that first, then test our error handling for completeness.
-	err := json.Unmarshal([]byte("&"), &s)
-	assert.Error(t, err)
+	assertUnmarshalUntrustedSignatureFails(t, schemaLoader, []byte("&"))
+	var s untrustedSignature
 	err = s.UnmarshalJSON([]byte("&"))
 	assert.Error(t, err)
 
 	// Not an object
-	err = json.Unmarshal([]byte("1"), &s)
-	assert.Error(t, err)
+	assertUnmarshalUntrustedSignatureFails(t, schemaLoader, []byte("1"))
 
 	// Start with a valid JSON.
 	validSig := newUntrustedSignature("digest!@#", "reference#@!")
 	validJSON, err := validSig.MarshalJSON()
 	require.NoError(t, err)
 
 	// Success
-	s = untrustedSignature{}
-	err = json.Unmarshal(validJSON, &s)
-	require.NoError(t, err)
+	s = succesfullyUnmarshalUntrustedSignature(t, schemaLoader, validJSON)
 	assert.Equal(t, validSig, s)
 
 	// Various ways to corrupt the JSON
@@ -156,8 +186,8 @@ func TestUnmarshalJSON(t *testing.T) {
 		func(v mSI) { x(v, "optional")["timestamp"] = 0.5 }, // Fractional input
 	}
 	for _, fn := range breakFns {
-		err = tryUnmarshalModifiedSignature(t, &s, validJSON, fn)
-		assert.Error(t, err)
+		testJSON := modifiedUntrustedSignatureJSON(t, validJSON, fn)
+		assertUnmarshalUntrustedSignatureFails(t, schemaLoader, testJSON)
 	}
 
 	// Modifications to unrecognized fields in "optional" are allowed and ignored
@@ -166,8 +196,8 @@ func TestUnmarshalJSON(t *testing.T) {
 		func(v mSI) { x(v, "optional")["unexpected"] = 1 },
 	}
 	for _, fn := range allowedModificationFns {
-		err = tryUnmarshalModifiedSignature(t, &s, validJSON, fn)
-		require.NoError(t, err)
+		testJSON := modifiedUntrustedSignatureJSON(t, validJSON, fn)
+		s := succesfullyUnmarshalUntrustedSignature(t, schemaLoader, testJSON)
 		assert.Equal(t, validSig, s)
 	}
 
@@ -180,9 +210,7 @@ func TestUnmarshalJSON(t *testing.T) {
 	}
 	validJSON, err = validSig.MarshalJSON()
 	require.NoError(t, err)
-	s = untrustedSignature{}
-	err = json.Unmarshal(validJSON, &s)
-	require.NoError(t, err)
+	s = succesfullyUnmarshalUntrustedSignature(t, schemaLoader, validJSON)
 	assert.Equal(t, validSig, s)
 }
 

vendor.conf

@@ -29,3 +29,5 @@ gopkg.in/cheggaaa/pb.v1 d7e6ca3010b6f084d8056847f55d7f572f180678
 gopkg.in/yaml.v2 a3f3340b5840cee44f372bddb5880fcbc419b46a
 k8s.io/client-go bcde30fb7eaed76fd98a36b4120321b94995ffb6
 github.com/xeipuuv/gojsonschema master
+github.com/xeipuuv/gojsonreference master
+github.com/xeipuuv/gojsonpointer master