aspects: check map key format in parsing and validation

Signed-off-by: Miguel Pires <miguel.pires@canonical.com>

aspects/schema.go

@@ -246,6 +246,10 @@ func (v *mapSchema) Validate(raw []byte) error {
 		return validationErrorf(`cannot accept null value for "map" type`)
 	}
 
+	if err := validMapKeys(mapValue); err != nil {
+		return validationErrorFrom(err)
+	}
+
 	if v.entrySchemas != nil {
 		for key := range mapValue {
 			if _, ok := v.entrySchemas[key]; !ok {
@@ -323,6 +327,16 @@ func (v *mapSchema) Validate(raw []byte) error {
 	return nil
 }
 
+func validMapKeys(v map[string]json.RawMessage) error {
+	for k := range v {
+		if !validSubkey.Match([]byte(k)) {
+			return fmt.Errorf(`key %q doesn't conform to required format`, k)
+		}
+	}
+
+	return nil
+}
+
 func (v *mapSchema) parseConstraints(constraints map[string]json.RawMessage) error {
 	err := checkExclusiveMapConstraints(constraints)
 	if err != nil {
@@ -336,6 +350,10 @@ func (v *mapSchema) parseConstraints(constraints map[string]json.RawMessage) err
 			return fmt.Errorf(`cannot parse map's "schema" constraint: %v`, err)
 		}
 
+		if err := validMapKeys(entries); err != nil {
+			return fmt.Errorf(`cannot parse map: %w`, err)
+		}
+
 		v.entrySchemas = make(map[string]Schema, len(entries))
 		for key, value := range entries {
 			entrySchema, err := v.topSchema.parse(value)

aspects/schema_test.go

@@ -441,6 +441,34 @@ func (*schemaSuite) TestMapSchemaRequiredNotInSchema(c *C) {
 	c.Assert(err, ErrorMatches, `cannot parse map's "required" constraint: required key "baz" must have schema entry`)
 }
 
+func (*schemaSuite) TestMapSchemaWithInvalidKeyFormat(c *C) {
+	schemaStr := []byte(`{
+	"schema": {
+		"-foo": "string"
+	}
+}`)
+
+	_, err := aspects.ParseSchema(schemaStr)
+	c.Assert(err, ErrorMatches, `cannot parse map: key "-foo" doesn't conform to required format`)
+}
+
+func (*schemaSuite) TestMapRejectsInputMapWithInvalidKeyFormat(c *C) {
+	schemaStr := []byte(`{
+	"schema": {
+		"foo": "int"
+	}
+}`)
+
+	schema, err := aspects.ParseSchema(schemaStr)
+	c.Assert(err, IsNil)
+
+	input := []byte(`{
+	"-foo": 1
+}`)
+	err = schema.Validate(input)
+	c.Assert(err, ErrorMatches, `cannot accept top level element: key "-foo" doesn't conform to required format`)
+}
+
 func (*schemaSuite) TestMapInvalidConstraintCombos(c *C) {
 	type testcase struct {
 		name    string