FR: Add spec validators for the WRP messages

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/go-kit/kit v0.8.0
 	github.com/go-logfmt/logfmt v0.3.0 // indirect
 	github.com/go-stack/stack v1.8.0 // indirect
+	github.com/google/uuid v1.3.0
 	github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515 // indirect
 	github.com/stretchr/testify v1.7.0
 	github.com/ugorji/go/codec v1.2.6

go.sum

@@ -7,6 +7,8 @@ github.com/go-logfmt/logfmt v0.3.0 h1:8HUsc87TaSWLKwrnumgC8/YconD2fJQsRJAsWaPg2i
 github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE=
 github.com/go-stack/stack v1.8.0 h1:5SgMzNM5HxrEjV0ww2lTmX6E2Izsfxas4+YHWRs3Lsk=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515 h1:T+h1c/A9Gawja4Y9mFVWj2vyii2bbUNDw3kt9VxK2EY=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

spec_validator.go

@@ -0,0 +1,160 @@
+/**
+ *  Copyright (c) 2022  Comcast Cable Communications Management, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package wrp
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+	"unicode"
+
+	"github.com/google/uuid"
+)
+
+const (
+	serialPrefix = "serial"
+	uuidPrefix   = "uuid"
+	eventPrefix  = "event"
+	dnsPrefix    = "dns"
+)
+
+var (
+	ErrorInvalidMessageEncoding = errors.New("invalid message encoding")
+	ErrorInvalidMessageType     = errors.New("invalid message type")
+	ErrorInvalidSource          = errors.New("invalid Source name")
+	ErrorInvalidDestination     = errors.New("invalid Destination name")
+	errInvalidUUID              = errors.New("invalid UUID")
+	errEmptyAuthority           = errors.New("invalid empty authority (ID)")
+	errInvalidMacLength         = errors.New("invalid mac length")
+	errInvalidCharacter         = errors.New("invalid character")
+	errInvalidLocatorPattern    = errors.New("value given doesn't match expected locator pattern")
+)
+
+// locatorPattern is the precompiled regular expression that all source and dest locators must match.
+// Matching is partial, as everything after the authority (ID) is ignored. https://xmidt.io/docs/wrp/basics/#locators
+var locatorPattern = regexp.MustCompile(
+	`^(?P<scheme>(?i)` + macPrefix + `|` + uuidPrefix + `|` + eventPrefix + `|` + dnsPrefix + `|` + serialPrefix + `):(?P<authority>[^/]+)?`,
+)
+
+// SpecValidators returns a WRP validator that ensures messages are valid based on
+// each spec validator in the list. Only validates the opinionated portions of the spec.
+// SpecValidators validates the following fields: UTF8 (all string fields), MessageType, Source, Destination
+func SpecValidators() Validators {
+	return Validators{UTF8Validator(), MessageTypeValidator(), SourceValidator(), DestinationValidator()}
+}
+
+// UTF8Validator returns a WRP validator that takes messages and validates that it contains UTF-8 strings.
+func UTF8Validator() ValidatorFunc {
+	return func(m Message) error {
+		if err := UTF8(m); err != nil {
+			return fmt.Errorf("%w: %v", ErrorInvalidMessageEncoding, err)
+		}
+
+		return nil
+	}
+}
+
+// MessageTypeValidator returns a WRP validator that takes messages and validates their Type.
+func MessageTypeValidator() ValidatorFunc {
+	return func(m Message) error {
+		if m.Type < Invalid0MessageType || m.Type > lastMessageType {
+			return ErrorInvalidMessageType
+		}
+
+		switch m.Type {
+		case Invalid0MessageType, Invalid1MessageType, lastMessageType:
+			return ErrorInvalidMessageType
+		}
+
+		return nil
+	}
+}
+
+// SourceValidator returns a WRP validator that takes messages and validates their Source.
+// Only mac and uuid sources are validated. Serial, event and dns sources are
+// not validated.
+func SourceValidator() ValidatorFunc {
+	return func(m Message) error {
+		if err := validateLocator(m.Source); err != nil {
+			return fmt.Errorf("%w '%s': %v", ErrorInvalidSource, m.Source, err)
+		}
+
+		return nil
+	}
+}
+
+// DestinationValidator returns a WRP validator that takes messages and validates their Destination.
+// Only mac and uuid destinations are validated. Serial, event and dns destinations are
+// not validated.
+func DestinationValidator() ValidatorFunc {
+	return func(m Message) error {
+		if err := validateLocator(m.Destination); err != nil {
+			return fmt.Errorf("%w '%s': %v", ErrorInvalidDestination, m.Destination, err)
+		}
+
+		return nil
+	}
+}
+
+// validateLocator validates a given locator's scheme and authority (ID).
+// Only mac and uuid schemes' IDs are validated. IDs from serial, event and dns schemes are
+// not validated.
+func validateLocator(l string) error {
+	match := locatorPattern.FindStringSubmatch(l)
+	if match == nil {
+		return errInvalidLocatorPattern
+	}
+
+	idPart := match[2]
+	if len(idPart) == 0 {
+		return errEmptyAuthority
+	}
+
+	switch strings.ToLower(match[1]) {
+	case macPrefix:
+		var invalidCharacter rune = -1
+		idPart = strings.Map(
+			func(r rune) rune {
+				switch {
+				case strings.ContainsRune(hexDigits, r):
+					return unicode.ToLower(r)
+				case strings.ContainsRune(macDelimiters, r):
+					return -1
+				default:
+					invalidCharacter = r
+					return -1
+				}
+			},
+			idPart,
+		)
+
+		if invalidCharacter != -1 {
+			return fmt.Errorf("%w: %v", errInvalidCharacter, strconv.QuoteRune(invalidCharacter))
+		} else if len(idPart) != macLength {
+			return errInvalidMacLength
+		}
+	case uuidPrefix:
+		if _, err := uuid.Parse(idPart); err != nil {
+			return fmt.Errorf("%w: %v", errInvalidUUID, err)
+		}
+	}
+
+	return nil
+}