refac: removed 7 direct and 12 indirect go modules for custom code instead

api/pkg/authtoken/authtoken.go

@@ -0,0 +1,170 @@
+package authtoken
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"maps"
+	"strings"
+	"time"
+)
+
+const (
+	SessionLifetime = 24 * time.Hour
+
+	algorithmHS256 = "HS256"
+	tokenType      = "JWT"
+	maxTokenBytes  = 4096
+	segmentCount   = 3
+	segmentSep     = "."
+)
+
+var (
+	ErrNoToken     = errors.New("no token found")
+	ErrInvalid     = errors.New("token is invalid")
+	ErrExpired     = errors.New("token is expired")
+	ErrNotYetValid = errors.New("token is not yet valid")
+)
+
+type Claims map[string]any
+
+type header struct {
+	Algorithm string `json:"alg"`
+	Type      string `json:"typ,omitempty"`
+}
+
+type Auth struct {
+	secret []byte
+	clock  func() time.Time
+}
+
+type Option func(*Auth)
+
+func WithClock(clock func() time.Time) Option {
+	return func(a *Auth) { a.clock = clock }
+}
+
+func New(secret []byte, options ...Option) *Auth {
+	auth := &Auth{secret: secret, clock: time.Now}
+	for _, option := range options {
+		option(auth)
+	}
+	return auth
+}
+
+func (a *Auth) Encode(claims map[string]any) (string, error) {
+	payload := maps.Clone(claims)
+	if payload == nil {
+		payload = map[string]any{}
+	}
+	now := a.clock()
+	if _, ok := payload["iat"]; !ok {
+		payload["iat"] = now.Unix()
+	}
+	if _, ok := payload["exp"]; !ok {
+		payload["exp"] = now.Add(SessionLifetime).Unix()
+	}
+
+	headerSegment, err := encodeSegment(header{Algorithm: algorithmHS256, Type: tokenType})
+	if err != nil {
+		return "", err
+	}
+	payloadSegment, err := encodeSegment(payload)
+	if err != nil {
+		return "", err
+	}
+
+	signingInput := headerSegment + segmentSep + payloadSegment
+	return signingInput + segmentSep + a.sign(signingInput), nil
+}
+
+func (a *Auth) Decode(token string) (Claims, error) {
+	if token == "" {
+		return nil, ErrNoToken
+	}
+	if len(token) > maxTokenBytes {
+		return nil, ErrInvalid
+	}
+
+	segments := strings.Split(token, segmentSep)
+	if len(segments) != segmentCount {
+		return nil, ErrInvalid
+	}
+
+	var tokenHeader header
+	if err := decodeSegment(segments[0], &tokenHeader); err != nil || tokenHeader.Algorithm != algorithmHS256 {
+		return nil, ErrInvalid
+	}
+
+	signingInput := segments[0] + segmentSep + segments[1]
+	if !hmac.Equal([]byte(a.sign(signingInput)), []byte(segments[2])) {
+		return nil, ErrInvalid
+	}
+
+	var claims Claims
+	if err := decodeSegment(segments[1], &claims); err != nil || claims == nil {
+		return nil, ErrInvalid
+	}
+
+	if err := a.validateTimes(claims); err != nil {
+		return nil, err
+	}
+	return claims, nil
+}
+
+func (a *Auth) validateTimes(claims Claims) error {
+	now := a.clock()
+
+	expiry, present, err := numericDate(claims, "exp")
+	if err != nil {
+		return err
+	}
+	if present && !now.Before(expiry) {
+		return ErrExpired
+	}
+
+	notBefore, present, err := numericDate(claims, "nbf")
+	if err != nil {
+		return err
+	}
+	if present && now.Before(notBefore) {
+		return ErrNotYetValid
+	}
+	return nil
+}
+
+func numericDate(claims Claims, name string) (time.Time, bool, error) {
+	raw, present := claims[name]
+	if !present {
+		return time.Time{}, false, nil
+	}
+	seconds, ok := raw.(float64)
+	if !ok {
+		return time.Time{}, false, ErrInvalid
+	}
+	return time.Unix(int64(seconds), 0), true, nil
+}
+
+func (a *Auth) sign(signingInput string) string {
+	mac := hmac.New(sha256.New, a.secret)
+	mac.Write([]byte(signingInput))
+	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
+}
+
+func encodeSegment(value any) (string, error) {
+	encoded, err := json.Marshal(value)
+	if err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(encoded), nil
+}
+
+func decodeSegment(segment string, into any) error {
+	decoded, err := base64.RawURLEncoding.DecodeString(segment)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(decoded, into)
+}