feat: add complete MFA support

Add complete MFA support with TOTP, recovery codes, WebAuthn, trusted-device cookie flow, and email/SMS OTP delivery via notification channels. Security follow-up: trusted device tokens are stored in HttpOnly cookies, and SMS OTP reuses the existing Webhook notifier to avoid introducing a new dynamic URL sink.

server/internal/security/otp_code.go

@@ -0,0 +1,23 @@
+package security
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math/big"
+	"strings"
+)
+
+const LoginOTPDigits = 6
+
+func GenerateNumericOTP() (string, error) {
+	limit := big.NewInt(1_000_000)
+	value, err := rand.Int(rand.Reader, limit)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%0*d", LoginOTPDigits, value.Int64()), nil
+}
+
+func NormalizeNumericOTP(code string) string {
+	return strings.TrimSpace(code)
+}

server/internal/security/recovery_code.go

@@ -0,0 +1,49 @@
+package security
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"strings"
+	"unicode"
+)
+
+const RecoveryCodeCount = 10
+
+func GenerateRecoveryCodes(count int) ([]string, error) {
+	if count <= 0 {
+		count = RecoveryCodeCount
+	}
+	codes := make([]string, 0, count)
+	for i := 0; i < count; i++ {
+		raw := make([]byte, 8)
+		if _, err := rand.Read(raw); err != nil {
+			return nil, fmt.Errorf("generate recovery code: %w", err)
+		}
+		encoded := strings.ToUpper(hex.EncodeToString(raw))
+		codes = append(codes, encoded[0:4]+"-"+encoded[4:8]+"-"+encoded[8:12]+"-"+encoded[12:16])
+	}
+	return codes, nil
+}
+
+func NormalizeRecoveryCode(code string) string {
+	return strings.Map(func(r rune) rune {
+		if unicode.IsSpace(r) || r == '-' {
+			return -1
+		}
+		return unicode.ToUpper(r)
+	}, strings.TrimSpace(code))
+}
+
+func IsRecoveryCodeCandidate(code string) bool {
+	normalized := NormalizeRecoveryCode(code)
+	if len(normalized) != 16 {
+		return false
+	}
+	for _, r := range normalized {
+		if !('0' <= r && r <= '9') && !('A' <= r && r <= 'F') {
+			return false
+		}
+	}
+	return true
+}

server/internal/security/totp.go

@@ -0,0 +1,68 @@
+package security
+
+import (
+	"bytes"
+	"encoding/base64"
+	"image/png"
+	"strings"
+	"time"
+	"unicode"
+
+	"github.com/pquerna/otp"
+	"github.com/pquerna/otp/totp"
+)
+
+const TOTPIssuer = "BackupX"
+
+type TOTPEnrollment struct {
+	Secret        string
+	OTPAuthURL    string
+	QRCodeDataURL string
+}
+
+func GenerateTOTPEnrollment(accountName string) (*TOTPEnrollment, error) {
+	key, err := totp.Generate(totp.GenerateOpts{
+		Issuer:      TOTPIssuer,
+		AccountName: accountName,
+		Period:      30,
+		SecretSize:  20,
+		Digits:      otp.DigitsSix,
+		Algorithm:   otp.AlgorithmSHA1,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	image, err := key.Image(220, 220)
+	if err != nil {
+		return nil, err
+	}
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, image); err != nil {
+		return nil, err
+	}
+
+	return &TOTPEnrollment{
+		Secret:        key.Secret(),
+		OTPAuthURL:    key.URL(),
+		QRCodeDataURL: "data:image/png;base64," + base64.StdEncoding.EncodeToString(buf.Bytes()),
+	}, nil
+}
+
+func ValidateTOTPCode(secret string, code string) (bool, error) {
+	return totp.ValidateCustom(NormalizeTOTPCode(code), secret, time.Now().UTC(), totp.ValidateOpts{
+		Period:    30,
+		Skew:      1,
+		Digits:    otp.DigitsSix,
+		Algorithm: otp.AlgorithmSHA1,
+	})
+}
+
+func NormalizeTOTPCode(code string) string {
+	return strings.Map(func(r rune) rune {
+		if unicode.IsSpace(r) {
+			return -1
+		}
+		return r
+	}, strings.TrimSpace(code))
+}

server/internal/security/webauthn.go

@@ -0,0 +1,447 @@
+package security
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/big"
+	"strings"
+)
+
+const (
+	WebAuthnChallengeBytes = 32
+)
+
+type WebAuthnCredentialMaterial struct {
+	CredentialID string
+	PublicKeyX   string
+	PublicKeyY   string
+	SignCount    uint32
+}
+
+type WebAuthnParsedCredential struct {
+	CredentialID string
+	PublicKeyX   string
+	PublicKeyY   string
+	SignCount    uint32
+}
+
+type WebAuthnClientData struct {
+	Type      string `json:"type"`
+	Challenge string `json:"challenge"`
+	Origin    string `json:"origin"`
+}
+
+type WebAuthnAttestationResponse struct {
+	ClientDataJSON    string `json:"clientDataJSON"`
+	AttestationObject string `json:"attestationObject"`
+}
+
+type WebAuthnRegistrationResponse struct {
+	ID       string                      `json:"id"`
+	RawID    string                      `json:"rawId"`
+	Type     string                      `json:"type"`
+	Response WebAuthnAttestationResponse `json:"response"`
+}
+
+type WebAuthnAssertionResponse struct {
+	ClientDataJSON    string `json:"clientDataJSON"`
+	AuthenticatorData string `json:"authenticatorData"`
+	Signature         string `json:"signature"`
+	UserHandle        string `json:"userHandle,omitempty"`
+}
+
+type WebAuthnLoginAssertion struct {
+	ID       string                    `json:"id"`
+	RawID    string                    `json:"rawId"`
+	Type     string                    `json:"type"`
+	Response WebAuthnAssertionResponse `json:"response"`
+}
+
+func GenerateWebAuthnChallenge() (string, error) {
+	buf := make([]byte, WebAuthnChallengeBytes)
+	if _, err := rand.Read(buf); err != nil {
+		return "", err
+	}
+	return EncodeBase64URL(buf), nil
+}
+
+func EncodeBase64URL(data []byte) string {
+	return base64.RawURLEncoding.EncodeToString(data)
+}
+
+func DecodeBase64URL(value string) ([]byte, error) {
+	trimmed := strings.TrimSpace(value)
+	if trimmed == "" {
+		return nil, errors.New("empty base64url value")
+	}
+	if decoded, err := base64.RawURLEncoding.DecodeString(trimmed); err == nil {
+		return decoded, nil
+	}
+	return base64.URLEncoding.DecodeString(trimmed)
+}
+
+func VerifyWebAuthnRegistration(input WebAuthnRegistrationResponse, challenge string, rpID string, expectedOrigin string) (*WebAuthnParsedCredential, error) {
+	if input.Type != "public-key" {
+		return nil, fmt.Errorf("unexpected credential type: %s", input.Type)
+	}
+	clientDataRaw, err := DecodeBase64URL(input.Response.ClientDataJSON)
+	if err != nil {
+		return nil, fmt.Errorf("decode client data: %w", err)
+	}
+	if err := validateWebAuthnClientData(clientDataRaw, "webauthn.create", challenge, expectedOrigin); err != nil {
+		return nil, err
+	}
+	attestationObject, err := DecodeBase64URL(input.Response.AttestationObject)
+	if err != nil {
+		return nil, fmt.Errorf("decode attestation object: %w", err)
+	}
+	parsed, err := parseCBORExact(attestationObject)
+	if err != nil {
+		return nil, fmt.Errorf("parse attestation object: %w", err)
+	}
+	attestationMap, ok := parsed.(map[any]any)
+	if !ok {
+		return nil, errors.New("attestation object is not a map")
+	}
+	authData, ok := attestationMap["authData"].([]byte)
+	if !ok {
+		return nil, errors.New("attestation authData is missing")
+	}
+	credential, err := parseAttestedCredentialData(authData, rpID)
+	if err != nil {
+		return nil, err
+	}
+	rawID := strings.TrimSpace(input.RawID)
+	if rawID == "" {
+		rawID = strings.TrimSpace(input.ID)
+	}
+	if rawID != "" && rawID != credential.CredentialID {
+		return nil, errors.New("credential raw id does not match attested credential id")
+	}
+	return credential, nil
+}
+
+func VerifyWebAuthnAssertion(input WebAuthnLoginAssertion, challenge string, rpID string, expectedOrigin string, credential WebAuthnCredentialMaterial) (uint32, error) {
+	if input.Type != "public-key" {
+		return 0, fmt.Errorf("unexpected credential type: %s", input.Type)
+	}
+	rawID := strings.TrimSpace(input.RawID)
+	if rawID == "" {
+		rawID = strings.TrimSpace(input.ID)
+	}
+	if rawID != credential.CredentialID {
+		return 0, errors.New("credential id does not match")
+	}
+	clientDataRaw, err := DecodeBase64URL(input.Response.ClientDataJSON)
+	if err != nil {
+		return 0, fmt.Errorf("decode client data: %w", err)
+	}
+	if err := validateWebAuthnClientData(clientDataRaw, "webauthn.get", challenge, expectedOrigin); err != nil {
+		return 0, err
+	}
+	authData, err := DecodeBase64URL(input.Response.AuthenticatorData)
+	if err != nil {
+		return 0, fmt.Errorf("decode authenticator data: %w", err)
+	}
+	signature, err := DecodeBase64URL(input.Response.Signature)
+	if err != nil {
+		return 0, fmt.Errorf("decode signature: %w", err)
+	}
+	signCount, err := parseAssertionAuthenticatorData(authData, rpID, credential.SignCount)
+	if err != nil {
+		return 0, err
+	}
+	xBytes, err := DecodeBase64URL(credential.PublicKeyX)
+	if err != nil {
+		return 0, fmt.Errorf("decode public key x: %w", err)
+	}
+	yBytes, err := DecodeBase64URL(credential.PublicKeyY)
+	if err != nil {
+		return 0, fmt.Errorf("decode public key y: %w", err)
+	}
+	publicKey := ecdsa.PublicKey{Curve: elliptic.P256(), X: new(big.Int).SetBytes(xBytes), Y: new(big.Int).SetBytes(yBytes)}
+	if !publicKey.Curve.IsOnCurve(publicKey.X, publicKey.Y) {
+		return 0, errors.New("webauthn public key is not on P-256 curve")
+	}
+	clientDataHash := sha256.Sum256(clientDataRaw)
+	verifyData := append(append([]byte{}, authData...), clientDataHash[:]...)
+	digest := sha256.Sum256(verifyData)
+	if !ecdsa.VerifyASN1(&publicKey, digest[:], signature) {
+		return 0, errors.New("invalid webauthn signature")
+	}
+	return signCount, nil
+}
+
+func validateWebAuthnClientData(raw []byte, expectedType string, challenge string, expectedOrigin string) error {
+	var clientData WebAuthnClientData
+	if err := json.Unmarshal(raw, &clientData); err != nil {
+		return fmt.Errorf("parse client data: %w", err)
+	}
+	if clientData.Type != expectedType {
+		return fmt.Errorf("unexpected webauthn client data type: %s", clientData.Type)
+	}
+	if clientData.Challenge != challenge {
+		return errors.New("webauthn challenge mismatch")
+	}
+	if expectedOrigin != "" && clientData.Origin != expectedOrigin {
+		return fmt.Errorf("webauthn origin mismatch: %s", clientData.Origin)
+	}
+	return nil
+}
+
+func parseAttestedCredentialData(authData []byte, rpID string) (*WebAuthnParsedCredential, error) {
+	signCount, credentialData, err := parseAuthenticatorDataHeader(authData, rpID, true, 0)
+	if err != nil {
+		return nil, err
+	}
+	if len(credentialData) < 18 {
+		return nil, errors.New("attested credential data is too short")
+	}
+	offset := 16
+	credentialIDLength := int(binary.BigEndian.Uint16(credentialData[offset : offset+2]))
+	offset += 2
+	if credentialIDLength <= 0 || len(credentialData) < offset+credentialIDLength {
+		return nil, errors.New("invalid credential id length")
+	}
+	credentialID := credentialData[offset : offset+credentialIDLength]
+	offset += credentialIDLength
+	publicKeyRaw := credentialData[offset:]
+	publicKey, err := parseCBOR(publicKeyRaw)
+	if err != nil {
+		return nil, fmt.Errorf("parse credential public key: %w", err)
+	}
+	publicKeyMap, ok := publicKey.(map[any]any)
+	if !ok {
+		return nil, errors.New("credential public key is not a map")
+	}
+	kty, err := coseInt(publicKeyMap, 1)
+	if err != nil {
+		return nil, err
+	}
+	alg, err := coseInt(publicKeyMap, 3)
+	if err != nil {
+		return nil, err
+	}
+	crv, err := coseInt(publicKeyMap, -1)
+	if err != nil {
+		return nil, err
+	}
+	if kty != 2 || alg != -7 || crv != 1 {
+		return nil, fmt.Errorf("unsupported COSE key: kty=%d alg=%d crv=%d", kty, alg, crv)
+	}
+	x, err := coseBytes(publicKeyMap, -2)
+	if err != nil {
+		return nil, err
+	}
+	y, err := coseBytes(publicKeyMap, -3)
+	if err != nil {
+		return nil, err
+	}
+	if !elliptic.P256().IsOnCurve(new(big.Int).SetBytes(x), new(big.Int).SetBytes(y)) {
+		return nil, errors.New("credential public key is not on P-256 curve")
+	}
+	return &WebAuthnParsedCredential{
+		CredentialID: EncodeBase64URL(credentialID),
+		PublicKeyX:   EncodeBase64URL(x),
+		PublicKeyY:   EncodeBase64URL(y),
+		SignCount:    signCount,
+	}, nil
+}
+
+func parseAssertionAuthenticatorData(authData []byte, rpID string, previousSignCount uint32) (uint32, error) {
+	signCount, _, err := parseAuthenticatorDataHeader(authData, rpID, false, previousSignCount)
+	if err != nil {
+		return 0, err
+	}
+	return signCount, nil
+}
+
+func parseAuthenticatorDataHeader(authData []byte, rpID string, requireAttestedData bool, previousSignCount uint32) (uint32, []byte, error) {
+	if len(authData) < 37 {
+		return 0, nil, errors.New("authenticator data is too short")
+	}
+	expectedRPIDHash := sha256.Sum256([]byte(rpID))
+	if string(authData[:32]) != string(expectedRPIDHash[:]) {
+		return 0, nil, errors.New("rp id hash mismatch")
+	}
+	flags := authData[32]
+	if flags&0x01 == 0 {
+		return 0, nil, errors.New("user presence flag is missing")
+	}
+	signCount := binary.BigEndian.Uint32(authData[33:37])
+	if previousSignCount > 0 && signCount > 0 && signCount <= previousSignCount {
+		return 0, nil, errors.New("authenticator sign count did not increase")
+	}
+	if requireAttestedData && flags&0x40 == 0 {
+		return 0, nil, errors.New("attested credential data flag is missing")
+	}
+	return signCount, authData[37:], nil
+}
+
+func coseInt(m map[any]any, key int64) (int64, error) {
+	value, ok := m[key]
+	if !ok {
+		return 0, fmt.Errorf("missing COSE key %d", key)
+	}
+	intValue, ok := value.(int64)
+	if !ok {
+		return 0, fmt.Errorf("invalid COSE key %d", key)
+	}
+	return intValue, nil
+}
+
+func coseBytes(m map[any]any, key int64) ([]byte, error) {
+	value, ok := m[key]
+	if !ok {
+		return nil, fmt.Errorf("missing COSE key %d", key)
+	}
+	bytesValue, ok := value.([]byte)
+	if !ok || len(bytesValue) == 0 {
+		return nil, fmt.Errorf("invalid COSE key %d", key)
+	}
+	return bytesValue, nil
+}
+
+func parseCBOR(data []byte) (any, error) {
+	reader := cborReader{data: data}
+	value, err := reader.read()
+	if err != nil {
+		return nil, err
+	}
+	return value, nil
+}
+
+func parseCBORExact(data []byte) (any, error) {
+	reader := cborReader{data: data}
+	value, err := reader.read()
+	if err != nil {
+		return nil, err
+	}
+	if reader.pos != len(data) {
+		return nil, errors.New("trailing cbor data")
+	}
+	return value, nil
+}
+
+type cborReader struct {
+	data []byte
+	pos  int
+}
+
+func (r *cborReader) read() (any, error) {
+	if r.pos >= len(r.data) {
+		return nil, errors.New("unexpected cbor eof")
+	}
+	initial := r.data[r.pos]
+	r.pos++
+	major := initial >> 5
+	additional := initial & 0x1f
+	length, err := r.readLength(additional)
+	if err != nil {
+		return nil, err
+	}
+	switch major {
+	case 0:
+		return int64(length), nil
+	case 1:
+		return -1 - int64(length), nil
+	case 2:
+		return r.readBytes(length)
+	case 3:
+		raw, err := r.readBytes(length)
+		if err != nil {
+			return nil, err
+		}
+		return string(raw), nil
+	case 4:
+		out := make([]any, 0, length)
+		for i := uint64(0); i < length; i++ {
+			item, err := r.read()
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, item)
+		}
+		return out, nil
+	case 5:
+		out := make(map[any]any, length)
+		for i := uint64(0); i < length; i++ {
+			key, err := r.read()
+			if err != nil {
+				return nil, err
+			}
+			value, err := r.read()
+			if err != nil {
+				return nil, err
+			}
+			out[key] = value
+		}
+		return out, nil
+	case 7:
+		switch additional {
+		case 20:
+			return false, nil
+		case 21:
+			return true, nil
+		case 22, 23:
+			return nil, nil
+		default:
+			return nil, fmt.Errorf("unsupported cbor simple value: %d", additional)
+		}
+	default:
+		return nil, fmt.Errorf("unsupported cbor major type: %d", major)
+	}
+}
+
+func (r *cborReader) readLength(additional byte) (uint64, error) {
+	switch {
+	case additional < 24:
+		return uint64(additional), nil
+	case additional == 24:
+		if r.pos+1 > len(r.data) {
+			return 0, errors.New("unexpected cbor eof")
+		}
+		value := r.data[r.pos]
+		r.pos++
+		return uint64(value), nil
+	case additional == 25:
+		if r.pos+2 > len(r.data) {
+			return 0, errors.New("unexpected cbor eof")
+		}
+		value := binary.BigEndian.Uint16(r.data[r.pos : r.pos+2])
+		r.pos += 2
+		return uint64(value), nil
+	case additional == 26:
+		if r.pos+4 > len(r.data) {
+			return 0, errors.New("unexpected cbor eof")
+		}
+		value := binary.BigEndian.Uint32(r.data[r.pos : r.pos+4])
+		r.pos += 4
+		return uint64(value), nil
+	case additional == 27:
+		if r.pos+8 > len(r.data) {
+			return 0, errors.New("unexpected cbor eof")
+		}
+		value := binary.BigEndian.Uint64(r.data[r.pos : r.pos+8])
+		r.pos += 8
+		return value, nil
+	default:
+		return 0, fmt.Errorf("unsupported cbor additional info: %d", additional)
+	}
+}
+
+func (r *cborReader) readBytes(length uint64) ([]byte, error) {
+	if length > uint64(len(r.data)-r.pos) {
+		return nil, errors.New("unexpected cbor eof")
+	}
+	out := r.data[r.pos : r.pos+int(length)]
+	r.pos += int(length)
+	return out, nil
+}