90 lines
2.3 KiB
Go
90 lines
2.3 KiB
Go
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package auth
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"encoding/gob"
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"fmt"
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"io"
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"time"
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)
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// Session holds the claims we care about after a successful OIDC login.
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type Session struct {
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Subject string // email or sub claim
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Groups []string // groups claim from Authelia
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IssuedAt time.Time // when we issued this session cookie
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}
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// seal gob-encodes v and AES-256-GCM encrypts it into a base64url string.
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func seal(key [32]byte, v any) (string, error) {
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var buf bytes.Buffer
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if err := gob.NewEncoder(&buf).Encode(v); err != nil {
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return "", fmt.Errorf("seal gob: %w", err)
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}
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block, err := aes.NewCipher(key[:])
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if err != nil {
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return "", err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return "", err
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}
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nonce := make([]byte, gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return "", err
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}
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// nonce || ciphertext+tag
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ciphertext := gcm.Seal(nonce, nonce, buf.Bytes(), nil)
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return base64.RawURLEncoding.EncodeToString(ciphertext), nil
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}
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// open decrypts and gob-decodes a value produced by seal into v.
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// Returns an error if the value was tampered with or sealed with a different key.
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func open(key [32]byte, encoded string, v any) error {
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data, err := base64.RawURLEncoding.DecodeString(encoded)
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if err != nil {
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return fmt.Errorf("open base64: %w", err)
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}
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block, err := aes.NewCipher(key[:])
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if err != nil {
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return err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return err
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}
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if len(data) < gcm.NonceSize() {
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return fmt.Errorf("sealed value too short")
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}
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nonce, ciphertext := data[:gcm.NonceSize()], data[gcm.NonceSize():]
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plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return fmt.Errorf("open decrypt: %w", err)
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}
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if err := gob.NewDecoder(bytes.NewReader(plaintext)).Decode(v); err != nil {
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return fmt.Errorf("open gob: %w", err)
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}
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return nil
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}
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// EncodeSession serialises and encrypts a Session into a cookie value.
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func EncodeSession(s Session, key [32]byte) (string, error) {
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return seal(key, s)
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}
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// DecodeSession decrypts and deserialises a cookie value produced by EncodeSession.
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func DecodeSession(encoded string, key [32]byte) (Session, error) {
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var s Session
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if err := open(key, encoded, &s); err != nil {
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return Session{}, err
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}
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return s, nil
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}
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