git feature

server/internal/auth/github_token.go

@@ -0,0 +1,90 @@
+package auth
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"io"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type GitHubOAuthStateClaims struct {
+	StaffID uint `json:"staffId"`
+	jwt.RegisteredClaims
+}
+
+func IssueGitHubOAuthState(staffID uint) (string, error) {
+	claims := GitHubOAuthStateClaims{
+		StaffID: staffID,
+		RegisteredClaims: jwt.RegisteredClaims{
+			ExpiresAt: jwt.NewNumericDate(time.Now().Add(15 * time.Minute)),
+			IssuedAt:  jwt.NewNumericDate(time.Now()),
+		},
+	}
+	t := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	return t.SignedString([]byte(JWTSecret()))
+}
+
+func ParseGitHubOAuthState(state string) (uint, error) {
+	t, err := jwt.ParseWithClaims(state, &GitHubOAuthStateClaims{}, func(t *jwt.Token) (any, error) {
+		return []byte(JWTSecret()), nil
+	})
+	if err != nil {
+		return 0, err
+	}
+	claims, ok := t.Claims.(*GitHubOAuthStateClaims)
+	if !ok || !t.Valid || claims.StaffID == 0 {
+		return 0, errors.New("invalid oauth state")
+	}
+	return claims.StaffID, nil
+}
+
+func tokenCipher() (cipher.AEAD, error) {
+	sum := sha256.Sum256([]byte(JWTSecret()))
+	block, err := aes.NewCipher(sum[:])
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewGCM(block)
+}
+
+func EncryptSecret(plain string) (string, error) {
+	if plain == "" {
+		return "", errors.New("empty secret")
+	}
+	gcm, err := tokenCipher()
+	if err != nil {
+		return "", err
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", err
+	}
+	sealed := gcm.Seal(nonce, nonce, []byte(plain), nil)
+	return base64.StdEncoding.EncodeToString(sealed), nil
+}
+
+func DecryptSecret(encoded string) (string, error) {
+	raw, err := base64.StdEncoding.DecodeString(encoded)
+	if err != nil {
+		return "", err
+	}
+	gcm, err := tokenCipher()
+	if err != nil {
+		return "", err
+	}
+	if len(raw) < gcm.NonceSize() {
+		return "", errors.New("ciphertext too short")
+	}
+	nonce, ciphertext := raw[:gcm.NonceSize()], raw[gcm.NonceSize():]
+	plain, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return "", err
+	}
+	return string(plain), nil
+}