1 files changed, 117 insertions, 0 deletions
diff --git a/pkg/service/auth.go b/pkg/service/auth.go
new file mode 100644
index 0000000..1fbf4b6
--- /dev/null
+++ b/pkg/service/auth.go
@@ -0,0 +1,117 @@
+package service
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+type (
+	AuthService struct {
+		authRepository authRepository
+	}
+
+	authRepository interface {
+		GetPassphrase() []byte
+		GetBase64AesKey() []byte
+	}
+)
+
+var tokenSeed = []byte("cerrado")
+
+func (a *AuthService) CheckAuth(username, password string) bool {
+	passphrase := a.authRepository.GetPassphrase()
+	pass := []byte(fmt.Sprintf("%s:%s", username, password))
+
+	err := bcrypt.CompareHashAndPassword(passphrase, pass)
+
+	return err == nil
+}
+
+func (a *AuthService) IssueToken() ([]byte, error) {
+	// TODO: do this block only once
+	base := a.authRepository.GetBase64AesKey()
+
+	dbuf, err := base64.StdEncoding.DecodeString(string(base))
+	if err != nil {
+		return nil, err
+	}
+
+	block, err := aes.NewCipher(dbuf)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+
+	ciphertext := gcm.Seal(nonce, nonce, tokenSeed, nil)
+
+	return ciphertext, nil
+}
+
+func (a *AuthService) ValidateToken(token []byte) (bool, error) {
+	base := a.authRepository.GetBase64AesKey()
+
+	dbuf, err := base64.StdEncoding.DecodeString(string(base))
+	if err != nil {
+		return false, err
+	}
+
+	block, err := aes.NewCipher(dbuf)
+	if err != nil {
+		return false, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return false, err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(token) < nonceSize {
+		return false, fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, ciphertext := token[:nonceSize], token[nonceSize:]
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return false, err
+	}
+
+	return bytes.Equal(tokenSeed, plaintext), nil
+}
+
+func GenerateHash(username, password string) (string, error) {
+	passphrase := fmt.Sprintf("%s:%s", username, password)
+	bytes, err := bcrypt.GenerateFromPassword([]byte(passphrase), 14)
+	if err != nil {
+		return "", err
+	}
+
+	return string(bytes), nil
+}
+
+func GenerateAesKey() (string, error) {
+	key := make([]byte, 32)
+
+	_, err := rand.Read(key)
+	if err != nil {
+		return "", err
+	}
+
+	return base64.StdEncoding.EncodeToString(key), nil
+}