feat(all): split client tooling and add OAuth server login

go/internal/server/dbcrypt/pages.go

@@ -0,0 +1,66 @@
+// Package dbcrypt implements the page cipher used by versioned GameData
+// SQLite archives. Client resource patching owns a separate copy so the pure
+// server dependency graph never imports internal/client.
+package dbcrypt
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/hmac"
+	"crypto/sha1"
+	"fmt"
+)
+
+const PageSize = 4096
+
+var Header = []byte("SQLite format 3\x00")
+
+func DecryptPages(in []byte) ([]byte, error) { return cryptPages(in, false) }
+func EncryptPages(in []byte) ([]byte, error) { return cryptPages(in, true) }
+
+func cryptPages(in []byte, encrypt bool) ([]byte, error) {
+	if len(in) == 0 || len(in)%PageSize != 0 {
+		return nil, fmt.Errorf("dbcrypt: database length %d is not a non-zero multiple of %d", len(in), PageSize)
+	}
+	block, err := aes.NewCipher(deriveKey())
+	if err != nil {
+		return nil, err
+	}
+	out := make([]byte, len(in))
+	for start := 0; start < len(in); start += PageSize {
+		var mode cipher.BlockMode = cipher.NewCBCEncrypter(block, Header)
+		if !encrypt {
+			mode = cipher.NewCBCDecrypter(block, Header)
+		}
+		mode.CryptBlocks(out[start:start+PageSize], in[start:start+PageSize])
+	}
+	return out, nil
+}
+
+func deriveKey() []byte {
+	password := []byte(fmt.Sprintf("%X", sha1.Sum([]byte("spdhdnlwmrpavmtm"))))
+	return pbkdf2SHA1(password, Header, 2010, 32)
+}
+
+func pbkdf2SHA1(password, salt []byte, iterations, length int) []byte {
+	var result []byte
+	for block := uint32(1); len(result) < length; block++ {
+		message := append(append([]byte{}, salt...), byte(block>>24), byte(block>>16), byte(block>>8), byte(block))
+		u := hmacSHA1(password, message)
+		t := append([]byte{}, u...)
+		for i := 1; i < iterations; i++ {
+			u = hmacSHA1(password, u)
+			for j := range t {
+				t[j] ^= u[j]
+			}
+		}
+		result = append(result, t...)
+	}
+	return result[:length]
+}
+
+func hmacSHA1(key, message []byte) []byte {
+	h := hmac.New(sha1.New, key)
+	_, _ = h.Write(message)
+	return h.Sum(nil)
+}