feat: book decryption

All credits go to gawgua for his work, tysm.

.gitignore

@@ -1,5 +1,7 @@
 # Akademiya
+/.vscode
 books/
+/bin/*.exe
 
 # Python-generated files
 __pycache__/

.vscode/settings.json

@@ -1,3 +0,0 @@
-{
-    "python.analysis.autoImportCompletions": true
-}

README.md

@@ -13,7 +13,32 @@ pip install git+https://git.tretrauit.me/tretrauit/akademiya
 + [x] Authentication
 + [x] Look up books
 + [x] Borrow books
-+ [x] Download (encrypted) books
++ [x] Download & decrypt books
+
+## Building
+
+1. (Optional) You'll need to build the C++ part first, which can be built using CMake:
+> [!WARNING]
+> If you don't build the decryptor then the download function will not work.
+```bash
+cd decypherer
+mkdir build
+cd build
+# Linux & other platforms (Cross-compile)
+cmake -D CMAKE_BUILD_TYPE=Release ..  
+ninja
+# Windows (You need to have MSVC installed)
+cmake -G "Visual Studio 17" -DCMAKE_GENERATOR_PLATFORM=WIN32 .. 
+cmake --build . --config Release
+```
+
+2. Copy `decypherer.exe` to `bin/` directory.
+3. Run `python -m akademiya` to use as normal. 
+
+
+## Acknowledgements
+
++ [gawgua](https://github.com/gawgua): Reverse engineered the encryption system and wrote the decryption code.
 
 ## License
 

akademiya/__main__.py

@@ -1,6 +1,6 @@
 from getpass import getpass
 from pathlib import Path
-from akademiya import __version__, Client
+from akademiya import __version__, Client, constants, utils
 from traceback import print_exc
 
 # Import readline if available (Unix-like systems)
@@ -29,9 +29,13 @@ def download_book(client: Client, book_id: int):
     if pdf_bytes is None:
         print("The server didn't return any PDF data.")
         return
+    constants.PLATFORM_DIRS.site_cache_path.mkdir(parents=True, exist_ok=True)
+    temp_path = constants.PLATFORM_DIRS.site_cache_path / f"{book.ID}.pdf"
     pdf_path = base_path / f"{book.ID}.pdf"
-    with pdf_path.open("wb") as f:
+    with temp_path.open("wb") as f:
         f.write(pdf_bytes)
+    print("Decrypting book...")
+    utils.decrypt_book_file(temp_path, pdf_path)
     print(f"Book downloaded to '{pdf_path.resolve()}'")
 
 

akademiya/client.py

@@ -4,6 +4,8 @@ from akademiya import constants
 from dataclasses import dataclass
 from urllib.parse import quote
 
+from akademiya.internal import utils
+
 
 @dataclass
 class BookPdf:
@@ -86,11 +88,12 @@ class Client:
         self._session.headers.update({"User-Agent": constants.USER_AGENT})
         self._app_version: float = None
         self.user: User = None
+        self.unique_key = utils.get_unique_key()
         self.set_app_version()
 
     def borrow_book(self, book_id: int):
         rsp = self._session.get(
-            f"{constants.ENDPOINT}/API/cbs/User/Payment/{self.user.token}/{book_id}/{constants.MAGIC_KEY}/1/1/"
+            f"{constants.ENDPOINT}/API/cbs/User/Payment/{self.user.token}/{book_id}/{self.unique_key}/1/1/"
         )
         rsp.raise_for_status()
         result = rsp.json()["BookBorrowsResult"]
@@ -125,7 +128,7 @@ class Client:
             raise Exception("You must borrow the book before downloading the PDF.")
         pdf = book.product_pdf[0]
         rsp = self._session.get(
-            f"{pdf.Url}{book.product_code}/{constants.MAGIC_KEY}/APPWINDOW.1.0/{self.user.token}/{self.user.username}/1/1/"
+            f"{pdf.Url}{book.product_code}/{self.unique_key}/APPWINDOW.1.0/{self.user.token}/{self.user.username}/1/1/"
         )
         rsp.raise_for_status()
         # Comment so Pylance can stfu
@@ -141,10 +144,10 @@ class Client:
     def is_borrowing(self, book_id: int) -> bool:
         """
         Checks if the user is borrowing a book.
-        
+
         Args:
             book_id (int): The ID of the book to check.
-            
+
         Returns:
             bool: True if the user is borrowing the book, False otherwise."""
         rsp = self._session.get(

akademiya/constants.py

@@ -1,3 +1,6 @@
+from platformdirs import PlatformDirs
+
+
 USER_AGENT = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.2; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727; .NET CLR 3.0.30729; .NET CLR 3.5.30729; Tablet PC 2.0)"
 ENDPOINT = "http://bookworm.vnu.edu.vn"
-MAGIC_KEY = "CA72dacfce21b55c"
+PLATFORM_DIRS = PlatformDirs("akademiya", "tretrauit")

akademiya/internal/utils.py

@@ -0,0 +1,74 @@
+# Thanks gawgua for all the reverse engineering work he has done.
+# Almost all codes here are from him, I just made some changes to make it work with my project.
+import hashlib
+import platform
+import random
+from akademiya.constants import PLATFORM_DIRS
+
+
+def _nt_get_window_id():
+    import clr  # type: ignore
+    import hashlib
+
+    clr.AddReference("System.Management")
+    from System.Management import ManagementScope, ManagementObjectSearcher, ObjectQuery  # type: ignore
+
+    def getCSProductUUID():
+        managementScope = ManagementScope("\\\\.\\ROOT\\cimv2")
+        objectQuery = ObjectQuery("SELECT * FROM Win32_ComputerSystemProduct")
+        managementObjectCollection = ManagementObjectSearcher(
+            managementScope, objectQuery
+        ).Get()
+        text = ""
+        for managemenBaseObject in managementObjectCollection:
+            text += managemenBaseObject["UUID"]
+            if text != "" and text.strip() != "":
+                break
+        return text
+
+    def getDiskDriveSerial():
+        managementScope = ManagementScope("\\\\.\\ROOT\\cimv2")
+        objectQuery = ObjectQuery("SELECT * FROM Win32_DiskDrive")
+        managementObjectCollection = ManagementObjectSearcher(
+            managementScope, objectQuery
+        ).Get()
+        text = ""
+        for managemenBaseObject in managementObjectCollection:
+            text += managemenBaseObject["UUID"]
+            if text != "" and text.strip() != "":
+                break
+        return text
+
+    text = getCSProductUUID()
+    if text == "":
+        text = getDiskDriveSerial()
+    text = text.replace("-", "") + "WINDOWID"
+    return hashlib.md5(text.encode("utf-8")).hexdigest()[0:16]
+
+
+def calculate_window_id():
+    PLATFORM_DIRS.site_data_path.mkdir(parents=True, exist_ok=True)
+    if PLATFORM_DIRS.site_data_path.joinpath("window_id").is_file():
+        return PLATFORM_DIRS.site_data_path.joinpath("window_id").read_text().strip()
+    else:
+        result: str = ""
+        if platform.system() == "Windows":
+            result = _nt_get_window_id()
+        else:
+            result = random.randbytes(16).hex()[0:16]
+        PLATFORM_DIRS.site_data_path.joinpath("window_id").write_text(result)
+        return result
+
+
+def calculate_serial():
+    text = calculate_window_id() + "SERIAL"
+    return hashlib.md5(text.encode("utf-8")).hexdigest()[0:16]
+
+
+def get_unique_key():
+    t = calculate_window_id()
+    t2 = calculate_serial()
+    t4 = f"{t}#{t2}#{t2}"
+    t6 = "CA" + hashlib.md5(t4.encode("utf-8")).hexdigest()[-10:]
+    t8 = hashlib.md5(t6.encode("utf-8")).hexdigest()[-4:]
+    return t6 + t8

akademiya/utils.py

@@ -0,0 +1,32 @@
+from pathlib import Path
+from subprocess import call
+from shutil import move, copy
+from os import PathLike
+from random import randint
+from akademiya.constants import PLATFORM_DIRS
+from akademiya.internal import utils as _utils
+
+
+def decrypt_book_file(book_file: PathLike, out_path: PathLike):
+    """
+    Decrypts the book file, only works if the book is downloaded by this client.
+
+    Args:
+        book_file (PathLike): The path to the encrypted book file.
+
+    Returns:
+        bytes: The decrypted book data.
+    """
+    cache_path = PLATFORM_DIRS.site_cache_path
+    cache_path.mkdir(exist_ok=True)
+    random_name_input = str(randint(100000, 999999))
+    input_file = cache_path.joinpath(random_name_input)
+    random_name_output = str(randint(100000, 999999))
+    output_file = cache_path.joinpath(random_name_output)
+    copy(book_file, input_file)
+    window_id = _utils.calculate_window_id()
+    retcode = call(["./bin/decypherer.exe", window_id, str(input_file), str(output_file)])
+    Path(input_file).unlink()
+    if retcode != 0:
+        raise RuntimeError("Failed to decrypt the book file.")
+    move(output_file, out_path)

decypherer/.gitignore

@@ -0,0 +1,34 @@
+### C++ template
+cmake-*/
+.idea/
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+

decypherer/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.30)
+project(decypherer)
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_FLAGS -m32)
+
+add_executable(decypherer main.cpp)

decypherer/main.cpp

@@ -0,0 +1,79 @@
+// Again, this is ported C++ code from gawgua's original Python code.
+// All credits go to him, I just used DeepSeek to convert it to C++.
+
+#include <iostream>
+#include <format>
+#include <Windows.h>
+#include <libloaderapi.h>
+
+// MuPDF structure definition
+struct pdf_write_options {
+    int do_incremental;
+    int do_pretty;
+    int do_ascii;
+    int do_compress;
+    int do_compress_images;
+    int do_compress_fonts;
+    int do_decompress;
+    int do_garbage;
+    int do_linear;
+    int do_clean;
+    int do_sanitize;
+    int do_appearance;
+    int do_encrypt;
+    int dont_regenerate_id;
+    int permissions;
+    char opwd_utf8[128];
+    char upwd_utf8[128];
+    int do_snapshot;
+    int do_preserve_metadata;
+    int do_use_objstms;
+    int compression_effort;
+};
+
+int main(const int argc, char* argv[])
+{
+	if (argc < 3) {
+		std::cout << "usage: decypherer.exe <window id> <path> <output>" << std::endl;
+		return 0;
+	}
+    // Arg 1
+    auto window_id = argv[1];
+    // Arg 2
+    auto path = argv[2];
+    // Arg 3
+	const auto output = argv[3];
+
+    const HMODULE mupdf = LoadLibraryA("mupdf-exp-dll-x86.dll");
+    if (mupdf == nullptr) {
+		std::cout << "error: failed to load MuPDF library" << std::endl;
+		return 1;
+    }
+
+    // Define function pointers
+    const auto fz_new_context_imp = reinterpret_cast<void* (*)(void *, void *, unsigned int, const char *)>(GetProcAddress(mupdf, "fz_new_context_imp"));
+    const auto fz_register_document_handlers = reinterpret_cast<void* (*)(void *)>(GetProcAddress(mupdf, "fz_register_document_handlers"));
+    const auto fz_open_document_w = reinterpret_cast<void* (*)(void *, const wchar_t *)>(GetProcAddress(mupdf, "fz_open_document_w"));
+    const auto pdf_save_document = reinterpret_cast<void(*)(void *, void *, const char *, pdf_write_options *)>(GetProcAddress(mupdf, "pdf_save_document"));
+
+    // Build argument path
+    auto arg_path_str = std::format("#OCB#{}#{}", window_id, path);
+    const std::wstring arg_path(arg_path_str.begin(), arg_path_str.end());
+
+    // Create context
+    void* ctx = fz_new_context_imp(nullptr, nullptr, 268435456, "1.16.1");
+    fz_register_document_handlers(ctx);
+
+    // Open document
+    void* doc = fz_open_document_w(ctx, arg_path.c_str());
+
+    // Set save options
+    pdf_write_options opts = {
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, ~0,
+        {}, {}, 0, 0, 0, 0
+    };
+
+    // Save document
+    pdf_save_document(ctx, doc, output, &opts);
+    FreeLibraryAndExitThread(mupdf, 0);
+}

pyproject.toml

@@ -1,9 +1,15 @@
 [project]
 name = "akademiya"
 version = "0.1.0"
-description = "Add your description here"
+description = "Unofficial API client written in Python for a certain book library."
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
+    "platformdirs>=4.3.6",
     "requests>=2.32.3",
 ]
+
+[project.optional-dependencies]
+win = [
+    "pythonnet>=3.0.5",
+]

uv.lock

@@ -6,11 +6,21 @@ name = "akademiya"
 version = "0.1.0"
 source = { virtual = "." }
 dependencies = [
+    { name = "platformdirs" },
     { name = "requests" },
 ]
 
+[package.optional-dependencies]
+win = [
+    { name = "pythonnet" },
+]
+
 [package.metadata]
-requires-dist = [{ name = "requests", specifier = ">=2.32.3" }]
+requires-dist = [
+    { name = "platformdirs", specifier = ">=4.3.6" },
+    { name = "pythonnet", marker = "extra == 'win'", specifier = ">=3.0.5" },
+    { name = "requests", specifier = ">=2.32.3" },
+]
 
 [[package]]
 name = "certifi"
@@ -21,6 +31,28 @@ wheels = [
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 ]
 
+[[package]]
+name = "cffi"
+version = "1.17.1"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pycparser" },
+]
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+]
+
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 version = "3.4.0"
@@ -45,6 +77,18 @@ wheels = [
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+[[package]]
+name = "clr-loader"
+version = "0.2.7.post0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "cffi" },
+]
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+]
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+version = "4.3.6"
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