可以从脚本执行Python字节码吗？ [英] Possible to execute Python bytecode from a script?

问题描述

假设我有一个正在运行的CPython会话，

Say I have a running CPython session,

是否可以运行数据（字节）直接从 pyc 文件中删除？
（不必在磁盘上存储数据，也不必编写临时pyc文件）

Is there a way to run the data (bytes) from a pyc file directly? (without having the data on-disk necessarily, and without having to write a temporary pyc file)

示例脚本显示一个简单的用例：

Example script to show a simple use-case:

if foo:
    # Intentionally ambiguous, since the data source
    # is a detail and answers shouldn't depend this detail.
    data = read_data_from_somewhere()
else:
    data = open("bar.pyc", 'rb').read()

assert(type(data) is bytes)

code = bytes_to_code(data)

# call a method from the loaded code
code.call_function()

---

精确使用并不重要，但可以动态生成代码并通过网络复制到execute是一个用例（出于考虑这个问题的目的）。

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Exact use isn't important, but generating code dynamically and copying over a network to execute is one use-case (for the purpose of thinking about this question).

以下是一些示例用例，这让我很好奇如何做到：

Here are some example use-cases, which made me curious to know how this can be done:

• 检查Python脚本中是否存在恶意代码。
  单个命令可以访问隐藏在二进制数据中的大量代码，该命令将是什么样？


• 动态生成代码并将其缓存以供重用（不一定在磁盘，例如可以使用数据库。）


• 能够将预编译的字节码发送到进程，控制应用程序w hich为例如嵌入Python。

• Checking Python scripts for malicious code.
  If a single command can access a larger body of code hidden in binary data, what would that command look like?
• Dynamically generate code and cache it for re-use (not necessarily on disk, could use a data-base for example).
• Ability to send pre-compiled byte-code to a process, control an application which embeds Python for eg.

推荐答案

有没有一种方法可以直接从pyc文件运行数据？

Is there a way to run the data from a pyc file directly?

可以使用元帅

import marshal
bytes = marshal.dumps(eggs)

字节可以转换回代码对象

the bytes can be converted back to a code object

eggs = marshal.loads(bytes)
exec(eggs)

一个 pyc 文件是带有标头的封送代码对象

A pyc file is a marshaled code object with a header

对于Python3，标头为需要跳过12个字节，其余数据可以通过 marshal.loads 读取。

For Python3, the header is 12 bytes which need to be skipped, the remaining data can be read via marshal.loads.

请参见内德·巴切尔德的博客文章：

在简单级别上，.pyc文件是二进制文件仅包含三个内容：

At the simple level, a .pyc file is a binary file containing only three things:

• 一个四字节的幻数，


• 一个四字节的修改时间戳记和


• 编组代码对象。

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注意，该链接引用了Python2，但在Python3中几乎相同， pyc 标头大小仅为12个字节，而不是8个字节

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Note, the link references Python2, but its almost the same in Python3, the pyc header size is just 12 instead of 8 bytes.

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