解密在命令行使用Ruby生成的盐化AES文件 [英] Decrypting salted AES file generated on command line with Ruby

问题描述

我想解密一个ruby 2.1脚本中的文本文件，该文件以前是使用OpenSSL的命令行工具加密的：
openssl enc -aes-256-cbc -a -salt -in my_file

I would like to decrypt a text file within a ruby 2.1 script which was previously encrypted using OpenSSL's commandline tools: openssl enc -aes-256-cbc -a -salt -in my_file

如命令中所示，该文件是AES-256-CBC加密，盐化和base64编码。

As seen in the command, the file is AES-256-CBC encrypted, salted and base64 encoded.

密码是已知的，但不是IV和密钥，它们是遵循此代码片段所需的，取自 ruby​​ documentation ：

The password is known, but not the IV nor the key, which are required to follow this code snippet, taken from the ruby documentation:

decipher = OpenSSL::Cipher::AES.new 256, :CBC
decipher.decrypt
decipher.key = key
decipher.iv = iv

plain = decipher.update(encrypted_text) + decipher.final

在尝试找到答案时，我发现了gem AESCrypt gem据推测可以简化加密和解密，但目前发布的版本与ruby 2.1不兼容。
看看它的源代码，我发现键是通过消化密码获取， IV是

While trying to find an answer, I found the gem AESCrypt gem which supposedly simplifies en- and decrypting, yet the currently released version is not compatible with ruby 2.1. Looking at it's source code, I found that the key was retrieved by digesting the password, and the IV is just left as nil.

所以我试图得到以下运行：

So I tried to get the following running:

encoded_and_encrypted_text = File.read my_file_path
encrypted_text = Base64.decode64 encoded_and_encrypted_text.to_s.strip

decipher = OpenSSL::Cipher::AES.new 256, :CBC
decipher.decrypt

decipher.key = OpenSSL::Digest::SHA256.new(my_password).digest

plain_text = decipher.update(encrypted_text) + decipher.final

但这会导致 OpenSSL :: Cipher :: CipherError：bad decrypt 。

我需要以某种方式专门处理文件被盐化？我已阅读 OpenSSL文档中的 enc 函数，如果在加密文件时未指定IV，则从密码生成IV。我需要手动重建IV吗？

Do I need to somehow specifically handle that the file is salted? I have read in the OpenSSL documentation for the enc function that the IV, if not specified while encrypting the file, is generated from the password. Do I need to manually reconstruct the IV somehow?

任何建议都非常感激：）

Any advice would be highly appreciated :)

推荐答案

OpenSSL使用自定义头和密钥导出例程。 Security.SE对标头和文档 EVP_BytesToKey 描述了密钥派生。

OpenSSL uses a custom header and key derivation routine. Security.SE has a good description of the header and the docs for EVP_BytesToKey describe the key derivation.

我们可以修改你的代码以使用这个奇怪的和有点破碎的密钥推导如下：

We can modify your code to use this weird and somewhat broken key derivation as follows:

encoded_and_encrypted_text = File.read my_file_path
encrypted_text = Base64.decode64 encoded_and_encrypted_text.to_s.strip

header = encrypted_text[0,8]
salt = encrypted_text[8,8]
payload = encrypted_text[16..-1]

decipher = OpenSSL::Cipher::AES.new 256, :CBC
decipher.decrypt

D_1 = OpenSSL::Digest::MD5.new(my_password + salt).digest
D_2 = OpenSSL::Digest::MD5.new(D_1 + my_password + salt).digest
D_3 = OpenSSL::Digest::MD5.new(D_2 + my_password + salt).digest

decipher.key = (D_1 + D_2)
decipher.iv = D_3

plain_text = decipher.update(payload) + decipher.final

这篇关于解密在命令行使用Ruby生成的盐化AES文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！