Glibc 的哈希函数

Question

我一直在尝试加密 Swift 中的字符串，但我希望它在 linux 下工作。类似下面代码的答案（取自 these 不起作用，因为它们依赖于 iOS 或 OSx 库：

func sha256(data : Data) -> Data {
    var hash = [UInt8](repeating: 0,  count: Int(CC_SHA256_DIGEST_LENGTH))
    data.withUnsafeBytes {
        _ = CC_SHA256([=10=], CC_LONG(data.count), &hash)
    }
    return Data(bytes: hash)
}

如何在 linux 中使用 Glibc 来完成？

Answer 1

glibc 中有一个 crypt 库，see manpage。
您需要包括：#include <crypt.h>.

您要使用的函数是：

char *crypt(const char *key, const char *salt);

根据该联机帮助页，SHA-256 算法从 glibc 2.7 开始集成，并通过 salt 参数选择：

The glibc2 version of this function supports additional encryption
algorithms.

If salt is a character string starting with the characters "$id$"
followed by a string terminated by "$":

       $id$salt$encrypted

then instead of using the DES machine, id identifies the encryption
method used and this then determines how the rest of the password
string is interpreted.  The following values of id are supported:

       ID  | Method
       ─────────────────────────────────────────────────────────
       1   | MD5
       2a  | Blowfish (not in mainline glibc; added in some
           | Linux distributions)
       5   | SHA-256 (since glibc 2.7)
       6   | SHA-512 (since glibc 2.7)

So $salt$encrypted is an SHA-256 encoded password and
$salt$encrypted is an SHA-512 encoded one.

"salt" stands for the up to 16 characters following "$id$" in the
salt.  The encrypted part of the password string is the actual
computed password.  The size of this string is fixed:

MD5     | 22 characters
SHA-256 | 43 characters
SHA-512 | 86 characters

The characters in "salt" and "encrypted" are drawn from the set
[a-zA-Z0-9./].  In the MD5 and SHA implementations the entire key is
significant (instead of only the first 8 bytes in DES).

在this official GNU page and this wikipedia article上有解释和例子：

SHA-256 的 salt 参数示例：
ks3nNEqv31FX.F$gdEoLFsCRsn/WRN3wxUnzfeZLoooVlzeF4WjLomTRFD

Glibc 的哈希函数

Hash function with Glibc

linux

glibc

swift