Haskell 绑定到 libsodium 的外部函数接口 - 错误签名

Question

我正在对 libsodium 进行绑定，因此我可以在 Haskell 中签署字节串，但签名与 C 为相同消息和密钥创建的签名不匹配。

我在 libsodium 中绑定到这个函数：

int crypto_sign_detached(unsigned char *sig, unsigned long long *siglen,
                         const unsigned char *m, unsigned long long mlen,
                         const unsigned char *sk);

文档说：

The crypto_sign_detached() function signs the message m whose length is mlen bytes, using the secret key sk, and puts the signature into sig, which can be up to crypto_sign_BYTES long.

The actual length of the signature is put into siglen if siglen is not NULL.

It is safe to ignore siglen and always consider a signature as crypto_sign_BYTES bytes long: shorter signatures will be transparently padded with zeros if necessary.

crypto_sign_BYTES 是 64.

这里是 Haskell 代码（抱歉有点长，但越短越好）：

{-# LANGUAGE OverloadedStrings #-}
module Main where

import qualified Data.ByteString as B
import qualified Data.ByteString.Base16 as B16
import qualified Data.ByteString.Internal as Bi
import qualified Foreign as F
import qualified Foreign.C.Types as T
import System.IO.Unsafe (unsafePerformIO)

secretkey :: B.ByteString
secretkey = B.pack [0x34, 0xEB, 0xA3, 0x9F, 0xC5, 0xA1, 0xB4, 0x1D,
                    0x64, 0x12, 0xCE, 0xC3, 0xD2, 0x0A, 0x7F, 0xA8,
                    0x24, 0x24, 0x2A, 0xDC, 0x1E, 0x6C, 0x04, 0x48,
                    0xCE, 0x91, 0xB3, 0xC4, 0x84, 0xCC, 0x7A, 0xC6]

main :: IO ()
main = do
    status <- c_sodium_init
    case status of
      0 ->
        case sign "test" secretkey of
          Right sig -> do
            print $ B16.encode sig
          Left err -> print err
      _ -> putStrLn "Could not initialize."

crypto_sign_BYTES :: Int
crypto_sign_BYTES = 64

packCString :: Int -> F.Ptr F.Word8 -> IO B.ByteString
packCString len cstr = create len $ \p -> Bi.memcpy p cstr len

create :: Int -> (F.Ptr F.Word8 -> IO ()) -> IO B.ByteString
create l f = do
  fp <- Bi.mallocByteString l
  F.withForeignPtr fp f
  return $! Bi.PS fp 0 l

foreign import ccall unsafe "sodium.h crypto_sign_detached"
  c_crypto_sign_detached
    :: CUString
    -> F.Ptr T.CULLong
    -> CUString
    -> T.CULLong
    -> CUString
    -> IO T.CInt

sign :: B.ByteString -> B.ByteString -> Either Int B.ByteString
sign message secretKey = unsafePerformIO $
  useAsCString message $ \messagePtr ->
  useAsCString secretKey $ \secretKeyPtr ->
  F.allocaBytes crypto_sign_BYTES $ \sig -> do
    status <- c_crypto_sign_detached
                  sig
                  F.nullPtr
                  messagePtr
                  (fromIntegral $ B.length message)
                  secretKeyPtr
    case status of
      0 -> do
        packed <- packCString crypto_sign_BYTES $ F.castPtr sig
        return $ Right packed
      errCode -> return $ Left $ fromIntegral errCode

foreign import ccall unsafe "sodium.h sodium_init"
  c_sodium_init :: IO T.CInt

type CUString = F.Ptr T.CUChar

useAsCString :: B.ByteString -> (CUString -> IO a) -> IO a
useAsCString (Bi.PS fp o l) action =
  F.allocaBytes (l+1) $ \buf ->
    F.withForeignPtr fp $ \p -> do
      Bi.memcpy buf (p `F.plusPtr` o) (fromIntegral l)
      F.pokeByteOff buf l (0::F.Word8)
      action (F.castPtr buf)

C代码如下：

#include <sodium.h>
#include <stdio.h>

int main (void)
{
    if (sodium_init() < 0) {
        printf("could not initialize");
    }

    unsigned char message[4] = "test";
    unsigned char sk[32] = {0x34, 0xEB, 0xA3, 0x9F, 0xC5, 0xA1, 0xB4, 
                            0x1D, 0x64, 0x12, 0xCE, 0xC3, 0xD2, 0x0A,
                            0x7F, 0xA8, 0x24, 0x24, 0x2A, 0xDC, 0x1E,
                            0x6C, 0x04, 0x48, 0xCE, 0x91, 0xB3, 0xC4, 
                            0x84, 0xCC, 0x7A, 0xC6};

    unsigned char sig[crypto_sign_BYTES];
    
    crypto_sign_detached(sig, NULL, message, 4, sk);

    int i;
    for (i=0; i<64; i++)
    {
        printf("%02X", sig[i]);
    }
    printf("\n");
}

Haskell 输出为：

"17aa8f20476a8e70f860707b8fd7f8f78ffd778690a755ddf3a432a81786ea3dea9efa2028d8896efaf1efe428781b3af83ab0450fc94a2ae6ec2c1a34ca830e"

C输出为：

17AA8F20476A8E70F860707B8FD7F8F78FFD778690A755DDF3A432A81786EA3D4B54ECDA53E7774C43BE7098A96C39A59664953E40AFFB54ACB84E09CBFF4E07

为什么这些签名只匹配 64 字节的前 32 个字节？如果有帮助，我已将代码放在 Github.

Answer 1

crypto_sign_SECRETKEYBYTES 是 64，而不是 32。将你的密钥设置这么长，C 和 Haskell 代码将相互一致。

Haskell 绑定到 libsodium 的外部函数接口 - 错误签名

Haskell Foreign function interface binding to libsodium - bad signature

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