OpenSSL EVP_BytesToKey 方法的 C 版本

Question

我正在寻找 OpenSSL EVP_BytesToKey 函数的 C 实现。

这是 EVP_BytesToKey 方法的伪代码解释(在 OpenSSL 源代码的/doc/ssleay.txt 中):

/* M[] is an array of message digests
 * MD() is the message digest function */
M[0]=MD(data . salt);
for (i=1; i<count; i++) M[0]=MD(M[0]);

i=1
while (data still needed for key and iv)
{
    M[i]=MD(M[i-1] . data . salt);
    for (i=1; i<count; i++) M[i]=MD(M[i]);
    i++;
}

If the salt is NULL, it is not used.
The digests are concatenated together.
M = M[0] . M[1] . M[2] .......

这是我的代码(MD()是sha512。我需要 key 是32字节，iv是16字节):

int main()
{
    unsigned long long out[8]; 
    unsigned char key[9] = {0x4b,0x0c,0x0c,0x0c,0x0c,0x0c,0x0c,0x0c,0x0c};
    int len, i;

    len = sizeof(key);
    sha512(out, key, len);

    unsigned char a[sizeof(out)];
    for (i = 0; i < count; i++) 
    {
        long2char(out, a); // unsigned long long to unsigned char;
        sha512(out, a, sizeof(out));
    }

    return 0;
}

经过 count 次 sha512() 后，输出为 64 字节，所以我认为我不需要其余的伪代码。但结果不正确，不知道哪里出了问题。

我希望你能帮我解决这个问题。谢谢!

Answer 1

I'm looking for C implementation of the OpenSSL EVP_BytesToKey function...

也许您应该只使用 OpenSSL 提供的一个？您知道，evp_key.c 中名为 EVP_BytesToKey 的那个。 (如下所示)。

OpenSSL 1.1.0c changed the digest algorithm用于一些内部组件。之前使用MD5，1.1.0改用SHA256。请注意，更改不会影响 EVP_BytesToKey 和 openssl enc 等命令

<小时/>

int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
                   const unsigned char *salt, const unsigned char *data,
                   int datal, int count, unsigned char *key,
                   unsigned char *iv)
{
    EVP_MD_CTX *c;
    unsigned char md_buf[EVP_MAX_MD_SIZE];
    int niv, nkey, addmd = 0;
    unsigned int mds = 0, i;
    int rv = 0;
    nkey = EVP_CIPHER_key_length(type);
    niv = EVP_CIPHER_iv_length(type);
    OPENSSL_assert(nkey <= EVP_MAX_KEY_LENGTH);
    OPENSSL_assert(niv <= EVP_MAX_IV_LENGTH);

    if (data == NULL)
        return nkey;

    c = EVP_MD_CTX_new();
    if (c == NULL)
        goto err;
    for (;;) {
        if (!EVP_DigestInit_ex(c, md, NULL))
            goto err;
        if (addmd++)
            if (!EVP_DigestUpdate(c, &(md_buf[0]), mds))
                goto err;
        if (!EVP_DigestUpdate(c, data, datal))
            goto err;
        if (salt != NULL)
            if (!EVP_DigestUpdate(c, salt, PKCS5_SALT_LEN))
                goto err;
        if (!EVP_DigestFinal_ex(c, &(md_buf[0]), &mds))
            goto err;

        for (i = 1; i < (unsigned int)count; i++) {
            if (!EVP_DigestInit_ex(c, md, NULL))
                goto err;
            if (!EVP_DigestUpdate(c, &(md_buf[0]), mds))
                goto err;
            if (!EVP_DigestFinal_ex(c, &(md_buf[0]), &mds))
                goto err;
        }
        i = 0;
        if (nkey) {
            for (;;) {
                if (nkey == 0)
                    break;
                if (i == mds)
                    break;
                if (key != NULL)
                    *(key++) = md_buf[i];
                nkey--;
                i++;
            }
        }
        if (niv && (i != mds)) {
            for (;;) {
                if (niv == 0)
                    break;
                if (i == mds)
                    break;
                if (iv != NULL)
                    *(iv++) = md_buf[i];
                niv--;
                i++;
            }
        }
        if ((nkey == 0) && (niv == 0))
            break;
    }
    rv = EVP_CIPHER_key_length(type);
 err:
    EVP_MD_CTX_free(c);
    OPENSSL_cleanse(md_buf, sizeof(md_buf));
    return rv;
}