1  

Beware The original code posted in this question has a BUG...

注意这个问题中发布的原始代码有一个BUG ...

I'm just going to comment on this, and show you how to handle it.

我只想对此发表评论，并向您展示如何处理它。

unsigned char publicKey[] = {0x30, 0x5a, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, ...}
size_t publicKeyLength = sizeof(publicKey);

unsigned char* t = publicKey;
rsa = d2i_RSA_PUBKEY(NULL, &t, pubKeyLen);

Internally, the temporary pointer t is incremented, so its wasted. It will point to some place after the buffer if everything works as expected. What you should find is (size_t)t - (size_t)publicKey == publicKeyLength after the function executes.

在内部，临时指针t递增，因此浪费了它。如果一切按预期工作，它将指向缓冲区之后的某个位置。在函数执行后你应该找到的是（size_t）t - （size_t）publicKey == publicKeyLength。

Because you used a temporary pointer, the original pointer publicKey is still good. And you can use t to parse the next key if there are consecutive keys in memory.

因为您使用了临时指针，所以原始指针publicKey仍然很好。如果内存中有连续的密钥，您可以使用t来解析下一个密钥。

There's no need to copy the data.

无需复制数据。

I think a second option is to use a memory BIO and d2i_RSA_PUBKEY_bio. Something like:

我认为第二种选择是使用内存BIO和d2i_RSA_PUBKEY_bio。就像是：

BIO* bio = BIO_new_mem_buf(publicKey, (int)publicKeyLength);
ASSERT(bio != NULL);

RSA* rsa = d2i_RSA_PUBKEY_bio(bio, NULL);
ASSERT(rsa != NULL);

/* ... */

RSA_free(rsa);
BIO_free(bio);

The get1 bumps the reference count, so you need to call free on both the EVP_PKEY* and RSA*.

get1会破坏引用计数，因此您需要在EVP_PKEY *和RSA *上调用free。

0  

With the help of @jww in this answer https://stackoverflow.com/a/29885771/2692914. I came up with this solution, I hope it is ok:

在这个答案https://stackoverflow.com/a/29885771/2692914的@jww的帮助下。我想出了这个解决方案，我希望它没问题：

bool isValidPublicKeyOnly(EVP_PKEY *pkey) {
    //EVP_PKEY_get_type from https://stackoverflow.com/a/29885771/2692914
    int type = EVP_PKEY_get_type(pkey); //checks nullptr
    if (type != EVP_PKEY_RSA && type != EVP_PKEY_RSA2) {
        //not RSA
        return false;
    }

    RSA *rsa = EVP_PKEY_get1_RSA(pkey);
    if (!rsa) {
        return false;
    }

    bool isValid = isValidRSAPublicKeyOnly(rsa);
    RSA_free(rsa);
    return isValid;
}

bool isValidRSAPublicKeyOnly(RSA *rsa) {
    //from rsa_ameth.c do_rsa_print : has a private key
    //from rsa_chk.c RSA_check_key : doesn't have n (modulus) and e (public exponent)
    if (!rsa || rsa->d || !rsa->n || !rsa->e) {
        return false;
    }
    //from http://rt.openssl.org/Ticket/Display.html?user=guest&pass=guest&id=1454
    //doesnt have a valid public exponent
    return BN_is_odd(rsa->e) && !BN_is_one(rsa->e);
}