c – 将PEM编码的X.509证书加载到Windows CryptoAPI中

我知道如果我有HCRYPTKEY后如何加密/解密.
但是,我只是不知道如何在.PEM文件中导入Base64 blob并获得我可以使用的HCRYPTKEY.

我有一种奇怪的感觉,除了简单地调用CryptDecodeObject()之外还有更多的东西.

任何可以让我走上正轨的指针？我已经失去了两天做“试验和错误”编程而无处可去.

I discovered the “magic” sequence of calls to import a RSA public key in PEM format. Here you go:

decode the key into a binary blob with CryptStringToBinary; pass CRYPT_STRING_BASE64HEADER in dwFlags decode the binary key blob into a CERT_PUBLIC_KEY_INFO with CryptDecodeObjectEx; pass X509_ASN_ENCODING in dwCertEncodingType and X509_PUBLIC_KEY_INFO in lpszStructType decode the PublicKey blob from the CERT_PUBLIC_KEY_INFO into a RSA key blob with CryptDecodeObjectEx; pass X509_ASN_ENCODING in dwCertEncodingType and RSA_CSP_PUBLICKEYBLOB in lpszStructType import the RSA key blob with CryptImportKey

这个序列确实帮助我理解了发生了什么,但它对我来说并不适用.第二次调用CryptDecodeObjectEx给了我一个错误：
“符合ASN.1标签值”.
在多次尝试理解Microsoft文档之后,我终于意识到第一个解码的输出不能再被解码为ASN,并且它实际上已准备好导入.通过这种理解,我在以下链接中找到了答案：

http://www.ms-news.net/f2748/problem-importing-public-key-4052577.html

以下是我自己的程序,它将.pem文件中的公钥导入CryptApi上下文：

int main()
{
    char           pemPubKey[2048];
    int            readLen;
    char           derPubKey[2048];
    size_t         derPubKeyLen = 2048;
    CERT_PUBLIC_KEY_INFO *publicKeyInfo;
    int            publicKeyInfoLen;
    HANDLE         hFile;
    HCRYPTPROV     hProv = 0;
    HCRYPTKEY      hKey = 0;

    /*
     * Read the public key cert from the file
     */
    hFile = CreateFileA( "c:\\pub.pem", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL );
    if ( hFile == INVALID_HANDLE_VALUE )
    {
        fprintf( stderr, "Failed to open file. error: %d\n", GetLastError() );
    }

    if ( !ReadFile( hFile, pemPubKey, 2048, &readLen, NULL ) )
    {
        fprintf( stderr, "Failed to read file. error: %d\n", GetLastError() );
    }

    /*
     * Convert from PEM format to DER format - removes header and footer and decodes from base64
     */
    if ( !CryptStringToBinaryA( pemPubKey, 0, CRYPT_STRING_BASE64HEADER, derPubKey, &derPubKeyLen, NULL, NULL ) )
    {
        fprintf( stderr, "CryptStringToBinary failed. Err: %d\n", GetLastError() );
    }

    /*
     * Decode from DER format to CERT_PUBLIC_KEY_INFO
     */
    if ( !CryptDecodeObjectEx( X509_ASN_ENCODING, X509_PUBLIC_KEY_INFO, derPubKey, derPubKeyLen, 
                               CRYPT_ENCODE_ALLOC_FLAG, NULL, &publicKeyInfo, &publicKeyInfoLen ) )
    {
        fprintf( stderr, "CryptDecodeObjectEx 1 failed. Err: %p\n", GetLastError() );
        return -1;
    }

    /*
     * Acquire context 
     */
    if( !CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) )
    {
        {
            printf( "CryptAcquireContext failed - err=0x%x.\n", GetLastError() );
            return -1;
        }
    }

    /*
     * Import the public key using the context
     */
    if ( !CryptImportPublicKeyInfo( hProv, X509_ASN_ENCODING, publicKeyInfo, &hKey ) )
    {
        fprintf( stderr, "CryptImportPublicKeyInfo failed. error: %d\n", GetLastError() );
        return -1;
    }
    LocalFree( publicKeyInfo );

    /*
     * Now use hKey to encrypt whatever you need.
     */

    return 0;
}