Do HMAC with SHA1 derived key?

Question

I'm trying to create a MAC for a PKCS12. I have successfully generated key bytes according to the PKCS12 standard, section B.2. The PKCS12 standard defines
I'm supposed to do an HMAC using SHA-1 as the digest algorithm (so I do Mac.getInstance("HmacSHA1")). To initialize the Mac object I need to provide a key. At this point I have a 20 byte array representing the key, but no way to initialize the Mac as I need to convert those bytes into a Key object. The SecretKeyFactory doesn't have any algorithms listed for SHA1 or PKCS12 related so I don't know how to create a Key from the bytes (using a KeySpec...). The BouncyCastle provider also doesn't list sha1 in its list of supported algorithms for keyfactory.
I imagine this functionality is buried somewhere in the JRE as the KeyStore class can load a PKCS12 and (I would hope) it is verifying the Mac on the P12 before it uses it.

Answer 1

I must be missing something because I generate the key and initialise the Mac using            final byte[] keyBytes = ...;
            final String mode = "HmacSHA1";
            final SecretKey key = new SecretKeySpec(keyBytes, mode);
            final mac = Mac.getInstance(mode);
            mac.init(key);I have never tried using an invalid 'mode' in the key generation.