Question regarding Registration ID for x509 DPS

[domasgim]

Similar question was asked #2234

In that case as I understand, if registration ID is derived from x509 subject common name (CN) of the device certificate, why not just parse the registration ID information from the certificate itself? In the DPS sample programs the user needs to specify this value:

azure-iot-sdk-c/provisioning_client/samples/prov_dev_client_ll_x509_sample/prov_dev_client_ll_x509_sample.c

Lines 23 to 26 in 3fd808b

	// Provisioning information:
	static const char* global_prov_uri = "global.azure-devices-provisioning.net";
	static const char* id_scope = "<ID SCOPE>";
	static const char* registration_id = "<registration-id>"; // Case sensitive.

But if my application has information about x509 certificate in a string, I'm thinking I could derive registration ID information from that variable, say from x509certificate as seen below but in some separate function, that would reduce the option list a user may need to input themselves.

azure-iot-sdk-c/provisioning_client/samples/prov_dev_client_ll_x509_sample/prov_dev_client_ll_x509_sample.c

Lines 43 to 48 in 3fd808b

	static const char* x509certificate =
	"-----BEGIN CERTIFICATE-----\n"
	"MIIBVjCB/aADAgECAhRMqqc/rOqEW+Afbkw4XyMLu1PUaTAKBggqhkjOPQQDAjAT\n"
	"..."
	"dwjNGPacV5zzgA==\n"
	"-----END CERTIFICATE-----\n";

The call to this new function would be something like this, it would parse base64 encoded x509 certificate presumably with the help of openssl library functions:

static const char* registration_id = Get_Registration_ID_From_x509(x509certificate);

Would a solution like that make any sense or am I missing some key point here and should leave Registration ID to be configured separately as seen in the example?

[CIPop]

Thank you for the feedback! We will consider this as a feature request.

We have considered this in the past but decided against adding more dependencies such as an ASN.1 parser. While using OpenSSL might be simple, we have to consider support for multiple TLS stacks (mBedTLS, WolfSSL, SChannel, etc) making this feature a medium to large project.