undocumented options for -inform / -outform for rsa / OpenSSL?

Question

According to http://pumka.net/2009/12/19/reading-writing-and-converting-rsa-keys-in-pem-der-publickeyblob-and-privatekeyblob-formats/ MSPRIVATEKEYBLOB and MSPUBLICKEYBLOB are acceptable parameters for -outform / -inform for rsa.

The official OpenSSL docs, however, make no mention of these parameters:

https://www.openssl.org/docs/man1.0.1/apps/rsa.html

This kinda makes me wonder.. what other undocumented parameters can -outform and -inform?

Answer 1

Unfortunately proper documentation is not one of the strength of OpenSSL (and it shares this weakness with many other software). The parsing of the options is done in apps/opt.c function opt_format. Not all of the possible options are implemented for rsa but looking at apps/rsa.c I see mention of PEM, DER, MSBLOB and PVK.