On Jan 5, 2014, at 11:49 AM, Alan D. Cabrera <l...@toolazydogs.com> wrote:
> I've created a public key file using the following commands: > > openssl genrsa -out mykey.pem 2046 > openssl rsa -in mykey.pem -pubout > mykey.pub > > I then read it from some C code: > > public_key = PEM_read_RSA_PUBKEY(fp, NULL, NULL, NULL); > > and then obtain the DER form of this public key: > > int len = i2d_RSAPublicKey (public_key, NULL); > buf = (unsigned char *) malloc (len); > i2d_RSAPublicKey (public_key, &buf); > here len == 269 > > but the command line openssl tells me: > > openssl rsa -outform der -pubin -inform pem -in mykey.pub | wc > writing RSA key > 1 10 293 > > When I print out the DER forms from openssl and my C code they, obviously, > don't match and, oddly, the DER encoding that my C code obtains has a lot of > zeros. > > What could I be doing wrong? I should have obtained the DER form using i2d_RSA_PUBKEY(). Also, passing &buf to the method should have warned me that the pointer was being modified. I have no idea why it gets modified and what it points to after the call. So now I do der_form = throw_away = (unsigned char *) malloc (len); i2d_RSAPublicKey (public_key, &throw_away); and use the contents of der_form. Regards, Alan
