Importing a PKCS#1 RSAPublicKey structure into a gnutls_pubkey_t

[René Korthaus]

Hello list,

I have a smartcard that gives me a PKCS#1 RSAPublicKey structure of the 
public key on the card and I need to generate a X.509 
SubjectPublicKeyInfo structure from it. I already have a C++ wrapper 
class that uses gnutls_pubkey_export to generate the 
SubjectPublicKeyInfo structure. The question is how to import the 
RSAPublicKey structure right.

As there seems to be no direct way to import from PCKS#1 I tried the 
following approach, which failed:
1) Use gnutls_rsa_params_import_pkcs1 to import PKCS1 structure into 
rsa_params structure
2) Use gnutls_rsa_params_export_raw to export modulus and exponent
3) Use gnutls_pubkey_import_rsa_raw to finally import modulus and 
exponent into gnutls_pubkey_t

The call to gnutls_rsa_params_import_pkcs1 fails with a 
GNUTLS_E_ASN1_DER_ERROR. The data can be viewed fine from within an ASN1 
viewer.

Questions:
* Is there an onbvious way to import PKCS#1 RSAPublicKey into a 
gnutls_pubkey_t structure?
* From my short look into the code of gnutls_rsa_params_import_pkcs1, it 
seems that it calls gnutls_x509_privkey_import which uses 
_gnutls_privkey_decode_pkcs1_rsa_key to import a _private key_ from a 
_RSAPrivateKey_ structure although it according to doc "should contain a 
PKCS1 RSAPublicKey structure PEM or DER encoded". Of course this fails 
in my case, as what I hand over is a RSAPublicKey structure, not a 
RSAPrivatekey. What's wrong here?

Please CC me when answering, as I am not on the list. Thx.

Best regards, René


-- 
Sirrix AG security technologies - http://www.sirrix.com
René Korthaus      eMail: r.korthaus at sirrix.com
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