Unable to load RSA public key for signature verification

Viktor Dukhovni openssl-users at dukhovni.org
Thu Apr 13 17:49:09 UTC 2023

On Thu, Apr 13, 2023 at 05:28:34PM +0000, Michael Wojcik via openssl-users wrote:

> > int main() {
> >  constexpr auto pubKey = "-----BEGIN PUBLIC KEY-----\n"
> A quick look at the source shows PEM_read_RSAPublicKey wants
> PEM_STRING_RSA_PUBLIC, which is "RSA PUBLIC KEY". So that function
> only supports PEM objects with the start line
> "-----BEGIN RSA PUBLIC KEY-----".

Yes, that's the issue.

> OpenSSL supports multiple PEM formats for RSA keys. I'm trying to
> recall the details -- I think there's an old OpenSSL format and a
> later standard format, maybe?

There's an RSA algorithm-specific legacy format an an algorithm-neutral
preferred format (X.509 SPKI).

> Try PEM_read_RSA_PUBKEY instead.

No, just use PEM_read_PUBKEY(), and use algorithm-neutral APIs that
will work equally well with RSA, ECDSA, Ed25519, ...


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