Implement server-side support for sk-ecdsa U2F-backed keys (#142) * Implement server-side support for sk-ecdsa U2F-backed keys * Fix out-of-bounds read on normal ecdsa-sha2-[identifier] keys * Fix one more potential out-of-bounds read * Check if nistp256 curve is used in sk-ecdsa-sha2- key It's the only allowed curve per PROTOCOL.u2f specification * Implement server-side support for sk-ed25519 FIDO2-backed keys * Keys with type sk-* make no sense as host keys, so they should be disabled * fix typo * Make sk-ecdsa call buf_ecdsa_verify This reduces code duplication, the SK code just handles the different message format. * Reduce sk specific code The application id can be stored in signkey, then we don't need to call sk-specific functions from svr-authpubkey * Remove debugging output, which causes compilation errors with DEBUG_TRACE disabled * Proper cleanup of sk_app Co-authored-by: Matt Johnston <[email protected]>

-----BEGIN DSA PRIVATE KEY-----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-----END DSA PRIVATE KEY-----