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]>

--- a/default_options.h	Sat Jan 22 12:46:08 2022 +0800
+++ b/default_options.h	Sat Jan 22 16:53:04 2022 +0300
@@ -126,9 +126,11 @@
  * code (either ECDSA or ECDH) increases binary size - around 30kB
  * on x86-64 */
 #define DROPBEAR_ECDSA 1
+#define DROPBEAR_SK_ECDSA 1
 /* Ed25519 is faster than ECDSA. Compiling in Ed25519 code increases
    binary size - around 7,5kB on x86-64 */
 #define DROPBEAR_ED25519 1
+#define DROPBEAR_SK_ED25519 1
 
 /* RSA must be >=1024 */
 #define DROPBEAR_DEFAULT_RSA_SIZE 2048