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]>

Multi-binary compilation
========================

To compile for systems without much space (floppy distributions etc), you
can create a single binary. This will save disk space by avoiding repeated
code between the various parts.
If you are familiar with "busybox", it's the same principle.

To compile the multi-binary, first "make clean" (if you've compiled
previously), then

make PROGRAMS="programs you want here" MULTI=1

To use the binary, symlink it from the desired executable:

ln -s dropbearmulti dropbear
ln -s dropbearmulti dbclient
etc

then execute as normal:

./dropbear <options here>