RC4, which was previously used for performance reasons, is not supported
anymore with newer versions of SSH (stretch still supports it, but it
requires explicit configuration on the guests when they act as clients
too - the version in Ubuntu 18.04 apparently doesn't support it anymore
at all).
AES-GCM should actually be faster (at least for larger amounts of data and
in particular with hardware acceleration).
ClientAuthentication is known in OpenSSL 1.1 and the redefinition, therefore,
causes an error. These two OIDs are not used anyway in these config
files.
This adds the ability to return supported signature schemes (and
parameters) from a private key.
This is useful for keys on a TPM 2.0 as these can be used only with a
particular scheme (the hash algorithm and for RSA even the padding scheme
is fixed). For RSA with PSS padding there is an additional complication
because different TPMs use different salt lengths, which we have to know
beforehand to correctly produce e.g. a certificate request (the signature
covers the algorithm identifier that describes the signature scheme).
It turned out that the new method is also useful for the agent plugin.
Newer ssh/gpg-agents support SHA-256 and SHA-512 for RSA signatures, but
not SHA-384, which we can now convey to the pubkey authenticator.
Unfortunately, older agents ignore the flags that request a SHA2 signature
and just return one with SHA-1, in such scenarios IKEv2 signature
authentication has to be disabled.
SHA-384 is not supported but is selected by signature_schemes_for_key()
for keys between 3072 and 7680 bits.
Since this is only called for IKEv2 signature authentication we don't
even provide SHA-1 anymore. We always provide both schemes, though,
which is what pubkey-authenticator does too for RSA.
Older agents apparently just ignore the flags and always return a SHA-1
signature. If that's the case, charon.signature_authentication has to
be disabled.
On newer Android versions (8+) this does not seem to be necessary (adding
the onClick handler also sets "clickable" and that in turn seems to make
it focusable), however, for older releases it is (tested with 7.1.1
keyboard navigation just skips over the button). This was seen on a
Fire TV stick.
Andreas Steffen