Recognize LANcom LCOS software and support extraction of ssh-ed448 key type

LANcom router devices appear to be primarily used in Germany (see [1]
for examples on the public Internet), and they appear to support the
`ssh-ed448` key type which is documented in [2], but which has never
been supported by any as-yet-released version of OpenSSH.

[1] https://www.shodan.io/search?query=ssh+%22ed448%22
[2] https://datatracker.ietf.org/doc/html/rfc8709#name-public-key-format

src/ssh_audit/hostkeytest.py

@@ -52,6 +52,9 @@ class HostKeyTest:
 
         'ssh-ed25519':                      {'cert': False, 'variable_key_len': False},
         'ssh-ed25519-cert-v01@openssh.com': {'cert': True, 'variable_key_len': False},
+
+        'ssh-ed448':                      {'cert': False, 'variable_key_len': False},
+        # 'ssh-ed448-cert-v01@openssh.com': {'cert': True,  'variable_key_len': False},
     }
 
     TWO2K_MODULUS_WARNING = '2048-bit modulus only provides 112-bits of symmetric strength'

src/ssh_audit/kexdh.py

@@ -134,6 +134,9 @@ class KexDH:  # pragma: nocover
         if self.__hostkey_type == 'ssh-ed25519':
             self.out.d("%s has a fixed host key modulus of 32." % self.__hostkey_type)
             self.__hostkey_n_len = 32
+        elif self.__hostkey_type == 'ssh-ed448':
+            self.out.d("%s has a fixed host key modulus of 57." % self.__hostkey_type)
+            self.__hostkey_n_len = 57
         else:
             # Here is the modulus size & actual modulus of the host key public key.
             hostkey_n, self.__hostkey_n_len, ptr = KexDH.__get_bytes(hostkey, ptr)

src/ssh_audit/software.py

@@ -224,4 +224,8 @@ class Software:
         mx = re.match(r'^PuTTY_Release_(.*)', software)
         if mx:
             return cls(None, Product.PuTTY, mx.group(1), None, None)
+        mx = re.match(r'^lancom(.*)', software)
+        if mx:
+            v, p = 'LANcom', 'LCOS sshd'
+            return cls(v, p, mx.group(1), None, None)
         return None

src/ssh_audit/ssh2_kexdb.py

@@ -68,6 +68,7 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
     INFO_DEPRECATED_IN_OPENSSH88 = 'deprecated in OpenSSH 8.8: https://www.openssh.com/txt/release-8.8'
     INFO_DISABLED_IN_DBEAR67 = 'disabled in Dropbear SSH 2015.67'
     INFO_DISABLED_IN_OPENSSH70 = 'disabled in OpenSSH 7.0: https://www.openssh.com/txt/release-7.0'
+    INFO_RFC8709_NOT_OPENSSH = 'described in RFC8709 but never implemented in OpenSSH'
     INFO_NEVER_IMPLEMENTED_IN_OPENSSH = 'despite the @openssh.com tag, this was never implemented in OpenSSH'
     INFO_REMOVED_IN_OPENSSH61 = 'removed since OpenSSH 6.1, removed from specification'
     INFO_REMOVED_IN_OPENSSH69 = 'removed in OpenSSH 6.9: https://www.openssh.com/txt/release-6.9'
@@ -245,7 +246,7 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
             'ssh-dss-sha512@ssh.com': [[], [FAIL_1024BIT_MODULUS]],
             'ssh-ed25519': [['6.5,d2020.79,l10.7.0']],
             'ssh-ed25519-cert-v01@openssh.com': [['6.5']],
-            'ssh-ed448': [[]],
+            'ssh-ed448': [[], [], [], [INFO_RFC8709_NOT_OPENSSH]],
             'ssh-ed448-cert-v01@openssh.com': [[], [], [], [INFO_NEVER_IMPLEMENTED_IN_OPENSSH]],
             'ssh-gost2001': [[], [FAIL_UNTRUSTED]],
             'ssh-gost2012-256': [[], [FAIL_UNTRUSTED]],