From 4ff0ee9aa5a500ce51dc6a93f400641698cdf3e0 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Sat, 10 Oct 2020 13:24:38 -0400
Subject: add script originating from cryptonomic source

---
 src/get-dyndns-name | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100755 src/get-dyndns-name

diff --git a/src/get-dyndns-name b/src/get-dyndns-name
new file mode 100755
index 0000000..7ef8c1b
--- /dev/null
+++ b/src/get-dyndns-name
@@ -0,0 +1,67 @@
+#!/bin/sh
+set -e
+
+DEFAULT_AUTH_TYPE=ed25519
+
+in_group()
+{
+    local g
+    for g in $(groups)
+    do
+        [ "$g" = "$1" ] && return
+    done
+    false
+}
+
+ssh_keytag_to_path_fragment()
+{
+    case "$1" in
+        ssh-dss) echo dsa ;;
+        ecdsa-sha2-nistp256) echo ecdsa ;;
+        ssh-rsa|ssh-ed25519) echo ${1#ssh-} ;;
+        *) return 1 ;;
+    esac
+}
+
+path_fragment_to_ssh_keytag()
+{
+    case "$1" in
+        ssh-dss|ecdsa-sha2-nistp256|ssh-rsa|ssh-ed25519) echo $1;;
+        dss|rsa|ed25519) echo ssh-$1 ;;
+        dsa) echo ssh-dss ;;
+        ecdsa) echo ecdsa-sha2-nistp256 ;;
+        *) return 1 ;;
+    esac
+}
+
+get_dyndns_domain()
+{
+        fragment=$(ssh_keytag_to_path_fragment "$1") || return
+
+        host_keyfile=/etc/ssh/ssh_host_${fragment}_key
+        user_keyfile=$HOME/.ssh/id_${fragment}
+
+        set -- -q dyndns@cryptonomic.net
+
+        if [ -r "$host_keyfile" ]
+        then
+                set -- ssh -i "$host_keyfile" "$@"
+
+        elif in_group sudo
+        then
+                set -- sudo ssh -i "$host_keyfile" "$@"
+
+        elif [ -r "$user_keyfile" ]
+        then
+                set -- ssh -i "$user_keyfile" "$@"
+
+        else
+                set -- ssh "$@"
+        fi
+
+        "$@"
+}
+
+AUTH_TYPE=${1:-$DEFAULT_AUTH_TYPE}
+AUTH_KEYTAG=$(path_fragment_to_ssh_keytag "$AUTH_TYPE")
+get_dyndns_domain "$AUTH_KEYTAG"
-- 
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