From ec0f8838547f8f787a6d0dc099f8ff0d467cd04c Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Wed, 2 Sep 2020 05:13:16 +0000
Subject: once/get_updates.sh: initial implementation.

---
 once/get_updates.sh | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100755 once/get_updates.sh

diff --git a/once/get_updates.sh b/once/get_updates.sh
new file mode 100755
index 0000000..2f6485b
--- /dev/null
+++ b/once/get_updates.sh
@@ -0,0 +1,162 @@
+#!/bin/sh
+
+set -eu
+
+trap update_failure 1 2 EXIT
+
+# before we begin...
+mb_path="$PATH"
+mb_script="$0"
+mb_success=no
+mb_obtain=no
+mb_dlopt="${1:-}"
+
+error_msg()
+{
+	printf '%s\n' "$@" >&2
+}
+
+warning_msg()
+{
+	printf '%s\n' "$@" >&2
+}
+
+update_failure()
+{
+	if [ _$mb_success = _yes ]; then
+		return 0
+	fi
+
+	printf 'update info: exiting due to an error.\n' >&3
+
+	exit 2
+}
+
+
+update_needed()
+{
+	trap '' EXIT
+	mb_success=yes
+	exit 1
+}
+
+
+update_success()
+{
+	trap '' EXIT
+	mb_success=yes
+	exit 0
+}
+
+obtain_remote_file()
+{
+	pathname="$1"
+
+	case "$mb_vendor" in
+		/* )
+			cp -p "${mb_vendor}/${pathname}" \
+				"${pathname}"
+			;;
+
+		https://* )
+			wget "${mb_vendor}/${pathname}"       \
+				--output-document="${pathname}"  \
+				--no-check-certificate            \
+				2>/dev/null
+			;;
+
+		* )
+			error_msg "Invalid prefix in path argument ${pathname}"
+			update_failure
+			;;
+	esac
+}
+
+# logging
+exec 3> /updates/update.log
+
+# previous state
+if [ -f /updates/update.pending ]; then
+	rm /updates/update.pending
+	update_needed
+fi
+
+# vendor server location
+mb_vendor=$(cat /etc/vendor.host)
+
+# obtain list of advertised updates
+obtain_remote_file /updates/updates.sha256
+mb_tarballs=$(cut -d' ' -f3 /updates/updates.sha256)
+
+# simple argument parsing
+if [ "${mb_dlopt}" = '--obtain-tarballs' ]; then
+	mb_obtain=yes
+fi
+
+# compare against local state
+for tarball in ${mb_tarballs:-}; do
+	printf 'checking local status of %s...\n' $tarball >&3
+
+	if ! [ -f /updates/$tarball ]; then
+		printf '\t/updates/%s does not exist, download needed.\n' $tarball >&3
+
+		if [ $mb_obtain = no ]; then
+			update_needed
+		else
+			mb_needed=yes
+		fi
+	else
+		printf '\t/updates/%s found, checking signatures...\n' $tarball >&3
+
+		if ! [ -f /updates/$tarball.sha256 ]; then
+			sha256sum /updates/$tarball > /updates/$tarball.sha256
+		fi
+
+		mb_remotesig=$(grep $tarball /updates/updates.sha256 | cut -d' ' -f1)
+		mb_localsig=$(cat /updates/$tarball.sha256 | cut -d' ' -f1)
+
+		printf '\tremote signature: %s\n' $mb_remotesig >&3
+		printf '\tlocal  signature: %s\n' $mb_localsig >&3
+
+		if [ $mb_localsig != $mb_remotesig ]; then
+			printf '\tsignatures do not match, download needed.\n' >&3
+
+			if [ $mb_obtain = no ]; then
+				update_needed
+			else
+				mb_needed=yes
+			fi
+		else
+			printf '\tsignatures match, local tarball is already up-to-date.\n' >&3
+			mb_needed=no
+		fi
+	fi
+
+	if [ $mb_needed = yes ]; then
+		printf '\tattempting to download %s...\n' ${mb_vendor}/updates/$tarball >&3
+
+		obtain_remote_file /updates/$tarball
+		sha256sum /updates/$tarball > /updates/$tarball.sha256
+
+		mb_remotesig=$(grep $tarball /updates/updates.sha256 | cut -d' ' -f1)
+		mb_localsig=$(cat /updates/$tarball.sha256 | cut -d' ' -f1)
+
+		printf '\tremote signature: %s\n' $mb_remotesig >&3
+		printf '\tlocal  signature: %s\n' $mb_localsig >&3
+
+		if [ $mb_localsig != $mb_remotesig ]; then
+			printf 'signatures do not match, aborting.\n' >&3
+			update_failure
+		else
+			printf '\t/local tarball is now up-to-date.\n' >&3
+		fi
+	fi
+
+	printf '\n' >&3
+done
+
+# status
+touch /updates/update.pending
+
+# all done
+update_success
-- 
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