ddns-scripts: Support Amazon AWS Route53 as a ddns provider

Based on a sh-only route53 update script by Yuval Adam
https://github.com/yuvadm/route53-ddns/blob/master/route53.sh

Signed-off-by: Max Berger <max@berger.name>

net/ddns-scripts/files/update_route53_v1.sh

@@ -0,0 +1,97 @@
+#!/bin/sh
+#.Distributed under the terms of the GNU General Public License (GPL) version 2.0
+#.based on Yuval Adam's route53.sh found at https://github.com/yuvadm/route53-ddns/blob/master/route53.sh
+#.2017 Max Berger <max at berger dot name>
+[ -z "$CURL_SSL" ] && write_log 14 "Amazon AWS Route53 communication require cURL with SSL support. Please install"
+[ -z "$username" ] && write_log 14 "Service section not configured correctly! Missing key as 'username'"
+[ -z "$password" ] && write_log 14 "Service section not configured correctly! Missing secret as 'password'"
+[ -z "$domain" ] && write_log 14 "Service section not configured correctly! Missing zone id as 'domain'"
+
+set -euo pipefail
+IFS=$'\n\t'
+
+ENDPOINT="route53.amazonaws.com"
+RECORD_TTL=300
+RECORD_NAME="$lookup_host".
+[ $use_ipv6 -eq 0 ] && RECORD_TYPE="A"
+[ $use_ipv6 -eq 1 ] && RECORD_TYPE="AAAA"
+RECORD_VALUE="$LOCAL_IP"
+HOSTED_ZONE_ID="$domain"
+API_PATH="/2013-04-01/hostedzone/${HOSTED_ZONE_ID}/rrset/"
+
+AWS_ACCESS_KEY_ID="$username"
+AWS_SECRET_ACCESS_KEY="$password"
+AWS_REGION='us-east-1'
+AWS_SERVICE='route53'
+
+hash() {
+    msg=$1
+    echo -en "$msg" | openssl dgst -sha256 | sed 's/^.* //'
+}
+
+sign_plain() {
+    # Sign message using a plaintext key
+    key=$1
+    msg=$2
+    echo -en "$msg" | openssl dgst -hex -sha256 -hmac "$key" | sed 's/^.* //'
+}
+
+sign() {
+    # Sign message using a hex formatted key
+    key=$1
+    msg=$2
+    echo -en "$msg" | openssl dgst -hex -sha256 -mac HMAC -macopt "hexkey:${key}" | sed 's/^.* //'
+}
+
+request_body="<?xml version=\"1.0\" encoding=\"UTF-8\"?> \
+<ChangeResourceRecordSetsRequest xmlns=\"https://route53.amazonaws.com/doc/2013-04-01/\"> \
+<ChangeBatch> \
+   <Changes> \
+      <Change> \
+         <Action>UPSERT</Action> \
+         <ResourceRecordSet> \
+            <Name>${RECORD_NAME}</Name> \
+            <Type>${RECORD_TYPE}</Type> \
+            <TTL>${RECORD_TTL}</TTL> \
+            <ResourceRecords> \
+               <ResourceRecord> \
+                  <Value>${RECORD_VALUE}</Value> \
+               </ResourceRecord> \
+            </ResourceRecords> \
+         </ResourceRecordSet> \
+      </Change> \
+   </Changes> \
+</ChangeBatch> \
+</ChangeResourceRecordSetsRequest>"
+
+fulldate=$(date --utc +%Y%m%dT%H%M%SZ)
+shortdate=$(date --utc +%Y%m%d)
+signed_headers="host;x-amz-date"
+request_hash=$(hash "$request_body")
+canonical_request="POST\n${API_PATH}\n\nhost:route53.amazonaws.com\nx-amz-date:${fulldate}\n\n${signed_headers}\n${request_hash}"
+
+date_key=$(sign_plain "AWS4${AWS_SECRET_ACCESS_KEY}" "${shortdate}")
+region_key=$(sign "$date_key" $AWS_REGION)
+service_key=$(sign "$region_key" $AWS_SERVICE)
+signing_key=$(sign "$service_key" aws4_request)
+
+credential="${shortdate}/${AWS_REGION}/${AWS_SERVICE}/aws4_request"
+sigmsg="AWS4-HMAC-SHA256\n${fulldate}\n${credential}\n$(hash "$canonical_request")"
+
+signature=$(sign "$signing_key" "$sigmsg")
+
+authorization="AWS4-HMAC-SHA256 Credential=${AWS_ACCESS_KEY_ID}/${credential}, SignedHeaders=${signed_headers}, Signature=${signature}"
+
+ANSWER=$(curl \
+    -X "POST" \
+    -H "Host: route53.amazonaws.com" \
+    -H "X-Amz-Date: ${fulldate}" \
+    -H "Authorization: ${authorization}" \
+    -H "Content-Type: text/xml" \
+    -d "$request_body" \
+    "https://${ENDPOINT}${API_PATH}")
+write_log 7 "${ANSWER}"
+
+echo ${ANSWER} | grep Error >/dev/null && return 1
+echo ${ANSWER} | grep ChangeInfo >/dev/null && return 0
+return 2