Merge pull request #1292 from mal/aws-use-instance-role

Let AWS DNS API driver pull creds from instance metadata

dnsapi/dns_aws.sh

@@ -21,6 +21,11 @@ dns_aws_add() {
 
   AWS_ACCESS_KEY_ID="${AWS_ACCESS_KEY_ID:-$(_readaccountconf_mutable AWS_ACCESS_KEY_ID)}"
   AWS_SECRET_ACCESS_KEY="${AWS_SECRET_ACCESS_KEY:-$(_readaccountconf_mutable AWS_SECRET_ACCESS_KEY)}"
+
+  if [ -z "$AWS_ACCESS_KEY_ID" ] || [ -z "$AWS_SECRET_ACCESS_KEY" ]; then
+    _use_instance_role
+  fi
+
   if [ -z "$AWS_ACCESS_KEY_ID" ] || [ -z "$AWS_SECRET_ACCESS_KEY" ]; then
     AWS_ACCESS_KEY_ID=""
     AWS_SECRET_ACCESS_KEY=""
@@ -29,9 +34,11 @@ dns_aws_add() {
     return 1
   fi
 
-  #save for future use
-  _saveaccountconf_mutable AWS_ACCESS_KEY_ID "$AWS_ACCESS_KEY_ID"
-  _saveaccountconf_mutable AWS_SECRET_ACCESS_KEY "$AWS_SECRET_ACCESS_KEY"
+  #save for future use, unless using a role which will be fetched as needed
+  if [ -z "$_using_role" ]; then
+    _saveaccountconf_mutable AWS_ACCESS_KEY_ID "$AWS_ACCESS_KEY_ID"
+    _saveaccountconf_mutable AWS_SECRET_ACCESS_KEY "$AWS_SECRET_ACCESS_KEY"
+  fi
 
   _debug "First detect the root zone"
   if ! _get_root "$fulldomain"; then
@@ -78,6 +85,11 @@ dns_aws_rm() {
 
   AWS_ACCESS_KEY_ID="${AWS_ACCESS_KEY_ID:-$(_readaccountconf_mutable AWS_ACCESS_KEY_ID)}"
   AWS_SECRET_ACCESS_KEY="${AWS_SECRET_ACCESS_KEY:-$(_readaccountconf_mutable AWS_SECRET_ACCESS_KEY)}"
+
+  if [ -z "$AWS_ACCESS_KEY_ID" ] || [ -z "$AWS_SECRET_ACCESS_KEY" ]; then
+    _use_instance_role
+  fi
+
   _debug "First detect the root zone"
   if ! _get_root "$fulldomain"; then
     _err "invalid domain"
@@ -162,6 +174,37 @@ _get_root() {
   return 1
 }
 
+_use_instance_role() {
+  _url="http://169.254.169.254/latest/meta-data/iam/security-credentials/"
+  _debug "_url" "$_url"
+  if ! _get "$_url" true 1 | _head_n 1 | grep -Fq 200; then
+    _err "Unable to fetch IAM role from AWS instance metadata."
+    return
+  fi
+  _aws_role=$(_get "$_url" "" 1)
+  _debug "_aws_role" "$_aws_role"
+  _aws_creds="$(
+    _get "$_url$_aws_role" "" 1 \
+      | _normalizeJson \
+      | tr '{,}' '\n' \
+      | while read -r _line; do
+        _key="$(echo "${_line%%:*}" | tr -d '"')"
+        _value="${_line#*:}"
+        _debug3 "_key" "$_key"
+        _secure_debug3 "_value" "$_value"
+        case "$_key" in
+          AccessKeyId) echo "AWS_ACCESS_KEY_ID=$_value" ;;
+          SecretAccessKey) echo "AWS_SECRET_ACCESS_KEY=$_value" ;;
+          Token) echo "AWS_SESSION_TOKEN=$_value" ;;
+        esac
+      done \
+        | paste -sd' ' -
+  )"
+  _secure_debug "_aws_creds" "$_aws_creds"
+  eval "$_aws_creds"
+  _using_role=true
+}
+
 #method uri qstr data
 aws_rest() {
   mtd="$1"