nixos/modules/virtualisation/ec2-metadata-fetcher.sh

   1 metaDir=/etc/ec2-metadata
   2 mkdir -m 0755 -p "$metaDir"
   3 rm -f "$metaDir/*"
   4
   5 get_imds_token() {
   6   # retry-delay of 1 selected to give the system a second to get going,
   7   # but not add a lot to the bootup time
   8   curl \
   9     --silent \
  10     --show-error \
  11     --retry 3 \
  12     --retry-delay 1 \
  13     --fail \
  14     -X PUT \
  15     --connect-timeout 1 \
  16     -H "X-aws-ec2-metadata-token-ttl-seconds: 600" \
  17     http://169.254.169.254/latest/api/token
  18 }
  19
  20 preflight_imds_token() {
  21   # retry-delay of 1 selected to give the system a second to get going,
  22   # but not add a lot to the bootup time
  23   curl \
  24     --silent \
  25     --show-error \
  26     --retry 3 \
  27     --retry-delay 1 \
  28     --fail \
  29     --connect-timeout 1 \
  30     -H "X-aws-ec2-metadata-token: $IMDS_TOKEN" \
  31     -o /dev/null \
  32     http://169.254.169.254/1.0/meta-data/instance-id
  33 }
  34
  35 try=1
  36 while [ $try -le 3 ]; do
  37   echo "(attempt $try/3) getting an EC2 instance metadata service v2 token..."
  38   IMDS_TOKEN=$(get_imds_token) && break
  39   try=$((try + 1))
  40   sleep 1
  41 done
  42
  43 if [ "x$IMDS_TOKEN" == "x" ]; then
  44   echo "failed to fetch an IMDS2v token."
  45 fi
  46
  47 try=1
  48 while [ $try -le 10 ]; do
  49   echo "(attempt $try/10) validating the EC2 instance metadata service v2 token..."
  50   preflight_imds_token && break
  51   try=$((try + 1))
  52   sleep 1
  53 done
  54
  55 echo "getting EC2 instance metadata..."
  56
  57 get_imds() {
  58   # --fail to avoid populating missing files with 404 HTML response body
  59   # || true to allow the script to continue even when encountering a 404
  60   curl --silent --show-error --fail --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" "$@" || true
  61 }
  62
  63 get_imds -o "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
  64 (umask 077 && get_imds -o "$metaDir/user-data" http://169.254.169.254/1.0/user-data)
  65 get_imds -o "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
  66 get_imds -o "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key