1 files changed, 66 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/virtualisation/ec2-metadata-fetcher.sh b/nixpkgs/nixos/modules/virtualisation/ec2-metadata-fetcher.sh
new file mode 100644
index 000000000000..716aff7c22fb
--- /dev/null
+++ b/nixpkgs/nixos/modules/virtualisation/ec2-metadata-fetcher.sh
@@ -0,0 +1,66 @@
+metaDir=/etc/ec2-metadata
+mkdir -m 0755 -p "$metaDir"
+rm -f "$metaDir/*"
+
+get_imds_token() {
+  # retry-delay of 1 selected to give the system a second to get going,
+  # but not add a lot to the bootup time
+  curl \
+    --silent \
+    --show-error \
+    --retry 3 \
+    --retry-delay 1 \
+    --fail \
+    -X PUT \
+    --connect-timeout 1 \
+    -H "X-aws-ec2-metadata-token-ttl-seconds: 600" \
+    http://169.254.169.254/latest/api/token
+}
+
+preflight_imds_token() {
+  # retry-delay of 1 selected to give the system a second to get going,
+  # but not add a lot to the bootup time
+  curl \
+    --silent \
+    --show-error \
+    --retry 3 \
+    --retry-delay 1 \
+    --fail \
+    --connect-timeout 1 \
+    -H "X-aws-ec2-metadata-token: $IMDS_TOKEN" \
+    -o /dev/null \
+    http://169.254.169.254/1.0/meta-data/instance-id
+}
+
+try=1
+while [ $try -le 3 ]; do
+  echo "(attempt $try/3) getting an EC2 instance metadata service v2 token..."
+  IMDS_TOKEN=$(get_imds_token) && break
+  try=$((try + 1))
+  sleep 1
+done
+
+if [ "x$IMDS_TOKEN" == "x" ]; then
+  echo "failed to fetch an IMDS2v token."
+fi
+
+try=1
+while [ $try -le 10 ]; do
+  echo "(attempt $try/10) validating the EC2 instance metadata service v2 token..."
+  preflight_imds_token && break
+  try=$((try + 1))
+  sleep 1
+done
+
+echo "getting EC2 instance metadata..."
+
+get_imds() {
+  # --fail to avoid populating missing files with 404 HTML response body
+  # || true to allow the script to continue even when encountering a 404
+  curl --silent --show-error --fail --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" "$@" || true
+}
+
+get_imds -o "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
+(umask 077 && get_imds -o "$metaDir/user-data" http://169.254.169.254/1.0/user-data)
+get_imds -o "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
+get_imds -o "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key