Merge pull request #104193 from grahamc/ec2-metadata-imdsv2

NixOS EC2 AMI: Support IMDSv2

nixos/modules/virtualisation/amazon-image.nix

···
 let
   cfg = config.ec2;
   metadataFetcher = import ./ec2-metadata-fetcher.nix {
+    inherit (pkgs) curl;
     targetRoot = "$targetRoot/";
     wgetExtraOptions = "-q";
   };

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

···
-{ targetRoot, wgetExtraOptions }:
+{ curl, targetRoot, wgetExtraOptions }:
+# Note: be very cautious about dependencies, each dependency grows
+# the closure of the initrd. Ideally we would not even require curl,
+# but there is no reasonable way to send an HTTP PUT request without
+# it. Note: do not be fooled: the wget referenced in this script
+# is busybox's wget, not the fully featured one with --method support.
+#
+# Make sure that every package you depend on here is already listed as
+# a channel blocker for both the full-sized and small channels.
+# Otherwise, we risk breaking user deploys in released channels.
 ''
   metaDir=${targetRoot}etc/ec2-metadata
   mkdir -m 0755 -p "$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}/bin/curl \
+      -v \
+      --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}/bin/curl \
+      -v \
+      --retry 3 \
+      --retry-delay 1 \
+      --fail \
+      --connect-timeout 1 \
+      -H "X-aws-ec2-metadata-token: $IMDS_TOKEN" \
+      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..."
 
   if ! [ -e "$metaDir/ami-manifest-path" ]; then
-    wget ${wgetExtraOptions} -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
+    wget ${wgetExtraOptions} --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
   fi
 
   if ! [ -e "$metaDir/user-data" ]; then
-    wget ${wgetExtraOptions} -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
+    wget ${wgetExtraOptions} --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
   fi
 
   if ! [ -e "$metaDir/hostname" ]; then
-    wget ${wgetExtraOptions} -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
+    wget ${wgetExtraOptions} --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
   fi
 
   if ! [ -e "$metaDir/public-keys-0-openssh-key" ]; then
-    wget ${wgetExtraOptions} -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
+    wget ${wgetExtraOptions} --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
   fi
 ''

nixos/modules/virtualisation/openstack-config.nix

···
 with lib;
 
 let
-  metadataFetcher = import ./ec2-metadata-fetcher.nix {
+  metadataFetcher = import ./openstack-metadata-fetcher.nix {
     targetRoot = "/";
     wgetExtraOptions = "--retry-connrefused";
   };

nixos/modules/virtualisation/openstack-metadata-fetcher.nix

···
+{ targetRoot, wgetExtraOptions }:
+''
+  metaDir=${targetRoot}etc/ec2-metadata
+  mkdir -m 0755 -p "$metaDir"
+
+  echo "getting EC2 instance metadata..."
+
+  if ! [ -e "$metaDir/ami-manifest-path" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path
+  fi
+
+  if ! [ -e "$metaDir/user-data" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data && chmod 600 "$metaDir/user-data"
+  fi
+
+  if ! [ -e "$metaDir/hostname" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname
+  fi
+
+  if ! [ -e "$metaDir/public-keys-0-openssh-key" ]; then
+    wget ${wgetExtraOptions} -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key
+  fi
+''

nixos/release-combined.nix

···
         [ "nixos.channel" ]
         (onFullSupported "nixos.dummy")
         (onAllSupported "nixos.iso_minimal")
+        (onAllSupported "nixos.amazonImage")
         (onSystems ["x86_64-linux"] "nixos.iso_plasma5")
         (onSystems ["x86_64-linux"] "nixos.iso_gnome")
         (onFullSupported "nixos.manual")

nixos/release-small.nix

···
       [ "nixos.channel"
         "nixos.dummy.x86_64-linux"
         "nixos.iso_minimal.x86_64-linux"
+        "nixos.amazonImage.x86_64-linux"
         "nixos.manual.x86_64-linux"
         "nixos.tests.boot.biosCdrom.x86_64-linux"
         "nixos.tests.containers-imperative.x86_64-linux"