nixos/ec2: use only curl in metadata fetcher, log to console

We don't need both wget and curl, so let's use only curl (which is
part of a minimal NixOS closure, unlike wget).

Logging to the console is helpful for debugging.
This commit is contained in:
Linus Heckemann 2022-11-17 19:44:52 +01:00
parent 6fb582e030
commit 36ca2b495f
3 changed files with 71 additions and 82 deletions

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@ -75,12 +75,11 @@ in
systemd.services.fetch-ec2-metadata = {
wantedBy = [ "multi-user.target" ];
path = [ pkgs.wget ];
script = pkgs.callPackage ./ec2-metadata-fetcher.nix {
targetRoot = "/";
wgetExtraOptions = "";
};
after = ["network-online.target"];
path = [ pkgs.curl ];
script = builtins.readFile ./ec2-metadata-fetcher.sh;
serviceConfig.Type = "oneshot";
serviceConfig.StandardOutput = "journal+console";
};
# Allow root logins only using the SSH key that the user specified

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@ -1,77 +0,0 @@
{ 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.
#
# Also note: OpenStack's metadata service for its instances aims to be
# compatible with the EC2 IMDS. Where possible, try to keep the set of
# fetched metadata in sync with ./openstack-metadata-fetcher.nix .
''
metaDir=${targetRoot}etc/ec2-metadata
mkdir -m 0755 -p "$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}/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..."
wget_imds() {
wget ${wgetExtraOptions} --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" "$@";
}
wget_imds -O "$metaDir/ami-manifest-path" http://169.254.169.254/1.0/meta-data/ami-manifest-path || true
(umask 077 && wget_imds -O "$metaDir/user-data" http://169.254.169.254/1.0/user-data || true)
wget_imds -O "$metaDir/hostname" http://169.254.169.254/1.0/meta-data/hostname || true
wget_imds -O "$metaDir/public-keys-0-openssh-key" http://169.254.169.254/1.0/meta-data/public-keys/0/openssh-key || true
''

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@ -0,0 +1,67 @@
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() {
# Intentionally no --fail here, so that we proceed even if e.g. a
# 404 was returned (but we still fail if we can't reach the IMDS
# server).
curl --silent --show-error --header "X-aws-ec2-metadata-token: $IMDS_TOKEN" "$@"
}
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