chore(cloud-init): truncate hostnames in determineHostname

Too long hostname are not allowed and potentially breaking things. Instead of individually checking the hostname in each metadata provider, we adjust the hostname length when it's used to be set

Author: Rick Rackow

coreos-cloudinit.go

@@ -23,6 +23,7 @@ import (
 	"log"
 	"os"
 	"runtime"
+	"strings"
 	"sync"
 	"time"
 
@@ -285,6 +286,14 @@ func determineHostname(md datasource.Metadata, udata *initialize.UserData) strin
 			hostname = udataHostname
 		}
 	}
+	if len(hostname) > 63 {
+		log.Printf("Hostname too long. Truncating hostname %s to %s", hostname, strings.Split(hostname, ".")[0])
+		hostname = strings.Split(hostname, ".")[0]
+		if len(hostname) > 63 {
+			log.Printf("Hostname still too long. Truncating hostname %s further to 63 bytes (%s)", hostname, hostname[:63])
+			hostname = hostname[:63]
+		}
+	}
 	return hostname
 }
 

coreos-cloudinit_test.go

@@ -18,6 +18,10 @@ import (
 	"bytes"
 	"encoding/base64"
 	"errors"
+	"github.com/flatcar/coreos-cloudinit/datasource"
+	"github.com/flatcar/coreos-cloudinit/initialize"
+	"net"
+	"reflect"
 	"testing"
 )
 
@@ -75,3 +79,75 @@ func TestDecompressIfGzip(t *testing.T) {
 	}
 
 }
+
+func TestDetermineHostname(t *testing.T) {
+	for _, tt := range []struct {
+		metaData datasource.Metadata
+		uData    *initialize.UserData
+		expect   string
+	}{
+		{
+			metaData: datasource.Metadata{
+				PublicIPv4:    net.ParseIP("1.2.3.4"),
+				PublicIPv6:    net.ParseIP("5.6.7.8"),
+				PrivateIPv4:   net.ParseIP("1.2.3.4"),
+				PrivateIPv6:   net.ParseIP("5.6.7.8"),
+				Hostname:      "regular-name",
+				SSHPublicKeys: map[string]string{"my": "key"},
+				NetworkConfig: net.Interface{
+					Index:        0,
+					MTU:          0,
+					Name:         "some-interface",
+					HardwareAddr: nil,
+					Flags:        0,
+				},
+			},
+			uData:  nil,
+			expect: "regular-name",
+		},
+		{
+			metaData: datasource.Metadata{
+				PublicIPv4:    net.ParseIP("1.2.3.4"),
+				PublicIPv6:    net.ParseIP("5.6.7.8"),
+				PrivateIPv4:   net.ParseIP("1.2.3.4"),
+				PrivateIPv6:   net.ParseIP("5.6.7.8"),
+				Hostname:      "this-hostname-is-larger-than-sixty-three-characters-long-and.will.be.truncated.locale",
+				SSHPublicKeys: map[string]string{"my": "key"},
+				NetworkConfig: net.Interface{
+					Index:        0,
+					MTU:          0,
+					Name:         "some-interface",
+					HardwareAddr: nil,
+					Flags:        0,
+				},
+			},
+			uData:  nil,
+			expect: "this-hostname-is-larger-than-sixty-three-characters-long-and",
+		},
+		{
+			metaData: datasource.Metadata{
+				PublicIPv4:    net.ParseIP("1.2.3.4"),
+				PublicIPv6:    net.ParseIP("5.6.7.8"),
+				PrivateIPv4:   net.ParseIP("1.2.3.4"),
+				PrivateIPv6:   net.ParseIP("5.6.7.8"),
+				Hostname:      "this-hostname-is-larger-than-sixty-three-characters-long-and-will-be-truncated.local",
+				SSHPublicKeys: map[string]string{"my": "key"},
+				NetworkConfig: net.Interface{
+					Index:        0,
+					MTU:          0,
+					Name:         "some-interface",
+					HardwareAddr: nil,
+					Flags:        0,
+				},
+			},
+			uData:  nil,
+			expect: "this-hostname-is-larger-than-sixty-three-characters-long-and-wi",
+		},
+	} {
+		hostname := determineHostname(tt.metaData, tt.uData)
+		if !reflect.DeepEqual(tt.expect, hostname) {
+			t.Fatalf("Bad hostname, want %s, got %s", tt.expect, hostname)
+		}
+
+	}
+}

datasource/metadata/ec2/metadata.go

@@ -78,11 +78,6 @@ func (ms metadataService) FetchMetadata() (datasource.Metadata, error) {
 	}
 
 	if hostname, err := ms.fetchAttribute(fmt.Sprintf("%s/hostname", ms.MetadataUrl())); err == nil {
-		hostname := strings.Split(hostname, ".")[0]
-		if len(hostname) > 63 {
-			log.Printf("Truncating hostname %s to 63 bytes (%s)", hostname, hostname[:63])
-			hostname = hostname[:63]
-		}
 		metadata.Hostname = hostname
 	} else if _, ok := err.(pkg.ErrNotFound); !ok {
 		return metadata, err

datasource/metadata/ec2/metadata_test.go

@@ -194,24 +194,6 @@ func TestFetchMetadata(t *testing.T) {
 				SSHPublicKeys: map[string]string{"test1": "key"},
 			},
 		},
-		{
-			root:         "/",
-			metadataPath: "2009-04-04/meta-data",
-			resources: map[string]string{
-				"/2009-04-04/meta-data/hostname":                  "this-hostname-is-larger-than-sixty-three-characters-long-and-will-be-truncated.local",
-				"/2009-04-04/meta-data/local-ipv4":                "1.2.3.4",
-				"/2009-04-04/meta-data/public-ipv4":               "5.6.7.8",
-				"/2009-04-04/meta-data/public-keys":               "0=test1\n",
-				"/2009-04-04/meta-data/public-keys/0":             "openssh-key",
-				"/2009-04-04/meta-data/public-keys/0/openssh-key": "key",
-			},
-			expect: datasource.Metadata{
-				Hostname:      "this-hostname-is-larger-than-sixty-three-characters-long-and-wi",
-				PrivateIPv4:   net.ParseIP("1.2.3.4"),
-				PublicIPv4:    net.ParseIP("5.6.7.8"),
-				SSHPublicKeys: map[string]string{"test1": "key"},
-			},
-		},
 		{
 			clientErr: pkg.ErrTimeout{Err: fmt.Errorf("test error")},
 			expectErr: pkg.ErrTimeout{Err: fmt.Errorf("test error")},