common: setup default VPC/subnet for public IPs

If a template requests a public IP for the instance being created, and
no VPC or subnet is, we get the default VPC ID and a random subnet in
this VPC to associate for the instance being created.

This fixes a bug where the public IP was requested, but because no
subnet was specified, it wasn't associated explicitely.

builder/common/step_network_info.go

@@ -7,9 +7,11 @@ import (
 	"math/rand"
 	"sort"
 
+	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/packer-plugin-sdk/multistep"
 	packersdk "github.com/hashicorp/packer-plugin-sdk/packer"
+	confighelper "github.com/hashicorp/packer-plugin-sdk/template/config"
 )
 
 // StepNetworkInfo queries AWS for information about
@@ -20,13 +22,14 @@ import (
 //   subnet_id string - the Subnet ID
 //   availability_zone string - the AZ name
 type StepNetworkInfo struct {
-	VpcId               string
-	VpcFilter           VpcFilterOptions
-	SubnetId            string
-	SubnetFilter        SubnetFilterOptions
-	AvailabilityZone    string
-	SecurityGroupIds    []string
-	SecurityGroupFilter SecurityGroupFilterOptions
+	VpcId                    string
+	VpcFilter                VpcFilterOptions
+	SubnetId                 string
+	SubnetFilter             SubnetFilterOptions
+	AssociatePublicIpAddress confighelper.Trilean
+	AvailabilityZone         string
+	SecurityGroupIds         []string
+	SecurityGroupFilter      SecurityGroupFilterOptions
 }
 
 type subnetsSort []*ec2.Subnet
@@ -158,6 +161,66 @@ func (s *StepNetworkInfo) Run(ctx context.Context, state multistep.StateBag) mul
 		}
 	}
 
+	if s.AssociatePublicIpAddress != confighelper.TriUnset && s.SubnetId == "" {
+		ui.Say(fmt.Sprintf("Setting public IP address to %t on instance without a subnet ID",
+			*s.AssociatePublicIpAddress.ToBoolPointer()))
+		if s.VpcId == "" {
+			ui.Say("No VPC ID provided, Packer will choose one from the provided or default VPC")
+			vpcs, err := ec2conn.DescribeVpcs(&ec2.DescribeVpcsInput{
+				Filters: []*ec2.Filter{
+					{
+						Name:   aws.String("is-default"),
+						Values: []*string{aws.String("true")},
+					},
+				},
+			})
+			if err != nil {
+				err := fmt.Errorf("Failed to describe VPCs: %s", err)
+				state.Put("error", err)
+				ui.Error(err.Error())
+				return multistep.ActionHalt
+			}
+
+			if len(vpcs.Vpcs) != 1 {
+				err := fmt.Errorf("No default VPC found, please set one up for associating a public IP address to the instance")
+				state.Put("error", err)
+				ui.Error(err.Error())
+				return multistep.ActionHalt
+			}
+			defaultVPC := vpcs.Vpcs[0]
+
+			s.VpcId = *defaultVPC.VpcId
+		}
+
+		var err error
+
+		ui.Say(fmt.Sprintf("Inferring subnet from the selected VPC %q", s.VpcId))
+		params := &ec2.DescribeSubnetsInput{}
+		filters := map[string]string{
+			"vpc-id": s.VpcId,
+			"state":  "available",
+		}
+		params.Filters, err = buildEc2Filters(filters)
+		if err != nil {
+			err := fmt.Errorf("Failed to prepare subnet filters: %s", err)
+			state.Put("error", err)
+			ui.Error(err.Error())
+			return multistep.ActionHalt
+		}
+		subnets, err := ec2conn.DescribeSubnets(params)
+		if err != nil {
+			err := fmt.Errorf("Failed to describe subnets: %s", err)
+			state.Put("error", err)
+			ui.Error(err.Error())
+			return multistep.ActionHalt
+		}
+
+		subnet := mostFreeSubnet(subnets.Subnets)
+		s.SubnetId = *subnet.SubnetId
+
+		ui.Say(fmt.Sprintf("Set subnet as %q", s.SubnetId))
+	}
+
 	state.Put("vpc_id", s.VpcId)
 	state.Put("availability_zone", s.AvailabilityZone)
 	state.Put("subnet_id", s.SubnetId)

builder/common/step_run_source_instance.go

@@ -214,6 +214,9 @@ func (s *StepRunSourceInstance) Run(ctx context.Context, state multistep.StateBa
 	subnetId := state.Get("subnet_id").(string)
 
 	if subnetId != "" && s.AssociatePublicIpAddress != confighelper.TriUnset {
+		ui.Say(fmt.Sprintf("changing public IP address config to %t for instance on subnet %q",
+			*s.AssociatePublicIpAddress.ToBoolPointer(),
+			subnetId))
 		runOpts.NetworkInterfaces = []*ec2.InstanceNetworkInterfaceSpecification{
 			{
 				DeviceIndex:              aws.Int64(0),

builder/common/step_run_spot_instance.go

@@ -114,6 +114,8 @@ func (s *StepRunSpotInstance) CreateTemplateData(userData *string, az string,
 
 	}
 
+	ui := state.Get("ui").(packersdk.Ui)
+
 	iamInstanceProfile := aws.String(state.Get("iamInstanceProfile").(string))
 
 	// Create a launch template.
@@ -142,6 +144,9 @@ func (s *StepRunSpotInstance) CreateTemplateData(userData *string, az string,
 			SubnetId:            aws.String(subnetId),
 		}
 		if s.AssociatePublicIpAddress != confighelper.TriUnset {
+			ui.Say(fmt.Sprintf("changing public IP address config to %t for instance on subnet %q",
+				*s.AssociatePublicIpAddress.ToBoolPointer(),
+				subnetId))
 			networkInterface.SetAssociatePublicIpAddress(*s.AssociatePublicIpAddress.ToBoolPointer())
 		}
 		templateData.SetNetworkInterfaces([]*ec2.LaunchTemplateInstanceNetworkInterfaceSpecificationRequest{&networkInterface})

builder/ebs/builder.go

@@ -297,13 +297,14 @@ func (b *Builder) Run(ctx context.Context, ui packersdk.Ui, hook packersdk.Hook)
 			AMIVirtType:              b.config.AMIVirtType,
 		},
 		&awscommon.StepNetworkInfo{
-			VpcId:               b.config.VpcId,
-			VpcFilter:           b.config.VpcFilter,
-			SecurityGroupIds:    b.config.SecurityGroupIds,
-			SecurityGroupFilter: b.config.SecurityGroupFilter,
-			SubnetId:            b.config.SubnetId,
-			SubnetFilter:        b.config.SubnetFilter,
-			AvailabilityZone:    b.config.AvailabilityZone,
+			VpcId:                    b.config.VpcId,
+			VpcFilter:                b.config.VpcFilter,
+			SecurityGroupIds:         b.config.SecurityGroupIds,
+			SecurityGroupFilter:      b.config.SecurityGroupFilter,
+			SubnetId:                 b.config.SubnetId,
+			SubnetFilter:             b.config.SubnetFilter,
+			AvailabilityZone:         b.config.AvailabilityZone,
+			AssociatePublicIpAddress: b.config.AssociatePublicIpAddress,
 		},
 		&awscommon.StepKeyPair{
 			Debug:        b.config.PackerDebug,

builder/ebs/builder_acc_test.go

@@ -1212,6 +1212,85 @@ func TestAccBuilder_EBSWithSSHPassword_NoTempKeyCreated(t *testing.T) {
 	acctest.TestPlugin(t, testcase)
 }
 
+func TestAccBuilder_SpotInstanceWithPublicIPAddressExplicitelySet(t *testing.T) {
+	nonSpotInstance := amazon_acc.AMIHelper{
+		Region: "us-east-1",
+		Name:   fmt.Sprintf("packer-ebs-explicit-public-ip-%d", time.Now().Unix()),
+	}
+
+	spotInstance := amazon_acc.AMIHelper{
+		Region: "us-east-1",
+		Name:   fmt.Sprintf("packer-ebs-spot-explicit-public-ip-%d", time.Now().Unix()),
+	}
+	tests := []struct {
+		name      string
+		IPVal     bool
+		amiSetup  amazon_acc.AMIHelper
+		template  string
+		expectErr bool
+	}{
+		{
+			"Spot instance, with public IP explicitely set",
+			true,
+			spotInstance,
+			testSetupPublicIPWithoutVPCOrSubnetOnSpotInstance,
+			false,
+		},
+		{
+			"Spot instance, with public IP explicitely unset",
+			false,
+			spotInstance,
+			testSetupPublicIPWithoutVPCOrSubnetOnSpotInstance,
+			true, // We expect an error without a public IP since no outbound connections work in this case, so SSM doesn't work with the current config
+		},
+		{
+			"Non-Spot instance, with public IP explicitely set",
+			true,
+			nonSpotInstance,
+			testSetupPublicIPWithoutVPCOrSubnet,
+			false,
+		},
+		{
+			"Non-Spot instance, with public IP explicitely unset",
+			false,
+			nonSpotInstance,
+			testSetupPublicIPWithoutVPCOrSubnet,
+			true, // We expect an error without a public IP since no outbound connections work in this case, so SSM doesn't work with the current config
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			testcase := &acctest.PluginTestCase{
+				Name:     tt.name,
+				Template: fmt.Sprintf(tt.template, tt.amiSetup.Name, tt.IPVal),
+				Check: func(buildCommand *exec.Cmd, logfile string) error {
+					if (buildCommand.ProcessState.ExitCode() != 0) != tt.expectErr {
+						return fmt.Errorf("Bad exit code, expected %t error, got %d. Logfile: %s",
+							tt.expectErr,
+							buildCommand.ProcessState.ExitCode(),
+							logfile)
+					}
+
+					logs, err := os.ReadFile(logfile)
+					if err != nil {
+						return fmt.Errorf("couldn't read logs from logfile %s: %s", logfile, err)
+					}
+
+					expectMsg := fmt.Sprintf("changing public IP address config to %t for instance on subnet", tt.IPVal)
+
+					if !strings.Contains(string(logs), expectMsg) {
+						return fmt.Errorf("did not change the public IP setting for the instance")
+					}
+
+					return nil
+				},
+			}
+			acctest.TestPlugin(t, testcase)
+		})
+	}
+}
+
 const testBuilderAccBasic = `
 {
 	"builders": [{
@@ -1541,6 +1620,56 @@ build {
 }
 `
 
+const testSetupPublicIPWithoutVPCOrSubnet = `
+source "amazon-ebs" "test_build" {
+  region                      = "us-east-1"
+  ami_name                    = "%s"
+  source_ami                  = "ami-06e46074ae430fba6" # Amazon Linux 2023 x86-64
+  instance_type               = "t2.micro"
+  communicator                = "ssh"
+  ssh_username                = "ec2-user"
+  ssh_interface               = "session_manager"
+  iam_instance_profile        = "SSMInstanceProfile"
+  associate_public_ip_address = %t
+  skip_create_ami             = true
+}
+
+build {
+  sources = ["amazon-ebs.test_build"]
+}
+`
+
+const testSetupPublicIPWithoutVPCOrSubnetOnSpotInstance = `
+source "amazon-ebs" "test" {
+  region                      = "us-east-1"
+  spot_price                  = "auto"
+  source_ami                  = "ami-06e46074ae430fba6" # Amazon Linux 2023 x86-64
+  instance_type               = "t2.micro"
+  ssh_username                = "ec2-user"
+  ssh_interface               = "session_manager"
+  iam_instance_profile        = "SSMInstanceProfile"
+  ami_name                    = "%s"
+  skip_create_ami             = true
+  associate_public_ip_address = %t
+  temporary_iam_instance_profile_policy_document {
+    Version = "2012-10-17"
+    Statement {
+      Effect = "Allow"
+      Action = [
+        "ec2:GetDefaultCreditSpecification",
+        "ec2:DescribeInstanceTypeOfferings",
+        "ec2:DescribeInstanceCreditSpecifications"
+      ]
+      Resource = ["*"]
+    }
+  }
+}
+
+build {
+  sources = ["source.amazon-ebs.test"]
+}
+`
+
 const testWindowsFastBoot = `
 source "amazon-ebs" "windows-fastboot" {
 	ami_name             = "%s"

builder/ebssurrogate/builder.go

@@ -325,13 +325,14 @@ func (b *Builder) Run(ctx context.Context, ui packersdk.Ui, hook packersdk.Hook)
 			AMIVirtType:              b.config.AMIVirtType,
 		},
 		&awscommon.StepNetworkInfo{
-			VpcId:               b.config.VpcId,
-			VpcFilter:           b.config.VpcFilter,
-			SecurityGroupIds:    b.config.SecurityGroupIds,
-			SecurityGroupFilter: b.config.SecurityGroupFilter,
-			SubnetId:            b.config.SubnetId,
-			SubnetFilter:        b.config.SubnetFilter,
-			AvailabilityZone:    b.config.AvailabilityZone,
+			VpcId:                    b.config.VpcId,
+			VpcFilter:                b.config.VpcFilter,
+			SecurityGroupIds:         b.config.SecurityGroupIds,
+			SecurityGroupFilter:      b.config.SecurityGroupFilter,
+			SubnetId:                 b.config.SubnetId,
+			SubnetFilter:             b.config.SubnetFilter,
+			AvailabilityZone:         b.config.AvailabilityZone,
+			AssociatePublicIpAddress: b.config.AssociatePublicIpAddress,
 		},
 		&awscommon.StepKeyPair{
 			Debug:        b.config.PackerDebug,

builder/ebsvolume/builder.go

@@ -272,13 +272,14 @@ func (b *Builder) Run(ctx context.Context, ui packersdk.Ui, hook packersdk.Hook)
 			AmiFilters:               b.config.SourceAmiFilter,
 		},
 		&awscommon.StepNetworkInfo{
-			VpcId:               b.config.VpcId,
-			VpcFilter:           b.config.VpcFilter,
-			SecurityGroupIds:    b.config.SecurityGroupIds,
-			SecurityGroupFilter: b.config.SecurityGroupFilter,
-			SubnetId:            b.config.SubnetId,
-			SubnetFilter:        b.config.SubnetFilter,
-			AvailabilityZone:    b.config.AvailabilityZone,
+			VpcId:                    b.config.VpcId,
+			VpcFilter:                b.config.VpcFilter,
+			SecurityGroupIds:         b.config.SecurityGroupIds,
+			SecurityGroupFilter:      b.config.SecurityGroupFilter,
+			SubnetId:                 b.config.SubnetId,
+			SubnetFilter:             b.config.SubnetFilter,
+			AvailabilityZone:         b.config.AvailabilityZone,
+			AssociatePublicIpAddress: b.config.AssociatePublicIpAddress,
 		},
 		&awscommon.StepKeyPair{
 			Debug:        b.config.PackerDebug,

builder/instance/builder.go

@@ -342,13 +342,14 @@ func (b *Builder) Run(ctx context.Context, ui packersdk.Ui, hook packersdk.Hook)
 			AMIVirtType:              b.config.AMIVirtType,
 		},
 		&awscommon.StepNetworkInfo{
-			VpcId:               b.config.VpcId,
-			VpcFilter:           b.config.VpcFilter,
-			SecurityGroupIds:    b.config.SecurityGroupIds,
-			SecurityGroupFilter: b.config.SecurityGroupFilter,
-			SubnetId:            b.config.SubnetId,
-			SubnetFilter:        b.config.SubnetFilter,
-			AvailabilityZone:    b.config.AvailabilityZone,
+			VpcId:                    b.config.VpcId,
+			VpcFilter:                b.config.VpcFilter,
+			SecurityGroupIds:         b.config.SecurityGroupIds,
+			SecurityGroupFilter:      b.config.SecurityGroupFilter,
+			SubnetId:                 b.config.SubnetId,
+			SubnetFilter:             b.config.SubnetFilter,
+			AvailabilityZone:         b.config.AvailabilityZone,
+			AssociatePublicIpAddress: b.config.AssociatePublicIpAddress,
 		},
 		&awscommon.StepKeyPair{
 			Debug:        b.config.PackerDebug,