feat(gardener#161): adds a prompt when providing /32 CIDR ranges

including an --force flag that hides such prompts for non-interactive/script usage

pkg/cmd/ssh/export_test.go

@@ -10,6 +10,8 @@ import (
 	"context"
 	"os"
 	"time"
+
+	"github.com/gardener/gardenctl-v2/internal/util"
 )
 
 func SetBastionAvailabilityChecker(f func(hostname string, privateKey []byte) error) {
@@ -42,3 +44,9 @@ func SetKeepAliveInterval(d time.Duration) {
 
 	keepAliveInterval = d
 }
+
+var Confirm = confirm
+
+func SetConfirm(f func(ioStreams util.IOStreams, question string, defaultAnswer bool) bool) {
+	confirm = f
+}

pkg/cmd/ssh/options.go

@@ -7,6 +7,8 @@ SPDX-License-Identifier: Apache-2.0
 package ssh
 
 import (
+	"bufio"
+	"bytes"
 	"context"
 	"crypto/rand"
 	"crypto/rsa"
@@ -151,6 +153,34 @@ var (
 
 		return cmd.Run()
 	}
+
+	// Displays a prompt to the user to confirm (yes/no) something
+	confirm = func(ioStreams util.IOStreams, question string, defaultAnswer bool) bool {
+		reader := bufio.NewReader(ioStreams.In)
+
+		choices := "y/N"
+		if defaultAnswer {
+			choices = "n/Y"
+		}
+
+		for {
+			fmt.Fprint(ioStreams.Out, question+" ["+choices+"]: ")
+
+			str, _ := reader.ReadString('\n')
+
+			str = strings.TrimSpace(str)
+			str = strings.ToLower(str)
+
+			switch str {
+			case "":
+				return defaultAnswer
+			case "n", "no":
+				return false
+			case "y", "yes":
+				return true
+			}
+		}
+	}
 )
 
 // SSHOptions is a struct to support ssh command
@@ -199,6 +229,10 @@ type SSHOptions struct {
 	// bastion once it exits. By default it deletes it, but we allow the user to
 	// keep it for debugging purposes.
 	KeepBastion bool
+
+	// Force will silence warnings and interactive prompts. The latter happens if the user
+	// specifies a /32/large/ CIDR range which usually requires the users confirmation.
+	Force bool
 }
 
 // NewSSHOptions returns initialized SSHOptions
@@ -301,9 +335,18 @@ func (o *SSHOptions) Validate() error {
 	}
 
 	for _, cidr := range o.CIDRs {
-		if _, _, err := net.ParseCIDR(cidr); err != nil {
+		_, netIP, err := net.ParseCIDR(cidr)
+		if err != nil {
 			return fmt.Errorf("CIDR %q is invalid: %w", cidr, err)
 		}
+
+		if !o.Force && bytes.Compare(netIP.Mask, []byte{0, 0, 0, 0}) <= 0 {
+			question := fmt.Sprintf("Large CIDR range %s compromises security. Continue?", cidr)
+			if !confirm(o.IOStreams, question, false) {
+				// return fmt.Errorf("")
+				os.Exit(0)
+			}
+		}
 	}
 
 	content, err := os.ReadFile(o.SSHPublicKeyFile)

pkg/cmd/ssh/ssh.go

@@ -42,6 +42,7 @@ func NewCmdSSH(f util.Factory, o *SSHOptions) *cobra.Command {
 	cmd.Flags().StringVar(&o.SSHPublicKeyFile, "public-key-file", "", "Path to the file that contains a public SSH key. If not given, a temporary keypair will be generated.")
 	cmd.Flags().DurationVar(&o.WaitTimeout, "wait-timeout", o.WaitTimeout, "Maximum duration to wait for the bastion to become available.")
 	cmd.Flags().BoolVar(&o.KeepBastion, "keep-bastion", o.KeepBastion, "Do not delete immediately when gardenctl exits (Bastions will be garbage-collected after some time)")
+	cmd.Flags().BoolVar(&o.Force, "force", o.Force, "Do not show warnings and do not prompt for confirmation. Does not affect access control warnings.")
 
 	return cmd
 }

pkg/cmd/ssh/ssh_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/gardener/gardener/pkg/utils/secrets"
 	"github.com/golang/mock/gomock"
 	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/ginkgo/extensions/table"
 	. "github.com/onsi/gomega"
 	"github.com/spf13/cobra"
 	corev1 "k8s.io/api/core/v1"
@@ -569,4 +570,47 @@ var _ = Describe("SSH Options", func() {
 
 		Expect(o.Validate()).NotTo(Succeed())
 	})
+
+	DescribeTable("Prompt should print question and should return...", func(defaultAnswer bool, answer string, expectedResult bool) {
+		question := "Is 42 the ultimate answer?"
+		expectedPrompt := question
+		if defaultAnswer {
+			expectedPrompt += " [n/Y]: "
+		} else {
+			expectedPrompt += " [y/N]: "
+		}
+		streams, stdin, stdout, _ := util.NewTestIOStreams()
+
+		stdin.Write([]byte(answer))
+		result := ssh.Confirm(streams, question, defaultAnswer)
+		stdoutStr := stdout.String()
+
+		Expect(stdoutStr).To(Equal(expectedPrompt))
+		Expect(result).To(Equal(expectedResult))
+	},
+		Entry("true  (defaultAnswer: false, given answer: y )", false, "y", true),
+		Entry("false (defaultAnswer: false, given answer: n )", false, "n", false),
+		Entry("false (defaultAnswer: false, given answer: \\n)", false, "\n", false),
+		Entry("true  (defaultAnswer: true , given answer: yEs )", true, "yEs", true),
+		Entry("false (defaultAnswer: true , given answer: nO )", true, "nO", false),
+		Entry("true  (defaultAnswer: true , given answer: \\n)", true, "\n", true),
+	)
+
+	DescribeTable("Should prompt for confirmation in case of /0 CIDRs without force-flag", func(cidr string, forceFlag, shouldConfirm bool) {
+		o := ssh.NewSSHOptions(streams)
+		o.CIDRs = []string{cidr}
+		o.SSHPublicKeyFile = publicSSHKeyFile
+		o.Force = forceFlag
+		confirmCalled := false
+		ssh.SetConfirm(func(ioStreams util.IOStreams, question string, defaultAnswer bool) bool {
+			confirmCalled = true
+			return true
+		})
+		o.Validate()
+		Expect(confirmCalled).To(Equal(shouldConfirm))
+	},
+		Entry("testing CIDR 8.8.8.8/0 without force flag", "8.8.8.8/0", false, true),
+		Entry("testing CIDR 8.8.8.8/16 without force flag", "8.8.8.8/16", false, false),
+		Entry("testing CIDR 8.8.8.8/0 with force flag", "8.8.8.8/0", true, false),
+	)
 })