Add initial implementation of step ssh logout.

command/ssh/logout.go

@@ -0,0 +1,103 @@
+package ssh
+
+import (
+	"github.com/pkg/errors"
+	"github.com/smallstep/cli/command"
+	"github.com/smallstep/cli/crypto/sshutil"
+	"github.com/smallstep/cli/errs"
+	"github.com/urfave/cli"
+)
+
+func logoutCommand() cli.Command {
+	return cli.Command{
+		Name:      "logout",
+		Action:    command.ActionFunc(logoutAction),
+		Usage:     "removes a private key from the ssh-agent and revoke",
+		UsageText: `**step ssh logout** <subject>`,
+		Description: `**step ssh logout** commands removes a key from the ssh-agent and optionally
+revokes the key creating a Key Revocation List file.
+
+## POSITIONAL ARGUMENTS
+
+<subject>
+:  The SSH subject or comment in the key.
+
+## EXAMPLES
+
+Remove the key mariano@work from the SSH agent:
+'''
+$ step ssh logout mariano@work
+'''
+
+Remove the key mariano@work from the agent listening in /tmp/ssh/agent:
+'''
+$ SSH_AUTH_SOCK=/tmp/ssh/agent step ssh logout mariano@work
+'''
+
+Remove all the keys stored in the SSH agent:
+'''
+$ step ssh logout --all
+'''
+
+Remove and revoke the key mariano@work:
+'''
+$ step ssh logout --revoke /etc/ssh/revoked_keys mariano@work
+'''`,
+		Flags: []cli.Flag{
+			cli.BoolFlag{
+				Name:  "all",
+				Usage: "Removes all the keys stored in the SSH agent.",
+			},
+			cli.StringFlag{
+				Name:  "revoke",
+				Usage: "Removes the key and updates a Key Revocation List <file> or KRL.",
+			},
+		},
+	}
+}
+
+func logoutAction(ctx *cli.Context) error {
+	if err := errs.NumberOfArguments(ctx, 1); err != nil {
+		return err
+	}
+
+	subject := ctx.Args().First()
+	// Flags
+	all := ctx.Bool("all")
+	revoke := ctx.String("revoke")
+
+	_, _ = subject, all
+
+	switch {
+	case revoke != "":
+		return errs.UnsupportedFlag(ctx, "revoke")
+	}
+
+	agent, err := sshutil.DialAgent()
+	if err != nil {
+		return err
+	}
+	defer agent.Close()
+
+	// Remove all
+	if all {
+		if err := agent.RemoveAll(); err != nil {
+			return errors.Wrap(err, "error removing all keys")
+		}
+	}
+
+	// Remove if comment == subject
+	keys, err := agent.List()
+	if err != nil {
+		return errors.Wrap(err, "error listing keys")
+	}
+	for _, key := range keys {
+		if key.Comment == subject {
+			if err := agent.Remove(key); err != nil {
+				return errors.Wrap(err, "error removing key")
+			}
+		}
+	}
+
+	return nil
+}