feat: Add support of configuring host to use Satellite server

* Card ID: CCT-993
* Introduced new command "configure" and immediately added
  sub-command "satellite" to this command. "satellite" subcommand
  has --url CLI option and you can set hostname or URL of
  server Satellite server.
  * When valid URL or hostname is provided, then rhc tries to
    read /api/ping endpoint and it tries to verify that given
    server is Satellite server
  * When Satellite server is verified, then it tries to download
    bootstrap script from /pub/katello-rhsm-consumer
  * When script is downloaded, then this script is run as root
    user.
* Is little bit risky to run some script downloaded from web
  server. For this reason we will try to use different approach
  in the future. Satellite server will provide public REST API
  endpoints providing CA certs and rendered rhsm.conf. We will
  simply download these files and install them to system.
  Unfortunately, these REST API endpoints will be available
  in some future version of Satellite.
* Directory /var/lib/rhc is created during installation of RPM
  package

configure_cmd.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"fmt"
+	"github.com/briandowns/spinner"
+	"github.com/urfave/cli/v2"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+)
+
+// beforeSatelliteAction is run before satelliteAction is run. It is used
+// for checking CLI options.
+func beforeSatelliteAction(ctx *cli.Context) error {
+	// First check if machine-readable format is used
+	err := setupFormatOption(ctx)
+	if err != nil {
+		return err
+	}
+
+	satelliteUrlStr := ctx.String("url")
+	if satelliteUrlStr == "" {
+		return fmt.Errorf("no url provided using --url CLI option")
+	}
+
+	return checkForUnknownArgs(ctx)
+}
+
+// satelliteAction tries to get bootstrap script from Satellite server and run it.
+// When it is not possible to download the script or running script returns
+// non-zero exit code, then error is returned.
+//
+// It is really risky to download to run some script downloaded from the URL as a
+// root user without any restriction. For this reason, we at least check that
+// provided URL is URL of Satellite server.
+//
+// We would like to use different approach in the future. We would like to use
+// some API endpoints not restricted by username & password for getting CA certs
+// and rendered rhsm.conf, because it would be more secure, but it is not possible ATM
+func satelliteAction(ctx *cli.Context) error {
+	var configureSatelliteResult ConfigureSatelliteResult
+	configureSatelliteResult.format = ctx.String("format")
+	satelliteUrlStr := ctx.String("url")
+
+	uid := os.Getuid()
+	if uid != 0 {
+		errMsg := "non-root user cannot connect system"
+		exitCode := 1
+		return cli.Exit(fmt.Errorf("error: %satSpinner", errMsg), exitCode)
+	}
+
+	hostname, err := os.Hostname()
+	if uiSettings.isMachineReadable {
+		configureSatelliteResult.Hostname = hostname
+	}
+	if err != nil {
+		exitCode := 1
+		if uiSettings.isMachineReadable {
+			configureSatelliteResult.HostnameError = err.Error()
+			return cli.Exit(configureSatelliteResult, exitCode)
+		} else {
+			return cli.Exit(err, exitCode)
+		}
+	}
+
+	satelliteUrl, err := normalizeSatelliteScriptUrl(satelliteUrlStr)
+	if err != nil {
+		return cli.Exit(fmt.Errorf("could not parse satellite url: %w", err), 1)
+	}
+
+	configureSatelliteResult.SatelliteServerHostname = satelliteUrl.Hostname()
+	configureSatelliteResult.SatelliteServerScriptUrl = satelliteUrl.String()
+
+	var satSpinner *spinner.Spinner = nil
+	if uiSettings.isRich {
+		satSpinner = spinner.New(spinner.CharSets[9], 100*time.Millisecond)
+		satSpinner.Suffix = fmt.Sprintf(" Configuring '%v' to use Satellite %v", hostname, satelliteUrl.Host)
+		satSpinner.Start()
+		// Stop spinner after running function
+		defer func() { satSpinner.Stop() }()
+	}
+
+	err = pingSatelliteServer(satelliteUrl, satSpinner)
+	if err != nil {
+		return cli.Exit(fmt.Errorf("unable to verify that given server is Satellite server: %v", err), 1)
+	}
+
+	configureSatelliteResult.IsServerSatellite = true
+
+	// Create file for script file
+	satelliteScriptPath := filepath.Join(VarLibDir, "katello-rhsm-consumer")
+	defer os.Remove(satelliteScriptPath)
+	scriptFile, err := os.Create(satelliteScriptPath)
+	if err != nil {
+		return cli.Exit(fmt.Errorf("could not create %v file: %w", satelliteScriptPath, err), 1)
+	}
+	defer scriptFile.Close()
+	err = os.Chmod(satelliteScriptPath, 0700)
+	if err != nil {
+		return cli.Exit(fmt.Errorf("could not set permissions on %v file: %w", satelliteScriptPath, err), 1)
+	}
+
+	err = downloadSatelliteScript(scriptFile, satelliteUrl, satSpinner)
+	if err != nil {
+		return cli.Exit(fmt.Errorf("could not download satellite bootstrap script: %w", err), 1)
+	}
+
+	if satSpinner != nil {
+		satSpinner.Suffix = fmt.Sprintf(" Configuring '%v' to use Satellite server: %v", hostname, satelliteUrl.Host)
+	}
+	// Run the script. It should install CA certificate, change configuration of rhsm.conf.
+	// In theory, it can do almost anything.
+	cmd := exec.Command(satelliteScriptPath)
+	err = cmd.Run()
+	if err != nil {
+		return cli.Exit(fmt.Errorf("execution of %v script failed: %w", satelliteScriptPath, err), 1)
+	}
+
+	configureSatelliteResult.HostConfigured = true
+
+	if uiSettings.isRich {
+		satSpinner.Suffix = ""
+		satSpinner.Stop()
+	}
+
+	interactivePrintf("Host '%v' configured to use Satellite server: %v\n", hostname, satelliteUrl.Host)
+
+	return cli.Exit(configureSatelliteResult, 0)
+}

constants.go

@@ -39,6 +39,7 @@ var (
 	SysconfDir        string
 	LocalstateDir     string
 	DbusInterfacesDir string
+	VarLibDir         string
 )
 
 func init() {
@@ -75,6 +76,9 @@ func init() {
 	if DbusInterfacesDir == "" {
 		DbusInterfacesDir = filepath.Join(DataDir, "dbus-1", "interfaces")
 	}
+	if VarLibDir == "" {
+		VarLibDir = filepath.Join(LocalstateDir, "lib")
+	}
 
 	if ShortName == "" {
 		ShortName = "rhc"

main.go

@@ -174,6 +174,33 @@ func main() {
 			Before:      beforeConnectAction,
 			Action:      connectAction,
 		},
+		{
+			Name:      "configure",
+			Usage:     "Configure the host",
+			UsageText: fmt.Sprintf("%v configure [sub-command]", app.Name),
+			Subcommands: []*cli.Command{
+				{
+					Name:        "satellite",
+					Usage:       "Configure the host to use with Satellite server",
+					UsageText:   fmt.Sprintf("%v configure satellite [command options]", app.Name),
+					Description: "The satellite sub-command configure the system for connection to a Satellite server",
+					Flags: []cli.Flag{
+						&cli.StringFlag{
+							Name:    "url",
+							Usage:   "URL of the Satellite server",
+							Aliases: []string{"u"},
+						},
+						&cli.StringFlag{
+							Name:    "format",
+							Usage:   "prints output of satellite configure in machine-readable format (supported formats: \"json\")",
+							Aliases: []string{"f"},
+						},
+					},
+					Before: beforeSatelliteAction,
+					Action: satelliteAction,
+				},
+			},
+		},
 		{
 			Name: "disconnect",
 			Flags: []cli.Flag{

rhc.spec.in

@@ -78,6 +78,7 @@ make PREFIX=%{_prefix} \
      install
 install --directory %{buildroot}%{_unitdir}
 install --directory %{buildroot}%{_sysconfdir}/rhc
+mkdir -p %{buildroot}%{_sharedstatedir}/rhc
 ln -sf yggdrasil.service        %{buildroot}%{_unitdir}/rhcd.service
 ln -sf ../yggdrasil/config.toml %{buildroot}%{_sysconfdir}/rhc/config.toml
 
@@ -104,6 +105,7 @@ fi
 %{_mandir}/man1/*
 %{_unitdir}/*
 %{_presetdir}/*
+%dir %{_sharedstatedir}/rhc
 
 
 %files compat