Add 'user kick' and 'user ban' commands

The former allows to terminate all active user sessions (poll-based,
every 30s)

The latter does the same but also removes all user keys, making him
unable to login again

pkg/bastion/shell.go

@@ -1611,6 +1611,59 @@ GLOBAL OPTIONS:
 						enc.SetIndent("", "  ")
 						return enc.Encode(users)
 					},
+				}, {
+					Name:      "kick",
+					Usage:     "Kills all active sessions for user(s)",
+					ArgsUsage: "USER...",
+					Action: func(c *cli.Context) error {
+						if c.NArg() < 1 {
+							return cli.ShowSubcommandHelp(c)
+						}
+
+						if err := myself.CheckRoles([]string{"admin"}); err != nil {
+							return err
+						}
+
+						var users []*dbmodels.User
+						if err := dbmodels.UsersByIdentifiers(db, c.Args()).Find(&users).Error; err != nil {
+							return err
+						}
+
+						for _, user := range users {
+							if err := db.Model(&dbmodels.Session{}).Where(&dbmodels.Session{User: user, Status: string(dbmodels.SessionStatusActive)}).Update("status", "closed").Error; err != nil {
+								return err
+							}
+						}
+						return nil
+					},
+				}, {
+					Name:      "ban",
+					Usage:     "Kills all active sessions for user(s), and wipes all his ssh keys",
+					ArgsUsage: "USER...",
+					Action: func(c *cli.Context) error {
+						if c.NArg() < 1 {
+							return cli.ShowSubcommandHelp(c)
+						}
+
+						if err := myself.CheckRoles([]string{"admin"}); err != nil {
+							return err
+						}
+
+						var users []*dbmodels.User
+						if err := dbmodels.UsersByIdentifiers(db, c.Args()).Find(&users).Error; err != nil {
+							return err
+						}
+
+						for _, user := range users {
+							if err := db.Where("user_id = ?", user.ID).Delete(&dbmodels.UserKey{}).Error; err != nil {
+								return err
+							}
+							if err := db.Model(&dbmodels.Session{}).Where(&dbmodels.Session{User: user, Status: string(dbmodels.SessionStatusActive)}).Update("status", "closed").Error; err != nil {
+								return err
+							}
+						}
+						return nil
+					},
 				}, {
 					Name:        "invite",
 					ArgsUsage:   "<email>",

pkg/bastion/ssh.go

@@ -169,10 +169,21 @@ func ChannelHandler(srv *ssh.Server, conn *gossh.ServerConn, newChan gossh.NewCh
 				_ = ch.Close()
 				return
 			}
+			go func(cnx *gossh.ServerConn, dbConn *gorm.DB, sessionID uint) {
+				for {
+					sess := dbmodels.Session{Model: gorm.Model{ID: sessionID}, Status: string(dbmodels.SessionStatusActive)}
+					if err := dbConn.First(&sess).Error; err != nil || sess.Status != string(dbmodels.SessionStatusActive) {
+						log.Println("Session should be closed", sessionID, "closing connection")
+						conn.Close()
+						break
+					}
+					time.Sleep(30 * time.Second) // TODO: VDO: make configurable
+				}
+			}(conn, actx.db, sess.ID)
 			go func() {
 				err = multiChannelHandler(conn, newChan, ctx, sessionConfigs, sess.ID)
 				if err != nil {
-					log.Printf("Error: %v", err)
+					log.Printf("Error on session %v: %v", sess.ID, err)
 				}
 
 				now := time.Now()