source: code/trunk/service.go@ 751

package soju

import (
        "context"
        "crypto/sha1"
        "crypto/sha256"
        "crypto/sha512"
        "encoding/hex"
        "errors"
        "flag"
        "fmt"
        "io/ioutil"
        "sort"
        "strconv"
        "strings"
        "time"
        "unicode"

        "golang.org/x/crypto/bcrypt"
        "gopkg.in/irc.v3"
)

const serviceNick = "BouncerServ"
const serviceNickCM = "bouncerserv"
const serviceRealname = "soju bouncer service"

// maxRSABits is the maximum number of RSA key bits used when generating a new
// private key.
const maxRSABits = 8192

var servicePrefix = &irc.Prefix{
        Name: serviceNick,
        User: serviceNick,
        Host: serviceNick,
}

type serviceCommandSet map[string]*serviceCommand

type serviceCommand struct {
        usage    string
        desc     string
        handle   func(ctx context.Context, dc *downstreamConn, params []string) error
        children serviceCommandSet
        admin    bool
}

func sendServiceNOTICE(dc *downstreamConn, text string) {
        dc.SendMessage(&irc.Message{
                Prefix:  servicePrefix,
                Command: "NOTICE",
                Params:  []string{dc.nick, text},
        })
}

func sendServicePRIVMSG(dc *downstreamConn, text string) {
        dc.SendMessage(&irc.Message{
                Prefix:  servicePrefix,
                Command: "PRIVMSG",
                Params:  []string{dc.nick, text},
        })
}

func splitWords(s string) ([]string, error) {
        var words []string
        var lastWord strings.Builder
        escape := false
        prev := ' '
        wordDelim := ' '

        for _, r := range s {
                if escape {
                        // last char was a backslash, write the byte as-is.
                        lastWord.WriteRune(r)
                        escape = false
                } else if r == '\\' {
                        escape = true
                } else if wordDelim == ' ' && unicode.IsSpace(r) {
                        // end of last word
                        if !unicode.IsSpace(prev) {
                                words = append(words, lastWord.String())
                                lastWord.Reset()
                        }
                } else if r == wordDelim {
                        // wordDelim is either " or ', switch back to
                        // space-delimited words.
                        wordDelim = ' '
                } else if r == '"' || r == '\'' {
                        if wordDelim == ' ' {
                                // start of (double-)quoted word
                                wordDelim = r
                        } else {
                                // either wordDelim is " and r is ' or vice-versa
                                lastWord.WriteRune(r)
                        }
                } else {
                        lastWord.WriteRune(r)
                }

                prev = r
        }

        if !unicode.IsSpace(prev) {
                words = append(words, lastWord.String())
        }

        if wordDelim != ' ' {
                return nil, fmt.Errorf("unterminated quoted string")
        }
        if escape {
                return nil, fmt.Errorf("unterminated backslash sequence")
        }

        return words, nil
}

func handleServicePRIVMSG(ctx context.Context, dc *downstreamConn, text string) {
        words, err := splitWords(text)
        if err != nil {
                sendServicePRIVMSG(dc, fmt.Sprintf(`error: failed to parse command: %v`, err))
                return
        }

        cmd, params, err := serviceCommands.Get(words)
        if err != nil {
                sendServicePRIVMSG(dc, fmt.Sprintf(`error: %v (type "help" for a list of commands)`, err))
                return
        }
        if cmd.admin && !dc.user.Admin {
                sendServicePRIVMSG(dc, "error: you must be an admin to use this command")
                return
        }

        if cmd.handle == nil {
                if len(cmd.children) > 0 {
                        var l []string
                        appendServiceCommandSetHelp(cmd.children, words, dc.user.Admin, &l)
                        sendServicePRIVMSG(dc, "available commands: "+strings.Join(l, ", "))
                } else {
                        // Pretend the command does not exist if it has neither children nor handler.
                        // This is obviously a bug but it is better to not die anyway.
                        dc.logger.Printf("command without handler and subcommands invoked:", words[0])
                        sendServicePRIVMSG(dc, fmt.Sprintf("command %q not found", words[0]))
                }
                return
        }

        if err := cmd.handle(ctx, dc, params); err != nil {
                sendServicePRIVMSG(dc, fmt.Sprintf("error: %v", err))
        }
}

func (cmds serviceCommandSet) Get(params []string) (*serviceCommand, []string, error) {
        if len(params) == 0 {
                return nil, nil, fmt.Errorf("no command specified")
        }

        name := params[0]
        params = params[1:]

        cmd, ok := cmds[name]
        if !ok {
                for k := range cmds {
                        if !strings.HasPrefix(k, name) {
                                continue
                        }
                        if cmd != nil {
                                return nil, params, fmt.Errorf("command %q is ambiguous", name)
                        }
                        cmd = cmds[k]
                }
        }
        if cmd == nil {
                return nil, params, fmt.Errorf("command %q not found", name)
        }

        if len(params) == 0 || len(cmd.children) == 0 {
                return cmd, params, nil
        }
        return cmd.children.Get(params)
}

func (cmds serviceCommandSet) Names() []string {
        l := make([]string, 0, len(cmds))
        for name := range cmds {
                l = append(l, name)
        }
        sort.Strings(l)
        return l
}

var serviceCommands serviceCommandSet

func init() {
        serviceCommands = serviceCommandSet{
                "help": {
                        usage:  "[command]",
                        desc:   "print help message",
                        handle: handleServiceHelp,
                },
                "network": {
                        children: serviceCommandSet{
                                "create": {
                                        usage:  "-addr <addr> [-name name] [-username username] [-pass pass] [-realname realname] [-nick nick] [-enabled enabled] [-connect-command command]...",
                                        desc:   "add a new network",
                                        handle: handleServiceNetworkCreate,
                                },
                                "status": {
                                        desc:   "show a list of saved networks and their current status",
                                        handle: handleServiceNetworkStatus,
                                },
                                "update": {
                                        usage:  "<name> [-addr addr] [-name name] [-username username] [-pass pass] [-realname realname] [-nick nick] [-enabled enabled] [-connect-command command]...",
                                        desc:   "update a network",
                                        handle: handleServiceNetworkUpdate,
                                },
                                "delete": {
                                        usage:  "<name>",
                                        desc:   "delete a network",
                                        handle: handleServiceNetworkDelete,
                                },
                                "quote": {
                                        usage:  "<name> <command>",
                                        desc:   "send a raw line to a network",
                                        handle: handleServiceNetworkQuote,
                                },
                        },
                },
                "certfp": {
                        children: serviceCommandSet{
                                "generate": {
                                        usage:  "[-key-type rsa|ecdsa|ed25519] [-bits N] <network name>",
                                        desc:   "generate a new self-signed certificate, defaults to using RSA-3072 key",
                                        handle: handleServiceCertFPGenerate,
                                },
                                "fingerprint": {
                                        usage:  "<network name>",
                                        desc:   "show fingerprints of certificate associated with the network",
                                        handle: handleServiceCertFPFingerprints,
                                },
                        },
                },
                "sasl": {
                        children: serviceCommandSet{
                                "status": {
                                        usage:  "<network name>",
                                        desc:   "show SASL status",
                                        handle: handleServiceSaslStatus,
                                },
                                "set-plain": {
                                        usage:  "<network name> <username> <password>",
                                        desc:   "set SASL PLAIN credentials",
                                        handle: handleServiceSASLSetPlain,
                                },
                                "reset": {
                                        usage:  "<network name>",
                                        desc:   "disable SASL authentication and remove stored credentials",
                                        handle: handleServiceSASLReset,
                                },
                        },
                },
                "user": {
                        children: serviceCommandSet{
                                "create": {
                                        usage:  "-username <username> -password <password> [-realname <realname>] [-admin]",
                                        desc:   "create a new soju user",
                                        handle: handleUserCreate,
                                        admin:  true,
                                },
                                "update": {
                                        usage:  "[-password <password>] [-realname <realname>]",
                                        desc:   "update the current user",
                                        handle: handleUserUpdate,
                                },
                                "delete": {
                                        usage:  "<username>",
                                        desc:   "delete a user",
                                        handle: handleUserDelete,
                                        admin:  true,
                                },
                        },
                },
                "channel": {
                        children: serviceCommandSet{
                                "status": {
                                        usage:  "[-network name]",
                                        desc:   "show a list of saved channels and their current status",
                                        handle: handleServiceChannelStatus,
                                },
                                "update": {
                                        usage:  "<name> [-relay-detached <default|none|highlight|message>] [-reattach-on <default|none|highlight|message>] [-detach-after <duration>] [-detach-on <default|none|highlight|message>]",
                                        desc:   "update a channel",
                                        handle: handleServiceChannelUpdate,
                                },
                        },
                },
                "server": {
                        children: serviceCommandSet{
                                "status": {
                                        desc:   "show server statistics",
                                        handle: handleServiceServerStatus,
                                        admin:  true,
                                },
                                "notice": {
                                        desc:   "broadcast a notice to all connected bouncer users",
                                        handle: handleServiceServerNotice,
                                        admin:  true,
                                },
                        },
                        admin: true,
                },
        }
}

func appendServiceCommandSetHelp(cmds serviceCommandSet, prefix []string, admin bool, l *[]string) {
        for _, name := range cmds.Names() {
                cmd := cmds[name]
                if cmd.admin && !admin {
                        continue
                }
                words := append(prefix, name)
                if len(cmd.children) == 0 {
                        s := strings.Join(words, " ")
                        *l = append(*l, s)
                } else {
                        appendServiceCommandSetHelp(cmd.children, words, admin, l)
                }
        }
}

func handleServiceHelp(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) > 0 {
                cmd, rest, err := serviceCommands.Get(params)
                if err != nil {
                        return err
                }
                words := params[:len(params)-len(rest)]

                if len(cmd.children) > 0 {
                        var l []string
                        appendServiceCommandSetHelp(cmd.children, words, dc.user.Admin, &l)
                        sendServicePRIVMSG(dc, "available commands: "+strings.Join(l, ", "))
                } else {
                        text := strings.Join(words, " ")
                        if cmd.usage != "" {
                                text += " " + cmd.usage
                        }
                        text += ": " + cmd.desc

                        sendServicePRIVMSG(dc, text)
                }
        } else {
                var l []string
                appendServiceCommandSetHelp(serviceCommands, nil, dc.user.Admin, &l)
                sendServicePRIVMSG(dc, "available commands: "+strings.Join(l, ", "))
        }
        return nil
}

func newFlagSet() *flag.FlagSet {
        fs := flag.NewFlagSet("", flag.ContinueOnError)
        fs.SetOutput(ioutil.Discard)
        return fs
}

type stringSliceFlag []string

func (v *stringSliceFlag) String() string {
        return fmt.Sprint([]string(*v))
}

func (v *stringSliceFlag) Set(s string) error {
        *v = append(*v, s)
        return nil
}

// stringPtrFlag is a flag value populating a string pointer. This allows to
// disambiguate between a flag that hasn't been set and a flag that has been
// set to an empty string.
type stringPtrFlag struct {
        ptr **string
}

func (f stringPtrFlag) String() string {
        if f.ptr == nil || *f.ptr == nil {
                return ""
        }
        return **f.ptr
}

func (f stringPtrFlag) Set(s string) error {
        *f.ptr = &s
        return nil
}

type boolPtrFlag struct {
        ptr **bool
}

func (f boolPtrFlag) String() string {
        if f.ptr == nil || *f.ptr == nil {
                return "<nil>"
        }
        return strconv.FormatBool(**f.ptr)
}

func (f boolPtrFlag) Set(s string) error {
        v, err := strconv.ParseBool(s)
        if err != nil {
                return err
        }
        *f.ptr = &v
        return nil
}

type networkFlagSet struct {
        *flag.FlagSet
        Addr, Name, Nick, Username, Pass, Realname *string
        Enabled                                    *bool
        ConnectCommands                            []string
}

func newNetworkFlagSet() *networkFlagSet {
        fs := &networkFlagSet{FlagSet: newFlagSet()}
        fs.Var(stringPtrFlag{&fs.Addr}, "addr", "")
        fs.Var(stringPtrFlag{&fs.Name}, "name", "")
        fs.Var(stringPtrFlag{&fs.Nick}, "nick", "")
        fs.Var(stringPtrFlag{&fs.Username}, "username", "")
        fs.Var(stringPtrFlag{&fs.Pass}, "pass", "")
        fs.Var(stringPtrFlag{&fs.Realname}, "realname", "")
        fs.Var(boolPtrFlag{&fs.Enabled}, "enabled", "")
        fs.Var((*stringSliceFlag)(&fs.ConnectCommands), "connect-command", "")
        return fs
}

func (fs *networkFlagSet) update(network *Network) error {
        if fs.Addr != nil {
                if addrParts := strings.SplitN(*fs.Addr, "://", 2); len(addrParts) == 2 {
                        scheme := addrParts[0]
                        switch scheme {
                        case "ircs", "irc+insecure", "unix":
                        default:
                                return fmt.Errorf("unknown scheme %q (supported schemes: ircs, irc+insecure, unix)", scheme)
                        }
                }
                network.Addr = *fs.Addr
        }
        if fs.Name != nil {
                network.Name = *fs.Name
        }
        if fs.Nick != nil {
                network.Nick = *fs.Nick
        }
        if fs.Username != nil {
                network.Username = *fs.Username
        }
        if fs.Pass != nil {
                network.Pass = *fs.Pass
        }
        if fs.Realname != nil {
                network.Realname = *fs.Realname
        }
        if fs.Enabled != nil {
                network.Enabled = *fs.Enabled
        }
        if fs.ConnectCommands != nil {
                if len(fs.ConnectCommands) == 1 && fs.ConnectCommands[0] == "" {
                        network.ConnectCommands = nil
                } else {
                        for _, command := range fs.ConnectCommands {
                                _, err := irc.ParseMessage(command)
                                if err != nil {
                                        return fmt.Errorf("flag -connect-command must be a valid raw irc command string: %q: %v", command, err)
                                }
                        }
                        network.ConnectCommands = fs.ConnectCommands
                }
        }
        return nil
}

func handleServiceNetworkCreate(ctx context.Context, dc *downstreamConn, params []string) error {
        fs := newNetworkFlagSet()
        if err := fs.Parse(params); err != nil {
                return err
        }
        if fs.Addr == nil {
                return fmt.Errorf("flag -addr is required")
        }

        record := &Network{
                Addr:    *fs.Addr,
                Enabled: true,
        }
        if err := fs.update(record); err != nil {
                return err
        }

        network, err := dc.user.createNetwork(ctx, record)
        if err != nil {
                return fmt.Errorf("could not create network: %v", err)
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("created network %q", network.GetName()))
        return nil
}

func handleServiceNetworkStatus(ctx context.Context, dc *downstreamConn, params []string) error {
        n := 0
        dc.user.forEachNetwork(func(net *network) {
                var statuses []string
                var details string
                if uc := net.conn; uc != nil {
                        if dc.nick != uc.nick {
                                statuses = append(statuses, "connected as "+uc.nick)
                        } else {
                                statuses = append(statuses, "connected")
                        }
                        details = fmt.Sprintf("%v channels", uc.channels.Len())
                } else if !net.Enabled {
                        statuses = append(statuses, "disabled")
                } else {
                        statuses = append(statuses, "disconnected")
                        if net.lastError != nil {
                                details = net.lastError.Error()
                        }
                }

                if net == dc.network {
                        statuses = append(statuses, "current")
                }

                name := net.GetName()
                if name != net.Addr {
                        name = fmt.Sprintf("%v (%v)", name, net.Addr)
                }

                s := fmt.Sprintf("%v [%v]", name, strings.Join(statuses, ", "))
                if details != "" {
                        s += ": " + details
                }
                sendServicePRIVMSG(dc, s)

                n++
        })

        if n == 0 {
                sendServicePRIVMSG(dc, `No network configured, add one with "network create".`)
        }

        return nil
}

func handleServiceNetworkUpdate(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) < 1 {
                return fmt.Errorf("expected at least one argument")
        }

        fs := newNetworkFlagSet()
        if err := fs.Parse(params[1:]); err != nil {
                return err
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        record := net.Network // copy network record because we'll mutate it
        if err := fs.update(&record); err != nil {
                return err
        }

        network, err := dc.user.updateNetwork(ctx, &record)
        if err != nil {
                return fmt.Errorf("could not update network: %v", err)
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("updated network %q", network.GetName()))
        return nil
}

func handleServiceNetworkDelete(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        if err := dc.user.deleteNetwork(ctx, net.ID); err != nil {
                return err
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("deleted network %q", net.GetName()))
        return nil
}

func handleServiceNetworkQuote(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 2 {
                return fmt.Errorf("expected exactly two arguments")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        uc := net.conn
        if uc == nil {
                return fmt.Errorf("network %q is not currently connected", params[0])
        }

        m, err := irc.ParseMessage(params[1])
        if err != nil {
                return fmt.Errorf("failed to parse command %q: %v", params[1], err)
        }
        uc.SendMessage(m)

        sendServicePRIVMSG(dc, fmt.Sprintf("sent command to %q", net.GetName()))
        return nil
}

func sendCertfpFingerprints(dc *downstreamConn, cert []byte) {
        sha1Sum := sha1.Sum(cert)
        sendServicePRIVMSG(dc, "SHA-1 fingerprint: "+hex.EncodeToString(sha1Sum[:]))
        sha256Sum := sha256.Sum256(cert)
        sendServicePRIVMSG(dc, "SHA-256 fingerprint: "+hex.EncodeToString(sha256Sum[:]))
        sha512Sum := sha512.Sum512(cert)
        sendServicePRIVMSG(dc, "SHA-512 fingerprint: "+hex.EncodeToString(sha512Sum[:]))
}

func handleServiceCertFPGenerate(ctx context.Context, dc *downstreamConn, params []string) error {
        fs := newFlagSet()
        keyType := fs.String("key-type", "rsa", "key type to generate (rsa, ecdsa, ed25519)")
        bits := fs.Int("bits", 3072, "size of key to generate, meaningful only for RSA")

        if err := fs.Parse(params); err != nil {
                return err
        }

        if len(fs.Args()) != 1 {
                return errors.New("exactly one argument is required")
        }

        net := dc.user.getNetwork(fs.Arg(0))
        if net == nil {
                return fmt.Errorf("unknown network %q", fs.Arg(0))
        }

        if *bits <= 0 || *bits > maxRSABits {
                return fmt.Errorf("invalid value for -bits")
        }

        privKey, cert, err := generateCertFP(*keyType, *bits)
        if err != nil {
                return err
        }

        net.SASL.External.CertBlob = cert
        net.SASL.External.PrivKeyBlob = privKey
        net.SASL.Mechanism = "EXTERNAL"

        if err := dc.srv.db.StoreNetwork(ctx, dc.user.ID, &net.Network); err != nil {
                return err
        }

        sendServicePRIVMSG(dc, "certificate generated")
        sendCertfpFingerprints(dc, cert)
        return nil
}

func handleServiceCertFPFingerprints(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        if net.SASL.Mechanism != "EXTERNAL" {
                return fmt.Errorf("CertFP not set up")
        }

        sendCertfpFingerprints(dc, net.SASL.External.CertBlob)
        return nil
}

func handleServiceSaslStatus(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        switch net.SASL.Mechanism {
        case "PLAIN":
                sendServicePRIVMSG(dc, fmt.Sprintf("SASL PLAIN enabled with username %q", net.SASL.Plain.Username))
        case "EXTERNAL":
                sendServicePRIVMSG(dc, "SASL EXTERNAL (CertFP) enabled")
        case "":
                sendServicePRIVMSG(dc, "SASL is disabled")
        }

        if uc := net.conn; uc != nil {
                if uc.account != "" {
                        sendServicePRIVMSG(dc, fmt.Sprintf("Authenticated on upstream network with account %q", uc.account))
                } else {
                        sendServicePRIVMSG(dc, "Unauthenticated on upstream network")
                }
        } else {
                sendServicePRIVMSG(dc, "Disconnected from upstream network")
        }

        return nil
}

func handleServiceSASLSetPlain(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 3 {
                return fmt.Errorf("expected exactly 3 arguments")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        net.SASL.Plain.Username = params[1]
        net.SASL.Plain.Password = params[2]
        net.SASL.Mechanism = "PLAIN"

        if err := dc.srv.db.StoreNetwork(ctx, dc.user.ID, &net.Network); err != nil {
                return err
        }

        sendServicePRIVMSG(dc, "credentials saved")
        return nil
}

func handleServiceSASLReset(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }

        net := dc.user.getNetwork(params[0])
        if net == nil {
                return fmt.Errorf("unknown network %q", params[0])
        }

        net.SASL.Plain.Username = ""
        net.SASL.Plain.Password = ""
        net.SASL.External.CertBlob = nil
        net.SASL.External.PrivKeyBlob = nil
        net.SASL.Mechanism = ""

        if err := dc.srv.db.StoreNetwork(ctx, dc.user.ID, &net.Network); err != nil {
                return err
        }

        sendServicePRIVMSG(dc, "credentials reset")
        return nil
}

func handleUserCreate(ctx context.Context, dc *downstreamConn, params []string) error {
        fs := newFlagSet()
        username := fs.String("username", "", "")
        password := fs.String("password", "", "")
        realname := fs.String("realname", "", "")
        admin := fs.Bool("admin", false, "")

        if err := fs.Parse(params); err != nil {
                return err
        }
        if *username == "" {
                return fmt.Errorf("flag -username is required")
        }
        if *password == "" {
                return fmt.Errorf("flag -password is required")
        }

        hashed, err := bcrypt.GenerateFromPassword([]byte(*password), bcrypt.DefaultCost)
        if err != nil {
                return fmt.Errorf("failed to hash password: %v", err)
        }

        user := &User{
                Username: *username,
                Password: string(hashed),
                Realname: *realname,
                Admin:    *admin,
        }
        if _, err := dc.srv.createUser(ctx, user); err != nil {
                return fmt.Errorf("could not create user: %v", err)
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("created user %q", *username))
        return nil
}

func popArg(params []string) (string, []string) {
        if len(params) > 0 && !strings.HasPrefix(params[0], "-") {
                return params[0], params[1:]
        }
        return "", params
}

func handleUserUpdate(ctx context.Context, dc *downstreamConn, params []string) error {
        var password, realname *string
        var admin *bool
        fs := newFlagSet()
        fs.Var(stringPtrFlag{&password}, "password", "")
        fs.Var(stringPtrFlag{&realname}, "realname", "")
        fs.Var(boolPtrFlag{&admin}, "admin", "")

        username, params := popArg(params)
        if err := fs.Parse(params); err != nil {
                return err
        }
        if len(fs.Args()) > 0 {
                return fmt.Errorf("unexpected argument")
        }

        var hashed *string
        if password != nil {
                hashedBytes, err := bcrypt.GenerateFromPassword([]byte(*password), bcrypt.DefaultCost)
                if err != nil {
                        return fmt.Errorf("failed to hash password: %v", err)
                }
                hashedStr := string(hashedBytes)
                hashed = &hashedStr
        }

        if username != "" && username != dc.user.Username {
                if !dc.user.Admin {
                        return fmt.Errorf("you must be an admin to update other users")
                }
                if realname != nil {
                        return fmt.Errorf("cannot update -realname of other user")
                }

                u := dc.srv.getUser(username)
                if u == nil {
                        return fmt.Errorf("unknown username %q", username)
                }

                done := make(chan error, 1)
                event := eventUserUpdate{
                        password: hashed,
                        admin:    admin,
                        done:     done,
                }
                select {
                case <-ctx.Done():
                        return ctx.Err()
                case u.events <- event:
                }
                // TODO: send context to the other side
                if err := <-done; err != nil {
                        return err
                }

                sendServicePRIVMSG(dc, fmt.Sprintf("updated user %q", username))
        } else {
                // copy the user record because we'll mutate it
                record := dc.user.User

                if hashed != nil {
                        record.Password = *hashed
                }
                if realname != nil {
                        record.Realname = *realname
                }
                if admin != nil {
                        return fmt.Errorf("cannot update -admin of own user")
                }

                if err := dc.user.updateUser(ctx, &record); err != nil {
                        return err
                }

                sendServicePRIVMSG(dc, fmt.Sprintf("updated user %q", dc.user.Username))
        }

        return nil
}

func handleUserDelete(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }
        username := params[0]

        u := dc.srv.getUser(username)
        if u == nil {
                return fmt.Errorf("unknown username %q", username)
        }

        u.stop()

        if err := dc.srv.db.DeleteUser(ctx, u.ID); err != nil {
                return fmt.Errorf("failed to delete user: %v", err)
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("deleted user %q", username))
        return nil
}

func handleServiceChannelStatus(ctx context.Context, dc *downstreamConn, params []string) error {
        var defaultNetworkName string
        if dc.network != nil {
                defaultNetworkName = dc.network.GetName()
        }

        fs := newFlagSet()
        networkName := fs.String("network", defaultNetworkName, "")

        if err := fs.Parse(params); err != nil {
                return err
        }

        n := 0

        sendNetwork := func(net *network) {
                var channels []*Channel
                for _, entry := range net.channels.innerMap {
                        channels = append(channels, entry.value.(*Channel))
                }

                sort.Slice(channels, func(i, j int) bool {
                        return strings.ReplaceAll(channels[i].Name, "#", "") <
                                strings.ReplaceAll(channels[j].Name, "#", "")
                })

                for _, ch := range channels {
                        var uch *upstreamChannel
                        if net.conn != nil {
                                uch = net.conn.channels.Value(ch.Name)
                        }

                        name := ch.Name
                        if *networkName == "" {
                                name += "/" + net.GetName()
                        }

                        var status string
                        if uch != nil {
                                status = "joined"
                        } else if net.conn != nil {
                                status = "parted"
                        } else {
                                status = "disconnected"
                        }

                        if ch.Detached {
                                status += ", detached"
                        }

                        s := fmt.Sprintf("%v [%v]", name, status)
                        sendServicePRIVMSG(dc, s)

                        n++
                }
        }

        if *networkName == "" {
                dc.user.forEachNetwork(sendNetwork)
        } else {
                net := dc.user.getNetwork(*networkName)
                if net == nil {
                        return fmt.Errorf("unknown network %q", *networkName)
                }
                sendNetwork(net)
        }

        if n == 0 {
                sendServicePRIVMSG(dc, "No channel configured.")
        }

        return nil
}

type channelFlagSet struct {
        *flag.FlagSet
        RelayDetached, ReattachOn, DetachAfter, DetachOn *string
}

func newChannelFlagSet() *channelFlagSet {
        fs := &channelFlagSet{FlagSet: newFlagSet()}
        fs.Var(stringPtrFlag{&fs.RelayDetached}, "relay-detached", "")
        fs.Var(stringPtrFlag{&fs.ReattachOn}, "reattach-on", "")
        fs.Var(stringPtrFlag{&fs.DetachAfter}, "detach-after", "")
        fs.Var(stringPtrFlag{&fs.DetachOn}, "detach-on", "")
        return fs
}

func (fs *channelFlagSet) update(channel *Channel) error {
        if fs.RelayDetached != nil {
                filter, err := parseFilter(*fs.RelayDetached)
                if err != nil {
                        return err
                }
                channel.RelayDetached = filter
        }
        if fs.ReattachOn != nil {
                filter, err := parseFilter(*fs.ReattachOn)
                if err != nil {
                        return err
                }
                channel.ReattachOn = filter
        }
        if fs.DetachAfter != nil {
                dur, err := time.ParseDuration(*fs.DetachAfter)
                if err != nil || dur < 0 {
                        return fmt.Errorf("unknown duration for -detach-after %q (duration format: 0, 300s, 22h30m, ...)", *fs.DetachAfter)
                }
                channel.DetachAfter = dur
        }
        if fs.DetachOn != nil {
                filter, err := parseFilter(*fs.DetachOn)
                if err != nil {
                        return err
                }
                channel.DetachOn = filter
        }
        return nil
}

func handleServiceChannelUpdate(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) < 1 {
                return fmt.Errorf("expected at least one argument")
        }
        name := params[0]

        fs := newChannelFlagSet()
        if err := fs.Parse(params[1:]); err != nil {
                return err
        }

        uc, upstreamName, err := dc.unmarshalEntity(name)
        if err != nil {
                return fmt.Errorf("unknown channel %q", name)
        }

        ch := uc.network.channels.Value(upstreamName)
        if ch == nil {
                return fmt.Errorf("unknown channel %q", name)
        }

        if err := fs.update(ch); err != nil {
                return err
        }

        uc.updateChannelAutoDetach(upstreamName)

        if err := dc.srv.db.StoreChannel(ctx, uc.network.ID, ch); err != nil {
                return fmt.Errorf("failed to update channel: %v", err)
        }

        sendServicePRIVMSG(dc, fmt.Sprintf("updated channel %q", name))
        return nil
}

func handleServiceServerStatus(ctx context.Context, dc *downstreamConn, params []string) error {
        dbStats, err := dc.user.srv.db.Stats(ctx)
        if err != nil {
                return err
        }
        serverStats := dc.user.srv.Stats()
        sendServicePRIVMSG(dc, fmt.Sprintf("%v/%v users, %v downstreams, %v upstreams, %v networks, %v channels", serverStats.Users, dbStats.Users, serverStats.Downstreams, serverStats.Upstreams, dbStats.Networks, dbStats.Channels))
        return nil
}

func handleServiceServerNotice(ctx context.Context, dc *downstreamConn, params []string) error {
        if len(params) != 1 {
                return fmt.Errorf("expected exactly one argument")
        }
        text := params[0]

        dc.logger.Printf("broadcasting bouncer-wide NOTICE: %v", text)

        broadcastMsg := &irc.Message{
                Prefix:  servicePrefix,
                Command: "NOTICE",
                Params:  []string{"$" + dc.srv.Config().Hostname, text},
        }
        var err error
        dc.srv.forEachUser(func(u *user) {
                select {
                case <-ctx.Done():
                        err = ctx.Err()
                case u.events <- eventBroadcast{broadcastMsg}:
                }
        })
        return err
}