fix #858 and #383

conventional.yaml

@@ -259,6 +259,10 @@ server:
     secure-nets:
         # - "10.0.0.0/8"
 
+    # oragono will write files to disk under certain circumstances, e.g.,
+    # CPU profiling or data export. by default, these files will be written
+    # to the working directory. set this to customize:
+    # output-path: "/home/oragono/out"
 
 # account options
 accounts:
@@ -556,6 +560,7 @@ oper-classes:
             - "samode"
             - "vhosts"
             - "chanreg"
+            - "history"
 
 # ircd operators
 opers:
@@ -751,7 +756,8 @@ roleplay:
     # add the real nickname, in parentheses, to the end of every roleplay message?
     add-suffix: true
 
-# message history tracking, for the RESUME extension and possibly other uses in future
+# history message storage: this is used by CHATHISTORY, HISTORY, znc.in/playback,
+# various autoreplay features, and the resume extension
 history:
     # should we store messages for later playback?
     # by default, messages are stored in RAM only; they do not persist
@@ -820,3 +826,13 @@ history:
         # if you enable this, strict nickname reservation is strongly recommended
         # as well.
         direct-messages: "opt-out"
+
+    # options to control how messages are stored and deleted:
+    retention:
+        # allow users to delete their own messages from history?
+        allow-individual-delete: false
+
+        # if persistent history is enabled, create additional index tables,
+        # allowing deletion of JSON export of an account's messages. this
+        # may be needed for compliance with data privacy regulations.
+        enable-account-indexing: false

irc/accounts.go

@@ -1103,6 +1103,30 @@ func (am *AccountManager) LoadAccount(accountName string) (result ClientAccount,
 	return
 }
 
+// look up the unfolded version of an account name, possibly after deletion
+func (am *AccountManager) AccountToAccountName(account string) (result string) {
+	casefoldedAccount, err := CasefoldName(account)
+	if err != nil {
+		return
+	}
+
+	unregisteredKey := fmt.Sprintf(keyAccountUnregistered, casefoldedAccount)
+	accountNameKey := fmt.Sprintf(keyAccountName, casefoldedAccount)
+
+	am.server.store.View(func(tx *buntdb.Tx) error {
+		if name, err := tx.Get(accountNameKey); err == nil {
+			result = name
+			return nil
+		}
+		if name, err := tx.Get(unregisteredKey); err == nil {
+			result = name
+		}
+		return nil
+	})
+
+	return
+}
+
 func (am *AccountManager) deserializeRawAccount(raw rawClientAccount, cfName string) (result ClientAccount, err error) {
 	result.Name = raw.Name
 	result.NameCasefolded = cfName

irc/channel.go

@@ -20,10 +20,6 @@ import (
 	"github.com/oragono/oragono/irc/utils"
 )
 
-const (
-	histServMask = "HistServ!HistServ@localhost"
-)
-
 type ChannelSettings struct {
 	History HistoryStatus
 }
@@ -641,14 +637,14 @@ func channelHistoryStatus(config *Config, registered bool, storedStatus HistoryS
 	}
 }
 
-func (channel *Channel) AddHistoryItem(item history.Item) (err error) {
+func (channel *Channel) AddHistoryItem(item history.Item, account string) (err error) {
 	if !item.IsStorable() {
 		return
 	}
 
 	status, target := channel.historyStatus(channel.server.Config())
 	if status == HistoryPersistent {
-		err = channel.server.historyDB.AddChannelItem(target, item)
+		err = channel.server.historyDB.AddChannelItem(target, item, account)
 	} else if status == HistoryEphemeral {
 		channel.history.Add(item)
 	}
@@ -746,7 +742,7 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 			Message:     message,
 		}
 		histItem.Params[0] = details.realname
-		channel.AddHistoryItem(histItem)
+		channel.AddHistoryItem(histItem, details.account)
 	}
 
 	client.addChannel(channel, rb == nil)
@@ -902,7 +898,7 @@ func (channel *Channel) Part(client *Client, message string, rb *ResponseBuffer)
 		Nick:        details.nickMask,
 		AccountName: details.accountName,
 		Message:     splitMessage,
-	})
+	}, details.account)
 
 	client.server.logger.Debug("part", fmt.Sprintf("%s left channel %s", details.nick, chname))
 }
@@ -1165,7 +1161,7 @@ func (channel *Channel) SetTopic(client *Client, topic string, rb *ResponseBuffe
 		Nick:        details.nickMask,
 		AccountName: details.accountName,
 		Message:     message,
-	})
+	}, details.account)
 
 	channel.MarkDirty(IncludeTopic)
 }
@@ -1222,8 +1218,7 @@ func (channel *Channel) SendSplitMessage(command string, minPrefixMode modes.Mod
 		return
 	}
 
-	nickmask := client.NickMaskString()
-	account := client.AccountName()
+	details := client.Details()
 	chname := channel.Name()
 
 	// STATUSMSG targets are prefixed with the supplied min-prefix, e.g., @#channel
@@ -1238,9 +1233,9 @@ func (channel *Channel) SendSplitMessage(command string, minPrefixMode modes.Mod
 			tagsToUse = clientOnlyTags
 		}
 		if histType == history.Tagmsg && rb.session.capabilities.Has(caps.MessageTags) {
-			rb.AddFromClient(message.Time, message.Msgid, nickmask, account, tagsToUse, command, chname)
+			rb.AddFromClient(message.Time, message.Msgid, details.nickMask, details.accountName, tagsToUse, command, chname)
 		} else {
-			rb.AddSplitMessageFromClient(nickmask, account, tagsToUse, command, chname, message)
+			rb.AddSplitMessageFromClient(details.nickMask, details.accountName, tagsToUse, command, chname, message)
 		}
 	}
 	// send echo-message to other connected sessions
@@ -1253,9 +1248,9 @@ func (channel *Channel) SendSplitMessage(command string, minPrefixMode modes.Mod
 			tagsToUse = clientOnlyTags
 		}
 		if histType == history.Tagmsg && session.capabilities.Has(caps.MessageTags) {
-			session.sendFromClientInternal(false, message.Time, message.Msgid, nickmask, account, tagsToUse, command, chname)
+			session.sendFromClientInternal(false, message.Time, message.Msgid, details.nickMask, details.accountName, tagsToUse, command, chname)
 		} else if histType != history.Tagmsg {
-			session.sendSplitMsgFromClientInternal(false, nickmask, account, tagsToUse, command, chname, message)
+			session.sendSplitMsgFromClientInternal(false, details.nickMask, details.accountName, tagsToUse, command, chname, message)
 		}
 	}
 
@@ -1282,9 +1277,9 @@ func (channel *Channel) SendSplitMessage(command string, minPrefixMode modes.Mod
 			}
 
 			if histType == history.Tagmsg {
-				session.sendFromClientInternal(false, message.Time, message.Msgid, nickmask, account, tagsToUse, command, chname)
+				session.sendFromClientInternal(false, message.Time, message.Msgid, details.nickMask, details.accountName, tagsToUse, command, chname)
 			} else {
-				session.sendSplitMsgFromClientInternal(false, nickmask, account, tagsToUse, command, chname, message)
+				session.sendSplitMsgFromClientInternal(false, details.nickMask, details.accountName, tagsToUse, command, chname, message)
 			}
 		}
 	}
@@ -1294,10 +1289,10 @@ func (channel *Channel) SendSplitMessage(command string, minPrefixMode modes.Mod
 		channel.AddHistoryItem(history.Item{
 			Type:        histType,
 			Message:     message,
-			Nick:        nickmask,
-			AccountName: account,
+			Nick:        details.nickMask,
+			AccountName: details.accountName,
 			Tags:        clientOnlyTags,
-		})
+		}, details.account)
 	}
 }
 
@@ -1391,28 +1386,27 @@ func (channel *Channel) Kick(client *Client, target *Client, comment string, rb
 	}
 
 	message := utils.MakeMessage(comment)
-	clientMask := client.NickMaskString()
-	clientAccount := client.AccountName()
+	details := client.Details()
 
 	targetNick := target.Nick()
 	chname := channel.Name()
 	for _, member := range channel.Members() {
 		for _, session := range member.Sessions() {
 			if session != rb.session {
-				session.sendFromClientInternal(false, message.Time, message.Msgid, clientMask, clientAccount, nil, "KICK", chname, targetNick, comment)
+				session.sendFromClientInternal(false, message.Time, message.Msgid, details.nickMask, details.accountName, nil, "KICK", chname, targetNick, comment)
 			}
 		}
 	}
-	rb.Add(nil, clientMask, "KICK", chname, targetNick, comment)
+	rb.AddFromClient(message.Time, message.Msgid, details.nickMask, details.accountName, nil, "KICK", chname, targetNick, comment)
 
 	histItem := history.Item{
 		Type:        history.Kick,
-		Nick:        clientMask,
-		AccountName: target.AccountName(),
+		Nick:        details.nickMask,
+		AccountName: details.accountName,
 		Message:     message,
 	}
 	histItem.Params[0] = targetNick
-	channel.AddHistoryItem(histItem)
+	channel.AddHistoryItem(histItem, details.account)
 
 	channel.Quit(target)
 }

irc/chanserv.go

@@ -255,7 +255,7 @@ func csAmodeHandler(server *Server, client *Client, command string, params []str
 				if member.Account() == change.Arg {
 					applied, change := channel.applyModeToMember(client, change, rb)
 					if applied {
-						announceCmodeChanges(channel, modes.ModeChanges{change}, chanservMask, "*", rb)
+						announceCmodeChanges(channel, modes.ModeChanges{change}, chanservMask, "*", "", rb)
 					}
 				}
 			}
@@ -302,7 +302,7 @@ func csOpHandler(server *Server, client *Client, command string, params []string
 		},
 		rb)
 	if applied {
-		announceCmodeChanges(channelInfo, modes.ModeChanges{change}, chanservMask, "*", rb)
+		announceCmodeChanges(channelInfo, modes.ModeChanges{change}, chanservMask, "*", "", rb)
 	}
 
 	csNotice(rb, fmt.Sprintf(client.t("Successfully op'd in channel %s"), channelName))
@@ -354,7 +354,7 @@ func csRegisterHandler(server *Server, client *Client, command string, params []
 		},
 		rb)
 	if applied {
-		announceCmodeChanges(channelInfo, modes.ModeChanges{change}, chanservMask, "*", rb)
+		announceCmodeChanges(channelInfo, modes.ModeChanges{change}, chanservMask, "*", "", rb)
 	}
 }
 

irc/client.go

@@ -1277,7 +1277,7 @@ func (client *Client) destroy(session *Session) {
 	// use a defer here to avoid writing to mysql while holding the destroy semaphore:
 	defer func() {
 		for _, channel := range channels {
-			channel.AddHistoryItem(quitItem)
+			channel.AddHistoryItem(quitItem, details.account)
 		}
 	}()
 

irc/config.go

@@ -13,6 +13,7 @@ import (
 	"log"
 	"net"
 	"os"
+	"path/filepath"
 	"regexp"
 	"sort"
 	"strconv"
@@ -511,6 +512,7 @@ type Config struct {
 		supportedCaps *caps.Set
 		capValues     caps.Values
 		Casemapping   Casemapping
+		OutputPath    string `yaml:"output-path"`
 	}
 
 	Roleplay struct {
@@ -590,6 +592,10 @@ type Config struct {
 			RegisteredChannels   PersistentStatus `yaml:"registered-channels"`
 			DirectMessages       PersistentStatus `yaml:"direct-messages"`
 		}
+		Retention struct {
+			AllowIndividualDelete bool `yaml:"allow-individual-delete"`
+			EnableAccountIndexing bool `yaml:"enable-account-indexing"`
+		}
 	}
 
 	Filename string
@@ -1111,6 +1117,7 @@ func LoadConfig(filename string) (config *Config, err error) {
 	config.Roleplay.addSuffix = utils.BoolDefaultTrue(config.Roleplay.AddSuffix)
 
 	config.Datastore.MySQL.ExpireTime = time.Duration(config.History.Restrictions.ExpireTime)
+	config.Datastore.MySQL.TrackAccountMessages = config.History.Retention.EnableAccountIndexing
 
 	config.Server.Cloaks.Initialize()
 	if config.Server.Cloaks.Enabled {
@@ -1133,6 +1140,10 @@ func LoadConfig(filename string) (config *Config, err error) {
 	return config, nil
 }
 
+func (config *Config) getOutputPath(filename string) string {
+	return filepath.Join(config.Server.OutputPath, filename)
+}
+
 // setISupport sets up our RPL_ISUPPORT reply.
 func (config *Config) generateISupport() (err error) {
 	maxTargetsString := strconv.Itoa(maxTargets)

irc/handlers.go

@@ -677,7 +677,7 @@ func debugHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Res
 		rb.Notice(fmt.Sprintf("num goroutines: %d", count))
 
 	case "PROFILEHEAP":
-		profFile := "oragono.mprof"
+		profFile := server.Config().getOutputPath("oragono.mprof")
 		file, err := os.Create(profFile)
 		if err != nil {
 			rb.Notice(fmt.Sprintf("error: %s", err))
@@ -688,7 +688,7 @@ func debugHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Res
 		rb.Notice(fmt.Sprintf("written to %s", profFile))
 
 	case "STARTCPUPROFILE":
-		profFile := "oragono.prof"
+		profFile := server.Config().getOutputPath("oragono.prof")
 		file, err := os.Create(profFile)
 		if err != nil {
 			rb.Notice(fmt.Sprintf("error: %s", err))
@@ -935,50 +935,17 @@ func historyHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *R
 		return false
 	}
 
-	target := msg.Params[0]
-	if strings.ToLower(target) == "me" {
-		target = "*"
-	}
-	channel, sequence, err := server.GetHistorySequence(nil, client, target)
+	items, channel, err := easySelectHistory(server, client, msg.Params)
 
-	if sequence == nil || err != nil {
-		// whatever
-		rb.Add(nil, server.name, ERR_NOSUCHCHANNEL, client.Nick(), utils.SafeErrorParam(target), client.t("No such channel"))
+	if err == errNoSuchChannel {
+		rb.Add(nil, server.name, ERR_NOSUCHCHANNEL, client.Nick(), utils.SafeErrorParam(msg.Params[0]), client.t("No such channel"))
+		return false
+	} else if err != nil {
+		rb.Add(nil, server.name, ERR_UNKNOWNERROR, client.Nick(), msg.Command, client.t("Could not retrieve history"))
 		return false
 	}
 
-	var duration time.Duration
-	maxChathistoryLimit := config.History.ChathistoryMax
-	limit := 100
-	if maxChathistoryLimit < limit {
-		limit = maxChathistoryLimit
-	}
-	if len(msg.Params) > 1 {
-		providedLimit, err := strconv.Atoi(msg.Params[1])
-		if err == nil && providedLimit != 0 {
-			limit = providedLimit
-			if maxChathistoryLimit < limit {
-				limit = maxChathistoryLimit
-			}
-		} else if err != nil {
-			duration, err = time.ParseDuration(msg.Params[1])
-			if err == nil {
-				limit = maxChathistoryLimit
-			}
-		}
-	}
-
-	var items []history.Item
-	if duration == 0 {
-		items, _, err = sequence.Between(history.Selector{}, history.Selector{}, limit)
-	} else {
-		now := time.Now().UTC()
-		start := history.Selector{Time: now}
-		end := history.Selector{Time: now.Add(-duration)}
-		items, _, err = sequence.Between(start, end, limit)
-	}
-
-	if err == nil && len(items) != 0 {
+	if len(items) != 0 {
 		if channel != nil {
 			channel.replayHistoryItems(rb, items, false)
 		} else {
@@ -1530,12 +1497,12 @@ func cmodeHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Res
 	// process mode changes, include list operations (an empty set of changes does a list)
 	applied := channel.ApplyChannelModeChanges(client, msg.Command == "SAMODE", changes, rb)
 	details := client.Details()
-	announceCmodeChanges(channel, applied, details.nickMask, details.accountName, rb)
+	announceCmodeChanges(channel, applied, details.nickMask, details.accountName, details.account, rb)
 
 	return false
 }
 
-func announceCmodeChanges(channel *Channel, applied modes.ModeChanges, source, accountName string, rb *ResponseBuffer) {
+func announceCmodeChanges(channel *Channel, applied modes.ModeChanges, source, accountName, account string, rb *ResponseBuffer) {
 	// send out changes
 	if len(applied) > 0 {
 		message := utils.MakeMessage("")
@@ -1557,7 +1524,7 @@ func announceCmodeChanges(channel *Channel, applied modes.ModeChanges, source, a
 			Nick:        source,
 			AccountName: accountName,
 			Message:     message,
-		})
+		}, account)
 	}
 }
 

irc/history/history.go

@@ -284,6 +284,32 @@ func (list *Buffer) matchInternal(predicate Predicate, ascending bool, limit int
 	return
 }
 
+// Delete deletes messages matching some predicate.
+func (list *Buffer) Delete(predicate Predicate) (count int) {
+	list.Lock()
+	defer list.Unlock()
+
+	if list.start == -1 || len(list.buffer) == 0 {
+		return
+	}
+
+	pos := list.start
+	stop := list.prev(list.end)
+
+	for {
+		if predicate(&list.buffer[pos]) {
+			list.buffer[pos] = Item{}
+			count++
+		}
+		if pos == stop {
+			break
+		}
+		pos = list.next(pos)
+	}
+
+	return
+}
+
 // latest returns the items most recently added, up to `limit`. If `limit` is 0,
 // it returns all items.
 func (list *Buffer) latest(limit int) (results []Item) {

irc/histserv.go

@@ -0,0 +1,242 @@
+// Copyright (c) 2020 Shivaram Lingamneni <slingamn@cs.stanford.edu>
+// released under the MIT license
+
+package irc
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"runtime/debug"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/oragono/oragono/irc/history"
+)
+
+const (
+	histservHelp = `HistServ provides commands related to history.`
+	histServMask = "HistServ!HistServ@localhost"
+)
+
+func histservEnabled(config *Config) bool {
+	return config.History.Enabled
+}
+
+func historyComplianceEnabled(config *Config) bool {
+	return config.History.Enabled && config.History.Persistent.Enabled && config.History.Retention.EnableAccountIndexing
+}
+
+var (
+	histservCommands = map[string]*serviceCommand{
+		"forget": {
+			handler: histservForgetHandler,
+			help: `Syntax: $bFORGET <account>$b
+
+FORGET deletes all history messages sent by an account.`,
+			helpShort: `$bFORGET$b deletes all history messages sent by an account.`,
+			capabs:    []string{"history"},
+			enabled:   histservEnabled,
+			minParams: 1,
+			maxParams: 1,
+		},
+		"delete": {
+			handler: histservDeleteHandler,
+			help: `Syntax: $bDELETE [target] <msgid>$b
+
+DELETE deletes an individual message by its msgid. The target is a channel
+name or nickname; depending on the history implementation, this may or may not
+be necessary to locate the message.`,
+			helpShort: `$bDELETE$b deletes an individual message by its msgid.`,
+			enabled:   histservEnabled,
+			minParams: 1,
+			maxParams: 2,
+		},
+		"export": {
+			handler: histservExportHandler,
+			help: `Syntax: $bEXPORT <account>$b
+
+EXPORT exports all messages sent by an account as JSON. This can be used
+for regulatory compliance, e.g., article 15 of the GDPR.`,
+			helpShort: `$bEXPORT$b exports all messages sent by an account as JSON.`,
+			enabled:   historyComplianceEnabled,
+			capabs:    []string{"history"},
+			minParams: 1,
+			maxParams: 1,
+		},
+		"play": {
+			handler: histservPlayHandler,
+			help: `Syntax: $bPLAY <target> [limit]$b
+
+PLAY plays back history messages, rendering them into direct messages from
+HistServ. 'target' is a channel name (or 'me' for direct messages), and 'limit'
+is a message count or a time duration. Note that message playback may be
+incomplete or degraded, relative to direct playback from /HISTORY or
+CHATHISTORY.`,
+			helpShort: `$bPLAY$b plays back history messages.`,
+			enabled:   histservEnabled,
+			minParams: 1,
+			maxParams: 2,
+		},
+	}
+)
+
+// histNotice sends the client a notice from HistServ
+func histNotice(rb *ResponseBuffer, text string) {
+	rb.Add(nil, histServMask, "NOTICE", rb.target.Nick(), text)
+}
+
+func histservForgetHandler(server *Server, client *Client, command string, params []string, rb *ResponseBuffer) {
+	accountName := server.accounts.AccountToAccountName(params[0])
+	if accountName == "" {
+		histNotice(rb, client.t("Could not look up account name, proceeding anyway"))
+		accountName = params[0]
+	}
+
+	server.ForgetHistory(accountName)
+
+	histNotice(rb, fmt.Sprintf(client.t("Enqueued account %s for message deletion"), accountName))
+}
+
+func histservDeleteHandler(server *Server, client *Client, command string, params []string, rb *ResponseBuffer) {
+	var target, msgid string
+	if len(params) == 1 {
+		msgid = params[0]
+	} else {
+		target, msgid = params[0], params[1]
+	}
+
+	accountName := "*"
+	hasPrivs := client.HasRoleCapabs("history")
+	if !hasPrivs {
+		accountName = client.AccountName()
+		if !(server.Config().History.Retention.AllowIndividualDelete && accountName != "*") {
+			hsNotice(rb, client.t("Insufficient privileges"))
+			return
+		}
+	}
+
+	err := server.DeleteMessage(target, msgid, accountName)
+	if err == nil {
+		hsNotice(rb, client.t("Successfully deleted message"))
+	} else {
+		if hasPrivs {
+			hsNotice(rb, fmt.Sprintf(client.t("Error deleting message: %v"), err))
+		} else {
+			hsNotice(rb, client.t("Could not delete message"))
+		}
+	}
+}
+
+func histservExportHandler(server *Server, client *Client, command string, params []string, rb *ResponseBuffer) {
+	cfAccount, err := CasefoldName(params[0])
+	if err != nil {
+		histNotice(rb, client.t("Invalid account name"))
+		return
+	}
+
+	config := server.Config()
+	filename := fmt.Sprintf("%s@%s.json", cfAccount, time.Now().UTC().Format(IRCv3TimestampFormat))
+	pathname := config.getOutputPath(filename)
+	outfile, err := os.Create(pathname)
+	if err != nil {
+		hsNotice(rb, fmt.Sprintf(client.t("Error opening export file: %v"), err))
+	} else {
+		hsNotice(rb, fmt.Sprintf(client.t("Started exporting account data to file %s"), pathname))
+	}
+
+	go histservExportAndNotify(server, cfAccount, outfile, client.Nick())
+}
+
+func histservExportAndNotify(server *Server, cfAccount string, outfile *os.File, alertNick string) {
+	defer func() {
+		if r := recover(); r != nil {
+			server.logger.Error("history",
+				fmt.Sprintf("Panic in history export routine: %v\n%s", r, debug.Stack()))
+		}
+	}()
+
+	defer outfile.Close()
+	writer := bufio.NewWriter(outfile)
+	defer writer.Flush()
+
+	server.historyDB.Export(cfAccount, writer)
+
+	client := server.clients.Get(alertNick)
+	if client != nil && client.HasRoleCapabs("history") {
+		client.Send(nil, histServMask, "NOTICE", client.Nick(), fmt.Sprintf(client.t("Data export for %[1]s completed and written to %[2]s"), cfAccount, outfile.Name()))
+	}
+}
+
+func histservPlayHandler(server *Server, client *Client, command string, params []string, rb *ResponseBuffer) {
+	items, _, err := easySelectHistory(server, client, params)
+	if err != nil {
+		hsNotice(rb, client.t("Could not retrieve history"))
+		return
+	}
+
+	playMessage := func(timestamp time.Time, nick, message string) {
+		hsNotice(rb, fmt.Sprintf("%s <%s> %s", timestamp.Format("15:04:05"), stripMaskFromNick(nick), message))
+	}
+
+	for _, item := range items {
+		// TODO: support a few more of these, maybe JOIN/PART/QUIT
+		if item.Type != history.Privmsg && item.Type != history.Notice {
+			continue
+		}
+		if len(item.Message.Split) == 0 {
+			playMessage(item.Message.Time, item.Nick, item.Message.Message)
+		} else {
+			for _, pair := range item.Message.Split {
+				playMessage(item.Message.Time, item.Nick, pair.Message)
+			}
+		}
+	}
+
+	hsNotice(rb, client.t("End of history playback"))
+}
+
+// handles parameter parsing and history queries for /HISTORY and /HISTSERV PLAY
+func easySelectHistory(server *Server, client *Client, params []string) (items []history.Item, channel *Channel, err error) {
+	target := params[0]
+	if strings.ToLower(target) == "me" {
+		target = "*"
+	}
+	channel, sequence, err := server.GetHistorySequence(nil, client, target)
+
+	if sequence == nil || err != nil {
+		return nil, nil, errNoSuchChannel
+	}
+
+	var duration time.Duration
+	maxChathistoryLimit := server.Config().History.ChathistoryMax
+	limit := 100
+	if maxChathistoryLimit < limit {
+		limit = maxChathistoryLimit
+	}
+	if len(params) > 1 {
+		providedLimit, err := strconv.Atoi(params[1])
+		if err == nil && providedLimit != 0 {
+			limit = providedLimit
+			if maxChathistoryLimit < limit {
+				limit = maxChathistoryLimit
+			}
+		} else if err != nil {
+			duration, err = time.ParseDuration(params[1])
+			if err == nil {
+				limit = maxChathistoryLimit
+			}
+		}
+	}
+
+	if duration == 0 {
+		items, _, err = sequence.Between(history.Selector{}, history.Selector{}, limit)
+	} else {
+		now := time.Now().UTC()
+		start := history.Selector{Time: now}
+		end := history.Selector{Time: now.Add(-duration)}
+		items, _, err = sequence.Between(start, end, limit)
+	}
+	return
+}

irc/mysql/config.go

@@ -19,4 +19,5 @@ type Config struct {
 
 	// XXX these are copied from elsewhere in the config:
 	ExpireTime           time.Duration
+	TrackAccountMessages bool
 }

irc/mysql/history.go

@@ -7,7 +7,10 @@ import (
 	"bytes"
 	"context"
 	"database/sql"
+	"encoding/json"
+	"errors"
 	"fmt"
+	"io"
 	"runtime/debug"
 	"sync"
 	"sync/atomic"
@@ -19,6 +22,10 @@ import (
 	"github.com/oragono/oragono/irc/utils"
 )
 
+var (
+	ErrDisallowed = errors.New("disallowed")
+)
+
 const (
 	// maximum length in bytes of any message target (nickname or channel name) in its
 	// canonicalized (i.e., casefolded) state:
@@ -27,30 +34,46 @@ const (
 	// latest schema of the db
 	latestDbSchema   = "2"
 	keySchemaVersion = "db.version"
+	// minor version indicates rollback-safe upgrades, i.e.,
+	// you can downgrade oragono and everything will work
+	latestDbMinorVersion  = "1"
+	keySchemaMinorVersion = "db.minorversion"
 	cleanupRowLimit       = 50
 	cleanupPauseTime      = 10 * time.Minute
 )
 
+type e struct{}
+
 type MySQL struct {
 	timeout              int64
+	trackAccountMessages uint32
 	db                   *sql.DB
 	logger               *logger.Manager
 
 	insertHistory        *sql.Stmt
 	insertSequence       *sql.Stmt
 	insertConversation   *sql.Stmt
+	insertAccountMessage *sql.Stmt
 
 	stateMutex sync.Mutex
 	config     Config
+
+	wakeForgetter chan e
 }
 
 func (mysql *MySQL) Initialize(logger *logger.Manager, config Config) {
 	mysql.logger = logger
+	mysql.wakeForgetter = make(chan e, 1)
 	mysql.SetConfig(config)
 }
 
 func (mysql *MySQL) SetConfig(config Config) {
 	atomic.StoreInt64(&mysql.timeout, int64(config.Timeout))
+	var trackAccountMessages uint32
+	if config.TrackAccountMessages {
+		trackAccountMessages = 1
+	}
+	atomic.StoreUint32(&mysql.trackAccountMessages, trackAccountMessages)
 	mysql.stateMutex.Lock()
 	mysql.config = config
 	mysql.stateMutex.Unlock()
@@ -85,6 +108,7 @@ func (m *MySQL) Open() (err error) {
 	}
 
 	go m.cleanupLoop()
+	go m.forgetLoop()
 
 	return nil
 }
@@ -109,14 +133,35 @@ func (mysql *MySQL) fixSchemas() (err error) {
 		if err != nil {
 			return
 		}
+		_, err = mysql.db.Exec(`insert into metadata (key_name, value) values (?, ?);`, keySchemaMinorVersion, latestDbMinorVersion)
+		if err != nil {
+			return
+		}
+		return
 	} else if err == nil && schema != latestDbSchema {
 		// TODO figure out what to do about schema changes
 		return &utils.IncompatibleSchemaError{CurrentVersion: schema, RequiredVersion: latestDbSchema}
-	} else {
+	} else if err != nil {
 		return err
 	}
 
-	return nil
+	var minorVersion string
+	err = mysql.db.QueryRow(`select value from metadata where key_name = ?;`, keySchemaMinorVersion).Scan(&minorVersion)
+	if err == sql.ErrNoRows {
+		// XXX for now, the only minor version upgrade is the account tracking tables
+		err = mysql.createComplianceTables()
+		if err != nil {
+			return
+		}
+		_, err = mysql.db.Exec(`insert into metadata (key_name, value) values (?, ?);`, keySchemaMinorVersion, latestDbMinorVersion)
+		if err != nil {
+			return
+		}
+	} else if err == nil && minorVersion != latestDbMinorVersion {
+		// TODO: if minorVersion < latestDbMinorVersion, upgrade,
+		// if latestDbMinorVersion < minorVersion, ignore because backwards compatible
+	}
+	return
 }
 
 func (mysql *MySQL) createTables() (err error) {
@@ -155,6 +200,32 @@ func (mysql *MySQL) createTables() (err error) {
 		return err
 	}
 
+	err = mysql.createComplianceTables()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (mysql *MySQL) createComplianceTables() (err error) {
+	_, err = mysql.db.Exec(fmt.Sprintf(`CREATE TABLE account_messages (
+		history_id BIGINT UNSIGNED NOT NULL PRIMARY KEY,
+		account VARBINARY(%[1]d) NOT NULL,
+		KEY (account, history_id)
+	) CHARSET=ascii COLLATE=ascii_bin;`, MaxTargetLength))
+	if err != nil {
+		return err
+	}
+
+	_, err = mysql.db.Exec(fmt.Sprintf(`CREATE TABLE forget (
+		id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+		account VARBINARY(%[1]d) NOT NULL
+	) CHARSET=ascii COLLATE=ascii_bin;`, MaxTargetLength))
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -191,7 +262,10 @@ func (mysql *MySQL) cleanupLoop() {
 }
 
 func (mysql *MySQL) doCleanup(age time.Duration) (count int, err error) {
-	ids, maxNanotime, err := mysql.selectCleanupIDs(age)
+	ctx, cancel := context.WithTimeout(context.Background(), cleanupPauseTime)
+	defer cancel()
+
+	ids, maxNanotime, err := mysql.selectCleanupIDs(ctx, age)
 	if len(ids) == 0 {
 		mysql.logger.Debug("mysql", "found no rows to clean up")
 		return
@@ -199,6 +273,10 @@ func (mysql *MySQL) doCleanup(age time.Duration) (count int, err error) {
 
 	mysql.logger.Debug("mysql", fmt.Sprintf("deleting %d history rows, max age %s", len(ids), utils.NanoToTimestamp(maxNanotime)))
 
+	return len(ids), mysql.deleteHistoryIDs(ctx, ids)
+}
+
+func (mysql *MySQL) deleteHistoryIDs(ctx context.Context, ids []uint64) (err error) {
 	// can't use ? binding for a variable number of arguments, build the IN clause manually
 	var inBuf bytes.Buffer
 	inBuf.WriteByte('(')
@@ -210,25 +288,30 @@ func (mysql *MySQL) doCleanup(age time.Duration) (count int, err error) {
 	}
 	inBuf.WriteRune(')')
 
-	_, err = mysql.db.Exec(fmt.Sprintf(`DELETE FROM conversations WHERE history_id in %s;`, inBuf.Bytes()))
+	_, err = mysql.db.ExecContext(ctx, fmt.Sprintf(`DELETE FROM conversations WHERE history_id in %s;`, inBuf.Bytes()))
 	if err != nil {
 		return
 	}
-	_, err = mysql.db.Exec(fmt.Sprintf(`DELETE FROM sequence WHERE history_id in %s;`, inBuf.Bytes()))
+	_, err = mysql.db.ExecContext(ctx, fmt.Sprintf(`DELETE FROM sequence WHERE history_id in %s;`, inBuf.Bytes()))
 	if err != nil {
 		return
 	}
-	_, err = mysql.db.Exec(fmt.Sprintf(`DELETE FROM history WHERE id in %s;`, inBuf.Bytes()))
+	if mysql.isTrackingAccountMessages() {
+		_, err = mysql.db.ExecContext(ctx, fmt.Sprintf(`DELETE FROM account_messages WHERE history_id in %s;`, inBuf.Bytes()))
+		if err != nil {
+			return
+		}
+	}
+	_, err = mysql.db.ExecContext(ctx, fmt.Sprintf(`DELETE FROM history WHERE id in %s;`, inBuf.Bytes()))
 	if err != nil {
 		return
 	}
 
-	count = len(ids)
 	return
 }
 
-func (mysql *MySQL) selectCleanupIDs(age time.Duration) (ids []uint64, maxNanotime int64, err error) {
-	rows, err := mysql.db.Query(`
+func (mysql *MySQL) selectCleanupIDs(ctx context.Context, age time.Duration) (ids []uint64, maxNanotime int64, err error) {
+	rows, err := mysql.db.QueryContext(ctx, `
 		SELECT history.id, sequence.nanotime
 		FROM history
 		LEFT JOIN sequence ON history.id = sequence.history_id
@@ -266,6 +349,109 @@ func (mysql *MySQL) selectCleanupIDs(age time.Duration) (ids []uint64, maxNanoti
 	return
 }
 
+// wait for forget queue items and process them one by one
+func (mysql *MySQL) forgetLoop() {
+	defer func() {
+		if r := recover(); r != nil {
+			mysql.logger.Error("mysql",
+				fmt.Sprintf("Panic in forget routine: %v\n%s", r, debug.Stack()))
+			time.Sleep(cleanupPauseTime)
+			go mysql.forgetLoop()
+		}
+	}()
+
+	for {
+		for {
+			found, err := mysql.doForget()
+			mysql.logError("error processing forget", err)
+			if err != nil {
+				time.Sleep(cleanupPauseTime)
+			}
+			if !found {
+				break
+			}
+		}
+
+		<-mysql.wakeForgetter
+	}
+}
+
+// dequeue an item from the forget queue and process it
+func (mysql *MySQL) doForget() (found bool, err error) {
+	id, account, err := func() (id int64, account string, err error) {
+		ctx, cancel := context.WithTimeout(context.Background(), cleanupPauseTime)
+		defer cancel()
+
+		row := mysql.db.QueryRowContext(ctx,
+			`SELECT forget.id, forget.account FROM forget LIMIT 1;`)
+		err = row.Scan(&id, &account)
+		if err == sql.ErrNoRows {
+			return 0, "", nil
+		}
+		return
+	}()
+
+	if err != nil || account == "" {
+		return false, err
+	}
+
+	found = true
+
+	var count int
+	for {
+		start := time.Now()
+		count, err = mysql.doForgetIteration(account)
+		elapsed := time.Since(start)
+		if err != nil {
+			return true, err
+		}
+		if count == 0 {
+			break
+		}
+		time.Sleep(elapsed)
+	}
+
+	mysql.logger.Debug("mysql", "forget complete for account", account)
+
+	ctx, cancel := context.WithTimeout(context.Background(), cleanupPauseTime)
+	defer cancel()
+	_, err = mysql.db.ExecContext(ctx, `DELETE FROM forget where id = ?;`, id)
+	return
+}
+
+func (mysql *MySQL) doForgetIteration(account string) (count int, err error) {
+	ctx, cancel := context.WithTimeout(context.Background(), cleanupPauseTime)
+	defer cancel()
+
+	rows, err := mysql.db.QueryContext(ctx, `
+		SELECT account_messages.history_id
+		FROM account_messages
+		WHERE account_messages.account = ?
+		LIMIT ?;`, account, cleanupRowLimit)
+	if err != nil {
+		return
+	}
+	defer rows.Close()
+
+	var ids []uint64
+	for rows.Next() {
+		var id uint64
+		err = rows.Scan(&id)
+		if err != nil {
+			return
+		}
+		ids = append(ids, id)
+	}
+
+	if len(ids) == 0 {
+		return
+	}
+
+	mysql.logger.Debug("mysql", fmt.Sprintf("deleting %d history rows from account %s", len(ids), account))
+	err = mysql.deleteHistoryIDs(ctx, ids)
+	return len(ids), err
+}
+
 func (mysql *MySQL) prepareStatements() (err error) {
 	mysql.insertHistory, err = mysql.db.Prepare(`INSERT INTO history
 		(data, msgid) VALUES (?, ?);`)
@@ -282,6 +468,11 @@ func (mysql *MySQL) prepareStatements() (err error) {
 	if err != nil {
 		return
 	}
+	mysql.insertAccountMessage, err = mysql.db.Prepare(`INSERT INTO account_messages
+		(history_id, account) VALUES (?, ?);`)
+	if err != nil {
+		return
+	}
 
 	return
 }
@@ -290,6 +481,10 @@ func (mysql *MySQL) getTimeout() time.Duration {
 	return time.Duration(atomic.LoadInt64(&mysql.timeout))
 }
 
+func (mysql *MySQL) isTrackingAccountMessages() bool {
+	return atomic.LoadUint32(&mysql.trackAccountMessages) != 0
+}
+
 func (mysql *MySQL) logError(context string, err error) (quit bool) {
 	if err != nil {
 		mysql.logger.Error("mysql", context, err.Error())
@@ -298,7 +493,27 @@ func (mysql *MySQL) logError(context string, err error) (quit bool) {
 	return false
 }
 
-func (mysql *MySQL) AddChannelItem(target string, item history.Item) (err error) {
+func (mysql *MySQL) Forget(account string) {
+	if mysql.db == nil || account == "" {
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), mysql.getTimeout())
+	defer cancel()
+
+	_, err := mysql.db.ExecContext(ctx, `INSERT INTO forget (account) VALUES (?);`, account)
+	if mysql.logError("can't insert into forget table", err) {
+		return
+	}
+
+	// wake up the forget goroutine if it's blocked:
+	select {
+	case mysql.wakeForgetter <- e{}:
+	default:
+	}
+}
+
+func (mysql *MySQL) AddChannelItem(target string, item history.Item, account string) (err error) {
 	if mysql.db == nil {
 		return
 	}
@@ -316,6 +531,15 @@ func (mysql *MySQL) AddChannelItem(target string, item history.Item) (err error)
 	}
 
 	err = mysql.insertSequenceEntry(ctx, target, item.Message.Time.UnixNano(), id)
+	if err != nil {
+		return
+	}
+
+	err = mysql.insertAccountMessageEntry(ctx, id, account)
+	if err != nil {
+		return
+	}
+
 	return
 }
 
@@ -354,6 +578,15 @@ func (mysql *MySQL) insertBase(ctx context.Context, item history.Item) (id int64
 	return
 }
 
+func (mysql *MySQL) insertAccountMessageEntry(ctx context.Context, id int64, account string) (err error) {
+	if account == "" || !mysql.isTrackingAccountMessages() {
+		return
+	}
+	_, err = mysql.insertAccountMessage.ExecContext(ctx, id, account)
+	mysql.logError("could not insert account-message entry", err)
+	return
+}
+
 func (mysql *MySQL) AddDirectMessage(sender, senderAccount, recipient, recipientAccount string, item history.Item) (err error) {
 	if mysql.db == nil {
 		return
@@ -399,10 +632,102 @@ func (mysql *MySQL) AddDirectMessage(sender, senderAccount, recipient, recipient
 		}
 	}
 
+	err = mysql.insertAccountMessageEntry(ctx, id, senderAccount)
+	if err != nil {
 		return
 	}
 
-func (mysql *MySQL) msgidToTime(ctx context.Context, msgid string) (result time.Time, err error) {
+	return
+}
+
+// note that accountName is the unfolded name
+func (mysql *MySQL) DeleteMsgid(msgid, accountName string) (err error) {
+	if mysql.db == nil {
+		return nil
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), mysql.getTimeout())
+	defer cancel()
+
+	_, id, data, err := mysql.lookupMsgid(ctx, msgid, true)
+	if err != nil {
+		return
+	}
+
+	if accountName != "*" {
+		var item history.Item
+		err = unmarshalItem(data, &item)
+		// delete if the entry is corrupt
+		if err == nil && item.AccountName != accountName {
+			return ErrDisallowed
+		}
+	}
+
+	err = mysql.deleteHistoryIDs(ctx, []uint64{id})
+	mysql.logError("couldn't delete msgid", err)
+	return
+}
+
+func (mysql *MySQL) Export(account string, writer io.Writer) {
+	if mysql.db == nil {
+		return
+	}
+
+	var err error
+	var lastSeen uint64
+	for {
+		rows := func() (count int) {
+			ctx, cancel := context.WithTimeout(context.Background(), cleanupPauseTime)
+			defer cancel()
+
+			rows, rowsErr := mysql.db.QueryContext(ctx, `
+				SELECT account_messages.history_id, history.data, sequence.target FROM account_messages
+				INNER JOIN history ON history.id = account_messages.history_id
+				INNER JOIN sequence ON account_messages.history_id = sequence.history_id
+				WHERE account_messages.account = ? AND account_messages.history_id > ?
+				LIMIT ?`, account, lastSeen, cleanupRowLimit)
+			if rowsErr != nil {
+				err = rowsErr
+				return
+			}
+			defer rows.Close()
+			for rows.Next() {
+				var id uint64
+				var blob, jsonBlob []byte
+				var target string
+				var item history.Item
+				err = rows.Scan(&id, &blob, &target)
+				if err != nil {
+					return
+				}
+				err = unmarshalItem(blob, &item)
+				if err != nil {
+					return
+				}
+				item.CfCorrespondent = target
+				jsonBlob, err = json.Marshal(item)
+				if err != nil {
+					return
+				}
+				count++
+				if lastSeen < id {
+					lastSeen = id
+				}
+				writer.Write(jsonBlob)
+				writer.Write([]byte{'\n'})
+			}
+			return
+		}()
+		if rows == 0 || err != nil {
+			break
+		}
+	}
+
+	mysql.logError("could not export history", err)
+	return
+}
+
+func (mysql *MySQL) lookupMsgid(ctx context.Context, msgid string, includeData bool) (result time.Time, id uint64, data []byte, err error) {
 	// in theory, we could optimize out a roundtrip to the database by using a subquery instead:
 	// sequence.nanotime > (
 	//     SELECT sequence.nanotime FROM sequence, history
@@ -415,15 +740,27 @@ func (mysql *MySQL) msgidToTime(ctx context.Context, msgid string) (result time.
 	if err != nil {
 		return
 	}
-	row := mysql.db.QueryRowContext(ctx, `
-		SELECT sequence.nanotime FROM sequence
+	cols := `sequence.nanotime`
+	if includeData {
+		cols = `sequence.nanotime, sequence.history_id, history.data`
+	}
+	row := mysql.db.QueryRowContext(ctx, fmt.Sprintf(`
+		SELECT %s FROM sequence
 		INNER JOIN history ON history.id = sequence.history_id
-		WHERE history.msgid = ? LIMIT 1;`, decoded)
+		WHERE history.msgid = ? LIMIT 1;`, cols), decoded)
 	var nanotime int64
+	if !includeData {
 		err = row.Scan(&nanotime)
-	if mysql.logError("could not resolve msgid to time", err) {
+	} else {
+		err = row.Scan(&nanotime, &id, &data)
+	}
+	if err != sql.ErrNoRows {
+		mysql.logError("could not resolve msgid to time", err)
+	}
+	if err != nil {
 		return
 	}
+
 	result = time.Unix(0, nanotime).UTC()
 	return
 }
@@ -519,14 +856,14 @@ func (s *mySQLHistorySequence) Between(start, end history.Selector, limit int) (
 
 	startTime := start.Time
 	if start.Msgid != "" {
-		startTime, err = s.mysql.msgidToTime(ctx, start.Msgid)
+		startTime, _, _, err = s.mysql.lookupMsgid(ctx, start.Msgid, false)
 		if err != nil {
 			return nil, false, err
 		}
 	}
 	endTime := end.Time
 	if end.Msgid != "" {
-		endTime, err = s.mysql.msgidToTime(ctx, end.Msgid)
+		endTime, _, _, err = s.mysql.lookupMsgid(ctx, end.Msgid, false)
 		if err != nil {
 			return nil, false, err
 		}

irc/nickname.go

@@ -80,7 +80,7 @@ func performNickChange(server *Server, client *Client, target *Client, session *
 	}
 
 	for _, channel := range client.Channels() {
-		channel.AddHistoryItem(histItem)
+		channel.AddHistoryItem(histItem, details.account)
 	}
 
 	if target.Registered() {

irc/roleplay.go

@@ -91,7 +91,7 @@ func sendRoleplayMessage(server *Server, client *Client, source string, targetSt
 			Type:    history.Privmsg,
 			Message: splitMessage,
 			Nick:    source,
-		})
+		}, client.Account())
 	} else {
 		target, err := CasefoldName(targetString)
 		user := server.clients.Get(target)

irc/server.go

@@ -879,6 +879,76 @@ func (server *Server) GetHistorySequence(providedChannel *Channel, client *Clien
 	return
 }
 
+func (server *Server) ForgetHistory(accountName string) {
+	// sanity check
+	if accountName == "*" {
+		return
+	}
+
+	config := server.Config()
+	if !config.History.Enabled {
+		return
+	}
+
+	if cfAccount, err := CasefoldName(accountName); err == nil {
+		server.historyDB.Forget(cfAccount)
+	}
+
+	persistent := config.History.Persistent
+	if persistent.Enabled && persistent.UnregisteredChannels && persistent.RegisteredChannels == PersistentMandatory && persistent.DirectMessages == PersistentMandatory {
+		return
+	}
+
+	predicate := func(item *history.Item) bool { return item.AccountName == accountName }
+
+	for _, channel := range server.channels.Channels() {
+		channel.history.Delete(predicate)
+	}
+
+	for _, client := range server.clients.AllClients() {
+		client.history.Delete(predicate)
+	}
+}
+
+// deletes a message. target is a hint about what buffer it's in (not required for
+// persistent history, where all the msgids are indexed together). if accountName
+// is anything other than "*", it must match the recorded AccountName of the message
+func (server *Server) DeleteMessage(target, msgid, accountName string) (err error) {
+	config := server.Config()
+	var hist *history.Buffer
+
+	if target != "" {
+		if target[0] == '#' {
+			channel := server.channels.Get(target)
+			if channel != nil {
+				if status, _ := channel.historyStatus(config); status == HistoryEphemeral {
+					hist = &channel.history
+				}
+			}
+		} else {
+			client := server.clients.Get(target)
+			if client != nil {
+				if status, _ := client.historyStatus(config); status == HistoryEphemeral {
+					hist = &client.history
+				}
+			}
+		}
+	}
+
+	if hist == nil {
+		err = server.historyDB.DeleteMsgid(msgid, accountName)
+	} else {
+		count := hist.Delete(func(item *history.Item) bool {
+			return item.Message.Msgid == msgid && (accountName == "*" || item.AccountName == accountName)
+		})
+		if count == 0 {
+			err = errNoop
+		}
+	}
+
+	return
+}
+
 // elistMatcher takes and matches ELIST conditions
 type elistMatcher struct {
 	MinClientsActive bool

irc/services.go

@@ -82,6 +82,13 @@ var OragonoServices = map[string]*ircService{
 		Commands:       hostservCommands,
 		HelpBanner:     hostservHelp,
 	},
+	"histserv": {
+		Name:           "HistServ",
+		ShortName:      "HISTSERV",
+		CommandAliases: []string{"HISTSERV"},
+		Commands:       histservCommands,
+		HelpBanner:     histservHelp,
+	},
 }
 
 // all service commands at the protocol level, by uppercase command name

oragono.yaml

@@ -280,6 +280,10 @@ server:
     secure-nets:
         # - "10.0.0.0/8"
 
+    # oragono will write files to disk under certain circumstances, e.g.,
+    # CPU profiling or data export. by default, these files will be written
+    # to the working directory. set this to customize:
+    # output-path: "/home/oragono/out"
 
 # account options
 accounts:
@@ -577,6 +581,7 @@ oper-classes:
             - "samode"
             - "vhosts"
             - "chanreg"
+            - "history"
 
 # ircd operators
 opers:
@@ -772,7 +777,8 @@ roleplay:
     # add the real nickname, in parentheses, to the end of every roleplay message?
     add-suffix: true
 
-# message history tracking, for the RESUME extension and possibly other uses in future
+# history message storage: this is used by CHATHISTORY, HISTORY, znc.in/playback,
+# various autoreplay features, and the resume extension
 history:
     # should we store messages for later playback?
     # by default, messages are stored in RAM only; they do not persist
@@ -841,3 +847,13 @@ history:
         # if you enable this, strict nickname reservation is strongly recommended
         # as well.
         direct-messages: "opt-out"
+
+    # options to control how messages are stored and deleted:
+    retention:
+        # allow users to delete their own messages from history?
+        allow-individual-delete: false
+
+        # if persistent history is enabled, create additional index tables,
+        # allowing deletion of JSON export of an account's messages. this
+        # may be needed for compliance with data privacy regulations.
+        enable-account-indexing: false