Refuse API writes that are not application/json (closes #271)

A page on another origin of the same site could send a text/plain or
form POST with the user's cookie, since a browser sends such a request
without a preflight. RequireJSON on the /api/v1 router answers 415 to a
POST, PUT or DELETE whose Content-Type is not application/json, or that
has none, before the handler runs.

The web client and neoirc-cli already send the header on every request.

Model: opus-5-5

Dockerfile

@@ -83,14 +83,15 @@ RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /neoirc-cli ./cmd/neoir
 # stage's chain and nothing else.
 # alpine:3.21, 2026-02-26
 FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
-RUN apk add --no-cache ca-certificates \
-    && addgroup -S neoirc && adduser -S neoirc -G neoirc \
-    && mkdir -p /var/lib/neoirc \
-    && chown neoirc:neoirc /var/lib/neoirc
+# su-exec 0.2-r3, 2026-11-10
+RUN apk add --no-cache ca-certificates su-exec=0.2-r3 \
+    && addgroup -S neoirc && adduser -S neoirc -G neoirc
 COPY --from=builder /neoircd /usr/local/bin/neoircd
+COPY deploy/docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
 
-USER neoirc
+# No USER: the entrypoint starts as root to give /var/lib/neoirc to neoirc,
+# then runs neoircd as neoirc.
 EXPOSE 8080 6667
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
     CMD wget -qO- http://localhost:8080/.well-known/healthcheck.json || exit 1
-ENTRYPOINT ["neoircd"]
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]

README.md

@@ -157,6 +157,10 @@ either.
 ### Conventions
 
 - Request and response bodies are JSON.
+- Every `POST`, `PUT` and `DELETE` request under `/api/v1/` needs the header
+  `Content-Type: application/json`, even one with no body. A request with
+  another type, or none, gets `415` with
+  `{"error": "content type must be application/json"}`.
 - Endpoints marked "needs auth" need the `neoirc_auth` cookie.
   `POST /api/v1/session` and `POST /api/v1/login` set it. A request without a
   valid cookie gets `401` with `{"error": "not registered", "numeric": 451}`.
@@ -168,8 +172,10 @@ either.
 - Request bodies for `POST /api/v1/session`, `POST /api/v1/login` and
   `POST /api/v1/messages` are limited to `MAX_MESSAGE_SIZE` bytes (default
   `4096`). A larger body gets `400` `invalid request body`.
-- The server allows cross-origin requests from any origin, with credentials. The
-  cookie is `SameSite=Strict`, so a browser sends it only from the same site.
+- `GET /api/v1/server` and `GET /.well-known/healthcheck.json` answer a request
+  from any origin with `Access-Control-Allow-Origin: *`. Every other route sends
+  no `Access-Control-Allow-*` header, so a page on another origin cannot read
+  its responses.
 
 ### The auth cookie
 
@@ -515,7 +521,8 @@ for every HTTP request when metrics are on.
 Every other `GET` path serves the web client. A path that names one of its files
 gets that file; any other path gets its `index.html`. An unknown path under
 `/api/v1/` gets a plain-text `404`. A request whose method the path does not
-take gets `405` with no body.
+take gets `405` with no body. Under `/api/v1/`, a `POST`, `PUT` or `DELETE`
+without `Content-Type: application/json` gets `415` instead.
 
 ### The message envelope
 
@@ -1722,7 +1729,8 @@ exceptions:
 
 A `neoirc.yaml` that is not valid YAML stops the server at startup. A setting
 that does not parse or is out of range also stops the server at startup, and the
-error names the setting.
+error names the setting. The same holds for a setting given a list or a map in
+`neoirc.yaml`.
 
 - `PORT` (default `8080`): the HTTP port. `0` lets the system pick a free port.
 - `IRC_LISTEN_ADDR` (default `:6667`): the address of the IRC listener. The
@@ -1790,13 +1798,17 @@ NEOIRC_HASHCASH_BITS=20
 the linter first and stops when either fails. The image:
 
 - is Alpine with the `neoircd` binary and CA certificates;
-- runs as the user `neoirc`;
+- runs `neoircd` as the user `neoirc`;
 - exposes ports 8080 and 6667;
 - keeps its database in `/var/lib/neoirc`;
 - has a `HEALTHCHECK` that calls `/.well-known/healthcheck.json` every 30
   seconds.
 
-Run it with a volume for the database and the settings as environment variables:
+The image prepares `/var/lib/neoirc` itself on every start. It creates the
+directory, gives it to `neoirc` and then runs `neoircd` as `neoirc`.
+
+Run it with a named volume for the database and the settings as environment
+variables:
 
 ```bash
 docker run -d --name neoirc \
@@ -1807,6 +1819,17 @@ docker run -d --name neoirc \
   neoirc
 ```
 
+A host directory works the same way in place of the named volume:
+
+```bash
+docker run -d --name neoirc \
+  -p 8080:8080 -p 6667:6667 \
+  -v /srv/neoirc:/var/lib/neoirc \
+  -e SERVER_NAME="My Server" \
+  -e MOTD="Welcome!" \
+  neoirc
+```
+
 ### Reverse proxy
 
 Run the server behind a reverse proxy that terminates TLS. The server itself
@@ -1814,10 +1837,14 @@ speaks plain HTTP, and the auth cookie is `Secure`, so browsers send it only
 over HTTPS. The proxy must:
 
 - Connect from an address in `TRUSTED_PROXIES`. The default trusts the private
-  ranges `10.0.0.0/8`, `172.16.0.0/12` and `192.168.0.0/16`. A proxy on the same
-  host connects from `127.0.0.1`, which the default does not trust, so set
-  `TRUSTED_PROXIES=127.0.0.1` for it.
-- Add the client's address to `X-Forwarded-For`, or set `X-Real-IP`.
+  ranges `10.0.0.0/8`, `172.16.0.0/12` and `192.168.0.0/16`. The setting must
+  hold the address the server sees the proxy connect from. For a proxy on the
+  same host:
+    - With the server outside Docker, that address is `127.0.0.1` or `::1`. The
+      default does not trust them, so set `TRUSTED_PROXIES=127.0.0.1,::1`.
+    - Through a published Docker port, that address is the Docker bridge
+      gateway, such as `172.17.0.1`. The default trusts it.
+- Add the client's address to `X-Forwarded-For`.
 - Wait at least 60 seconds for a response. A long poll can take 30 seconds, and
   the server's own write timeout is 60 seconds.
 
@@ -1873,23 +1900,34 @@ The IRC listener has no TLS.
   seconds. A request still running after 60 seconds is cancelled, and the
   connection closes without a response. Headers may be up to 1 MiB.
 - A long poll waits at most 30 seconds.
-- Every response to a well-formed request, except to a cross-origin preflight,
-  carries a `Content-Security-Policy` header:
+- Every response to a well-formed request carries a `Content-Security-Policy`
+  header:
   `default-src 'self'; script-src 'self'; style-src 'self'; connect-src 'self'; img-src 'self'; font-src 'self'; object-src 'none'; frame-ancestors 'none'; base-uri 'self'; form-action 'self'`.
   The web client works within it.
-- Cross-origin requests are allowed from any origin, with credentials. The
-  allowed methods are `GET`, `POST`, `PUT`, `DELETE` and `OPTIONS`. The allowed
-  request headers are `Accept`, `Content-Type` and `X-CSRF-Token`. The cookie's
-  `SameSite=Strict` still keeps it to the same site.
+- `GET /api/v1/server` and `GET /.well-known/healthcheck.json` answer a request
+  from any origin with `Access-Control-Allow-Origin: *`. Every other route sends
+  no `Access-Control-Allow-*` header, so a page on another origin cannot read
+  its responses.
 
 ### Logging
 
 The server logs with Go's `slog`, one line per event, to standard output. The
 lines are JSON, or plain text when standard output is a terminal. Every HTTP
-request is logged with its method, URL, protocol, status, latency, client
-address, user agent, referrer and request ID. The client address is the one
-found as described in [Reverse proxy](#reverse-proxy). `DEBUG=true` adds
-debug-level lines.
+request is logged with:
+
+- start time
+- method
+- URL
+- protocol
+- status
+- latency
+- client address
+- user agent
+- referrer
+- request ID
+
+The client address is the one found as described in
+[Reverse proxy](#reverse-proxy). `DEBUG=true` adds debug-level lines.
 
 ### The database
 
@@ -1972,7 +2010,8 @@ and their sessions to end. Then it closes the database.
   gets a message.
 - `internal/hashcash/`: stamp checking and minting.
 - `internal/ratelimit/`: the per-address login rate limiter.
-- `internal/middleware/`: request logging, cross-origin requests, the
+- `internal/middleware/`: finding the client's address, request logging,
+  cross-origin requests, the API's `Content-Type` check, the
   `Content-Security-Policy` header and metrics.
 - `internal/healthcheck/` and `internal/stats/`: the health check and its
   counters.
@@ -1985,6 +2024,8 @@ and their sessions to end. Then it closes the database.
 - `schema/`: JSON Schema files for the message envelope, with their own
   `README.md`.
 - `script/`: the entrypoints below.
+- `deploy/`: `docker-entrypoint.sh`, the image's entrypoint, which prepares
+  `/var/lib/neoirc` and starts `neoircd` as `neoirc`.
 - `CONVENTIONS.md`, `REPO_POLICIES.md` and `AGENTS.md`: the architecture
   conventions, the repository policies and the rules for coding agents.
 

deploy/docker-entrypoint.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+# deploy/docker-entrypoint.sh: the image's ENTRYPOINT, run as root. A host
+# directory mounted at /var/lib/neoirc keeps the host's owner, so this gives
+# it to neoirc before running neoircd as neoirc.
+set -eu
+
+main() {
+    mkdir -p /var/lib/neoirc
+    chown -R neoirc:neoirc /var/lib/neoirc
+    chmod 0700 /var/lib/neoirc
+    exec su-exec neoirc neoircd "$@"
+}
+
+main "$@"

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/prometheus/client_golang v1.23.2
 	github.com/rivo/tview v0.42.0
 	github.com/slok/go-http-metrics v0.13.0
+	github.com/spf13/cast v1.10.0
 	github.com/spf13/viper v1.21.0
 	go.uber.org/fx v1.24.0
 	go4.org/netipx v0.0.0-20260823151212-3075585bcbeb
@@ -41,7 +42,6 @@ require (
 	github.com/sagikazarmark/locafero v0.11.0 // indirect
 	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
 	github.com/spf13/afero v1.15.0 // indirect
-	github.com/spf13/cast v1.10.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	go.uber.org/dig v1.19.0 // indirect

internal/config/config.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/spf13/cast"
 	"github.com/spf13/viper"
 	"go.uber.org/fx"
 	"go4.org/netipx"
@@ -35,12 +36,16 @@ Type /help for available commands.`
 const DefaultDBURL = "file:///var/lib/neoirc/state.db" +
 	"?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)"
 
-// defaultTrustedProxies is TRUSTED_PROXIES when it is not set: the
+// DefaultTrustedProxies is TRUSTED_PROXIES when it is not set: the
 // private address ranges of RFC 1918.
-const defaultTrustedProxies = "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16"
+const DefaultTrustedProxies = "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16"
 
 var errOutOfRange = errors.New("setting out of range")
 
+var errNeverMatches = errors.New("entry can never match a connection")
+
+var errListOrMap = errors.New("a list or a map")
+
 // Params defines the dependencies for creating a Config.
 type Params struct {
 	fx.In
@@ -77,8 +82,9 @@ type Config struct {
 }
 
 // New creates a new Config by reading from files and environment variables.
-// It returns an error when a number, true/false, duration or address
-// setting does not parse or is out of range.
+// It returns an error when the config file does not parse, when the file
+// gives a setting a list or a map, and when a number, true/false,
+// duration or address setting does not parse or is out of range.
 func New(
 	_ fx.Lifecycle, params Params,
 ) (*Config, error) {
@@ -111,33 +117,20 @@ func New(
 	viper.SetDefault("LOGIN_RATE_LIMIT", "1")
 	viper.SetDefault("LOGIN_RATE_BURST", "5")
 	viper.SetDefault("IRC_LISTEN_ADDR", ":6667")
-	viper.SetDefault("TRUSTED_PROXIES", defaultTrustedProxies)
+	viper.SetDefault("TRUSTED_PROXIES", DefaultTrustedProxies)
 
 	err := viper.ReadInConfig()
 	if err != nil {
 		var notFound viper.ConfigFileNotFoundError
 		if !errors.As(err, &notFound) {
-			log.Error("config file malformed", "error", err)
-			panic(err)
+			return nil, fmt.Errorf("cannot read %s: %w",
+				viper.ConfigFileUsed(), err)
 		}
 	}
 
 	cfg := &Config{
-		DBURL:              viper.GetString("DBURL"),
-		SentryDSN:          viper.GetString("SENTRY_DSN"),
-		MetricsUsername:    viper.GetString("METRICS_USERNAME"),
-		MetricsPassword:    viper.GetString("METRICS_PASSWORD"),
-		MessageMaxAge:      viper.GetString("MESSAGE_MAX_AGE"),
-		QueueMaxAge:        viper.GetString("QUEUE_MAX_AGE"),
-		MOTD:               viper.GetString("MOTD"),
-		ServerName:         viper.GetString("SERVER_NAME"),
-		FederationKey:      viper.GetString("FEDERATION_KEY"),
-		SessionIdleTimeout: viper.GetString("SESSION_IDLE_TIMEOUT"),
-		OperName:           viper.GetString("NEOIRC_OPER_NAME"),
-		OperPassword:       viper.GetString("NEOIRC_OPER_PASSWORD"),
-		IRCListenAddr:      viper.GetString("IRC_LISTEN_ADDR"),
-		log:                log,
-		params:             &params,
+		log:    log,
+		params: &params,
 	}
 
 	err = parseSettings(cfg)
@@ -145,13 +138,6 @@ func New(
 		return nil, err
 	}
 
-	// Viper counts an empty environment variable as unset, but an
-	// empty IRC_LISTEN_ADDR must turn the IRC listener off.
-	ircListenAddr, set := os.LookupEnv("IRC_LISTEN_ADDR")
-	if set {
-		cfg.IRCListenAddr = ircListenAddr
-	}
-
 	if cfg.Debug {
 		params.Logger.EnableDebugLogging()
 		cfg.log = params.Logger.Get()
@@ -160,13 +146,24 @@ func New(
 	return cfg, nil
 }
 
-// parseSettings reads the number, true/false and address settings into
-// cfg and checks the duration settings. Each number and duration must be
-// above zero. PORT and NEOIRC_HASHCASH_BITS may also be zero: port 0 lets
-// the system pick a port, and 0 bits turns proof of work off. The error
-// names each setting that does not parse or is out of range.
+// parseSettings reads every setting into cfg. Each number and duration
+// must be above zero. PORT and NEOIRC_HASHCASH_BITS may also be zero:
+// port 0 lets the system pick a port, and 0 bits turns proof of work off.
+// The error names each setting that is a list or a map, does not parse or
+// is out of range.
 func parseSettings(cfg *Config) error {
 	return errors.Join(
+		parseString("DBURL", &cfg.DBURL),
+		parseString("SENTRY_DSN", &cfg.SentryDSN),
+		parseString("METRICS_USERNAME", &cfg.MetricsUsername),
+		parseString("METRICS_PASSWORD", &cfg.MetricsPassword),
+		parseString("MOTD", &cfg.MOTD),
+		parseString("SERVER_NAME", &cfg.ServerName),
+		parseString("FEDERATION_KEY", &cfg.FederationKey),
+		parseString("NEOIRC_OPER_NAME", &cfg.OperName),
+		parseString("NEOIRC_OPER_PASSWORD", &cfg.OperPassword),
+		// The empty string turns the IRC listener off.
+		parseStringAllowEmptyEnv("IRC_LISTEN_ADDR", &cfg.IRCListenAddr),
 		parseInt("PORT", 0, &cfg.Port),
 		parseInt("MAX_MESSAGE_SIZE", 1, &cfg.MaxMessageSize),
 		parseInt("NEOIRC_HASHCASH_BITS", 0, &cfg.HashcashBits),
@@ -174,38 +171,64 @@ func parseSettings(cfg *Config) error {
 		parseFloat("LOGIN_RATE_LIMIT", &cfg.LoginRateLimit),
 		parseBool("DEBUG", &cfg.Debug),
 		parseBool("MAINTENANCE_MODE", &cfg.MaintenanceMode),
-		checkDuration("MESSAGE_MAX_AGE", cfg.MessageMaxAge),
-		checkDuration("QUEUE_MAX_AGE", cfg.QueueMaxAge),
-		checkDuration("SESSION_IDLE_TIMEOUT", cfg.SessionIdleTimeout),
+		parseDuration("MESSAGE_MAX_AGE", &cfg.MessageMaxAge),
+		parseDuration("QUEUE_MAX_AGE", &cfg.QueueMaxAge),
+		parseDuration("SESSION_IDLE_TIMEOUT", &cfg.SessionIdleTimeout),
 		parseTrustedProxies(&cfg.TrustedProxies),
 	)
 }
 
-// parseTrustedProxies sets *value to the addresses in TRUSTED_PROXIES, a
-// comma-separated list of networks such as 10.0.0.0/8 and single
-// addresses such as 192.0.2.1. The empty string trusts nothing. Viper
-// counts an empty environment variable as unset, so the environment is
-// read directly as well.
-func parseTrustedProxies(value **netipx.IPSet) error {
-	raw := viper.GetString("TRUSTED_PROXIES")
+// getString returns the setting key as a string. A number or a true/false
+// value in the config file becomes its text, as with viper.GetString. A
+// list or a map in the config file is an error, where viper.GetString
+// would return the empty string. The error leaves out the value, which
+// may be a password.
+func getString(key string) (string, error) {
+	raw, err := cast.ToStringE(viper.Get(key))
+	if err != nil {
+		return "", fmt.Errorf("%s is %w", key, errListOrMap)
+	}
 
-	fromEnv, set := os.LookupEnv("TRUSTED_PROXIES")
+	return raw, nil
+}
+
+// parseString sets *value to the setting key.
+func parseString(key string, value *string) error {
+	raw, err := getString(key)
+	if err != nil {
+		return err
+	}
+
+	*value = raw
+
+	return nil
+}
+
+// parseStringAllowEmptyEnv sets *value to the setting key, as parseString
+// does, but an environment variable set to the empty string counts as
+// set. Viper counts such a variable as unset and uses the config file or
+// the default instead.
+func parseStringAllowEmptyEnv(key string, value *string) error {
+	fromEnv, set := os.LookupEnv(key)
 	if set {
-		raw = fromEnv
+		*value = fromEnv
+
+		return nil
 	}
 
-	var builder netipx.IPSetBuilder
+	return parseString(key, value)
+}
 
-	if strings.TrimSpace(raw) != "" {
-		for entry := range strings.SplitSeq(raw, ",") {
-			err := addTrustedProxy(&builder, strings.TrimSpace(entry))
-			if err != nil {
-				return fmt.Errorf("cannot parse TRUSTED_PROXIES: %w", err)
-			}
-		}
+// parseTrustedProxies sets *value to the addresses in TRUSTED_PROXIES.
+func parseTrustedProxies(value **netipx.IPSet) error {
+	var raw string
+
+	err := parseStringAllowEmptyEnv("TRUSTED_PROXIES", &raw)
+	if err != nil {
+		return err
 	}
 
-	ipSet, err := builder.IPSet()
+	ipSet, err := ParseTrustedProxies(raw)
 	if err != nil {
 		return fmt.Errorf("cannot parse TRUSTED_PROXIES: %w", err)
 	}
@@ -215,9 +238,29 @@ func parseTrustedProxies(value **netipx.IPSet) error {
 	return nil
 }
 
+// ParseTrustedProxies returns the addresses in list, which has the form
+// of TRUSTED_PROXIES: a comma-separated list of networks such as
+// 10.0.0.0/8 and single addresses such as 192.0.2.1. The empty string
+// trusts nothing.
+func ParseTrustedProxies(list string) (*netipx.IPSet, error) {
+	var builder netipx.IPSetBuilder
+
+	if strings.TrimSpace(list) != "" {
+		for entry := range strings.SplitSeq(list, ",") {
+			err := addTrustedProxy(&builder, strings.TrimSpace(entry))
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return builder.IPSet()
+}
+
 // addTrustedProxy adds entry, a network with a slash or a single
 // address, to builder. An IPv4 address written in IPv6 form, such as
-// ::ffff:192.0.2.1, is added as IPv4.
+// ::ffff:192.0.2.1, is added as IPv4. A network in that form and an
+// address with a zone are errors, since no connection could match them.
 func addTrustedProxy(builder *netipx.IPSetBuilder, entry string) error {
 	if strings.Contains(entry, "/") {
 		prefix, err := netip.ParsePrefix(entry)
@@ -225,6 +268,12 @@ func addTrustedProxy(builder *netipx.IPSetBuilder, entry string) error {
 			return err //nolint:wrapcheck // the caller names the setting
 		}
 
+		// A connection from an IPv4 address is checked in IPv4 form.
+		if prefix.Addr().Is4In6() {
+			return fmt.Errorf("%w: %s is an IPv4 network in IPv6 form",
+				errNeverMatches, entry)
+		}
+
 		builder.AddPrefix(prefix)
 
 		return nil
@@ -235,6 +284,11 @@ func addTrustedProxy(builder *netipx.IPSetBuilder, entry string) error {
 		return err //nolint:wrapcheck // the caller names the setting
 	}
 
+	// IPSet.Contains is false for every address with a zone.
+	if addr.Zone() != "" {
+		return fmt.Errorf("%w: %s has a zone", errNeverMatches, entry)
+	}
+
 	builder.Add(addr.Unmap())
 
 	return nil
@@ -243,7 +297,10 @@ func addTrustedProxy(builder *netipx.IPSetBuilder, entry string) error {
 // parseInt sets *value to the setting key read as a whole number. It
 // returns an error when the value does not parse or is below minimum.
 func parseInt(key string, minimum int, value *int) error {
-	raw := viper.GetString(key)
+	raw, err := getString(key)
+	if err != nil {
+		return err
+	}
 
 	parsed, err := strconv.Atoi(raw)
 	if err != nil {
@@ -264,7 +321,10 @@ func parseInt(key string, minimum int, value *int) error {
 // number. It returns an error when the value does not parse or is not a
 // finite number above zero.
 func parseFloat(key string, value *float64) error {
-	raw := viper.GetString(key)
+	raw, err := getString(key)
+	if err != nil {
+		return err
+	}
 
 	parsed, err := strconv.ParseFloat(raw, 64)
 	if err != nil {
@@ -284,7 +344,12 @@ func parseFloat(key string, value *float64) error {
 
 // parseBool sets *value to the setting key read as true or false.
 func parseBool(key string, value *bool) error {
-	parsed, err := strconv.ParseBool(viper.GetString(key))
+	raw, err := getString(key)
+	if err != nil {
+		return err
+	}
+
+	parsed, err := strconv.ParseBool(raw)
 	if err != nil {
 		return fmt.Errorf("cannot parse %s: %w", key, err)
 	}
@@ -294,18 +359,25 @@ func parseBool(key string, value *bool) error {
 	return nil
 }
 
-// checkDuration returns an error naming the setting key when value is
-// not a Go duration above zero.
-func checkDuration(key, value string) error {
-	duration, err := time.ParseDuration(value)
+// parseDuration sets *value to the setting key. It returns an error when
+// the value is not a Go duration above zero.
+func parseDuration(key string, value *string) error {
+	raw, err := getString(key)
+	if err != nil {
+		return err
+	}
+
+	duration, err := time.ParseDuration(raw)
 	if err != nil {
 		return fmt.Errorf("cannot parse %s: %w", key, err)
 	}
 
 	if duration <= 0 {
 		return fmt.Errorf("%w: %s is %s, but must be above zero",
-			errOutOfRange, key, value)
+			errOutOfRange, key, raw)
 	}
 
+	*value = raw
+
 	return nil
 }

internal/config/config_test.go

@@ -3,10 +3,12 @@ package config_test
 import (
 	"net/netip"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/spf13/viper"
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/globals"
 	"sneak.berlin/go/neoirc/internal/logger"
@@ -141,8 +143,7 @@ func settingsOf(cfg *config.Config) settings {
 }
 
 func TestBadSettingStopsStartup(t *testing.T) {
-	// For each setting, the first value does not parse and the others
-	// parse but are out of range.
+	// Each value is invalid for its setting.
 	tests := []struct {
 		key    string
 		values []string
@@ -161,6 +162,7 @@ func TestBadSettingStopsStartup(t *testing.T) {
 		{key: "SESSION_IDLE_TIMEOUT", values: []string{"a month", "0", "-1m"}},
 		{key: "TRUSTED_PROXIES", values: []string{
 			"proxy.example.com", "10.0.0.0/33", "192.0.2.1:8080",
+			"::ffff:10.0.0.0/104", "fe80::1%eth0",
 		}},
 	}
 
@@ -237,21 +239,21 @@ func TestTrustedProxies(t *testing.T) {
 			set:       true,
 			value:     "198.51.100.0/24, 192.0.2.7,2001:db8::/32",
 			trusted:   []string{"198.51.100.200", "192.0.2.7", "2001:db8::5"},
-			untrusted: []string{"10.1.2.3", "192.168.1.1", "192.0.2.8"},
+			untrusted: []string{"10.4.5.6", "192.168.4.4", "192.0.2.8"},
 		},
 		{
 			name:      "a mapped IPv6 address is trusted as IPv4",
 			set:       true,
 			value:     "::ffff:192.0.2.7",
 			trusted:   []string{"192.0.2.7"},
-			untrusted: []string{"10.1.2.3"},
+			untrusted: []string{"10.7.8.9"},
 		},
 		{
 			name:      "the empty string trusts nothing",
 			set:       true,
 			value:     "",
 			trusted:   nil,
-			untrusted: []string{"10.1.2.3", "192.168.1.1", "127.0.0.1"},
+			untrusted: []string{"10.0.0.1", "192.168.0.1", "::1"},
 		},
 	}
 
@@ -284,3 +286,154 @@ func TestTrustedProxies(t *testing.T) {
 		})
 	}
 }
+
+// unsetEnv removes the environment variable key for the rest of the
+// test, so that config.New reads key from the config file.
+func unsetEnv(t *testing.T, key string) {
+	t.Helper()
+
+	// t.Setenv puts back whatever value was there after the test,
+	// including when Unsetenv removes it.
+	t.Setenv(key, "")
+
+	err := os.Unsetenv(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// writeConfigFile writes content to the config file config.New reads
+// when HOME is home, and returns the file's path.
+func writeConfigFile(t *testing.T, home, content string) string {
+	t.Helper()
+
+	// loadConfig names the app neoirc-test, so config.New reads
+	// $HOME/.config/neoirc-test/neoirc-test.yaml.
+	dir := filepath.Join(home, ".config", "neoirc-test")
+
+	err := os.MkdirAll(dir, 0o700)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	path := filepath.Join(dir, "neoirc-test.yaml")
+
+	err = os.WriteFile(path, []byte(content), 0o600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Viper keeps the file and the values it read from it after the
+	// file is gone. Reset clears them for later tests.
+	t.Cleanup(viper.Reset)
+
+	return path
+}
+
+func TestListOrMapInConfigFileStopsStartup(t *testing.T) {
+	// YAML reads the first value as a list and the second as a map.
+	values := []string{`[":6667"]`, `{addr: ":6667"}`}
+	keys := []string{"IRC_LISTEN_ADDR", "MOTD", "TRUSTED_PROXIES"}
+
+	for _, key := range keys {
+		for _, value := range values {
+			t.Run(key+"="+value, func(t *testing.T) {
+				home := t.TempDir()
+				t.Setenv("HOME", home)
+				unsetEnv(t, key)
+				writeConfigFile(t, home, key+": "+value+"\n")
+
+				_, err := loadConfig(t)
+				if err == nil || !strings.Contains(err.Error(), key) {
+					t.Errorf("error = %v, want one naming %s", err, key)
+				}
+			})
+		}
+	}
+}
+
+func TestListOrMapErrorLeavesOutValue(t *testing.T) {
+	const key = "NEOIRC_OPER_PASSWORD"
+
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	unsetEnv(t, key)
+	// YAML reads an unquoted {hunter2} as a map.
+	writeConfigFile(t, home, key+": {hunter2}\n")
+
+	_, err := loadConfig(t)
+	if err == nil || !strings.Contains(err.Error(), key) {
+		t.Fatalf("error = %v, want one naming %s", err, key)
+	}
+
+	if strings.Contains(err.Error(), "hunter2") {
+		t.Errorf("error %q shows the password", err)
+	}
+}
+
+func TestEmptyEnvironmentValueWinsOverConfigFile(t *testing.T) {
+	const (
+		ircListenAddr  = "IRC_LISTEN_ADDR"
+		trustedProxies = "TRUSTED_PROXIES"
+	)
+
+	// Each setting is the empty string in the environment and a list in
+	// the config file. The environment wins, so the list is never read.
+	tests := []struct {
+		key   string
+		empty func(cfg *config.Config) bool
+	}{
+		{
+			key: ircListenAddr,
+			empty: func(cfg *config.Config) bool {
+				return cfg.IRCListenAddr == ""
+			},
+		},
+		{
+			key: trustedProxies,
+			empty: func(cfg *config.Config) bool {
+				return len(cfg.TrustedProxies.Prefixes()) == 0
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.key, func(t *testing.T) {
+			home := t.TempDir()
+			t.Setenv("HOME", home)
+			t.Setenv(test.key, "")
+			writeConfigFile(t, home, test.key+": [\":6667\"]\n")
+
+			cfg := newConfig(t)
+			if !test.empty(cfg) {
+				t.Errorf("%s is not the empty string", test.key)
+			}
+		})
+	}
+}
+
+func TestSingleValuesInConfigFileAreUsed(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	unsetEnv(t, "PORT")
+	unsetEnv(t, "DEBUG")
+	unsetEnv(t, "MOTD")
+	writeConfigFile(t, home, "PORT: 9000\nDEBUG: true\nMOTD: hello\n")
+
+	cfg := newConfig(t)
+	if cfg.Port != 9000 || !cfg.Debug || cfg.MOTD != "hello" {
+		t.Errorf("Port, Debug, MOTD = %d, %t, %q, want 9000, true, %q",
+			cfg.Port, cfg.Debug, cfg.MOTD, "hello")
+	}
+}
+
+func TestConfigFileThatDoesNotParseStopsStartup(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	path := writeConfigFile(t, home, "MOTD: [unclosed\n")
+
+	_, err := loadConfig(t)
+	if err == nil || !strings.Contains(err.Error(), path) {
+		t.Errorf("error = %v, want one naming %s", err, path)
+	}
+}

internal/db/auth.go

@@ -22,7 +22,7 @@ func (database *Database) SetPassword(
 	password string,
 ) error {
 	hash, err := bcrypt.GenerateFromPassword(
-		[]byte(password), bcrypt.DefaultCost,
+		[]byte(password), database.passwordCost,
 	)
 	if err != nil {
 		return fmt.Errorf("hash password: %w", err)

internal/db/db.go

@@ -15,6 +15,7 @@ import (
 	"strings"
 
 	"go.uber.org/fx"
+	"golang.org/x/crypto/bcrypt"
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/logger"
 
@@ -39,13 +40,19 @@ type Params struct {
 
 	Logger *logger.Logger
 	Config *config.Config
+
+	// PasswordCost is the bcrypt cost at which SetPassword hashes
+	// a password. The server leaves it unset, which means
+	// bcrypt.DefaultCost. Tests set a lower cost to save time.
+	PasswordCost int `optional:"true"`
 }
 
 // Database manages the SQLite connection and migrations.
 type Database struct {
-	conn   *sql.DB
-	log    *slog.Logger
-	params *Params
+	conn         *sql.DB
+	log          *slog.Logger
+	params       *Params
+	passwordCost int
 }
 
 // New creates a new Database and registers lifecycle hooks.
@@ -53,9 +60,15 @@ func New(
 	lifecycle fx.Lifecycle,
 	params Params,
 ) (*Database, error) {
+	passwordCost := params.PasswordCost
+	if passwordCost == 0 {
+		passwordCost = bcrypt.DefaultCost
+	}
+
 	database := &Database{ //nolint:exhaustruct // conn set in OnStart
-		params: &params,
-		log:    params.Logger.Get(),
+		params:       &params,
+		log:          params.Logger.Get(),
+		passwordCost: passwordCost,
 	}
 
 	database.log.Info("Database instantiated")

internal/db/db_test.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"go.uber.org/fx/fxtest"
+	"golang.org/x/crypto/bcrypt"
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/db"
 	"sneak.berlin/go/neoirc/internal/dbtest"
@@ -26,7 +27,11 @@ const (
 		(SELECT 1 UNION ALL SELECT x + 1 FROM n)
 		SELECT COUNT(*) FROM n`
 
-	endlessQueryTimeout = 100 * time.Millisecond
+	// endlessQueryTimeout is how long the endless query runs
+	// before its context ends. A query whose context ends before
+	// it starts is never run, and the pool keeps its connection,
+	// so the timeout leaves a loaded host time to start it.
+	endlessQueryTimeout = 2 * time.Second
 )
 
 // TestDefaultDBURLSetsWALAndBusyTimeout opens a file database
@@ -236,6 +241,85 @@ func TestDBURLSettingForeignKeysFailsStartup(t *testing.T) {
 	}
 }
 
+// TestPasswordCost checks the bcrypt cost of the hash that SetPassword
+// stores: bcrypt.DefaultCost when db.Params leaves PasswordCost unset,
+// as the server does, and PasswordCost when it is set.
+func TestPasswordCost(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name         string
+		passwordCost int
+		wantCost     int
+	}{
+		{name: "unset", wantCost: bcrypt.DefaultCost},
+		{
+			name:         "bcrypt.MinCost",
+			passwordCost: bcrypt.MinCost,
+			wantCost:     bcrypt.MinCost,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			lifecycle := fxtest.NewLifecycle(t)
+
+			log, err := logger.New(lifecycle, logger.Params{
+				Globals: &globals.Globals{},
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			database, err := db.New(lifecycle, db.Params{
+				Logger:       log,
+				Config:       &config.Config{DBURL: dbtest.NewURL(t)},
+				PasswordCost: test.passwordCost,
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			lifecycle.RequireStart()
+			t.Cleanup(lifecycle.RequireStop)
+
+			sessionID, _, _, err := database.CreateSession(
+				t.Context(), "costuser", "", "", "",
+			)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			err = database.SetPassword(t.Context(), sessionID, "password123")
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			var hash string
+
+			err = database.GetDB().QueryRowContext(
+				t.Context(),
+				"SELECT password_hash FROM sessions WHERE id = ?",
+				sessionID,
+			).Scan(&hash)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			cost, err := bcrypt.Cost([]byte(hash))
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if cost != test.wantCost {
+				t.Errorf("cost = %d, want %d", cost, test.wantCost)
+			}
+		})
+	}
+}
+
 // startDatabase starts a Database for dbURL the way the server does.
 // It returns the error that stopped it from starting, if any.
 func startDatabase(t *testing.T, dbURL string) (*db.Database, error) {

internal/db/export_test.go

@@ -8,10 +8,12 @@ import (
 	"testing"
 	"time"
 
+	"golang.org/x/crypto/bcrypt"
 	"sneak.berlin/go/neoirc/internal/dbtest"
 )
 
-// NewTestDatabase creates an in-memory database for testing.
+// NewTestDatabase creates an in-memory database for testing. It
+// hashes passwords at bcrypt.MinCost.
 func NewTestDatabase(tb testing.TB) (*Database, error) {
 	tb.Helper()
 
@@ -23,8 +25,9 @@ func NewTestDatabase(tb testing.TB) (*Database, error) {
 	}
 
 	database := &Database{ //nolint:exhaustruct // test helper, params not needed
-		conn: conn,
-		log:  slog.Default(),
+		conn:         conn,
+		log:          slog.Default(),
+		passwordCost: bcrypt.MinCost,
 	}
 
 	err = database.runMigrations(context.Background())

internal/handlers/api_test.go

@@ -145,34 +145,46 @@ type testServer struct {
 	handlers   *handlers.Handlers
 }
 
-// viperMu makes tests start their servers one at a time,
-// because config.New writes the global viper instance and
-// the server reads it as it starts.
-//
-//nolint:gochecknoglobals // guards a global, so must be one
-var viperMu sync.Mutex
+const (
+	// maxMessageSize is MAX_MESSAGE_SIZE on every test server, the
+	// setting's default.
+	maxMessageSize = 4096
+
+	// loginRateLimit is LOGIN_RATE_LIMIT on every test server, the
+	// setting's default.
+	loginRateLimit = 1
+
+	// loginRateBurst is LOGIN_RATE_BURST on every test server, the
+	// setting's default.
+	loginRateBurst = 5
+)
 
 func newTestServer(
 	t *testing.T,
 ) *testServer {
 	t.Helper()
 
-	return newTestServerWith(t, 0, "", "")
+	return newTestServerWith(t, 0, "", "", config.DefaultTrustedProxies)
 }
 
 func newTestServerWith(
 	t *testing.T,
 	hashcashBits int,
-	operName, operPassword string,
+	operName, operPassword, trustedProxies string,
 ) *testServer {
 	t.Helper()
 
-	viperMu.Lock()
-	defer viperMu.Unlock()
-
 	dbURL := dbtest.NewURL(t)
 	copyTemplateDB(t, dbURL)
 
+	trusted, err := config.ParseTrustedProxies(trustedProxies)
+	if err != nil {
+		t.Fatalf("parse trusted proxies: %v", err)
+	}
+
+	// Each duration setting defaults to 30 days.
+	const thirtyDays = "720h"
+
 	var (
 		srv      *server.Server
 		brk      *broker.Broker
@@ -184,31 +196,25 @@ func newTestServerWith(
 		fx.Provide(
 			newTestGlobals,
 			logger.New,
-			func(
-				lifecycle fx.Lifecycle,
-				globs *globals.Globals,
-				log *logger.Logger,
-			) (*config.Config, error) {
-				cfg, err := config.New(
-					lifecycle, config.Params{ //nolint:exhaustruct
-						Globals: globs, Logger: log,
-					},
-				)
-				if err != nil {
-					return nil, fmt.Errorf(
-						"test config: %w", err,
-					)
+			// Built here rather than by config.New, which writes
+			// the global viper instance, so servers start in
+			// parallel.
+			func() *config.Config {
+				return &config.Config{
+					DBURL: dbURL,
+					// One line: each line is a database write per new session.
+					MOTD:               "neoirc test server",
+					MaxMessageSize:     maxMessageSize,
+					HashcashBits:       hashcashBits,
+					OperName:           operName,
+					OperPassword:       operPassword,
+					MessageMaxAge:      thirtyDays,
+					QueueMaxAge:        thirtyDays,
+					SessionIdleTimeout: thirtyDays,
+					LoginRateLimit:     loginRateLimit,
+					LoginRateBurst:     loginRateBurst,
+					TrustedProxies:     trusted,
 				}
-
-				cfg.DBURL = dbURL
-				cfg.Port = 0
-				// One line: each line is a database write per new session.
-				cfg.MOTD = "neoirc test server"
-				cfg.HashcashBits = hashcashBits
-				cfg.OperName = operName
-				cfg.OperPassword = operPassword
-
-				return cfg, nil
 			},
 			newTestDB,
 			broker.New,
@@ -255,7 +261,7 @@ func newTestDB(
 	cfg *config.Config,
 ) (*db.Database, error) {
 	database, err := db.New(lifecycle, db.Params{ //nolint:exhaustruct
-		Logger: log, Config: cfg,
+		Logger: log, Config: cfg, PasswordCost: bcrypt.MinCost,
 	})
 	if err != nil {
 		return nil, fmt.Errorf("test db: %w", err)
@@ -409,7 +415,7 @@ func doRequestAuth(
 		return nil, fmt.Errorf("new request: %w", err)
 	}
 
-	if body != nil {
+	if method != http.MethodGet {
 		request.Header.Set(
 			"Content-Type", "application/json",
 		)
@@ -830,10 +836,7 @@ func (tserver *testServer) postBody(
 func TestRequestBodyLimit(t *testing.T) {
 	t.Parallel()
 
-	const (
-		maxMessageSize = 4096 // the default MAX_MESSAGE_SIZE
-		nick           = "alice_bodylimit"
-	)
+	const nick = "alice_bodylimit"
 
 	endpoints := []struct {
 		name, path, value string
@@ -900,6 +903,131 @@ func TestRequestBodyLimit(t *testing.T) {
 	}
 }
 
+// requestWithType sends a request with the Content-Type contentType,
+// or none when it is empty, and returns the status and the decoded
+// JSON body.
+func (tserver *testServer) requestWithType(
+	method, path, token, contentType, body string,
+) (int, map[string]any) {
+	tserver.t.Helper()
+
+	request, err := http.NewRequestWithContext(
+		tserver.t.Context(), method, tserver.url(path),
+		strings.NewReader(body),
+	)
+	if err != nil {
+		tserver.t.Fatalf("new request: %v", err)
+	}
+
+	if contentType != "" {
+		request.Header.Set("Content-Type", contentType)
+	}
+
+	request.AddCookie(&http.Cookie{ //nolint:exhaustruct,gosec // only name+value
+		Name:  authCookieName,
+		Value: token,
+	})
+
+	resp, err := http.DefaultClient.Do(request)
+	if err != nil {
+		tserver.t.Fatalf("%s %s: %v", method, path, err)
+	}
+
+	defer func() { _ = resp.Body.Close() }()
+
+	var result map[string]any
+
+	_ = json.NewDecoder(resp.Body).Decode(&result)
+
+	return resp.StatusCode, result
+}
+
+// TestRequireJSONContentType checks that a POST whose Content-Type is
+// not application/json gets 415 and changes nothing: the message is
+// not stored and the client is not logged out.
+func TestRequireJSONContentType(t *testing.T) {
+	t.Parallel()
+
+	tserver := newTestServer(t)
+	token := tserver.createSession("alice_ctype")
+
+	tserver.sendCommand(token, map[string]any{
+		commandKey: joinCmd, toKey: "#ctype",
+	})
+
+	status, _ := tserver.requestWithType(
+		http.MethodGet, apiState, token, "text/plain", "",
+	)
+	if status != http.StatusOK {
+		t.Errorf("GET with text/plain: expected 200, got %d", status)
+	}
+
+	tests := []struct {
+		name, contentType string
+		want              int
+	}{
+		{"text", "text/plain", http.StatusUnsupportedMediaType},
+		{
+			"form", "application/x-www-form-urlencoded",
+			http.StatusUnsupportedMediaType,
+		},
+		{
+			"multipart", "multipart/form-data; boundary=x",
+			http.StatusUnsupportedMediaType,
+		},
+		{"missing", "", http.StatusUnsupportedMediaType},
+		{"json", "application/json", http.StatusOK},
+		{"json with charset", "application/json; charset=utf-8", http.StatusOK},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			status, result := tserver.requestWithType(
+				http.MethodPost, apiMessages, token, test.contentType,
+				`{"command":"PRIVMSG","to":"#ctype","body":["`+test.name+`"]}`,
+			)
+			if status != test.want {
+				t.Fatalf("send: expected %d, got %d: %v", test.want, status, result)
+			}
+
+			if status == http.StatusUnsupportedMediaType &&
+				result["error"] != "content type must be application/json" {
+				t.Errorf("send: unexpected error body %v", result)
+			}
+
+			msgs, _ := tserver.pollMessages(token, 0)
+
+			stored := slices.ContainsFunc(msgs, func(msg map[string]any) bool {
+				body, _ := msg[bodyKey].([]any)
+
+				return msg[commandKey] == privmsgCmd &&
+					slices.Contains(body, any(test.name))
+			})
+			if stored != (test.want == http.StatusOK) {
+				t.Errorf("message stored: %v, want %v", stored, !stored)
+			}
+
+			if test.want == http.StatusOK {
+				return
+			}
+
+			status, _ = tserver.requestWithType(
+				http.MethodPost, apiLogout, token, test.contentType, "",
+			)
+			if status != http.StatusUnsupportedMediaType {
+				t.Errorf("logout: expected 415, got %d", status)
+			}
+
+			status, _ = tserver.getState(token)
+			if status != http.StatusOK {
+				t.Errorf("state after refused logout: expected 200, got %d", status)
+			}
+		})
+	}
+}
+
 func TestAuthNoCookie(t *testing.T) {
 	t.Parallel()
 
@@ -1750,52 +1878,67 @@ func TestConcurrentQuitsSendOneQuit(t *testing.T) {
 // that the second session then holds one QUIT from the
 // first, and that the first session is deleted: its tokens
 // are refused and its nick is free. It does all this
-// quitRaceTrials times, each on a new server, because each
-// trial logs in and logins are rate limited.
+// quitRaceTrials times, at once, each on a new server, because
+// each trial logs in and logins are rate limited.
 func checkQuitRace(
 	t *testing.T,
 	leave func(tserver *testServer, tokens []string),
 ) {
 	t.Helper()
 
+	for trial := range quitRaceTrials {
+		t.Run(fmt.Sprintf("trial %d", trial), func(t *testing.T) {
+			t.Parallel()
+
+			checkQuitRaceOnce(t, newTestServer(t), leave)
+		})
+	}
+}
+
+// checkQuitRaceOnce runs one trial of checkQuitRace on
+// tserver.
+func checkQuitRaceOnce(
+	t *testing.T,
+	tserver *testServer,
+	leave func(tserver *testServer, tokens []string),
+) {
+	t.Helper()
+
 	const nick = "racingquitter"
 
-	for trial := range quitRaceTrials {
-		tserver := newTestServer(t)
-		firstToken := tserver.createSession(nick)
-		observerToken := tserver.createSession("raceobserver")
+	firstToken := tserver.createSession(nick)
+	observerToken := tserver.createSession("raceobserver")
 
-		tserver.setPassword(nick)
+	tserver.setPassword(nick)
 
-		tokens := []string{firstToken, tserver.login(nick)}
+	tokens := []string{firstToken, tserver.login(nick)}
 
-		for _, token := range []string{firstToken, observerToken} {
-			tserver.sendCommand(token, map[string]any{
-				commandKey: joinCmd, toKey: "#quitrace",
-			})
-		}
-
-		_, lastID := tserver.pollMessages(observerToken, 0)
-
-		leave(tserver, tokens)
-
-		msgs, _ := tserver.pollMessages(observerToken, lastID)
-
-		quits := countQuits(msgs, nick)
-		if quits != 1 {
-			t.Errorf("trial %d: %d QUITs, want 1: %v", trial, quits, msgs)
-		}
-
-		for _, token := range tokens {
-			status, _ := tserver.getState(token)
-			if status != http.StatusUnauthorized {
-				t.Errorf("trial %d: state got %d, want 401", trial, status)
-			}
-		}
-
-		// createSession fails the test if the nick is taken.
-		tserver.createSession(nick)
+	for _, token := range []string{firstToken, observerToken} {
+		tserver.sendCommand(token, map[string]any{
+			commandKey: joinCmd, toKey: "#quitrace",
+		})
 	}
+
+	_, lastID := tserver.pollMessages(observerToken, 0)
+
+	leave(tserver, tokens)
+
+	msgs, _ := tserver.pollMessages(observerToken, lastID)
+
+	quits := countQuits(msgs, nick)
+	if quits != 1 {
+		t.Errorf("%d QUITs, want 1: %v", quits, msgs)
+	}
+
+	for _, token := range tokens {
+		status, _ := tserver.getState(token)
+		if status != http.StatusUnauthorized {
+			t.Errorf("state got %d, want 401", status)
+		}
+	}
+
+	// createSession fails the test if the nick is taken.
+	tserver.createSession(nick)
 }
 
 // TestLogoutOfOneClientKeepsSession checks that when one of
@@ -1933,11 +2076,28 @@ const (
 	// return once the session has left.
 	quitWakeDeadline = 5 * time.Second
 
-	// pollWaitStep is how often checkQuitWakesPoll checks
+	// pollWaitStep is how often waitForLongPoll checks
 	// whether the long poll is waiting yet.
 	pollWaitStep = 10 * time.Millisecond
 )
 
+// waitForLongPoll waits until a long poll of the session
+// sessionID is waiting, and fails the test if none is within
+// quitWakeDeadline.
+func (tserver *testServer) waitForLongPoll(sessionID int64) {
+	tserver.t.Helper()
+
+	deadline := time.Now().Add(quitWakeDeadline)
+
+	for tserver.broker.ListenerCount(sessionID) == 0 {
+		if time.Now().After(deadline) {
+			tserver.t.Fatal("the long poll did not start waiting")
+		}
+
+		time.Sleep(pollWaitStep)
+	}
+}
+
 // TestQuitWakesPeerLongPoll checks that a session's QUIT
 // wakes the long poll of a user who shares a channel with
 // it.
@@ -2012,15 +2172,7 @@ func checkQuitWakesPoll(
 		msgs, pollErr = tserver.longPoll(peerToken, lastID, quitWakePollTimeout)
 	}()
 
-	deadline := time.Now().Add(quitWakeDeadline)
-
-	for tserver.broker.ListenerCount(peerID) == 0 {
-		if time.Now().After(deadline) {
-			t.Fatal("the long poll did not start waiting")
-		}
-
-		time.Sleep(pollWaitStep)
-	}
+	tserver.waitForLongPoll(peerID)
 
 	leave(tserver, token)
 
@@ -2850,7 +3002,12 @@ func TestLongPoll(t *testing.T) {
 		pollMsgs = result.Messages
 	}()
 
-	time.Sleep(200 * time.Millisecond)
+	bobID, err := tserver.database.GetSessionByNick(t.Context(), "lp_bob")
+	if err != nil {
+		t.Fatalf("get session of lp_bob: %v", err)
+	}
+
+	tserver.waitForLongPoll(bobID)
 
 	tserver.sendCommand(aliceToken, map[string]any{
 		commandKey: privmsgCmd,
@@ -3009,18 +3166,18 @@ func TestGetMessagesRemovesWaitChannel(t *testing.T) {
 		longTimeout = 10
 
 		// shortTimeout, in seconds, is the timeout of the
-		// requests that wait it out.
+		// request that waits it out.
 		shortTimeout = 1
 	)
 
 	// queued is whether a message is queued before the request,
-	// whose timeout is in seconds. failingRead is as for
-	// getMessagesFailingRead. wantReads is how many times the
-	// handler reads the queue: once if it answers at once,
+	// whose timeout is in seconds. failingRead and notified are
+	// as for getMessagesFailingRead. wantReads is how many times
+	// the handler reads the queue: once if it answers at once,
 	// twice if it waits first.
 	tests := []struct {
 		name                  string
-		queued                bool
+		queued, notified      bool
 		timeout, failingRead  int
 		wantReads, wantStatus int
 	}{
@@ -3041,9 +3198,9 @@ func TestGetMessagesRemovesWaitChannel(t *testing.T) {
 			wantReads: 1, wantStatus: http.StatusInternalServerError,
 		},
 		{
-			name: "read after the wait failed", timeout: shortTimeout,
-			failingRead: 2, wantReads: 2,
-			wantStatus: http.StatusInternalServerError,
+			name: "read after the wait failed", notified: true,
+			timeout: handlers.MaxLongPollTimeout, failingRead: 2,
+			wantReads: 2, wantStatus: http.StatusInternalServerError,
 		},
 	}
 
@@ -3075,7 +3232,7 @@ func TestGetMessagesRemovesWaitChannel(t *testing.T) {
 			}
 
 			status, reads := tserver.getMessagesFailingRead(
-				token, lastID, tc.timeout, tc.failingRead,
+				token, sessionID, lastID, tc.timeout, tc.failingRead, tc.notified,
 			)
 			if status != tc.wantStatus {
 				t.Errorf("status %d, want %d", status, tc.wantStatus)
@@ -3092,14 +3249,17 @@ func TestGetMessagesRemovesWaitChannel(t *testing.T) {
 }
 
 // getMessagesFailingRead sends GET /api/v1/messages for the
-// client token with timeout and after afterID. The handler's
-// read of the queue numbered failingRead, counting from 1,
-// fails; with 0, none does. It returns the response status
-// and how many times the handler read the queue.
+// client token of the session sessionID, with timeout and
+// after afterID. The handler's read of the queue numbered
+// failingRead, counting from 1, fails; with 0, none does.
+// With notified, it notifies the broker once the request
+// waits. It returns the response status and how many times
+// the handler read the queue.
 func (tserver *testServer) getMessagesFailingRead(
 	token string,
-	afterID int64,
+	sessionID, afterID int64,
 	timeout, failingRead int,
+	notified bool,
 ) (int, int) {
 	tserver.t.Helper()
 
@@ -3121,20 +3281,45 @@ func (tserver *testServer) getMessagesFailingRead(
 		)
 	})
 
-	resp, err := doRequestAuth(
-		tserver.t, http.MethodGet,
-		tserver.url(fmt.Sprintf(
-			"%s?timeout=%d&after=%d", apiMessages, timeout, afterID,
-		)),
-		token, nil,
+	var (
+		status int
+		err    error
 	)
+
+	answered := make(chan struct{})
+
+	go func() {
+		defer close(answered)
+
+		var resp *http.Response
+
+		resp, err = doRequestAuth(
+			tserver.t, http.MethodGet,
+			tserver.url(fmt.Sprintf(
+				"%s?timeout=%d&after=%d", apiMessages, timeout, afterID,
+			)),
+			token, nil,
+		)
+		if err != nil {
+			return
+		}
+
+		status = resp.StatusCode
+		_ = resp.Body.Close()
+	}()
+
+	if notified {
+		tserver.waitForLongPoll(sessionID)
+		tserver.broker.Notify(sessionID)
+	}
+
+	<-answered
+
 	if err != nil {
 		tserver.t.Fatalf("get messages: %v", err)
 	}
 
-	_ = resp.Body.Close()
-
-	return resp.StatusCode, reads
+	return status, reads
 }
 
 // TestLongPollRemovesWaitChannelWhenClientGivesUp checks that
@@ -4295,7 +4480,7 @@ func TestLoginRateLimitIgnoresForwardedHeaders(t *testing.T) {
 	}
 
 	loginBody, err := json.Marshal(map[string]string{
-		nickKey: "nosuchuser", passwordKey: "doesnotmatter",
+		nickKey: "unknownnick", passwordKey: "wrongpassword",
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -4342,6 +4527,55 @@ func TestLoginRateLimitIgnoresForwardedHeaders(t *testing.T) {
 	}
 }
 
+func TestLoginRateLimitPerClientBehindTrustedProxy(t *testing.T) {
+	t.Parallel()
+
+	// The test client connects from 127.0.0.1. Trusted as a proxy, it
+	// passes each client's address in X-Forwarded-For.
+	tserver := newTestServerWith(t, 0, "", "", "127.0.0.1")
+
+	// An empty JSON object is refused after the rate limit counts the
+	// attempt, so no attempt checks a password or looks up a hostname.
+	loginFrom := func(forwardedFor string) int {
+		t.Helper()
+
+		request, err := http.NewRequestWithContext(
+			t.Context(), http.MethodPost,
+			tserver.url("/api/v1/login"), strings.NewReader("{}"),
+		)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		request.Header.Set("Content-Type", "application/json")
+		request.Header.Set("X-Forwarded-For", forwardedFor)
+
+		resp, err := http.DefaultClient.Do(request)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		_ = resp.Body.Close()
+
+		return resp.StatusCode
+	}
+
+	// The default burst is 5 attempts per address.
+	for range 5 {
+		loginFrom("203.0.113.1")
+	}
+
+	status := loginFrom("203.0.113.1")
+	if status != http.StatusTooManyRequests {
+		t.Errorf("sixth attempt from 203.0.113.1 got %d, want 429", status)
+	}
+
+	status = loginFrom("203.0.113.2")
+	if status == http.StatusTooManyRequests {
+		t.Error("first attempt from 203.0.113.2 got 429")
+	}
+}
+
 func TestLoginRateLimitAllowsNormalUse(t *testing.T) {
 	t.Parallel()
 
@@ -5029,7 +5263,9 @@ func TestRefusedSessionLeavesStampUnspent(t *testing.T) {
 		badNick = "bad nick"
 	)
 
-	tserver := newTestServerWith(t, bits, "", "")
+	tserver := newTestServerWith(
+		t, bits, "", "", config.DefaultTrustedProxies,
+	)
 
 	// A server with no SERVER_NAME takes stamps for "neoirc".
 	status := postSessionWithStamp(
@@ -5235,6 +5471,7 @@ func newTestServerWithOper(
 
 	return newTestServerWith(
 		t, 0, testOperName, testOperPassword,
+		config.DefaultTrustedProxies,
 	)
 }
 

internal/handlers/export_test.go

@@ -6,6 +6,10 @@ import (
 	"sneak.berlin/go/neoirc/internal/db"
 )
 
+// MaxLongPollTimeout is the longest HandleGetMessages waits, in
+// seconds.
+const MaxLongPollTimeout = maxLongPollTimeout
+
 // SetPollMessages makes HandleGetMessages read the client
 // output queue with poll in place of Database.PollMessages.
 func (hdlr *Handlers) SetPollMessages(

internal/ircserver/conn.go

@@ -70,6 +70,10 @@ type Conn struct {
 	closed      bool
 	killed      bool
 
+	// pollInterval is how often the relay checks the client
+	// output queue when no broker notification arrives.
+	pollInterval time.Duration
+
 	// quitReason is the reason in the QUIT that peers are
 	// sent when the connection ends. The client's QUIT
 	// replaces it.
@@ -83,6 +87,7 @@ func newConn(
 	brk *broker.Broker,
 	cfg *config.Config,
 	svc *service.Service,
+	poll time.Duration,
 ) *Conn {
 	host, _, _ := net.SplitHostPort(tcpConn.RemoteAddr().String())
 
@@ -101,6 +106,8 @@ func newConn(
 		serverSfx:  srvName,
 		remoteIP:   host,
 		quitReason: "Connection closed",
+
+		pollInterval: poll,
 	}
 
 	conn.commands = conn.buildCommandMap()

internal/ircserver/export_test.go

@@ -14,16 +14,16 @@ import (
 )
 
 // NewTestServer creates a Server suitable for testing, whose
-// connections use interval and deadline in place of
-// pingInterval and pongDeadline, and resolve in place of
-// resolveHost.
+// connections use interval, deadline and poll in place of
+// pingInterval, pongDeadline and pollInterval, and resolve in
+// place of resolveHost.
 // The caller must call Stop() when finished.
 func NewTestServer(
 	log *slog.Logger,
 	cfg *config.Config,
 	database *db.Database,
 	brk *broker.Broker,
-	interval, deadline time.Duration,
+	interval, deadline, poll time.Duration,
 	resolve func(ctx context.Context, addr string) string,
 ) *Server {
 	globs := &globals.Globals{
@@ -46,10 +46,18 @@ func NewTestServer(
 
 		pingInterval: interval,
 		pongDeadline: deadline,
+		pollInterval: poll,
+		stopTimeout:  stopTimeout,
 		resolveHost:  resolve,
 	}
 }
 
+// SetStopTimeout makes Stop wait at most timeout for the
+// connections' cleanup.
+func (s *Server) SetStopTimeout(timeout time.Duration) {
+	s.stopTimeout = timeout
+}
+
 // ResolveHost is the reverse DNS lookup that a server made by
 // New does for each client.
 func ResolveHost(ctx context.Context, addr string) string {
@@ -99,10 +107,6 @@ const PingInterval = pingInterval
 // for a line before it closes the connection.
 const PongDeadline = pongDeadline
 
-// StopTimeout is the longest Stop waits for the connections'
-// cleanup.
-const StopTimeout = stopTimeout
-
 // NewTestConn returns a Conn for nick on tcpConn, without a
 // server, database or service behind it.
 func NewTestConn(
@@ -111,7 +115,7 @@ func NewTestConn(
 	tcpConn net.Conn,
 	nick string,
 ) *Conn {
-	conn := newConn(tcpConn, log, nil, nil, cfg, nil)
+	conn := newConn(tcpConn, log, nil, nil, cfg, nil, pollInterval)
 	conn.nick = nick
 
 	return conn

internal/ircserver/integration_test.go

@@ -3,7 +3,6 @@ package ircserver_test
 import (
 	"strings"
 	"testing"
-	"time"
 
 	"sneak.berlin/go/neoirc/internal/config"
 )
@@ -1508,9 +1507,6 @@ func TestIntegrationThirdClientObserver(t *testing.T) {
 	bob.joinAndDrain("#trio")
 	carol.joinAndDrain("#trio")
 
-	// Drain join notifications.
-	time.Sleep(100 * time.Millisecond)
-
 	// alice sends; both bob and carol should receive.
 	alice.send("PRIVMSG #trio :hello trio")
 

internal/ircserver/relay.go

@@ -17,7 +17,7 @@ import (
 func (c *Conn) relayMessages(ctx context.Context) {
 	// Use a ticker as a fallback; primary wakeup is via
 	// broker notification.
-	ticker := time.NewTicker(pollInterval)
+	ticker := time.NewTicker(c.pollInterval)
 	defer ticker.Stop()
 
 	for {

internal/ircserver/relay_test.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"golang.org/x/crypto/bcrypt"
+	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/dbtest"
 	"sneak.berlin/go/neoirc/internal/ircserver"
 	"sneak.berlin/go/neoirc/internal/service"
@@ -58,7 +59,11 @@ func (env *testEnv) queueMessage(
 func TestRelayKeepsOneWaitChannel(t *testing.T) {
 	t.Parallel()
 
-	env := newTestEnv(t)
+	env := newTestEnvWithResolver(
+		t, &config.Config{ServerName: testServerName},
+		ircserver.PingInterval, ircserver.PongDeadline,
+		ircserver.PollInterval, ircserver.ResolveHost,
+	)
 
 	client := env.dial(t)
 	client.register("idle")
@@ -119,6 +124,63 @@ func (env *testEnv) checkOneWaitChannel(
 	}
 }
 
+// TestRelayDeliversAfterFailedRead checks that when the relay
+// cannot read the client output queue, it waits for the next
+// notification, and delivers once the queue can be read again.
+func TestRelayDeliversAfterFailedRead(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	client := env.dial(t)
+	client.register("reader")
+
+	sessionID, err := env.database.GetSessionByNick(t.Context(), "reader")
+	if err != nil {
+		t.Fatalf("get session of reader: %v", err)
+	}
+
+	dbtest.Exec(t, env.dbURL,
+		"ALTER TABLE client_queues RENAME TO hidden_queues")
+
+	// Each pass of the relay takes a wait channel and then reads
+	// the queue. Once it holds a channel after the second
+	// notification, the read after the first one has failed.
+	for range 2 {
+		env.waitForWaitChannel(t, sessionID)
+		env.brk.Notify(sessionID)
+	}
+
+	env.waitForWaitChannel(t, sessionID)
+
+	dbtest.Exec(t, env.dbURL,
+		"ALTER TABLE hidden_queues RENAME TO client_queues")
+
+	env.queueMessage(
+		t, "reader", "PRIVMSG", "carol", "reader", []string{"readable"},
+	)
+
+	client.readUntil(func(l string) bool {
+		return strings.Contains(l, "readable")
+	})
+}
+
+// waitForWaitChannel waits until the session sessionID holds a
+// broker wait channel, and fails the test if it does not
+// within testTimeout.
+func (env *testEnv) waitForWaitChannel(t *testing.T, sessionID int64) {
+	t.Helper()
+
+	deadline := time.Now().Add(testTimeout)
+
+	for env.brk.ListenerCount(sessionID) == 0 {
+		if time.Now().After(deadline) {
+			t.Fatal("the relay is not waiting for a notification")
+		}
+
+		time.Sleep(relayCheckStep)
+	}
+}
+
 // TestRelayMultiLineBody checks that each line of a PRIVMSG
 // or NOTICE body sent over the HTTP API reaches an IRC
 // listener user as its own line.

internal/ircserver/server.go

@@ -53,6 +53,11 @@ type Server struct {
 	pingInterval time.Duration
 	pongDeadline time.Duration
 
+	// pollInterval and stopTimeout are the constants of the
+	// same names, except in tests, which change them.
+	pollInterval time.Duration
+	stopTimeout  time.Duration
+
 	// resolveHost is the function of the same name, except in
 	// tests, which replace it with one that blocks.
 	resolveHost func(ctx context.Context, addr string) string
@@ -79,6 +84,8 @@ func New(
 
 		pingInterval: pingInterval,
 		pongDeadline: pongDeadline,
+		pollInterval: pollInterval,
+		stopTimeout:  stopTimeout,
 		resolveHost:  resolveHost,
 	}
 
@@ -154,10 +161,10 @@ func (s *Server) stop() {
 
 	select {
 	case <-done:
-	case <-time.After(stopTimeout):
+	case <-time.After(s.stopTimeout):
 		s.log.Error(
 			"irc connections not cleaned up before stop timeout",
-			"timeout", stopTimeout,
+			"timeout", s.stopTimeout,
 		)
 	}
 }
@@ -181,7 +188,7 @@ func (s *Server) acceptLoop(ctx context.Context) {
 
 		client := newConn(
 			tcpConn, s.log,
-			s.database, s.brk, s.cfg, s.svc,
+			s.database, s.brk, s.cfg, s.svc, s.pollInterval,
 		)
 
 		s.mu.Lock()

internal/ircserver/server_test.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"go.uber.org/fx/fxtest"
+	"golang.org/x/crypto/bcrypt"
 	"sneak.berlin/go/neoirc/internal/broker"
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/db"
@@ -30,7 +31,16 @@ import (
 	_ "modernc.org/sqlite"
 )
 
-const testTimeout = 5 * time.Second
+// testTimeout is how long a test waits for something before it
+// fails. A passing test never waits this long, so it is generous
+// enough for a heavily loaded host.
+const testTimeout = 30 * time.Second
+
+// testPollInterval is how often the relay of a test server
+// checks the client output queue without a broker
+// notification. It is so long that the relay delivers only on
+// notification, and a test fails when one is missing.
+const testPollInterval = time.Hour
 
 // testEnv holds the shared test infrastructure.
 type testEnv struct {
@@ -91,16 +101,19 @@ func newTestEnvWithPingTimes(
 	t.Helper()
 
 	return newTestEnvWithResolver(
-		t, cfg, interval, deadline, ircserver.ResolveHost,
+		t, cfg, interval, deadline, testPollInterval,
+		ircserver.ResolveHost,
 	)
 }
 
 // newTestEnvWithResolver is newTestEnvWithPingTimes, except
-// that the server looks up a client's hostname with resolve.
+// that the relay checks the client output queue every poll
+// without a broker notification, and the server looks up a
+// client's hostname with resolve.
 func newTestEnvWithResolver(
 	t *testing.T,
 	cfg *config.Config,
-	interval, deadline time.Duration,
+	interval, deadline, poll time.Duration,
 	resolve func(ctx context.Context, addr string) string,
 ) *testEnv {
 	t.Helper()
@@ -116,8 +129,9 @@ func newTestEnvWithResolver(
 	}
 
 	database, err := db.New(lifecycle, db.Params{
-		Logger: dbLog,
-		Config: &config.Config{DBURL: dbURL},
+		Logger:       dbLog,
+		Config:       &config.Config{DBURL: dbURL},
+		PasswordCost: bcrypt.MinCost,
 	})
 	if err != nil {
 		t.Fatalf("new database: %v", err)
@@ -134,7 +148,7 @@ func newTestEnvWithResolver(
 	))
 
 	srv := ircserver.NewTestServer(
-		log, cfg, database, brk, interval, deadline, resolve,
+		log, cfg, database, brk, interval, deadline, poll, resolve,
 	)
 
 	// Port 0 makes the system pick a free port. dial reads it
@@ -430,7 +444,8 @@ func TestRegistrationWhileAnotherLookupIsPending(t *testing.T) {
 
 	env := newTestEnvWithResolver(
 		t, &config.Config{ServerName: testServerName},
-		ircserver.PingInterval, ircserver.PongDeadline, resolve,
+		ircserver.PingInterval, ircserver.PongDeadline,
+		testPollInterval, resolve,
 	)
 
 	env.dial(t)
@@ -553,27 +568,49 @@ func TestQuietClientAnsweringPingStaysConnected(t *testing.T) {
 func TestQuietClientNotAnsweringPingIsClosed(t *testing.T) {
 	t.Parallel()
 
-	// latest leaves room for a loaded host, but is sooner than
-	// a read deadline of two ping intervals would close it.
+	// A read deadline of two ping intervals would close the
+	// connection a second after latest. The ping interval is
+	// longer than testPingInterval, so that the time between
+	// the expected close and latest leaves room for a loaded
+	// host.
 	const (
-		earliest = testPingInterval + testPongDeadline
-		latest   = 2 * testPingInterval
+		interval = 4 * time.Second
+		earliest = interval + testPongDeadline
+		latest   = 2*interval - time.Second
 	)
 
-	env := newTestEnvWithShortPings(t)
+	env := newTestEnvWithPingTimes(
+		t,
+		&config.Config{ServerName: testServerName},
+		interval, testPongDeadline,
+	)
 	client := env.dial(t)
 
 	lastSent := time.Now()
 
 	client.register("silent")
-	client.readServerPing(lastSent)
+
+	// The server starts both waits once it has handled the
+	// registration, so the time registration took does not
+	// count against latest.
+	registered := time.Now()
+
+	client.readUntil(isServerPing)
 	client.readUntilClosed()
 
 	waited := time.Since(lastSent)
-	if waited < earliest || waited >= latest {
+	if waited < earliest {
 		t.Errorf(
-			"closed %v after the client's last line, want %v to %v",
-			waited, earliest, latest,
+			"closed %v after the client's last line, want at least %v",
+			waited, earliest,
+		)
+	}
+
+	sinceRegistered := time.Since(registered)
+	if sinceRegistered >= latest {
+		t.Errorf(
+			"closed %v after registration, want less than %v",
+			sinceRegistered, latest,
 		)
 	}
 }
@@ -1039,12 +1076,16 @@ func TestStopEndsSessions(t *testing.T) {
 }
 
 // TestStopReturnsWhileCleanupIsStuck checks that Stop stops
-// waiting for a connection's cleanup after StopTimeout, so a
-// cleanup that cannot finish does not hold up stopping.
+// waiting for a connection's cleanup after its stop timeout,
+// so a cleanup that cannot finish does not hold up stopping.
 func TestStopReturnsWhileCleanupIsStuck(t *testing.T) {
 	t.Parallel()
 
+	const stopTimeout = 100 * time.Millisecond
+
 	env := newTestEnv(t)
+	env.srv.SetStopTimeout(stopTimeout)
+
 	client := env.dial(t)
 
 	client.register("stuck")
@@ -1070,7 +1111,7 @@ func TestStopReturnsWhileCleanupIsStuck(t *testing.T) {
 
 	select {
 	case <-stopped:
-	case <-time.After(ircserver.StopTimeout + testTimeout):
+	case <-time.After(stopTimeout + testTimeout):
 		t.Error("Stop did not return while a cleanup was stuck")
 	}
 
@@ -1122,9 +1163,6 @@ func TestDirectMessage(t *testing.T) {
 	receiver := env.dial(t)
 	receiver.register("dmreceiver")
 
-	// Give relay goroutines time to start.
-	time.Sleep(100 * time.Millisecond)
-
 	sender.send("PRIVMSG dmreceiver :hello privately")
 
 	lines := receiver.readUntil(func(line string) bool {

internal/middleware/middleware.go

@@ -3,9 +3,11 @@ package middleware
 
 import (
 	"log/slog"
+	"mime"
 	"net"
 	"net/http"
 	"net/netip"
+	"slices"
 	"strings"
 	"time"
 
@@ -119,11 +121,10 @@ func clientAddr(
 		return realIP.Unmap()
 	}
 
-	entries := strings.Split(forwarded, ",")
 	client := peer
 
-	for i := len(entries) - 1; i >= 0; i-- {
-		addr, err := netip.ParseAddr(strings.TrimSpace(entries[i]))
+	for _, entry := range slices.Backward(strings.Split(forwarded, ",")) {
+		addr, err := netip.ParseAddr(strings.TrimSpace(entry))
 		if err != nil {
 			return peer
 		}
@@ -200,28 +201,74 @@ func (mware *Middleware) Logging() func(http.Handler) http.Handler {
 	}
 }
 
-// CORS returns middleware that handles Cross-Origin Resource Sharing.
-// AllowCredentials is true so browsers include cookies in
-// cross-origin API requests.
+// CORS returns middleware that lets a page on any origin read the
+// response. Use it only on public, read-only routes.
 func (mware *Middleware) CORS() func(http.Handler) http.Handler {
 	return cors.Handler(cors.Options{ //nolint:exhaustruct // optional fields
-		AllowOriginFunc: func(
-			_ *http.Request, _ string,
-		) bool {
-			return true
-		},
+		AllowedOrigins: []string{"*"},
 		AllowedMethods: []string{
 			"GET", "POST", "PUT", "DELETE", "OPTIONS",
 		},
 		AllowedHeaders: []string{
-			"Accept", "Content-Type", "X-CSRF-Token",
+			"Accept", "Authorization", "Content-Type", "X-CSRF-Token",
 		},
 		ExposedHeaders:   []string{"Link"},
-		AllowCredentials: true,
+		AllowCredentials: false,
 		MaxAge:           corsMaxAge,
 	})
 }
 
+// notJSONError is the body of the 415 answer, in the API's usual
+// error format.
+const notJSONError = `{"error":"content type must be application/json"}` + "\n"
+
+// needsJSON reports whether a request with method must have the
+// Content-Type application/json, whether or not it has a body.
+func needsJSON(method string) bool {
+	return method == http.MethodPost ||
+		method == http.MethodPut ||
+		method == http.MethodDelete
+}
+
+// isJSON reports whether the request's Content-Type is
+// application/json, with or without parameters such as charset.
+func isJSON(request *http.Request) bool {
+	mediaType, _, err := mime.ParseMediaType(
+		request.Header.Get("Content-Type"),
+	)
+
+	return err == nil && mediaType == "application/json"
+}
+
+// RequireJSON returns middleware that answers 415 to a POST, PUT or
+// DELETE request whose Content-Type is not application/json, or that
+// has none. A browser sends a request with another type, such as
+// text/plain, to another origin of the same site without asking the
+// server first, and attaches the auth cookie. Refusing those types
+// stops a page on that origin from acting as the signed-in user.
+func (mware *Middleware) RequireJSON() func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(
+			func(
+				writer http.ResponseWriter,
+				request *http.Request,
+			) {
+				if needsJSON(request.Method) && !isJSON(request) {
+					writer.Header().Set(
+						"Content-Type",
+						"application/json; charset=utf-8",
+					)
+					writer.WriteHeader(http.StatusUnsupportedMediaType)
+					_, _ = writer.Write([]byte(notJSONError))
+
+					return
+				}
+
+				next.ServeHTTP(writer, request)
+			})
+	}
+}
+
 // Metrics returns middleware that records HTTP metrics.
 func (mware *Middleware) Metrics() func(http.Handler) http.Handler {
 	metricsMiddleware := ghmm.New(ghmm.Config{ //nolint:exhaustruct // optional fields

internal/middleware/middleware_test.go

@@ -14,111 +14,122 @@ import (
 	"sneak.berlin/go/neoirc/internal/middleware"
 )
 
-func TestClientIP(t *testing.T) {
-	t.Parallel()
+// The tests trust 10.0.0.0/8. Clients use the documentation ranges
+// 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24.
+const (
+	trustedNetwork = "10.0.0.0/8"
+	proxyPeer      = "10.0.0.1:4000"
+	directPeer     = "192.0.2.1:4000"
+	client         = "203.0.113.7"
+	clientWithPort = "203.0.113.7:4000"
+	realIPClient   = "203.0.113.8"
+)
 
-	// The proxies are in 10.0.0.0/8. Clients use the documentation
-	// ranges 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24.
-	tests := []struct {
-		name       string
-		remoteAddr string
-		forwarded  []string
-		realIP     string
-		want       string
-	}{
+type clientIPTest struct {
+	name       string
+	remoteAddr string
+	forwarded  []string
+	realIP     string
+	want       string
+}
+
+func clientIPTests() []clientIPTest {
+	return []clientIPTest{
 		{
 			name:       "untrusted peer ignores forged headers",
-			remoteAddr: "192.0.2.1:4000",
-			forwarded:  []string{"203.0.113.7"},
-			realIP:     "203.0.113.8",
-			want:       "192.0.2.1:4000",
-		},
-		{
-			name:       "trusted peer without headers",
-			remoteAddr: "10.0.0.1:4000",
-			want:       "10.0.0.1:4000",
+			remoteAddr: directPeer,
+			forwarded:  []string{client},
+			realIP:     realIPClient,
+			want:       directPeer,
 		},
+		{name: "trusted peer without headers", remoteAddr: proxyPeer, want: proxyPeer},
 		{
 			name:       "trusted peer gives rightmost untrusted entry",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			forwarded:  []string{"198.51.100.9, 203.0.113.7, 10.0.0.2"},
-			want:       "203.0.113.7:4000",
+			want:       clientWithPort,
 		},
 		{
 			name:       "entries split over several headers",
-			remoteAddr: "10.0.0.1:4000",
-			forwarded:  []string{"198.51.100.9", "203.0.113.7", "10.0.0.2"},
-			want:       "203.0.113.7:4000",
+			remoteAddr: proxyPeer,
+			forwarded:  []string{"198.51.100.9", client, "10.0.0.2"},
+			want:       clientWithPort,
 		},
 		{
 			name:       "all-trusted chain gives leftmost entry",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			forwarded:  []string{"10.0.0.3, 10.0.0.2"},
 			want:       "10.0.0.3:4000",
 		},
 		{
 			name:       "X-Real-IP without X-Forwarded-For",
-			remoteAddr: "10.0.0.1:4000",
-			realIP:     "203.0.113.8",
+			remoteAddr: proxyPeer,
+			realIP:     realIPClient,
 			want:       "203.0.113.8:4000",
 		},
 		{
 			name:       "X-Forwarded-For wins over X-Real-IP",
-			remoteAddr: "10.0.0.1:4000",
-			forwarded:  []string{"203.0.113.7"},
-			realIP:     "203.0.113.8",
-			want:       "203.0.113.7:4000",
+			remoteAddr: proxyPeer,
+			forwarded:  []string{client},
+			realIP:     realIPClient,
+			want:       clientWithPort,
 		},
 		{
 			name:       "unparseable X-Forwarded-For entry gives peer",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			forwarded:  []string{"203.0.113.7, not-an-ip, 10.0.0.2"},
-			want:       "10.0.0.1:4000",
+			want:       proxyPeer,
 		},
 		{
 			name:       "unparseable entry past the client is not read",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			forwarded:  []string{"not-an-ip, 203.0.113.7"},
-			want:       "203.0.113.7:4000",
+			want:       clientWithPort,
 		},
 		{
 			name:       "unparseable X-Real-IP gives peer",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			realIP:     "not-an-ip",
-			want:       "10.0.0.1:4000",
+			want:       proxyPeer,
 		},
 		{
 			name:       "mapped IPv6 peer is unmapped and trusted",
 			remoteAddr: "[::ffff:10.0.0.1]:4000",
-			forwarded:  []string{"203.0.113.7"},
-			want:       "203.0.113.7:4000",
+			forwarded:  []string{client},
+			want:       clientWithPort,
 		},
 		{
 			name:       "mapped IPv6 peer outside the set",
 			remoteAddr: "[::ffff:192.0.2.1]:4000",
-			forwarded:  []string{"203.0.113.7"},
-			want:       "192.0.2.1:4000",
+			forwarded:  []string{client},
+			want:       directPeer,
 		},
 		{
 			name:       "IPv6 client",
-			remoteAddr: "10.0.0.1:4000",
+			remoteAddr: proxyPeer,
 			forwarded:  []string{"2001:db8::1"},
 			want:       "[2001:db8::1]:4000",
 		},
 	}
+}
 
-	handler := newMiddleware(t, "10.0.0.0/8").ClientIP()(
-		http.HandlerFunc(func(
-			writer http.ResponseWriter, request *http.Request,
-		) {
-			_, _ = writer.Write([]byte(request.RemoteAddr))
-		}),
-	)
+func TestClientIP(t *testing.T) {
+	t.Parallel()
 
-	for _, test := range tests {
+	mware := newMiddleware(t, trustedNetwork)
+
+	for _, test := range clientIPTests() {
 		t.Run(test.name, func(t *testing.T) {
 			t.Parallel()
 
+			var got string
+
+			handler := mware.ClientIP()(http.HandlerFunc(func(
+				_ http.ResponseWriter, request *http.Request,
+			) {
+				got = request.RemoteAddr
+			}))
+
 			request := httptest.NewRequestWithContext(
 				t.Context(), http.MethodGet, "/", nil,
 			)
@@ -132,10 +143,8 @@ func TestClientIP(t *testing.T) {
 				request.Header.Set("X-Real-IP", test.realIP)
 			}
 
-			recorder := httptest.NewRecorder()
-			handler.ServeHTTP(recorder, request)
+			handler.ServeHTTP(httptest.NewRecorder(), request)
 
-			got := recorder.Body.String()
 			if got != test.want {
 				t.Errorf("RemoteAddr = %q, want %q", got, test.want)
 			}
@@ -143,6 +152,73 @@ func TestClientIP(t *testing.T) {
 	}
 }
 
+func TestRequireJSON(t *testing.T) {
+	t.Parallel()
+
+	mware := newMiddleware(t, trustedNetwork)
+
+	const (
+		jsonType = "application/json"
+		textType = "text/plain"
+		refused  = http.StatusUnsupportedMediaType
+	)
+
+	tests := []struct {
+		method, contentType string
+		want                int
+	}{
+		{http.MethodPost, jsonType, http.StatusOK},
+		{http.MethodPost, "application/json; charset=utf-8", http.StatusOK},
+		{http.MethodPost, "Application/JSON", http.StatusOK},
+		{http.MethodPost, textType, refused},
+		{http.MethodPost, "application/x-www-form-urlencoded", refused},
+		{http.MethodPost, "multipart/form-data; boundary=x", refused},
+		{http.MethodPost, "", refused},
+		{http.MethodPost, "application/json; charset", refused},
+		{http.MethodPut, textType, refused},
+		{http.MethodPut, jsonType, http.StatusOK},
+		{http.MethodDelete, "", refused},
+		{http.MethodDelete, jsonType, http.StatusOK},
+		{http.MethodGet, "", http.StatusOK},
+		{http.MethodGet, textType, http.StatusOK},
+	}
+
+	for _, test := range tests {
+		t.Run(test.method+" "+test.contentType, func(t *testing.T) {
+			t.Parallel()
+
+			handler := mware.RequireJSON()(http.HandlerFunc(func(
+				http.ResponseWriter, *http.Request,
+			) {
+			}))
+
+			request := httptest.NewRequestWithContext(
+				t.Context(), test.method, "/", nil,
+			)
+			if test.contentType != "" {
+				request.Header.Set("Content-Type", test.contentType)
+			}
+
+			recorder := httptest.NewRecorder()
+
+			handler.ServeHTTP(recorder, request)
+
+			if recorder.Code != test.want {
+				t.Fatalf("status %d, want %d", recorder.Code, test.want)
+			}
+
+			if test.want == http.StatusOK {
+				return
+			}
+
+			want := `{"error":"content type must be application/json"}` + "\n"
+			if recorder.Body.String() != want {
+				t.Errorf("body %q, want %q", recorder.Body.String(), want)
+			}
+		})
+	}
+}
+
 // newMiddleware returns a Middleware that trusts the network trusted.
 func newMiddleware(t *testing.T, trusted string) *middleware.Middleware {
 	t.Helper()

internal/server/routes.go

@@ -30,7 +30,6 @@ func (srv *Server) SetupRoutes() {
 		srv.router.Use(srv.mw.Metrics())
 	}
 
-	srv.router.Use(srv.mw.CORS())
 	srv.router.Use(srv.mw.CSP())
 	srv.router.Use(middleware.Timeout(routeTimeout))
 
@@ -45,7 +44,7 @@ func (srv *Server) SetupRoutes() {
 	}
 
 	// Health check.
-	srv.router.Get(
+	srv.router.With(srv.mw.CORS()).Get(
 		"/.well-known/healthcheck.json",
 		srv.handlers.HandleHealthCheck(),
 	)
@@ -69,7 +68,9 @@ func (srv *Server) SetupRoutes() {
 }
 
 func (srv *Server) setupAPIv1(router chi.Router) {
-	router.Get(
+	router.Use(srv.mw.RequireJSON())
+
+	router.With(srv.mw.CORS()).Get(
 		"/server",
 		srv.handlers.HandleServerInfo(),
 	)

internal/server/server_test.go

@@ -6,8 +6,10 @@ package server_test
 
 import (
 	"fmt"
+	"maps"
 	"net"
 	"net/http"
+	"net/http/httptest"
 	"strconv"
 	"strings"
 	"testing"
@@ -188,6 +190,88 @@ func TestServeAfterStopDoesNotStopApp(t *testing.T) {
 	}
 }
 
+// TestCORSHeaders checks the Access-Control-Allow-* headers on the
+// answers to requests from another origin. The public, read-only
+// routes answer with Access-Control-Allow-Origin: * alone. Routes
+// that need the cookie, and a preflight to one, answer with none.
+func TestCORSHeaders(t *testing.T) {
+	var srv *server.Server
+
+	startApp(t, fx.Populate(&srv))
+
+	tests := []struct {
+		name          string
+		method        string
+		path          string
+		requestMethod string
+		wantHeaders   map[string]string
+	}{
+		{
+			name:        "server information",
+			method:      http.MethodGet,
+			path:        "/api/v1/server",
+			wantHeaders: map[string]string{"Access-Control-Allow-Origin": "*"},
+		},
+		{
+			name:        "health check",
+			method:      http.MethodGet,
+			path:        "/.well-known/healthcheck.json",
+			wantHeaders: map[string]string{"Access-Control-Allow-Origin": "*"},
+		},
+		{
+			name:   "send",
+			method: http.MethodPost,
+			path:   "/api/v1/messages",
+		},
+		{
+			name:   "state",
+			method: http.MethodGet,
+			path:   "/api/v1/state",
+		},
+		{
+			name:          "preflight for send",
+			method:        http.MethodOptions,
+			path:          "/api/v1/messages",
+			requestMethod: http.MethodPost,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			request := httptest.NewRequestWithContext(
+				t.Context(), test.method,
+				"http://chat.example.com"+test.path, nil,
+			)
+			request.Header.Set("Origin", "http://blog.example.com")
+
+			if test.requestMethod != "" {
+				request.Header.Set(
+					"Access-Control-Request-Method", test.requestMethod,
+				)
+			}
+
+			recorder := httptest.NewRecorder()
+
+			srv.ServeHTTP(recorder, request)
+
+			gotHeaders := map[string]string{}
+
+			for name := range recorder.Header() {
+				if strings.HasPrefix(name, "Access-Control-Allow-") {
+					gotHeaders[name] = recorder.Header().Get(name)
+				}
+			}
+
+			if !maps.Equal(gotHeaders, test.wantHeaders) {
+				t.Errorf(
+					"Access-Control-Allow-* headers are %v, want %v",
+					gotHeaders, test.wantHeaders,
+				)
+			}
+		})
+	}
+}
+
 // startApp starts the app newApp builds, with the HTTP port
 // set to 0, so the system gives the server a free port.
 func startApp(

internal/service/service_test.go

@@ -1,7 +1,3 @@
-// Tests use a global viper instance for configuration,
-// making parallel execution unsafe.
-//
-//nolint:paralleltest
 package service_test
 
 import (
@@ -59,28 +55,12 @@ func newTestEnv(t *testing.T) *testEnv {
 				}
 			},
 			logger.New,
-			func(
-				lifecycle fx.Lifecycle,
-				globs *globals.Globals,
-				log *logger.Logger,
-			) (*config.Config, error) {
-				cfg, err := config.New(
-					lifecycle, config.Params{ //nolint:exhaustruct
-						Globals: globs, Logger: log,
-					},
-				)
-				if err != nil {
-					return nil, fmt.Errorf(
-						"test config: %w", err,
-					)
+			func() *config.Config {
+				return &config.Config{
+					DBURL:        dbURL,
+					OperName:     "admin",
+					OperPassword: "secret",
 				}
-
-				cfg.DBURL = dbURL
-				cfg.Port = 0
-				cfg.OperName = "admin"
-				cfg.OperPassword = "secret"
-
-				return cfg, nil
 			},
 			func(
 				lifecycle fx.Lifecycle,
@@ -136,6 +116,8 @@ func createSession(
 // environment starts on an empty database while another one
 // is still open.
 func TestEachTestEnvHasItsOwnDatabase(t *testing.T) {
+	t.Parallel()
+
 	ctx := t.Context()
 
 	first := newTestEnv(t)
@@ -146,6 +128,8 @@ func TestEachTestEnvHasItsOwnDatabase(t *testing.T) {
 }
 
 func TestFanOut(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -173,6 +157,8 @@ func TestFanOut(t *testing.T) {
 }
 
 func TestJoinChannel(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -213,6 +199,8 @@ func TestJoinChannel(t *testing.T) {
 }
 
 func TestPartChannel(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -313,6 +301,8 @@ func joinConcurrently(
 // concurrent JOINs of a +l 2 channel with one member, one
 // gets in and the other gets ERR_CHANNELISFULL.
 func TestConcurrentJoinsRespectUserLimit(t *testing.T) {
+	t.Parallel()
+
 	const userLimit = 2
 
 	env := newTestEnv(t)
@@ -375,6 +365,8 @@ func TestConcurrentJoinsRespectUserLimit(t *testing.T) {
 // two concurrent JOINs that create a channel, exactly one
 // makes its session the operator.
 func TestConcurrentFirstJoinsMakeOneOperator(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -426,6 +418,8 @@ func TestConcurrentFirstJoinsMakeOneOperator(t *testing.T) {
 // either joins a channel that still exists or gets
 // ERR_NOSUCHCHANNEL, and never fails otherwise.
 func TestJoinConcurrentWithLastPart(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -491,6 +485,8 @@ func TestJoinConcurrentWithLastPart(t *testing.T) {
 // quits, gets in only once the channel is deleted, into a
 // new channel of that name with no key.
 func TestJoinConcurrentWithLastQuit(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -569,81 +565,95 @@ const quitCrowdSize = 10
 // ahead of that JOIN. The quitting session is also on a
 // channel with quitCrowdSize other sessions, made before the
 // watcher's channel, so that its QUIT reaches the watcher
-// last.
+// last. Each trial runs on a database of its own.
 func TestQuitQueuedAheadOfNewNickHoldersJoin(t *testing.T) {
-	env := newTestEnv(t)
-	ctx := t.Context()
+	t.Parallel()
 
 	for trial := range concurrentJoinTrials {
-		nick := fmt.Sprintf("reused%d", trial)
-		crowd := fmt.Sprintf("#crowd%d", trial)
-		shared := fmt.Sprintf("#shared%d", trial)
-		quitterSID := createSession(ctx, t, env.db, nick)
+		t.Run(fmt.Sprintf("trial %d", trial), func(t *testing.T) {
+			t.Parallel()
 
-		for _, channel := range []string{crowd, shared} {
-			_, err := env.svc.JoinChannel(ctx, quitterSID, 0, nick, channel, "")
-			if err != nil {
-				t.Fatalf("join %s: %v", channel, err)
-			}
+			checkQuitQueuedAheadOfJoin(t, newTestEnv(t))
+		})
+	}
+}
+
+// checkQuitQueuedAheadOfJoin runs one trial of
+// TestQuitQueuedAheadOfNewNickHoldersJoin on env.
+func checkQuitQueuedAheadOfJoin(t *testing.T, env *testEnv) {
+	t.Helper()
+
+	const (
+		nick        = "reused"
+		crowd       = "#crowd"
+		shared      = "#shared"
+		watcherNick = "watcher"
+	)
+
+	ctx := t.Context()
+	quitterSID := createSession(ctx, t, env.db, nick)
+
+	for _, channel := range []string{crowd, shared} {
+		_, err := env.svc.JoinChannel(ctx, quitterSID, 0, nick, channel, "")
+		if err != nil {
+			t.Fatalf("join %s: %v", channel, err)
 		}
+	}
 
-		for member := range quitCrowdSize {
-			memberNick := fmt.Sprintf("crowd%dx%d", trial, member)
-			memberSID := createSession(ctx, t, env.db, memberNick)
+	for member := range quitCrowdSize {
+		memberNick := fmt.Sprintf("crowd%d", member)
+		memberSID := createSession(ctx, t, env.db, memberNick)
 
-			_, err := env.svc.JoinChannel(ctx, memberSID, 0, memberNick, crowd, "")
-			if err != nil {
-				t.Fatalf("join %s: %v", memberNick, err)
-			}
+		_, err := env.svc.JoinChannel(ctx, memberSID, 0, memberNick, crowd, "")
+		if err != nil {
+			t.Fatalf("join %s: %v", memberNick, err)
 		}
+	}
 
-		watcherNick := fmt.Sprintf("watcher%d", trial)
+	watcherSID, watcherClientID, _, err := env.db.CreateSession(
+		ctx, watcherNick, watcherNick, "localhost", "127.0.0.1",
+	)
+	if err != nil {
+		t.Fatalf("create session %s: %v", watcherNick, err)
+	}
 
-		watcherSID, watcherClientID, _, err := env.db.CreateSession(
-			ctx, watcherNick, watcherNick, "localhost", "127.0.0.1",
+	_, err = env.svc.JoinChannel(ctx, watcherSID, 0, watcherNick, shared, "")
+	if err != nil {
+		t.Fatalf("join %s: %v", watcherNick, err)
+	}
+
+	_, lastQueueID, err := env.db.PollMessages(ctx, watcherClientID, 0, 0)
+	if err != nil {
+		t.Fatalf("poll: %v", err)
+	}
+
+	errs := runConcurrently(
+		func() error {
+			env.svc.BroadcastQuit(ctx, quitterSID, nick, "")
+
+			return nil
+		},
+		func() error {
+			return takeNickAndJoin(ctx, env, nick, shared)
+		},
+	)
+	if errs[1] != nil {
+		t.Fatalf("new session: %v", errs[1])
+	}
+
+	msgs, _, err := env.db.PollMessages(
+		ctx, watcherClientID, lastQueueID, 0,
+	)
+	if err != nil {
+		t.Fatalf("poll: %v", err)
+	}
+
+	commands := commandsFrom(msgs, nick)
+	if !slices.Equal(commands, []string{irc.CmdQuit, irc.CmdJoin}) {
+		t.Errorf(
+			"watcher got %v from %s, want QUIT then JOIN",
+			commands, nick,
 		)
-		if err != nil {
-			t.Fatalf("create session %s: %v", watcherNick, err)
-		}
-
-		_, err = env.svc.JoinChannel(ctx, watcherSID, 0, watcherNick, shared, "")
-		if err != nil {
-			t.Fatalf("join %s: %v", watcherNick, err)
-		}
-
-		_, lastQueueID, err := env.db.PollMessages(ctx, watcherClientID, 0, 0)
-		if err != nil {
-			t.Fatalf("poll: %v", err)
-		}
-
-		errs := runConcurrently(
-			func() error {
-				env.svc.BroadcastQuit(ctx, quitterSID, nick, "")
-
-				return nil
-			},
-			func() error {
-				return takeNickAndJoin(ctx, env, nick, shared)
-			},
-		)
-		if errs[1] != nil {
-			t.Fatalf("trial %d: new session: %v", trial, errs[1])
-		}
-
-		msgs, _, err := env.db.PollMessages(
-			ctx, watcherClientID, lastQueueID, 0,
-		)
-		if err != nil {
-			t.Fatalf("poll: %v", err)
-		}
-
-		commands := commandsFrom(msgs, nick)
-		if !slices.Equal(commands, []string{irc.CmdQuit, irc.CmdJoin}) {
-			t.Errorf(
-				"trial %d: watcher got %v from %s, want QUIT then JOIN",
-				trial, commands, nick,
-			)
-		}
 	}
 }
 
@@ -691,6 +701,8 @@ func commandsFrom(msgs []db.IRCMessage, nick string) []string {
 // into a +i channel uses the invite up, so that a JOIN
 // after leaving gets ERR_INVITEONLYCHAN.
 func TestJoinUsesUpInvite(t *testing.T) {
+	t.Parallel()
+
 	const channel = "#club"
 
 	env := newTestEnv(t)
@@ -736,6 +748,8 @@ func TestJoinUsesUpInvite(t *testing.T) {
 // session's nick, username and hostname refuses its JOIN
 // with ERR_BANNEDFROMCHAN.
 func TestJoinRefusedByHostmaskBan(t *testing.T) {
+	t.Parallel()
+
 	const channel = "#club"
 
 	env := newTestEnv(t)
@@ -774,6 +788,8 @@ func TestJoinRefusedByHostmaskBan(t *testing.T) {
 // keeps a channel other members are still on and deletes
 // the channel when its last member parts.
 func TestPartDeletesChannelOnlyWhenEmpty(t *testing.T) {
+	t.Parallel()
+
 	const channel = "#room"
 
 	env := newTestEnv(t)
@@ -821,6 +837,8 @@ func TestPartDeletesChannelOnlyWhenEmpty(t *testing.T) {
 // TestKickOfLastMemberDeletesChannel checks that a KICK
 // that leaves a channel with no members deletes it.
 func TestKickOfLastMemberDeletesChannel(t *testing.T) {
+	t.Parallel()
+
 	const channel = "#room"
 
 	env := newTestEnv(t)
@@ -845,6 +863,8 @@ func TestKickOfLastMemberDeletesChannel(t *testing.T) {
 }
 
 func TestSendChannelMessage(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -892,6 +912,8 @@ func TestSendChannelMessage(t *testing.T) {
 }
 
 func TestBroadcastQuit(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -929,6 +951,8 @@ func TestBroadcastQuit(t *testing.T) {
 // error as a DM to an unknown nick. The trigger deletes the
 // target's session just before the DM is stored.
 func TestSendDirectMessageTargetQuits(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -960,6 +984,8 @@ func TestSendDirectMessageTargetQuits(t *testing.T) {
 // trigger deletes the channel just before the message is
 // stored.
 func TestSendChannelMessageChannelDeleted(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -991,6 +1017,8 @@ func TestSendChannelMessageChannelDeleted(t *testing.T) {
 }
 
 func TestSendChannelMessage_Moderated(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -1042,6 +1070,8 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 // not spend its hashcash stamp: the operator can then send
 // the same message with it.
 func TestRefusedChannelMessageLeavesStampUnspent(t *testing.T) {
+	t.Parallel()
+
 	const (
 		channel = "#paid"
 		bits    = 2
@@ -1067,6 +1097,8 @@ func TestRefusedChannelMessageLeavesStampUnspent(t *testing.T) {
 
 	for _, refusal := range refusals {
 		t.Run(refusal.name, func(t *testing.T) {
+			t.Parallel()
+
 			env := newTestEnv(t)
 			ctx := t.Context()
 
@@ -1119,6 +1151,8 @@ func TestRefusedChannelMessageLeavesStampUnspent(t *testing.T) {
 }
 
 func TestQueryUserMode(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -1169,6 +1203,8 @@ func TestQueryUserMode(t *testing.T) {
 }
 
 func TestUserhostReply(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 	ctx := t.Context()
 
@@ -1274,10 +1310,14 @@ func applyUserModeTests() []applyUserModeTest {
 }
 
 func TestApplyUserMode(t *testing.T) {
+	t.Parallel()
+
 	env := newTestEnv(t)
 
 	for i, test := range applyUserModeTests() {
 		t.Run(test.modeStr, func(t *testing.T) {
+			t.Parallel()
+
 			ctx := t.Context()
 			sid := createSession(
 				ctx, t, env.db, fmt.Sprintf("user%d", i),