feat: add username/hostname support with IRC hostmask format

- Add username and hostname columns to sessions table (001_initial.sql) - Accept optional username field in session creation and registration endpoints; defaults to nick if not provided - Resolve hostname via reverse DNS of connecting client IP at session creation time (supports X-Forwarded-For and X-Real-IP headers) - Display real username and hostname in WHOIS (311 RPL_WHOISUSER) and WHO (352 RPL_WHOREPLY) responses instead of nick/servername - Add FormatHostmask helper for nick!user@host format - Add SessionHostInfo type and GetSessionHostInfo query - Include username/hostname in MemberInfo and ChannelMembers results - Extract validateHashcash and resolveUsername helpers to stay under funlen limits - Add comprehensive unit tests for all new DB functions, hostmask formatting, and integration tests for WHOIS/WHO responses - Update README with hostmask documentation, new API fields, and updated schema reference
2026-03-17 05:34:57 -07:00
15 changed files with 773 additions and 491 deletions
--- a/README.md
+++ b/README.md
@@ -207,6 +207,26 @@ removal. Identity verification at the message layer via cryptographic
 signatures (see [Security Model](#security-model)) remains independent
 of account registration.

+### Hostmask (nick!user@host)
+
+Each session has an IRC-style hostmask composed of three parts:
+
+- **nick** — the user's current nick (changes with `NICK` command)
+- **username** — an ident-like identifier set at session creation (optional
+  `username` field in the session/register request; defaults to the nick)
+- **hostname** — automatically resolved via reverse DNS of the connecting
+  client's IP address at session creation time
+
+The hostmask appears in:
+
+- **WHOIS** (`311 RPL_WHOISUSER`) — `params` contains
+  `[nick, username, hostname, "*"]`
+- **WHO** (`352 RPL_WHOREPLY`) — `params` contains
+  `[channel, username, hostname, server, nick, flags]`
+
+The hostmask format (`nick!user@host`) is stored for future use in ban matching
+(`+b` mode) and other access control features.
+
 ### Nick Semantics

 - Nicks are **unique per server at any point in time** — two sessions cannot
@@ -976,7 +996,7 @@ the server to the client (never C2S) and use 3-digit string codes in the
 | `252` | RPL_LUSEROP         | On connect or LUSERS command | `{"command":"252","to":"alice","params":["0"],"body":["operator(s) online"]}` |
 | `254` | RPL_LUSERCHANNELS   | On connect or LUSERS command | `{"command":"254","to":"alice","params":["3"],"body":["channels formed"]}` |
 | `255` | RPL_LUSERME         | On connect or LUSERS command | `{"command":"255","to":"alice","body":["I have 5 clients and 1 servers"]}` |
-| `311` | RPL_WHOISUSER       | In response to WHOIS | `{"command":"311","to":"alice","params":["bob","bob","neoirc","*"],"body":["bob"]}` |
+| `311` | RPL_WHOISUSER       | In response to WHOIS | `{"command":"311","to":"alice","params":["bob","bobident","host.example.com","*"],"body":["bob"]}` |
 | `312` | RPL_WHOISSERVER     | In response to WHOIS | `{"command":"312","to":"alice","params":["bob","neoirc"],"body":["neoirc server"]}` |
 | `315` | RPL_ENDOFWHO        | End of WHO response | `{"command":"315","to":"alice","params":["#general"],"body":["End of /WHO list"]}` |
 | `318` | RPL_ENDOFWHOIS      | End of WHOIS response | `{"command":"318","to":"alice","params":["bob"],"body":["End of /WHOIS list"]}` |
@@ -987,7 +1007,7 @@ the server to the client (never C2S) and use 3-digit string codes in the
 | `329` | RPL_CREATIONTIME    | After channel MODE query | `{"command":"329","to":"alice","params":["#general","1709251200"]}` |
 | `331` | RPL_NOTOPIC         | Channel has no topic (on JOIN) | `{"command":"331","to":"alice","params":["#general"],"body":["No topic is set"]}` |
 | `332` | RPL_TOPIC           | On JOIN or TOPIC query | `{"command":"332","to":"alice","params":["#general"],"body":["Welcome!"]}` |
-| `352` | RPL_WHOREPLY        | In response to WHO | `{"command":"352","to":"alice","params":["#general","bob","neoirc","neoirc","bob","H"],"body":["0 bob"]}` |
+| `352` | RPL_WHOREPLY        | In response to WHO | `{"command":"352","to":"alice","params":["#general","bobident","host.example.com","neoirc","bob","H"],"body":["0 bob"]}` |
 | `353` | RPL_NAMREPLY        | On JOIN or NAMES query | `{"command":"353","to":"alice","params":["=","#general"],"body":["@op1 alice bob +voiced1"]}` |
 | `366` | RPL_ENDOFNAMES      | End of NAMES response | `{"command":"366","to":"alice","params":["#general"],"body":["End of /NAMES list"]}` |
 | `372` | RPL_MOTD            | MOTD line | `{"command":"372","to":"alice","body":["Welcome to the server"]}` |
@@ -1056,14 +1076,20 @@ difficulty is advertised via `GET /api/v1/server` in the `hashcash_bits` field.

 **Request Body:**
 ```json
-{"nick": "alice", "pow_token": "1:20:260310:neoirc::3a2f1"}
+{"nick": "alice", "username": "alice", "pow_token": "1:20:260310:neoirc::3a2f1"}
 ```

 | Field      | Type   | Required    | Constraints |
 |------------|--------|-------------|-------------|
 | `nick`     | string | Yes         | 1–32 characters, must be unique on the server |
+| `username` | string | No          | 1–32 characters, IRC ident-style. Defaults to nick if omitted. |
 | `pow_token` | string | Conditional | Hashcash stamp (required when server has `hashcash_bits` > 0) |

+The `username` field sets the user portion of the IRC hostmask
+(`nick!user@host`). The hostname is automatically resolved via reverse DNS of
+the connecting client's IP address at session creation time. Together these form
+the hostmask used in WHOIS, WHO, and future ban matching (`+b`).
+
 **Response:** `201 Created`
 ```json
 {
@@ -1084,6 +1110,7 @@ difficulty is advertised via `GET /api/v1/server` in the `hashcash_bits` field.
 | Status | Error | When |
 |--------|-------|------|
 | 400    | `nick must be 1-32 characters` | Empty or too-long nick |
+| 400    | `invalid username format` | Username doesn't match allowed format |
 | 402    | `hashcash proof-of-work required` | Missing `pow_token` field in request body when hashcash is enabled |
 | 402    | `invalid hashcash stamp: ...` | Stamp fails validation (wrong bits, expired, reused, etc.) |
 | 409    | `nick already taken` | Another active session holds this nick |
@@ -1105,14 +1132,18 @@ remains active.

 **Request Body:**
 ```json
-{"nick": "alice", "password": "mypassword"}
+{"nick": "alice", "username": "alice", "password": "mypassword"}
 ```

 | Field      | Type   | Required | Constraints |
 |------------|--------|----------|-------------|
 | `nick`     | string | Yes      | 1–32 characters, must be unique on the server |
+| `username` | string | No       | 1–32 characters, IRC ident-style. Defaults to nick if omitted. |
 | `password` | string | Yes      | Minimum 8 characters |

+The `username` and hostname (auto-resolved via reverse DNS) form the IRC
+hostmask (`nick!user@host`) shown in WHOIS and WHO responses.
+
 **Response:** `201 Created`
 ```json
 {
@@ -1133,6 +1164,7 @@ remains active.
 | Status | Error | When |
 |--------|-------|------|
 | 400    | `invalid nick format` | Nick doesn't match allowed format |
+| 400    | `invalid username format` | Username doesn't match allowed format |
 | 400    | `password must be at least 8 characters` | Password too short |
 | 409    | `nick already taken` | Another active session holds this nick |

@@ -1941,6 +1973,8 @@ The database schema is managed via embedded SQL migration files in
 | `id`           | INTEGER  | Primary key (auto-increment) |
 | `uuid`         | TEXT     | Unique session UUID |
 | `nick`         | TEXT     | Unique nick |
+| `username`     | TEXT     | IRC ident/username portion of the hostmask (defaults to nick) |
+| `hostname`     | TEXT     | Reverse DNS hostname of the connecting client IP |
 | `password_hash`| TEXT     | bcrypt hash (empty string for anonymous sessions) |
 | `signing_key`  | TEXT     | Public signing key (empty string if unset) |
 | `away_message` | TEXT     | Away message (empty string if not away) |
@@ -2051,8 +2085,6 @@ directory is also loaded automatically via
 | `METRICS_USERNAME` | string  | `""`                                 | Basic auth username for `/metrics` endpoint. If empty, metrics endpoint is disabled. |
 | `METRICS_PASSWORD` | string  | `""`                                 | Basic auth password for `/metrics` endpoint |
 | `NEOIRC_HASHCASH_BITS` | int | `20`                               | Required hashcash proof-of-work difficulty (leading zero bits in SHA-256) for session creation. Set to `0` to disable. |
-| `LOGIN_RATE_LIMIT` | float   | `1`                                  | Allowed login attempts per second per IP address. |
-| `LOGIN_RATE_BURST`  | int    | `5`                                  | Maximum burst of login attempts per IP before rate limiting kicks in. |
 | `MAINTENANCE_MODE` | bool    | `false`                              | Maintenance mode flag (reserved) |

 ### Example `.env` file
@@ -2457,49 +2489,6 @@ creating one session pays once and keeps their session.
 - **Language-agnostic**: SHA-256 is available in every programming language.
  The proof computation is trivially implementable in any client.

-### Login Rate Limiting
-
-The login endpoint (`POST /api/v1/login`) has per-IP rate limiting to prevent
-brute-force password attacks. This uses a token-bucket algorithm
-(`golang.org/x/time/rate`) with configurable rate and burst.
-
-| Environment Variable | Default | Description |
-|---------------------|---------|-------------|
-| `LOGIN_RATE_LIMIT`  | `1`     | Allowed login attempts per second per IP |
-| `LOGIN_RATE_BURST`  | `5`     | Maximum burst of login attempts per IP |
-
-When the limit is exceeded, the server returns **429 Too Many Requests** with a
-`Retry-After: 1` header. Stale per-IP entries are automatically cleaned up
-every 10 minutes.
-
-> **⚠️ Security: Reverse Proxy Required for Production Use**
->
-> The rate limiter extracts the client IP by checking the `X-Forwarded-For`
-> header first, then `X-Real-IP`, and finally falling back to the TCP
-> `RemoteAddr`. Both `X-Forwarded-For` and `X-Real-IP` are **client-controlled
-> request headers** — any client can set them to arbitrary values.
->
-> Without a properly configured reverse proxy in front of this server:
->
-> - An attacker can **bypass rate limiting entirely** by rotating
->   `X-Forwarded-For` values on each request (each value is treated as a
->   distinct IP).
-> - An attacker can **deny service to a specific user** by spoofing that user's
->   IP in the `X-Forwarded-For` header, exhausting their rate limit bucket.
->
-> **Recommendation:** Always deploy behind a reverse proxy (e.g. nginx, Caddy,
-> Traefik) that strips or overwrites incoming `X-Forwarded-For` and `X-Real-IP`
-> headers with the actual client IP. If running without a reverse proxy, be
-> aware that the rate limiting provides no meaningful protection against a
-> targeted attack.
-
-**Why rate limits here but not on session creation?** Session creation is
-protected by hashcash proof-of-work (stateless, no IP tracking needed). Login
-involves bcrypt password verification against a registered account — a
-fundamentally different threat model where an attacker targets a specific
-account. Per-IP rate limiting is appropriate here because the cost of a wrong
-guess is borne by the server (bcrypt), not the client.
-
 ---

 ## Roadmap
--- a/go.mod
+++ b/go.mod
@@ -16,7 +16,6 @@ require (
 	github.com/spf13/viper v1.21.0
 	go.uber.org/fx v1.24.0
 	golang.org/x/crypto v0.48.0
-	golang.org/x/time v0.6.0
 	modernc.org/sqlite v1.45.0
 )

--- a/go.sum
+++ b/go.sum
@@ -151,8 +151,6 @@ golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
 golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
-golang.org/x/time v0.6.0 h1:eTDhh4ZXt5Qf0augr54TN6suAUudPcawVZeIAPU7D4U=
-golang.org/x/time v0.6.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -46,8 +46,6 @@ type Config struct {
 	FederationKey      string
 	SessionIdleTimeout string
 	HashcashBits       int
-	LoginRateLimit     float64
-	LoginRateBurst     int
 	params             *Params
 	log                *slog.Logger
 }
@@ -80,8 +78,6 @@ func New(
 	viper.SetDefault("FEDERATION_KEY", "")
 	viper.SetDefault("SESSION_IDLE_TIMEOUT", "720h")
 	viper.SetDefault("NEOIRC_HASHCASH_BITS", "20")
-	viper.SetDefault("LOGIN_RATE_LIMIT", "1")
-	viper.SetDefault("LOGIN_RATE_BURST", "5")

 	err := viper.ReadInConfig()
 	if err != nil {
@@ -108,8 +104,6 @@ func New(
 		FederationKey:      viper.GetString("FEDERATION_KEY"),
 		SessionIdleTimeout: viper.GetString("SESSION_IDLE_TIMEOUT"),
 		HashcashBits:       viper.GetInt("NEOIRC_HASHCASH_BITS"),
-		LoginRateLimit:     viper.GetFloat64("LOGIN_RATE_LIMIT"),
-		LoginRateBurst:     viper.GetInt("LOGIN_RATE_BURST"),
 		log:                log,
 		params:             &params,
 	}
--- a/internal/db/auth.go
+++ b/internal/db/auth.go
@@ -20,8 +20,12 @@ var errNoPassword = errors.New(
 // and returns session ID, client ID, and token.
 func (database *Database) RegisterUser(
 	ctx context.Context,
-	nick, password string,
+	nick, password, username, hostname string,
 ) (int64, int64, string, error) {
+	if username == "" {
+		username = nick
+	}
+
 	hash, err := bcrypt.GenerateFromPassword(
 		[]byte(password), bcryptCost,
 	)
@@ -50,10 +54,11 @@ func (database *Database) RegisterUser(

 	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO sessions
-		 (uuid, nick, password_hash,
-		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?)`,
-		sessionUUID, nick, string(hash), now, now)
+		 (uuid, nick, username, hostname,
+		  password_hash, created_at, last_seen)
+		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
+		sessionUUID, nick, username, hostname,
+		string(hash), now, now)
 	if err != nil {
 		_ = transaction.Rollback()

--- a/internal/db/auth_test.go
+++ b/internal/db/auth_test.go
@@ -13,7 +13,7 @@ func TestRegisterUser(t *testing.T) {
 	ctx := t.Context()

 	sessionID, clientID, token, err :=
-		database.RegisterUser(ctx, "reguser", "password123")
+		database.RegisterUser(ctx, "reguser", "password123", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -38,6 +38,69 @@ func TestRegisterUser(t *testing.T) {
 	}
 }

+func TestRegisterUserWithUserHost(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+	ctx := t.Context()
+
+	sessionID, _, _, err := database.RegisterUser(
+		ctx, "reguhost", "password123",
+		"myident", "example.org",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	info, err := database.GetSessionHostInfo(
+		ctx, sessionID,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if info.Username != "myident" {
+		t.Fatalf(
+			"expected myident, got %s", info.Username,
+		)
+	}
+
+	if info.Hostname != "example.org" {
+		t.Fatalf(
+			"expected example.org, got %s",
+			info.Hostname,
+		)
+	}
+}
+
+func TestRegisterUserDefaultUsername(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+	ctx := t.Context()
+
+	sessionID, _, _, err := database.RegisterUser(
+		ctx, "regdefault", "password123", "", "",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	info, err := database.GetSessionHostInfo(
+		ctx, sessionID,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if info.Username != "regdefault" {
+		t.Fatalf(
+			"expected regdefault, got %s",
+			info.Username,
+		)
+	}
+}
+
 func TestRegisterUserDuplicateNick(t *testing.T) {
 	t.Parallel()

@@ -45,7 +108,7 @@ func TestRegisterUserDuplicateNick(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "dupnick", "password123")
+		database.RegisterUser(ctx, "dupnick", "password123", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -55,7 +118,7 @@ func TestRegisterUserDuplicateNick(t *testing.T) {
 	_ = regToken

 	dupSID, dupCID, dupToken, dupErr :=
-		database.RegisterUser(ctx, "dupnick", "other12345")
+		database.RegisterUser(ctx, "dupnick", "other12345", "", "")
 	if dupErr == nil {
 		t.Fatal("expected error for duplicate nick")
 	}
@@ -72,7 +135,7 @@ func TestLoginUser(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "loginuser", "mypassword")
+		database.RegisterUser(ctx, "loginuser", "mypassword", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -110,7 +173,7 @@ func TestLoginUserWrongPassword(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "wrongpw", "correctpass")
+		database.RegisterUser(ctx, "wrongpw", "correctpass", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -138,7 +201,7 @@ func TestLoginUserNoPassword(t *testing.T) {

 	// Create anonymous session (no password).
 	anonSID, anonCID, anonToken, err :=
-		database.CreateSession(ctx, "anon")
+		database.CreateSession(ctx, "anon", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
--- a/internal/db/queries.go
+++ b/internal/db/queries.go
@@ -74,14 +74,40 @@ type ChannelInfo struct {
 type MemberInfo struct {
 	ID       int64     `json:"id"`
 	Nick     string    `json:"nick"`
+	Username string    `json:"username"`
+	Hostname string    `json:"hostname"`
 	LastSeen time.Time `json:"lastSeen"`
 }

+// Hostmask returns the IRC hostmask in
+// nick!user@host format.
+func (m *MemberInfo) Hostmask() string {
+	return FormatHostmask(m.Nick, m.Username, m.Hostname)
+}
+
+// FormatHostmask formats a nick, username, and hostname
+// into a standard IRC hostmask string (nick!user@host).
+func FormatHostmask(nick, username, hostname string) string {
+	if username == "" {
+		username = nick
+	}
+
+	if hostname == "" {
+		hostname = "*"
+	}
+
+	return nick + "!" + username + "@" + hostname
+}
+
 // CreateSession registers a new session and its first client.
 func (database *Database) CreateSession(
 	ctx context.Context,
-	nick string,
+	nick, username, hostname string,
 ) (int64, int64, string, error) {
+	if username == "" {
+		username = nick
+	}
+
 	sessionUUID := uuid.New().String()
 	clientUUID := uuid.New().String()

@@ -101,9 +127,10 @@ func (database *Database) CreateSession(

 	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO sessions
-		 (uuid, nick, created_at, last_seen)
-		 VALUES (?, ?, ?, ?)`,
-		sessionUUID, nick, now, now)
+		 (uuid, nick, username, hostname,
+		  created_at, last_seen)
+		 VALUES (?, ?, ?, ?, ?, ?)`,
+		sessionUUID, nick, username, hostname, now, now)
 	if err != nil {
 		_ = transaction.Rollback()

@@ -209,6 +236,35 @@ func (database *Database) GetSessionByNick(
 	return sessionID, nil
 }

+// SessionHostInfo holds the username and hostname for a session.
+type SessionHostInfo struct {
+	Username string
+	Hostname string
+}
+
+// GetSessionHostInfo returns the username and hostname
+// for a session.
+func (database *Database) GetSessionHostInfo(
+	ctx context.Context,
+	sessionID int64,
+) (*SessionHostInfo, error) {
+	var info SessionHostInfo
+
+	err := database.conn.QueryRowContext(
+		ctx,
+		`SELECT username, hostname
+		 FROM sessions WHERE id = ?`,
+		sessionID,
+	).Scan(&info.Username, &info.Hostname)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"get session host info: %w", err,
+		)
+	}
+
+	return &info, nil
+}
+
 // GetChannelByName returns the channel ID for a name.
 func (database *Database) GetChannelByName(
 	ctx context.Context,
@@ -388,7 +444,8 @@ func (database *Database) ChannelMembers(
 	channelID int64,
 ) ([]MemberInfo, error) {
 	rows, err := database.conn.QueryContext(ctx,
-		`SELECT s.id, s.nick, s.last_seen
+		`SELECT s.id, s.nick, s.username,
+		   s.hostname, s.last_seen
 		 FROM sessions s
 		 INNER JOIN channel_members cm
 		   ON cm.session_id = s.id
@@ -408,7 +465,9 @@ func (database *Database) ChannelMembers(
 		var member MemberInfo

 		err = rows.Scan(
-			&member.ID, &member.Nick, &member.LastSeen,
+			&member.ID, &member.Nick,
+			&member.Username, &member.Hostname,
+			&member.LastSeen,
 		)
 		if err != nil {
 			return nil, fmt.Errorf(
--- a/internal/db/queries_test.go
+++ b/internal/db/queries_test.go
@@ -34,7 +34,7 @@ func TestCreateSession(t *testing.T) {
 	ctx := t.Context()

 	sessionID, _, token, err := database.CreateSession(
-		ctx, "alice",
+		ctx, "alice", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -45,7 +45,7 @@ func TestCreateSession(t *testing.T) {
 	}

 	_, _, dupToken, dupErr := database.CreateSession(
-		ctx, "alice",
+		ctx, "alice", "", "",
 	)
 	if dupErr == nil {
 		t.Fatal("expected error for duplicate nick")
@@ -54,13 +54,186 @@ func TestCreateSession(t *testing.T) {
 	_ = dupToken
 }

+// assertSessionHostInfo creates a session and verifies
+// the stored username and hostname match expectations.
+func assertSessionHostInfo(
+	t *testing.T,
+	database *db.Database,
+	nick, inputUser, inputHost,
+	expectUser, expectHost string,
+) {
+	t.Helper()
+
+	sessionID, _, _, err := database.CreateSession(
+		t.Context(), nick, inputUser, inputHost,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	info, err := database.GetSessionHostInfo(
+		t.Context(), sessionID,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if info.Username != expectUser {
+		t.Fatalf(
+			"expected username %s, got %s",
+			expectUser, info.Username,
+		)
+	}
+
+	if info.Hostname != expectHost {
+		t.Fatalf(
+			"expected hostname %s, got %s",
+			expectHost, info.Hostname,
+		)
+	}
+}
+
+func TestCreateSessionWithUserHost(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+
+	assertSessionHostInfo(
+		t, database,
+		"hostuser", "myident", "example.com",
+		"myident", "example.com",
+	)
+}
+
+func TestCreateSessionDefaultUsername(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+
+	// Empty username defaults to nick.
+	assertSessionHostInfo(
+		t, database,
+		"defaultu", "", "host.local",
+		"defaultu", "host.local",
+	)
+}
+
+func TestGetSessionHostInfoNotFound(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+
+	_, err := database.GetSessionHostInfo(
+		t.Context(), 99999,
+	)
+	if err == nil {
+		t.Fatal("expected error for nonexistent session")
+	}
+}
+
+func TestFormatHostmask(t *testing.T) {
+	t.Parallel()
+
+	result := db.FormatHostmask(
+		"nick", "user", "host.com",
+	)
+	if result != "nick!user@host.com" {
+		t.Fatalf(
+			"expected nick!user@host.com, got %s",
+			result,
+		)
+	}
+}
+
+func TestFormatHostmaskDefaults(t *testing.T) {
+	t.Parallel()
+
+	result := db.FormatHostmask("nick", "", "")
+	if result != "nick!nick@*" {
+		t.Fatalf(
+			"expected nick!nick@*, got %s",
+			result,
+		)
+	}
+}
+
+func TestMemberInfoHostmask(t *testing.T) {
+	t.Parallel()
+
+	member := &db.MemberInfo{ //nolint:exhaustruct // test only uses hostmask fields
+		Nick:     "alice",
+		Username: "aliceident",
+		Hostname: "alice.example.com",
+	}
+
+	hostmask := member.Hostmask()
+	expected := "alice!aliceident@alice.example.com"
+
+	if hostmask != expected {
+		t.Fatalf(
+			"expected %s, got %s", expected, hostmask,
+		)
+	}
+}
+
+func TestChannelMembersIncludeUserHost(t *testing.T) {
+	t.Parallel()
+
+	database := setupTestDB(t)
+	ctx := t.Context()
+
+	sid, _, _, err := database.CreateSession(
+		ctx, "memuser", "myuser", "myhost.net",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chID, err := database.GetOrCreateChannel(
+		ctx, "#hostchan",
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = database.JoinChannel(ctx, chID, sid)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	members, err := database.ChannelMembers(ctx, chID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(members) != 1 {
+		t.Fatalf(
+			"expected 1 member, got %d", len(members),
+		)
+	}
+
+	if members[0].Username != "myuser" {
+		t.Fatalf(
+			"expected username myuser, got %s",
+			members[0].Username,
+		)
+	}
+
+	if members[0].Hostname != "myhost.net" {
+		t.Fatalf(
+			"expected hostname myhost.net, got %s",
+			members[0].Hostname,
+		)
+	}
+}
+
 func TestGetSessionByToken(t *testing.T) {
 	t.Parallel()

 	database := setupTestDB(t)
 	ctx := t.Context()

-	_, _, token, err := database.CreateSession(ctx, "bob")
+	_, _, token, err := database.CreateSession(ctx, "bob", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -93,7 +266,7 @@ func TestGetSessionByNick(t *testing.T) {
 	ctx := t.Context()

 	charlieID, charlieClientID, charlieToken, err :=
-		database.CreateSession(ctx, "charlie")
+		database.CreateSession(ctx, "charlie", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -150,7 +323,7 @@ func TestJoinAndPart(t *testing.T) {
 	database := setupTestDB(t)
 	ctx := t.Context()

-	sid, _, _, err := database.CreateSession(ctx, "user1")
+	sid, _, _, err := database.CreateSession(ctx, "user1", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -199,7 +372,7 @@ func TestDeleteChannelIfEmpty(t *testing.T) {
 		t.Fatal(err)
 	}

-	sid, _, _, err := database.CreateSession(ctx, "temp")
+	sid, _, _, err := database.CreateSession(ctx, "temp", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -234,7 +407,7 @@ func createSessionWithChannels(

 	ctx := t.Context()

-	sid, _, _, err := database.CreateSession(ctx, nick)
+	sid, _, _, err := database.CreateSession(ctx, nick, "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -317,7 +490,7 @@ func TestChangeNick(t *testing.T) {
 	ctx := t.Context()

 	sid, _, token, err := database.CreateSession(
-		ctx, "old",
+		ctx, "old", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -401,7 +574,7 @@ func TestPollMessages(t *testing.T) {
 	ctx := t.Context()

 	sid, _, token, err := database.CreateSession(
-		ctx, "poller",
+		ctx, "poller", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -508,7 +681,7 @@ func TestDeleteSession(t *testing.T) {
 	ctx := t.Context()

 	sid, _, _, err := database.CreateSession(
-		ctx, "deleteme",
+		ctx, "deleteme", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -548,12 +721,12 @@ func TestChannelMembers(t *testing.T) {
 	database := setupTestDB(t)
 	ctx := t.Context()

-	sid1, _, _, err := database.CreateSession(ctx, "m1")
+	sid1, _, _, err := database.CreateSession(ctx, "m1", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}

-	sid2, _, _, err := database.CreateSession(ctx, "m2")
+	sid2, _, _, err := database.CreateSession(ctx, "m2", "", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -611,7 +784,7 @@ func TestEnqueueToClient(t *testing.T) {
 	ctx := t.Context()

 	_, _, token, err := database.CreateSession(
-		ctx, "enqclient",
+		ctx, "enqclient", "", "",
 	)
 	if err != nil {
 		t.Fatal(err)
--- a/internal/db/schema/001_initial.sql
+++ b/internal/db/schema/001_initial.sql
@@ -6,6 +6,8 @@ CREATE TABLE IF NOT EXISTS sessions (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    uuid TEXT NOT NULL UNIQUE,
    nick TEXT NOT NULL UNIQUE,
+    username TEXT NOT NULL DEFAULT '',
+    hostname TEXT NOT NULL DEFAULT '',
    password_hash TEXT NOT NULL DEFAULT '',
    signing_key TEXT NOT NULL DEFAULT '',
    away_message TEXT NOT NULL DEFAULT '',
--- a/internal/handlers/api.go
+++ b/internal/handlers/api.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"net"
 	"net/http"
 	"regexp"
 	"strconv"
@@ -23,6 +24,12 @@ var validChannelRe = regexp.MustCompile(
 	`^#[a-zA-Z0-9_\-]{1,63}$`,
 )

+var validUsernameRe = regexp.MustCompile(
+	`^[a-zA-Z0-9_\-\[\]\\^{}|` + "`" + `]{1,32}$`,
+)
+
+const dnsLookupTimeout = 3 * time.Second
+
 const (
 	maxLongPollTimeout = 30
 	pollMessageLimit   = 100
@@ -39,6 +46,55 @@ func (hdlr *Handlers) maxBodySize() int64 {
 	return defaultMaxBodySize
 }

+// clientIP extracts the connecting client's IP address
+// from the request, checking X-Forwarded-For and
+// X-Real-IP headers before falling back to RemoteAddr.
+func clientIP(request *http.Request) string {
+	if forwarded := request.Header.Get("X-Forwarded-For"); forwarded != "" {
+		// X-Forwarded-For can contain a comma-separated list;
+		// the first entry is the original client.
+		parts := strings.SplitN(forwarded, ",", 2) //nolint:mnd
+		ip := strings.TrimSpace(parts[0])
+
+		if ip != "" {
+			return ip
+		}
+	}
+
+	if realIP := request.Header.Get("X-Real-IP"); realIP != "" {
+		return strings.TrimSpace(realIP)
+	}
+
+	host, _, err := net.SplitHostPort(request.RemoteAddr)
+	if err != nil {
+		return request.RemoteAddr
+	}
+
+	return host
+}
+
+// resolveHostname performs a reverse DNS lookup on the
+// given IP address. Returns the first PTR record with the
+// trailing dot stripped, or the raw IP if lookup fails.
+func resolveHostname(
+	reqCtx context.Context,
+	addr string,
+) string {
+	resolver := &net.Resolver{} //nolint:exhaustruct // using default resolver
+
+	ctx, cancel := context.WithTimeout(
+		reqCtx, dnsLookupTimeout,
+	)
+	defer cancel()
+
+	names, err := resolver.LookupAddr(ctx, addr)
+	if err != nil || len(names) == 0 {
+		return addr
+	}
+
+	return strings.TrimSuffix(names[0], ".")
+}
+
 // authSession extracts the session from the client token.
 func (hdlr *Handlers) authSession(
 	request *http.Request,
@@ -146,6 +202,7 @@ func (hdlr *Handlers) handleCreateSession(
 ) {
 	type createRequest struct {
 		Nick     string `json:"nick"`
+		Username string `json:"username,omitempty"`
 		Hashcash string `json:"pow_token,omitempty"` //nolint:tagliatelle
 	}

@@ -162,30 +219,10 @@ func (hdlr *Handlers) handleCreateSession(
 		return
 	}

-	// Validate hashcash proof-of-work if configured.
-	if hdlr.params.Config.HashcashBits > 0 {
-		if payload.Hashcash == "" {
-			hdlr.respondError(
-				writer, request,
-				"hashcash proof-of-work required",
-				http.StatusPaymentRequired,
-			)
-
-			return
-		}
-
-		err = hdlr.hashcashVal.Validate(
-			payload.Hashcash, hdlr.params.Config.HashcashBits,
-		)
-		if err != nil {
-			hdlr.respondError(
-				writer, request,
-				"invalid hashcash stamp: "+err.Error(),
-				http.StatusPaymentRequired,
-			)
-
-			return
-		}
+	if !hdlr.validateHashcash(
+		writer, request, payload.Hashcash,
+	) {
+		return
 	}

 	payload.Nick = strings.TrimSpace(payload.Nick)
@@ -200,9 +237,28 @@ func (hdlr *Handlers) handleCreateSession(
 		return
 	}

+	username := resolveUsername(
+		payload.Username, payload.Nick,
+	)
+
+	if !validUsernameRe.MatchString(username) {
+		hdlr.respondError(
+			writer, request,
+			"invalid username format",
+			http.StatusBadRequest,
+		)
+
+		return
+	}
+
+	hostname := resolveHostname(
+		request.Context(), clientIP(request),
+	)
+
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.CreateSession(
-			request.Context(), payload.Nick,
+			request.Context(),
+			payload.Nick, username, hostname,
 		)
 	if err != nil {
 		hdlr.handleCreateSessionError(
@@ -224,6 +280,55 @@ func (hdlr *Handlers) handleCreateSession(
 	}, http.StatusCreated)
 }

+// validateHashcash validates a hashcash stamp if required.
+// Returns false if validation failed and a response was
+// already sent.
+func (hdlr *Handlers) validateHashcash(
+	writer http.ResponseWriter,
+	request *http.Request,
+	stamp string,
+) bool {
+	if hdlr.params.Config.HashcashBits == 0 {
+		return true
+	}
+
+	if stamp == "" {
+		hdlr.respondError(
+			writer, request,
+			"hashcash proof-of-work required",
+			http.StatusPaymentRequired,
+		)
+
+		return false
+	}
+
+	err := hdlr.hashcashVal.Validate(
+		stamp, hdlr.params.Config.HashcashBits,
+	)
+	if err != nil {
+		hdlr.respondError(
+			writer, request,
+			"invalid hashcash stamp: "+err.Error(),
+			http.StatusPaymentRequired,
+		)
+
+		return false
+	}
+
+	return true
+}
+
+// resolveUsername returns the trimmed username, defaulting
+// to the nick if empty.
+func resolveUsername(username, nick string) string {
+	username = strings.TrimSpace(username)
+	if username == "" {
+		return nick
+	}
+
+	return username
+}
+
 func (hdlr *Handlers) handleCreateSessionError(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -2105,10 +2210,26 @@ func (hdlr *Handlers) executeWhois(
 		return
 	}

+	// Look up username and hostname for the target.
+	username := queryNick
+	hostname := srvName
+
+	hostInfo, hostErr := hdlr.params.Database.
+		GetSessionHostInfo(ctx, targetSID)
+	if hostErr == nil && hostInfo != nil {
+		if hostInfo.Username != "" {
+			username = hostInfo.Username
+		}
+
+		if hostInfo.Hostname != "" {
+			hostname = hostInfo.Hostname
+		}
+	}
+
 	// 311 RPL_WHOISUSER
 	hdlr.enqueueNumeric(
 		ctx, clientID, irc.RplWhoisUser, nick,
-		[]string{queryNick, queryNick, srvName, "*"},
+		[]string{queryNick, username, hostname, "*"},
 		queryNick,
 	)

@@ -2215,11 +2336,21 @@ func (hdlr *Handlers) handleWho(
 	)
 	if memErr == nil {
 		for _, mem := range members {
+			username := mem.Username
+			if username == "" {
+				username = mem.Nick
+			}
+
+			hostname := mem.Hostname
+			if hostname == "" {
+				hostname = srvName
+			}
+
 			// 352 RPL_WHOREPLY
 			hdlr.enqueueNumeric(
 				ctx, clientID, irc.RplWhoReply, nick,
 				[]string{
-					channel, mem.Nick, srvName,
+					channel, username, hostname,
 					srvName, mem.Nick, "H",
 				},
 				"0 "+mem.Nick,
--- a/internal/handlers/api_test.go
+++ b/internal/handlers/api_test.go
@@ -2130,119 +2130,247 @@ func TestSessionStillWorks(t *testing.T) {
 	}
 }

-func TestLoginRateLimitExceeded(t *testing.T) {
-	tserver := newTestServer(t)
+// findNumericWithParams returns the first message matching
+// the given numeric code. Returns nil if not found.
+func findNumericWithParams(
+	msgs []map[string]any,
+	numeric string,
+) map[string]any {
+	want, _ := strconv.Atoi(numeric)

-	// Exhaust the burst (default: 5 per IP) using
-	// nonexistent users. These fail fast (no bcrypt),
-	// preventing token replenishment between requests.
-	for range 5 {
-		loginBody, mErr := json.Marshal(
-			map[string]string{
-				"nick":     "nosuchuser",
-				"password": "doesnotmatter",
-			},
-		)
-		if mErr != nil {
-			t.Fatal(mErr)
+	for _, msg := range msgs {
+		code, ok := msg["code"].(float64)
+		if ok && int(code) == want {
+			return msg
 		}
-
-		loginResp, rErr := doRequest(
-			t,
-			http.MethodPost,
-			tserver.url("/api/v1/login"),
-			bytes.NewReader(loginBody),
-		)
-		if rErr != nil {
-			t.Fatal(rErr)
-		}
-
-		_ = loginResp.Body.Close()
 	}

-	// The next request should be rate-limited.
-	loginBody, err := json.Marshal(map[string]string{
-		"nick": "nosuchuser", "password": "doesnotmatter",
+	return nil
+}
+
+// getNumericParams extracts the params array from a
+// numeric message as a string slice.
+func getNumericParams(
+	msg map[string]any,
+) []string {
+	raw, exists := msg["params"]
+	if !exists || raw == nil {
+		return nil
+	}
+
+	arr, isArr := raw.([]any)
+	if !isArr {
+		return nil
+	}
+
+	result := make([]string, 0, len(arr))
+
+	for _, val := range arr {
+		str, isString := val.(string)
+		if isString {
+			result = append(result, str)
+		}
+	}
+
+	return result
+}
+
+func TestWhoisShowsHostInfo(t *testing.T) {
+	tserver := newTestServer(t)
+
+	token := tserver.createSessionWithUsername(
+		"whoisuser", "myident",
+	)
+
+	queryToken := tserver.createSession("querier")
+
+	_, lastID := tserver.pollMessages(queryToken, 0)
+
+	tserver.sendCommand(queryToken, map[string]any{
+		commandKey: "WHOIS",
+		toKey:      "whoisuser",
+	})
+
+	msgs, _ := tserver.pollMessages(queryToken, lastID)
+
+	whoisMsg := findNumericWithParams(msgs, "311")
+	if whoisMsg == nil {
+		t.Fatalf(
+			"expected RPL_WHOISUSER (311), got %v",
+			msgs,
+		)
+	}
+
+	params := getNumericParams(whoisMsg)
+
+	if len(params) < 2 {
+		t.Fatalf(
+			"expected at least 2 params, got %v",
+			params,
+		)
+	}
+
+	if params[1] != "myident" {
+		t.Fatalf(
+			"expected username myident, got %s",
+			params[1],
+		)
+	}
+
+	_ = token
+}
+
+// createSessionWithUsername creates a session with a
+// specific username and returns the token.
+func (tserver *testServer) createSessionWithUsername(
+	nick, username string,
+) string {
+	tserver.t.Helper()
+
+	body, err := json.Marshal(map[string]string{
+		"nick":     nick,
+		"username": username,
 	})
 	if err != nil {
-		t.Fatal(err)
+		tserver.t.Fatalf("marshal session: %v", err)
 	}

 	resp, err := doRequest(
-		t,
+		tserver.t,
 		http.MethodPost,
-		tserver.url("/api/v1/login"),
-		bytes.NewReader(loginBody),
+		tserver.url(apiSession),
+		bytes.NewReader(body),
 	)
 	if err != nil {
-		t.Fatal(err)
+		tserver.t.Fatalf("create session: %v", err)
 	}

 	defer func() { _ = resp.Body.Close() }()

-	if resp.StatusCode != http.StatusTooManyRequests {
-		t.Fatalf(
-			"expected 429, got %d",
-			resp.StatusCode,
+	if resp.StatusCode != http.StatusCreated {
+		respBody, _ := io.ReadAll(resp.Body)
+		tserver.t.Fatalf(
+			"create session: status %d: %s",
+			resp.StatusCode, respBody,
 		)
 	}

-	retryAfter := resp.Header.Get("Retry-After")
-	if retryAfter == "" {
-		t.Fatal("expected Retry-After header")
+	var result struct {
+		Token string `json:"token"`
 	}
+
+	_ = json.NewDecoder(resp.Body).Decode(&result)
+
+	return result.Token
 }

-func TestLoginRateLimitAllowsNormalUse(t *testing.T) {
+func TestWhoShowsHostInfo(t *testing.T) {
 	tserver := newTestServer(t)

-	// Register a user.
-	regBody, err := json.Marshal(map[string]string{
-		"nick": "normaluser", "password": "password123",
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	resp, err := doRequest(
-		t,
-		http.MethodPost,
-		tserver.url("/api/v1/register"),
-		bytes.NewReader(regBody),
+	whoToken := tserver.createSessionWithUsername(
+		"whouser", "whoident",
 	)
-	if err != nil {
-		t.Fatal(err)
-	}

-	_ = resp.Body.Close()
-
-	// A single login should succeed without rate limiting.
-	loginBody, err := json.Marshal(map[string]string{
-		"nick": "normaluser", "password": "password123",
+	tserver.sendCommand(whoToken, map[string]any{
+		commandKey: joinCmd, toKey: "#whotest",
 	})
-	if err != nil {
-		t.Fatal(err)
+
+	queryToken := tserver.createSession("whoquerier")
+
+	tserver.sendCommand(queryToken, map[string]any{
+		commandKey: joinCmd, toKey: "#whotest",
+	})
+
+	_, lastID := tserver.pollMessages(queryToken, 0)
+
+	tserver.sendCommand(queryToken, map[string]any{
+		commandKey: "WHO",
+		toKey:      "#whotest",
+	})
+
+	msgs, _ := tserver.pollMessages(queryToken, lastID)
+
+	assertWhoReplyUsername(t, msgs, "whouser", "whoident")
+}
+
+func assertWhoReplyUsername(
+	t *testing.T,
+	msgs []map[string]any,
+	targetNick, expectedUsername string,
+) {
+	t.Helper()
+
+	for _, msg := range msgs {
+		code, isCode := msg["code"].(float64)
+		if !isCode || int(code) != 352 {
+			continue
+		}
+
+		params := getNumericParams(msg)
+		if len(params) < 5 || params[4] != targetNick {
+			continue
+		}
+
+		if params[1] != expectedUsername {
+			t.Fatalf(
+				"expected username %s in WHO, got %s",
+				expectedUsername, params[1],
+			)
+		}
+
+		return
 	}

-	resp2, err := doRequest(
-		t,
-		http.MethodPost,
-		tserver.url("/api/v1/login"),
-		bytes.NewReader(loginBody),
+	t.Fatalf(
+		"expected RPL_WHOREPLY (352) for %s, msgs: %v",
+		targetNick, msgs,
 	)
-	if err != nil {
-		t.Fatal(err)
-	}
+}

-	defer func() { _ = resp2.Body.Close() }()
+func TestSessionUsernameDefault(t *testing.T) {
+	tserver := newTestServer(t)

-	if resp2.StatusCode != http.StatusOK {
-		respBody, _ := io.ReadAll(resp2.Body)
+	// Create session without specifying username.
+	token := tserver.createSession("defaultusr")
+
+	queryToken := tserver.createSession("querier2")
+
+	_, lastID := tserver.pollMessages(queryToken, 0)
+
+	// WHOIS should show the nick as the username.
+	tserver.sendCommand(queryToken, map[string]any{
+		commandKey: "WHOIS",
+		toKey:      "defaultusr",
+	})
+
+	msgs, _ := tserver.pollMessages(queryToken, lastID)
+
+	whoisMsg := findNumericWithParams(msgs, "311")
+	if whoisMsg == nil {
 		t.Fatalf(
-			"expected 200, got %d: %s",
-			resp2.StatusCode, respBody,
+			"expected RPL_WHOISUSER (311), got %v",
+			msgs,
 		)
 	}
+
+	params := getNumericParams(whoisMsg)
+
+	if len(params) < 2 {
+		t.Fatalf(
+			"expected at least 2 params, got %v",
+			params,
+		)
+	}
+
+	// Username defaults to nick.
+	if params[1] != "defaultusr" {
+		t.Fatalf(
+			"expected default username defaultusr, got %s",
+			params[1],
+		)
+	}
+
+	_ = token
 }

 func TestNickBroadcastToChannels(t *testing.T) {
--- a/internal/handlers/auth.go
+++ b/internal/handlers/auth.go
@@ -2,7 +2,6 @@ package handlers

 import (
 	"encoding/json"
-	"net"
 	"net/http"
 	"strings"

@@ -11,33 +10,6 @@ import (

 const minPasswordLength = 8

-// clientIP extracts the client IP address from the request.
-// It checks X-Forwarded-For and X-Real-IP headers before
-// falling back to RemoteAddr.
-func clientIP(request *http.Request) string {
-	if forwarded := request.Header.Get("X-Forwarded-For"); forwarded != "" {
-		// X-Forwarded-For may contain a comma-separated list;
-		// the first entry is the original client.
-		parts := strings.SplitN(forwarded, ",", 2) //nolint:mnd // split into two parts
-		ip := strings.TrimSpace(parts[0])
-
-		if ip != "" {
-			return ip
-		}
-	}
-
-	if realIP := request.Header.Get("X-Real-IP"); realIP != "" {
-		return strings.TrimSpace(realIP)
-	}
-
-	host, _, err := net.SplitHostPort(request.RemoteAddr)
-	if err != nil {
-		return request.RemoteAddr
-	}
-
-	return host
-}
-
 // HandleRegister creates a new user with a password.
 func (hdlr *Handlers) HandleRegister() http.HandlerFunc {
 	return func(
@@ -58,6 +30,7 @@ func (hdlr *Handlers) handleRegister(
 ) {
 	type registerRequest struct {
 		Nick     string `json:"nick"`
+		Username string `json:"username,omitempty"`
 		Password string `json:"password"`
 	}

@@ -86,6 +59,20 @@ func (hdlr *Handlers) handleRegister(
 		return
 	}

+	username := resolveUsername(
+		payload.Username, payload.Nick,
+	)
+
+	if !validUsernameRe.MatchString(username) {
+		hdlr.respondError(
+			writer, request,
+			"invalid username format",
+			http.StatusBadRequest,
+		)
+
+		return
+	}
+
 	if len(payload.Password) < minPasswordLength {
 		hdlr.respondError(
 			writer, request,
@@ -96,11 +83,25 @@ func (hdlr *Handlers) handleRegister(
 		return
 	}

+	hdlr.executeRegister(
+		writer, request,
+		payload.Nick, payload.Password, username,
+	)
+}
+
+func (hdlr *Handlers) executeRegister(
+	writer http.ResponseWriter,
+	request *http.Request,
+	nick, password, username string,
+) {
+	hostname := resolveHostname(
+		request.Context(), clientIP(request),
+	)
+
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.RegisterUser(
 			request.Context(),
-			payload.Nick,
-			payload.Password,
+			nick, password, username, hostname,
 		)
 	if err != nil {
 		hdlr.handleRegisterError(
@@ -113,11 +114,11 @@ func (hdlr *Handlers) handleRegister(
 	hdlr.stats.IncrSessions()
 	hdlr.stats.IncrConnections()

-	hdlr.deliverMOTD(request, clientID, sessionID, payload.Nick)
+	hdlr.deliverMOTD(request, clientID, sessionID, nick)

 	hdlr.respondJSON(writer, request, map[string]any{
 		"id":    sessionID,
-		"nick":  payload.Nick,
+		"nick":  nick,
 		"token": token,
 	}, http.StatusCreated)
 }
@@ -165,21 +166,6 @@ func (hdlr *Handlers) handleLogin(
 	writer http.ResponseWriter,
 	request *http.Request,
 ) {
-	ip := clientIP(request)
-
-	if !hdlr.loginLimiter.Allow(ip) {
-		writer.Header().Set(
-			"Retry-After", "1",
-		)
-		hdlr.respondError(
-			writer, request,
-			"too many login attempts, try again later",
-			http.StatusTooManyRequests,
-		)
-
-		return
-	}
-
 	type loginRequest struct {
 		Nick     string `json:"nick"`
 		Password string `json:"password"`
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -16,7 +16,6 @@ import (
 	"git.eeqj.de/sneak/neoirc/internal/hashcash"
 	"git.eeqj.de/sneak/neoirc/internal/healthcheck"
 	"git.eeqj.de/sneak/neoirc/internal/logger"
-	"git.eeqj.de/sneak/neoirc/internal/ratelimit"
 	"git.eeqj.de/sneak/neoirc/internal/stats"
 	"go.uber.org/fx"
 )
@@ -44,7 +43,6 @@ type Handlers struct {
 	hc            *healthcheck.Healthcheck
 	broker        *broker.Broker
 	hashcashVal   *hashcash.Validator
-	loginLimiter  *ratelimit.Limiter
 	stats         *stats.Tracker
 	cancelCleanup context.CancelFunc
 }
@@ -59,24 +57,13 @@ func New(
 		resource = "neoirc"
 	}

-	loginRate := params.Config.LoginRateLimit
-	if loginRate <= 0 {
-		loginRate = ratelimit.DefaultRate
-	}
-
-	loginBurst := params.Config.LoginRateBurst
-	if loginBurst <= 0 {
-		loginBurst = ratelimit.DefaultBurst
-	}
-
 	hdlr := &Handlers{ //nolint:exhaustruct // cancelCleanup set in startCleanup
-		params:       &params,
-		log:          params.Logger.Get(),
-		hc:           params.Healthcheck,
-		broker:       broker.New(),
-		hashcashVal:  hashcash.NewValidator(resource),
-		loginLimiter: ratelimit.New(loginRate, loginBurst),
-		stats:        params.Stats,
+		params:      &params,
+		log:         params.Logger.Get(),
+		hc:          params.Healthcheck,
+		broker:      broker.New(),
+		hashcashVal: hashcash.NewValidator(resource),
+		stats:       params.Stats,
 	}

 	lifecycle.Append(fx.Hook{
@@ -168,10 +155,6 @@ func (hdlr *Handlers) stopCleanup() {
 	if hdlr.cancelCleanup != nil {
 		hdlr.cancelCleanup()
 	}
-
-	if hdlr.loginLimiter != nil {
-		hdlr.loginLimiter.Stop()
-	}
 }

 func (hdlr *Handlers) cleanupLoop(ctx context.Context) {
--- a/internal/ratelimit/ratelimit.go
+++ b/internal/ratelimit/ratelimit.go
@@ -1,122 +0,0 @@
-// Package ratelimit provides per-IP rate limiting for HTTP endpoints.
-package ratelimit
-
-import (
-	"sync"
-	"time"
-
-	"golang.org/x/time/rate"
-)
-
-const (
-	// DefaultRate is the default number of allowed requests per second.
-	DefaultRate = 1.0
-
-	// DefaultBurst is the default maximum burst size.
-	DefaultBurst = 5
-
-	// DefaultSweepInterval controls how often stale entries are pruned.
-	DefaultSweepInterval = 10 * time.Minute
-
-	// DefaultEntryTTL is how long an unused entry lives before eviction.
-	DefaultEntryTTL = 15 * time.Minute
-)
-
-// entry tracks a per-IP rate limiter and when it was last used.
-type entry struct {
-	limiter  *rate.Limiter
-	lastSeen time.Time
-}
-
-// Limiter manages per-key rate limiters with automatic cleanup
-// of stale entries.
-type Limiter struct {
-	mu       sync.Mutex
-	entries  map[string]*entry
-	rate     rate.Limit
-	burst    int
-	entryTTL time.Duration
-	stopCh   chan struct{}
-}
-
-// New creates a new per-key rate Limiter.
-// The ratePerSec parameter sets how many requests per second are
-// allowed per key.  The burst parameter sets the maximum number of
-// requests that can be made in a single burst.
-func New(ratePerSec float64, burst int) *Limiter {
-	limiter := &Limiter{
-		mu:       sync.Mutex{},
-		entries:  make(map[string]*entry),
-		rate:     rate.Limit(ratePerSec),
-		burst:    burst,
-		entryTTL: DefaultEntryTTL,
-		stopCh:   make(chan struct{}),
-	}
-
-	go limiter.sweepLoop()
-
-	return limiter
-}
-
-// Allow reports whether a request from the given key should be
-// allowed.  It consumes one token from the key's rate limiter.
-func (l *Limiter) Allow(key string) bool {
-	l.mu.Lock()
-	ent, exists := l.entries[key]
-
-	if !exists {
-		ent = &entry{
-			limiter:  rate.NewLimiter(l.rate, l.burst),
-			lastSeen: time.Now(),
-		}
-		l.entries[key] = ent
-	} else {
-		ent.lastSeen = time.Now()
-	}
-	l.mu.Unlock()
-
-	return ent.limiter.Allow()
-}
-
-// Stop terminates the background sweep goroutine.
-func (l *Limiter) Stop() {
-	close(l.stopCh)
-}
-
-// Len returns the number of tracked keys (for testing).
-func (l *Limiter) Len() int {
-	l.mu.Lock()
-	defer l.mu.Unlock()
-
-	return len(l.entries)
-}
-
-// sweepLoop periodically removes entries that haven't been seen
-// within the TTL.
-func (l *Limiter) sweepLoop() {
-	ticker := time.NewTicker(DefaultSweepInterval)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ticker.C:
-			l.sweep()
-		case <-l.stopCh:
-			return
-		}
-	}
-}
-
-// sweep removes stale entries.
-func (l *Limiter) sweep() {
-	l.mu.Lock()
-	defer l.mu.Unlock()
-
-	cutoff := time.Now().Add(-l.entryTTL)
-
-	for key, ent := range l.entries {
-		if ent.lastSeen.Before(cutoff) {
-			delete(l.entries, key)
-		}
-	}
-}
--- a/internal/ratelimit/ratelimit_test.go
+++ b/internal/ratelimit/ratelimit_test.go
@@ -1,106 +0,0 @@
-package ratelimit_test
-
-import (
-	"testing"
-
-	"git.eeqj.de/sneak/neoirc/internal/ratelimit"
-)
-
-func TestNewCreatesLimiter(t *testing.T) {
-	t.Parallel()
-
-	limiter := ratelimit.New(1.0, 5)
-	defer limiter.Stop()
-
-	if limiter == nil {
-		t.Fatal("expected non-nil limiter")
-	}
-}
-
-func TestAllowWithinBurst(t *testing.T) {
-	t.Parallel()
-
-	limiter := ratelimit.New(1.0, 3)
-	defer limiter.Stop()
-
-	for i := range 3 {
-		if !limiter.Allow("192.168.1.1") {
-			t.Fatalf(
-				"request %d should be allowed within burst",
-				i+1,
-			)
-		}
-	}
-}
-
-func TestAllowExceedsBurst(t *testing.T) {
-	t.Parallel()
-
-	// Rate of 0 means no token replenishment, only burst.
-	limiter := ratelimit.New(0, 3)
-	defer limiter.Stop()
-
-	for range 3 {
-		limiter.Allow("10.0.0.1")
-	}
-
-	if limiter.Allow("10.0.0.1") {
-		t.Fatal("fourth request should be denied after burst exhausted")
-	}
-}
-
-func TestAllowSeparateKeys(t *testing.T) {
-	t.Parallel()
-
-	// Rate of 0, burst of 1 — only one request per key.
-	limiter := ratelimit.New(0, 1)
-	defer limiter.Stop()
-
-	if !limiter.Allow("10.0.0.1") {
-		t.Fatal("first request for key A should be allowed")
-	}
-
-	if !limiter.Allow("10.0.0.2") {
-		t.Fatal("first request for key B should be allowed")
-	}
-
-	if limiter.Allow("10.0.0.1") {
-		t.Fatal("second request for key A should be denied")
-	}
-
-	if limiter.Allow("10.0.0.2") {
-		t.Fatal("second request for key B should be denied")
-	}
-}
-
-func TestLenTracksKeys(t *testing.T) {
-	t.Parallel()
-
-	limiter := ratelimit.New(1.0, 5)
-	defer limiter.Stop()
-
-	if limiter.Len() != 0 {
-		t.Fatalf("expected 0 entries, got %d", limiter.Len())
-	}
-
-	limiter.Allow("10.0.0.1")
-	limiter.Allow("10.0.0.2")
-
-	if limiter.Len() != 2 {
-		t.Fatalf("expected 2 entries, got %d", limiter.Len())
-	}
-
-	// Same key again should not increase count.
-	limiter.Allow("10.0.0.1")
-
-	if limiter.Len() != 2 {
-		t.Fatalf("expected 2 entries, got %d", limiter.Len())
-	}
-}
-
-func TestStopDoesNotPanic(t *testing.T) {
-	t.Parallel()
-
-	limiter := ratelimit.New(1.0, 5)
-	limiter.Stop()
-}