fix #1312

conventional.yaml

@@ -269,6 +269,12 @@ server:
         # whether to enable IP cloaking
         enabled: false
 
+        # whether to use these cloak settings (specifically, `netname` and `num-bits`)
+        # to produce unique hostnames for always-on clients. you can enable this even if
+        # you disabled IP cloaking for normal clients above. if this is disabled,
+        # always-on clients will all have an identical hostname (the server name).
+        enabled-for-always-on: true
+
         # fake TLD at the end of the hostname, e.g., pwbs2ui4377257x8.irc
         # you may want to use your network name here
         netname: "irc"

default.yaml

@@ -297,6 +297,12 @@ server:
         # whether to enable IP cloaking
         enabled: true
 
+        # whether to use these cloak settings (specifically, `netname` and `num-bits`)
+        # to produce unique hostnames for always-on clients. you can enable this even if
+        # you disabled IP cloaking for normal clients above. if this is disabled,
+        # always-on clients will all have an identical hostname (the server name).
+        enabled-for-always-on: true
+
         # fake TLD at the end of the hostname, e.g., pwbs2ui4377257x8.irc
         # you may want to use your network name here
         netname: "irc"

irc/client.go

@@ -411,6 +411,11 @@ func (server *Server) AddAlwaysOnClient(account ClientAccount, chnames []string,
 		lastSeen = map[string]time.Time{"": now}
 	}
 
+	hostname := server.name
+	if config.Server.Cloaks.EnabledForAlwaysOn {
+		hostname = config.Server.Cloaks.ComputeAccountCloak(account.Name)
+	}
+
 	client := &Client{
 		lastSeen:   lastSeen,
 		lastActive: now,
@@ -419,9 +424,8 @@ func (server *Server) AddAlwaysOnClient(account ClientAccount, chnames []string,
 		languages:  server.Languages().Default(),
 		server:     server,
 
-		// TODO figure out how to set these on reattach?
 		username:    "~user",
-		rawHostname: server.name,
+		rawHostname: hostname,
 		realIP:      utils.IPv4LoopbackAddress,
 
 		alwaysOn: true,

irc/cloaks/cloak_test.go

@@ -104,3 +104,25 @@ func BenchmarkCloaks(b *testing.B) {
 		config.ComputeCloak(v6ip)
 	}
 }
+
+func TestAccountCloak(t *testing.T) {
+	config := cloakConfForTesting()
+
+	// just assert that we get all distinct values
+	assertEqual(config.ComputeAccountCloak("shivaram"), "8yu8kunudb45ztxm.oragono", t)
+	assertEqual(config.ComputeAccountCloak("dolph🐬n"), "hhgeqsvzeagv3wjw.oragono", t)
+	assertEqual(config.ComputeAccountCloak("SHIVARAM"), "bgx32x4r7qzih4uh.oragono", t)
+	assertEqual(config.ComputeAccountCloak("ed"), "j5autmgxtdjdyzf4.oragono", t)
+}
+
+func TestAccountCloakCollisions(t *testing.T) {
+	config := cloakConfForTesting()
+
+	v4ip := easyParseIP("97.97.97.97")
+	v4cloak := config.ComputeCloak(v4ip)
+	// "aaaa" is the same bytestring as 97.97.97.97
+	aaaacloak := config.ComputeAccountCloak("aaaa")
+	if v4cloak == aaaacloak {
+		t.Errorf("cloak collision between 97.97.97.97 and aaaa: %s", v4cloak)
+	}
+}

irc/cloaks/cloaks.go

@@ -12,12 +12,13 @@ import (
 )
 
 type CloakConfig struct {
-	Enabled           bool
-	Netname           string
-	CidrLenIPv4       int    `yaml:"cidr-len-ipv4"`
-	CidrLenIPv6       int    `yaml:"cidr-len-ipv6"`
-	NumBits           int    `yaml:"num-bits"`
-	LegacySecretValue string `yaml:"secret"`
+	Enabled            bool
+	EnabledForAlwaysOn bool `yaml:"enabled-for-always-on"`
+	Netname            string
+	CidrLenIPv4        int    `yaml:"cidr-len-ipv4"`
+	CidrLenIPv6        int    `yaml:"cidr-len-ipv6"`
+	NumBits            int    `yaml:"num-bits"`
+	LegacySecretValue  string `yaml:"secret"`
 
 	secret   string
 	numBytes int
@@ -26,14 +27,10 @@ type CloakConfig struct {
 }
 
 func (cloakConfig *CloakConfig) Initialize() {
-	if !cloakConfig.Enabled {
-		return
-	}
-
 	// sanity checks:
 	numBits := cloakConfig.NumBits
 	if 0 == numBits {
-		numBits = 80
+		numBits = 64
 	} else if 256 < numBits {
 		numBits = 256
 	}
@@ -69,12 +66,30 @@ func (config *CloakConfig) ComputeCloak(ip net.IP) string {
 	} else {
 		masked = ip.Mask(config.ipv6Mask)
 	}
+	return config.macAndCompose(masked)
+}
+
+func (config *CloakConfig) macAndCompose(b []byte) string {
 	// SHA3(K || M):
 	// https://crypto.stackexchange.com/questions/17735/is-hmac-needed-for-a-sha-3-based-mac
-	input := make([]byte, len(config.secret)+len(masked))
+	input := make([]byte, len(config.secret)+len(b))
 	copy(input, config.secret[:])
-	copy(input[len(config.secret):], masked)
+	copy(input[len(config.secret):], b)
 	digest := sha3.Sum512(input)
 	b32digest := utils.B32Encoder.EncodeToString(digest[:config.numBytes])
 	return fmt.Sprintf("%s.%s", b32digest, config.Netname)
 }
+
+func (config *CloakConfig) ComputeAccountCloak(accountName string) string {
+	// XXX don't bother checking EnabledForAlwaysOn, since if it's disabled,
+	// we need to use the server name which we don't have
+	if config.NumBits == 0 || config.secret == "" {
+		return config.Netname
+	}
+
+	// pad with 16 initial bytes of zeroes, avoiding any possibility of collision
+	// with a masked IP that could be an input to ComputeCloak:
+	paddedAccountName := make([]byte, 16+len(accountName))
+	copy(paddedAccountName[16:], accountName[:])
+	return config.macAndCompose(paddedAccountName)
+}

irc/server.go

@@ -599,9 +599,7 @@ func (server *Server) applyConfig(config *Config) (err error) {
 	// now that the datastore is initialized, we can load the cloak secret from it
 	// XXX this modifies config after the initial load, which is naughty,
 	// but there's no data race because we haven't done SetConfig yet
-	if config.Server.Cloaks.Enabled {
-		config.Server.Cloaks.SetSecret(LoadCloakSecret(server.store))
-	}
+	config.Server.Cloaks.SetSecret(LoadCloakSecret(server.store))
 
 	// activate the new config
 	server.SetConfig(config)