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Use checked type assertions and nil-check client session messages #189

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8a8839e
Guard nil payload in decoded session messages on the client.
fereidani Jun 24, 2026
b8b619a
Use checked type assertions when parsing ICMP messages.
fereidani Jun 24, 2026
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28 changes: 26 additions & 2 deletions client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,13 @@ func handshakeWithServerSync(test *ethrTest, conn net.Conn) (startTime time.Time
err = os.ErrInvalid
return
}
// A SyncReady whose payload was omitted decodes with a nil SyncReady
// pointer; the Type check above does not prove otherwise.
if ethrMsg.SyncReady == nil {
ui.printDbg("Received SyncReady message with nil payload from Ethr server.")
err = os.ErrInvalid
return
}
delayNs := ethrMsg.SyncReady.DelayNs

if delayNs == 0 {
Expand Down Expand Up @@ -335,6 +342,14 @@ func tcpRunBandwidthTestSync(test *ethrTest, toStop chan int, duration time.Dura
toStop <- disconnect
return
}
// A SyncReady whose payload was omitted decodes with a nil SyncReady
// pointer; the Type check above does not prove otherwise.
if ethrMsg.SyncReady == nil {
ui.printErr("Received SyncReady message with nil payload from server.")
controlConn.Close()
toStop <- disconnect
return
}
delayNs := ethrMsg.SyncReady.DelayNs
rtt := recvTime.Sub(sendTime)
rttNs := rtt.Nanoseconds()
Expand Down Expand Up @@ -1115,7 +1130,12 @@ func icmpRecvMsg(c net.PacketConn, proto EthrProtocol, timeout time.Duration, ne
continue
}
if icmpMsg.Type == ipv4.ICMPTypeTimeExceeded || icmpMsg.Type == ipv6.ICMPTypeTimeExceeded {
body := icmpMsg.Body.(*icmp.TimeExceeded).Data
te, ok := icmpMsg.Body.(*icmp.TimeExceeded)
if !ok {
ui.printDbg("Received TimeExceeded ICMP message with unexpected body type.")
continue
}
body := te.Data
index := bytes.Index(body, neededSig[:4])
if index > 0 {
if proto == TCP {
Expand Down Expand Up @@ -1144,7 +1164,11 @@ func icmpRecvMsg(c net.PacketConn, proto EthrProtocol, timeout time.Duration, ne
}

if proto == ICMP && (icmpMsg.Type == ipv4.ICMPTypeEchoReply || icmpMsg.Type == ipv6.ICMPTypeEchoReply) {
echo := icmpMsg.Body.(*icmp.Echo)
echo, ok := icmpMsg.Body.(*icmp.Echo)
if !ok {
ui.printDbg("Received EchoReply ICMP message with unexpected body type.")
continue
}
ethrUnused(echo)
b, _ := icmpMsg.Body.Marshal(1)
if string(b[4:]) != string(neededIcmpBody) {
Expand Down