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Terminate on any unsupported version instead of sending code 2 #40

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Merged
markmnl merged 3 commits into from
Aug 25, 2026
Merged

Terminate on any unsupported version instead of sending code 2 #40

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8a14a9f
Terminate on unsupported challenge version instead of sending code 2
markmnl Aug 10, 2026
1187918
Terminate on any unsupported version, retire code 2
markmnl Aug 25, 2026
2cb0664
Merge branch 'main' into fix/terminate-unsupported-challenge
markmnl Aug 25, 2026
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15 changes: 6 additions & 9 deletions cmd/fmsgd/host.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,8 +33,10 @@ const (
InboxDirName = "in"
OutboxDirName = "out"

// Response codes (SPEC §9). 2 was "unsupported version"; unsupported
// versions now TERMINATE without responding (SPEC §10.3/§10.5), so it is
// never sent and is left unassigned to keep the numbering stable.
RejectCodeInvalid uint8 = 1
RejectCodeUnsupportedVersion uint8 = 2
RejectCodeUndisclosed uint8 = 3
RejectCodeTooBig uint8 = 4
RejectCodeInsufficentResources uint8 = 5
Expand Down Expand Up @@ -64,8 +66,6 @@ func responseCodeName(code uint8) string {
switch code {
case RejectCodeInvalid:
return "invalid"
case RejectCodeUnsupportedVersion:
return "unsupported version"
case RejectCodeUndisclosed:
return "undisclosed"
case RejectCodeTooBig:
Expand Down Expand Up @@ -693,15 +693,12 @@ func readVersionOrChallenge(c net.Conn, r *bufio.Reader, h *FMsgHeader) (bool, e
if challengeVersion == 1 {
return true, handleChallenge(c, r)
}
if err := sendCode(c, RejectCodeUnsupportedVersion); err != nil {
log.Printf("WARN: failed to send unsupported version response: %s", err)
}
// TERMINATE without responding (SPEC §10.3/§10.5): an unsupported
// version is one we do not know how to respond in.
return false, fmt.Errorf("unsupported challenge version: %d", challengeVersion)
}
if v != 1 {
if err := sendCode(c, RejectCodeUnsupportedVersion); err != nil {
log.Printf("WARN: failed to send unsupported version response: %s", err)
}
// TERMINATE without responding (SPEC §10.3/§10.5).
return false, fmt.Errorf("unsupported message version: %d", v)
}
h.Version = v
Expand Down
1 change: 0 additions & 1 deletion cmd/fmsgd/host_test.go
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Expand Up @@ -162,7 +162,6 @@ func TestResponseCodeName(t *testing.T) {
want string
}{
{RejectCodeInvalid, "invalid"},
{RejectCodeUnsupportedVersion, "unsupported version"},
{RejectCodeUndisclosed, "undisclosed"},
{RejectCodeTooBig, "too big"},
{RejectCodeInsufficentResources, "insufficient resources"},
Expand Down
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