* fix(panel): accept 2FA codes from adjacent TOTP windows
CheckUser compared only gotp.Now(), so a code submitted at the end of
its 30s window (or with slight client/server clock drift) failed with
'invalid 2fa code', while the immediate retry in the next window
succeeded. Accept current +/-1 window, the standard TOTP skew
tolerance.
Fixes MHSanaei/3x-ui#6535
* fix(panel): share TOTP skew tolerance with VerifyTwoFactorCode
Move the +/-1 window helper to internal/util/totp so both 2FA
acceptance points use it: login (CheckUser) and disable/rebind plus
username/password changes (VerifyTwoFactorCode). Also shrink comments
to the 2-line house rule and anchor the unit test mid-window to avoid
a step-boundary flake.
Addresses review on #6546 (MEDIUM + 2 LOWs).
* fix(sub): send stable X-HWID on external subscription fetch
A Master panel fetching a donor subscription sent no X-HWID, so an
HWID-limited donor rejected it with 404. Identify this panel with a
stable per-installation id (persisted in settings), occupying exactly
one donor device slot.
FixesMHSanaei/3x-ui#6559
* fix(sub): address review on external X-HWID
- Serialize first-time id creation with a mutex so concurrent
first fetches cannot mint two UUIDs.
- Fix goimports grouping for the new third-party import.
- Add externalSubSendHwid opt-out (default send); document it.
- Cover header send/omit with httptest in TestFetchSendsStableHwid.
* fix(sub): drop the SQL-only X-HWID opt-out
The externalSubSendHwid opt-out added in 227ed818 had no settings
field, CLI flag or docs, so an operator could only reach it by editing
the settings table by hand, while every cache-miss fetch paid a query
for it. CLAUDE.md rules out config knobs on a one-header fix.
Also drop the test assertions that only restated the 3x-ui-server-
prefix constant; TestFetchSendsStableHwid still goes red without the
header.
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Co-authored-by: sdhfsl <sdhfsl@users.noreply.github.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>
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