Behavision/server/internal/api/handlers_password.go

// Changing your own password.
//
// This did not exist, and the cost of that was measured rather than guessed:
// rotating three production accounts took a shell on the server, three round
// trips, and briefly left a PLATFORM ADMIN - the account that reads every
// company on the estate - with a password anyone watching could guess, because
// a placeholder in a pasted command was taken literally.
//
// A manager could always reset somebody ELSE's password, and a platform admin
// could be reset by nobody at all: they have no client, so the team routes are
// not theirs, and `provision user` on the host was the only way. For a product
// that puts accounts on shop-floor PCs and staff phones, "change my password"
// is not a feature, it is the thing that makes every other credential decision
// recoverable.
package api

import (
	"net/http"

	"github.com/loyaly/behavision-server/internal/auth"
)

// handleChangePassword is on `authed`, NOT `tenantOnly`.
//
// A session is not a company's data. A platform admin has no client and must
// still be able to change their own password - they are precisely the account
// for which there was no other route.
func (s *Server) handleChangePassword(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())

	var in ChangePassword
	if err := decode(w, r, &in); err != nil {
		badRequest(w, err.Error())
		return
	}

	// The CURRENT password is required, and that is the whole security
	// argument. An access token lives twelve hours and travels on shop-floor
	// devices; without this, anyone holding a stolen one could set a new
	// password and own the account permanently rather than for the rest of
	// the day.
	rec, err := s.Store.UserByEmail(r.Context(), p.Email)
	if err != nil {
		s.serverError(w, "change password", err)
		return
	}
	if !rec.Found || !auth.VerifyPassword(rec.PasswordHash, in.CurrentPassword) {
		// Deliberately not throttled separately: this needs a live session, so
		// it is not reachable by anyone guessing from outside, and the login
		// throttle already governs getting one.
		writeErr(w, http.StatusForbidden, "wrong_password",
			"That is not your current password.")
		return
	}
	if in.CurrentPassword == in.NewPassword {
		badRequest(w, "the new password is the same as the old one")
		return
	}

	hash, err := auth.HashPassword(in.NewPassword)
	if err != nil {
		// HashPassword enforces the length floor, and its message names it.
		badRequest(w, err.Error())
		return
	}
	if err := s.Store.SetUserPassword(r.Context(), p.UserID, hash); err != nil {
		s.serverError(w, "change password", err)
		return
	}

	// Every OTHER session goes, and the caller's stays. Somebody changing
	// their password because they think it is known must not have to guess
	// whether the change took effect on the device that already had it - and
	// must not be signed out of the one in their hand while they deal with it.
	revoked, err := s.Store.RevokeOtherSessions(r.Context(), p.UserID, p.SessionID)
	if err != nil {
		// The password IS changed. Reporting a failure here would tell the
		// user to try again, and the retry would fail on the current password
		// they just replaced.
		s.logf("change password: revoke other sessions: %v", err)
	}

	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "auth.change_password", Entity: "user", EntityID: p.UserID,
		Detail: map[string]any{"sessions_revoked": revoked},
	})
	writeJSON(w, http.StatusOK, map[string]any{
		"changed":          true,
		"sessions_revoked": revoked,
	})
}