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Message-ID: <Y71UCProYz73JVCW@hog> Date: Tue, 10 Jan 2023 13:03:20 +0100 From: Sabrina Dubroca <sd@...asysnail.net> To: Emeel Hakim <ehakim@...dia.com> Cc: "dsahern@...nel.org" <dsahern@...nel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Raed Salem <raeds@...dia.com> Subject: Re: [PATCH main 1/1] macsec: Fix Macsec replay protection 2023-01-10, 11:23:26 +0000, Emeel Hakim wrote: > > > > -----Original Message----- > > From: Sabrina Dubroca <sd@...asysnail.net> > > Sent: Tuesday, 10 January 2023 12:02 > > To: Emeel Hakim <ehakim@...dia.com> > > Cc: dsahern@...nel.org; netdev@...r.kernel.org; Raed Salem > > <raeds@...dia.com> > > Subject: Re: [PATCH main 1/1] macsec: Fix Macsec replay protection > > > > External email: Use caution opening links or attachments > > > > > > 2023-01-10, 10:02:19 +0200, ehakim@...dia.com wrote: > > > @@ -1516,7 +1515,7 @@ static int macsec_parse_opt(struct link_util *lu, int > > argc, char **argv, > > > addattr_l(n, MACSEC_BUFLEN, IFLA_MACSEC_ICV_LEN, > > > &cipher.icv_len, sizeof(cipher.icv_len)); > > > > > > - if (replay_protect != -1) { > > > + if (replay_protect) { > > > > This will silently break disabling replay protection on an existing device. This: > > > > Thanks for catching that. > > > ip link set macsec0 type macsec replay off > > > > would now appear to succeed but will not do anything. That's why I used an int with > > -1 in iproute, and a U8 netlink attribute rather a flag. > > > > I think this would be a better fix: > > > > if (replay_protect != -1) { > > - addattr32(n, MACSEC_BUFLEN, IFLA_MACSEC_WINDOW, window); > > + if (replay_protect) > > + addattr32(n, MACSEC_BUFLEN, IFLA_MACSEC_WINDOW, > > + window); > > addattr8(n, MACSEC_BUFLEN, IFLA_MACSEC_REPLAY_PROTECT, > > replay_protect); > > } > > > > Does that work for all your test cases? > > The main test case works however I wonder if it should be allowed to pass a window with replay off > for example: > ip link set macsec0 type macsec replay off window 32 > > because now this will silently ignore the window attribute > > a possible scenario: > we start with a macsec device with replay enabled and window set to 64 > now we perform: > ip link set macsec0 type macsec replay off window 32 > ip link set macsec0 type macsec replay on > > we expect to move to a 32-bit window but we silently failed to do so. > > what do you think? The kernel currently doesn't allow that. From macsec_validate_attr: if ((data[IFLA_MACSEC_REPLAY_PROTECT] && nla_get_u8(data[IFLA_MACSEC_REPLAY_PROTECT])) && !data[IFLA_MACSEC_WINDOW]) return -EINVAL; So we can set the size of the replay window, but it's ignored and will be overwritten when we enable replay protection. We could check for window != -1 instead of replay_protect before adding IFLA_MACSEC_WINDOW, and I think that should take care of both cases. > > > > > > addattr32(n, MACSEC_BUFLEN, IFLA_MACSEC_WINDOW, window); > > > addattr8(n, MACSEC_BUFLEN, IFLA_MACSEC_REPLAY_PROTECT, > > > replay_protect); > > > > -- > > Sabrina > -- Sabrina
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