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Mon, 16 May 2022 10:27:19 +0200 Received: from sha by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1nqW4V-0003dI-02; Mon, 16 May 2022 10:27:19 +0200 Date: Mon, 16 May 2022 10:27:18 +0200 To: Jules Maselbas Cc: barebox@lists.infradead.org Message-ID: <20220516082718.GJ25578@pengutronix.de> References: <20220512143726.21614-1-jmaselbas@kalray.eu> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220512143726.21614-1-jmaselbas@kalray.eu> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 10:27:09 up 46 days, 20:56, 77 users, load average: 0.45, 0.68, 0.53 User-Agent: Mutt/1.10.1 (2018-07-13) From: Sascha Hauer X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220516_012721_460131_5F59BB4C X-CRM114-Status: GOOD ( 32.39 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:e::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.8 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH v2] net: dns: Generate and verify transaction ID X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) On Thu, May 12, 2022 at 04:37:26PM +0200, Jules Maselbas wrote: > The transaction ID wasn't verified on received DNS responses, plus the > ID needs to be difficult to predict in order to avoid MitM (man in the > middle) being able to easily forge responses. > > The ID is generated from the time of the request, probably not strongly > unpredictable, this what musl does and it is considered to be enough. > > Signed-off-by: Jules Maselbas > --- > v2: fix the dns_req_id type to uint16_t, added pr_debug when incorrect id > is received, drop uses of the random32. > > net/dns.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) Applied, thanks Sascha > > diff --git a/net/dns.c b/net/dns.c > index 78588b96f..8b5e8d59e 100644 > --- a/net/dns.c > +++ b/net/dns.c > @@ -58,6 +58,7 @@ struct header { > > static struct net_connection *dns_con; > static uint64_t dns_timer_start; > +static uint16_t dns_req_id; > static int dns_state; > static IPaddr_t dns_ip; > > @@ -70,9 +71,12 @@ static int dns_send(const char *name) > unsigned char *p, *s, *fullname, *dotptr; > const unsigned char *domain; > > + /* generate "difficult" to predict transaction id */ > + dns_req_id = dns_timer_start + (dns_timer_start >> 16); > + > /* Prepare DNS packet header */ > header = (struct header *)packet; > - header->tid = 1; > + header->tid = htons(dns_req_id); > header->flags = htons(0x100); /* standard query */ > header->nqueries = htons(1); /* Just one query */ > header->nanswers = 0; > @@ -127,6 +131,12 @@ static void dns_recv(struct header *header, unsigned len) > > pr_debug("%s\n", __func__); > > + /* Only accept responses with the expected request id */ > + if (ntohs(header->tid) != dns_req_id) { > + pr_debug("DNS response with incorrect id\n"); > + return; > + } > + > /* We sent 1 query. We want to see more that 1 answer. */ > if (ntohs(header->nqueries) != 1) > return; > -- > 2.17.1 > > > _______________________________________________ > barebox mailing list > barebox@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/barebox > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox