From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Wed, 03 Dec 2025 13:01:43 +0100 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1vQlYF-007VBY-2d for lore@lore.pengutronix.de; Wed, 03 Dec 2025 13:01:43 +0100 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1vQlYF-0008Us-73 for lore@pengutronix.de; Wed, 03 Dec 2025 13:01:43 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vrm8qM1LLdNW6W3f8hsF9pw5lbV041bLQB5siMDwCuw=; b=T3C5iFHaISluZVvWTULyGIODY9 BS+rsylBGTjTIFavTw+Pjj4UAoENNBv4WR4e2Q2jv9Q47GNDTVEeW6ZQEqyxj/567QRAxR0avHnZt 9XOUmRUO2ahMuuU1NpU2SEu6Se2TO4XwqQeWgYOjb1ceix3eeHzzRec60ZKfHsOA4ynF9fjlzQT9U OljcYTQLIuUn9nrWY0fKo5aHA55rZcBBaUwdUm/6x6WiF4I9P8DFMXPrnPqjn6iikFEAhljToCCJb IXZO2nuoekkcLyv6jchvYuBvS9QFJWalp7W+JF5689T0jAJ2fcKIPLrXYadgloa1p7vAlQLRgX68i ItRern9w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vQlXp-00000006XCt-3GNU; Wed, 03 Dec 2025 12:01:17 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vQlXn-00000006XCY-31WI for barebox@lists.infradead.org; Wed, 03 Dec 2025 12:01:16 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1vQlXl-0008MR-UC; Wed, 03 Dec 2025 13:01:14 +0100 Message-ID: <61c7405c-7d00-474a-8c9a-37b818965ad1@pengutronix.de> Date: Wed, 3 Dec 2025 13:01:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer , Jonas Rebmann Cc: BAREBOX References: <20251202-base64-bounds-v2-0-34d3716c3f55@pengutronix.de> <20251202-base64-bounds-v2-1-34d3716c3f55@pengutronix.de> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251203_040115_767434_37A64289 X-CRM114-Status: GOOD ( 22.83 ) 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: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::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.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.0 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH v2 1/2] lib: base64: Fix out-of-bounds potential by respecting dst_len X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) Hi Sascha, On 12/3/25 9:59 AM, Sascha Hauer wrote: > On Tue, Dec 02, 2025 at 10:22:44AM +0100, Jonas Rebmann wrote: >> __decode_base64 generally writes the input in 3 bytes increments, >> corresponding to 4 bytes increments in the base64 input buffer. This >> means that in order to respect dst_len as the size of the output buffer, >> the case of exceeding dst_len within a loop iteration must be >> considered. >> >> In such a case, refrain from writing the last one or two bytes if that >> write would be past dst_len. >> >> Signed-off-by: Jonas Rebmann >> --- >> lib/base64.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) > > I wonder if we should switch to the kernel functions from lib/base64.c > instead. They look much more straight forward than the busybox based > implementation. Just need to take care to support base64url, which is needed for the JSON web token support. Cheers, Ahmad > > Sascha > >> >> diff --git a/lib/base64.c b/lib/base64.c >> index d5ab217528..3e29f0a56c 100644 >> --- a/lib/base64.c >> +++ b/lib/base64.c >> @@ -163,19 +163,19 @@ static int __decode_base64(char *p_dst, int dst_len, const char *src, bool url) >> */ >> if (count > 1) >> *dst++ = six_bit[0] << 2 | six_bit[1] >> 4; >> - if (count > 2) >> + if (count > 2 && dst_len > 1) >> *dst++ = six_bit[1] << 4 | six_bit[2] >> 2; >> - if (count > 3) >> + if (count > 3 && dst_len > 2) >> *dst++ = six_bit[2] << 6 | six_bit[3]; >> + /* last character was "=" */ >> + if (count != 0) >> + length += min(count - 1, dst_len); >> /* >> * Note that if we decode "AA==" and ate first '=', >> * we just decoded one char (count == 2) and now we'll >> * do the loop once more to decode second '='. >> */ >> dst_len -= count-1; >> - /* last character was "=" */ >> - if (count != 0) >> - length += count - 1; >> } >> ret: >> p_dst = dst; >> >> -- >> 2.51.2.535.g419c72cb8a >> >> > -- 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 |