From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BCE25C3DA64 for ; Wed, 31 Jul 2024 15:22:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sZB9D-0002tw-D2; Wed, 31 Jul 2024 11:21:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sZB9A-0002sQ-GA for qemu-devel@nongnu.org; Wed, 31 Jul 2024 11:21:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sZB98-0006ko-UZ for qemu-devel@nongnu.org; Wed, 31 Jul 2024 11:21:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722439306; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EuPadYHE5F9ga3dsED3ZBkxQlSPE7Tr0QIumyhMBOtw=; b=RJd5WL4svS/Fx2yp2niDnkQ4vRqOtQb8SR/3CfgY38VgLKMW+0yf/x0+0nnNRVO4xa9Jsh y7utvjeJG6VJeOWfsI+5xgvkTDuCURo9n2FKFGG1GBZunbo9RZHQcmDXkeGYSHTrYCG9qB StKdnVXunXx2xyEQPHLXkm4ET4Nqhkw= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-10-Xin_Be6lMqGykbnZ0aDwng-1; Wed, 31 Jul 2024 11:21:42 -0400 X-MC-Unique: Xin_Be6lMqGykbnZ0aDwng-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D073F18EB204; Wed, 31 Jul 2024 15:21:40 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.1]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7B0601955E89; Wed, 31 Jul 2024 15:21:38 +0000 (UTC) Date: Wed, 31 Jul 2024 17:21:36 +0200 From: Kevin Wolf To: Peter Maydell Cc: qemu-devel@nongnu.org, Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , John Snow , Stefan Weil , "Richard W.M. Jones" , Hanna Reitz , qemu-block@nongnu.org Subject: Re: [PATCH 7/7] block/ssh.c: Don't double-check that characters are hex digits Message-ID: References: <20240731143617.3391947-1-peter.maydell@linaro.org> <20240731143617.3391947-8-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240731143617.3391947-8-peter.maydell@linaro.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.126, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 31.07.2024 um 16:36 hat Peter Maydell geschrieben: > In compare_fingerprint() we effectively check whether the characters > in the fingerprint are valid hex digits twice: first we do so with > qemu_isxdigit(), but then the hex2decimal() function also has a code > path where it effectively detects an invalid digit and returns -1. > This causes Coverity to complain because it thinks that we might use > that -1 value in an expression where it would be an integer overflow. If it's a Coverity issue, I think you want to mention the CID, too. > Avoid the double-check of hex digit validity by testing the return > values from hex2decimal() rather than doing separate calls to > qemu_isxdigit(). > > Signed-off-by: Peter Maydell > --- > Could alternatively have put a g_assert_non_reached() in > hex2decimal(), but this seemed better to me. I don't like that hex2decimal() returns -1 when its result is unsigned, which is why you had to write the check as > 0xf rather than < 0. So in this sense, g_assert_non_reached() would look better to me. But we could also just change it to return UINT_MAX instead, which should be the same, just written in a less confusing way. > block/ssh.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/block/ssh.c b/block/ssh.c > index 27d582e0e3d..510dd208aba 100644 > --- a/block/ssh.c > +++ b/block/ssh.c > @@ -376,13 +376,15 @@ static int compare_fingerprint(const unsigned char *fingerprint, size_t len, > unsigned c; > > while (len > 0) { > + unsigned c0, c1; > while (*host_key_check == ':') > host_key_check++; > - if (!qemu_isxdigit(host_key_check[0]) || > - !qemu_isxdigit(host_key_check[1])) > + c0 = hex2decimal(host_key_check[0]); > + c1 = hex2decimal(host_key_check[1]); > + if (c0 > 0xf || c1 > 0xf) { > return 1; > - c = hex2decimal(host_key_check[0]) * 16 + > - hex2decimal(host_key_check[1]); > + } > + c = c0 * 16 + c1; > if (c - *fingerprint != 0) > return c - *fingerprint; > fingerprint++; Reviewed-by: Kevin Wolf