From patchwork Fri Aug 2 19:26:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13751930 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 0F514C52D6F for ; Fri, 2 Aug 2024 19:42:57 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sZyAN-000286-4t; Fri, 02 Aug 2024 15:42:19 -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 1sZyAJ-00022e-RD for qemu-devel@nongnu.org; Fri, 02 Aug 2024 15:42:16 -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 1sZyAI-0006Ql-Ac for qemu-devel@nongnu.org; Fri, 02 Aug 2024 15:42:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722627733; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zujWLanYU65hRJrPq3mrZmUXtKznUN/BGwM9MRtRTtE=; b=WnceGgKZhlG25Pw9rVSme6oBxm6cDypgV38TLyZpUtUV2A7cCLmDNGakt+STBsWQlzYeby sxeiUoth8KgaYqaH7UOWgA8/X+rt3X9caox73NbUcEaTEGfXxhIFqJ86lU/FxzQSnto/im 5LzIjRhRCbpm90FBf8Lo7RZNhtltRwE= Received: from mx-prod-mc-04.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-18-R71nrcNcMwalGvZc5B7s5A-1; Fri, 02 Aug 2024 15:42:07 -0400 X-MC-Unique: R71nrcNcMwalGvZc5B7s5A-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 107B91955D5A; Fri, 2 Aug 2024 19:42:05 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.72]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7336F195605A; Fri, 2 Aug 2024 19:42:03 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, rjones@redhat.com, Vladimir Sementsov-Ogievskiy Subject: [PATCH 2/2] qemu-img: CVE-XXX Sanitize untrusted output from NBD server Date: Fri, 2 Aug 2024 14:26:06 -0500 Message-ID: <20240802194156.2131519-6-eblake@redhat.com> In-Reply-To: <20240802194156.2131519-4-eblake@redhat.com> References: <20240802194156.2131519-4-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@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=-0.124, 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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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 Error messages from an NBD server must be treated as untrusted; a malicious server can inject escape sequences to try and trigger RCE flaws via escape sequences to whatever terminal happens to be running qemu-img. The easiest solution is to sanitize the output with the same code we use to produce sanitized (pseudo-)JSON over QMP. Rich Jones originally pointed this flaw out at: https://lists.libguestfs.org/archives/list/guestfs@lists.libguestfs.org/thread/2NXA23G2V3HPWJYAO726PLNBEAAEUJAU/ With this patch, and a malicious server run with nbdkit 1.40 as: $ nbdkit --log=null eval open=' printf \ "EPERM x\\r mess up the output \e[31mmess up the output\e[m mess up" >&2; \ exit 1 ' get_size=' echo 0 ' --run 'qemu-img info "$uri"' we now get: qemu-img: Could not open 'nbd://localhost': Requested export not available server reported: /tmp/nbdkitOZHOKB/open: x\r mess up the output \u001B[31mmess up the output\u001B[m mess up instead of an attempt to hide the name of the Unix socket and forcing the terminal to render part of the text red. Note that I did _not_ sanitize the string being sent through trace-events in trace_nbd_server_error_msg; this is because I assume that our trace engines already treat all string strings as untrusted input and apply their own escaping as needed. Reported-by: "Richard W.M. Jones" Signed-off-by: Eric Blake Reviewed-by: Richard W.M. Jones Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Daniel P. Berrangé --- If my assumption about allowing raw escape bytes through to trace_ calls is wrong (such as when tracing to stderr), let me know. That's a much bigger audit to determine which trace points, if any, should sanitize data before tracing, and/or change the trace engines to sanitize all strings (with possible knock-on effects if trace output changes unexpectedly for a tool expecting something unsanitized). --- nbd/client.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/nbd/client.c b/nbd/client.c index c89c7504673..baa20d10d69 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -23,6 +23,7 @@ #include "trace.h" #include "nbd-internal.h" #include "qemu/cutils.h" +#include "qemu/unicode.h" /* Definitions for opaque data types */ @@ -230,7 +231,9 @@ static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply, } if (msg) { - error_append_hint(errp, "server reported: %s\n", msg); + g_autoptr(GString) buf = g_string_sized_new(reply->length); + mod_utf8_sanitize(buf, msg); + error_append_hint(errp, "server reported: %s\n", buf->str); } err: