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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7053AC433E0 for ; Tue, 23 Jun 2020 18:22:32 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 3B87B207E8 for ; Tue, 23 Jun 2020 18:22:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bLcP6ukw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B87B207E8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55312 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jnnZ1-0008H0-FT for qemu-devel@archiver.kernel.org; Tue, 23 Jun 2020 14:22:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35240) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jnnYG-00070Y-HJ for qemu-devel@nongnu.org; Tue, 23 Jun 2020 14:21:44 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:21120 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jnnYE-0001nb-CU for qemu-devel@nongnu.org; Tue, 23 Jun 2020 14:21:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592936498; 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=cfgnWErQiBEj++RtmHqXcckhk4i5tvf7X2LMrPEWeE0=; b=bLcP6ukwF73padj73AJCH9EQf/FfY7uyhQnbxUUpOguVpdLOMyfLqLeMaFaCD96dQolnp9 QwJ6oHjfE3Gffyni9F6y/ijXVLa3Bi7a5IX5t8L0zp76ROCXjvsqQvbC/8u0j/HHg0YB5f DSMGlzfgnjMlBIgJsXtqNwin7qf8Ogo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-201-YyAWeFcENliNDTnTrkDP9w-1; Tue, 23 Jun 2020 14:21:23 -0400 X-MC-Unique: YyAWeFcENliNDTnTrkDP9w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2D4DD18A0761; Tue, 23 Jun 2020 18:21:22 +0000 (UTC) Received: from [10.3.114.107] (ovpn-114-107.phx2.redhat.com [10.3.114.107]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A97853C6B; Tue, 23 Jun 2020 18:21:21 +0000 (UTC) Subject: Re: [PATCH 1/2] vvfat: Check that updated filenames are valid To: Kevin Wolf , qemu-block@nongnu.org References: <20200623175534.38286-1-kwolf@redhat.com> <20200623175534.38286-2-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <33941063-cfcc-002b-5fe8-d37050d8e532@redhat.com> Date: Tue, 23 Jun 2020 13:21:21 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200623175534.38286-2-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=eblake@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/23 02:55:19 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: nhuck15@gmail.com, qemu-devel@nongnu.org, ppandit@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/23/20 12:55 PM, Kevin Wolf wrote: > FAT allows only a restricted set of characters in file names, and for > some of the illegal characters, it's actually important that we catch > them: If filenames can contain '/', the guest can construct filenames > containing "../" and escape from the assigned vvfat directory. The same > problem could arise if ".." was ever accepted as a literal filename. > > Fix this by adding a check that all filenames are valid in > check_directory_consistency(). > > Reported-by: Nathan Huckleberry > Signed-off-by: Kevin Wolf > --- > block/vvfat.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/block/vvfat.c b/block/vvfat.c > index c65a98e3ee..2fab371258 100644 > --- a/block/vvfat.c > +++ b/block/vvfat.c > @@ -520,6 +520,25 @@ static void set_begin_of_direntry(direntry_t* direntry, uint32_t begin) > direntry->begin_hi = cpu_to_le16((begin >> 16) & 0xffff); > } > > +static bool valid_filename(const unsigned char *name) > +{ > + unsigned char c; > + if (!strcmp((const char*)name, ".") || !strcmp((const char*)name, "..")) { > + return false; > + } > + for (; (c = *name); name++) { > + if (!((c >= '0' && c <= '9') || > + (c >= 'A' && c <= 'Z') || > + (c >= 'a' && c <= 'z') || > + c > 127 || > + strchr("$%'-_@~`!(){}^#&.+,;=[]", c) != 0)) s/0/NULL/ Hmm - would it be any more efficient to use a single comparison of strcspn() vs. strlen(), where you merely spell out the bytes that are rejected? Out of 256 byte values, NUL is implicitly rejected (since these are C strings), the 128 high-bit bytes are all valid, and you have permitted 62 alnum and 23 other characters; that leaves merely 42 byte values to explicitly list in a reject string. Of course, writing the string literal containing those 42 invalid bytes is itself a bit of an exercise in reading the ASCII table: "\x01\x02\x03\x04\x05\x06\x07" "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" "\x10\x11\x12\x13\x14\x15\x16\x17" "\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" " \"*/:<>?\\|\x7f" > + { > + return false; > + } > + } > + return true; > +} > + > static uint8_t to_valid_short_char(gunichar c) > { > c = g_unichar_toupper(c); > @@ -2098,6 +2117,10 @@ DLOG(fprintf(stderr, "check direntry %d:\n", i); print_direntry(direntries + i)) > } > lfn.checksum = 0x100; /* cannot use long name twice */ > > + if (!valid_filename(lfn.name)) { > + fprintf(stderr, "Invalid file name\n"); Wow, the fact that we are still using fprintf is annoying, but pre-existing. > + goto fail; > + } > if (path_len + 1 + lfn.len >= PATH_MAX) { > fprintf(stderr, "Name too long: %s/%s\n", path, lfn.name); > goto fail; > At any rate, the idea makes sense. If you don't like my strcspn() idea, then: Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org