From patchwork Mon Feb 20 14:42:19 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 730032 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3vRn4Y2tvxz9sDC for ; Tue, 21 Feb 2017 02:05:33 +1100 (AEDT) Received: from localhost ([::1]:39061 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpWs-0003PB-Sr for incoming@patchwork.ozlabs.org; Mon, 20 Feb 2017 10:05:30 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54625) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpAd-0008GF-4A for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cfpAZ-00040l-U0 for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:31 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:38949 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cfpAZ-00040d-MV for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:27 -0500 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1KEdO9o114288 for ; Mon, 20 Feb 2017 09:42:27 -0500 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0b-001b2d01.pphosted.com with ESMTP id 28pgs4waut-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Feb 2017 09:42:26 -0500 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Feb 2017 07:42:22 -0700 Received: from b01cxnp22033.gho.pok.ibm.com (b01cxnp22033.gho.pok.ibm.com [9.57.198.23]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 48BBE3B20004; Mon, 20 Feb 2017 07:41:34 -0700 (MST) Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1KEgIgA44105848; Mon, 20 Feb 2017 14:42:21 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3F958AE03B; Mon, 20 Feb 2017 09:42:19 -0500 (EST) Received: from bahia.lan (unknown [9.164.137.25]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP id DFF8EAE043; Mon, 20 Feb 2017 09:42:17 -0500 (EST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 20 Feb 2017 15:42:19 +0100 In-Reply-To: <148760155821.31154.13876757160410915057.stgit@bahia.lan> References: <148760155821.31154.13876757160410915057.stgit@bahia.lan> User-Agent: StGit/0.17.1-20-gc0b1b-dirty MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022014-0004-0000-0000-000011A2C42B X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006651; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000204; SDB=6.00824569; UDB=6.00403651; IPR=6.00602024; BA=6.00005157; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014360; XFM=3.00000011; UTC=2017-02-20 14:42:24 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022014-0005-0000-0000-00007D3811FC Message-Id: <148760173919.31154.7555675803159581620.stgit@bahia.lan> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-20_13:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702200144 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PATCH 23/29] 9pfs: local: chmod: don't follow symlinks X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jann Horn , Prasad J Pandit , Greg Kurz , "Aneesh Kumar K.V" , Stefan Hajnoczi Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The local_chmod() callback is vulnerable to symlink attacks because it calls: (1) chmod() which follows symbolic links for all path elements (2) local_set_xattr()->setxattr() which follows symbolic links for all path elements (3) local_set_mapped_file_attr() which calls in turn local_fopen() and mkdir(), both functions following symbolic links for all path elements but the rightmost one This patch converts local_chmod() to rely on open_nofollow() and fchmod() to fix (1). It introduces a local_set_xattrat() replacement to local_set_xattr() based on fsetxattrat() to fix (2), and a local_set_mapped_file_attrat() replacement to local_set_mapped_file_attr() based on local_fopenat() and mkdirat() to fix (3). No effort is made to factor out code because both local_set_xattr() and local_set_mapped_file_attr() will be dropped when all users have been converted to use the "at" versions. This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz --- hw/9pfs/9p-local.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 150 insertions(+), 13 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index fb536fdb3082..56d7731f7ce1 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -327,6 +327,87 @@ err_out: return ret; } +static int local_set_mapped_file_attrat(int dirfd, const char *name, + FsCred *credp) +{ + FILE *fp; + int ret; + char buf[ATTR_MAX]; + int uid = -1, gid = -1, mode = -1, rdev = -1; + int map_dirfd; + + ret = mkdirat(dirfd, VIRTFS_META_DIR, 0700); + if (ret < 0 && errno != EEXIST) { + return -1; + } + + map_dirfd = openat(dirfd, VIRTFS_META_DIR, + O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + if (map_dirfd == -1) { + return -1; + } + + fp = local_fopenat(map_dirfd, name, "r"); + if (!fp) { + if (errno == ENOENT) { + goto update_map_file; + } else { + close_preserve_errno(map_dirfd); + return -1; + } + } + memset(buf, 0, ATTR_MAX); + while (fgets(buf, ATTR_MAX, fp)) { + if (!strncmp(buf, "virtfs.uid", 10)) { + uid = atoi(buf + 11); + } else if (!strncmp(buf, "virtfs.gid", 10)) { + gid = atoi(buf + 11); + } else if (!strncmp(buf, "virtfs.mode", 11)) { + mode = atoi(buf + 12); + } else if (!strncmp(buf, "virtfs.rdev", 11)) { + rdev = atoi(buf + 12); + } + memset(buf, 0, ATTR_MAX); + } + fclose(fp); + +update_map_file: + fp = local_fopenat(map_dirfd, name, "w"); + close_preserve_errno(map_dirfd); + if (!fp) { + return -1; + } + + if (credp->fc_uid != -1) { + uid = credp->fc_uid; + } + if (credp->fc_gid != -1) { + gid = credp->fc_gid; + } + if (credp->fc_mode != -1) { + mode = credp->fc_mode; + } + if (credp->fc_rdev != -1) { + rdev = credp->fc_rdev; + } + + if (uid != -1) { + fprintf(fp, "virtfs.uid=%d\n", uid); + } + if (gid != -1) { + fprintf(fp, "virtfs.gid=%d\n", gid); + } + if (mode != -1) { + fprintf(fp, "virtfs.mode=%d\n", mode); + } + if (rdev != -1) { + fprintf(fp, "virtfs.rdev=%d\n", rdev); + } + fclose(fp); + + return 0; +} + static int local_set_xattr(const char *path, FsCred *credp) { int err; @@ -362,6 +443,45 @@ static int local_set_xattr(const char *path, FsCred *credp) return 0; } +static int local_set_xattrat(int dirfd, const char *path, FsCred *credp) +{ + int err; + + if (credp->fc_uid != -1) { + uint32_t tmp_uid = cpu_to_le32(credp->fc_uid); + err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.uid", &tmp_uid, + sizeof(uid_t), 0); + if (err) { + return err; + } + } + if (credp->fc_gid != -1) { + uint32_t tmp_gid = cpu_to_le32(credp->fc_gid); + err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.gid", &tmp_gid, + sizeof(gid_t), 0); + if (err) { + return err; + } + } + if (credp->fc_mode != -1) { + uint32_t tmp_mode = cpu_to_le32(credp->fc_mode); + err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.mode", &tmp_mode, + sizeof(mode_t), 0); + if (err) { + return err; + } + } + if (credp->fc_rdev != -1) { + uint64_t tmp_rdev = cpu_to_le64(credp->fc_rdev); + err = fsetxattrat_nofollow(dirfd, path, "user.virtfs.rdev", &tmp_rdev, + sizeof(dev_t), 0); + if (err) { + return err; + } + } + return 0; +} + static int local_post_create_passthrough(FsContext *fs_ctx, const char *path, FsCred *credp) { @@ -553,21 +673,38 @@ static ssize_t local_pwritev(FsContext *ctx, V9fsFidOpenState *fs, static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp) { - char *buffer; int ret = -1; - char *path = fs_path->data; + int dirfd; - if (fs_ctx->export_flags & V9FS_SM_MAPPED) { - buffer = rpath(fs_ctx, path); - ret = local_set_xattr(buffer, credp); - g_free(buffer); - } else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { - return local_set_mapped_file_attr(fs_ctx, path, credp); - } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || - (fs_ctx->export_flags & V9FS_SM_NONE)) { - buffer = rpath(fs_ctx, path); - ret = chmod(buffer, credp->fc_mode); - g_free(buffer); + if (fs_ctx->export_flags & V9FS_SM_MAPPED || + fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { + char *dirpath, *name; + + dirpath = g_path_get_dirname(fs_path->data); + dirfd = local_opendir_nofollow(fs_ctx, dirpath); + g_free(dirpath); + if (dirfd == -1) { + return -1; + } + + name = g_path_get_basename(fs_path->data); + if (fs_ctx->export_flags & V9FS_SM_MAPPED) { + ret = local_set_xattrat(dirfd, name, credp); + } else { + ret = local_set_mapped_file_attrat(dirfd, name, credp); + } + g_free(name); + close_preserve_errno(dirfd); + } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || + fs_ctx->export_flags & V9FS_SM_NONE) { + int fd; + + fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0); + if (fd == -1) { + return -1; + } + ret = fchmod(fd, credp->fc_mode); + close_preserve_errno(fd); } return ret; }