Return-Path: Received: from fieldses.org ([173.255.197.46]:44222 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750885AbeCHV0B (ORCPT ); Thu, 8 Mar 2018 16:26:01 -0500 Date: Thu, 8 Mar 2018 16:26:00 -0500 From: "J. Bruce Fields" To: Chuck Lever Cc: Guillem Jover , libtirpc List , Linux NFS Mailing List Subject: Re: [PATCH] Do not bind to reserved ports registered in /etc/services Message-ID: <20180308212600.GB16485@fieldses.org> References: <20180110004920.11100-1-gjover@sipwise.com> <20180112184151.GA10261@thunder.hadrons.org> <9a53753a-56bf-12b5-f328-ff1f3a72249d@talpey.com> <20180308202423.GA16485@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180308202423.GA16485@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Mar 08, 2018 at 03:24:23PM -0500, bfields wrote: > Looks like knfsd's not helpful here, though: the export option > ("secure"/"insecure") defaults to "secure", which always requires a low > port. It should be easy to modify "secure" to mean "require low ports > only for auth_sys/auth_null", and that's probably the right thing to do. Disclaimer: totally untested. --b. commit ddc2a5f5ce98 Author: J. Bruce Fields Date: Thu Mar 8 15:49:48 2018 -0500 nfsd: don't require low ports for gss requests In a traditional NFS deployment using auth_unix, the clients are trusted to correctly report the credentials of their logged-in users. The server assumes that only root on client machines is allowed to send requests from low-numbered ports, so it can use the originating port number to distinguish "real" NFS clients from NFS clients run by ordinary users, to prevent ordinary users from spoofing credentials. The originating port number on a gss-authenticated request is less important. The authentication ties the request to a user, and we take it as proof that that user authorized the request. The low port number check no longer adds much. So, don't enforce low port numbers in the auth_gss case. Signed-off-by: J. Bruce Fields diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index 8aa011820c4a..764e6cae6533 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -87,13 +87,23 @@ nfsd_mode_check(struct svc_rqst *rqstp, struct dentry *dentry, return nfserr_inval; } +static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags) +{ + if (flags & NFSEXP_INSECURE_PORT) + return true; + /* We don't require gss requests to use low ports: */ + if (rqstp->rq_cred.cr_flavor >= RPC_AUTH_GSS) + return true; + return test_bit(RQ_SECURE, &rqstp->rq_flags); +} + static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp, struct svc_export *exp) { int flags = nfsexp_flags(rqstp, exp); /* Check if the request originated from a secure port. */ - if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && !(flags & NFSEXP_INSECURE_PORT)) { + if (!nfsd_originating_port_ok(rqstp, flags)) { RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]); dprintk("nfsd: request from insecure port %s!\n", svc_print_addr(rqstp, buf, sizeof(buf)));