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[79.18.159.44]) by smtp.gmail.com with ESMTPSA id l17sm9080825wmh.14.2020.06.20.11.48.11 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 20 Jun 2020 11:48:11 -0700 (PDT) Date: Sat, 20 Jun 2020 20:48:10 +0200 From: Alfonso Siciliano To: freebsd-hackers@freebsd.org Subject: Re: An option to ignore sysctl CTLFLAG_ANYBODY Message-Id: <20200620204810.89d433d1905cfb03dae1db74@gmail.com> In-Reply-To: <20200618172721.GA28529@daemon> References: <20200618172721.GA28529@daemon> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 49q4SG4k4Mz4YHn X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=QQYOAzhw; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of alfix86@gmail.com designates 2a00:1450:4864:20::444 as permitted sender) smtp.mailfrom=alfix86@gmail.com X-Spamd-Result: default: False [-2.79 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; MV_CASE(0.50)[]; TO_DN_NONE(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[gmail.com:+]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; NEURAL_HAM_SHORT(-0.33)[-0.329]; RECEIVED_SPAMHAUS_PBL(0.00)[79.18.159.44:received]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; MID_RHS_MATCH_FROM(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.94)[-0.941]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.02)[-1.019]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; RCPT_COUNT_ONE(0.00)[1]; RCVD_IN_DNSWL_NONE(0.00)[2a00:1450:4864:20::444:from]; RCVD_TLS_ALL(0.00)[] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 20 Jun 2020 18:48:15 -0000 On Thu, 18 Jun 2020 17:27:21 +0000 Teran McKinney wrote: > Dear freebsd-hackers, > > I apologize if I am using the wrong list for this. > > I am wondering what the best way is to remove CTLFLAG_ANYBODY > behavior on my systems. For my purposes, it's not desirable for any > user to be able to adjust certain sysctls. I'd prefer root to be > the only one able to adjust sysctl. Hi Teran, I had a look at kern_sysctl.c, you could recompile the kernel changing: https://github.com/freebsd/freebsd/blob/master/sys/kern/kern_sysctl.c#L2122 from /* Is this sysctl writable by only privileged users? */ if (req->newptr && !(oid->oid_kind & CTLFLAG_ANYBODY)) { to /* Is this sysctl writable? */ if (req->newptr) { so, sysctl(3) has to call/check priv_check() every time you pass a new value. > I generally don't know what I'm doing as it's my first time hacking > on the FreeBSD kernel, or any kernel in general for that matter. Another (silly :D) solution is a kernel module (nice for training): it could explore the MIB to set CTLFLAG_ANYBODY to 0 for each object. Happy Hacking, Alfonso --- Alfonso S. Siciliano http://alfix.gitlab.io