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diff --git a/share/man/man4/mac_mls.4 b/share/man/man4/mac_mls.4 new file mode 100644 index 0000000..b314fb5 --- /dev/null +++ b/share/man/man4/mac_mls.4 @@ -0,0 +1,251 @@ +.\" Copyright (c) 2002-2004 Networks Associates Technology, Inc. +.\" All rights reserved. +.\" +.\" This software was developed for the FreeBSD Project by Chris Costello +.\" at Safeport Network Services and Network Associates Laboratories, the +.\" Security Research Division of Network Associates, Inc. under +.\" DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the +.\" DARPA CHATS research program. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd December 1, 2002 +.Dt MAC_MLS 4 +.Os +.Sh NAME +.Nm mac_mls +.Nd "Multi-Level Security confidentiality policy" +.Sh SYNOPSIS +To compile MLS into your kernel, place the following lines in your kernel +configuration file: +.Bd -ragged -offset indent +.Cd "options MAC" +.Cd "options MAC_MLS" +.Ed +.Pp +Alternately, to load the MLS module at boot time, place the following line +in your kernel configuration file: +.Bd -ragged -offset indent +.Cd "options MAC" +.Ed +.Pp +and in +.Xr loader.conf 5 : +.Bd -literal -offset indent +mac_mls_load="YES" +.Ed +.Sh DESCRIPTION +The +.Nm +policy module implements the Multi-Level Security, or MLS model, +which controls access between subjects and objects based on their +confidentiality by means of a strict information flow policy. +Each subject and object in the system has an MLS label associated with it; +each subject's MLS label contains information on its clearance level, +and each object's MLS label contains information on its classification. +.Pp +In MLS, all system subjects and objects are assigned confidentiality labels, +made up of a sensitivity level and zero or more compartments. +Together, these label elements permit all labels to be placed in a partial +order, with confidentiality protections based on a dominance operator +describing the order. +The sensitivity level is expressed as a value between 0 and +65535, with higher values reflecting higher sensitivity levels. +The compartment field is expressed as a set of up to 256 components, +numbered from 1 to 256. +A complete label consists of both sensitivity and compartment +elements. +.Pp +With normal labels, dominance is defined as a label having a higher +or equal active sensitivity level, and having at least +all of the same compartments as the label to which it is being compared. +With respect to label comparisons, +.Dq Li lower +is defined as being dominated by the label to which it is being compared, +and +.Dq Li higher +is defined as dominating the label to which it is being compared, +and +.Dq Li equal +is defined as both labels being able to satisfy the dominance requirements +over one another. +.Pp +Three special label values exist: +.Bl -column -offset indent ".Li mls/equal" "dominated by all other labels" +.It Sy Label Ta Sy Comparison +.It Li mls/low Ta "dominated by all other labels" +.It Li mls/equal Ta "equal to all other labels" +.It Li mls/high Ta "dominates all other labels" +.El +.Pp +The +.Dq Li mls/equal +label may be applied to subjects and objects for which no enforcement of the +MLS security policy is desired. +.Pp +The MLS model enforces the following basic restrictions: +.Bl -bullet +.It +Subjects may not observe the processes of another subject if its +clearance level is lower than the clearance level of the object it is +attempting to observe. +.It +Subjects may not read, write, or otherwise observe objects without proper +clearance (e.g.\& subjects may not observe objects whose classification label +dominates its own clearance label) +.It +Subjects may not write to objects with a lower classification level than +its own clearance level. +.It +A subject may read and write to an object if its clearance level is equal +to the object's classification level as though MLS protections were not in +place. +.El +.Pp +These rules prevent subjects of lower clearance from gaining access +information classified beyond its clearance level in order to protect the +confidentiality of classified information, subjects of higher clearance +from writing to objects of lower classification in order to prevent the +accidental or malicious leaking of information, and subjects of lower +clearance from observing subjects of higher clearance altogether. +In traditional trusted operating systems, the MLS confidentiality model is +used in concert with the Biba integrity model +.Xr ( mac_biba 4 ) +in order to protect the Trusted Code Base (TCB). +.Ss Label Format +Almost all system objects are tagged with an effective, active label element, +reflecting the classification of the object, or classification of the data +contained in the object. +In general, object labels are represented in the following form: +.Pp +.Sm off +.D1 Li mls / Ar grade : compartments +.Sm on +.Pp +For example: +.Bd -literal -offset indent +mls/10:2+3+6 +mls/low +.Ed +.Pp +Subject labels consist of three label elements: an effective (active) label, +as well as a range of available labels. +This range is represented using two ordered MLS label elements, and when set +on a process, permits the process to change its active label to any label of +greater or equal integrity to the low end of the range, and lesser or equal +integrity to the high end of the range. +In general, subject labels are represented in the following form: +.Pp +.Sm off +.D1 Li mls / Ar effectivegrade : effectivecompartments ( lograde : locompartments No - +.D1 Ar higrade : hicompartments ) +.Sm on +.Pp +For example: +.Bd -literal -offset indent +mls/10:2+3+6(5:2+3-20:2+3+4+5+6) +mls/high(low-high) +.Ed +.Pp +Valid ranged labels must meet the following requirement regarding their +elements: +.Pp +.D1 Ar rangehigh No \[>=] Ar effective No \[>=] Ar rangelow +.Pp +One class of objects with ranges currently exists, the network interface. +In the case of the network interface, the effective label element references +the default label for packets received over the interface, and the range +represents the range of acceptable labels of packets to be transmitted over +the interface. +.Ss Runtime Configuration +The following +.Xr sysctl 8 +MIBs are available for fine-tuning the enforcement of this MAC policy. +.Bl -tag -width ".Va security.mac.mls.ptys_equal" +.It Va security.mac.mls.enabled +Enables the enforcement of the MLS confidentiality policy. +(Default: 1). +.It Va security.mac.mls.ptys_equal +Label +.Xr pty 4 Ns s +as +.Dq Li mls/equal +upon creation. +(Default: 0). +.It Va security.mac.mls.revocation_enabled +Revoke access to objects if the label is changed to a more sensitive +level than the subject. +(Default: 0). +.El +.Sh IMPLEMENTATION NOTES +Currently, the +.Nm +policy relies on superuser status +.Pq Xr suser 9 +in order to change network interface MLS labels. +This will eventually go away, but it is currently a liability and may +allow the superuser to bypass MLS protections. +.Sh SEE ALSO +.Xr mac 4 , +.Xr mac_biba 4 , +.Xr mac_bsdextended 4 , +.Xr mac_ifoff 4 , +.Xr mac_lomac 4 , +.Xr mac_none 4 , +.Xr mac_partition 4 , +.Xr mac_portacl 4 , +.Xr mac_seeotheruids 4 , +.Xr mac_test 4 , +.Xr maclabel 7 , +.Xr mac 9 +.Sh HISTORY +The +.Nm +policy module first appeared in +.Fx 5.0 +and was developed by the +.Tn TrustedBSD +Project. +.Sh AUTHORS +This software was contributed to the +.Fx +Project by Network Associates Laboratories, +the Security Research Division of Network Associates +Inc.\& under DARPA/SPAWAR contract N66001-01-C-8035 +.Pq Dq CBOSS , +as part of the DARPA CHATS research program. +.Sh BUGS +See +.Xr mac 9 +concerning appropriateness for production use. +The +.Tn TrustedBSD +MAC Framework is considered experimental in +.Fx . +.Pp +While the MAC Framework design is intended to support the containment of +the root user, not all attack channels are currently protected by entry +point checks. +As such, MAC Framework policies should not be relied on, in isolation, +to protect against a malicious privileged user. |
