mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-24 13:11:14 +07:00
doc: ReSTify Smack.txt
Adjusts for ReST markup and moves under LSM admin guide. Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
parent
30da4f77aa
commit
a5606ced28
@ -1,3 +1,6 @@
|
||||
=====
|
||||
Smack
|
||||
=====
|
||||
|
||||
|
||||
"Good for you, you've decided to clean the elevator!"
|
||||
@ -14,6 +17,7 @@ available to determine which is best suited to the problem
|
||||
at hand.
|
||||
|
||||
Smack consists of three major components:
|
||||
|
||||
- The kernel
|
||||
- Basic utilities, which are helpful but not required
|
||||
- Configuration data
|
||||
@ -39,16 +43,24 @@ The current git repository for Smack user space is:
|
||||
This should make and install on most modern distributions.
|
||||
There are five commands included in smackutil:
|
||||
|
||||
chsmack - display or set Smack extended attribute values
|
||||
smackctl - load the Smack access rules
|
||||
smackaccess - report if a process with one label has access
|
||||
to an object with another
|
||||
chsmack:
|
||||
display or set Smack extended attribute values
|
||||
|
||||
smackctl:
|
||||
load the Smack access rules
|
||||
|
||||
smackaccess:
|
||||
report if a process with one label has access
|
||||
to an object with another
|
||||
|
||||
These two commands are obsolete with the introduction of
|
||||
the smackfs/load2 and smackfs/cipso2 interfaces.
|
||||
|
||||
smackload - properly formats data for writing to smackfs/load
|
||||
smackcipso - properly formats data for writing to smackfs/cipso
|
||||
smackload:
|
||||
properly formats data for writing to smackfs/load
|
||||
|
||||
smackcipso:
|
||||
properly formats data for writing to smackfs/cipso
|
||||
|
||||
In keeping with the intent of Smack, configuration data is
|
||||
minimal and not strictly required. The most important
|
||||
@ -56,15 +68,15 @@ configuration step is mounting the smackfs pseudo filesystem.
|
||||
If smackutil is installed the startup script will take care
|
||||
of this, but it can be manually as well.
|
||||
|
||||
Add this line to /etc/fstab:
|
||||
Add this line to ``/etc/fstab``::
|
||||
|
||||
smackfs /sys/fs/smackfs smackfs defaults 0 0
|
||||
|
||||
The /sys/fs/smackfs directory is created by the kernel.
|
||||
The ``/sys/fs/smackfs`` directory is created by the kernel.
|
||||
|
||||
Smack uses extended attributes (xattrs) to store labels on filesystem
|
||||
objects. The attributes are stored in the extended attribute security
|
||||
name space. A process must have CAP_MAC_ADMIN to change any of these
|
||||
name space. A process must have ``CAP_MAC_ADMIN`` to change any of these
|
||||
attributes.
|
||||
|
||||
The extended attributes that Smack uses are:
|
||||
@ -73,14 +85,17 @@ SMACK64
|
||||
Used to make access control decisions. In almost all cases
|
||||
the label given to a new filesystem object will be the label
|
||||
of the process that created it.
|
||||
|
||||
SMACK64EXEC
|
||||
The Smack label of a process that execs a program file with
|
||||
this attribute set will run with this attribute's value.
|
||||
|
||||
SMACK64MMAP
|
||||
Don't allow the file to be mmapped by a process whose Smack
|
||||
label does not allow all of the access permitted to a process
|
||||
with the label contained in this attribute. This is a very
|
||||
specific use case for shared libraries.
|
||||
|
||||
SMACK64TRANSMUTE
|
||||
Can only have the value "TRUE". If this attribute is present
|
||||
on a directory when an object is created in the directory and
|
||||
@ -89,27 +104,29 @@ SMACK64TRANSMUTE
|
||||
gets the label of the directory instead of the label of the
|
||||
creating process. If the object being created is a directory
|
||||
the SMACK64TRANSMUTE attribute is set as well.
|
||||
|
||||
SMACK64IPIN
|
||||
This attribute is only available on file descriptors for sockets.
|
||||
Use the Smack label in this attribute for access control
|
||||
decisions on packets being delivered to this socket.
|
||||
|
||||
SMACK64IPOUT
|
||||
This attribute is only available on file descriptors for sockets.
|
||||
Use the Smack label in this attribute for access control
|
||||
decisions on packets coming from this socket.
|
||||
|
||||
There are multiple ways to set a Smack label on a file:
|
||||
There are multiple ways to set a Smack label on a file::
|
||||
|
||||
# attr -S -s SMACK64 -V "value" path
|
||||
# chsmack -a value path
|
||||
|
||||
A process can see the Smack label it is running with by
|
||||
reading /proc/self/attr/current. A process with CAP_MAC_ADMIN
|
||||
reading ``/proc/self/attr/current``. A process with ``CAP_MAC_ADMIN``
|
||||
can set the process Smack by writing there.
|
||||
|
||||
Most Smack configuration is accomplished by writing to files
|
||||
in the smackfs filesystem. This pseudo-filesystem is mounted
|
||||
on /sys/fs/smackfs.
|
||||
on ``/sys/fs/smackfs``.
|
||||
|
||||
access
|
||||
Provided for backward compatibility. The access2 interface
|
||||
@ -120,6 +137,7 @@ access
|
||||
this file. The next read will indicate whether the access
|
||||
would be permitted. The text will be either "1" indicating
|
||||
access, or "0" indicating denial.
|
||||
|
||||
access2
|
||||
This interface reports whether a subject with the specified
|
||||
Smack label has a particular access to an object with a
|
||||
@ -127,13 +145,17 @@ access2
|
||||
this file. The next read will indicate whether the access
|
||||
would be permitted. The text will be either "1" indicating
|
||||
access, or "0" indicating denial.
|
||||
|
||||
ambient
|
||||
This contains the Smack label applied to unlabeled network
|
||||
packets.
|
||||
|
||||
change-rule
|
||||
This interface allows modification of existing access control rules.
|
||||
The format accepted on write is:
|
||||
The format accepted on write is::
|
||||
|
||||
"%s %s %s %s"
|
||||
|
||||
where the first string is the subject label, the second the
|
||||
object label, the third the access to allow and the fourth the
|
||||
access to deny. The access strings may contain only the characters
|
||||
@ -141,47 +163,63 @@ change-rule
|
||||
modified by enabling the permissions in the third string and disabling
|
||||
those in the fourth string. If there is no such rule it will be
|
||||
created using the access specified in the third and the fourth strings.
|
||||
|
||||
cipso
|
||||
Provided for backward compatibility. The cipso2 interface
|
||||
is preferred and should be used instead.
|
||||
This interface allows a specific CIPSO header to be assigned
|
||||
to a Smack label. The format accepted on write is:
|
||||
to a Smack label. The format accepted on write is::
|
||||
|
||||
"%24s%4d%4d"["%4d"]...
|
||||
|
||||
The first string is a fixed Smack label. The first number is
|
||||
the level to use. The second number is the number of categories.
|
||||
The following numbers are the categories.
|
||||
"level-3-cats-5-19 3 2 5 19"
|
||||
The following numbers are the categories::
|
||||
|
||||
"level-3-cats-5-19 3 2 5 19"
|
||||
|
||||
cipso2
|
||||
This interface allows a specific CIPSO header to be assigned
|
||||
to a Smack label. The format accepted on write is:
|
||||
"%s%4d%4d"["%4d"]...
|
||||
to a Smack label. The format accepted on write is::
|
||||
|
||||
"%s%4d%4d"["%4d"]...
|
||||
|
||||
The first string is a long Smack label. The first number is
|
||||
the level to use. The second number is the number of categories.
|
||||
The following numbers are the categories.
|
||||
"level-3-cats-5-19 3 2 5 19"
|
||||
The following numbers are the categories::
|
||||
|
||||
"level-3-cats-5-19 3 2 5 19"
|
||||
|
||||
direct
|
||||
This contains the CIPSO level used for Smack direct label
|
||||
representation in network packets.
|
||||
|
||||
doi
|
||||
This contains the CIPSO domain of interpretation used in
|
||||
network packets.
|
||||
|
||||
ipv6host
|
||||
This interface allows specific IPv6 internet addresses to be
|
||||
treated as single label hosts. Packets are sent to single
|
||||
label hosts only from processes that have Smack write access
|
||||
to the host label. All packets received from single label hosts
|
||||
are given the specified label. The format accepted on write is:
|
||||
are given the specified label. The format accepted on write is::
|
||||
|
||||
"%h:%h:%h:%h:%h:%h:%h:%h label" or
|
||||
"%h:%h:%h:%h:%h:%h:%h:%h/%d label".
|
||||
|
||||
The "::" address shortcut is not supported.
|
||||
If label is "-DELETE" a matched entry will be deleted.
|
||||
|
||||
load
|
||||
Provided for backward compatibility. The load2 interface
|
||||
is preferred and should be used instead.
|
||||
This interface allows access control rules in addition to
|
||||
the system defined rules to be specified. The format accepted
|
||||
on write is:
|
||||
on write is::
|
||||
|
||||
"%24s%24s%5s"
|
||||
|
||||
where the first string is the subject label, the second the
|
||||
object label, and the third the requested access. The access
|
||||
string may contain only the characters "rwxat-", and specifies
|
||||
@ -189,17 +227,21 @@ load
|
||||
permissions that are not allowed. The string "r-x--" would
|
||||
specify read and execute access. Labels are limited to 23
|
||||
characters in length.
|
||||
|
||||
load2
|
||||
This interface allows access control rules in addition to
|
||||
the system defined rules to be specified. The format accepted
|
||||
on write is:
|
||||
on write is::
|
||||
|
||||
"%s %s %s"
|
||||
|
||||
where the first string is the subject label, the second the
|
||||
object label, and the third the requested access. The access
|
||||
string may contain only the characters "rwxat-", and specifies
|
||||
which sort of access is allowed. The "-" is a placeholder for
|
||||
permissions that are not allowed. The string "r-x--" would
|
||||
specify read and execute access.
|
||||
|
||||
load-self
|
||||
Provided for backward compatibility. The load-self2 interface
|
||||
is preferred and should be used instead.
|
||||
@ -208,66 +250,83 @@ load-self
|
||||
otherwise be permitted, and are intended to provide additional
|
||||
restrictions on the process. The format is the same as for
|
||||
the load interface.
|
||||
|
||||
load-self2
|
||||
This interface allows process specific access rules to be
|
||||
defined. These rules are only consulted if access would
|
||||
otherwise be permitted, and are intended to provide additional
|
||||
restrictions on the process. The format is the same as for
|
||||
the load2 interface.
|
||||
|
||||
logging
|
||||
This contains the Smack logging state.
|
||||
|
||||
mapped
|
||||
This contains the CIPSO level used for Smack mapped label
|
||||
representation in network packets.
|
||||
|
||||
netlabel
|
||||
This interface allows specific internet addresses to be
|
||||
treated as single label hosts. Packets are sent to single
|
||||
label hosts without CIPSO headers, but only from processes
|
||||
that have Smack write access to the host label. All packets
|
||||
received from single label hosts are given the specified
|
||||
label. The format accepted on write is:
|
||||
label. The format accepted on write is::
|
||||
|
||||
"%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label".
|
||||
|
||||
If the label specified is "-CIPSO" the address is treated
|
||||
as a host that supports CIPSO headers.
|
||||
|
||||
onlycap
|
||||
This contains labels processes must have for CAP_MAC_ADMIN
|
||||
and CAP_MAC_OVERRIDE to be effective. If this file is empty
|
||||
and ``CAP_MAC_OVERRIDE`` to be effective. If this file is empty
|
||||
these capabilities are effective at for processes with any
|
||||
label. The values are set by writing the desired labels, separated
|
||||
by spaces, to the file or cleared by writing "-" to the file.
|
||||
|
||||
ptrace
|
||||
This is used to define the current ptrace policy
|
||||
0 - default: this is the policy that relies on Smack access rules.
|
||||
For the PTRACE_READ a subject needs to have a read access on
|
||||
object. For the PTRACE_ATTACH a read-write access is required.
|
||||
1 - exact: this is the policy that limits PTRACE_ATTACH. Attach is
|
||||
|
||||
0 - default:
|
||||
this is the policy that relies on Smack access rules.
|
||||
For the ``PTRACE_READ`` a subject needs to have a read access on
|
||||
object. For the ``PTRACE_ATTACH`` a read-write access is required.
|
||||
|
||||
1 - exact:
|
||||
this is the policy that limits ``PTRACE_ATTACH``. Attach is
|
||||
only allowed when subject's and object's labels are equal.
|
||||
PTRACE_READ is not affected. Can be overridden with CAP_SYS_PTRACE.
|
||||
2 - draconian: this policy behaves like the 'exact' above with an
|
||||
exception that it can't be overridden with CAP_SYS_PTRACE.
|
||||
``PTRACE_READ`` is not affected. Can be overridden with ``CAP_SYS_PTRACE``.
|
||||
|
||||
2 - draconian:
|
||||
this policy behaves like the 'exact' above with an
|
||||
exception that it can't be overridden with ``CAP_SYS_PTRACE``.
|
||||
|
||||
revoke-subject
|
||||
Writing a Smack label here sets the access to '-' for all access
|
||||
rules with that subject label.
|
||||
|
||||
unconfined
|
||||
If the kernel is configured with CONFIG_SECURITY_SMACK_BRINGUP
|
||||
a process with CAP_MAC_ADMIN can write a label into this interface.
|
||||
If the kernel is configured with ``CONFIG_SECURITY_SMACK_BRINGUP``
|
||||
a process with ``CAP_MAC_ADMIN`` can write a label into this interface.
|
||||
Thereafter, accesses that involve that label will be logged and
|
||||
the access permitted if it wouldn't be otherwise. Note that this
|
||||
is dangerous and can ruin the proper labeling of your system.
|
||||
It should never be used in production.
|
||||
|
||||
relabel-self
|
||||
This interface contains a list of labels to which the process can
|
||||
transition to, by writing to /proc/self/attr/current.
|
||||
transition to, by writing to ``/proc/self/attr/current``.
|
||||
Normally a process can change its own label to any legal value, but only
|
||||
if it has CAP_MAC_ADMIN. This interface allows a process without
|
||||
CAP_MAC_ADMIN to relabel itself to one of labels from predefined list.
|
||||
A process without CAP_MAC_ADMIN can change its label only once. When it
|
||||
if it has ``CAP_MAC_ADMIN``. This interface allows a process without
|
||||
``CAP_MAC_ADMIN`` to relabel itself to one of labels from predefined list.
|
||||
A process without ``CAP_MAC_ADMIN`` can change its label only once. When it
|
||||
does, this list will be cleared.
|
||||
The values are set by writing the desired labels, separated
|
||||
by spaces, to the file or cleared by writing "-" to the file.
|
||||
|
||||
If you are using the smackload utility
|
||||
you can add access rules in /etc/smack/accesses. They take the form:
|
||||
you can add access rules in ``/etc/smack/accesses``. They take the form::
|
||||
|
||||
subjectlabel objectlabel access
|
||||
|
||||
@ -277,14 +336,14 @@ object with objectlabel. If there is no rule no access is allowed.
|
||||
|
||||
Look for additional programs on http://schaufler-ca.com
|
||||
|
||||
From the Smack Whitepaper:
|
||||
|
||||
The Simplified Mandatory Access Control Kernel
|
||||
The Simplified Mandatory Access Control Kernel (Whitepaper)
|
||||
===========================================================
|
||||
|
||||
Casey Schaufler
|
||||
casey@schaufler-ca.com
|
||||
|
||||
Mandatory Access Control
|
||||
------------------------
|
||||
|
||||
Computer systems employ a variety of schemes to constrain how information is
|
||||
shared among the people and services using the machine. Some of these schemes
|
||||
@ -297,6 +356,7 @@ access control mechanisms because you don't have a choice regarding the users
|
||||
or programs that have access to pieces of data.
|
||||
|
||||
Bell & LaPadula
|
||||
---------------
|
||||
|
||||
From the middle of the 1980's until the turn of the century Mandatory Access
|
||||
Control (MAC) was very closely associated with the Bell & LaPadula security
|
||||
@ -306,6 +366,7 @@ within the Capital Beltway and Scandinavian supercomputer centers but was
|
||||
often sited as failing to address general needs.
|
||||
|
||||
Domain Type Enforcement
|
||||
-----------------------
|
||||
|
||||
Around the turn of the century Domain Type Enforcement (DTE) became popular.
|
||||
This scheme organizes users, programs, and data into domains that are
|
||||
@ -316,6 +377,7 @@ necessary to provide a secure domain mapping leads to the scheme being
|
||||
disabled or used in limited ways in the majority of cases.
|
||||
|
||||
Smack
|
||||
-----
|
||||
|
||||
Smack is a Mandatory Access Control mechanism designed to provide useful MAC
|
||||
while avoiding the pitfalls of its predecessors. The limitations of Bell &
|
||||
@ -326,46 +388,55 @@ Enforcement and avoided by defining access controls in terms of the access
|
||||
modes already in use.
|
||||
|
||||
Smack Terminology
|
||||
-----------------
|
||||
|
||||
The jargon used to talk about Smack will be familiar to those who have dealt
|
||||
with other MAC systems and shouldn't be too difficult for the uninitiated to
|
||||
pick up. There are four terms that are used in a specific way and that are
|
||||
especially important:
|
||||
|
||||
Subject: A subject is an active entity on the computer system.
|
||||
Subject:
|
||||
A subject is an active entity on the computer system.
|
||||
On Smack a subject is a task, which is in turn the basic unit
|
||||
of execution.
|
||||
|
||||
Object: An object is a passive entity on the computer system.
|
||||
Object:
|
||||
An object is a passive entity on the computer system.
|
||||
On Smack files of all types, IPC, and tasks can be objects.
|
||||
|
||||
Access: Any attempt by a subject to put information into or get
|
||||
Access:
|
||||
Any attempt by a subject to put information into or get
|
||||
information from an object is an access.
|
||||
|
||||
Label: Data that identifies the Mandatory Access Control
|
||||
Label:
|
||||
Data that identifies the Mandatory Access Control
|
||||
characteristics of a subject or an object.
|
||||
|
||||
These definitions are consistent with the traditional use in the security
|
||||
community. There are also some terms from Linux that are likely to crop up:
|
||||
|
||||
Capability: A task that possesses a capability has permission to
|
||||
Capability:
|
||||
A task that possesses a capability has permission to
|
||||
violate an aspect of the system security policy, as identified by
|
||||
the specific capability. A task that possesses one or more
|
||||
capabilities is a privileged task, whereas a task with no
|
||||
capabilities is an unprivileged task.
|
||||
|
||||
Privilege: A task that is allowed to violate the system security
|
||||
Privilege:
|
||||
A task that is allowed to violate the system security
|
||||
policy is said to have privilege. As of this writing a task can
|
||||
have privilege either by possessing capabilities or by having an
|
||||
effective user of root.
|
||||
|
||||
Smack Basics
|
||||
------------
|
||||
|
||||
Smack is an extension to a Linux system. It enforces additional restrictions
|
||||
on what subjects can access which objects, based on the labels attached to
|
||||
each of the subject and the object.
|
||||
|
||||
Labels
|
||||
~~~~~~
|
||||
|
||||
Smack labels are ASCII character strings. They can be up to 255 characters
|
||||
long, but keeping them to twenty-three characters is recommended.
|
||||
@ -377,7 +448,7 @@ contain unprintable characters, the "/" (slash), the "\" (backslash), the "'"
|
||||
(quote) and '"' (double-quote) characters.
|
||||
Smack labels cannot begin with a '-'. This is reserved for special options.
|
||||
|
||||
There are some predefined labels:
|
||||
There are some predefined labels::
|
||||
|
||||
_ Pronounced "floor", a single underscore character.
|
||||
^ Pronounced "hat", a single circumflex character.
|
||||
@ -390,14 +461,18 @@ of a process will usually be assigned by the system initialization
|
||||
mechanism.
|
||||
|
||||
Access Rules
|
||||
~~~~~~~~~~~~
|
||||
|
||||
Smack uses the traditional access modes of Linux. These modes are read,
|
||||
execute, write, and occasionally append. There are a few cases where the
|
||||
access mode may not be obvious. These include:
|
||||
|
||||
Signals: A signal is a write operation from the subject task to
|
||||
Signals:
|
||||
A signal is a write operation from the subject task to
|
||||
the object task.
|
||||
Internet Domain IPC: Transmission of a packet is considered a
|
||||
|
||||
Internet Domain IPC:
|
||||
Transmission of a packet is considered a
|
||||
write operation from the source task to the destination task.
|
||||
|
||||
Smack restricts access based on the label attached to a subject and the label
|
||||
@ -417,6 +492,7 @@ order:
|
||||
7. Any other access is denied.
|
||||
|
||||
Smack Access Rules
|
||||
~~~~~~~~~~~~~~~~~~
|
||||
|
||||
With the isolation provided by Smack access separation is simple. There are
|
||||
many interesting cases where limited access by subjects to objects with
|
||||
@ -427,8 +503,9 @@ be "born" highly classified. To accommodate such schemes Smack includes a
|
||||
mechanism for specifying rules allowing access between labels.
|
||||
|
||||
Access Rule Format
|
||||
~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The format of an access rule is:
|
||||
The format of an access rule is::
|
||||
|
||||
subject-label object-label access
|
||||
|
||||
@ -446,7 +523,7 @@ describe access modes:
|
||||
|
||||
Uppercase values for the specification letters are allowed as well.
|
||||
Access mode specifications can be in any order. Examples of acceptable rules
|
||||
are:
|
||||
are::
|
||||
|
||||
TopSecret Secret rx
|
||||
Secret Unclass R
|
||||
@ -456,7 +533,7 @@ are:
|
||||
New Old rRrRr
|
||||
Closed Off -
|
||||
|
||||
Examples of unacceptable rules are:
|
||||
Examples of unacceptable rules are::
|
||||
|
||||
Top Secret Secret rx
|
||||
Ace Ace r
|
||||
@ -469,6 +546,7 @@ access specifications. The dash is a placeholder, so "a-r" is the same
|
||||
as "ar". A lone dash is used to specify that no access should be allowed.
|
||||
|
||||
Applying Access Rules
|
||||
~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The developers of Linux rarely define new sorts of things, usually importing
|
||||
schemes and concepts from other systems. Most often, the other systems are
|
||||
@ -511,6 +589,7 @@ one process to another requires that the sender have write access to the
|
||||
receiver. The receiver is not required to have read access to the sender.
|
||||
|
||||
Setting Access Rules
|
||||
~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The configuration file /etc/smack/accesses contains the rules to be set at
|
||||
system startup. The contents are written to the special file
|
||||
@ -520,6 +599,7 @@ one rule, with the most recently specified overriding any earlier
|
||||
specification.
|
||||
|
||||
Task Attribute
|
||||
~~~~~~~~~~~~~~
|
||||
|
||||
The Smack label of a process can be read from /proc/<pid>/attr/current. A
|
||||
process can read its own Smack label from /proc/self/attr/current. A
|
||||
@ -527,12 +607,14 @@ privileged process can change its own Smack label by writing to
|
||||
/proc/self/attr/current but not the label of another process.
|
||||
|
||||
File Attribute
|
||||
~~~~~~~~~~~~~~
|
||||
|
||||
The Smack label of a filesystem object is stored as an extended attribute
|
||||
named SMACK64 on the file. This attribute is in the security namespace. It can
|
||||
only be changed by a process with privilege.
|
||||
|
||||
Privilege
|
||||
~~~~~~~~~
|
||||
|
||||
A process with CAP_MAC_OVERRIDE or CAP_MAC_ADMIN is privileged.
|
||||
CAP_MAC_OVERRIDE allows the process access to objects it would
|
||||
@ -540,6 +622,7 @@ be denied otherwise. CAP_MAC_ADMIN allows a process to change
|
||||
Smack data, including rules and attributes.
|
||||
|
||||
Smack Networking
|
||||
~~~~~~~~~~~~~~~~
|
||||
|
||||
As mentioned before, Smack enforces access control on network protocol
|
||||
transmissions. Every packet sent by a Smack process is tagged with its Smack
|
||||
@ -551,6 +634,7 @@ packet has write access to the receiving process and if that is not the case
|
||||
the packet is dropped.
|
||||
|
||||
CIPSO Configuration
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
It is normally unnecessary to specify the CIPSO configuration. The default
|
||||
values used by the system handle all internal cases. Smack will compose CIPSO
|
||||
@ -571,13 +655,13 @@ discarded. The DOI is 3 by default. The value can be read from
|
||||
The label and category set are mapped to a Smack label as defined in
|
||||
/etc/smack/cipso.
|
||||
|
||||
A Smack/CIPSO mapping has the form:
|
||||
A Smack/CIPSO mapping has the form::
|
||||
|
||||
smack level [category [category]*]
|
||||
|
||||
Smack does not expect the level or category sets to be related in any
|
||||
particular way and does not assume or assign accesses based on them. Some
|
||||
examples of mappings:
|
||||
examples of mappings::
|
||||
|
||||
TopSecret 7
|
||||
TS:A,B 7 1 2
|
||||
@ -597,25 +681,30 @@ value can be read from /sys/fs/smackfs/direct and changed by writing to
|
||||
/sys/fs/smackfs/direct.
|
||||
|
||||
Socket Attributes
|
||||
~~~~~~~~~~~~~~~~~
|
||||
|
||||
There are two attributes that are associated with sockets. These attributes
|
||||
can only be set by privileged tasks, but any task can read them for their own
|
||||
sockets.
|
||||
|
||||
SMACK64IPIN: The Smack label of the task object. A privileged
|
||||
SMACK64IPIN:
|
||||
The Smack label of the task object. A privileged
|
||||
program that will enforce policy may set this to the star label.
|
||||
|
||||
SMACK64IPOUT: The Smack label transmitted with outgoing packets.
|
||||
SMACK64IPOUT:
|
||||
The Smack label transmitted with outgoing packets.
|
||||
A privileged program may set this to match the label of another
|
||||
task with which it hopes to communicate.
|
||||
|
||||
Smack Netlabel Exceptions
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
You will often find that your labeled application has to talk to the outside,
|
||||
unlabeled world. To do this there's a special file /sys/fs/smackfs/netlabel
|
||||
where you can add some exceptions in the form of :
|
||||
@IP1 LABEL1 or
|
||||
@IP2/MASK LABEL2
|
||||
where you can add some exceptions in the form of::
|
||||
|
||||
@IP1 LABEL1 or
|
||||
@IP2/MASK LABEL2
|
||||
|
||||
It means that your application will have unlabeled access to @IP1 if it has
|
||||
write access on LABEL1, and access to the subnet @IP2/MASK if it has write
|
||||
@ -624,28 +713,32 @@ access on LABEL2.
|
||||
Entries in the /sys/fs/smackfs/netlabel file are matched by longest mask
|
||||
first, like in classless IPv4 routing.
|
||||
|
||||
A special label '@' and an option '-CIPSO' can be used there :
|
||||
@ means Internet, any application with any label has access to it
|
||||
-CIPSO means standard CIPSO networking
|
||||
A special label '@' and an option '-CIPSO' can be used there::
|
||||
|
||||
If you don't know what CIPSO is and don't plan to use it, you can just do :
|
||||
echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel
|
||||
@ means Internet, any application with any label has access to it
|
||||
-CIPSO means standard CIPSO networking
|
||||
|
||||
If you don't know what CIPSO is and don't plan to use it, you can just do::
|
||||
|
||||
echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel
|
||||
|
||||
If you use CIPSO on your 192.168.0.0/16 local network and need also unlabeled
|
||||
Internet access, you can have :
|
||||
echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 192.168.0.0/16 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel
|
||||
Internet access, you can have::
|
||||
|
||||
echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 192.168.0.0/16 -CIPSO > /sys/fs/smackfs/netlabel
|
||||
echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel
|
||||
|
||||
Writing Applications for Smack
|
||||
------------------------------
|
||||
|
||||
There are three sorts of applications that will run on a Smack system. How an
|
||||
application interacts with Smack will determine what it will have to do to
|
||||
work properly under Smack.
|
||||
|
||||
Smack Ignorant Applications
|
||||
---------------------------
|
||||
|
||||
By far the majority of applications have no reason whatever to care about the
|
||||
unique properties of Smack. Since invoking a program has no impact on the
|
||||
@ -653,12 +746,14 @@ Smack label associated with the process the only concern likely to arise is
|
||||
whether the process has execute access to the program.
|
||||
|
||||
Smack Relevant Applications
|
||||
---------------------------
|
||||
|
||||
Some programs can be improved by teaching them about Smack, but do not make
|
||||
any security decisions themselves. The utility ls(1) is one example of such a
|
||||
program.
|
||||
|
||||
Smack Enforcing Applications
|
||||
----------------------------
|
||||
|
||||
These are special programs that not only know about Smack, but participate in
|
||||
the enforcement of system policy. In most cases these are the programs that
|
||||
@ -666,15 +761,16 @@ set up user sessions. There are also network services that provide information
|
||||
to processes running with various labels.
|
||||
|
||||
File System Interfaces
|
||||
----------------------
|
||||
|
||||
Smack maintains labels on file system objects using extended attributes. The
|
||||
Smack label of a file, directory, or other file system object can be obtained
|
||||
using getxattr(2).
|
||||
using getxattr(2)::
|
||||
|
||||
len = getxattr("/", "security.SMACK64", value, sizeof (value));
|
||||
|
||||
will put the Smack label of the root directory into value. A privileged
|
||||
process can set the Smack label of a file system object with setxattr(2).
|
||||
process can set the Smack label of a file system object with setxattr(2)::
|
||||
|
||||
len = strlen("Rubble");
|
||||
rc = setxattr("/foo", "security.SMACK64", "Rubble", len, 0);
|
||||
@ -683,17 +779,18 @@ will set the Smack label of /foo to "Rubble" if the program has appropriate
|
||||
privilege.
|
||||
|
||||
Socket Interfaces
|
||||
-----------------
|
||||
|
||||
The socket attributes can be read using fgetxattr(2).
|
||||
|
||||
A privileged process can set the Smack label of outgoing packets with
|
||||
fsetxattr(2).
|
||||
fsetxattr(2)::
|
||||
|
||||
len = strlen("Rubble");
|
||||
rc = fsetxattr(fd, "security.SMACK64IPOUT", "Rubble", len, 0);
|
||||
|
||||
will set the Smack label "Rubble" on packets going out from the socket if the
|
||||
program has appropriate privilege.
|
||||
program has appropriate privilege::
|
||||
|
||||
rc = fsetxattr(fd, "security.SMACK64IPIN, "*", strlen("*"), 0);
|
||||
|
||||
@ -701,33 +798,40 @@ will set the Smack label "*" as the object label against which incoming
|
||||
packets will be checked if the program has appropriate privilege.
|
||||
|
||||
Administration
|
||||
--------------
|
||||
|
||||
Smack supports some mount options:
|
||||
|
||||
smackfsdef=label: specifies the label to give files that lack
|
||||
smackfsdef=label:
|
||||
specifies the label to give files that lack
|
||||
the Smack label extended attribute.
|
||||
|
||||
smackfsroot=label: specifies the label to assign the root of the
|
||||
smackfsroot=label:
|
||||
specifies the label to assign the root of the
|
||||
file system if it lacks the Smack extended attribute.
|
||||
|
||||
smackfshat=label: specifies a label that must have read access to
|
||||
smackfshat=label:
|
||||
specifies a label that must have read access to
|
||||
all labels set on the filesystem. Not yet enforced.
|
||||
|
||||
smackfsfloor=label: specifies a label to which all labels set on the
|
||||
smackfsfloor=label:
|
||||
specifies a label to which all labels set on the
|
||||
filesystem must have read access. Not yet enforced.
|
||||
|
||||
These mount options apply to all file system types.
|
||||
|
||||
Smack auditing
|
||||
--------------
|
||||
|
||||
If you want Smack auditing of security events, you need to set CONFIG_AUDIT
|
||||
in your kernel configuration.
|
||||
By default, all denied events will be audited. You can change this behavior by
|
||||
writing a single character to the /sys/fs/smackfs/logging file :
|
||||
0 : no logging
|
||||
1 : log denied (default)
|
||||
2 : log accepted
|
||||
3 : log denied & accepted
|
||||
writing a single character to the /sys/fs/smackfs/logging file::
|
||||
|
||||
0 : no logging
|
||||
1 : log denied (default)
|
||||
2 : log accepted
|
||||
3 : log denied & accepted
|
||||
|
||||
Events are logged as 'key=value' pairs, for each event you at least will get
|
||||
the subject, the object, the rights requested, the action, the kernel function
|
||||
@ -735,6 +839,7 @@ that triggered the event, plus other pairs depending on the type of event
|
||||
audited.
|
||||
|
||||
Bringup Mode
|
||||
------------
|
||||
|
||||
Bringup mode provides logging features that can make application
|
||||
configuration and system bringup easier. Configure the kernel with
|
@ -36,5 +36,6 @@ the one "major" module (e.g. SELinux) if there is one configured.
|
||||
apparmor
|
||||
LoadPin
|
||||
SELinux
|
||||
Smack
|
||||
tomoyo
|
||||
Yama
|
||||
|
@ -1,7 +1,5 @@
|
||||
00-INDEX
|
||||
- this file.
|
||||
Smack.txt
|
||||
- documentation on the Smack Linux Security Module.
|
||||
keys-ecryptfs.txt
|
||||
- description of the encryption keys for the ecryptfs filesystem.
|
||||
keys-request-key.txt
|
||||
|
@ -11876,7 +11876,7 @@ L: linux-security-module@vger.kernel.org
|
||||
W: http://schaufler-ca.com
|
||||
T: git git://github.com/cschaufler/smack-next
|
||||
S: Maintained
|
||||
F: Documentation/security/Smack.txt
|
||||
F: Documentation/admin-guide/LSM/Smack.rst
|
||||
F: security/smack/
|
||||
|
||||
DRIVERS FOR ADAPTIVE VOLTAGE SCALING (AVS)
|
||||
|
Loading…
Reference in New Issue
Block a user