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    SubjectRe: [PATCH v5 01/12] S.A.R.A.: add documentation
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    Date
    Hi,

    Just a few typo fixes (inline).

    On 7/6/19 3:54 AM, Salvatore Mesoraca wrote:
    > Adding documentation for S.A.R.A. LSM.
    >
    > Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
    > ---
    > Documentation/admin-guide/LSM/SARA.rst | 177 ++++++++++++++++++++++++
    > Documentation/admin-guide/LSM/index.rst | 1 +
    > Documentation/admin-guide/kernel-parameters.txt | 24 ++++
    > 3 files changed, 202 insertions(+)
    > create mode 100644 Documentation/admin-guide/LSM/SARA.rst
    >
    > diff --git a/Documentation/admin-guide/LSM/SARA.rst b/Documentation/admin-guide/LSM/SARA.rst
    > new file mode 100644
    > index 0000000..fdde04c
    > --- /dev/null
    > +++ b/Documentation/admin-guide/LSM/SARA.rst
    > @@ -0,0 +1,177 @@
    > +.. SPDX-License-Identifier: GPL-2.0
    > +
    > +========
    > +S.A.R.A.
    > +========
    > +
    > +S.A.R.A. (S.A.R.A. is Another Recursive Acronym) is a stacked Linux Security
    > +Module that aims to collect heterogeneous security measures, providing a common
    > +interface to manage them.
    > +As of today it consists of one submodule:
    > +
    > +- WX Protection
    > +
    > +
    > +The kernel-space part is complemented by its user-space counterpart: `saractl`
    > +[2]_.
    > +A test suite for WX Protection, called `sara-test` [4]_, is also available.
    > +More information about where to find these tools and the full S.A.R.A.
    > +documentation are in the `External Links and Documentation`_ section.
    > +
    > +-------------------------------------------------------------------------------
    > +
    > +S.A.R.A.'s Submodules
    > +=====================
    > +
    > +WX Protection
    > +-------------
    > +WX Protection aims to improve user-space programs security by applying:
    > +
    > +- `W^X enforcement`_
    > +- `W!->X (once writable never executable) mprotect restriction`_
    > +- `Executable MMAP prevention`_
    > +
    > +All of the above features can be enabled or disabled both system wide
    > +or on a per executable basis through the use of configuration files managed by
    > +`saractl` [2]_.
    > +
    > +It is important to note that some programs may have issues working with
    > +WX Protection. In particular:
    > +
    > +- **W^X enforcement** will cause problems to any programs that needs
    > + memory pages mapped both as writable and executable at the same time e.g.
    > + programs with executable stack markings in the *PT_GNU_STACK* segment.
    > +- **W!->X mprotect restriction** will cause problems to any program that
    > + needs to generate executable code at run time or to modify executable
    > + pages e.g. programs with a *JIT* compiler built-in or linked against a
    > + *non-PIC* library.
    > +- **Executable MMAP prevention** can work only with programs that have at least
    > + partial *RELRO* support. It's disabled automatically for programs that
    > + lack this feature. It will cause problems to any program that uses *dlopen*
    > + or tries to do an executable mmap. Unfortunately this feature is the one
    > + that could create most problems and should be enabled only after careful
    > + evaluation.
    > +
    > +To extend the scope of the above features, despite the issues that they may
    > +cause, they are complemented by **/proc/PID/attr/sara/wxprot** interface
    > +and **trampoline emulation**.
    > +
    > +At the moment, WX Protection (unless specified otherwise) should work on
    > +any architecture supporting the NX bit, including, but not limited to:
    > +`x86_64`, `x86_32` (with PAE), `ARM` and `ARM64`.
    > +
    > +Parts of WX Protection are inspired by some of the features available in PaX.
    > +
    > +For further information about configuration file format and user-space
    > +utilities please take a look at the full documentation [1]_.
    > +
    > +W^X enforcement
    > +^^^^^^^^^^^^^^^
    > +W^X means that a program can't have a page of memory that is marked, at the
    > +same time, writable and executable. This also allow to detect many bad

    allows

    > +behaviours that make life much more easy for attackers. Programs running with
    > +this feature enabled will be more difficult to exploit in the case they are
    > +affected by some vulnerabilities, because the attacker will be forced
    > +to make more steps in order to exploit them.
    > +This feature also blocks accesses to /proc/*/mem files that would allow to
    > +write the current process read-only memory, bypassing any protection.
    > +
    > +W!->X (once writable never executable) mprotect restriction
    > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    > +"Once writable never executable" means that any page that could have been
    > +marked as writable in the past won't ever be allowed to be marked (e.g. via
    > +an mprotect syscall) as executable.
    > +This goes on the same track as W^X, but is much stricter and prevents
    > +the runtime creation of new executable code in memory.
    > +Obviously, this feature does not prevent a program from creating a new file and
    > +*mmapping* it as executable, however, it will be way more difficult for
    > +attackers to exploit vulnerabilities if this feature is enabled.
    > +
    > +Executable MMAP prevention
    > +^^^^^^^^^^^^^^^^^^^^^^^^^^
    > +This feature prevents the creation of new executable mmaps after the dynamic
    > +libraries have been loaded. When used in combination with **W!->X mprotect
    > +restriction** this feature will completely prevent the creation of new
    > +executable code from the current thread.
    > +Obviously, this feature does not prevent cases in which an attacker uses an
    > +*execve* to start a completely new program. This kind of restriction, if
    > +needed, can be applied using one of the other LSM that focuses on MAC.

    LSMs

    > +Please be aware that this feature can break many programs and so it should be
    > +enabled after careful evaluation.
    > +
    > +/proc/PID/attr/sara/wxprot interface
    > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    > +The `procattr` interface can be used by a thread to discover which
    > +WX Protection features are enabled and/or to tighten them: protection
    > +can't be softened via procattr.
    > +The interface is simple: it's a text file with an hexadecimal

    with a

    > +number in it representing enabled features (more information can be
    > +found in the `Flags values`_ section). Via this interface it is also
    > +possible to perform a complete memory scan to remove the write permission
    > +from pages that are both writable and executable, please note that this
    > +change will also affect other threads of the same process.

    [snip]

    cheers.
    --
    ~Randy

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