Polish "Security first" rst

parent 051aa94f
......@@ -52,52 +52,52 @@ CLI interface access
The command line interface can be accessed in three ways.
`varnishd` can be told to listen and offer CLI connections
on a TCP socket. You can bind the socket to pretty
much anything the kernel will accept::
:ref:`varnishd(1)` can be told to listen and offer CLI connections on
a TCP socket. You can bind the socket to pretty much anything the
kernel will accept::
-T 127.0.0.1:631
-T localhost:9999
-T 192.168.1.1:34
-T '[fe80::1]:8082'
The default is ``-T localhost:0`` which will pick a random
port number, which `varnishadm(8)` can learn from the shared
memory.
The default is ``-T localhost:0`` which will pick a random port
number, which :ref:`varnishadm(1)` can learn from the shared memory.
By using a "localhost" address, you restrict CLI access
to the local machine.
By using a ``localhost`` address, you restrict CLI access to the local
machine.
You can also bind the CLI port to an IP address reachable across
the net, and let other machines connect directly.
This gives you no secrecy, i.e. the CLI commands will
go across the network as ASCII text with no encryption, but
the -S/PSK authentication requires the remote end to know
the shared secret.
This gives you no secrecy, i.e. the CLI commands will go across the
network as ASCII text with no encryption, but the ``-S`` / pre shared
key (`PSK`_) authentication requires the remote end to know the shared
secret.
Alternatively you can bind the CLI port to a 'localhost' address,
Alternatively you can bind the CLI port to a ``localhost`` address,
and give remote users access via a secure connection to the local
machine, using ssh/VPN or similar.
If you use `ssh` you can restrict which commands each user can execute
to just `varnishadm`, or even use a wrapper scripts around `varnishadm`
to allow specific CLI commands.
If you use `ssh(1)` you can restrict which commands each user can
execute to just :ref:`varnishadm(1)`, or even use a wrapper scripts
around :ref:`varnishadm(1)` to allow specific CLI commands.
It is also possible to configure `varnishd` for "reverse mode", using
the '-M' argument. In that case `varnishd` will attempt to open a
TCP connection to the specified address, and initiate a CLI connection
to your central Varnish management facility.
It is also possible to configure :ref:`varnishd(1)` for "reverse
mode", using the ``-M`` argument. In that case :ref:`varnishd(1)`
will attempt to open a TCP connection to the specified address, and
initiate a CLI connection to your central Varnish management facility.
.. XXX:Maybe a sample command here with a brief explanation? benc
The connection in this case is also without encryption, but
the remote end must still authenticate using -S/PSK.
the remote end must still authenticate using ``-S``\ /`PSK`_.
Finally, if you run varnishd with the '-d' option, you get a CLI
command on stdin/stdout, but since you started the process, it
would be hard to prevent you getting CLI access, wouldn't it ?
Finally, if you run varnishd with the ``-d`` option, you get a CLI
command on stdin/stdout, but since you started the process, it would
be hard to prevent you getting CLI access, wouldn't it ?
.. _PSK:
CLI interface authentication
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
......@@ -106,37 +106,38 @@ By default the CLI interface is protected with a simple, yet powerful
"Pre Shared Key" authentication method, which do not provide secrecy
(ie: The CLI commands and responses are not encrypted).
The way -S/PSK works is really simple: During startup a file is
created with a random content and the file is only accessible to
the user who started `varnishd` (or the superuser).
The way ``-S``\ /PSK works is really simple: During startup a file is
created with a random content and the file is only accessible to the
user who started :ref:`varnishd(1)` (or the superuser).
To authenticate and use a CLI connection, you need to know the
contents of that file, in order to answer the cryptographic
challenge `varnishd` issues, see :ref:`ref_psk_auth`.
contents of that file, in order to answer the cryptographic challenge
:ref:`varnishd(1)` issues, see :ref:`ref_psk_auth`.
`varnishadm` uses all of this to restrict access, it will only function,
provided it can read the secret file.
:ref:`varnishadm(1)` uses all of this to restrict access, it will only
function, provided it can read the secret file.
If you want to allow other users, local or remote, to be able to access
CLI connections, you must create your own secret file and make it possible
for (only!) these users to read it.
If you want to allow other users, local or remote, to be able to
access CLI connections, you must create your own secret file and make
it possible for (only!) these users to read it.
A good way to create the secret file is::
dd if=/dev/random of=/etc/varnish_secret count=1
When you start `varnishd`, you specify the filename with '-S', and
it goes without saying that the `varnishd` master process needs
to be able to read the file too.
When you start :ref:`varnishd(1)`, you specify the filename with '-S',
and it goes without saying that the :ref:`varnishd(1)` master process
needs to be able to read the file too.
You can change the contents of the secret file while `varnishd`
runs, it is read every time a CLI connection is authenticated.
You can change the contents of the secret file while
:ref:`varnishd(1)` runs, it is read every time a CLI connection is
authenticated.
On the local system, `varnishadm` can retrieve the filename from
shared memory, but on remote systems, you need to give `varnishadm`
a copy of the secret file, with the -S argument.
On the local system, :ref:`varnishadm(1)` can retrieve the filename
from shared memory, but on remote systems, you need to give
:ref:`varnishadm(1)` a copy of the secret file, with the -S argument.
If you want to disable -S/PSK authentication, use an ``-S none``
If you want to disable ``-S``\ /PSK authentication, use an ``-S none``
argument to varnishd::
varnishd [...] -S none [...]
......@@ -155,7 +156,8 @@ HTTP service, but a few can do more damage than others:
Execute arbitrary programs
:ref:`ref_param_vcc_allow_inline_c`
Allow inline C in VCL, which would allow any C code from VCL to be executed by Varnish.
Allow inline C in VCL, which would allow any C code from VCL
to be executed by Varnish.
Furthermore you may want to look at and lock down:
......@@ -163,12 +165,13 @@ Furthermore you may want to look at and lock down:
Log all CLI commands to `syslog(8)`, so you know what goes on.
:ref:`ref_param_vcc_unsafe_path`
Restrict VCL/VMODs to :ref:`ref_param_vcl_path` and :ref:`ref_param_vmod_path`
Restrict VCL/VMODs to :ref:`ref_param_vcl_path` and
:ref:`ref_param_vmod_path`
:ref:`ref_param_vmod_path`
The directory (or colon separated list of directories) where
Varnish will look for modules. This could potentially be
used to load rogue modules into Varnish.
The directory (or colon separated list of directories) where
Varnish will look for modules. This could potentially be
used to load rogue modules into Varnish.
The CLI interface
-----------------
......@@ -181,12 +184,11 @@ As described above, some of the damage can be limited by restricting
certain parameters, but that will only protect the local filesystem,
and operating system, it will not protect your HTTP service.
We do not currently have a way to restrict specific CLI commands
to specific CLI connections. One way to get such an effect is to
"wrap" all CLI access in pre-approved scripts which use `varnishadm(1)`
to submit the sanitized CLI commands, and restrict a remote user
to only those scripts, for instance using sshd(8)'s configuration.
We do not currently have a way to restrict specific CLI commands to
specific CLI connections. One way to get such an effect is to "wrap"
all CLI access in pre-approved scripts which use :ref:`varnishadm(1)`
to submit the sanitized CLI commands, and restrict a remote user to
only those scripts, for instance using sshd(8)'s configuration.
VCL programs
------------
......@@ -198,11 +200,13 @@ Both of these mechanisms allow execution of arbitrary code and will
thus allow a person to get access to the machine, with the
privileges of the child process.
If `varnishd` is started as root/superuser, we sandbox the child
process, using whatever facilities are available on the operating
system, but if `varnishd` is not started as root/superuser, this is
not possible. No, don't ask me why you have to be superuser to
lower the privilege of a child process...
If :ref:`varnishd(1)` is started as root/superuser, we sandbox the
child process, using whatever facilities are available on the
operating system, but if :ref:`varnishd(1)` is not started as
root/superuser, this is not possible. No, don't ask me why you have to
be superuser to lower the privilege of a child process...
.. XXX the above is not correct for the solaris jail
Inline-C is disabled by default since Varnish version 4, so unless
you enable it, you don't have to worry about it.
......@@ -229,4 +233,3 @@ to various kinds of attacks and subversive activities.
If you have "administrative" HTTP requests, for instance PURGE
requests, we strongly recommend that you restrict them to trusted
IP numbers/nets using VCL's :ref:`vcl_syntax_acl`.
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