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[nncp.git] / doc / usecases.texi

@node Use cases
@unnumbered Use cases

@menu
* Occasional connection to mail server: UsecaseMail.
* Unreliable/expensive communication link: UsecaseUnreliable.
* Slow/expensive link for high-volume data, bad QoS: UsecaseQoS.
* Extreme terrestrial environments, no link: UsecaseNoLink.
* Private, isolated MitM-resistant networks: UsecaseF2F.
* Highly secure isolated air-gap computers: UsecaseAirgap.
* Network censorship bypassing: UsecaseCensor.
* Reconnaissance, spying, intelligence, covert agents: UsecaseSpy.
@end menu

@node UsecaseMail
@section Occasional connection to mail server

Assume that you have got your own @url{http://www.postfix.org/, Postfix}
SMTP server connected to the Internet. But you read and write emails on
your notebook, that is connected to it just from time to time. How can
you flush buffered mail queues when your notebook is connected?

One possibility is to log in and run something like @command{postqueue
-f}, but by default you have got only several days so and sender will
receive notification emails that his messages still are not delivered
yet. Also you must have secure link (SSH, VPN, etc).

Another possibility is to use POP3/IMAP4 servers, but this is too
overcomplicated and bloated for the simple task. Not an option. KISS!

@anchor{Postfix}

Just tell both of your Postfixes (on the server and notebook) to drop
email as a mail via NNCP to specified node. This is done similarly as
with UUCP and as written in Postfix
@url{http://www.postfix.org/UUCP_README.html, documentation}.

Search for @verb{|uucp|} related strings in @file{master.cf} and replace
command to NNCP ones:

@verbatim
nncp unix - n n - - pipe flags=Fqhu user=nncp argv=nncp-mail -quiet $nexthop $recipient
@end verbatim

then add transport map, telling that mail for example.com domain can be
reached through NNCP transport to node @emph{bob}:

@verbatim
example.com nncp:bob
@end verbatim

Now, all mail will be stored in NNCP @ref{Spool, spool}, that after
exchanging and tossing will call local @command{sendmail} command to
deliver them just that was happened on the same machine.

@node UsecaseUnreliable
@section Unreliable/expensive communication link

Assume that you have got slow modem/radio/cellular link that frequently
disconnects and causes TCP timeouts. Not all HTTP servers support file
download continuation. SMTP does not support resuming at all and heavy
messages is a problem to retrieve. Moreover, each disconnect leads to
the same data retransmission again, that can be expensive to afford.

Just send your mail and files through NNCP. You can use either offline
delivery methods -- read about them in the next section, or you can use
included NNCP TCP daemon.

The command below:

@verbatim
% nncp-file file_i_want_to_send bob:
% nncp-file another_file bob:movie.avi
@end verbatim

will queue two files for sending to @code{emph} node. Fire and forget!
Now this is daemon's job (or offline transfer) to send this file part by
part to remote system when it is available.

@node UsecaseQoS
@section Slow/expensive link for high-volume data, bad QoS

Assume that you can give your relatively cheap 2 TiB removable hard
drive to someone each day at the morning (and take it back at the
evening). This equals to 185 Mbps good quality (without any speed
degradation) link in single direction. What about more and bigger hard
drives? This type of data exchange is called
@url{https://en.wikipedia.org/wiki/Sneakernet, sneakernet}/floppynet.

NNCP allows traffic @ref{Niceness, prioritizing}: each packet has
niceness level, that will guarantee that it will be processed earlier or
later than the other ones. Nearly all commands has corresponding option:

@verbatim
% nncp-file -nice 32 myfile node:dst
% nncp-xfer -nice 192 /mnt/shared
% nncp-call -nice 224 bob
[...]
@end verbatim

@node UsecaseNoLink
@section Extreme terrestrial environments, no link

This is some kind of too slow link. Offline delivery methods is the only
choice. Just send files as shown in previous section, but use removable
media for transferring packets to other nodes.

Assume that you send two files to @emph{bob} node. Insert USB storage
device, mount it and run:

@verbatim
% nncp-xfer -node bob /media/usbstick
@end verbatim

to copy all outbound packets related to @emph{bob}'s node. Use
@option{-force} option to forcefully create related directory on USB
storage if they are missing (for example when running for the first
time).

If you use single storage device to transfer data both to @emph{bob} and
@emph{alice}, then just omit @option{-node} option to copy all existing
outgoing packets to that storage device.

@verbatim
% nncp-xfer /media/usbstick
@end verbatim

Unmount it and transfer somehow to Bob and Alice. When they will insert
it in their computers, they will use exactly the same command:

@verbatim
% nncp-xfer /media/usbstick
@end verbatim

to find all packets related to their node and copy them locally for
further processing. @ref{nncp-xfer} is the only command used with
removable devices.

@node UsecaseF2F
@section Private, isolated MitM-resistant networks

All Internet connections can be eavesdropped and forged. You
@strong{have to} to use encryption and authentication for securing them.
But it is very hard to secure metadata, that leaks during each online
session. When you start your shiny new software server be sure that
there could be huge quantity of bogus peers trying to perform
@url{https://en.wikipedia.org/wiki/Sybil_attack, Sybil attack}. Opennet
peer-to-peer networking is dangerous thing to do.

The most popular cryptographic protocol in Internet is
@url{https://en.wikipedia.org/wiki/Transport_Layer_Security, TLS} that
is very hard to implement right and hard to configure for mutual
participants authentication. Not all TLS configurations and related
protocols provide @url{https://en.wikipedia.org/wiki/Forward_secrecy,
forward secrecy} property -- all previously intercepted packets could be
read if private keys are compromised.

Friend-to-friend networks, darknets can mitigate risks related to fake
and forged nodes. However they are harder to support and require more
time to be done right.

NNCP's TCP daemon uses @url{http://noiseprotocol.org/, Noise-IK}
protocol to mutually authenticate peers and provide effective (both
participants send payload in the very first packet) secure transport
with forward secrecy property.

@verbatim
% nncp-daemon -bind [::]:5400
@end verbatim
will start TCP daemon listening on all interfaces for incoming
connections.

@verbatim
% nncp-call bob
@end verbatim
will try to connect to @emph{bob}'s node known TCP addresses (taken from
configuration file) and send all related outbound packets and retrieve
those the Bob has. All interrupted transfers will be automatically
resumed.

@node UsecaseAirgap
@section Highly secure isolated air-gap computers

If you worry much about security, then air-gapped computer could be the
only choice you can afford. Computer without any modems, wired and
wireless networks. Obviously the only possibility to exchange mail and
files is to use physically removable storage devices like CD-ROM, hard
drive, tape and USB flash drives (worst choice, due to those devices
complexity).

Presumably you have got another own hop before that computer: another
intermediate node which performs basic verification of retrieved storage
devices, possibly by rewriting the data from USB/hard drives to CD-RWs.

NNCP supports packets relying (transitioning) out-of-box.

@verbatim
neigh:
  bob:
    [...]
    addrs:
      lan: [fe80::5400%igb0]:5400
  bob-airgap:
    [...]
    via: [bob]
@end verbatim

That configuration file tells that we have got two known neighbours:
@emph{bob} and @emph{bob-airgap}. @emph{bob} can be reached via online
connection using @emph{lan} address. @emph{bob-airgap} can be reached by
sending intermediate relay packet through the @emph{bob}.

Any command like @command{nncp-file myfile bob-airgap:} will
automatically create an encapsulated packet: one for the destination
endpoint, and other carrying it for intermediate relaying node.

Pay attention that relaying node knows nothing about the packet inside,
but just its size and priority. Transition packets are encrypted too.
@emph{bob} can not read @emph{bob-airgap}'s packets.

@node UsecaseCensor
@section Network censorship bypassing

This is some kind of bad link too. Some governments tend to forbid
@strong{any} kind of private communication between people, allowing only
entertainment content delivering and popular social networks access
(that are already bloated with advertisements, locally executed
proprietary JavaScript code (for spying on user activities, collect data
on them), shamelessly exploiting of very basic interhuman need of
communication).

This is their natural wish. But nobody forces you to obey huge
corporations like Apple, Google or Microsoft. It is your choice to
create isolated friend-to-friend network with piles of harmless content
and private messaging. Only predators silently watch for their victims
in mammals world -- it harms your health being watched and feeling that
you are the victim that has already done something wrong.

@node UsecaseSpy
@section Reconnaissance, spying, intelligence, covert agents

Those guys know how Internet is a dangerous place incompatible with
privacy. They require quick, fast dropping and picking of data. No
possibility of many round-trips -- just drop the data, fire-and-forget.
It could be either removable media again, or
@url{https://en.wikipedia.org/wiki/USB_dead_drop, USB dead drops}, or
@url{https://en.wikipedia.org/wiki/PirateBox, PirateBox}es, or
@url{https://en.wikipedia.org/wiki/Short-range_agent_communications, SRAC}.
Short lived short range networks like Bluetooth and WiFi can also
be pretty fast, allowing to quickly fire chunks of queued packets.

Very important property is that compromising of those dead drops and
storages must not be fatal and even dangerous. Packets sent through the
network and exchanged via those devices are end-to-end @ref{Encrypted,
encrypted} (but unfortunately lacking forward secrecy). No filenames,
mail recipients are seen.

All communications are done with so-called @ref{Spool, spool} area:
directory containing only those unprocessed encrypted packets. After
packet transfer you still can not read any of them: you have to run
another stage: tossing, that involves your private cryptographic keys.
So even if your loose your computer, storage devices and so on -- it is
not so bad, because you are not carrying private keys with it, you do
not "toss" those packets immediately on the same device. Tossing
(reading those encrypted packets and extracting transferred files and
mail messages) could and should be done on a separate computer.