dejima/dejima-guard
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

The guard, which is the step that makes any of this detection

Browse Source 
dejima-devbox-hardener made a devbox report what changed. Everything it
reports goes to a log nobody reads: the node's firewall log, and the audit's
own output in a journal. A signal you never see is not detection, and calling
it one would be the same mistake as reporting a timeout as a pass.

This is the part that reads those reports and wakes somebody up.

ITS OWN REPOSITORY because it runs on neither of that project's two machines.
Shipping it inside the hardener would have put a program that must not run on
the devbox in the repository whose whole subject is the devbox.

THE INVERSION IS THE DESIGN. The guard reaches in; the devbox never reaches
out. That falls out of the firewall the devbox already has - inbound SSH from
the admin subnet is permitted, so no new rule is needed - and it buys three
things:

  - the baseline lives here, so root on the devbox can lie about the current
    state but cannot alter what this machine recorded last week;
  - the alert leaves from here, so a compromised devbox can neither suppress
    it by going quiet nor drown it by shouting;
  - silence becomes a signal. A reporter running on the devbox and switched
    off by whoever took it causes nothing to happen, forever. A collection
    that stops arriving is itself the alarm, and it is the only mechanism
    here a compromised machine cannot defeat by doing nothing.

Not a service: no port, no daemon, nothing inbound. A timer runs it, it makes
a few outbound connections, writes a file and exits - which is why it needs
no machine of its own, and why "another thing to harden" is not the trade.

NOTHING THE DEVBOX CONTROLS REACHES THE PHONE. Alert bodies are composed here
from a fixed vocabulary and counts. A compromised devbox controls every
filename and unit name, and interpolating one into a push hands it a channel
to the operator's phone - the thing dejima's own notification guarantee
exists to prevent, defeated one layer out. Detail stays in the local report.

The documented path is ntfy for alerts and an Uptime Kuma push monitor for
the dead-man's switch, both self-hosted. The alert topic is deliberately not
the one dejima publishes to: that URL lives on the devbox, so root there can
drown the topic or forge an all-clear.

Two bugs the tests found rather than review: `printf '%s\n' ""` writes a
newline, so an audit returning nothing passed a -s check and would have been
recorded as a baseline; and die() inside a command substitution ends the
subshell rather than the program, so a missing host produced an empty result
and the cycle carried on as though the box had answered.

`bats test/` 16 passing.
This commit is contained in:
Brad Anderson
2026-08-28 00:14:17 -07:00
commit 89f2896971
9 changed files with 1520 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
.gitignore
+1
View File
@@ -0,0 +1 @@
*.swp
LICENSE
+674
View File
@@ -0,0 +1,674 @@
GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
The GNU General Public License is a free, copyleft license for
software and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains free
software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work released this way by its authors. You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.
To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights. Therefore, you have
certain responsibilities if you distribute copies of the software, or if
you modify it: responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received. You must make sure that they, too, receive
or can get the source code. And you must show them these terms so they
know their rights.
Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.
For the developers' and authors' protection, the GPL clearly explains
that there is no warranty for this free software. For both users' and
authors' sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.
Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the manufacturer
can do so. This is fundamentally incompatible with the aim of
protecting users' freedom to change the software. The systematic
pattern of such abuse occurs in the area of products for individuals to
use, which is precisely where it is most unacceptable. Therefore, we
have designed this version of the GPL to prohibit the practice for those
products. If such problems arise substantially in other domains, we
stand ready to extend this provision to those domains in future versions
of the GPL, as needed to protect the freedom of users.
Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
software on general-purpose computers, but in those that do, we wish to
avoid the special danger that patents applied to a free program could
make it effectively proprietary. To prevent this, the GPL assures that
patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution and
modification follow.
TERMS AND CONDITIONS
0. Definitions.
"This License" refers to version 3 of the GNU General Public License.
"Copyright" also means copyright-like laws that apply to other kinds of
works, such as semiconductor masks.
"The Program" refers to any copyrightable work licensed under this
License. Each licensee is addressed as "you". "Licensees" and
"recipients" may be individuals or organizations.
To "modify" a work means to copy from or adapt all or part of the work
in a fashion requiring copyright permission, other than the making of an
exact copy. The resulting work is called a "modified version" of the
earlier work or a work "based on" the earlier work.
A "covered work" means either the unmodified Program or a work based
on the Program.
To "propagate" a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on a
computer or modifying a private copy. Propagation includes copying,
distribution (with or without modification), making available to the
public, and in some countries other activities as well.
To "convey" a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user through
a computer network, with no transfer of a copy, is not conveying.
An interactive user interface displays "Appropriate Legal Notices"
to the extent that it includes a convenient and prominently visible
feature that (1) displays an appropriate copyright notice, and (2)
tells the user that there is no warranty for the work (except to the
extent that warranties are provided), that licensees may convey the
work under this License, and how to view a copy of this License. If
the interface presents a list of user commands or options, such as a
menu, a prominent item in the list meets this criterion.
1. Source Code.
The "source code" for a work means the preferred form of the work
for making modifications to it. "Object code" means any non-source
form of a work.
A "Standard Interface" means an interface that either is an official
standard defined by a recognized standards body, or, in the case of
interfaces specified for a particular programming language, one that
is widely used among developers working in that language.
The "System Libraries" of an executable work include anything, other
than the work as a whole, that (a) is included in the normal form of
packaging a Major Component, but which is not part of that Major
Component, and (b) serves only to enable use of the work with that
Major Component, or to implement a Standard Interface for which an
implementation is available to the public in source code form. A
"Major Component", in this context, means a major essential component
(kernel, window system, and so on) of the specific operating system
(if any) on which the executable work runs, or a compiler used to
produce the work, or an object code interpreter used to run it.
The "Corresponding Source" for a work in object code form means all
the source code needed to generate, install, and (for an executable
work) run the object code and to modify the work, including scripts to
control those activities. However, it does not include the work's
System Libraries, or general-purpose tools or generally available free
programs which are used unmodified in performing those activities but
which are not part of the work. For example, Corresponding Source
includes interface definition files associated with source files for
the work, and the source code for shared libraries and dynamically
linked subprograms that the work is specifically designed to require,
such as by intimate data communication or control flow between those
subprograms and other parts of the work.
The Corresponding Source need not include anything that users
can regenerate automatically from other parts of the Corresponding
Source.
The Corresponding Source for a work in source code form is that
same work.
2. Basic Permissions.
All rights granted under this License are granted for the term of
copyright on the Program, and are irrevocable provided the stated
conditions are met. This License explicitly affirms your unlimited
permission to run the unmodified Program. The output from running a
covered work is covered by this License only if the output, given its
content, constitutes a covered work. This License acknowledges your
rights of fair use or other equivalent, as provided by copyright law.
You may make, run and propagate covered works that you do not
convey, without conditions so long as your license otherwise remains
in force. You may convey covered works to others for the sole purpose
of having them make modifications exclusively for you, or provide you
with facilities for running those works, provided that you comply with
the terms of this License in conveying all material for which you do
not control copyright. Those thus making or running the covered works
for you must do so exclusively on your behalf, under your direction
and control, on terms that prohibit them from making any copies of
your copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under
the conditions stated below. Sublicensing is not allowed; section 10
makes it unnecessary.
3. Protecting Users' Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological
measure under any applicable law fulfilling obligations under article
11 of the WIPO copyright treaty adopted on 20 December 1996, or
similar laws prohibiting or restricting circumvention of such
measures.
When you convey a covered work, you waive any legal power to forbid
circumvention of technological measures to the extent such circumvention
is effected by exercising rights under this License with respect to
the covered work, and you disclaim any intention to limit operation or
modification of the work as a means of enforcing, against the work's
users, your or third parties' legal rights to forbid circumvention of
technological measures.
4. Conveying Verbatim Copies.
You may convey verbatim copies of the Program's source code as you
receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice;
keep intact all notices stating that this License and any
non-permissive terms added in accord with section 7 apply to the code;
keep intact all notices of the absence of any warranty; and give all
recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey,
and you may offer support or warranty protection for a fee.
5. Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to
produce it from the Program, in the form of source code under the
terms of section 4, provided that you also meet all of these conditions:
a) The work must carry prominent notices stating that you modified
it, and giving a relevant date.
b) The work must carry prominent notices stating that it is
released under this License and any conditions added under section
7. This requirement modifies the requirement in section 4 to
"keep intact all notices".
c) You must license the entire work, as a whole, under this
License to anyone who comes into possession of a copy. This
License will therefore apply, along with any applicable section 7
additional terms, to the whole of the work, and all its parts,
regardless of how they are packaged. This License gives no
permission to license the work in any other way, but it does not
invalidate such permission if you have separately received it.
d) If the work has interactive user interfaces, each must display
Appropriate Legal Notices; however, if the Program has interactive
interfaces that do not display Appropriate Legal Notices, your
work need not make them do so.
A compilation of a covered work with other separate and independent
works, which are not by their nature extensions of the covered work,
and which are not combined with it such as to form a larger program,
in or on a volume of a storage or distribution medium, is called an
"aggregate" if the compilation and its resulting copyright are not
used to limit the access or legal rights of the compilation's users
beyond what the individual works permit. Inclusion of a covered work
in an aggregate does not cause this License to apply to the other
parts of the aggregate.
6. Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms
of sections 4 and 5, provided that you also convey the
machine-readable Corresponding Source under the terms of this License,
in one of these ways:
a) Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by the
Corresponding Source fixed on a durable physical medium
customarily used for software interchange.
b) Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by a
written offer, valid for at least three years and valid for as
long as you offer spare parts or customer support for that product
model, to give anyone who possesses the object code either (1) a
copy of the Corresponding Source for all the software in the
product that is covered by this License, on a durable physical
medium customarily used for software interchange, for a price no
more than your reasonable cost of physically performing this
conveying of source, or (2) access to copy the
Corresponding Source from a network server at no charge.
c) Convey individual copies of the object code with a copy of the
written offer to provide the Corresponding Source. This
alternative is allowed only occasionally and noncommercially, and
only if you received the object code with such an offer, in accord
with subsection 6b.
d) Convey the object code by offering access from a designated
place (gratis or for a charge), and offer equivalent access to the
Corresponding Source in the same way through the same place at no
further charge. You need not require recipients to copy the
Corresponding Source along with the object code. If the place to
copy the object code is a network server, the Corresponding Source
may be on a different server (operated by you or a third party)
that supports equivalent copying facilities, provided you maintain
clear directions next to the object code saying where to find the
Corresponding Source. Regardless of what server hosts the
Corresponding Source, you remain obligated to ensure that it is
available for as long as needed to satisfy these requirements.
e) Convey the object code using peer-to-peer transmission, provided
you inform other peers where the object code and Corresponding
Source of the work are being offered to the general public at no
charge under subsection 6d.
A separable portion of the object code, whose source code is excluded
from the Corresponding Source as a System Library, need not be
included in conveying the object code work.
A "User Product" is either (1) a "consumer product", which means any
tangible personal property which is normally used for personal, family,
or household purposes, or (2) anything designed or sold for incorporation
into a dwelling. In determining whether a product is a consumer product,
doubtful cases shall be resolved in favor of coverage. For a particular
product received by a particular user, "normally used" refers to a
typical or common use of that class of product, regardless of the status
of the particular user or of the way in which the particular user
actually uses, or expects or is expected to use, the product. A product
is a consumer product regardless of whether the product has substantial
commercial, industrial or non-consumer uses, unless such uses represent
the only significant mode of use of the product.
"Installation Information" for a User Product means any methods,
procedures, authorization keys, or other information required to install
and execute modified versions of a covered work in that User Product from
a modified version of its Corresponding Source. The information must
suffice to ensure that the continued functioning of the modified object
code is in no case prevented or interfered with solely because
modification has been made.
If you convey an object code work under this section in, or with, or
specifically for use in, a User Product, and the conveying occurs as
part of a transaction in which the right of possession and use of the
User Product is transferred to the recipient in perpetuity or for a
fixed term (regardless of how the transaction is characterized), the
Corresponding Source conveyed under this section must be accompanied
by the Installation Information. But this requirement does not apply
if neither you nor any third party retains the ability to install
modified object code on the User Product (for example, the work has
been installed in ROM).
The requirement to provide Installation Information does not include a
requirement to continue to provide support service, warranty, or updates
for a work that has been modified or installed by the recipient, or for
the User Product in which it has been modified or installed. Access to a
network may be denied when the modification itself materially and
adversely affects the operation of the network or violates the rules and
protocols for communication across the network.
Corresponding Source conveyed, and Installation Information provided,
in accord with this section must be in a format that is publicly
documented (and with an implementation available to the public in
source code form), and must require no special password or key for
unpacking, reading or copying.
7. Additional Terms.
"Additional permissions" are terms that supplement the terms of this
License by making exceptions from one or more of its conditions.
Additional permissions that are applicable to the entire Program shall
be treated as though they were included in this License, to the extent
that they are valid under applicable law. If additional permissions
apply only to part of the Program, that part may be used separately
under those permissions, but the entire Program remains governed by
this License without regard to the additional permissions.
When you convey a copy of a covered work, you may at your option
remove any additional permissions from that copy, or from any part of
it. (Additional permissions may be written to require their own
removal in certain cases when you modify the work.) You may place
additional permissions on material, added by you to a covered work,
for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you
add to a covered work, you may (if authorized by the copyright holders of
that material) supplement the terms of this License with terms:
a) Disclaiming warranty or limiting liability differently from the
terms of sections 15 and 16 of this License; or
b) Requiring preservation of specified reasonable legal notices or
author attributions in that material or in the Appropriate Legal
Notices displayed by works containing it; or
c) Prohibiting misrepresentation of the origin of that material, or
requiring that modified versions of such material be marked in
reasonable ways as different from the original version; or
d) Limiting the use for publicity purposes of names of licensors or
authors of the material; or
e) Declining to grant rights under trademark law for use of some
trade names, trademarks, or service marks; or
f) Requiring indemnification of licensors and authors of that
material by anyone who conveys the material (or modified versions of
it) with contractual assumptions of liability to the recipient, for
any liability that these contractual assumptions directly impose on
those licensors and authors.
All other non-permissive additional terms are considered "further
restrictions" within the meaning of section 10. If the Program as you
received it, or any part of it, contains a notice stating that it is
governed by this License along with a term that is a further
restriction, you may remove that term. If a license document contains
a further restriction but permits relicensing or conveying under this
License, you may add to a covered work material governed by the terms
of that license document, provided that the further restriction does
not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you
must place, in the relevant source files, a statement of the
additional terms that apply to those files, or a notice indicating
where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the
form of a separately written license, or stated as exceptions;
the above requirements apply either way.
8. Termination.
You may not propagate or modify a covered work except as expressly
provided under this License. Any attempt otherwise to propagate or
modify it is void, and will automatically terminate your rights under
this License (including any patent licenses granted under the third
paragraph of section 11).
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly and
finally terminates your license, and (b) permanently, if the copyright
holder fails to notify you of the violation by some reasonable means
prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, you do not qualify to receive new licenses for the same
material under section 10.
9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or
run a copy of the Program. Ancillary propagation of a covered work
occurring solely as a consequence of using peer-to-peer transmission
to receive a copy likewise does not require acceptance. However,
nothing other than this License grants you permission to propagate or
modify any covered work. These actions infringe copyright if you do
not accept this License. Therefore, by modifying or propagating a
covered work, you indicate your acceptance of this License to do so.
10. Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically
receives a license from the original licensors, to run, modify and
propagate that work, subject to this License. You are not responsible
for enforcing compliance by third parties with this License.
An "entity transaction" is a transaction transferring control of an
organization, or substantially all assets of one, or subdividing an
organization, or merging organizations. If propagation of a covered
work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever
licenses to the work the party's predecessor in interest had or could
give under the previous paragraph, plus a right to possession of the
Corresponding Source of the work from the predecessor in interest, if
the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the
rights granted or affirmed under this License. For example, you may
not impose a license fee, royalty, or other charge for exercise of
rights granted under this License, and you may not initiate litigation
(including a cross-claim or counterclaim in a lawsuit) alleging that
any patent claim is infringed by making, using, selling, offering for
sale, or importing the Program or any portion of it.
11. Patents.
A "contributor" is a copyright holder who authorizes use under this
License of the Program or a work on which the Program is based. The
work thus licensed is called the contributor's "contributor version".
A contributor's "essential patent claims" are all patent claims
owned or controlled by the contributor, whether already acquired or
hereafter acquired, that would be infringed by some manner, permitted
by this License, of making, using, or selling its contributor version,
but do not include claims that would be infringed only as a
consequence of further modification of the contributor version. For
purposes of this definition, "control" includes the right to grant
patent sublicenses in a manner consistent with the requirements of
this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free
patent license under the contributor's essential patent claims, to
make, use, sell, offer for sale, import and otherwise run, modify and
propagate the contents of its contributor version.
In the following three paragraphs, a "patent license" is any express
agreement or commitment, however denominated, not to enforce a patent
(such as an express permission to practice a patent or covenant not to
sue for patent infringement). To "grant" such a patent license to a
party means to make such an agreement or commitment not to enforce a
patent against the party.
If you convey a covered work, knowingly relying on a patent license,
and the Corresponding Source of the work is not available for anyone
to copy, free of charge and under the terms of this License, through a
publicly available network server or other readily accessible means,
then you must either (1) cause the Corresponding Source to be so
available, or (2) arrange to deprive yourself of the benefit of the
patent license for this particular work, or (3) arrange, in a manner
consistent with the requirements of this License, to extend the patent
license to downstream recipients. "Knowingly relying" means you have
actual knowledge that, but for the patent license, your conveying the
covered work in a country, or your recipient's use of the covered work
in a country, would infringe one or more identifiable patents in that
country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or
arrangement, you convey, or propagate by procuring conveyance of, a
covered work, and grant a patent license to some of the parties
receiving the covered work authorizing them to use, propagate, modify
or convey a specific copy of the covered work, then the patent license
you grant is automatically extended to all recipients of the covered
work and works based on it.
A patent license is "discriminatory" if it does not include within
the scope of its coverage, prohibits the exercise of, or is
conditioned on the non-exercise of one or more of the rights that are
specifically granted under this License. You may not convey a covered
work if you are a party to an arrangement with a third party that is
in the business of distributing software, under which you make payment
to the third party based on the extent of your activity of conveying
the work, and under which the third party grants, to any of the
parties who would receive the covered work from you, a discriminatory
patent license (a) in connection with copies of the covered work
conveyed by you (or copies made from those copies), or (b) primarily
for and in connection with specific products or compilations that
contain the covered work, unless you entered into that arrangement,
or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot convey a
covered work so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you may
not convey it at all. For example, if you agree to terms that obligate you
to collect a royalty for further conveying from those to whom you convey
the Program, the only way you could satisfy both those terms and this
License would be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work. The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of
the GNU General Public License from time to time. Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.
Each version is given a distinguishing version number. If the
Program specifies that a certain numbered version of the GNU General
Public License "or any later version" applies to it, you have the
option of following the terms and conditions either of that numbered
version or of any later version published by the Free Software
Foundation. If the Program does not specify a version number of the
GNU General Public License, you may choose any version ever published
by the Free Software Foundation.
If the Program specifies that a proxy can decide which future
versions of the GNU General Public License can be used, that proxy's
public statement of acceptance of a version permanently authorizes you
to choose that version for the Program.
Later license versions may give you additional or different
permissions. However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<https://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program
into proprietary programs. If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library. If this is what you want to do, use the GNU Lesser General
Public License instead of this License. But first, please read
<https://www.gnu.org/licenses/why-not-lgpl.html>.
README.md
+158
View File
@@ -0,0 +1,158 @@
# dejima-guard
Notices when a devbox changes, and tells you — from a machine that is not the
devbox.
A devbox has no upper bound on how long a compromise lasts. Its sister project,
[dejima-ci-hardener](https://gitbox.branderson.io/dejima/dejima-ci-hardener),
rebuilds a runner from a snapshot on a schedule, so anything that gets in has
until the next rebuild. A devbox holds uncommitted work and is never rebuilt.
Nothing reclaims it and nothing is looking.
[dejima-devbox-hardener](https://gitbox.branderson.io/dejima/dejima-devbox-hardener)
made the box report what changed. This is the part that reads those reports and
wakes you up.
**It does not run on the devbox.** That is the entire design, not a deployment
detail — see [Why it pulls](#why-it-pulls).
| | |
| --- | --- |
| [Setting it up](#setting-it-up) | **Start here.** One config file, one key, one timer |
| [Why it pulls](#why-it-pulls) | The three things the inversion buys |
| [What it does not do](#what-it-does-not-do) | Read this before relying on it |
---
## Before you use it
**Early development. Not ready to be depended on.** Nothing here has been
through outside review, an external audit, or adversarial testing by anyone but
the person who wrote it. Every security property this describes is a claim
awaiting scrutiny, not one that has survived it.
**One maintainer, no support.** Nothing about this is promised: not a reply, not
a fix, not a release.
**It is a second opinion, not a boundary.** Nothing here prevents anything. It
watches, and everything it can tell you is something that has already happened.
## Setting it up
It needs a machine that is always on and is not the devbox. A NAS, a home
server, a Pi, an existing VM — anything already running. **Not a new VM**: this
is not a service, and a machine of its own would be a poor trade for something
whose whole job is to notice.
```sh
sudo install -m 0755 bin/dejima-guard /usr/local/sbin/dejima-guard
sudo install -d -m 0750 /etc/dejima-guard /var/lib/dejima-guard
sudo install -m 0640 etc/config.example /etc/dejima-guard/config
sudoedit /etc/dejima-guard/config
```
Then a key of its own, restricted at the devbox end so it can run the two
read-only subcommands and nothing else:
```sh
sudo ssh-keygen -t ed25519 -N '' -f /var/lib/dejima-guard/id_ed25519
sudo cat /var/lib/dejima-guard/id_ed25519.pub
```
`etc/config.example` has the `authorized_keys` line to pair it with. Then:
```sh
sudo dejima-guard check # first run records the baseline, alerts nothing
sudo install -m 0644 systemd/dejima-guard.{service,timer} /etc/systemd/system/
sudo sed -i 's|@@BIN_DIR@@|/usr/local/sbin|' /etc/systemd/system/dejima-guard.service
sudo systemctl daemon-reload && sudo systemctl enable --now dejima-guard.timer
```
**Take the first baseline on a box you believe is clean.** One taken on a
compromised machine records the compromise as normal and reports clean forever.
### The happy path is ntfy and Uptime Kuma
Both self-hosted, and if you run dejima's remote access you already have the
first.
**ntfy** carries the alerts. Give this its **own topic**, separate from the one
dejima pushes to, and give the devbox no credential for it — `ntfy_url` lives in
`~/.config/dejima/config` *on the devbox*, so root there can publish to that
topic, drown it, or forge an all-clear. Deny the devbox read on the alert topic
too: an intruder who can read the alerts about themselves learns what the
monitoring noticed and what it missed.
**Uptime Kuma** is the dead-man's switch. A push monitor expects a ping on a
cadence and alerts when one does not arrive; this pings only on a cycle that
completed and found nothing wrong. Without it, a watcher that dies looks exactly
like a watcher with nothing to report.
Anything else works through `alert_command` and a `heartbeat_url` of the same
shape. Only the one path is documented, because a list of alternatives is a list
that goes stale.
## Why it pulls
The watcher reaches in; the devbox never reaches out. That falls out of the
firewall the devbox already has — inbound SSH from the admin subnet is
permitted, so **no new firewall rule is needed** — and it buys three things:
**The baseline lives here.** Root on the devbox can lie about the current state.
It cannot alter what this machine recorded last week.
**The alert leaves from here.** A compromised devbox cannot suppress it by going
quiet, or drown it by shouting.
**Silence becomes a signal.** This is the one that matters. A reporter running
*on* the devbox, switched off by whoever took the box, causes nothing to happen —
forever, with nothing to see. A collection that stops arriving is itself the
alarm, and it is the only mechanism here that a compromised machine cannot
defeat by doing nothing.
It also bounds tampering: at a fifteen-minute cadence, an intruder has fifteen
minutes to notice the monitoring and scrub, and the resulting gap is evidence.
## What it does not do
- **It does not prevent anything.** Everything it reports has already happened.
- **It does not detect an intruder who anticipated it.** The devbox-side audit
can be lied to by root on the devbox. What this catches is a payload that did
not think to look — most of them, since the adversary in this threat model did
not choose your devbox.
- **It does not watch CI runners.** Their scheduled rollback bounds dwell time,
so the need is weaker. The design is not tier-specific and extending it would
not be a rewrite.
- **It does not watch itself.** That is what the heartbeat is for, and the thing
receiving it is outside this program.
- **It sends no detail.** Alert bodies carry counts and categories, never a
filename or a unit name. A compromised devbox controls those strings, and
interpolating one into a push hands it a channel to your phone. The detail is
in `dejima-guard report`, on this machine.
## Use
```sh
dejima-guard check # what the timer runs
dejima-guard report # the last cycle's detail
dejima-guard accept # record the devbox's current state as the baseline
```
`accept` is a decision, which is why a check never makes it. After an `apt
upgrade` on the devbox, read the report, and if the changes are yours, accept.
## Tests
```sh
bats test/
```
They stub `ssh` and `curl` on `PATH` rather than replacing functions, because
what is under test includes whether this program calls them at all — and the
worst failures here are silent: alerting on nothing until the topic is muted,
staying quiet when the box stops answering, and sending the heartbeat on a cycle
that failed.
## License
GPL-3.0-or-later.
bin/dejima-guard
Executable
+288
View File
@@ -0,0 +1,288 @@
#!/usr/bin/env bash
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2026 Brad Anderson
#
# Watches a devbox from a machine that is not the devbox.
#
# THE INVERSION IS THE WHOLE DESIGN. The watcher reaches in; the watched host
# never reaches out. That falls out of the firewall the devbox already has -
# inbound SSH from the admin subnet is permitted, so this needs no new rule -
# and it buys three things at once:
#
# - the baseline lives here, on a machine the devbox cannot reach. Root there
# can lie about the current state; it cannot alter what was recorded last
# week;
# - the alert leaves from here, so a compromised devbox cannot suppress it by
# staying quiet or drown it by shouting;
# - SILENCE BECOMES A SIGNAL. A push reporter that is switched off causes
# nothing to happen, forever. A pull that stops arriving is itself the
# alarm, and it is the only mechanism here a compromised box cannot defeat
# by doing nothing.
#
# It is not a service. No port, no daemon, no inbound anything: a timer runs
# it, it makes a few outbound connections, writes a file and exits. That is why
# it does not need a machine of its own, and why "another thing to harden" is
# not the trade being made.
#
# WHAT IT HOLDS is the new concentration of privilege and is worth stating: an
# SSH key to the devbox, and a token for whatever it alerts through. Neither
# grants a shell on the hypervisor. The key should be its own, restricted by
# command= in authorized_keys, rather than a general-purpose administrative one.
set -euo pipefail
PROG=${0##*/}
CONF=${DEJIMA_GUARD_CONF:-/etc/dejima-guard/config}
STATE_DIR=${DEJIMA_GUARD_STATE:-/var/lib/dejima-guard}
say() { printf '%s\n' "$*" >&2; }
die() { say "$PROG: $*"; exit 2; }
# --- config -----------------------------------------------------------------
#
# Parsed, never sourced. This file names a host to SSH to and a URL to post to,
# and sourcing it would make both of those arbitrary code from a file that has
# no reason to be executable.
cfg() { # cfg KEY [DEFAULT]
local v=""
[ -r "$CONF" ] && v=$(sed -n "s/^[[:space:]]*$1[[:space:]]*=[[:space:]]*//p" "$CONF" | tail -1)
[ -n "$v" ] || v="${2-}"
printf '%s\n' "$v"
}
# The same restriction dejima puts on its own notify URL, for the same reason:
# curl reads a leading -K/path as an option that takes the request from a file,
# so a value without an explicit scheme is refused rather than guessed at.
check_url() { # check_url NAME VALUE
case "$2" in
http://*|https://*) ;;
*) die "$1 must start with http:// or https:// - got '$2'" ;;
esac
case "$2" in
*[!A-Za-z0-9:/._~?=%@+-]*) die "$1 contains a character that is not allowed here" ;;
esac
}
# --- reaching the devbox ----------------------------------------------------
ssh_devbox() { # ssh_devbox COMMAND...
local host user key opts
host=$(cfg host) ; [ -n "$host" ] || die "no host in $CONF"
user=$(cfg user root)
key=$(cfg ssh_key)
opts="-o BatchMode=yes -o ConnectTimeout=$(cfg ssh_timeout 10)"
# StrictHostKeyChecking left at the ssh default on purpose. Turning it off
# here would mean this program accepts a changed host key without comment -
# on the one connection whose whole point is noticing that something about
# that machine changed.
# shellcheck disable=SC2086
ssh $opts ${key:+-i "$key"} "$user@$host" "$@"
}
# --- alerting ---------------------------------------------------------------
#
# NOTHING THE DEVBOX CONTROLS REACHES THE PHONE. dejima draws this line for its
# own pushes and states where the guarantee lives; the same rule applies one
# layer out, for the same reason. A compromised devbox controls filenames, unit
# names and process names - every string a naive alert body would interpolate -
# and ntfy renders a URL in a body as something tappable.
#
# So a body is composed here, from a fixed vocabulary and counts. The detail
# stays in the report on this machine. The push exists to say go and look.
alert() { # alert PRIORITY TITLE BODY
local url tok cmd
url=$(cfg ntfy_url)
cmd=$(cfg alert_command)
if [ -n "$cmd" ]; then
printf '%s\n%s\n' "$2" "$3" | $cmd
return 0
fi
[ -n "$url" ] || { say "no ntfy_url and no alert_command: alert not sent"; return 1; }
check_url ntfy_url "$url"
tok=$(cfg ntfy_token)
curl -fsS --max-time 15 \
${tok:+-H "Authorization: Bearer $tok"} \
-H "Title: $2" -H "Priority: $1" -H "Tags: rotating_light" \
-d "$3" "$url" >/dev/null
}
# The dead-man's switch, and the only part of this a compromised devbox cannot
# reach at all.
#
# Uptime Kuma's push monitor is the documented shape: it expects a ping on a
# cadence and alerts when one does not arrive. So this pings only on a cycle
# that completed - never in a failure path - and the absence of that ping is
# what reports a watcher that has died, been switched off, or lost its network.
#
# Anything speaking the same "GET this URL to say you are alive" shape works
# here. Only the one is documented, because a list of alternatives is a list
# that goes stale.
heartbeat() {
local url
url=$(cfg heartbeat_url)
[ -n "$url" ] || return 0
check_url heartbeat_url "$url"
curl -fsS --max-time 10 "$url" >/dev/null || say "heartbeat failed to send"
}
# --- the cycle ---------------------------------------------------------------
BASE="$STATE_DIR/baseline"
LAST="$STATE_DIR/last-report"
# Categories rather than paths, because the body of an alert must carry nothing
# the watched machine chose. A count of changed unit files is safe to send; the
# name of one is not.
summarise() { # summarise DIFF_FILE
local f=$1 n_file n_unit n_port
n_file=$(grep -c '^[+-] FILE ' "$f" || true)
n_unit=$(grep -c '^[+-] UNIT ' "$f" || true)
n_port=$(grep -c '^[+-] PORT ' "$f" || true)
[ "$n_file" -gt 0 ] && printf '%s file(s)\n' "$n_file"
[ "$n_unit" -gt 0 ] && printf '%s systemd unit(s)\n' "$n_unit"
[ "$n_port" -gt 0 ] && printf '%s listening port(s)\n' "$n_port"
return 0
}
# Checked here rather than at the point of use.
#
# ssh_devbox runs inside a command substitution, and `exit` in there ends the
# subshell rather than this program - so a missing host produced an empty
# result and the cycle carried on as though the box had answered with nothing.
require_config() {
[ -n "$(cfg host)" ] || die "no host in $CONF - nothing to watch"
local u
for u in ntfy_url heartbeat_url; do
[ -n "$(cfg "$u")" ] && check_url "$u" "$(cfg "$u")"
done
return 0
}
cmd_check() {
local rc=0 state now reach_rc reach_out changed=0 body=""
require_config
install -d -m 0750 "$STATE_DIR"
now=$(mktemp) || die "no temp space"
# shellcheck disable=SC2064
trap "rm -f '$now' '$now.diff'" EXIT
# 1. Can it be reached at all?
#
# Deliberately the first question. A devbox that does not answer is the
# case a push reporter cannot report, and it is why this program pulls.
if ! state=$(ssh_devbox dejima-devbox-audit drift --state 2>/dev/null); then
alert max "devbox unreachable" \
"The watcher could not collect from the devbox. It may be down, off the network, or refusing this key." || true
say "FAIL: could not reach the devbox"
return 1
fi
# Tested on the string, not on the file. `printf '%s\n' ""` writes a
# newline, so a file holding nothing useful is still one byte long and
# passes -s - which had an audit that returned nothing read as a valid
# state, and on a first run recorded it as the baseline.
if [ -z "$state" ]; then
alert max "devbox returned nothing" \
"The audit ran and produced no state. That is not a clean box; it is a check that did not run." || true
say "FAIL: empty state"
return 1
fi
printf '%s\n' "$state" > "$now"
# 2. Containment, which the devbox can answer for itself.
reach_rc=0
reach_out=$(ssh_devbox dejima-devbox-audit reach 2>&1) || reach_rc=$?
# 3. Drift, which it cannot: the baseline is here.
if [ ! -f "$BASE" ]; then
cp "$now" "$BASE"
say "First run. Baseline recorded from the devbox as it is now."
say " $(grep -c . "$BASE") entries. Take it on a box you believe is clean."
heartbeat
return 0
fi
diff --unchanged-line-format= --old-line-format='- %L' --new-line-format='+ %L' \
"$BASE" "$now" > "$now.diff" || true
if [ -s "$now.diff" ]; then
changed=1
body=$(summarise "$now.diff" | paste -sd', ' -)
fi
# 4. One alert per cycle, batching every finding.
#
# Not one per finding: an apt upgrade would otherwise arrive as forty
# pushes, and the next real one lands in a topic already muted.
if [ "$changed" = 1 ] && [ "$reach_rc" -ne 0 ]; then
alert max "devbox: changes and containment" \
"$body changed, and the containment check did not pass." || true
rc=1
elif [ "$changed" = 1 ]; then
alert high "devbox: unexplained changes" \
"$body changed since the last accepted state." || true
rc=1
elif [ "$reach_rc" -ne 0 ]; then
alert high "devbox: containment" \
"Nothing changed on the box, but the containment check did not pass." || true
rc=1
fi
{
printf '%s\n' "--- collected $(date -u +'%Y-%m-%dT%H:%M:%SZ')"
printf 'reach exit: %s\n%s\n\n' "$reach_rc" "$reach_out"
if [ "$changed" = 1 ]; then
printf 'changes against the baseline:\n'; cat "$now.diff"
else
printf 'no changes against the baseline\n'
fi
} > "$LAST"
if [ "$rc" -eq 0 ]; then
say "CLEAN: no changes, containment passed."
# Only on a cycle that completed and found nothing wrong. Pinging in a
# failure path would tell the dead-man's switch that all is well at the
# exact moment it is not.
heartbeat
else
say "ALERTED: see $LAST"
fi
return $rc
}
# Accepting the current state is a decision, so it is a separate command and
# never something a check does on its own.
cmd_accept() {
local state
require_config
install -d -m 0750 "$STATE_DIR"
state=$(ssh_devbox dejima-devbox-audit drift --state) || die "could not collect from the devbox"
[ -n "$state" ] || die "the devbox returned nothing - not accepting that as a baseline"
printf '%s\n' "$state" > "$BASE"
say "Baseline accepted: $(grep -c . "$BASE") entries in $BASE"
say " Take it on a box you believe is clean. One taken on a compromised"
say " machine records the compromise as normal and reports clean forever."
}
cmd_report() { [ -r "$LAST" ] && cat "$LAST" || say "no report yet - run $PROG check"; }
usage() {
cat >&2 <<USAGE
usage: $PROG [check|accept|report]
check collect from the devbox, diff against the baseline held here,
alert on any change or on containment failing, and send the
heartbeat only if the cycle completed clean
accept record the devbox's current state as the baseline
report the last cycle's detail, which is deliberately not in the alert
USAGE
}
case "${1:-check}" in
check) cmd_check ;;
accept) cmd_accept ;;
report) cmd_report ;;
-h|--help) usage ;;
*) say "$PROG: unknown command: $1"; usage; exit 64 ;;
esac
etc/config.example
+61
View File
@@ -0,0 +1,61 @@
# SPDX-License-Identifier: GPL-3.0-or-later
#
# Install at /etc/dejima-guard/config, mode 0640 root. It holds an ntfy token.
#
# Parsed, never sourced: key = value, and nothing here is executed. This file
# names a host to SSH to and URLs to post to, and sourcing it would make all of
# those arbitrary code from a file with no reason to be executable.
# --- the devbox this watches ------------------------------------------------
host = devbox.example.invalid
user = root
# Its own key, not a general-purpose administrative one, and restricted at the
# devbox end. In that account's authorized_keys:
#
# command="/usr/local/sbin/dejima-devbox-audit ${SSH_ORIGINAL_COMMAND##* }",\
# no-port-forwarding,no-agent-forwarding,no-pty ssh-ed25519 AAAA...
#
# What this program needs is two read-only subcommands. A key that can do only
# those is a key worth less to whoever takes this machine - and this machine is
# the one holding the evidence about the other one.
ssh_key = /var/lib/dejima-guard/id_ed25519
ssh_timeout = 10
# --- where alerts go --------------------------------------------------------
#
# A DIFFERENT TOPIC FROM THE ONE dejima PUSHES TO, and this is the part that
# matters rather than a tidiness preference.
#
# dejima's ntfy_url lives in ~/.config/dejima/config ON THE DEVBOX. Root there
# reads it. So a compromised devbox can publish to that topic - drowning it
# until you mute it, or forging an all-clear that never came from here.
#
# Give this its own topic, and give the devbox no credential for it. On a
# self-hosted ntfy with access control that is a token per topic. Deny the
# devbox READ on this one too: an intruder who can read the alerts about
# themselves learns exactly what the monitoring noticed and what it missed,
# which is worse than being able to write.
ntfy_url = https://ntfy.example.invalid/devbox-alerts
# ntfy_token = tk_...
# --- the dead-man's switch --------------------------------------------------
#
# An Uptime Kuma push monitor. Kuma expects a ping on a cadence and alerts when
# one does not arrive, which is exactly the shape wanted: this program pings
# only on a cycle that completed and found nothing wrong, so silence from it is
# itself the alarm.
#
# Without this, a watcher that dies is indistinguishable from a watcher with
# nothing to report. That is the one failure this design cannot catch about
# itself, and it is why the line is here rather than optional-by-omission.
#
# Anything speaking the same "GET this URL to say you are alive" shape works.
heartbeat_url = https://kuma.example.invalid/api/push/abcdef
# --- if you use something else ----------------------------------------------
#
# alert_command receives the title on the first line and the body on the second,
# on stdin. Set it and ntfy_url is ignored.
#
# alert_command = /usr/local/bin/my-alerter
systemd/dejima-guard.service
+20
View File
@@ -0,0 +1,20 @@
[Unit]
Description=Collect from the devbox and alert on what changed
Documentation=https://gitbox.branderson.io/dejima/dejima-guard
After=network-online.target
Wants=network-online.target
[Service]
Type=oneshot
ExecStart=@@BIN_DIR@@/dejima-guard check
# It listens on nothing and needs almost nothing. Whatever this machine is, it
# is not this program's to put at risk.
NoNewPrivileges=yes
PrivateTmp=yes
ProtectSystem=strict
ProtectHome=yes
ReadWritePaths=/var/lib/dejima-guard
ProtectKernelTunables=yes
ProtectControlGroups=yes
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
systemd/dejima-guard.timer
+16
View File
@@ -0,0 +1,16 @@
[Unit]
Description=Watch the devbox on a cadence
[Timer]
# Fifteen minutes sets two things at once, and they pull the same way: it is
# the longest an intruder has to notice the monitoring and scrub before a
# collection, and the granularity of the dead-man's switch. Shorter costs
# almost nothing; much longer and a compromise has room to tidy up.
OnBootSec=5min
OnUnitActiveSec=15min
# Without this a fleet of watchers all collect on the same second.
RandomizedDelaySec=60s
Persistent=true
[Install]
WantedBy=timers.target
test/guard.bats
+220
View File
@@ -0,0 +1,220 @@
#!/usr/bin/env bats
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2026 Brad Anderson
#
# The ways a watcher can be wrong are worse than the ways a check can be, because
# nobody is looking at a watcher. It runs from a timer and its output is an alert
# that either arrives or does not.
#
# Three of them are tested here and all three are silent failures:
#
# - alerting on nothing, until the topic is muted and the real one is missed;
# - staying quiet when the watched host stops answering, which is the case a
# push reporter cannot report and the reason this pulls;
# - sending the heartbeat on a cycle that failed, which tells the dead-man's
# switch all is well at the exact moment it is not.
#
# `ssh` and `curl` are stubbed on PATH rather than the functions being replaced,
# because what is under test includes whether this program calls them at all.
setup() {
REPO="$(cd "$BATS_TEST_DIRNAME/.." && pwd)"
TOOL="$REPO/bin/dejima-guard"
STUB="$BATS_TEST_TMPDIR/stub"; mkdir -p "$STUB"
export DEJIMA_GUARD_STATE="$BATS_TEST_TMPDIR/lib"
export DEJIMA_GUARD_CONF="$BATS_TEST_TMPDIR/config"
cat > "$DEJIMA_GUARD_CONF" <<EOF
host = devbox.example.invalid
ntfy_url = https://ntfy.example.invalid/alerts
heartbeat_url = https://kuma.example.invalid/api/push/abc
EOF
# Records every call so a test can assert what was and was not sent.
cat > "$STUB/curl" <<'EOF'
#!/bin/sh
printf '%s\n' "$*" >> "$DEJIMA_GUARD_STATE/curl.log"
exit 0
EOF
chmod +x "$STUB/curl"
mkdir -p "$DEJIMA_GUARD_STATE"
}
# An ssh that returns the given state for `drift --state`, and the given exit
# code for `reach`.
stub_ssh() { # stub_ssh STATE REACH_RC [SSH_RC]
printf '%s' "$1" > "$BATS_TEST_TMPDIR/state.txt"
cat > "$STUB/ssh" <<EOF
#!/bin/sh
[ "${3:-0}" -eq 0 ] || exit ${3:-0}
case "\$*" in
*"drift --state"*) cat "$BATS_TEST_TMPDIR/state.txt" ;;
*reach*) echo "PASS: the gateway is unreachable"; exit $2 ;;
esac
EOF
chmod +x "$STUB/ssh"
}
run_watch() { PATH="$STUB:$PATH" run "$TOOL" "$@"; }
curl_log() { cat "$DEJIMA_GUARD_STATE/curl.log" 2>/dev/null || true; }
alerts() { curl_log | grep -c 'Title:' || true; }
heartbeats() { curl_log | grep -c 'kuma.example.invalid' || true; }
# --- the first run ----------------------------------------------------------
@test "the first run records a baseline and does not alert" {
# Everything is new on a first run. Alerting on it would train the operator
# to dismiss the first alert they ever get from this.
stub_ssh "FILE aaa /etc/one" 0
run_watch check
[ "$status" -eq 0 ]
[ -f "$DEJIMA_GUARD_STATE/baseline" ]
[ "$(alerts)" = 0 ]
}
@test "an unchanged box alerts nothing and sends the heartbeat" {
stub_ssh "FILE aaa /etc/one" 0
run_watch check
run_watch check
[ "$status" -eq 0 ]
[ "$(alerts)" = 0 ]
[ "$(heartbeats)" -gt 0 ]
}
# --- the cases a push reporter cannot report --------------------------------
@test "a devbox that does not answer is alerted on, at max priority" {
# THE CASE THIS DESIGN EXISTS FOR. A reporter running on the box itself
# reports nothing here, forever, and nothing is wrong as far as anyone can
# see.
stub_ssh "FILE aaa /etc/one" 0
run_watch check # baseline
stub_ssh "" 0 255 # ssh itself fails
run_watch check
[ "$status" -ne 0 ]
[[ "$(curl_log)" == *"Priority: max"* ]]
[[ "$(curl_log)" == *unreachable* ]]
}
@test "an empty state is a failure, not a clean box" {
# A check that produced nothing has not found nothing. Treating the two the
# same is how a watcher reports all-clear on a box whose audit was removed.
stub_ssh "FILE aaa /etc/one" 0
run_watch check
stub_ssh "" 0
run_watch check
[ "$status" -ne 0 ]
[[ "$(curl_log)" == *"returned nothing"* ]]
}
@test "no heartbeat is sent on a cycle that failed" {
# Pinging the dead-man's switch in a failure path tells it all is well at
# the exact moment it is not, which is worse than not having one.
stub_ssh "FILE aaa /etc/one" 0
run_watch check
: > "$DEJIMA_GUARD_STATE/curl.log"
stub_ssh "" 0 255
run_watch check
[ "$(heartbeats)" = 0 ]
}
# --- drift ------------------------------------------------------------------
@test "a change against the baseline alerts once, not once per finding" {
# An apt upgrade otherwise arrives as forty pushes, and the next real alert
# lands in a topic already muted.
stub_ssh "FILE aaa /etc/one" 0
run_watch check
: > "$DEJIMA_GUARD_STATE/curl.log"
stub_ssh "FILE aaa /etc/one
FILE bbb /etc/two
FILE ccc /etc/three
UNIT backdoor.service" 0
run_watch check
[ "$status" -ne 0 ]
[ "$(alerts)" = 1 ]
}
@test "the alert body carries counts, never anything the devbox chose" {
# A compromised devbox controls every filename. Interpolating one into a
# push hands it a channel to the operator's phone - the thing dejima's own
# notification guarantee exists to prevent, defeated one layer out.
stub_ssh "FILE aaa /etc/one" 0
run_watch check
: > "$DEJIMA_GUARD_STATE/curl.log"
stub_ssh "FILE aaa /etc/one
FILE bbb /etc/evil-http-backdoor" 0
run_watch check
[[ "$(curl_log)" != *evil-http-backdoor* ]]
[[ "$(curl_log)" == *"file(s)"* ]]
}
@test "the detail is kept locally, where the alert deliberately does not put it" {
stub_ssh "FILE aaa /etc/one" 0
run_watch check
stub_ssh "FILE aaa /etc/one
FILE bbb /etc/evil-http-backdoor" 0
run_watch check
grep -q 'evil-http-backdoor' "$DEJIMA_GUARD_STATE/last-report"
}
@test "containment failing alerts even when nothing changed" {
stub_ssh "FILE aaa /etc/one" 0
run_watch check
: > "$DEJIMA_GUARD_STATE/curl.log"
stub_ssh "FILE aaa /etc/one" 1
run_watch check
[ "$status" -ne 0 ]
[[ "$(curl_log)" == *containment* ]]
}
@test "both wrong at once is one alert, at max" {
stub_ssh "FILE aaa /etc/one" 0
run_watch check
: > "$DEJIMA_GUARD_STATE/curl.log"
stub_ssh "FILE bbb /etc/two" 1
run_watch check
[ "$(alerts)" = 1 ]
[[ "$(curl_log)" == *"Priority: max"* ]]
}
# --- accepting --------------------------------------------------------------
@test "accept replaces the baseline" {
stub_ssh "FILE aaa /etc/one" 0
run_watch check
stub_ssh "FILE bbb /etc/two" 0
run_watch accept
[ "$status" -eq 0 ]
grep -q 'FILE bbb' "$DEJIMA_GUARD_STATE/baseline"
run_watch check
[ "$status" -eq 0 ]
}
@test "accept refuses an empty state rather than baselining nothing" {
# A baseline of nothing compares clean against everything, forever.
stub_ssh "" 0
run_watch accept
[ "$status" -ne 0 ]
[ ! -f "$DEJIMA_GUARD_STATE/baseline" ]
}
# --- config -----------------------------------------------------------------
@test "a URL without a scheme is refused rather than guessed at" {
# curl reads a leading -K/path as an option taking the request from a file.
# dejima refuses these for the same reason and this follows it.
stub_ssh "FILE aaa /etc/one" 0
printf 'host = devbox.example.invalid\nntfy_url = ntfy.example.invalid/x\n' > "$DEJIMA_GUARD_CONF"
run_watch check
[ -f "$DEJIMA_GUARD_STATE/baseline" ] || true
stub_ssh "FILE zzz /etc/one" 0
run_watch check
[[ "$output" == *"must start with http"* ]]
}
@test "no host configured is refused, not silently skipped" {
printf 'ntfy_url = https://ntfy.example.invalid/x\n' > "$DEJIMA_GUARD_CONF"
stub_ssh "FILE aaa /etc/one" 0
run_watch check
[ "$status" -ne 0 ]
[[ "$output" == *"no host"* ]]
}
test/snippets.bats
+82
View File
@@ -0,0 +1,82 @@
#!/usr/bin/env bats
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2026 Brad Anderson
#
# Every ```sh block in the documentation parses as shell.
#
# The runbooks are the product, and a command in one is not an illustration -
# it is something an operator pastes into a root shell on a hypervisor while
# following the page. A block that does not parse is a defect in the
# deliverable, exactly as a dangling link is.
#
# It exists because of a near-miss: restructuring prose around a fenced block
# turned a `\` line continuation into `\\`, which renders identically, reads
# as prose in a diff, and breaks for whoever pastes it. Nothing else here looks
# inside a fence, and nobody counts backslashes at end of line.
#
# IT PARSES AND DOES NOT EXECUTE, which is the only safe thing to do with a
# file full of `sudo iptables`. So it checks syntax, not whether a command is
# correct or does what the prose around it claims.
#
# PLACEHOLDERS ARE SUBSTITUTED FIRST. `<name>` is this repository's idiom, not
# shell, and shell reads it as redirection - so whether a block parsed would
# otherwise depend on how many angle brackets landed on a line.
# `try <forge-ip> 443` parses by accident as two redirects; `ssh <you>@<vm-ip>`
# does not, because the trailing `>` has nothing after it. The pattern requires
# a letter after the `<`, which leaves `3<>/dev/tcp/...` and `<<EOF` intact -
# both real shell, and both things a naive substitution would corrupt into a
# passing test.
setup() {
REPO="$(cd "$BATS_TEST_DIRNAME/.." && pwd)"
}
@test "every fenced sh block parses as shell" {
work="$BATS_TEST_TMPDIR/snippets"
mkdir -p "$work"
# Extracted to files rather than piped, so bash -n reports a line number
# inside the block and the .loc file turns it back into a place in the docs.
while IFS= read -r f; do
safe="$(printf '%s' "$f" | tr '/.' '__')"
awk -v dir="$work" -v pfx="$safe" -v file="$f" '
/^```sh$/ {
inblock = 1; n++
out = dir "/" pfx "_" n ".sh"
print file ":" NR > (out ".loc"); close(out ".loc")
next
}
/^```$/ { if (inblock) { close(out); inblock = 0 } ; next }
inblock { print >> out }
' "$REPO/$f"
done < <(cd "$REPO" && git ls-files '*.md')
checked=0
fails=""
for snippet in "$work"/*.sh; do
[ -e "$snippet" ] || continue
checked=$((checked + 1))
sed -i -E 's/<[a-zA-Z][^<>]*>/PLACEHOLDER/g' "$snippet"
if ! err="$(bash -n "$snippet" 2>&1)"; then
fails="$fails\n $(cat "$snippet.loc")\n$(printf '%s' "$err" | sed 's/^/ /')"
fi
done
# A pass that checked nothing is the failure this suite exists to avoid, and
# an extractor that silently stops matching is exactly how it would happen.
[ "$checked" -gt 0 ] || { echo "no sh blocks found - the extractor is broken, not the docs" >&2; false; }
if [ -n "$fails" ]; then
printf 'fenced sh blocks that do not parse:%b\n' "$fails" >&2
false
fi
}
@test "the guard fails when a block is broken, rather than passing quietly" {
# The same shape as links.bats's own self-check. A guard that cannot fail is
# indistinguishable from one that always passes, and this one runs over
# files nobody expects to break.
printf 'x() { echo a \\\\\n && echo b; }\n' > "$BATS_TEST_TMPDIR/broken.sh"
run bash -n "$BATS_TEST_TMPDIR/broken.sh"
[ "$status" -ne 0 ]
}