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Contextual age scoring with stacking and SAN discount, directional multi-resolver DNS validation, surfaced fetch errors, and GPLv3 licensing

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markmental 2026-09-08 21:49:25 -04:00
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AGENTS.md
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# Built Go binary (replaces bash script in place; bash kept as isthislegit.sh)
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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
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Some devices are designed to deny users access to install or run
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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
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permission, would make you directly or secondarily liable for
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public, and in some countries other activities as well.
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parties to make or receive copies. Mere interaction with a user through
a computer network, with no transfer of a copy, is not conveying.
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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
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1. Source Code.
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The Corresponding Source need not include anything that users
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The Corresponding Source for a work in source code form is that
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All rights granted under this License are granted for the term of
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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
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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
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All other non-permissive additional terms are considered "further
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You may not propagate or modify a covered work except as expressly
provided under this License. Any attempt otherwise to propagate or
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However, if you cease all violation of this License, then your
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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
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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>.

25
README.md
View file

@ -4,7 +4,14 @@ Domain Impersonation & OSINT Triage Tool.
`isthislegit` compares a known-legitimate domain (target) against a suspect
domain using DNS resolution, X.509 TLS certificates, and RDAP registration
data to produce a deterministic risk score and verdict. It ships as a single
data to produce a deterministic risk score and verdict. DNS answers are
cross-checked across the system resolver, 1.1.1.1, and 8.8.8.8 for
split-brain or hijacking signals (state consistency only — raw addresses
are never compared, so CDN/GeoDNS fronting stays quiet). Each unique
domain is probed once and the outcomes reused; even identical
target/suspect pairs run the full pipeline (verdict forced to legitimate).
System-dark/public-live suppression splits score on the suspect, while
split-horizon shapes stay display-only. It ships as a single
static binary built on the Go standard library (plus `golang.org/x/sync` for
the concurrent fetch pipeline) — no `curl`, `openssl`, `jq`, or `dig`
required.
@ -146,8 +153,14 @@ VERDICT: LIKELY UNRELATED / MISCONFIGURED
| Signal | Points |
|---------------------------------------------|--------|
| Suspect domain age < 30 days (CRITICAL) | +80 |
| Suspect domain age 30–89 days (WARNING) | +80 |
| Suspect < 30d (CRITICAL), stacked w/ signal | +80 |
| Suspect < 30d (CRITICAL), isolated | +40 |
| Suspect 30–89d (WARNING), stacked w/ signal | +40 |
| Suspect 30–89d (WARNING), isolated | +20 |
| Shared cert infrastructure (halves age tier)| x0.5 |
| Identical target/suspect (forced LEGITIMATE) | +0 |
| Resolution tampering: suppression split (suspect) | +50 |
| DNS split-horizon / target-side (display only) | +0 |
| Cert downgrade: target EV/OV vs suspect DV | +40 |
| Registrar mismatch | +30 |
| Same-class issuer difference (display only) | +0 |
@ -178,3 +191,9 @@ internal/rdap RDAP client, creation date and registrar extraction
internal/score Risk scoring and verdict mapping
internal/report Human, JSON, scale, and verbose renderers
```
## License
Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL). `isthislegit` is free
software licensed under the GNU General Public License v3 — see
[LICENSE](LICENSE) for the full text.

85
cmd/isthislegit/main.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Command isthislegit compares a known-legitimate domain against a suspect
// domain using X.509 TLS certificates, RDAP registration data, and DNS
// resolution to produce a risk score and verdict. Stdlib only, plus
@ -54,11 +59,12 @@ type domainResult struct {
info score.DomainData
cert *cert.Details
rdap *rdap.Result
cons dns.Consistency
rdapErr error
certErr error
}
func fetchDomain(ctx context.Context, client *http.Client, domain string, now time.Time, perCall time.Duration) domainResult {
func fetchDomain(ctx context.Context, client *http.Client, domain string, now time.Time, perCall time.Duration, dc dns.DomainCheck) domainResult {
res := domainResult{info: score.DomainData{Domain: domain}}
var g errgroup.Group
@ -75,12 +81,17 @@ func fetchDomain(ctx context.Context, client *http.Client, domain string, now ti
cd, res.certErr = c, err
return err
})
// Fail-open per field; the root causes are kept for the
// fail-closed verdict gate below.
// DNS was probed once in pre-flight; reuse those outcomes here so no
// resolver is queried twice. Fail-open per field; the root causes are
// kept for the fail-closed verdict gate below.
_ = g.Wait()
res.rdap = rd
res.cert = cd
res.cons = dc.Consistency
res.info.DNSTampered = res.cons.Tampered
res.info.DNSSplit = res.cons.Kind
res.info.DNSDetail = res.cons.Detail
res.info.Date = rdap.RegistrationDate(rd)
res.info.Registrar = rdap.Registrar(rd)
@ -187,20 +198,44 @@ func run() int {
ctx, cancel := context.WithTimeout(context.Background(), globalTimeout)
defer cancel()
// DNS pre-flight for both domains in parallel (fail fast like bash check_dns).
var dg errgroup.Group
for _, d := range []string{legit, suspect} {
d := d
dg.Go(func() error {
if err := dns.CheckDNS(ctx, d, perCall); err != nil {
return fmt.Errorf("domain '%s' failed DNS resolution (NXDOMAIN or offline). Aborting", d)
}
// DNS pre-flight probes each unique domain once across the system and
// pinned resolvers. Outcomes are reused by the fetch stage, so no
// resolver is queried twice for one domain.
uniq := []string{legit}
if suspect != legit {
uniq = append(uniq, suspect)
}
type domainProbe struct {
domain string
check dns.DomainCheck
}
probes := make([]domainProbe, len(uniq))
var pg errgroup.Group
for i := range uniq {
pg.Go(func() error {
probes[i] = domainProbe{domain: uniq[i], check: dns.CheckDomain(ctx, uniq[i], perCall)}
return nil
})
}
if err := dg.Wait(); err != nil {
fmt.Fprintf(os.Stderr, "[!] Error: %v.\n", err)
return 1
_ = pg.Wait()
probeFor := func(domain string) dns.DomainCheck {
for _, p := range probes {
if p.domain == domain {
return p.check
}
}
return dns.DomainCheck{}
}
for _, rd := range []struct{ role, domain string }{{"target", legit}, {"suspect", suspect}} {
dc := probeFor(rd.domain)
if !dc.SystemLive && dc.PublicLive {
fmt.Fprintf(os.Stderr, "[!] Error: Domain '%s' (%s) suppressed locally: system resolver reports NXDOMAIN while public resolvers resolve live — possible DNS hijacking. Aborting.\n", rd.domain, rd.role)
return 1
}
if !dc.SystemLive {
fmt.Fprintf(os.Stderr, "[!] Error: Domain '%s' (%s) failed DNS resolution (NXDOMAIN or offline). Aborting.\n", rd.domain, rd.role)
return 1
}
}
client := &http.Client{}
@ -210,17 +245,21 @@ func run() int {
}
now := time.Now()
var target, sus domainResult
fetched := make([]domainResult, len(uniq))
var fg errgroup.Group
fg.Go(func() error {
target = fetchDomain(ctx, client, legit, now, perCall)
return nil
})
fg.Go(func() error {
sus = fetchDomain(ctx, client, suspect, now, perCall)
return nil
})
for i := range uniq {
fg.Go(func() error {
fetched[i] = fetchDomain(ctx, client, uniq[i], now, perCall, probeFor(uniq[i]))
return nil
})
}
_ = fg.Wait()
results := make(map[string]domainResult, len(uniq))
for i, d := range uniq {
results[d] = fetched[i]
}
target := results[legit]
sus := results[suspect]
if err := score.VerifyDataQuality(target.info, sus.info); err != nil {
msg := fmt.Sprintf("[!] Error: %v.", err)

5
compile.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Command compile is the build driver for isthislegit. It cross-compiles
// ./cmd/isthislegit for the requested platform/arch matrix:
//

2
docs/cert.html
View file

@ -65,5 +65,7 @@ already-parsed leaf certificate. Preferred entry point for tests.</p>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func (d *Details) SANsString() string</pre></td></tr></table>
<p>Joins SANs with <tt>", "</tt> for display, or returns
<tt>"Unknown"</tt> when empty. Nil-receiver safe.</p>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

73
docs/dns.html
View file

@ -5,8 +5,9 @@
</head>
<body bgcolor="#002b36" text="#a3b8b9" link="#859900" vlink="#b58900">
<font color="#b58900"><h1>Package dns</h1></font>
<p>Domain normalization, syntax validation, and DNS pre-flight resolution
checks. Source: <tt>internal/dns/dns.go</tt>.</p>
<p>Domain normalization, syntax validation, DNS pre-flight resolution
checks, and multi-resolver consistency cross-checks. Sources:
<tt>internal/dns/dns.go</tt>, <tt>internal/dns/resolvers.go</tt>.</p>
<hr>
<a name="NormalizeDomain"></a>
@ -28,17 +29,69 @@ input before any network call.</p>
dns.ValidSyntax("no-dot") // =&gt; false</pre></td></tr></table>
<hr>
<a name="CheckDNS"></a>
<font color="#859900"><h2>CheckDNS</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func CheckDNS(ctx context.Context, domain string, timeout time.Duration) error</pre></td></tr></table>
<p>Aborts early on NXDOMAIN or unresolvable names via
<tt>net.DefaultResolver.LookupIP</tt> with the given deadline. Returns
<tt>nil</tt> when at least one IPv4 address resolves, an error otherwise.</p>
<a name="DomainCheck"></a>
<font color="#859900"><h2>DomainCheck</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>type DomainCheck struct {
SystemLive bool
PublicLive bool
Consistency Consistency
}</pre></td></tr></table>
<p>One domain's full probe: system liveness for pre-flight gating, public
liveness for suppression attribution, and the aggregate consistency
verdict. The pre-flight gate aborts on system failure and reuses these
outcomes downstream, so each resolver is queried exactly once per
domain.</p>
<hr>
<a name="CheckDomain"></a>
<font color="#859900"><h2>CheckDomain</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func CheckDomain(ctx context.Context, domain string, timeout time.Duration) DomainCheck</pre></td></tr></table>
<p>Probes the system resolver and pinned public resolvers once. Use
<tt>SystemLive</tt> for NXDOMAIN gating and <tt>Consistency</tt> for
scoring and messaging.</p>
<hr>
<a name="Consistency"></a>
<font color="#859900"><h2>Consistency</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>type Consistency struct {
Checked bool
Tampered bool
Kind SplitKind
Detail string
}</pre></td></tr></table>
<p>Verdict of a multi-resolver cross-check. <tt>Detail</tt> names the
disagreeing resolvers and the split kind when tampered.</p>
<hr>
<a name="SplitKind"></a>
<font color="#859900"><h2>SplitKind</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>const (
SplitNone SplitKind = iota
SplitSuppression
SplitHorizon
SplitNS
)</pre></td></tr></table>
<p>Split direction. Suppression (system dark, public live) signals local
tampering; horizon (system live, public dark) is the expected split-horizon
shape of internal names and never scores; NS marks delegation splits.</p>
<hr>
<a name="CheckConsistency"></a>
<font color="#859900"><h2>CheckConsistency</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func CheckConsistency(ctx context.Context, domain string, timeout time.Duration) Consistency</pre></td></tr></table>
<p>Queries the system resolver plus pinned 1.1.1.1 and 8.8.8.8 servers in
parallel (stdlib <tt>net.Resolver</tt> with a pinned dialer; filtered
resolvers excluded by design). Flags NXDOMAIN-vs-live splits and NS
delegation splits; raw A records are never compared, so CDN/GeoDNS churn
stays quiet. Inconclusive resolvers abstain, and fewer than two conclusive
votes is never tampering. Never fails closed.</p>
<table border="1" cellpadding="4">
<tr><th>Parameter</th><th>Description</th></tr>
<tr><td><tt>ctx</tt></td><td>Parent context; the global 15 second budget.</td></tr>
<tr><td><tt>domain</tt></td><td>Already-normalized domain to resolve.</td></tr>
<tr><td><tt>timeout</tt></td><td>Per-call deadline (the CLI --timeout value).</td></tr>
<tr><td><tt>domain</tt></td><td>Already-normalized domain to cross-check.</td></tr>
<tr><td><tt>timeout</tt></td><td>Per-resolver deadline (the CLI --timeout value).</td></tr>
</table>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

2
docs/index.html
View file

@ -18,6 +18,8 @@
<li><a href="report.html">Package report</a></li>
<li><a href="main.html">Command main</a></li>
</ul>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</noframes>
</frameset>

8
docs/main.html
View file

@ -31,7 +31,11 @@ include the underlying fetch cause(s).</p>
<font color="#859900"><h2>Flow</h2></font>
<ol>
<li>DNS pre-flight for both domains in parallel; any failure aborts.</li>
<li>DNS pre-flight probes each unique domain once across the system and
pinned resolvers; system failure aborts (with hijack-aware messaging when
public resolvers resolve live). Outcomes are reused downstream, so no
resolver is queried twice - identical domains are fetched once and the
result shared.</li>
<li>Per-domain fetch in parallel: RDAP
(<a href="rdap.html#Query">rdap.Query</a>) plus TLS
(<a href="cert.html#InspectDomain">cert.InspectDomain</a>) concurrently.
@ -51,5 +55,7 @@ plus <a href="report.html#Verbose">report.Verbose</a> when verbose.</li>
output, and <tt>--scale</tt> header. Build target:
<tt>CGO_ENABLED=0 go build -ldflags="-s -w" -o isthislegit
./cmd/isthislegit</tt>.</p>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

8
docs/nav.html
View file

@ -21,7 +21,11 @@
<ul>
<li><a href="dns.html#NormalizeDomain" target="content">NormalizeDomain</a></li>
<li><a href="dns.html#ValidSyntax" target="content">ValidSyntax</a></li>
<li><a href="dns.html#CheckDNS" target="content">CheckDNS</a></li>
<li><a href="dns.html#DomainCheck" target="content">DomainCheck</a></li>
<li><a href="dns.html#CheckDomain" target="content">CheckDomain</a></li>
<li><a href="dns.html#SplitKind" target="content">SplitKind</a></li>
<li><a href="dns.html#Consistency" target="content">Consistency</a></li>
<li><a href="dns.html#CheckConsistency" target="content">CheckConsistency</a></li>
</ul>
<p><b>cert</b></p>
<ul>
@ -59,5 +63,7 @@
<li><a href="report.html#JSON" target="content">JSON</a></li>
<li><a href="report.html#Verbose" target="content">Verbose</a></li>
</ul>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

22
docs/overview.html
View file

@ -44,6 +44,16 @@ cause(s).</p>
<tt>--help</tt>), <tt>1</tt> on bad flags, invalid domains, DNS failure, or
failed data-quality verification.</p>
<font color="#859900"><h2>DNS Consistency</h2></font>
<p>Each domain is probed once by the system resolver plus pinned 1.1.1.1 and
8.8.8.8 servers, and the outcomes are reused downstream. Only state is
compared, never raw addresses: system-dark/public-live suppression splits
and NS delegation splits flag tampering (+50 on the suspect), while
system-live/public-dark split-horizon shapes and target-side splits stay
display-only NOTEs. CDN/GeoDNS address churn stays quiet. Inconclusive
resolvers abstain; filtered resolvers are excluded by design. The
pre-flight gate aborts on system failure with hijack-aware messaging.</p>
<font color="#859900"><h2>Embedded Systems</h2></font>
<p>The tool runs on embedded ARM devices (verified on a Miyoo Mini Plus),
but minimal firmware often ships without a CA certificate store. DNS and
@ -55,8 +65,14 @@ where possible, otherwise use <tt>-k/--insecure</tt> as a last resort.</p>
<font color="#859900"><h2>Scoring Scale</h2></font>
<table border="1" cellpadding="4">
<tr><th>Signal</th><th>Points</th></tr>
<tr><td>Suspect domain age &lt; 30 days (CRITICAL)</td><td>+80</td></tr>
<tr><td>Suspect domain age 30-89 days (WARNING)</td><td>+80</td></tr>
<tr><td>Suspect &lt; 30d (CRITICAL), stacked w/ signal</td><td>+80</td></tr>
<tr><td>Suspect &lt; 30d (CRITICAL), isolated</td><td>+40</td></tr>
<tr><td>Suspect 30-89d (WARNING), stacked w/ signal</td><td>+40</td></tr>
<tr><td>Suspect 30-89d (WARNING), isolated</td><td>+20</td></tr>
<tr><td>Shared cert infrastructure (halves age tier)</td><td>x0.5</td></tr>
<tr><td>Identical target/suspect (forced LEGITIMATE)</td><td>+0</td></tr>
<tr><td>Resolution tampering: suppression split (suspect)</td><td>+50</td></tr>
<tr><td>DNS split-horizon / target-side (display only)</td><td>+0</td></tr>
<tr><td>Cert downgrade: target EV/OV vs suspect DV</td><td>+40</td></tr>
<tr><td>Registrar mismatch</td><td>+30</td></tr>
<tr><td>Same-class issuer difference (display only)</td><td>+0</td></tr>
@ -79,5 +95,7 @@ where possible, otherwise use <tt>-k/--insecure</tt> as a last resort.</p>
<li><a href="report.html"><b>report</b></a> - human, JSON, scale, and verbose renderers.</li>
<li><a href="main.html"><b>main</b></a> - CLI entry point and fetch orchestration.</li>
</ul>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

2
docs/rdap.html
View file

@ -65,5 +65,7 @@ Non-2xx status and invalid JSON are errors.</p>
<p>Best-effort registrar name, or <tt>"Unknown"</tt>. Prefers entities with
the <tt>registrar</tt> role, falling back to the first vCard
<tt>fn</tt> property. Nil-safe.</p>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

2
docs/report.html
View file

@ -60,5 +60,7 @@ newline for pipeline use.</p>
<p>Raw policy OIDs with classes, per-domain TLS details (issuer, subject,
validity, SANs), and raw RDAP JSON for both domains. Missing data renders
an explicit unavailable notice per section.</p>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

18
docs/score.html
View file

@ -5,7 +5,8 @@
</head>
<body bgcolor="#002b36" text="#a3b8b9" link="#859900" vlink="#b58900">
<font color="#b58900"><h1>Package score</h1></font>
<p>Deterministic risk scoring: domain-age check (+80), certificate
<p>Deterministic risk scoring: domain-age check (contextual tiers with
stacking and shared-cert discount), certificate
downgrade check (+40), and registrar mismatch (+30), mapped onto a
four-tier verdict. Sources: <tt>internal/score/score.go</tt>,
<tt>internal/score/date.go</tt>.</p>
@ -56,11 +57,18 @@ The CLI aborts instead of printing a verdict built on missing data.</p>
<a name="Score"></a>
<font color="#859900"><h2>Score</h2></font>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func Score(target, suspect DomainData) Result</pre></td></tr></table>
<p>Applies the three signals. Suspect age under 30 days adds 80 with a
CRITICAL flag; 30-89 days adds 80 with a WARNING flag. Target EV/OV versus
<p>Applies the signals. Identical domains force score zero and LEGITIMATE
while still attaching DNS NOTEs. Suspect age
is contextual: the full tier (&lt; 30d: 80, 30-89d: 40) needs company
(registrar mismatch or cert downgrade), otherwise the next tier down;
shared certificate infrastructure (either domain in the other's SANs,
exactly or via parent wildcard) halves whatever remains. Target EV/OV versus
suspect DV adds 40 as DOWNGRADE; a same-class issuer difference is a
display-only NOTE (+0). Case-insensitive registrar mismatch adds 30,
skipped when either side is unknown.</p>
skipped when either side is unknown. Suspect-side DNS suppression and NS
splits add 50; split-horizon shapes and anything target-side are
display-only NOTEs (+0). Identical domains force score zero and LEGITIMATE
while still attaching DNS NOTEs.</p>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>r := score.Score(target, suspect)
// r.Score, r.Findings, r.Verdict, r.AgeFlag</pre></td></tr></table>
@ -84,5 +92,7 @@ sentinel or garbage value fails by design.</p>
<table border="0" cellpadding="8" width="100%"><tr><td bgcolor="#073642"><pre>func AgeDays(ymd string, now time.Time) (days int, ok bool)</pre></td></tr></table>
<p>Whole days between <tt>ymd</tt> and <tt>now</tt>; <tt>ok</tt> is false
when <tt>ymd</tt> is unparseable.</p>
<hr>
<font color="#b58900">Licensed under the GNU General Public License v3 - Mark Robillard Jr (MARKMENTAL)</font>
</body>
</html>

5
internal/cert/cert.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Package cert fetches leaf X.509 certificates and classifies the
// CA/Browser Forum validation level from policy OIDs.
// Mirrors bash get_cert_issuer / get_cert_sans / get_cert_class.

5
internal/cert/cert_test.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package cert
import (

26
internal/dns/dns.go
View file

@ -1,14 +1,15 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Package dns provides domain normalization, syntax validation,
// and DNS pre-flight resolution checks.
// and multi-resolver resolution checks.
package dns
import (
"context"
"fmt"
"net"
"regexp"
"strings"
"time"
)
var domainRe = regexp.MustCompile(`^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?(\.[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?)+$`)
@ -35,18 +36,3 @@ func NormalizeDomain(d string) string {
func ValidSyntax(d string) bool {
return domainRe.MatchString(d)
}
// CheckDNS aborts early on NXDOMAIN / unresolvable names.
// Mirrors bash check_dns (dig +short A). Uses the stdlib resolver.
func CheckDNS(ctx context.Context, domain string, timeout time.Duration) error {
ctx, cancel := context.WithTimeout(ctx, timeout)
defer cancel()
addrs, err := net.DefaultResolver.LookupIP(ctx, "ip4", domain)
if err != nil {
return fmt.Errorf("domain '%s' failed DNS resolution (NXDOMAIN or offline): %w", domain, err)
}
if len(addrs) == 0 {
return fmt.Errorf("domain '%s' failed DNS resolution (NXDOMAIN or offline): no addresses", domain)
}
return nil
}

5
internal/dns/dns_test.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package dns
import "testing"

233
internal/dns/resolvers.go Normal file
View file

@ -0,0 +1,233 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Multi-resolver consistency checks: cross-validate the system resolver
// against pinned public resolvers to catch split-brain DNS, local resolver
// poisoning, or targeted routing manipulation.
//
// Only resolution *state* is compared, never raw A records: CDN and GeoDNS
// fronting legitimately returns different IPs per egress geography, while
// existence (live vs NXDOMAIN) and NS delegation stay stable. Tampering
// requires two conclusive votes; timeouts and lookup errors abstain.
package dns
import (
"context"
"errors"
"fmt"
"net"
"sort"
"strings"
"sync"
"time"
)
// pinned public resolvers. Filtered resolvers (Quad9, OpenDNS) are
// deliberately excluded: they alter answers by design and would
// manufacture discrepancies.
var pinnedServers = []struct {
name string
addr string
}{
{"1.1.1.1", "1.1.1.1:53"},
{"8.8.8.8", "8.8.8.8:53"},
}
// Consistency is the verdict of a multi-resolver cross-check.
type Consistency struct {
Checked bool
Tampered bool
Kind SplitKind
Detail string
}
// SplitKind names the direction of a resolution split. Suppression
// (system dark, public live) signals local tampering; horizon
// (system live, public dark) is the expected split-horizon shape for
// internal names and never scores.
type SplitKind int
const (
SplitNone SplitKind = iota
SplitSuppression
SplitHorizon
SplitNS
)
type outcomeKind int
const (
outcomeLive outcomeKind = iota
outcomeNXDomain
outcomeInconclusive
)
type resolverOutcome struct {
name string
kind outcomeKind
ns []string
}
// pinnedResolver dials one DNS server directly, bypassing resolv.conf.
func pinnedResolver(addr string) *net.Resolver {
return &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, _ string) (net.Conn, error) {
var d net.Dialer
return d.DialContext(ctx, network, addr)
},
}
}
// DomainCheck is one domain's full probe: system liveness for gating,
// public liveness for suppression attribution, and the aggregate verdict.
type DomainCheck struct {
SystemLive bool
PublicLive bool
Consistency Consistency
}
// CheckDomain probes the system resolver and pinned public resolvers once
// and returns everything callers need: gating votes plus the aggregate
// consistency verdict. Query every resolver exactly once per domain.
func CheckDomain(ctx context.Context, domain string, timeout time.Duration) DomainCheck {
names := []string{"system"}
resolvers := []*net.Resolver{net.DefaultResolver}
for _, s := range pinnedServers {
names = append(names, s.name)
resolvers = append(resolvers, pinnedResolver(s.addr))
}
outcomes := make([]resolverOutcome, len(resolvers))
var wg sync.WaitGroup
for i := range resolvers {
wg.Add(1)
go func(i int) {
defer wg.Done()
callCtx, cancel := context.WithTimeout(ctx, timeout)
defer cancel()
addrs, err := resolvers[i].LookupIP(callCtx, "ip4", domain)
out := resolverOutcome{name: names[i], kind: classifyOutcome(addrs, err)}
if out.kind == outcomeLive {
if nss, nsErr := resolvers[i].LookupNS(callCtx, domain); nsErr == nil {
for _, ns := range nss {
out.ns = append(out.ns, normalizeNS(ns.Host))
}
}
}
outcomes[i] = out
}(i)
}
wg.Wait()
var dc DomainCheck
for _, o := range outcomes {
if o.name == "system" && o.kind == outcomeLive {
dc.SystemLive = true
}
if o.name != "system" && o.kind == outcomeLive {
dc.PublicLive = true
}
}
kind, detail := detectSplit(domain, outcomes)
dc.Consistency = Consistency{Checked: true, Tampered: kind == SplitSuppression || kind == SplitNS, Kind: kind, Detail: detail}
return dc
}
// CheckConsistency queries the system resolver and pinned public resolvers
// in parallel and reports state splits. Never fails closed: inconclusive
// resolvers abstain, and agreement (or too few votes) is not tampering.
func CheckConsistency(ctx context.Context, domain string, timeout time.Duration) Consistency {
return CheckDomain(ctx, domain, timeout).Consistency
}
// classifyOutcome maps a lookup result to live, NXDOMAIN, or inconclusive.
// Anything that is not a clean answer or an authoritative NXDOMAIN abstains.
func classifyOutcome(addrs []net.IP, err error) outcomeKind {
if err != nil {
var dnsErr *net.DNSError
if errors.As(err, &dnsErr) && dnsErr.IsNotFound {
return outcomeNXDomain
}
return outcomeInconclusive
}
if len(addrs) == 0 {
return outcomeInconclusive
}
return outcomeLive
}
// normalizeNS lowercases and strips the trailing root dot for comparison.
func normalizeNS(host string) string {
return strings.TrimSuffix(strings.ToLower(strings.TrimSpace(host)), ".")
}
// nsSetsEqual compares normalized NS sets as sets, ignoring order.
func nsSetsEqual(a, b []string) bool {
if len(a) != len(b) {
return false
}
set := make(map[string]int, len(a))
for _, ns := range a {
set[ns]++
}
for _, ns := range b {
set[ns]--
if set[ns] < 0 {
return false
}
}
return true
}
// detectSplit flags existence and NS-delegation splits across conclusive
// resolver outcomes, with direction: system-dark/public-live is
// suppression (local tampering shape), system-live/public-dark is the
// split-horizon shape of internal names. Pure function; safe to unit test.
func detectSplit(domain string, outcomes []resolverOutcome) (SplitKind, string) {
sysKind := outcomeInconclusive
var pubLive, pubNX []string
var nsVotes [][]string
var nsNames []string
for _, o := range outcomes {
if o.name == "system" {
sysKind = o.kind
}
if o.name != "system" && o.kind == outcomeLive {
pubLive = append(pubLive, o.name)
}
if o.name != "system" && o.kind == outcomeNXDomain {
pubNX = append(pubNX, o.name)
}
if o.kind == outcomeLive && len(o.ns) > 0 {
nsVotes = append(nsVotes, o.ns)
nsNames = append(nsNames, o.name)
}
}
if sysKind == outcomeNXDomain && len(pubLive) > 0 {
sort.Strings(pubLive)
return SplitSuppression, fmt.Sprintf("suppression pattern on %s: system reports NXDOMAIN while %s resolve live",
domain, strings.Join(pubLive, ", "))
}
if sysKind == outcomeLive && len(pubNX) > 0 {
sort.Strings(pubNX)
return SplitHorizon, fmt.Sprintf("split-horizon pattern on %s: system resolves live while %s report NXDOMAIN",
domain, strings.Join(pubNX, ", "))
}
if sysKind == outcomeInconclusive && len(pubLive) > 0 && len(pubNX) > 0 {
sort.Strings(pubLive)
sort.Strings(pubNX)
return SplitSuppression, fmt.Sprintf("existence split on %s: %s report NXDOMAIN while %s resolve live (system inconclusive)",
domain, strings.Join(pubNX, ", "), strings.Join(pubLive, ", "))
}
for i := 1; i < len(nsVotes); i++ {
if !nsSetsEqual(nsVotes[0], nsVotes[i]) {
sort.Strings(nsNames)
return SplitNS, fmt.Sprintf("NS delegation split on %s across resolvers (%s)",
domain, strings.Join(nsNames, ", "))
}
}
return SplitNone, ""
}

115
internal/dns/resolvers_test.go Normal file
View file

@ -0,0 +1,115 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package dns
import (
"errors"
"net"
"strings"
"testing"
)
func TestClassifyOutcome(t *testing.T) {
live := classifyOutcome([]net.IP{net.ParseIP("93.184.216.34")}, nil)
if live != outcomeLive {
t.Errorf("addrs, no error = %v, want live", live)
}
nx := classifyOutcome(nil, &net.DNSError{Err: "no such host", IsNotFound: true})
if nx != outcomeNXDomain {
t.Errorf("not-found DNSError = %v, want nxdomain", nx)
}
timeout := classifyOutcome(nil, &net.DNSError{Err: "i/o timeout", IsTimeout: true})
if timeout != outcomeInconclusive {
t.Errorf("timeout DNSError = %v, want inconclusive", timeout)
}
generic := classifyOutcome(nil, errors.New("boom"))
if generic != outcomeInconclusive {
t.Errorf("generic error = %v, want inconclusive", generic)
}
empty := classifyOutcome(nil, nil)
if empty != outcomeInconclusive {
t.Errorf("empty answer = %v, want inconclusive", empty)
}
}
func TestNsSetsEqual(t *testing.T) {
a := []string{"ns1.example.com", "ns2.example.com"}
b := []string{"ns2.example.com", "ns1.example.com"}
if !nsSetsEqual(a, b) {
t.Error("same set, different order should be equal")
}
if nsSetsEqual(a, []string{"ns1.example.com"}) {
t.Error("different cardinality should not be equal")
}
if nsSetsEqual(a, []string{"ns1.example.com", "ns9.example.com"}) {
t.Error("different members should not be equal")
}
}
func TestDetectSplitSuppression(t *testing.T) {
outcomes := []resolverOutcome{
{name: "system", kind: outcomeNXDomain},
{name: "1.1.1.1", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "8.8.8.8", kind: outcomeInconclusive},
}
kind, detail := detectSplit("evil.test", outcomes)
if kind != SplitSuppression {
t.Fatalf("system-dark/public-live should be suppression, got %v", kind)
}
if !strings.Contains(detail, "1.1.1.1") || !strings.Contains(detail, "suppression") {
t.Errorf("detail should name suppression, got %q", detail)
}
}
func TestDetectSplitHorizon(t *testing.T) {
outcomes := []resolverOutcome{
{name: "system", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "1.1.1.1", kind: outcomeNXDomain},
{name: "8.8.8.8", kind: outcomeNXDomain},
}
kind, detail := detectSplit("internal.test", outcomes)
if kind != SplitHorizon {
t.Fatalf("system-live/public-dark should be horizon, got %v", kind)
}
if !strings.Contains(detail, "split-horizon") {
t.Errorf("detail should name split-horizon, got %q", detail)
}
}
func TestDetectSplitNS(t *testing.T) {
outcomes := []resolverOutcome{
{name: "system", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "1.1.1.1", kind: outcomeLive, ns: []string{"ns9.y"}},
}
kind, detail := detectSplit("evil.test", outcomes)
if kind != SplitNS {
t.Fatalf("NS delegation split should be SplitNS, got %v", kind)
}
if !strings.Contains(detail, "NS delegation split") {
t.Errorf("detail should name NS split, got %q", detail)
}
}
func TestDetectSplitAgreement(t *testing.T) {
// Same NS everywhere, different A records (CDN) is not observable here
// by design: only state and NS sets vote.
agree := []resolverOutcome{
{name: "system", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "1.1.1.1", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "8.8.8.8", kind: outcomeInconclusive},
}
if kind, _ := detectSplit("ok.test", agree); kind != SplitNone {
t.Errorf("agreement should be SplitNone, got %v", kind)
}
thin := []resolverOutcome{
{name: "system", kind: outcomeLive, ns: []string{"ns1.x"}},
{name: "1.1.1.1", kind: outcomeInconclusive},
{name: "8.8.8.8", kind: outcomeInconclusive},
}
if kind, _ := detectSplit("ok.test", thin); kind != SplitNone {
t.Errorf("single conclusive vote should be SplitNone, got %v", kind)
}
}

5
internal/rdap/rdap.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Package rdap queries RDAP registration data via https://rdap.org/domain/.
// Mirrors bash rdap_query / get_registration_date / get_registrar.
package rdap

5
internal/rdap/rdap_test.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package rdap
import (

33
internal/report/report.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Package report renders human, JSON, scale, and verbose output.
// Mirrors bash render_human / render_json / render_scale / render_verbose,
// plus the restored Validation line (per user decision).
@ -32,14 +37,20 @@ type Data struct {
// Scale prints the scoring reference table (no lookups performed).
func Scale(version string) string {
return fmt.Sprintf(`isthislegit? [v%s] — Scoring Scale (max total: 150)
return fmt.Sprintf(`isthislegit? [v%s] — Scoring Scale (max total: 200)
Signals:
+-----------------------------------------------+--------+
| Signal | Points |
+-----------------------------------------------+--------+
| Suspect domain age < 30 days (CRITICAL) | +80 |
| Suspect domain age 30-89 days (WARNING) | +80 |
| Suspect < 30d (CRITICAL), stacked w/ signal | +80 |
| Suspect < 30d (CRITICAL), isolated | +40 |
| Suspect 30-89d (WARNING), stacked w/ signal | +40 |
| Suspect 30-89d (WARNING), isolated | +20 |
| Shared cert infrastructure (halves age tier) | x0.5 |
| Identical target/suspect (forced LEGITIMATE) | +0 |
| DNS suppression split (suspect) | +50 |
| DNS split-horizon/target-side (info) | +0 |
| Cert downgrade: target EV/OV vs suspect DV | +40 |
| Registrar mismatch | +30 |
| Same-class issuer difference (display only) | +0 |
@ -200,9 +211,25 @@ func Verbose(d Data) string {
writeRDAP(d.TargetDomain, d.TargetRDAP)
writeTLS(d.SuspectDomain, d.SuspectCert)
writeRDAP(d.SuspectDomain, d.SuspectRDAP)
writeDNS(&b, "Target", d.TargetDomain, d.Target.DNSTampered, d.Target.DNSDetail)
writeDNS(&b, "Suspect", d.SuspectDomain, d.Suspect.DNSTampered, d.Suspect.DNSDetail)
return b.String()
}
// writeDNS renders the multi-resolver consistency verdict for one domain.
func writeDNS(b *strings.Builder, label, domain string, tampered bool, detail string) {
fmt.Fprintf(b, "--- DNS consistency (%s):\n", domain)
if detail == "" {
fmt.Fprintf(b, " consistent across resolvers (%s)\n\n", label)
return
}
status := detail
if tampered {
status = "TAMPERED: " + detail
}
fmt.Fprintf(b, " %s\n\n", status)
}
func classOf(c *cert.Details) string {
if c == nil || c.Class == "" {
return "Unknown"

5
internal/score/date.go
View file

@ -1,3 +1,8 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package score
import (

184
internal/score/score.go
View file

@ -1,22 +1,33 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
// Package score implements the deterministic risk scoring logic.
// It mirrors the bash implementation exactly (spec AGENTS.md section 4.4
// as refined by the bash script: <30 and 30-89 both +80, downgrade only
// EV/OV -> DV for +40, registrar mismatch +30 case-insensitive).
// Age tiers (<30 CRITICAL, 30-89 WARNING) are contextual: full weight
// needs company (registrar mismatch or cert downgrade), shared certificate
// infrastructure halves the tier, and identical domains score zero.
// Downgrade (EV/OV -> DV) is +40, registrar mismatch +30 case-insensitive.
package score
import "fmt"
import "strings"
import "isthislegit/internal/dns"
// DomainData holds the collected triage fields for one domain.
type DomainData struct {
Domain string
Date string // YYYY-MM-DD or sentinel on failure
Registrar string // "Unknown" when unavailable
Issuer string // "Unknown" when unavailable
Class string // EV, OV, IV, DV, or Unknown
SANs string // comma-joined, or "Unknown"
AgeDays int
AgeKnown bool
Domain string
Date string // YYYY-MM-DD or sentinel on failure
Registrar string // "Unknown" when unavailable
Issuer string // "Unknown" when unavailable
Class string // EV, OV, IV, DV, or Unknown
SANs string // comma-joined, or "Unknown"
AgeDays int
AgeKnown bool
DNSTampered bool // suppression/NS split (scores on suspect)
DNSSplit dns.SplitKind // split direction (horizon never scores)
DNSDetail string // human-readable split description
}
// Result is the outcome of scoring a target/suspect pair.
@ -67,27 +78,46 @@ func VerifyDataQuality(target, suspect DomainData) error {
return nil
}
// Score applies the three signals and maps the total to a verdict.
// Score applies the signals and maps the total to a verdict.
//
// Age is contextual, not a binary cliff: identical domains force zero
// with findings attached; shared certificate infrastructure halves the
// tier; full tier needs company (registrar mismatch or cert downgrade),
// with isolated domains scoring the next tier down.
func Score(target, suspect DomainData) Result {
var r Result
// Age check: suspect created < 90 days => +80.
if suspect.AgeKnown {
switch {
case suspect.AgeDays < 30:
r.Score += 80
r.AgeFlag = " [CRITICAL: Domain created < 30 days ago]"
r.Findings = append(r.Findings, fmt.Sprintf("HIGH RISK: Suspect domain created recently (%s).", suspect.Date))
case suspect.AgeDays < 90:
r.Score += 80
r.AgeFlag = " [WARNING: Domain created < 90 days ago]"
r.Findings = append(r.Findings, fmt.Sprintf("HIGH RISK: Suspect domain created recently (%s).", suspect.Date))
if target.Domain != "" && strings.EqualFold(target.Domain, suspect.Domain) {
r.Findings = append(r.Findings, "INFO: Target and suspect are identical — a domain cannot impersonate itself.")
noteDNS(&r, target, "target")
if suspect.DNSDetail != target.DNSDetail {
noteDNS(&r, suspect, "suspect")
}
r.Verdict = Verdict(r.Score)
return r
}
// Cert validation downgrade: target EV/OV but suspect DV => +40.
// Same-class issuer differences are display-only (no points).
isDowngrade := (target.Class == "EV" || target.Class == "OV") && suspect.Class == "DV"
mismatch := registrarMismatch(target, suspect)
stacked := mismatch || isDowngrade
sharedCert := sansOverlap(target, suspect)
// Age check with stacking and shared-infrastructure discount.
if suspect.AgeKnown {
switch {
case suspect.AgeDays < 30:
r.AgeFlag = " [CRITICAL: Domain created < 30 days ago]"
r.Score += agePoints(80, stacked, sharedCert)
r.Findings = append(r.Findings, ageFinding(suspect.Date, 80, stacked, sharedCert))
case suspect.AgeDays < 90:
r.AgeFlag = " [WARNING: Domain created < 90 days ago]"
r.Score += agePoints(40, stacked, sharedCert)
r.Findings = append(r.Findings, ageFinding(suspect.Date, 40, stacked, sharedCert))
}
}
if isDowngrade {
r.Score += 40
r.Findings = append(r.Findings, fmt.Sprintf("DOWNGRADE: Target uses %s (%s) while Suspect uses DV automated cert (%s).", target.Class, target.Issuer, suspect.Issuer))
@ -97,17 +127,115 @@ func Score(target, suspect DomainData) Result {
}
// Registrar mismatch => +30 (skipped when either side is unknown).
if target.Registrar != "Unknown" && suspect.Registrar != "Unknown" && target.Registrar != "" && suspect.Registrar != "" {
if !strings.EqualFold(target.Registrar, suspect.Registrar) {
r.Score += 30
r.Findings = append(r.Findings, fmt.Sprintf("MISMATCH: Registrars do not align (%s vs %s).", target.Registrar, suspect.Registrar))
}
if mismatch {
r.Score += 30
r.Findings = append(r.Findings, fmt.Sprintf("MISMATCH: Registrars do not align (%s vs %s).", target.Registrar, suspect.Registrar))
}
// Resolution tampering => +50 on the suspect side for suppression and
// NS splits. Split-horizon shapes describe split-horizon or observer
// networks, never the suspect, so they stay display-only — as does
// anything on the target side.
if suspect.DNSTampered {
r.Score += 50
r.Findings = append(r.Findings, fmt.Sprintf("TAMPERING: Inconsistent DNS resolution for suspect (%s).", suspect.DNSDetail))
}
if suspect.DNSSplit == dns.SplitHorizon {
r.Findings = append(r.Findings, fmt.Sprintf("NOTE: Split-horizon DNS for suspect (%s); resolves locally only.", suspect.DNSDetail))
}
noteDNS(&r, target, "target")
r.Verdict = Verdict(r.Score)
return r
}
// noteDNS appends display-only DNS findings for one side: tampering notes
// observer-side suspicion, horizon notes split-horizon shape. No points.
func noteDNS(r *Result, d DomainData, role string) {
if d.DNSDetail == "" {
return
}
if d.DNSTampered {
r.Findings = append(r.Findings, fmt.Sprintf("NOTE: Inconsistent DNS resolution for %s (%s); observer-side network suspected.", role, d.DNSDetail))
return
}
if d.DNSSplit == dns.SplitHorizon {
r.Findings = append(r.Findings, fmt.Sprintf("NOTE: Split-horizon DNS for %s (%s); resolves locally only.", role, d.DNSDetail))
}
}
// registrarMismatch reports a case-insensitive registrar difference,
// skipped when either side is unknown.
func registrarMismatch(target, suspect DomainData) bool {
known := func(s string) bool { return s != "" && s != "Unknown" }
return known(target.Registrar) && known(suspect.Registrar) && !strings.EqualFold(target.Registrar, suspect.Registrar)
}
// agePoints resolves an age tier to points: the full tier needs company
// (stacked signals), otherwise the next tier down; shared certificate
// infrastructure halves whatever remains.
func agePoints(tier int, stacked, sharedCert bool) int {
points := tier
if !stacked {
points /= 2
}
if sharedCert {
points /= 2
}
return points
}
// ageFinding words the age finding by final points, with the reason the
// tier was reduced when it was.
func ageFinding(date string, tier int, stacked, sharedCert bool) string {
points := agePoints(tier, stacked, sharedCert)
level := "LOW RISK"
if points >= 80 {
level = "HIGH RISK"
}
if points >= 40 && points < 80 {
level = "ELEVATED RISK"
}
reason := ""
if sharedCert {
reason = " Shared certificate infrastructure with target."
}
if reason == "" && !stacked {
reason = " No corroborating registrar or certificate signals."
}
return fmt.Sprintf("%s: Suspect domain created recently (%s).%s", level, date, reason)
}
// sansOverlap reports shared certificate infrastructure: either domain
// appearing in the other's SAN set, exactly or via a parent wildcard.
// Unknown or empty SAN fields never match.
func sansOverlap(target, suspect DomainData) bool {
return sanCovers(suspect.SANs, target.Domain) || sanCovers(target.SANs, suspect.Domain)
}
// sanCovers reports whether a comma-joined SAN field covers domain.
func sanCovers(sansField, domain string) bool {
domain = strings.ToLower(strings.TrimSpace(domain))
if domain == "" {
return false
}
for _, san := range strings.Split(sansField, ",") {
san = strings.ToLower(strings.TrimSpace(san))
if san == "" || san == "unknown" {
continue
}
if san == domain {
return true
}
if parent, ok := strings.CutPrefix(san, "*."); ok && parent != "" {
if domain == parent || strings.HasSuffix(domain, "."+parent) {
return true
}
}
}
return false
}
// isIssuerNote reports a display-only issuer difference: distinct known
// issuers at comparable validation levels. Avoids false positives when both
// sides legitimately use different DV CAs.

163
internal/score/score_test.go
View file

@ -1,8 +1,16 @@
// Copyright (C) 2026 Mark Robillard Jr (MARKMENTAL)
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License v3. See LICENSE.
// SPDX-License-Identifier: GPL-3.0-only
package score
import (
"strings"
"testing"
"time"
"isthislegit/internal/dns"
)
func TestScorePhishing(t *testing.T) {
@ -32,6 +40,80 @@ func TestScoreLegitimate(t *testing.T) {
}
}
func TestScoreWarningTier(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "Let's Encrypt", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2026-07-25", Registrar: "Same Inc.", Issuer: "Let's Encrypt", Class: "DV", SANs: "b.com", AgeDays: 45, AgeKnown: true}
r := Score(target, suspect)
if r.Score != 20 {
t.Errorf("Score = %d, want 20 (isolated warning tier)", r.Score)
}
if got := Verdict(r.Score); got != "LIKELY UNRELATED / MISCONFIGURED" {
t.Errorf("Verdict = %q", got)
}
if r.AgeFlag == "" {
t.Error("expected AgeFlag for 30-89d domain")
}
found := false
for _, f := range r.Findings {
if strings.Contains(f, "LOW RISK") {
found = true
}
if strings.Contains(f, "HIGH RISK") {
t.Errorf("isolated warning tier must not emit HIGH RISK, got %q", f)
}
}
if !found {
t.Errorf("expected LOW RISK finding, got %v", r.Findings)
}
}
func TestScoreWarningTierStacked(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Registrar A", Issuer: "Let's Encrypt", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2026-07-25", Registrar: "Registrar B", Issuer: "Let's Encrypt", Class: "DV", SANs: "b.com", AgeDays: 45, AgeKnown: true}
r := Score(target, suspect)
if r.Score != 70 {
t.Errorf("Score = %d, want 70 (stacked warning 40 + registrar 30)", r.Score)
}
if got := Verdict(r.Score); got != "LIKELY PHISHING / IMPERSONATION ATTEMPT" {
t.Errorf("Verdict = %q", got)
}
}
func TestScoreIdenticalDomains(t *testing.T) {
a := DomainData{Domain: "same.com", Date: "2026-09-08", Registrar: "R", Issuer: "I", Class: "DV", SANs: "same.com", AgeDays: 1, AgeKnown: true}
r := Score(a, a)
if r.Score != 0 {
t.Errorf("Score = %d, want 0 (identical domains)", r.Score)
}
if got := Verdict(r.Score); got != "LIKELY LEGITIMATE" {
t.Errorf("Verdict = %q", got)
}
if len(r.Findings) != 1 || !strings.Contains(r.Findings[0], "INFO") {
t.Errorf("expected single INFO finding, got %v", r.Findings)
}
}
func TestScoreSharedCertDiscount(t *testing.T) {
target := DomainData{Domain: "corp.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "DigiCert Inc", Class: "OV", SANs: "corp.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "new-corp.com", Date: "2026-09-01", Registrar: "Same Inc.", Issuer: "DigiCert Inc", Class: "OV", SANs: "new-corp.com, corp.com", AgeDays: 8, AgeKnown: true}
r := Score(target, suspect)
if r.Score != 20 {
t.Errorf("Score = %d, want 20 (isolated critical 40 halved by shared cert)", r.Score)
}
}
func TestScoreCriticalUnstacked(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "Let's Encrypt", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2026-09-01", Registrar: "Same Inc.", Issuer: "Let's Encrypt", Class: "DV", SANs: "b.com", AgeDays: 8, AgeKnown: true}
r := Score(target, suspect)
if r.Score != 40 {
t.Errorf("Score = %d, want 40 (isolated critical)", r.Score)
}
if got := Verdict(r.Score); got != "SUSPICIOUS — MANUAL REVIEW RECOMMENDED" {
t.Errorf("Verdict = %q", got)
}
}
func TestScoreSameClassIssuerDiffNoPoints(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "Let's Encrypt", Class: "DV", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "ZeroSSL", Class: "DV", AgeDays: 8000, AgeKnown: true}
@ -44,6 +126,87 @@ func TestScoreSameClassIssuerDiffNoPoints(t *testing.T) {
}
}
func TestScoreTamperedSuspect(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "b.com", AgeDays: 8000, AgeKnown: true,
DNSTampered: true, DNSDetail: "resolution split on b.com: 1.1.1.1 report NXDOMAIN while system resolve live"}
r := Score(target, suspect)
if r.Score != 50 {
t.Errorf("Score = %d, want 50 (isolated tampering)", r.Score)
}
if got := Verdict(r.Score); got != "SUSPICIOUS — MANUAL REVIEW RECOMMENDED" {
t.Errorf("Verdict = %q", got)
}
found := false
for _, f := range r.Findings {
if strings.Contains(f, "TAMPERING") {
found = true
}
}
if !found {
t.Errorf("expected TAMPERING finding, got %v", r.Findings)
}
}
func TestScoreTamperedSuspectStacked(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Registrar A", Issuer: "DigiCert Inc", Class: "EV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2026-09-01", Registrar: "Registrar B", Issuer: "Let's Encrypt", Class: "DV", SANs: "b.com", AgeDays: 8, AgeKnown: true,
DNSTampered: true, DNSDetail: "NS delegation split on b.com"}
r := Score(target, suspect)
// Stacked critical 80 + downgrade 40 + registrar 30 + tampering 50.
if r.Score != 200 {
t.Errorf("Score = %d, want 200 (fully stacked)", r.Score)
}
if got := Verdict(r.Score); got != "LIKELY PHISHING / IMPERSONATION ATTEMPT" {
t.Errorf("Verdict = %q", got)
}
}
func TestScoreTamperedTargetNoteOnly(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true,
DNSTampered: true, DNSDetail: "NS delegation split on a.com"}
suspect := DomainData{Domain: "b.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "b.com", AgeDays: 8000, AgeKnown: true}
r := Score(target, suspect)
if r.Score != 0 {
t.Errorf("Score = %d, want 0 (target-side split is display-only)", r.Score)
}
if len(r.Findings) != 1 || !strings.Contains(r.Findings[0], "NOTE") {
t.Errorf("expected single NOTE finding, got %v", r.Findings)
}
}
func TestScoreHorizonNoteOnly(t *testing.T) {
target := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "a.com", AgeDays: 9000, AgeKnown: true}
suspect := DomainData{Domain: "b.com", Date: "2000-01-01", Registrar: "Same Inc.", Issuer: "CA", Class: "DV", SANs: "b.com", AgeDays: 8000, AgeKnown: true,
DNSSplit: dns.SplitHorizon, DNSDetail: "split-horizon pattern on b.com"}
r := Score(target, suspect)
if r.Score != 0 {
t.Errorf("Score = %d, want 0 (horizon never scores)", r.Score)
}
if len(r.Findings) != 1 || !strings.Contains(r.Findings[0], "split-horizon") {
t.Errorf("expected single split-horizon NOTE, got %v", r.Findings)
}
}
func TestScoreIdenticalWithDNSFindings(t *testing.T) {
a := DomainData{Domain: "same.com", Date: "2026-09-08", Registrar: "R", Issuer: "I", Class: "DV", SANs: "same.com", AgeDays: 1, AgeKnown: true,
DNSTampered: true, DNSSplit: dns.SplitSuppression, DNSDetail: "suppression pattern on same.com"}
r := Score(a, a)
if r.Score != 0 {
t.Errorf("Score = %d, want 0 (identical domains never score)", r.Score)
}
if got := Verdict(r.Score); got != "LIKELY LEGITIMATE" {
t.Errorf("Verdict = %q", got)
}
if len(r.Findings) != 2 {
t.Fatalf("expected INFO + single NOTE, got %v", r.Findings)
}
for _, f := range r.Findings {
if strings.Contains(f, "TAMPERING") {
t.Errorf("identical domains must not emit TAMPERING, got %q", f)
}
}
}
func TestVerifyDataQuality(t *testing.T) {
ok := DomainData{Domain: "a.com", Date: "2000-01-01", Registrar: "R", Issuer: "I", Class: "DV", AgeKnown: true}
if err := VerifyDataQuality(ok, ok); err != nil {