Wire-format JSON tag consistency fix, and the first real plugin

Writing PLUGINS.md as an authoritative external spec surfaced a real,
pre-existing bug: store.Summary/Entry/EntryTag/WSMessage, rules.Rule,
scope.Rule, and clientcert.Cert had no JSON struct tags at all, so Go's
default marshaling serialized them PascalCase ("ID", "StartedAt")
while the rest of the protocol (EntryDetail's own fields, every
Request/Response wrapper field) uses snake_case. Confirmed live against
a real daemon before touching anything: a raw socket "list" request
came back with "ID"/"StartedAt"/"StatusCode", exactly the mismatch
suspected. Nothing outside this repo's own Go code consumes this wire
format yet, so this was a free, purely additive fix rather than
something to work around - every affected struct now tags snake_case
consistently.

plugins/authcheck is the first real plugin: an Autorize-style
authorization checker. For every proxied request carrying an
Authorization or Cookie header, resends it with that header stripped
and compares status classes - a resend that still succeeds where the
original did too is a likely missing-function-level-access-control
bug, tagged authcheck:bypass with structured detail. Deliberately
speaks the wire protocol directly (its own local request/response/
summary/entryDetail structs mirroring the real ones field-for-field,
not imported from internal/ipc) rather than taking the shortcut a Go
plugin could - proof the documented protocol is actually sufficient on
its own, since that's all a non-Go plugin author has to work with.

Verified live end to end: a real daemon, a real Python origin with one
endpoint that looks like it enforces auth but doesn't (vulnerable by
design) and one that actually does (the control case) - the broken
endpoint was correctly tagged, the secure one correctly left alone, no
false positive, confirmed both via the stored tag data directly and
visually in the TUI (tmux, real keystrokes): the Tags column badge, T's
tag list, and the tag detail view's JSON-colorized data (ANSI-verified,
not eyeballed) all showing the plugin's actual findings.

1 files changed, 8 insertions, 0 deletions

diff --git a/PLUGINS.md b/PLUGINS.md
index bb46461..630f211 100644
--- a/PLUGINS.md
+++ b/PLUGINS.md
@@ -11,6 +11,14 @@ Go), and means a plugin can be developed and tested against the exact
 same socket the TUI is already using, with `mitmux` itself open in
 another terminal watching what happens in real time.
 
+`plugins/authcheck` is a real, working reference implementation - an
+Autorize-style authorization checker (resends a captured request with
+its auth header stripped, tags the entry if the response still
+succeeds) - written to only ever exercise what's documented on this
+page, not any of mitmux's own internal Go packages, specifically so it
+proves this protocol is sufficient on its own. Worth reading alongside
+this document, or just copying as a starting point.
+
 ## Connecting
 
 The socket path is the same one `mitmux -socket` and `mitmuxd -socket`