From de4607f9460ae00bd92f5317ed0a289511bc23b2 Mon Sep 17 00:00:00 2001
From: equa <equaa@protonmail.com>
Date: Tue, 14 Mar 2023 17:42:05 +0000
Subject: [PATCH] init

---
 README.md     | 47 ++++++++++++++++++++++++++++++++++++++++++
 make_lists.sh | 15 ++++++++++++++
 procmailrc    | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 README.md
 create mode 100755 make_lists.sh
 create mode 100644 procmailrc

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..04d0ea5
--- /dev/null
+++ b/README.md
@@ -0,0 +1,47 @@
+# town mailing list manager
+
+our little bespoke town engine. it runs on a janky procmail script
+
+
+## setup
+
+our system is very particular to running on public unix systems and probably
+wouldn't be advisable for anything with external mail.
+
+we have our local mail set up so that it's impossible to spoof the
+envelope sender of an email with `local_login_sender_maps` in postfix;
+the list handles this to make the emails look pretty and to evade spoofing
+
+the software works on the assumption that everything lives in the home dir
+of a user named `list`.
+our list account needs two directories, `lists/` and `archive/`.
+our scripts can autopopulate everything here, but you can also do manual
+configuration in `lists/` to change access control to certain mailing lists.
+
+copy procailrc to `~/.procmailrc` and set up `~/.forward` to filter all mail
+through it:
+
+```
+|/usr/bin/procmail
+```
+
+if you want to have any special read-only mailing lists, you can populate
+`lists/LISTNAME.senders` with a list of allowed senders, one on each line
+
+a user can subscribe by naming the lists they want to subscribe to in a
+`.townlists` file in their home directory
+rather than checking these lists every post, we populate some internal
+subscription lists with `make_lists.sh`, which should run on a cron job.
+
+## assumptions
+- mailing list names are `[a-z0-9_]{1,16}`
+  - we check this in the .townlists files and in sending
+- everything lives in our home directory
+  - `lists/` and `archive/` directories exist
+- usernames don't contain special characters
+  - i don't actually know which ones would be an issue
+    but town doesn't usually allow anything too crazy anyway
+
+### subscriptions
+- everyone we care about lives in /home and their usernames correspond to the directories
+- list subscriptions are stored per-line in `.townlists`
diff --git a/make_lists.sh b/make_lists.sh
new file mode 100755
index 0000000..974970e
--- /dev/null
+++ b/make_lists.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+rm -- "${HOME}/lists/"*.users.new
+
+for listfile in /home/*/.townlists; do
+	user="$(basename "$(dirname "$listfile")")"
+	for x in $(grep '^[a-z0-9_]\{1,16\}$' "$listfile"); do
+		echo "$user" >> "${HOME}/lists/${x}.users.new"
+	done
+done
+
+rm -- "${HOME}/lists"/*.users
+for i in "${HOME}/lists"/*.users.new; do
+	mv -- "$i" "$(dirname "$i")"/"$(basename "$i" .new)"
+done
diff --git a/procmailrc b/procmailrc
new file mode 100644
index 0000000..c3e53a0
--- /dev/null
+++ b/procmailrc
@@ -0,0 +1,56 @@
+# mailing list protocol!
+# depends on a bunch of files in $HOME/lists --
+# a "listname.users" containing all of the users
+# and (optionally) a "listname.senders" if you want to restrict that
+SHELL=/bin/sh
+SENDMAIL=/usr/sbin/sendmail
+LINEBUF=10000000
+
+:0
+* ^To:.*list\+\/[a-z0-9_]+@tilde\.town
+LIST=| echo "$MATCH" | sed 's/@.*//' | sed 's/\(.\{16\}\).*/\1/' | tr '[:upper:]' '[:lower:]'
+
+:0A
+{
+	:0A
+	* ? [ -e ${HOME}/lists/${LIST}.users ]
+	RECIPIENTS=| cat ${HOME}/lists/${LIST}.users | tr '\n' ' '
+
+	:0E
+	{ RECIPIENTS="" }
+}
+
+# Extract envelope sender. Email addresses are actually very complex
+# but we're on tilde.town so our email addresses aren't going to have spaces
+:0A
+* ^From \/[^ ]*
+ENV_SENDER=|echo "$MATCH" | sed "s/ .*//"
+
+:0A
+ENV_USER=|echo "$ENV_SENDER" | sed "s/@.*//"
+
+:0A
+{
+	# If we have a restricted list of senders we should abort if it's not in there
+	:0A
+	* ? [ -e "${HOME}/lists/${LIST}.senders" ]
+	{
+		:0A
+		* !? grep -F "${ENV_USER}" "${HOME}/lists/${LIST}.senders"
+		# hack to quit procmailrc immediately (WHY)
+		{ EXITCODE=77 HOST= }
+	}
+}
+
+:0Af
+| formail -a "X-Loop: list+${LIST}@tilde.town" -I "Reply-To: ${LIST} <list+${LIST}@tilde.town>" -I "From: ${ENV_SENDER}"
+
+:0A
+{
+	UMASK=003
+	:0c:
+	archive/${LIST}
+}
+
+:0A
+! ${RECIPIENTS}