2 files changed, 80 insertions, 3 deletions

diff --git a/modules/private/mail/filter-rewrite-from.py b/modules/private/mail/filter-rewrite-from.py
new file mode 100755
index 0000000..aad9c69
--- /dev/null
+++ b/modules/private/mail/filter-rewrite-from.py
@@ -0,0 +1,68 @@
+#! /usr/bin/env python3
+import sys
+
+sys.stdin.reconfigure(encoding='utf-8')
+sys.stdout.reconfigure(encoding='utf-8')
+stdin = sys.stdin
+stdout = sys.stdout
+
+mailaddr = sys.argv[1]
+inheader = {}
+
+# Change to actual file for logging
+logfile = open("/dev/null", "a")
+
+def log(l, i):
+    logfile.write("{} {}\n".format(i, l))
+    logfile.flush()
+
+def send(l):
+    log(l, ">")
+    stdout.write("{}\n".format(l))
+    stdout.flush()
+
+def token_and_sid(version, sid, token):
+    if version < "0.5":
+        return "{}|{}".format(token, sid)
+    else:
+        return "{}|{}".format(sid, token)
+
+log("started", "l")
+while True:
+    line = stdin.readline().strip()
+    log(line, "<")
+    if not line:
+        log("finished", "l")
+        break
+    splitted = line.split("|")
+    if line == "config|ready":
+        log("in config ready", "l")
+        send("register|filter|smtp-in|mail-from")
+        send("register|filter|smtp-in|data-line")
+        send("register|ready")
+    if splitted[0] != "filter":
+        continue
+    if len(splitted) < 7:
+        send("invalid filter command: expected >6 fields!")
+        sys.exit(1)
+    version = splitted[1]
+    action = splitted[4]
+    sid = splitted[5]
+    token = splitted[6]
+    token_sid = token_and_sid(version, sid, token)
+    rest = "|".join(splitted[7:])
+    if action == "mail-from":
+        inheader[sid] = True
+        send("filter-result|{}|rewrite|<{}>".format(token_sid, mailaddr))
+        continue
+    if action == "data-line":
+        if rest == "" and inheader.get(sid, False):
+            inheader[sid] = False
+        if rest == "." and not inheader.get(sid):
+            del(inheader[sid])
+        if inheader.get(sid, False) and rest.upper().startswith("FROM:"):
+            send("filter-dataline|{}|From: {}".format(token_sid, mailaddr))
+        else:
+            send("filter-dataline|{}|{}".format(token_sid, rest))
+        continue
+    send("filter-result|{}|proceed".format(token_sid))
diff --git a/modules/private/mail/opensmtpd.nix b/modules/private/mail/opensmtpd.nix
index e4a6140..a7be066 100644
--- a/modules/private/mail/opensmtpd.nix
+++ b/modules/private/mail/opensmtpd.nix
@@ -15,12 +15,21 @@
     users.users.smtpd.extraGroups = [ "keys" ];
     services.opensmtpd = {
       enable = true;
-      serverConfiguration = ''
+      serverConfiguration = let
+        filter-rewrite-from = pkgs.runCommand "filter-rewrite-from.py" {
+          buildInputs = [ pkgs.python3 ];
+        } ''
+          cp ${./filter-rewrite-from.py} $out
+          patchShebangs $out
+        '';
+      in ''
         table creds \
           "${config.secrets.fullPaths."opensmtpd/creds"}"
-        # FIXME: filtering requires 6.6
+        # FIXME: filtering requires 6.6, uncomment following lines when
+        # upgrading
         # filter "fixfrom" \
-        #   proc-exec "${pkgs.procmail}/bin/formail -i 'From: ${name}@immae.eu'"
+        #   proc-exec "${filter-rewrite-from} ${name}@immae.eu"
+        # listen on socket filter "fixfrom"
         action "relay-rewrite-from" relay \
           helo ${config.hostEnv.fqdn} \
           host smtp+tls://eldiron@eldiron.immae.eu:587 \