Optimize mail reinjection

- Mark reinjected mails so that Husk can shortcut the processing.
- Fix Cargo.toml to correctly include the patched version of
  sequoia-cert-store and sequoia-keystore.

src/daemon/mod.rs

@@ -18,6 +18,7 @@ use indymilter::{
     ContextActions,
 };
 
+use crate::types::defaults::HELO_REINJECT_ID;
 use crate::types::husk_context::HuskContext;
 use crate::config::{HuskConfig, HuskConfigContainer};
 use crate::mail;
@@ -83,9 +84,13 @@ impl Daemon {
     async fn handle_helo(_cx: &mut Context<HuskContext<'_>>, hostname: CString) -> Status {
         log::debug!("HELO: hostname: {hostname:?}");
 
-        // XXX: check for reinjection
-
-        Status::Continue
+        if hostname.to_str() == Ok(HELO_REINJECT_ID) {
+            // Reinjected mail detected - this mail is unencrypted because
+            // all recipients lack a valid certificate. Accept mail.
+            Status::Accept
+        } else {
+            Status::Continue
+        }
     }
 
     async fn handle_mail(cx: &mut Context<HuskContext<'_>>, config_container: HuskConfigContainer, args: Vec<CString>) -> Status {

src/mail.rs

@@ -87,7 +87,7 @@ pub async fn smtp_inject(from: String, to: &Vec<Recipient<'_>>, header: CHeader,
         rcpts.push(rcpt.try_into()?);
     }
 
-    let my_id = ClientId::Domain("husk.reinject".to_owned()); // TODO: add secret token?
+    let my_id = ClientId::Domain(defaults::HELO_REINJECT_ID.to_owned()); // TODO: add secret token?
     joinset.spawn(async move {
 
         // XXX

src/types/defaults.rs

@@ -11,6 +11,9 @@ pub const PID_FILE_LOCATION: &str = "/run/husk/pid";
 pub const FOOTER: &str = "---\nProcessed by Husk at {date}.\n";
 pub const FOOTER_RECIPIENTS: &str = "This mail was also send to {rcpts}.\n";
 
+/// This ID is used when reinjecting an unencrypted mail into the MTA.
+pub const HELO_REINJECT_ID: &str = "husk.reinject";
+
 /// Default logging configuration.
 pub const CONSOLE_LOGGING: &str = "
 [appenders.console]