Merge branch 'malte/mail_splitting' into 'main'

Mail splitting

See merge request husk-project/husk-milter!9

Cargo.toml

@@ -14,17 +14,18 @@ rust-version = "1.85"
 aho-corasick = "1.1.4"
 anyhow = "1.0.100"
 bytes = "1.11.1"
+chrono = "0.4.45"
 clap = { version = "4", features = ["derive"] }
 fastrand = "2.4.1"
 indymilter = "0.3.0"
+lettre = "0.11.22"
 log = "0.4.30"
 log4rs = "1.3.0"
 sequoia-cert-store = "0.7.3"
 sequoia-directories = "0.1.0"
-#sequoia-keystore = "0.7.2"
-sequoia-keystore = { git = "https://gitlab.com/sequoia-pgp/sequoia-keystore", branch = "malte/softkey-refresh" }
+sequoia-keystore = "0.7.2"
 sequoia-net = "0.30.1"
-sequoia-openpgp = "2.3.0"
+sequoia-openpgp = "2.4.0"
 sequoia-wot = "0.15.0"
 serde = "1.0.228"
 serde_derive = "1.0.228"
@@ -41,3 +42,11 @@ daemonix = "0.1.0"
 anyhow = "1.0.100"
 clap = { version = "4", features = ["derive"] }
 clap_complete = "4"
+
+[profile.release]
+lto = true
+codegen-units = 1
+
+[patch.crates-io]
+sequoia-cert-store = { git = "https://gitlab.com/sequoia-pgp/sequoia-cert-store", branch = "malte/assert_base_dir" }
+sequoia-keystore = { git = "https://gitlab.com/sequoia-pgp/sequoia-keystore", branch = "malte/softkey-refresh" }

e2e-tests/common.sh

@@ -12,13 +12,14 @@ delete_unix_user() { # name
 
 # send a mail and wait for delivery
 send_test_mail() { # email_address
+  echo "send test mail to $1" >&2
   USER=$(echo $1 | cut -f 1 -d '@')
   # create an empty mailbox file
   touch /var/mail/$USER
   chown $USER:mail /var/mail/$USER
   chmod 600 /var/mail/$USER
 
-  echo -e "Subject: testmail\n\ntest mail" | sendmail $1
+  echo -e "To: $1\nSubject: testmail\n\ntest mail" | sendmail -t
   inotifywait -qq -t 3 -e close_write /var/mail/$USER
 }
 
@@ -27,10 +28,10 @@ test_header() { # text
   echo "##############################################"
   echo $1
   echo "Workdir: $WORKDIR"
-  echo "##############################################"
+  echo "----------------------------------------------"
 }
 
-# Generate a key outside the cert store. The key will not be
+# Generate a key outside the key store. The key will not be
 # authenticated.
 gen_key() { # email
   FILE=$(echo $1 | cut -f 1 -d '@')
@@ -41,31 +42,60 @@ gen_key() { # email
   echo $FPR
 }
 
-expect_mail() { # unix_user mode
+# Generate a key outside the key store. The key will not be
+# authenticated. Import the certificate of the key.
+gen_cert() { # email
+  FILE=$(echo $1 | cut -f 1 -d '@')
+  FPR=$(sq key generate --home none --shared-key --without-password \
+    --email $1 \
+    --output $WORKDIR/${FILE}_sk.pgp \
+    --rev-cert $WORKDIR/${FILE}.rev |& grep "Fingerprint:" | cut -d ':' -f 2)
+  sq cert import $WORKDIR/${FILE}_sk.pgp > /dev/null 2>&1
+  echo $FPR
+}
+
+authenticate() { # Fingerprint
+  sq pki link add --cert $1 --all > /dev/null 2>&1
+}
+
+expect_mail() { # unix_user mode [signature_fpr]
   if [ -f /var/mail/$1 ] ; then
     case $2 in
       encrypted)
         if grep -q "BEGIN PGP MESSAGE" /var/mail/$1 ; then
+          echo "GOOD: found expected encrypted mail" >&2
           R=0
+          if [ "$3" != "" ] ; then
+            FOUND_FPR=$(sq packet dump /var/mail/$1 | grep "Issuer Fingerprint:" | cut -d ':' -f 2 | tr -d ' ')
+
+            if [ "$3" != "$FOUND_FPR" ] ; then
+              echo "BAD: Found wrong signature '$FOUND_FPR' - expected '$3'" >&2
+              R=1
+            else
+              echo "GOOD: found right signature" >&2
+            fi
+          fi
         else
-          echo "expected encrypted mail for $1" >&2
+          echo "BAD: encryped mail expected but not found" >&2
           R=1
         fi
         ;;
       unencrypted)
         if grep -q "BEGIN PGP MESSAGE" /var/mail/$1 ; then
-          echo "expected unencrypted mail for $1" >&2
+          echo "BAD: expected unencrypted mail for $1" >&2
           R=1
         else
+          echo "GOOD: found expected unencrypted mail" >&2
           R=0
         fi
         ;;
       delivered)
+        echo "GOOD: mail delivery worked" >&2
         R=0
         ;;
     esac
   else
-    echo "no mail for $1" >&2
+    echo "BAD: no mail for $1" >&2
     R=1
   fi
   echo $R

e2e-tests/tests/40_introducer_create.sh

@@ -14,12 +14,11 @@ $HUSK_BIN introducer list --config config/config.toml
 create_unix_user fred
 FRED_FPR=$(sq key generate --shared-key --without-password --name "Fred" --email "fred@example.org" 2>&1 | grep "Fingerprint:" | cut -d ':' -f 2)
 sleep 1
-sq pki link retract --cert $FRED_FPR --all
+sq pki link retract --cert $FRED_FPR --all > /dev/null 2>&1
 
-sq pki vouch add --certifier $ELLEN_FPR --cert $FRED_FPR --email "fred@example.org"
+sq pki vouch add --certifier $ELLEN_FPR --cert $FRED_FPR --email "fred@example.org" > /dev/null 2>&1
 
 send_test_mail fred@example.org
-
 RESULT_CODE=$(expect_mail fred encrypted)
 
 if [ "$RESULT_CODE" == "1" ] ; then

e2e-tests/tests/51_add_locals.sh

@@ -5,7 +5,7 @@
 
 test_header "Add locals"
 
-sq key generate --shared-key --without-password --email 'hubert@example.com' --output /tmp/hubert.pgp --rev-cert /tmp/hubert_rev.pgp
+sq key generate --shared-key --without-password --email 'hubert@example.com' --output /tmp/hubert.pgp --rev-cert /tmp/hubert_rev.pgp > /dev/null 2>&1
 
 cd $HUSK_DIR
 
@@ -16,47 +16,27 @@ if ! $HUSK_BIN locals list --config config/config.toml | grep -q "hubert@example
 fi
 
 # send a mail, husk should encrypt it
-echo "send mail to hubert@example.com"
 create_unix_user hubert
 send_test_mail hubert@example.com
 
-if [ -f /var/mail/hubert ] ; then
-  if grep -q "BEGIN PGP MESSAGE" /var/mail/hubert ; then
-    RESULT_CODE=0
-  else
-    echo "no encryption detected"
-    delete_unix_user hubert
-    exit 1
-  fi
-  # remove mail
-  rm /var/mail/hubert
-else
-  echo "no mail detected"
+R=$(expect_mail hubert encrypted)
+if [ $R != 0 ] ; then
   delete_unix_user hubert
   exit 1
 fi
 
 sleep 1
-# remove hubert as local
+
+echo "removing hubert as local"
 HUBERT_FPR=$(sq cert list --cert-email hubert@example.com 2>/dev/null | head -n 1 | cut -d ' ' -f 3)
 $HUSK_BIN locals remove --cert $HUBERT_FPR --config config/config.toml
 
-echo "send mail to hubert@example.com"
+rm /var/mail/hubert
 send_test_mail hubert@example.com
 
-if [ -f /var/mail/hubert ] ; then
-  if grep -q "BEGIN PGP MESSAGE" /var/mail/hubert ; then
-    echo "encryption detected where there should be none"
-    RESULT_CODE=1
-  else
-    RESULT_CODE=0
-  fi
-else
-  echo "no mail detected"
-  RESULT_CODE=1
-fi
+R=$(expect_mail hubert unencrypted)
 
 delete_unix_user hubert
 
-exit $RESULT_CODE
+exit $R
 

e2e-tests/tests/60_signing.sh

@@ -5,39 +5,28 @@
 
 test_header "Signing"
 
-# sq key generate --shared-key --without-password --email 'signing@example.com' --output /tmp/signing.pgp --rev-cert /tmp/signing.rev
-
-SIGN_FPR=$(sq key generate --own-key --without-password --name "Signing Key" 2>&1 | grep "Fingerprint:" | cut -d ':' -f 2)
+SIGN_FPR_GEN=$(sq key generate --own-key --without-password --name "Signing Key" 2>&1 | grep "Fingerprint:" | cut -d ':' -f 2 | tr -d ' ')
 
 cd $HUSK_DIR
 
-$HUSK_BIN --config config/config.toml signkey set --cert $SIGN_FPR
+$HUSK_BIN --config config/config.toml signkey set --cert $SIGN_FPR_GEN
 SIGN_FPR=$($HUSK_BIN --config config/config.toml signkey show | cut -d ':' -f 2 | tr -d ' ')
 echo "found signing key $SIGN_FPR"
 
+if [ "$SIGN_FPR" != "$SIGN_FPR_GEN"  ] ; then
+  echo "setting new siging key failed, found $SIGN_FPR expected $SIGN_FPR_GEN"
+  exit 1
+fi
+
 create_unix_user juliette
 JULIETTE_FPR=$(sq key generate --own-key --without-password --name "Juliette" --email "juliette@example.com" 2>&1 | grep "Fingerprint:" | cut -d ':' -f 2)
-sq pki vouch add --certifier-userid "CA" --cert $JULIETTE_FPR --all > /dev/null 2>&1
+# sq pki vouch add --certifier-userid "CA" --cert $JULIETTE_FPR --all > /dev/null 2>&1
 
 # send a mail, husk should encrypt it
-echo "send mail to juliette@example.com"
 send_test_mail juliette@example.com
 
-if [ -f /var/mail/juliette ] ; then
-  if grep -q "BEGIN PGP MESSAGE" /var/mail/juliette ; then
-
-    FOUND_FPR=$(sq packet dump /var/mail/juliette | grep "Issuer Fingerprint:" | cut -d ':' -f 2 | tr -d ' ')
-
-    if [ "$SIGN_FPR" != "$FOUND_FPR" ] ; then
-      echo "Found wrong fingerprint '$FOUND_FPR' - expected '$SIGN_FPR'"
-      exit 1
-    fi
-  else
-    echo "no encryption detected"
-    exit 1
-  fi
-else
-  echo "no mail detected"
+R=$(expect_mail juliette encrypted $SIGN_FPR)
+if [ $R != 0 ] ; then
   exit 1
 fi
 
@@ -50,23 +39,6 @@ echo "new signing key $SIGN_FPR"
 # remove old mail
 rm /var/mail/juliette
 
-echo "send mail to juliette@example.com"
 send_test_mail juliette@example.com
 
-if [ -f /var/mail/juliette ] ; then
-  if grep -q "BEGIN PGP MESSAGE" /var/mail/juliette ; then
-
-    FOUND_FPR=$(sq packet dump /var/mail/juliette | grep "Issuer Fingerprint:" | cut -d ':' -f 2 | tr -d ' ')
-
-    if [ "$SIGN_FPR" != "$FOUND_FPR" ] ; then
-      echo "Found wrong fingerprint '$FOUND_FPR' - expected '$SIGN_FPR'"
-      exit 1
-    fi
-  else
-    echo "no encryption detected"
-    exit 1
-  fi
-else
-  echo "no mail detected"
-  exit 1
-fi
+exit $(expect_mail juliette encrypted $SIGN_FPR)

e2e-tests/tests/70_mail_split.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/bash
+
+# source some functions
+. common.sh
+
+test_header "Mail split"
+
+create_unix_user karl
+KARL_FPR=$(gen_cert karl@example.com)
+authenticate $KARL_FPR
+
+create_unix_user laura
+
+echo -e "To: karl@example.com, Laura <laura@example.com>\nSubject: Testmail\n\nTestmail." | sendmail -t
+sleep 1
+
+R=1
+if [ $(expect_mail karl encrypted) == 0 ] ; then
+  if [ $(expect_mail laura unencrypted) == 0 ] ; then
+    R=0
+  fi
+fi
+
+exit $R

src/common/crypto.rs

@@ -23,7 +23,6 @@ use sequoia_openpgp::parse::{PacketParser, PacketParserResult, Parse};
 use sequoia_openpgp::policy::StandardPolicy;
 use sequoia_openpgp::serialize::stream::{Message, Armorer, Encryptor, Signer, LiteralWriter};
 use sequoia_openpgp::{Fingerprint, Cert, Packet};
-use sequoia_openpgp::cert::raw::RawCertParser;
 use sequoia_openpgp::types::SignatureType;
 use sequoia_cert_store::{Store, CertStore, LazyCert, StoreUpdate};
 use sequoia_cert_store::store::MergePublicCollectStats;
@@ -45,35 +44,15 @@ const HUSK_SIG_NOTATION: &str = "signing_key@husk-project.org";
 /// Returns the local trust root from the cert_store. If the trust root
 /// cannot be found, it returns an error.
 pub fn get_local_trust_root(cert_store: &CertStore) -> anyhow::Result<Cert> {
-
-    let root = cert_store.certd()
-        .and_then(|certd| {
-            match certd.certd().get(sequoia_cert_store::store::openpgp_cert_d::TRUST_ROOT) {
-                Ok(Some((_tag, bytes))) => Some(bytes),
-                Ok(None) => None,
-                Err(_) => None
-            }
-        })
-        .and_then(|bytes| {
-            match RawCertParser::from_bytes(&bytes[..]) {
-                Ok(mut parser) => {
-                    match parser.next() {
-                        Some(Ok(cert)) => {
-                            Cert::from_bytes(cert.as_bytes()).ok()
-                        },
-                        Some(Err(_))
-                        | None => None
-                    }
-                },
-                Err(_) => None,
-            }
-        });
-
-    match root {
-        Some(r) => Ok(r),
-        None => Err(HuskError::NoLocalTrustRoot.into())
+    if let Some((root, created)) = cert_store.certd().and_then(|certd| {
+        certd.trust_root().ok() }) {
+        if created {
+            log::info!("Local trust root not found - created one");
+        }
+        Ok(root.to_cert()?.clone())
+    } else {
+        Err(HuskError::NoLocalTrustRoot.into())
     }
-
 }
 
 /// Returns all local certificates with an authenticated binding to user id 'email'.
@@ -255,7 +234,7 @@ pub async fn get_certificates<'hc>(context: &HuskContext<'hc>, email: &str)
 
     for introducer in &context.introducers {
         log::debug!("consider introducer {:?}",
-            introducer.cert.userids().map(|u| u.userid()).collect::<Vec<_>>());
+            introducer.cert.self_signed_userids().map(|u| u.userid()).collect::<Vec<_>>());
         if introducer.can_introduce(format!("<{}>", email).as_str()) {
             log::debug!("  introducer regex matches!");
             match lookup_certificates(context, email).await {

src/daemon/mod.rs

@@ -1,7 +1,7 @@
 //! the actual daemon
 
 use anyhow;
-use bytes::Bytes;
+use bytes::{Bytes, BytesMut};
 use std::ffi::CString;
 use tokio::signal;
 use tokio::net::TcpListener;
@@ -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;
@@ -39,8 +40,8 @@ impl Daemon {
         let callbacks = Callbacks::new()
             .on_negotiate(|cx, actions, opts| Box::pin(Self::handle_negotiate(cx, actions, opts)))
             .on_connect(|cx, hostname, socket_info| Box::pin(Self::handle_connect(cx, hostname, socket_info)))
-            .on_helo(move |cx, hostname| Box::pin(Self::handle_helo(cx, config_container.clone(), hostname)))
-            .on_mail(|cx, args| Box::pin(Self::handle_mail(cx, args)))
+            .on_helo(|cx, hostname| Box::pin(Self::handle_helo(cx, hostname)))
+            .on_mail(move |cx, args| Box::pin(Self::handle_mail(cx, config_container.clone(), args)))
             .on_rcpt(|cx, args| Box::pin(Self::handle_rcpt(cx, args)))
             .on_data(|cx| Box::pin(Self::handle_data(cx)))
             .on_header(|cx, name, value| Box::pin(Self::handle_header(cx, name, value)))
@@ -80,26 +81,19 @@ impl Daemon {
         Status::Continue
     }
 
-    async fn handle_helo(cx: &mut Context<HuskContext<'_>>, config_container: HuskConfigContainer, hostname: CString) -> Status {
+    async fn handle_helo(_cx: &mut Context<HuskContext<'_>>, hostname: CString) -> Status {
         log::debug!("HELO: hostname: {hostname:?}");
 
-        let config: HuskConfig = config_container.into();
-
-        // setup Context
-        match HuskContext::new(&config) {
-            Ok(context) => {
-                log::debug!("found introducers: {:?}", context.introducers);
-                cx.data = Some(context);
-                Status::Continue
-            },
-            Err(e) => {
-                log::error!("{}", e);
-                Status::Tempfail
-            }
+        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<'_>>, args: Vec<CString>) -> Status {
+    async fn handle_mail(cx: &mut Context<HuskContext<'_>>, config_container: HuskConfigContainer, args: Vec<CString>) -> Status {
         log::debug!("MAIL: {args:?}");
 
         let mut sender: Option<String> = None;
@@ -117,7 +111,20 @@ impl Daemon {
             context.set_sender(sender.unwrap());
             Status::Continue
         } else {
-            Status::Tempfail
+            let config: HuskConfig = config_container.into();
+
+            // setup Context
+            match HuskContext::new(&config) {
+                Ok(mut context) => {
+                    context.set_sender(sender.unwrap());
+                    cx.data = Some(context);
+                    Status::Continue
+                },
+                Err(e) => {
+                    log::error!("{}", e);
+                    Status::Tempfail
+                }
+            }
         }
     }
 
@@ -202,58 +209,149 @@ impl Daemon {
                 return Status::Accept;
             }
 
-            // possible protection
-            // none -> accept
-            // partial -> accept (later: split)
-            // full -> encrypt
+            let from = match context.mail.sender.clone() {
+                Some(f) => f,
+                None => {
+                    log::error!("No sender given");
+                    return Status::Tempfail;
+                }
+            };
 
-            let protection = ProtectionPossibility::from(&context.mail);
+            match ProtectionPossibility::from(&context.mail) {
+                ProtectionPossibility::Full => {
+                    log::debug!("completely encryptable");
+                    let mut body: BytesMut = body.into();
+                    body.extend_from_slice(mail::generate_footer(&vec![]).as_bytes());
+                    let inner_mail = MailContext::generate_inner_mail(&context.mail.header, body.into());
 
-            if protection == ProtectionPossibility::Full {
+                    // if an error occures the body is not exchanged
+                    match crypto::encrypt(context, inner_mail.to_string().as_bytes(), &context.mail.recipients) {
+                        Ok(encrypted) => {
+                            // replace the body of the mail with an encrypted,
+                            // mime encoded version.
+                            let outer_mail = MailContext::generate_outer_mail(encrypted);
+                            if cx.actions.replace_body(
+                                    outer_mail
+                                    .body_to_string()
+                                    .as_bytes()).await.is_err() {
+                                log::error!("Cannot exchange body");
+                                return Status::Continue;
+                            }
 
-                let inner_mail = context.mail.generate_inner_mail(body);
-
-                // if an error occures the body is not exchanged
-                match crypto::encrypt(context, inner_mail.to_string().as_bytes(), &context.mail.recipients) {
-                    Ok(encrypted) => {
-                        // replace the body of the mail with an encrypted,
-                        // mime encoded version.
-                        let outer_mail = MailContext::generate_outer_mail(encrypted);
-                        if cx.actions.replace_body(
-                                outer_mail
-                                .body_to_string()
-                                .as_bytes()).await.is_err() {
-                            log::error!("Cannot exchange body");
-                            return Status::Continue;
-                        }
-
-                        // adjust headers
-                        // This is mostly Content-Type related.
-                        for line in outer_mail.get_header().iter_lines() {
-                            // XXX: handle errors
-                            if let Ok(key) = line.key_as_cstring() {
-                                if let Ok(value) = line.value_as_cstring() {
-                                    let _ = cx.actions.change_header(
-                                        key, 1,
-                                        Some(value)
-                                    ).await;
+                            // adjust headers
+                            // This is mostly Content-Type related.
+                            for line in outer_mail.get_header().iter_lines() {
+                                // XXX: handle errors
+                                if let Ok(key) = line.key_as_cstring() {
+                                    if let Ok(value) = line.value_as_cstring() {
+                                        let _ = cx.actions.change_header(
+                                            key, 1,
+                                            Some(value)
+                                        ).await;
+                                    }
                                 }
                             }
+                            // Change the subject
+                            let _ = cx.actions.change_header(
+                                "Subject",
+                                1,
+                                Some(context.subject_replacement.clone())).await;
+                        },
+                        Err(e) => {
+                            log::error!("{}", e);
                         }
-                        // Change the subject
-                        let _ = cx.actions.change_header(
-                            "Subject",
-                            1,
-                            Some(context.subject_replacement.clone())).await;
-                    },
-                    Err(e) => {
-                        log::error!("{}", e);
                     }
+                },
+                ProtectionPossibility::Partial(encryptable, unencryptable) => {
+                    log::debug!("partially encryptable");
+                    // Generate a new mail for the unencryptable recipients.
+
+                    let mut unencryted_body: BytesMut = body.clone().into();
+                    unencryted_body.extend_from_slice(mail::generate_footer(&encryptable).as_bytes());
+                    let header = context.mail.header.without_recipients(&encryptable);
+                    if mail::smtp_inject(
+                        from,
+                        &unencryptable,
+                        header,
+                        &unencryted_body.into()).await.is_err() {
+                            // smtp_inject() already logged the error.
+                            return Status::Tempfail;
+                    }
+
+                    // Encrypt for remaining recipients.
+                    let mut encrypted_body: BytesMut = body.into();
+                    encrypted_body.extend_from_slice(mail::generate_footer(&unencryptable).as_bytes());
+                    let header = context.mail.header.without_recipients(&unencryptable);
+                    let inner_mail = MailContext::generate_inner_mail(&header, encrypted_body.into());
+
+                    // If an error occures, the body is not exchanged.
+                    match crypto::encrypt(context, inner_mail.to_string().as_bytes(), &encryptable) {
+                        Ok(encrypted) => {
+                            // replace the body of the mail with an encrypted,
+                            // mime encoded version.
+                            let outer_mail = MailContext::generate_outer_mail(encrypted);
+                            if cx.actions.replace_body(
+                                    outer_mail
+                                    .body_to_string()
+                                    .as_bytes()).await.is_err() {
+                                log::error!("Cannot exchange body");
+                                return Status::Continue;
+                            }
+
+                            // Adjust headers
+                            // XXX error handling
+
+                            // Remove unencryptable recipients from 'to', 'cc'
+                            // and 'bcc'.
+                            for (key, value) in header.iter_lines() {
+                                match key.as_bytes().to_ascii_lowercase().as_slice() {
+                                    b"to"
+                                    | b"cc"
+                                    | b"bcc" => {
+                                        let _ = cx.actions.change_header(
+                                            key.clone(),
+                                            1,
+                                            Some(value.clone())
+                                        ).await;
+                                    },
+                                    _ => { }
+                                }
+                            }
+                            // Also remove recipients via the milter protocol.
+                            for rcpt in unencryptable {
+                                let _ = cx.actions.delete_recipient(rcpt.email).await;
+                            }
+
+                            // This is Content-Type related.
+                            for line in outer_mail.get_header().iter_lines() {
+                                // XXX: handle errors
+                                if let Ok(key) = line.key_as_cstring() {
+                                    if let Ok(value) = line.value_as_cstring() {
+                                        let _ = cx.actions.change_header(
+                                            key, 1,
+                                            Some(value)
+                                        ).await;
+                                    }
+                                }
+                            }
+                            // Change the subject.
+                            let _ = cx.actions.change_header(
+                                "Subject",
+                                1,
+                                Some(context.subject_replacement.clone())).await;
+                        },
+                        Err(e) => {
+                            log::error!("{}", e);
+                        }
+                    }
+                },
+                ProtectionPossibility::NoProtection => {
+                    log::debug!("not encryptable");
+                    // do nothing
                 }
             }
         }
 
-        log::logger().flush();
         Status::Continue
     }
 

src/mail.rs

@@ -1,8 +1,24 @@
 //! mail functions
 
+use anyhow::Result;
+use bytes::Bytes;
+use bytes::BytesMut;
 use std::ffi::CString;
 use sequoia_openpgp::packet::UserID;
+use lettre::transport::smtp::{
+    client::SmtpConnection, commands::*, extension::ClientId, SMTP_PORT,
+};
+use lettre::Address;
+use tokio::task::JoinSet;
+use std::time::Duration;
+use chrono::Utc;
 
+use crate::types::cheader::CHeader;
+use crate::types::defaults;
+use crate::types::errors::HuskError;
+use crate::types::recipient::Recipient;
+
+/// Parse the user id fields from a string.
 pub fn to_userid(rcpt: &CString) -> Option<UserID> {
     match rcpt.to_str() {
         Ok(s) => Some(UserID::from(s)),
@@ -10,6 +26,7 @@ pub fn to_userid(rcpt: &CString) -> Option<UserID> {
     }
 }
 
+/// Get the email from the string representation of a user id.
 pub fn to_email(rcpt: &CString) -> Option<String> {
     if let Some(u) = to_userid(rcpt) {
        if let Ok(Some(e)) = u.email() { Some(e.to_string()) }
@@ -32,3 +49,136 @@ pub fn is_email(email: &str) -> bool {
 pub fn is_domain(domain: &str) -> bool {
     is_email(format!("test@{}", domain).as_str())
 }
+
+pub async fn smtp_inject(from: String, to: &Vec<Recipient<'_>>, header: CHeader, body: &Bytes) -> Result<()> {
+
+    let mut joinset: JoinSet<Result<()>> = JoinSet::new();
+
+    log::debug!("smtp inject: from {}", from);
+
+    // build message
+    let mut header_size = 0;
+    for (key, value) in header.iter_lines() {
+        header_size += key.count_bytes();
+        header_size += value.count_bytes();
+        header_size += 4; // 4 is ': ' plus '\r\n'
+    }
+
+    // The size of the whole message the sum of header and body size + '\r\n'
+    // as the dividing empty line.
+    let mut message = BytesMut::with_capacity(header_size + body.len() + 2);
+    for (key, value) in header.iter_lines() {
+        message.extend_from_slice(key.as_bytes());
+        message.extend_from_slice(": ".as_bytes());
+        message.extend_from_slice(value.as_bytes());
+        message.extend_from_slice("\r\n".as_bytes());
+    }
+    message.extend_from_slice(b"\r\n");
+    message.extend_from_slice(&body[..]);
+
+    // convert addresses
+    let from_email = CString::new(from.clone())?;
+    let from_email = to_email(&from_email).unwrap(); // XXX
+    let from_email: Address = from_email.try_into()?;
+
+    let mut rcpts: Vec<Address> = Vec::new();
+    for rcpt in to {
+        let rcpt = rcpt.email.clone();
+        rcpts.push(rcpt.try_into()?);
+    }
+
+    let my_id = ClientId::Domain(defaults::HELO_REINJECT_ID.to_owned()); // TODO: add secret token?
+    joinset.spawn(async move {
+
+        // XXX
+        // We connect to localhost - every other host would require implementing
+        // TLS. The milter protocol is unencrypted anyways.
+        match SmtpConnection::connect(("localhost", SMTP_PORT), Some(Duration::from_secs(5)), &my_id, None, None) {
+            Ok(mut client) => {
+                log::debug!("connected - start sending");
+
+                client.command(Mail::new(Some(from_email),vec![]))?;
+                for rcpt in rcpts {
+                    client.command(Rcpt::new(rcpt, vec![]))?;
+                }
+                client.command(Data)?;
+                client.message(&message)?;
+                client.command(Quit)?;
+
+                Ok(())
+            },
+            Err(e) => {
+                log::error!("cannot connect to localhost:{} - {:?}", SMTP_PORT, e);
+                Err(e.into())
+            }
+        }
+    });
+
+    match joinset.join_all().await.first() {
+        Some(Ok(_)) => {
+            log::debug!("mail injection done.");
+            Ok(())
+        },
+        Some(Err(e)) => {
+            log::error!("mail injection failed: {:?}", e);
+            Err(HuskError::SmtpInjectionFailure(e.to_string()).into())
+        },
+        _ => {
+            log::error!("mail injection failed without reason");
+            Err(HuskError::SmtpInjectionFailure("no reason".to_string()).into())
+        },
+    }
+}
+
+pub fn generate_footer(rcpts: &Vec<Recipient>) -> String {
+    internal_generate_footer(Utc::now().to_rfc2822(), rcpts)
+}
+
+pub(crate) fn internal_generate_footer(now: String, other_rpcts: &Vec<Recipient>) -> String {
+    let mut footer = defaults::FOOTER.replace("{date}", now.as_str());
+
+    if ! other_rpcts.is_empty() {
+        let rcpts = other_rpcts.iter()
+            .map(|r| r.email.clone())
+            .collect::<Vec<String>>()
+            .join(", ");
+        footer.push_str(
+            defaults::FOOTER_RECIPIENTS.replace(
+                "{rcpts}",
+                &rcpts).as_str()
+            );
+    }
+    footer
+}
+
+
+#[cfg(test)]
+pub mod tests {
+
+    use crate::mail::internal_generate_footer;
+    use crate::types::recipient::Recipient;
+
+    #[test]
+    fn test_footer() {
+
+        let rcpts = vec![
+            Recipient {
+                email: "alice@example.com".to_string(),
+                certs: Vec::new()
+            },
+            Recipient {
+                email: "bob@example.com".to_string(),
+                certs: Vec::new()
+            }
+        ];
+
+        let footer = internal_generate_footer(
+            "1.1.1970".to_string(),
+            &rcpts
+        );
+
+        assert!(footer.contains("1.1.1970"));
+        assert!(footer.contains("alice@example.com"));
+        assert!(footer.contains("bob@example.com"));
+    }
+}

src/types/cheader.rs

@@ -5,6 +5,11 @@
 use std::ffi::CString;
 use std::fmt;
 
+use anyhow::Result;
+
+use crate::types::recipient::Recipient;
+
+#[derive(Debug, PartialEq, Clone)]
 pub struct CHeader {
     lines: Vec<(CString, CString)>
 }
@@ -52,6 +57,47 @@ impl CHeader {
     pub fn iter_lines(&self) -> std::slice::Iter<'_, (CString, CString)> {
         self.lines.iter()
     }
+
+    /// Remove a recipient from a value taken from a to, cc or bcc header
+    /// line. Only the email address is matched.
+    pub fn remove_recipient(header_value: &CString, to_remove: &Vec<Recipient>) -> Result<CString> {
+        let content = String::from_utf8_lossy(header_value.as_bytes());
+        let parts = content.split(",")
+            .filter(|part| {
+                let mut keep = true;
+                let p = part.to_ascii_lowercase();
+                for rcpt in to_remove {
+                    let rcpt = rcpt.email.to_ascii_lowercase();
+                    if p.contains(&rcpt) { keep = false; break; }
+                }
+                keep
+            })
+            .collect::<Vec<&str>>();
+        CString::new(parts.join(","))
+            .map_err(|e| e.into())
+    }
+
+    /// Returns a new header with `to_remove` removed from to, cc and bcc.
+    pub fn without_recipients(&self, to_remove: &Vec<Recipient>) -> CHeader {
+        let mut result = CHeader::new();
+
+        for (key, value) in self.iter_lines() {
+            let new_value = match key.as_bytes().to_ascii_lowercase().as_slice() {
+                b"to"
+                | b"cc"
+                | b"bcc" => Self::remove_recipient(value, to_remove),
+                _ => Ok(value.clone())
+            };
+            if let Ok(value) = new_value {
+                if ! value.is_empty() {
+                    result.append(key.clone(), value);
+                }
+            }
+        }
+
+        result
+    }
+
 }
 
 impl fmt::Display for CHeader {
@@ -75,10 +121,12 @@ impl fmt::Display for CHeader {
 #[cfg(test)]
 pub mod tests {
     use std::ffi::CString;
+    use crate::types::recipient::Recipient;
+
     use super::CHeader;
 
 
-#[test]
+    #[test]
     pub fn basic_functionality() {
         let cheader = CHeader::new()
             .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
@@ -87,7 +135,7 @@ pub mod tests {
         assert_eq!("Content-Type: text/plain\r\nContent-Transfer-Encoding: 7bit\r\n", cheader.to_string());
     }
 
-#[test]
+    #[test]
     pub fn find() {
         let cheader = CHeader::new()
             .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
@@ -103,7 +151,7 @@ pub mod tests {
         assert_eq!("text/plain", value);
     }
 
-#[test]
+    #[test]
     pub fn find_none() {
         let cheader = CHeader::new()
             .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
@@ -114,7 +162,7 @@ pub mod tests {
         assert!(line.is_none());
     }
 
-#[test]
+    #[test]
     pub fn find_with_default() {
         let cheader = CHeader::new()
             .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
@@ -124,5 +172,27 @@ pub mod tests {
 
         assert_eq!(value, "baaz");
     }
+
+    #[test]
+    pub fn remove_recipients() {
+        let header = CHeader::new()
+            .add(CString::new("To").unwrap(), CString::new("Alice <alice@example.com>, Bob <bob@other.org>").unwrap())
+            .add(CString::new("Cc").unwrap(), CString::new("carol@example.com").unwrap());
+
+        let modified_header = header.without_recipients(
+            &vec![ Recipient::from("bob@other.org".to_string()) ]
+        );
+        let expected_header = CHeader::new()
+            .add(CString::new("To").unwrap(), CString::new("Alice <alice@example.com>").unwrap())
+            .add(CString::new("Cc").unwrap(), CString::new("carol@example.com").unwrap());
+        assert_eq!(modified_header, expected_header);
+
+        let modified_header = header.without_recipients(
+            &vec![ Recipient::from("CaRol@exAmple.Com".to_string()) ]
+        );
+        let expected_header = CHeader::new()
+            .add(CString::new("To").unwrap(), CString::new("Alice <alice@example.com>, Bob <bob@other.org>").unwrap());
+        assert_eq!(modified_header, expected_header);
+    }
 }
 

src/types/defaults.rs

@@ -8,6 +8,12 @@ pub const SUBJECT_REPLACEMENT: &str = "...";
 
 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]

src/types/errors.rs

@@ -24,4 +24,6 @@ pub enum HuskError {
     InvalidDomainName(String),
     #[error("Certificate has no user ids - {0}")]
     NoUserIDs(String),
+    #[error("Failing to send mail: {0}")]
+    SmtpInjectionFailure(String),
 }

src/types/introducer.rs

@@ -110,7 +110,7 @@ use std::fmt::{Display, Formatter};
 impl Display for Introducer {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         // XXX: This is unsafe as ANSI control chars are not handled.
-        let uids = self.cert.userids()
+        let uids = self.cert.self_signed_userids()
             .map(|u| String::from_utf8_lossy(u.userid().value()).to_string())
             .collect::<Vec<String>>()
             .join(", ");

src/types/mail_context.rs

@@ -15,17 +15,15 @@ use crate::types::mime::header::Header;
 use crate::types::mime::part::Part;
 use crate::types::mime::multi_part::MultiPart;
 
-#[derive(PartialEq)]
-pub enum ProtectionPossibility {
+pub enum ProtectionPossibility<'mc> {
     // no recipient has a cert
     NoProtection,
     // some recipients have a cert (but not all)
-    Partial,
+    Partial(Vec<Recipient<'mc>>, Vec<Recipient<'mc>>),
     // all recipients have a cert
     Full
 }
 
-
 pub struct MailContext<'mc> {
     pub sender:     Option<String>,
     pub recipients: Vec<Recipient<'mc>>,
@@ -84,8 +82,8 @@ impl<'mc> MailContext<'mc> {
         buffer.into()
     }
 
-    pub fn generate_inner_mail(&self, body: Bytes) -> MultiPart<'mc> {
-        let header = &self.header;
+    pub fn generate_inner_mail(header: &CHeader, body: Bytes) -> MultiPart<'mc> {
+        //let header = &self.header;
         let inner = Part::with_body(body)
             .set_header(Header::new()
                 .add(
@@ -158,22 +156,27 @@ impl<'mc> Default for MailContext<'mc> {
     }
 }
 
-impl From<&MailContext<'_>> for ProtectionPossibility {
-    fn from(mail_context: &MailContext<'_>) -> ProtectionPossibility {
+impl<'mc> From<&MailContext<'mc>> for ProtectionPossibility<'mc> {
+    fn from(mail_context: &MailContext<'mc>) -> ProtectionPossibility<'mc> {
         let mut can_encrypt = false;
         let mut cannot_encrypt = false;
 
+        let mut encrypted_rcpt = Vec::new();
+        let mut unencrypted_rcpt = Vec::new();
+
         for rcpt in mail_context.recipients.iter() {
             if rcpt.can_encrypt() {
                 can_encrypt = true;
+                encrypted_rcpt.push(rcpt.clone());
             } else {
                 cannot_encrypt = true;
+                unencrypted_rcpt.push(rcpt.clone());
             }
         }
 
         match (can_encrypt, cannot_encrypt) {
             (true, false) => ProtectionPossibility::Full,
-            (true, true) => ProtectionPossibility::Partial,
+            (true, true) => ProtectionPossibility::Partial(encrypted_rcpt, unencrypted_rcpt),
             (false, true) => ProtectionPossibility::NoProtection,
             // (false, false) occurs if there are no recipients
             (false, false) => ProtectionPossibility::NoProtection,
@@ -185,8 +188,17 @@ impl From<&MailContext<'_>> for ProtectionPossibility {
 mod tests {
 
     use std::ffi::CString;
+    use std::sync::Arc;
+
+    use anyhow::Result;
+    use sequoia_cert_store::LazyCert;
+    use sequoia_openpgp::cert::CertBuilder;
+
     use crate::types::cheader::CHeader;
     use crate::types::mail_context::MailContext;
+    use crate::types::recipient::Recipient;
+
+    use super::ProtectionPossibility;
 
     #[test]
     fn test_inner_mail() {
@@ -202,8 +214,7 @@ mod tests {
 
         let orig_body = "This is the body".as_bytes().to_vec();
 
-        let context = MailContext::from_header(orig_header);
-        let inner_mail = context.generate_inner_mail(orig_body.into());
+        let inner_mail = MailContext::generate_inner_mail(&orig_header, orig_body.into());
 
         let intended_result = [
             format!("Content-Type: multipart/mixed; boundary=\"{}\"; protected-headers=\"v1\"", inner_mail.get_boundary()),
@@ -220,5 +231,80 @@ mod tests {
 
         assert_eq!(intended_result, inner_mail.to_string());
     }
+
+    #[test]
+    fn test_recipient_splitting() -> Result<()> {
+        let (alice_cert, _) = CertBuilder::general_purpose(["alice@example.com"])
+            .generate()?;
+
+        // Mixed recipients: alice can encrypt, bob doesn't.
+        let mut mail_context = MailContext::new();
+        mail_context.recipients = vec![
+            Recipient {
+                email: "alice@example.com".to_string(),
+                certs: vec![Arc::new(LazyCert::from_cert(alice_cert))],
+            },
+            Recipient {
+                email: "bob@example.com".to_string(),
+                certs: Vec::new()
+            }
+        ];
+
+        let protection = ProtectionPossibility::from(&mail_context);
+
+        assert!(matches!(protection, ProtectionPossibility::Partial(_, _)));
+
+        if let ProtectionPossibility::Partial(a, b) = protection {
+            assert_eq!(a.len(), 1);
+            assert_eq!(b.len(), 1);
+
+            let alice = a.iter().next().unwrap();
+            assert_eq!(alice.email, "alice@example.com");
+
+            let bob = b.iter().next().unwrap();
+            assert_eq!(bob.email, "bob@example.com");
+        } else {
+            return Err(anyhow::anyhow!("this should be unreachable"));
+        }
+
+        // Both recipients can encrypt.
+        let (alice_cert, _) = CertBuilder::general_purpose(["alice@example.com"])
+            .generate()?;
+        let (bob_cert, _) = CertBuilder::general_purpose(["bob@example.com"])
+            .generate()?;
+        let mut mail_context = MailContext::new();
+        mail_context.recipients = vec![
+            Recipient {
+                email: "alice@example.com".to_string(),
+                certs: vec![Arc::new(LazyCert::from_cert(alice_cert))],
+            },
+            Recipient {
+                email: "bob@example.com".to_string(),
+                certs: vec![Arc::new(LazyCert::from_cert(bob_cert))],
+            }
+        ];
+
+        let protection = ProtectionPossibility::from(&mail_context);
+
+        assert!(matches!(protection, ProtectionPossibility::Full));
+
+        // No recipient can encrypt.
+        let mut mail_context = MailContext::new();
+        mail_context.recipients = vec![
+            Recipient {
+                email: "alice@example.com".to_string(),
+                certs: Vec::new()
+            },
+            Recipient {
+                email: "bob@example.com".to_string(),
+                certs: Vec::new()
+            }
+        ];
+
+        let protection = ProtectionPossibility::from(&mail_context);
+
+        assert!(matches!(protection, ProtectionPossibility::NoProtection));
+        Ok(())
+    }
 }