Check for encryption

- collect body of incoming mail.
- check if incoming mail is already encrypted - dont touch it if it is.
- check if recipients of that mail can encrypt.

src/crypto.rs

@@ -7,9 +7,10 @@
 use std::sync::Arc;
 
 use anyhow;
-use sequoia_openpgp::parse::Parse;
+use bytes::Bytes;
+use sequoia_openpgp::parse::{PacketParser, PacketParserResult, Parse};
 use sequoia_openpgp::policy::StandardPolicy;
-use sequoia_openpgp::{Fingerprint, Cert};
+use sequoia_openpgp::{Fingerprint, Cert, Packet};
 use sequoia_openpgp::cert::raw::RawCertParser;
 use sequoia_cert_store::{Store, CertStore, LazyCert};
 use sequoia_wot::{self as wot};
@@ -125,3 +126,31 @@ pub fn get_introducers<'c>(cert_store: &CertStore<'c>, policy: &StandardPolicy,
 
     result
 }
+
+pub fn is_encrypted(body: &Bytes) -> bool {
+
+    let mut ppr = match PacketParser::from_bytes(body) {
+        Ok(pp) => pp,
+        Err(_) => return false, // no OpenPGP artifacts
+    };
+
+    let mut encrypted: bool = false;
+
+    while let PacketParserResult::Some(pp) = ppr {
+        if let Packet::SEIP(_) = pp.packet {
+            encrypted = true;
+        }
+
+        // parse the whole message, don't stop at first SEIP
+        ppr = match pp.recurse() {
+            Ok((_, next_ppr)) => next_ppr,
+            Err(_) => return false, // broken artifact -> not encrypted
+        }
+    }
+    if let PacketParserResult::EOF(eof) = ppr {
+        if eof.is_message().is_ok() && encrypted  {
+            return true;
+        }
+    }
+    false
+}

src/daemon/mod.rs

@@ -27,6 +27,8 @@ use indymilter::{
 use crate::types::husk_context::HuskContext;
 use crate::config::{HuskConfig, HuskConfigContainer};
 use crate::mail;
+use crate::crypto;
+use crate::types::mail_context::ProtectionPossibility;
 
 pub struct Daemon { }
 
@@ -153,7 +155,7 @@ impl Daemon {
     async fn handle_data(cx: &mut Context<HuskContext<'_>>) -> Status {
         log::debug!("DATA");
 
-        if let Some(ref mut context) = cx.data {
+        if let Some(ref mut _context) = cx.data {
             // XXX: check for early accepting
             // if there are no recipients with authenticated certificates
             // tell the MTA that this milter is done and the mail can be further
@@ -176,10 +178,15 @@ impl Daemon {
         Status::Continue
     }
 
-    async fn handle_body(_cx: &mut Context<HuskContext<'_>>, chunk: Bytes) -> Status {
+    async fn handle_body(cx: &mut Context<HuskContext<'_>>, chunk: Bytes) -> Status {
         log::debug!("BODY: chunk with {:?} bytes received", &chunk.len());
 
-        Status::Continue
+        if let Some(ref mut context) = cx.data {
+            context.mail.add_chunk(chunk);
+            Status::Continue
+        } else {
+            Status::Tempfail
+        }
     }
 
     async fn handle_eom(cx: &mut EomContext<HuskContext<'_>>) -> Status {
@@ -188,6 +195,30 @@ impl Daemon {
         if let Some(ref mut context) = cx.data {
             log::debug!("Mail from {:?} complete", context.mail.sender);
             log::debug!("recipients: {:?}", context.mail.recipients);
+            log::debug!("body size: {}", context.mail.body_size);
+
+            let body = context.mail.collect_body();
+
+            // check if mail is already encrypted. If it is, keep it as such.
+            if crypto::is_encrypted(&body) {
+                log::info!("encrypted mail detected");
+                return Status::Accept;
+            }
+
+
+            // possible protection
+            // none -> accept
+            // partial -> accept (later: split)
+            // full -> encrypt
+            //   check mailbody
+            //   is encrypted -> accept
+            //   else -> encrypt
+
+            let protection = ProtectionPossibility::from(&context.mail);
+
+            if protection == ProtectionPossibility::Full {
+                // encrypt
+            }
         }
 
         Status::Continue

src/types/mail_context.rs

@@ -5,16 +5,25 @@
 //
 
 use std::sync::Arc;
+use bytes::{Bytes, BytesMut};
 use sequoia_cert_store::LazyCert;
 
 use crate::types::recipient::Recipient;
 
+#[derive(PartialEq)]
+pub enum ProtectionPossibility {
+    NoProtection,
+    Partial,
+    Full
+}
+
+
 pub struct MailContext<'mc> {
     pub sender:     Option<String>,
     pub recipients: Vec<Recipient<'mc>>,
     // header
-    // body
+    body: Vec<Bytes>,
-    // body size
+    pub body_size: usize, 
 }
 
 impl<'mc> MailContext<'mc> {
@@ -23,6 +32,8 @@ impl<'mc> MailContext<'mc> {
         MailContext {
             sender: None,
             recipients: Vec::new(),
+            body: Vec::new(),
+            body_size: 0,
         }
     }
 
@@ -39,4 +50,39 @@ impl<'mc> MailContext<'mc> {
         Ok(())
     }
 
+    pub fn add_chunk(&mut self, chunk: Bytes) {
+        self.body_size += chunk.len();
+        self.body.push(chunk);
+    }
+
+    pub fn collect_body(&self) -> Bytes {
+        let mut buffer = BytesMut::with_capacity(self.body_size);
+        for chunk in &self.body {
+            buffer.extend_from_slice(&chunk[..]);
+        }
+        buffer.into()
+    }
+
+}
+
+impl From<&MailContext<'_>> for ProtectionPossibility {
+    fn from(mail_context: &MailContext<'_>) -> ProtectionPossibility {
+        let mut can_encrypt = false;
+        let mut cannot_encrypt = false;
+
+        for rcpt in mail_context.recipients.iter() {
+            if rcpt.can_encrypt() {
+                can_encrypt = true;
+            } else {
+                cannot_encrypt = true;
+            }
+        }
+
+        match (can_encrypt, cannot_encrypt) {
+            (true, false) => ProtectionPossibility::Full,
+            (true, true) => ProtectionPossibility::Partial,
+            (false, true) => ProtectionPossibility::NoProtection,
+            (false, false) => ProtectionPossibility::NoProtection, // this should not occure
+        }
+    }
 }

src/types/recipient.rs

@@ -36,4 +36,13 @@ impl TryFrom<CString> for Recipient<'_> {
     }
 }
 
+impl Recipient<'_> {
+    pub fn can_encrypt(&self) -> bool {
+        if self.certs.len() == 0 { 
+            return false;
+        }
+        true
+    }
+}
+