Added fuzzing.

fuzz/.gitignore

@@ -0,0 +1,3 @@
+target
+corpus
+artifacts

fuzz/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "smtp-proto-fuzz"
+version = "0.0.0"
+authors = ["Automatically generated"]
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.smtp-proto]
+path = ".."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[[bin]]
+name = "smtp_proto"
+path = "fuzz_targets/smtp_proto.rs"
+test = false
+doc = false

fuzz/fuzz_targets/smtp_proto.rs

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2020-2023, Stalwart Labs Ltd.
+ *
+ * This file is part of the Stalwart SMTP protocol parser.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ * in the LICENSE file at the top-level directory of this distribution.
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * You can be released from the requirements of the AGPLv3 license by
+ * purchasing a commercial license. Please contact licensing@stalw.art
+ * for more details.
+*/
+
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+use smtp_proto::{
+    request::{
+        parser::Rfc5321Parser,
+        receiver::{
+            BdatReceiver, DataReceiver, DummyDataReceiver, DummyLineReceiver, LineReceiver,
+            RequestReceiver,
+        },
+    },
+    response::parser::ResponseReceiver,
+    EhloResponse, Request,
+};
+
+static RFC5321_ALPHABET: &[u8] = b"0123456789abcdefghijklmnopqrstuvwxyz:=-<>,; \r\n";
+
+fuzz_target!(|data: &[u8]| {
+    let data_rfc5321 = into_alphabet(data, RFC5321_ALPHABET);
+
+    for bytes in [data, &data_rfc5321] {
+        let _ = Request::parse(&mut bytes.iter());
+        let _ = RequestReceiver::default().ingest(&mut bytes.iter(), &[]);
+        let _ = DataReceiver::new().ingest(&mut bytes.iter(), &mut vec![]);
+        let _ = BdatReceiver::new(bytes.len(), true).ingest(&mut bytes.iter(), &mut vec![]);
+        let _ = BdatReceiver::new(bytes.len(), false).ingest(&mut bytes.iter(), &mut vec![]);
+        let _ = DummyDataReceiver::new_bdat(bytes.len()).ingest(&mut bytes.iter());
+        let _ = DummyDataReceiver::new_data(&DataReceiver::new()).ingest(&mut bytes.iter());
+        let _ = LineReceiver::new(()).ingest(&mut bytes.iter());
+        let _ = DummyLineReceiver::default().ingest(&mut bytes.iter());
+        let _ = ResponseReceiver::default().parse(&mut bytes.iter());
+        let _ = EhloResponse::<String>::parse(&mut bytes.iter());
+
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).hashed_value();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).hashed_value_long();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).address();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).string();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).text();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).xtext();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).seek_char(0);
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).seek_lf();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).next_char();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).read_char();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).size();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).integer();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).timestamp();
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).mail_from_parameters(String::new());
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).rcpt_to_parameters(String::new());
+        let _ = Rfc5321Parser::new(&mut bytes.iter()).mechanism();
+    }
+});
+
+fn into_alphabet(data: &[u8], alphabet: &[u8]) -> Vec<u8> {
+    data.iter()
+        .map(|&byte| alphabet[byte as usize % alphabet.len()])
+        .collect()
+}

src/request/receiver.rs

@@ -71,7 +71,7 @@ impl RequestReceiver {
                 Err(Error::NeedsMoreData { bytes_left }) => {
                     if bytes_left > 0 {
                         if bytes_left < MAX_LINE_LENGTH {
-                            self.buf = buf[buf.len() - bytes_left..].to_vec();
+                            self.buf = buf[buf.len().saturating_sub(bytes_left)..].to_vec();
                         } else {
                             return Err(Error::ResponseTooLong);
                         }