Fix a number of bugs in zbase32 and add a fuzzer which caught them.

fuzz/src/bin/gen_target.sh

@@ -11,6 +11,7 @@ GEN_TEST chanmon_consistency
 GEN_TEST full_stack
 GEN_TEST peer_crypt
 GEN_TEST router
+GEN_TEST zbase32
 
 GEN_TEST msg_accept_channel msg_targets::
 GEN_TEST msg_announcement_signatures msg_targets::

fuzz/src/bin/zbase32_target.rs

@@ -0,0 +1,102 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+// This file is auto-generated by gen_target.sh based on target_template.txt
+// To modify it, modify target_template.txt and run gen_target.sh instead.
+
+#![cfg_attr(feature = "libfuzzer_fuzz", no_main)]
+
+extern crate lightning_fuzz;
+use lightning_fuzz::zbase32::*;
+
+#[cfg(feature = "afl")]
+#[macro_use] extern crate afl;
+#[cfg(feature = "afl")]
+fn main() {
+	fuzz!(|data| {
+		zbase32_run(data.as_ptr(), data.len());
+	});
+}
+
+#[cfg(feature = "honggfuzz")]
+#[macro_use] extern crate honggfuzz;
+#[cfg(feature = "honggfuzz")]
+fn main() {
+	loop {
+		fuzz!(|data| {
+			zbase32_run(data.as_ptr(), data.len());
+		});
+	}
+}
+
+#[cfg(feature = "libfuzzer_fuzz")]
+#[macro_use] extern crate libfuzzer_sys;
+#[cfg(feature = "libfuzzer_fuzz")]
+fuzz_target!(|data: &[u8]| {
+	zbase32_run(data.as_ptr(), data.len());
+});
+
+#[cfg(feature = "stdin_fuzz")]
+fn main() {
+	use std::io::Read;
+
+	let mut data = Vec::with_capacity(8192);
+	std::io::stdin().read_to_end(&mut data).unwrap();
+	zbase32_run(data.as_ptr(), data.len());
+}
+
+#[test]
+fn run_test_cases() {
+	use std::fs;
+	use std::io::Read;
+	use lightning_fuzz::utils::test_logger::StringBuffer;
+
+	use std::sync::{atomic, Arc};
+	{
+		let data: Vec<u8> = vec![0];
+		zbase32_run(data.as_ptr(), data.len());
+	}
+	let mut threads = Vec::new();
+	let threads_running = Arc::new(atomic::AtomicUsize::new(0));
+	if let Ok(tests) = fs::read_dir("test_cases/zbase32") {
+		for test in tests {
+			let mut data: Vec<u8> = Vec::new();
+			let path = test.unwrap().path();
+			fs::File::open(&path).unwrap().read_to_end(&mut data).unwrap();
+			threads_running.fetch_add(1, atomic::Ordering::AcqRel);
+
+			let thread_count_ref = Arc::clone(&threads_running);
+			let main_thread_ref = std::thread::current();
+			threads.push((path.file_name().unwrap().to_str().unwrap().to_string(),
+				std::thread::spawn(move || {
+					let string_logger = StringBuffer::new();
+
+					let panic_logger = string_logger.clone();
+					let res = if ::std::panic::catch_unwind(move || {
+						zbase32_test(&data, panic_logger);
+					}).is_err() {
+						Some(string_logger.into_string())
+					} else { None };
+					thread_count_ref.fetch_sub(1, atomic::Ordering::AcqRel);
+					main_thread_ref.unpark();
+					res
+				})
+			));
+			while threads_running.load(atomic::Ordering::Acquire) > 32 {
+				std::thread::park();
+			}
+		}
+	}
+	for (test, thread) in threads.drain(..) {
+		if let Some(output) = thread.join().unwrap() {
+			println!("Output of {}:\n{}", test, output);
+			panic!();
+		}
+	}
+}

fuzz/src/lib.rs

@@ -18,5 +18,6 @@ pub mod chanmon_consistency;
 pub mod full_stack;
 pub mod peer_crypt;
 pub mod router;
+pub mod zbase32;
 
 pub mod msg_targets;

fuzz/src/zbase32.rs

@@ -0,0 +1,33 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+use lightning::util::zbase32;
+
+use utils::test_logger;
+
+#[inline]
+pub fn do_test(data: &[u8]) {
+	let res = zbase32::encode(data);
+	assert_eq!(&zbase32::decode(&res).unwrap()[..], data);
+
+	if let Ok(s) = std::str::from_utf8(data) {
+		if let Ok(decoded) = zbase32::decode(s) {
+			assert_eq!(&zbase32::encode(&decoded), &s.to_ascii_lowercase());
+		}
+	}
+}
+
+pub fn zbase32_test<Out: test_logger::Output>(data: &[u8], _out: Out) {
+	do_test(data);
+}
+
+#[no_mangle]
+pub extern "C" fn zbase32_run(data: *const u8, datalen: usize) {
+	do_test(unsafe { std::slice::from_raw_parts(data, datalen) });
+}

fuzz/targets.h

@@ -4,6 +4,7 @@ void chanmon_consistency_run(const unsigned char* data, size_t data_len);
 void full_stack_run(const unsigned char* data, size_t data_len);
 void peer_crypt_run(const unsigned char* data, size_t data_len);
 void router_run(const unsigned char* data, size_t data_len);
+void zbase32_run(const unsigned char* data, size_t data_len);
 void msg_accept_channel_run(const unsigned char* data, size_t data_len);
 void msg_announcement_signatures_run(const unsigned char* data, size_t data_len);
 void msg_channel_reestablish_run(const unsigned char* data, size_t data_len);

lightning/src/util/zbase32.rs

@@ -25,8 +25,9 @@ SOFTWARE.
 
 const ALPHABET: &'static [u8] = b"ybndrfg8ejkmcpqxot1uwisza345h769";
 
+/// Encodes some bytes as a zbase32 string
 pub fn encode(data: &[u8]) -> String {
-    let mut ret = Vec::with_capacity((data.len() + 3) / 4 * 5);
+    let mut ret = Vec::with_capacity((data.len() + 4) / 5 * 8);
 
     for chunk in data.chunks(5) {
         let buf = {
@@ -47,11 +48,11 @@ pub fn encode(data: &[u8]) -> String {
         ret.push(ALPHABET[(buf[4] & 0x1F) as usize]);
     }
 
-    if data.len() % 5 != 0 {
-        let len = ret.len();
-        let num_extra = 8 - (data.len() % 5 * 8 + 4) / 5;
-        ret.truncate(len - num_extra);
-    }
+    ret.truncate((data.len() * 8 + 4) / 5);
+
+    // Check that our capacity calculation doesn't under-shoot in fuzzing
+    #[cfg(fuzzing)]
+    assert_eq!(ret.capacity(), (data.len() + 4) / 5 * 8);
 
     String::from_utf8(ret).unwrap()
 }
@@ -62,21 +63,29 @@ const INV_ALPHABET: [i8; 43] = [
     21, 9, 10, -1, 11, 2, 16, 13, 14, 4, 22, 17, 19, -1, 20, 15, 0, 23,
 ];
 
-pub fn decode(data: &str) -> Result<Vec<u8>, &'static str> {
+/// Decodes a zbase32 string to the original bytes, failing if the string was not encoded by a
+/// proper zbase32 encoder.
+pub fn decode(data: &str) -> Result<Vec<u8>, ()> {
     if !data.is_ascii() {
-        return Err("Data is not zbase32 encoded");
+        return Err(());
     }
 
     let data = data.as_bytes();
     let output_length = data.len() * 5 / 8;
-    let mut ret = Vec::with_capacity((output_length + 4) / 5 * 5);
+    if data.len() > (output_length * 8 + 4) / 5 {
+        // If the string has more charachters than are required to encode the number of bytes
+        // decodable, treat the string as invalid.
+        return Err(());
+    }
+
+    let mut ret = Vec::with_capacity((data.len() + 7) / 8 * 5);
 
     for chunk in data.chunks(8) {
         let buf = {
             let mut buf = [0u8; 8];
             for (i, &c) in chunk.iter().enumerate() {
                 match INV_ALPHABET.get(c.to_ascii_uppercase().wrapping_sub(b'0') as usize) {
-                    Some(&-1) | None => return Err("Data is not zbase32 encoded"),
+                    Some(&-1) | None => return Err(()),
                     Some(&value) => buf[i] = value as u8,
                 };
             }
@@ -88,10 +97,22 @@ pub fn decode(data: &str) -> Result<Vec<u8>, &'static str> {
         ret.push((buf[4] << 7) | (buf[5] << 2) | (buf[6] >> 3));
         ret.push((buf[6] << 5) | buf[7]);
     }
-    ret.truncate(output_length);
+    for c in ret.drain(output_length..) {
+        if c != 0 {
+            // If the original string had any bits set at positions outside of the encoded data,
+            // treat the string as invalid.
+            return Err(());
+        }
+    }
+
+    // Check that our capacity calculation doesn't under-shoot in fuzzing
+    #[cfg(fuzzing)]
+    assert_eq!(ret.capacity(), (data.len() + 7) / 8 * 5);
+
     Ok(ret)
 }
 
+#[cfg(test)]
 mod tests {
     use super::*;
 
@@ -125,7 +146,7 @@ mod tests {
 
     #[test]
     fn test_decode_wrong() {
-        let WRONG_DATA = &["00", "l1", "?", "="];
+        const WRONG_DATA: &[&str] = &["00", "l1", "?", "="];
 
         for &data in WRONG_DATA {
             match decode(data) {