From a402b5e3a5cd7d8a68d668b07021528490752621 Mon Sep 17 00:00:00 2001
From: Alexandra <aspasparagus@gmail.com>
Date: Tue, 8 Apr 2025 20:10:21 +0200
Subject: [PATCH 1/2] mcookie: fix max size option

---
 src/uu/mcookie/src/mcookie.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/uu/mcookie/src/mcookie.rs b/src/uu/mcookie/src/mcookie.rs
index 843f05b..997ca22 100644
--- a/src/uu/mcookie/src/mcookie.rs
+++ b/src/uu/mcookie/src/mcookie.rs
@@ -29,6 +29,9 @@ mod options {
 const ABOUT: &str = help_about!("mcookie.md");
 const USAGE: &str = help_usage!("mcookie.md");
 
+const RANDOM_BYTES: usize = 128;
+const MAX_DEFAULT: u64 = 4096;
+
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches: clap::ArgMatches = uu_app().try_get_matches_from(args)?;
@@ -43,13 +46,19 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
 
     let max_size = if let Some(size_str) = matches.get_one::<String>(options::MAX_SIZE) {
         match Size::parse(size_str) {
-            Ok(size) => Some(size.size_bytes()),
+            Ok(size) => {
+                let mut s = size.size_bytes();
+                if s == 0 {
+                    s = MAX_DEFAULT;
+                }
+                Some(s)
+            }
             Err(_) => {
                 return Err(USimpleError::new(1, "Failed to parse max-size value"));
             }
         }
     } else {
-        None
+        Some(MAX_DEFAULT)
     };
 
     let mut hasher = Md5::new();
@@ -107,7 +116,6 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         hasher.update(&buffer);
     }
 
-    const RANDOM_BYTES: usize = 128;
     let mut rng = rand::rng();
     let mut rand_bytes = [0u8; RANDOM_BYTES];
     rng.fill_bytes(&mut rand_bytes);

From 1a5896c3be4fe2d3aed815ea3ccd7aac67e69da1 Mon Sep 17 00:00:00 2001
From: Alexandra <aspasparagus@gmail.com>
Date: Tue, 8 Apr 2025 20:12:48 +0200
Subject: [PATCH 2/2] mcookie: fix and add tests

---
 tests/by-util/test_mcookie.rs | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/tests/by-util/test_mcookie.rs b/tests/by-util/test_mcookie.rs
index 5260340..a84e73f 100644
--- a/tests/by-util/test_mcookie.rs
+++ b/tests/by-util/test_mcookie.rs
@@ -79,7 +79,7 @@ fn test_char_device_input() {
         .arg("/dev/zero")
         .succeeds();
 
-    res_verbose.stderr_contains("Got 1024 bytes from /dev/zero");
+    res_verbose.stderr_contains("Got 4096 bytes from /dev/zero");
     res_verbose.stderr_contains("Got 128 bytes from randomness source"); // Ensure internal randomness is still added
 
     let stdout_verbose = res_verbose.stdout_str().trim_end();
@@ -177,3 +177,36 @@ fn test_not_existing_file() {
         file2.path().to_str().unwrap()
     ));
 }
+
+#[test]
+fn test_max_size_limits() {
+    let mut file = NamedTempFile::new().unwrap();
+    const CONTENT: [u8; 5500] = [1; 5500];
+    file.write_all(&CONTENT).unwrap();
+
+    let res_default = new_ucmd!()
+        .arg("--verbose")
+        .arg("-f")
+        .arg(file.path())
+        .succeeds();
+
+    // Ensure we only read up to 4096 bytes
+    res_default.stderr_contains(format!(
+        "Got 4096 bytes from {}",
+        file.path().to_str().unwrap()
+    ));
+
+    let res_zero = new_ucmd!()
+        .arg("--verbose")
+        .arg("-f")
+        .arg(file.path())
+        .arg("-m")
+        .arg("0")
+        .succeeds();
+
+    // Ensure we read up 4096 bytes
+    res_zero.stderr_contains(format!(
+        "Got 4096 bytes from {}",
+        file.path().to_str().unwrap()
+    ));
+}