From 952a5c502e032c01591d5bafd6489e482937dc24 Mon Sep 17 00:00:00 2001
From: Javan <javan_dhein@outlook.com>
Date: Fri, 11 Sep 2026 12:03:37 -0300
Subject: [PATCH] uucore: reject over-length BLAKE2b digests when checking

When verifying a checksum file, the BLAKE2b output length was inferred
from the digest found in the file and handed to the hasher unchecked. A
digest longer than the 64 bytes BLAKE2b maximum made blake2b_simd fail
its own length assertion and abort the process, instead of the line
being reported as malformed.

Route that inferred length through parse_blake_length, like the --length
and tagged-line paths already do, and treat a rejected length as an
improperly formatted line. This matches GNU, which skips such a line and
exits 1 with "no properly formatted checksum lines found".

HashLength::from_bytes loses its last caller with this change, so drop
it.

Fixes #14487
---
 src/uucore/src/lib/features/checksum/mod.rs      |  6 ------
 src/uucore/src/lib/features/checksum/validate.rs |  7 ++++++-
 tests/by-util/test_cksum.rs                      | 14 ++++++++++++++
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/uucore/src/lib/features/checksum/mod.rs b/src/uucore/src/lib/features/checksum/mod.rs
index 40c5bb421f9..36df7c5bc8c 100644
--- a/src/uucore/src/lib/features/checksum/mod.rs
+++ b/src/uucore/src/lib/features/checksum/mod.rs
@@ -260,12 +260,6 @@ pub struct HashLength {
 }
 
 impl HashLength {
-    #[must_use]
-    #[inline]
-    pub(crate) fn from_bytes(n: usize) -> Self {
-        Self { bit_len: n * 8 }
-    }
-
     #[must_use]
     #[inline]
     pub fn from_bits(n: usize) -> Self {
diff --git a/src/uucore/src/lib/features/checksum/validate.rs b/src/uucore/src/lib/features/checksum/validate.rs
index 50465fbb415..f53c756d75f 100644
--- a/src/uucore/src/lib/features/checksum/validate.rs
+++ b/src/uucore/src/lib/features/checksum/validate.rs
@@ -791,7 +791,12 @@ fn process_non_algo_based_line(
     // bits except when dealing with blake2b, sha2 and sha3, where we will
     // detect the length.
     let algo_len = match cli_algo_kind {
-        ak::Blake2b | ak::Blake3 => Some(HashLength::from_bytes(expected_checksum.len())),
+        // An over-length digest makes this a malformed line for GNU, not a
+        // fatal error.
+        algo @ (ak::Blake2b | ak::Blake3) => Some(
+            parse_blake_length(algo, BlakeLength::Int(expected_checksum.len() * 8))
+                .map_err(|_| LineCheckError::ImproperlyFormatted)?,
+        ),
         ak::Sha2 | ak::Sha3 => {
             // multiplication by 8 to get the number of bits
             Some(
diff --git a/tests/by-util/test_cksum.rs b/tests/by-util/test_cksum.rs
index 241777f289f..ec77c77e822 100644
--- a/tests/by-util/test_cksum.rs
+++ b/tests/by-util/test_cksum.rs
@@ -1676,6 +1676,20 @@ fn test_md5_bits() {
         .stderr_contains("f: no properly formatted checksum lines found");
 }
 
+#[test]
+fn test_blake2b_check_digest_too_long() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    // The referenced file must exist: the digest length is only used once the
+    // line is accepted and the file is about to be hashed.
+    at.write("f1", "content\n");
+    // 65 bytes, above the 64 bytes BLAKE2b maximum.
+    at.write("sums", &format!("{}  f1\n", "a".repeat(130)));
+
+    ucmd.args(&["-a", "blake2b", "-c", "sums"])
+        .fails_with_code(1)
+        .stderr_contains("sums: no properly formatted checksum lines found");
+}
+
 #[test]
 fn test_blake2b_bits() {
     let (at, mut ucmd) = at_and_ucmd!();