From b4be1bb21640397429fec036c577106938ffe9a1 Mon Sep 17 00:00:00 2001
From: "Tony Arcieri (iqlusion)" <tony@iqlusion.io>
Date: Wed, 13 Aug 2025 15:36:53 -0600
Subject: [PATCH] mgm: use `TdesEde3::weak_key_test` (#621)

Replaces the vendored weak key test with the upstream one from the `des`
crate which was added in RustCrypto/block-ciphers#465
---
 src/mgm.rs      | 12 +++++----
 src/mgm/tdes.rs | 70 -------------------------------------------------
 2 files changed, 7 insertions(+), 75 deletions(-)
 delete mode 100644 src/mgm/tdes.rs

diff --git a/src/mgm.rs b/src/mgm.rs
index 9740bd2..ee857d0 100644
--- a/src/mgm.rs
+++ b/src/mgm.rs
@@ -70,12 +70,14 @@ pub(crate) const APPLET_NAME: &str = "YubiKey MGMT";
 #[cfg(feature = "untested")]
 pub(crate) const APPLET_ID: &[u8] = &[0xa0, 0x00, 0x00, 0x05, 0x27, 0x47, 0x11, 0x17];
 
-mod tdes;
-pub(crate) use tdes::DES_LEN_3DES;
-use tdes::DES_LEN_DES;
-
 pub(crate) const ADMIN_FLAGS_1_PROTECTED_MGM: u8 = 0x02;
 
+/// Size of a DES key
+pub(super) const DES_LEN_DES: usize = 8;
+
+/// Size of a 3DES key
+pub(crate) const DES_LEN_3DES: usize = DES_LEN_DES * 3;
+
 #[cfg(feature = "untested")]
 const CB_ADMIN_SALT: usize = 16;
 
@@ -172,7 +174,7 @@ impl MgmKey {
     ///
     /// Returns an error if the key is weak.
     pub fn new(key_bytes: [u8; DES_LEN_3DES]) -> Result<Self> {
-        if tdes::is_weak_key(&key_bytes) {
+        if TdesEde3::weak_key_test(key_bytes.as_ref()).is_err() {
             error!(
                 "blacklisting key '{:?}' since it's weak (with odd parity)",
                 &key_bytes
diff --git a/src/mgm/tdes.rs b/src/mgm/tdes.rs
deleted file mode 100644
index ba1105b..0000000
--- a/src/mgm/tdes.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-use zeroize::Zeroizing;
-
-/// Size of a DES key
-pub(super) const DES_LEN_DES: usize = 8;
-
-/// Size of a 3DES key
-pub(crate) const DES_LEN_3DES: usize = DES_LEN_DES * 3;
-
-/// Weak and semi weak DES keys as taken from:
-/// %A D.W. Davies
-/// %A W.L. Price
-/// %T Security for Computer Networks
-/// %I John Wiley & Sons
-/// %D 1984
-const WEAK_DES_KEYS: &[[u8; DES_LEN_DES]] = &[
-    // weak keys
-    [0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01],
-    [0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE],
-    [0x1F, 0x1F, 0x1F, 0x1F, 0x0E, 0x0E, 0x0E, 0x0E],
-    [0xE0, 0xE0, 0xE0, 0xE0, 0xF1, 0xF1, 0xF1, 0xF1],
-    // semi-weak keys
-    [0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE],
-    [0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01],
-    [0x1F, 0xE0, 0x1F, 0xE0, 0x0E, 0xF1, 0x0E, 0xF1],
-    [0xE0, 0x1F, 0xE0, 0x1F, 0xF1, 0x0E, 0xF1, 0x0E],
-    [0x01, 0xE0, 0x01, 0xE0, 0x01, 0xF1, 0x01, 0xF1],
-    [0xE0, 0x01, 0xE0, 0x01, 0xF1, 0x01, 0xF1, 0x01],
-    [0x1F, 0xFE, 0x1F, 0xFE, 0x0E, 0xFE, 0x0E, 0xFE],
-    [0xFE, 0x1F, 0xFE, 0x1F, 0xFE, 0x0E, 0xFE, 0x0E],
-    [0x01, 0x1F, 0x01, 0x1F, 0x01, 0x0E, 0x01, 0x0E],
-    [0x1F, 0x01, 0x1F, 0x01, 0x0E, 0x01, 0x0E, 0x01],
-    [0xE0, 0xFE, 0xE0, 0xFE, 0xF1, 0xFE, 0xF1, 0xFE],
-    [0xFE, 0xE0, 0xFE, 0xE0, 0xFE, 0xF1, 0xFE, 0xF1],
-];
-
-/// Is this 3DES key weak?
-///
-/// This check is performed automatically when the key is instantiated to
-/// ensure no such keys are used.
-pub(super) fn is_weak_key(key: &[u8; DES_LEN_3DES]) -> bool {
-    // set odd parity of key
-    let mut tmp = Zeroizing::new([0u8; DES_LEN_3DES]);
-
-    for i in 0..DES_LEN_3DES {
-        // count number of set bits in byte, excluding the low-order bit - SWAR method
-        let mut c = key[i] & 0xFE;
-
-        c = (c & 0x55) + ((c >> 1) & 0x55);
-        c = (c & 0x33) + ((c >> 2) & 0x33);
-        c = (c & 0x0F) + ((c >> 4) & 0x0F);
-
-        // if count is even, set low key bit to 1, otherwise 0
-        tmp[i] = (key[i] & 0xFE) | u8::from(c & 0x01 != 0x01);
-    }
-
-    // check odd parity key against table by DES key block
-    let mut is_weak = false;
-
-    for weak_key in WEAK_DES_KEYS.iter() {
-        if weak_key == &tmp[0..DES_LEN_DES]
-            || weak_key == &tmp[DES_LEN_DES..2 * DES_LEN_DES]
-            || weak_key == &tmp[2 * DES_LEN_DES..3 * DES_LEN_DES]
-        {
-            is_weak = true;
-            break;
-        }
-    }
-
-    is_weak
-}