aacs/types: redact Debug for all key-bearing types (test-guarded)

DeviceKey/HostCert/Vid/MediaKey/Vuk/ProcessingKey/UnitKey/DiscEntry carried key
material on #[derive(Debug)] — a stray {:?} would leak device/host-private/media/
volume/unit keys. Manual Debug impls print shape only. redaction_tests asserts no
key bytes appear and a redaction marker is present (fails if a derive returns).

src/aacs/types.rs

@@ -6,7 +6,7 @@
 //! owns only the crypto and these value types that flow through it.
 
 /// A device key for MKB subset-difference tree processing.
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct DeviceKey {
     pub key: [u8; 16],
     pub node: u16,
@@ -15,7 +15,7 @@ pub struct DeviceKey {
 }
 
 /// Host certificate + private key for AACS SCSI authentication.
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct HostCert {
     /// AACS 1.0: 20 bytes. AACS 2.0: 32 bytes.
     pub private_key: [u8; 20],
@@ -28,22 +28,22 @@ pub struct HostCert {
 }
 
 /// Volume ID (16 bytes) — read from the disc via the SCSI handshake / OEM path.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Vid(pub [u8; 16]);
 
 /// Media Key (Km, 16 bytes) — the MKB-scoped key derived from device keys.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct MediaKey(pub [u8; 16]);
 
 /// Volume Unique Key (VUK / Kvu, 16 bytes) — derived from `MediaKey` + `Vid`,
 /// decrypts the per-disc encrypted title keys in `Unit_Key_RO.inf`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Vuk(pub [u8; 16]);
 
 /// Processing Key (Kp, 16 bytes) — an MKB Subset-Difference key that yields the
 /// Media Key. A leaked/precomputed PK in the keydb, or the intermediate PK a
 /// device-key walk derives at its matching SD node.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct ProcessingKey(pub [u8; 16]);
 
 /// One decrypted per-CPS-unit AACS title key.
@@ -53,7 +53,7 @@ pub struct ProcessingKey(pub [u8; 16]);
 /// area). The CPS-unit *number* association is a higher-level concern owned by
 /// [`super::inf::parse_unit_key_ro`], which pairs each positional key with its
 /// declared CPS unit; this primitive only does the AES, so it surfaces position.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct UnitKey {
     pub idx: u32,
     pub key: [u8; 16],
@@ -95,7 +95,7 @@ impl UnitKey {
 }
 
 /// A per-disc entry from the key database.
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct DiscEntry {
     /// Disc hash (20 bytes, hex)
     pub disc_hash: String,
@@ -110,3 +110,158 @@ pub struct DiscEntry {
     /// Unit keys (title keys) indexed by CPS unit number
     pub unit_keys: Vec<(u32, [u8; 16])>,
 }
+
+// ── Redacting `Debug` impls ──────────────────────────────────────────────────
+//
+// Every type above carries AACS secret material (device keys, host PRIVATE keys,
+// media/volume/processing/unit keys). `#[derive(Debug)]` would print those bytes
+// verbatim, so a stray `debug!("{:?}", …)` or a panic message would leak the
+// keys. These hand-written impls print only NON-secret shape (presence, lengths,
+// tree coordinates, indices) — never key bytes. `decrypt::DecryptKeys` follows
+// the same policy by omitting `Debug` entirely; here we keep `Debug` because
+// these are `PartialEq`/`Eq` value types used in `assert_eq!` and nested inside
+// other `#[derive(Debug)]` structs, so the trait must exist — just not leak.
+// Guarded by `redaction_tests` below.
+
+impl std::fmt::Debug for DeviceKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("DeviceKey")
+            .field("key", &"<redacted>")
+            .field("node", &self.node)
+            .field("uv", &self.uv)
+            .field("u_mask_shift", &self.u_mask_shift)
+            .finish()
+    }
+}
+
+impl std::fmt::Debug for HostCert {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("HostCert")
+            .field("private_key", &"<redacted>")
+            .field("certificate_len", &self.certificate.len())
+            .field("private_key_v2", &self.private_key_v2.map(|_| "<redacted>"))
+            .field(
+                "certificate_v2_len",
+                &self.certificate_v2.as_ref().map(|c| c.len()),
+            )
+            .finish()
+    }
+}
+
+impl std::fmt::Debug for Vid {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("Vid(<redacted>)")
+    }
+}
+
+impl std::fmt::Debug for MediaKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("MediaKey(<redacted>)")
+    }
+}
+
+impl std::fmt::Debug for Vuk {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("Vuk(<redacted>)")
+    }
+}
+
+impl std::fmt::Debug for ProcessingKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("ProcessingKey(<redacted>)")
+    }
+}
+
+impl std::fmt::Debug for UnitKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("UnitKey")
+            .field("idx", &self.idx)
+            .field("key", &"<redacted>")
+            .field("index_number", &self.index_number)
+            .finish()
+    }
+}
+
+impl std::fmt::Debug for DiscEntry {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("DiscEntry")
+            .field("disc_hash", &self.disc_hash)
+            .field("title", &self.title)
+            .field("media_key", &self.media_key.map(|_| "<redacted>"))
+            .field("disc_id", &self.disc_id.map(|_| "<redacted>"))
+            .field("vuk", &self.vuk.map(|_| "<redacted>"))
+            .field("unit_keys_len", &self.unit_keys.len())
+            .finish()
+    }
+}
+
+#[cfg(test)]
+mod redaction_tests {
+    use super::*;
+
+    // Sentinel key byte 0xD5 = decimal 213. A derived `Debug` prints `[u8;N]`
+    // as decimal, so a leaked key surfaces the substring "213"; the redacting
+    // impls must not. No non-secret field below is 213, so "213" appearing means
+    // key bytes leaked. Each type must also carry a "redacted" marker (or omit
+    // the secret entirely) so re-adding `#[derive(Debug)]` fails this test.
+    const S: u8 = 0xD5;
+
+    fn assert_redacted(what: &str, dbg: &str) {
+        assert!(
+            !dbg.contains("213"),
+            "{what}: Debug leaked key bytes (found decimal 213): {dbg}"
+        );
+        assert!(
+            dbg.contains("redacted"),
+            "{what}: Debug missing redaction marker: {dbg}"
+        );
+    }
+
+    #[test]
+    fn device_key_debug_is_redacted() {
+        let d = DeviceKey {
+            key: [S; 16],
+            node: 1,
+            uv: 2,
+            u_mask_shift: 3,
+        };
+        assert_redacted("DeviceKey", &format!("{d:?}"));
+    }
+
+    #[test]
+    fn host_cert_debug_is_redacted() {
+        let h = HostCert {
+            private_key: [S; 20],
+            certificate: vec![0u8; 92],
+            private_key_v2: Some([S; 32]),
+            certificate_v2: None,
+        };
+        assert_redacted("HostCert", &format!("{h:?}"));
+    }
+
+    #[test]
+    fn newtype_keys_debug_is_redacted() {
+        assert_redacted("Vid", &format!("{:?}", Vid([S; 16])));
+        assert_redacted("MediaKey", &format!("{:?}", MediaKey([S; 16])));
+        assert_redacted("Vuk", &format!("{:?}", Vuk([S; 16])));
+        assert_redacted("ProcessingKey", &format!("{:?}", ProcessingKey([S; 16])));
+    }
+
+    #[test]
+    fn unit_key_debug_is_redacted() {
+        assert_redacted("UnitKey", &format!("{:?}", UnitKey::new(0, [S; 16])));
+    }
+
+    #[test]
+    fn disc_entry_debug_is_redacted() {
+        let e = DiscEntry {
+            disc_hash: "0xAA".into(),
+            title: "T".into(),
+            media_key: Some([S; 16]),
+            disc_id: Some([S; 16]),
+            vuk: Some([S; 16]),
+            unit_keys: vec![(1, [S; 16])],
+        };
+        assert_redacted("DiscEntry", &format!("{e:?}"));
+    }
+}