sw-emulator: Limit HMAC KV access to 48 bytes

Signed-off-by: Arthur Heymans <arthur.heymans@9elements.com>
chipsalliance · Nov 19, 2024 · 78571d9 · 78571d9
1 parent 08a1740
commit 78571d9
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Showing 2 changed files with 7 additions and 4 deletions.
diff --git a/drivers/src/hmac.rs b/drivers/src/hmac.rs
@@ -166,7 +166,7 @@ impl Hmac {
 
         // Configure the hardware so that the output tag is stored at a location specified by the
         // caller.
-        if matches!(&mut tag, HmacTag::Array4x12(_)) {
+        if matches!(&mut tag, HmacTag::Array4x12(_) | HmacTag::Array4x16(_)) {
             KvAccess::begin_copy_to_arr(hmac.hmac512_kv_wr_status(), hmac.hmac512_kv_wr_ctrl())?;
         }
 

diff --git a/sw-emulator/lib/periph/src/hmac.rs b/sw-emulator/lib/periph/src/hmac.rs
@@ -91,6 +91,9 @@ register_bitfields! [
 /// HMAC384 Key Size.
 const HMAC_KEY_SIZE_384: usize = 48;
 
+/// TODO MAX KV KEY SIZE (needs KV supporting 64 bytes?)
+const MAX_KV_KEY_SIZE: usize = 48;
+
 /// HMAC512 Key Size.
 const HMAC_KEY_SIZE_512: usize = 64;
 
@@ -562,10 +565,10 @@ impl HmacSha {
 
         if let Some(key) = &key {
             self.key_from_kv = true;
-            let key_len = self.key_len();
+            let key_len = self.key_len().min(MAX_KV_KEY_SIZE);
             self.key[..key_len]
                 .as_bytes_mut()
-                .copy_from_slice(&key[..key_len * 4]);
+                .copy_from_slice(&key[..key_len]);
         }
 
         self.key_read_status.reg.modify(
@@ -641,7 +644,7 @@ impl HmacSha {
             .key_vault
             .write_key(
                 key_id,
-                &self.tag.as_bytes()[..self.key_len() * 4],
+                &self.tag.as_bytes()[..MAX_KV_KEY_SIZE],
                 self.tag_write_ctrl.reg.read(TagWriteControl::USAGE),
             )
             .err()