[Cryptech-Commits] [sw/libhal] branch master updated: Release keystore lock before unwrapping key.

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sra at hactrn.net pushed a commit to branch master
in repository sw/libhal.

The following commit(s) were added to refs/heads/master by this push:
     new a5b4842  Release keystore lock before unwrapping key.
a5b4842 is described below

commit a5b4842f95ea501dacb1ed828c924f372d3f1262
Author: Rob Austein <sra at hactrn.net>
AuthorDate: Sat May 19 22:18:56 2018 -0400

    Release keystore lock before unwrapping key.
    
    hal_ks_fetch() was written as lock-at-the-top, unlock-at-the-bottom to
    keep it as simple as possible, but this turns out to have bad
    performance implications when unwrapping the key is slow.  So now we
    grab the wrapped key, release the lock, then unwrap, which should be
    safe enough given that hal_ks_fetch() is read-only.  This lets us make
    better use of multiple AES cores to unwrap in parallel when we have
    multiple active clients.
---
 ks.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/ks.c b/ks.c
index 1598679..f4015e0 100644
--- a/ks.c
+++ b/ks.c
@@ -623,16 +623,17 @@ hal_error_t hal_ks_fetch(hal_ks_t *ks,
   if ((err = hal_ks_index_find(ks, &slot->name, &b, &slot->hint))         != HAL_OK ||
       (err = hal_ks_block_test_owner(ks, b, slot->client, slot->session)) != HAL_OK ||
       (err = hal_ks_block_read_cached(ks, b, &block))                     != HAL_OK)
-    goto done;
+    goto unlock;
 
   if (hal_ks_block_get_type(block) != HAL_KS_BLOCK_TYPE_KEY) {
     err = HAL_ERROR_KEYSTORE_WRONG_BLOCK_TYPE; /* HAL_ERROR_KEY_NOT_FOUND */
-    goto done;
+    goto unlock;
   }
 
   hal_ks_cache_mark_used(ks, block, b);
 
   hal_ks_key_block_t *k = &block->key;
+  const size_t k_der_len = k->der_len;
 
   slot->type  = k->type;
   slot->curve = k->curve;
@@ -641,6 +642,15 @@ hal_error_t hal_ks_fetch(hal_ks_t *ks,
   if (der == NULL && der_len != NULL)
     *der_len = k->der_len;
 
+  if (der != NULL && k_der_len <= der_max)
+    memcpy(der, k->der, k_der_len);
+
+ unlock:
+  hal_ks_unlock();
+
+  if (err != HAL_OK)
+    return err;
+
   if (der != NULL) {
 
     uint8_t kek[KEK_LENGTH];
@@ -653,13 +663,11 @@ hal_error_t hal_ks_fetch(hal_ks_t *ks,
     *der_len = der_max;
 
     if ((err = hal_mkm_get_kek(kek, &kek_len, sizeof(kek))) == HAL_OK)
-      err = hal_aes_keyunwrap(NULL, kek, kek_len, k->der, k->der_len, der, der_len);
+      err = hal_aes_keyunwrap(NULL, kek, kek_len, der, k_der_len, der, der_len);
 
     memset(kek, 0, sizeof(kek));
   }
 
- done:
-  hal_ks_unlock();
   return err;
 }
 

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