Initial implementations of ks_get_kek(). Untested, and none of these

are secure (the one in ks_flash.c is a stub, and the others are for
cases where we have no secure hardware in which to store the KEK).

These are primarily for testing, since in the long run the entire
software implementation of AES-keywrap will be replaced by Verilog
which never lets software see the unwrapped key.  Or so says current
theory.  For the moment, we just need something that will let us test
the rest of the RPC and keystore mechanisms.

1 files changed, 36 insertions, 0 deletions

diff --git a/ks_volatile.c b/ks_volatile.c
index 2381f4c..b71e27e 100644
--- a/ks_volatile.c
+++ b/ks_volatile.c
@@ -55,6 +55,17 @@
 
 static hal_ks_keydb_t db[1];
 
+/*
+ * There's no good place to store the master key (KEK) in this volatile memory implementation.
+ * We might be able to add a bit of protection doing things like using locked physical memory,
+ * as gpg does, or obfuscating the KEK a bit to make it harder to pull out of a crash dump,
+ * but, really, there's not a lot we can do against a determined opponant in this case.
+ *
+ * For now, we just go through the motions.
+ */
+
+static uint8_t kekbuf[bitsToBytes(256)];
+
 const hal_ks_keydb_t *hal_ks_get_keydb(void)
 {
   return db;
@@ -99,6 +110,31 @@ hal_error_t hal_ks_set_pin(const hal_user_t user,
   return HAL_OK;
 }
 
+hal_error_t hal_ks_get_kek(uint8_t *kek,
+                           size_t *kek_len,
+                           const size_t kek_max)
+{
+  if (kek == NULL || kek_len == NULL || kek_max < bitsToBytes(128))
+    return HAL_ERROR_BAD_ARGUMENTS;
+
+  hal_error_t err;
+
+  const size_t len = ((kek_max < bitsToBytes(192)) ? bitsToBytes(128) :
+                      (kek_max < bitsToBytes(256)) ? bitsToBytes(192) :
+                      bitsToBytes(256));
+
+  uint8_t t = 0;
+
+  for (int i = 0; i < sizeof(kekbuf); i++)
+    t |= kekbuf[i];
+
+  if (t == 0 && (err = hal_rpc_get_random(kekbuf, sizeof(kekbuf))) != HAL_OK)
+    return err;
+
+  memcpy(kek, kekbuf, len);
+  return HAL_OK;
+}
+
 /*
  * Local variables:
  * indent-tabs-mode: nil