ot_keymgr: Add property to disable flash seed check

docs/opentitan/earlgrey.md

@@ -206,6 +206,10 @@ There are two modes to handle address remapping, with different limitations:
   whenever possible. To enable this legacy mode, set the `alias-mode` property to true:
   `-global ot-ibex_wrapper.alias-mode=true`
 
+### Keymgr
+
+See documentation in [`keymgr.md`](./keymgr.md).
+
 ### OTBN
 
 * `-global ot-otbn.logfile=<filename>` output OTBN execution message to the specified logfile. When

docs/opentitan/keymgr.md

@@ -0,0 +1,14 @@
+# OpenTitan Key Manager support
+
+## Properties
+
+- `-global ot-keymgr.disable-flash-seed-check=true` can be used to disable the
+data validity check in the Keymgr for loaded flash secrets (the owner and
+creator seed). This validity check ensures that the loaded key is not all-zero
+or all-one (and thus probably uninitialized). When emulating OpenTitan, it may
+be useful to be able to advance using uninitialized keys due to a lack of flash
+info splicing, to bypass the need to run through an entire provisioning flow.
+  - Note also that the fatal Keymgr alert caused by failing this check should
+  not appear for unprovisioned flash if flash scrambling is implemented (and
+  enabled). This is because the garbage unscrambled data that is read will not
+  pass this check.

hw/opentitan/ot_keymgr.c

@@ -457,6 +457,7 @@ typedef struct OtKeyMgrState {
     DeviceState *key_sinks[KEYMGR_KEY_SINK_COUNT];
     char *seed_xstrs[KEYMGR_SEED_COUNT];
     bool use_default_entropy_seed; /* flag to seed PRNG with default seed */
+    bool disable_flash_seed_check; /* disable all-0/1 check for flash seeds */
 } OtKeyMgrState;
 
 struct OtKeyMgrClass {
@@ -1095,6 +1096,18 @@ ot_keymgr_kdf_append_flash_seed(OtKeyMgrState *s, OtFlashKeyMgrSecretType type,
     ot_keymgr_kdf_push_bytes(s, seed.secret, OT_FLASH_KEYMGR_SECRET_BYTES);
     bool data_valid =
         ot_keymgr_valid_data_check(seed.secret, OT_FLASH_KEYMGR_SECRET_BYTES);
+
+    /*
+     * Unprovisioned flash will not contain valid secrets, and will return all
+     * 1s (failing the validity check) if scrambling/ECCs are disabled. Using
+     * the `disable-flash-seed-check` property allows you to optionally bypass
+     * these errors for unprovisioned environments where flash info page
+     * splicing is not available.
+     */
+    if (!data_valid && s->disable_flash_seed_check) {
+        trace_ot_keymgr_bypass_failure(s->ot_id, seed_name);
+        data_valid = true;
+    }
     if (!seed.valid || !data_valid) {
         s->regs[R_DEBUG] |= debug_mask;
         s->op_state.valid_inputs = false;
@@ -2351,6 +2364,8 @@ static Property ot_keymgr_properties[] = {
                        seed_xstrs[KEYMGR_SEED_NONE]),
     DEFINE_PROP_BOOL("use-default-entropy-seed", OtKeyMgrState,
                      use_default_entropy_seed, false),
+    DEFINE_PROP_BOOL("disable-flash-seed-check", OtKeyMgrState,
+                     disable_flash_seed_check, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 

hw/opentitan/trace-events

@@ -280,6 +280,7 @@ ot_ibex_wrapper_update_exec(const char *id, uint32_t bm, bool esc_rx, bool halte
 
 # ot_keymgr.c
 ot_keymgr_advance(const char *id, const char *stage, int nstage, const char *cdi, int ncdi) "%s: [%s:%d], [%s:%d]"
+ot_keymgr_bypass_failure(const char *id, const char *what) "%s: bypass failure for %s due to enabled properties"
 ot_keymgr_change_main_fsm_state(const char *id, int line, const char *old, int nold, const char *new, int nnew) "%s: @ %d [%s:%d] -> [%s:%d]"
 ot_keymgr_change_op_status(const char *id, int line, const char *old, int nold, const char *new, int nnew) "%s: @ %d [%s:%d] -> [%s:%d]"
 ot_keymgr_change_working_state(const char *id, int line, const char *old, int nold, const char *new, int nnew) "%s: @ %d [%s:%d] -> [%s:%d]"