From: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Date: Tue, 17 Sep 2024 08:49:29 +0000 (+0200)
Subject: efi_leader: delete rng-seed if having EFI RNG protocol
X-Git-Url: http://git.dujemihanovic.xyz/html/%7B%7B%20%28.OutputFormats.Get?a=commitdiff_plain;h=b03b2a45f9f07bdfb0074adf9c8b4339080a7def;p=u-boot.git

efi_leader: delete rng-seed if having EFI RNG protocol

For measured be boot we must avoid any volatile values in the device-tree.
We already delete /chosen/kaslr-seed if we provide and EFI RNG protocol.

Additionally remove /chosen/rng-seed provided by QEMU or U-Boot.

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
---

diff --git a/include/efi_loader.h b/include/efi_loader.h
index f84852e384..511281e150 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -567,7 +567,7 @@ efi_status_t EFIAPI efi_convert_pointer(efi_uintn_t debug_disposition,
 /* Carve out DT reserved memory ranges */
 void efi_carve_out_dt_rsv(void *fdt);
 /* Purge unused kaslr-seed */
-void efi_try_purge_kaslr_seed(void *fdt);
+void efi_try_purge_rng_seed(void *fdt);
 /* Called by bootefi to make console interface available */
 efi_status_t efi_console_register(void);
 /* Called by efi_init_obj_list() to proble all block devices */
diff --git a/lib/efi_loader/efi_dt_fixup.c b/lib/efi_loader/efi_dt_fixup.c
index 9d017804ee..0dac94b0c6 100644
--- a/lib/efi_loader/efi_dt_fixup.c
+++ b/lib/efi_loader/efi_dt_fixup.c
@@ -41,7 +41,7 @@ static void efi_reserve_memory(u64 addr, u64 size, bool nomap)
 }
 
 /**
- * efi_try_purge_kaslr_seed() - Remove unused kaslr-seed
+ * efi_try_purge_rng_seed() - Remove unused kaslr-seed, rng-seed
  *
  * Kernel's EFI STUB only relies on EFI_RNG_PROTOCOL for randomization
  * and completely ignores the kaslr-seed for its own randomness needs
@@ -51,8 +51,9 @@ static void efi_reserve_memory(u64 addr, u64 size, bool nomap)
  *
  * @fdt: Pointer to device tree
  */
-void efi_try_purge_kaslr_seed(void *fdt)
+void efi_try_purge_rng_seed(void *fdt)
 {
+	const char * const prop[] = {"kaslr-seed", "rng-seed"};
 	const efi_guid_t efi_guid_rng_protocol = EFI_RNG_PROTOCOL_GUID;
 	struct efi_handler *handler;
 	efi_status_t ret;
@@ -67,9 +68,13 @@ void efi_try_purge_kaslr_seed(void *fdt)
 	if (nodeoff < 0)
 		return;
 
-	err = fdt_delprop(fdt, nodeoff, "kaslr-seed");
-	if (err < 0 && err != -FDT_ERR_NOTFOUND)
-		log_err("Error deleting kaslr-seed\n");
+	for (size_t i = 0; i < ARRAY_SIZE(prop); ++i) {
+		err = fdt_delprop(fdt, nodeoff, prop[i]);
+		if (err < 0 && err != -FDT_ERR_NOTFOUND)
+			log_err("Error deleting %s\n", prop[i]);
+		else
+			log_debug("Deleted /chosen/%s\n", prop[i]);
+	}
 }
 
 /**
diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
index 96f847652e..a481eb4b7e 100644
--- a/lib/efi_loader/efi_helper.c
+++ b/lib/efi_loader/efi_helper.c
@@ -522,7 +522,7 @@ efi_status_t efi_install_fdt(void *fdt)
 	/* Create memory reservations as indicated by the device tree */
 	efi_carve_out_dt_rsv(fdt);
 
-	efi_try_purge_kaslr_seed(fdt);
+	efi_try_purge_rng_seed(fdt);
 
 	if (CONFIG_IS_ENABLED(EFI_TCG2_PROTOCOL_MEASURE_DTB)) {
 		ret = efi_tcg2_measure_dtb(fdt);