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systemd/SOURCES/0668-boot-do-not-truncate-r...

51 lines
2.5 KiB

From 2d6ce79b1d727cd85d3504706da9c2eca6dc72fe Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed, 16 Nov 2022 19:34:53 +0100
Subject: [PATCH] boot: do not truncate random seed file
There are concerns about the FAT file system driver exploding if we try
to do this, so just leave the bytes zeroed out instead.
(cherry picked from commit 5d29d07b342397a8ecc4bea96f53595a03dd94f1)
Related: RHEL-16952
---
src/boot/efi/random-seed.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/src/boot/efi/random-seed.c b/src/boot/efi/random-seed.c
index e11e345e88..471398fbf1 100644
--- a/src/boot/efi/random-seed.c
+++ b/src/boot/efi/random-seed.c
@@ -268,7 +268,7 @@ EFI_STATUS process_random_seed(EFI_FILE *root_dir) {
sha256_finish_ctx(&hash, random_bytes);
size = sizeof(random_bytes);
- /* If the file size is too large, zero out the remaining bytes on disk, and then truncate. */
+ /* If the file size is too large, zero out the remaining bytes on disk. */
if (size < info->FileSize) {
err = handle->SetPosition(handle, size);
if (err != EFI_SUCCESS)
@@ -285,10 +285,17 @@ EFI_STATUS process_random_seed(EFI_FILE *root_dir) {
err = handle->SetPosition(handle, 0);
if (err != EFI_SUCCESS)
return log_error_status_stall(err, L"Failed to seek to beginning of random seed file: %r", err);
- info->FileSize = size;
- err = handle->SetInfo(handle, &GenericFileInfo, info->Size, info);
- if (err != EFI_SUCCESS)
- return log_error_status_stall(err, L"Failed to truncate random seed file: %r", err);
+
+ /* We could truncate the file here with something like:
+ *
+ * info->FileSize = size;
+ * err = handle->SetInfo(handle, &GenericFileInfo, info->Size, info);
+ * if (err != EFI_SUCCESS)
+ * return log_error_status_stall(err, L"Failed to truncate random seed file: %r", err);
+ *
+ * But this is considered slightly risky, because EFI filesystem drivers are a little bit
+ * flimsy. So instead we rely on userspace eventually truncating this when it writes a new
+ * seed. For now the best we do is zero it. */
}
/* Update the random seed on disk before we use it */
wsize = size;