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