On 1/12/24 09:06, Mimi Zohar wrote:
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..bf758fd5062c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -734,6 +734,14 @@ static int kexec_calculate_store_digests(struct kimage *image)
if (ksegment->kbuf == pi->purgatory_buf)
continue;
+ /*
+ * Skip the segment if ima_segment_index is set and matches
+ * the current index
+ */
+ if (image->is_ima_segment_index_set &&
+ i == image->ima_segment_index)
+ continue;
With this change, the IMA segment is not included in the digest
calculation, nor should it be included in the digest verification.
However, I'm not seeing the matching code change in the digest
verification.
Fair question.
But I don't think anything else needs to be done here.
The way kexec_calculate_store_digests() and verify_sha256_digest()
are implemented, it already skips verification of the segments if
the segment is not part of 'purgatory_sha_regions'.
In kexec_calculate_store_digests(), my change is to 'continue' when the
segment is the IMA segment when the function is going through all the
segments in a for loop [1].
Therefore in kexec_calculate_store_digests() -
- crypto_shash_update() is not called for IMA segment [1].
- sha_regions[j] is not updated with IMA segment [1].
- This 'sha_regions' variable later becomes 'purgatory_sha_regions'
in kexec_calculate_store_digests [1].
- and verify_sha256_digest() only verifies 'purgatory_sha_regions'[2].
Since IMA segment is not part of the 'purgatory_sha_regions', it is
not included in the verification as part of verify_sha256_digest().
Please make ignoring the IMA segment a separate patch.
Sure. Will do.
Thank you for the explanation. Please include in the patch description a
statement about the "sha_regions" not including the IMA segment, so nothing is
needed on the verify side.
Definitely. Will do.
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