[crypto] Re-mask AES-GCM keys #27647
Open
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
3e46299 to
e04ff10
Compare
johannheyszl
approved these changes
Jul 21, 2025
| HARDENED_TRY(hardened_xor((uint32_t *)internal_ctx->key.key_shares[1], mask, | ||
| internal_ctx->key.key_len)); | ||
| } else { | ||
| HARDENED_CHECK_EQ(internal_ctx->key.sideload, kHardenedBoolTrue); |
There was a problem hiding this comment.
Shall we return error upon calling remask with a sideload key to notify user?
sideloaded keys are always remasked on every power cycle iiuc
There was a problem hiding this comment.
gcm_remask_key() cannot be called by the user - it is only called by the CL internally in otcrypto_aes_gcm_update_encrypted_data, otcrypto_aes_gcm_decrypt_final, or otcrypto_aes_gcm_encrypt_final.
In this case, I think just returning OTCRYPTO_OK for this function in the sideloaded key case should be fine.
sw/device/lib/crypto/impl/aes_gcm.c
Outdated
| @@ -427,6 +455,8 @@ otcrypto_status_t otcrypto_aes_gcm_update_encrypted_data( | |||
| aes_gcm_context_t internal_ctx; | |||
| gcm_context_restore(ctx, &internal_ctx); | |||
| HARDENED_TRY(load_key_if_sideloaded(internal_ctx.key)); | |||
| // Remask the key if needed. | |||
There was a problem hiding this comment.
if needed refers to whether not sideloaded, right? we could say this explicitly
There was a problem hiding this comment.
Thanks, good point. I've updated the comment.
e04ff10 to
8ffb16e
Compare
nasahlpa
commented
Jul 22, 2025
As this function is useful also outside of keyblob, so move it to the hardened_memory library. Signed-off-by: Pascal Nasahl <nasahlpa@lowrisc.org>
8ffb16e to
6dd1b96
Compare
As suggested in lowRISC#27243, this commit regularly remasks the key that is used for AES-GCM. Signed-off-by: Pascal Nasahl <nasahlpa@lowrisc.org>
6dd1b96 to
7251046
Compare
moidx
approved these changes
Jul 25, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
As suggested in #27243, this commit regularly remasks the key that is used for AES-GCM.