Re: [RFC PATCH v5 06/11] dm-verity: move signature check after tree validation

The CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG introduced by Jaskaran was intended to be used to allow an LSM to enforce verifications for all dm-verity volumes. However, with it's current implementation, this signature verification occurs after the merkel-tree is validated, as a result the signature can pass initial verification by passing a matching root-hash and signature. This results in an unreadable block_device, but that has passed signature validation (and subsequently, would be marked as verified). This change moves the signature verification to after the merkel-tree has finished validation. Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- drivers/md/dm-verity-target.c | 44 ++++------ drivers/md/dm-verity-verify-sig.c | 140 ++++++++++++++++++++++-------- drivers/md/dm-verity-verify-sig.h | 24 +++-- drivers/md/dm-verity.h | 2 +- 4 files changed, 134 insertions(+), 76 deletions(-) diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index eec9f252e935..fabc173aa7b3 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -471,9 +471,9 @@ static int verity_verify_io(struct dm_verity_io *io) struct bvec_iter start; unsigned b; struct crypto_wait wait; + int r; for (b = 0; b < io->n_blocks; b++) { - int r; sector_t cur_block = io->block + b; struct ahash_request *req = verity_io_hash_req(v, io); @@ -530,6 +530,16 @@ static int verity_verify_io(struct dm_verity_io *io) return -EIO; } + /* + * At this point, the merkel tree has finished validating. + * if signature was specified, validate the signature here. + */ + r = verity_verify_root_hash(v); + if (r < 0) { + DMERR_LIMIT("signature mismatch"); + return r; + } + return 0; }