On 4/24/2024 8:56 PM, Eric Biggers wrote:
On Fri, Apr 12, 2024 at 05:55:56PM -0700, Fan Wu wrote:
dm verity: consume root hash digest and expose signature data via LSM hook
As in the fsverity patch, nothing is being "consumed" here. This patch adds a
supplier, not a consumer. I think you mean something like: expose root digest
and signature to LSMs.
Thanks for the suggestion.
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index bb5da66da4c1..fbb83c6fd99c 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -22,6 +22,8 @@
#include <linux/scatterlist.h>
#include <linux/string.h>
#include <linux/jump_label.h>
+#include <linux/security.h>
+#include <linux/dm-verity.h>
#define DM_MSG_PREFIX "verity"
@@ -1017,6 +1019,38 @@ static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
blk_limits_io_min(limits, limits->logical_block_size);
}
+#ifdef CONFIG_SECURITY
+
+static int verity_init_sig(struct dm_verity *v, const void *sig,
+ size_t sig_size)
+{
+ v->sig_size = sig_size;
+ v->root_digest_sig = kmemdup(sig, v->sig_size, GFP_KERNEL);
+ if (!v->root_digest)
+ return -ENOMEM;
root_digest_sig, not root_digest
Thanks for pointing out!
+#ifdef CONFIG_SECURITY
+
+static int verity_finalize(struct dm_target *ti)
+{
+ struct block_device *bdev;
+ struct dm_verity_digest root_digest;
+ struct dm_verity *v;
+ int r;
+
+ v = ti->private;
+ bdev = dm_disk(dm_table_get_md(ti->table))->part0;
+ root_digest.digest = v->root_digest;
+ root_digest.digest_len = v->digest_size;
+ root_digest.alg = v->alg_name;
+
+ r = security_bdev_setintegrity(bdev, LSM_INT_DMVERITY_ROOTHASH, &root_digest,
+ sizeof(root_digest));
+ if (r)
+ return r;
+
+ r = security_bdev_setintegrity(bdev,
+ LSM_INT_DMVERITY_SIG_VALID,
+ v->root_digest_sig,
+ v->sig_size);
The signature is only checked if CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=y, whereas
this code is built whenever CONFIG_SECURITY=y.
So this seems like the same issue that has turned up elsewhere in the IPE
patchset, where IPE is (apparently) happy with any signature, even one that
hasn't been checked...
Yes I do agree the second hook call should better depend on
CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=y.
However, the current implementation does not happy with any signature.
In case of CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=y, any signature
provided to dm-verity will be checked against the configured keyring,
the hook call won't be reached if the check failed. In case of no
signature is provided and !DM_VERITY_IS_SIG_FORCE_ENABLED(), the hook
will be called with signature value NULL.
In case of CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=n, signature won't be
accepted by dm-verity. In addition, the whole support of dm-verity will
be disabled for IPE because CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=n.
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index 20b1bcf03474..89e862f0cdf6 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -43,6 +43,9 @@ struct dm_verity {
u8 *root_digest; /* digest of the root block */
u8 *salt; /* salt: its size is salt_size */
u8 *zero_digest; /* digest for a zero block */
+#ifdef CONFIG_SECURITY
+ u8 *root_digest_sig; /* digest signature of the root block */
+#endif /* CONFIG_SECURITY */
No, it's not a signature of the root block, at least not directly. It's a
signature of the root digest (the digest of the root block).
diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
new file mode 100644
index 000000000000..a799a8043d85
--- /dev/null
+++ b/include/linux/dm-verity.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_DM_VERITY_H
+#define _LINUX_DM_VERITY_H
+
+struct dm_verity_digest {
+ const char *alg;
+ const u8 *digest;
+ size_t digest_len;
+};
+
+#endif /* _LINUX_DM_VERITY_H */
diff --git a/include/linux/security.h b/include/linux/security.h
index ac0985641611..9e46b13a356c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -84,7 +84,8 @@ enum lsm_event {
};
enum lsm_integrity_type {
- __LSM_INT_MAX
+ LSM_INT_DMVERITY_SIG_VALID,
+ LSM_INT_DMVERITY_ROOTHASH,
};
Shouldn't struct dm_verity_digest be defined next to LSM_INT_DMVERITY_ROOTHASH?
It's the struct that's associated with it.
It seems weird to create a brand new header <linux/dm-verity.h> that just
contains this one LSM related definition, when there's already a header for the
LSM definitions that even includes the related value LSM_INT_DMVERITY_ROOTHASH.
- Eric
Yes they can just be in the same header. Thanks for the suggestion.
-Fan
