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authorMickaël Salaün <mic@linux.microsoft.com>2020-10-23 19:05:12 +0200
committerMike Snitzer <snitzer@redhat.com>2020-12-04 18:04:35 -0500
commit4da8f8c8a1e07ad18f057f4044ad96f4135dc877 (patch)
tree99247a48d846727f3288051098cf927be70f55a1
parent985eabdcfe3aad1aea6fc195dafff503f303aa3a (diff)
dm verity: Add support for signature verification with 2nd keyring
Add a new configuration DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING to enable dm-verity signatures to be verified against the secondary trusted keyring. Instead of relying on the builtin trusted keyring (with hard-coded certificates), the second trusted keyring can include certificate authorities from the builtin trusted keyring and child certificates loaded at run time. Using the secondary trusted keyring enables to use dm-verity disks (e.g. loop devices) signed by keys which did not exist at kernel build time, leveraging the certificate chain of trust model. In practice, this makes it possible to update certificates without kernel update and reboot, aligning with module and kernel (kexec) signature verification which already use the secondary trusted keyring. Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
-rw-r--r--Documentation/admin-guide/device-mapper/verity.rst7
-rw-r--r--drivers/md/Kconfig13
-rw-r--r--drivers/md/dm-verity-verify-sig.c9
3 files changed, 25 insertions, 4 deletions
diff --git a/Documentation/admin-guide/device-mapper/verity.rst b/Documentation/admin-guide/device-mapper/verity.rst
index 66f71f0dab1b..b088a647acb7 100644
--- a/Documentation/admin-guide/device-mapper/verity.rst
+++ b/Documentation/admin-guide/device-mapper/verity.rst
@@ -134,7 +134,12 @@ root_hash_sig_key_desc <key_description>
the pkcs7 signature of the roothash. The pkcs7 signature is used to validate
the root hash during the creation of the device mapper block device.
Verification of roothash depends on the config DM_VERITY_VERIFY_ROOTHASH_SIG
- being set in the kernel.
+ being set in the kernel. The signatures are checked against the builtin
+ trusted keyring by default, or the secondary trusted keyring if
+ DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING is set. The secondary
+ trusted keyring includes by default the builtin trusted keyring, and it can
+ also gain new certificates at run time if they are signed by a certificate
+ already in the secondary trusted keyring.
Theory of operation
===================
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 30ba3573626c..1d68935e45ef 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -530,11 +530,22 @@ config DM_VERITY_VERIFY_ROOTHASH_SIG
bool "Verity data device root hash signature verification support"
depends on DM_VERITY
select SYSTEM_DATA_VERIFICATION
- help
+ help
Add ability for dm-verity device to be validated if the
pre-generated tree of cryptographic checksums passed has a pkcs#7
signature file that can validate the roothash of the tree.
+ By default, rely on the builtin trusted keyring.
+
+ If unsure, say N.
+
+config DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING
+ bool "Verity data device root hash signature verification with secondary keyring"
+ depends on DM_VERITY_VERIFY_ROOTHASH_SIG
+ depends on SECONDARY_TRUSTED_KEYRING
+ help
+ Rely on the secondary trusted keyring to verify dm-verity signatures.
+
If unsure, say N.
config DM_VERITY_FEC
diff --git a/drivers/md/dm-verity-verify-sig.c b/drivers/md/dm-verity-verify-sig.c
index 614e43db93aa..29385dc470d5 100644
--- a/drivers/md/dm-verity-verify-sig.c
+++ b/drivers/md/dm-verity-verify-sig.c
@@ -119,8 +119,13 @@ int verity_verify_root_hash(const void *root_hash, size_t root_hash_len,
}
ret = verify_pkcs7_signature(root_hash, root_hash_len, sig_data,
- sig_len, NULL, VERIFYING_UNSPECIFIED_SIGNATURE,
- NULL, NULL);
+ sig_len,
+#ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING
+ VERIFY_USE_SECONDARY_KEYRING,
+#else
+ NULL,
+#endif
+ VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
return ret;
}