ipe: enable support for fs-verity as a trust provider

Enable IPE policy authors to indicate trust for a singular fsverity
file, identified by the digest information, through "fsverity_digest"
and all files using valid fsverity builtin signatures via
"fsverity_signature".

This enables file-level integrity claims to be expressed in IPE,
allowing individual files to be authorized, giving some flexibility
for policy authors. Such file-level claims are important to be expressed
for enforcing the integrity of packages, as well as address some of the
scalability issues in a sole dm-verity based solution (# of loop back
devices, etc).

This solution cannot be done in userspace as the minimum threat that
IPE should mitigate is an attacker downloads malicious payload with
all required dependencies. These dependencies can lack the userspace
check, bypassing the protection entirely. A similar attack succeeds if
the userspace component is replaced with a version that does not
perform the check. As a result, this can only be done in the common
entry point - the kernel.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index 8e21879e96c7..f05f0caa4850 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -56,6 +56,9 @@ static const char *const audit_prop_names[__IPE_PROP_MAX] = {
 	"dmverity_roothash=",
 	"dmverity_signature=FALSE",
 	"dmverity_signature=TRUE",
+	"fsverity_digest=",
+	"fsverity_signature=FALSE",
+	"fsverity_signature=TRUE",
 };
 
 /**
@@ -70,6 +73,17 @@ static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
 }
 
 /**
+ * audit_fsv_digest() - audit the digest of a fsverity_digest property.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @d: Supplies a pointer to the digest structure.
+ */
+static void audit_fsv_digest(struct audit_buffer *ab, const void *d)
+{
+	audit_log_format(ab, "%s", audit_prop_names[IPE_PROP_FSV_DIGEST]);
+	ipe_digest_audit(ab, d);
+}
+
+/**
  * audit_rule() - audit an IPE policy rule.
  * @ab: Supplies a pointer to the audit_buffer to append to.
  * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
@@ -85,6 +99,9 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
 		case IPE_PROP_DMV_ROOTHASH:
 			audit_dmv_roothash(ab, ptr->value);
 			break;
+		case IPE_PROP_FSV_DIGEST:
+			audit_fsv_digest(ab, ptr->value);
+			break;
 		default:
 			audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
 			break;