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authorStefan Berger <stefanb@linux.ibm.com>2024-02-23 12:25:11 -0500
committerMimi Zohar <zohar@linux.ibm.com>2024-04-09 17:14:57 -0400
commit47add87ad181473e5ef2438918669540ba5016a6 (patch)
treec684b07c6bea4a972cf5f6609d210859c16e9d23 /security
parentcd9b909a117210bfd77a89bb06a3154c1fc51b51 (diff)
evm: Enforce signatures on unsupported filesystem for EVM_INIT_X509
Unsupported filesystems currently do not enforce any signatures. Add support for signature enforcement of the "original" and "portable & immutable" signatures when EVM_INIT_X509 is enabled. The "original" signature type contains filesystem specific metadata. Thus it cannot be copied up and verified. However with EVM_INIT_X509 and EVM_ALLOW_METADATA_WRITES enabled, the "original" file signature may be written. When EVM_ALLOW_METADATA_WRITES is not set or once it is removed from /sys/kernel/security/evm by setting EVM_INIT_HMAC for example, it is not possible to write or remove xattrs on the overlay filesystem. This change still prevents EVM from writing HMAC signatures on unsupported filesystem when EVM_INIT_HMAC is enabled. Co-developed-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security')
-rw-r--r--security/integrity/evm/evm_main.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index c1ca0894cd8a..cfb4f9809369 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -192,7 +192,11 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
return iint->evm_status;
- if (is_unsupported_fs(dentry))
+ /*
+ * On unsupported filesystems without EVM_INIT_X509 enabled, skip
+ * signature verification.
+ */
+ if (!(evm_initialized & EVM_INIT_X509) && is_unsupported_fs(dentry))
return INTEGRITY_UNKNOWN;
/* if status is not PASS, try to check again - against -ENOMEM */
@@ -261,7 +265,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
evm_status = INTEGRITY_PASS_IMMUTABLE;
} else if (!IS_RDONLY(inode) &&
!(inode->i_sb->s_readonly_remount) &&
- !IS_IMMUTABLE(inode)) {
+ !IS_IMMUTABLE(inode) &&
+ !is_unsupported_fs(dentry)) {
evm_update_evmxattr(dentry, xattr_name,
xattr_value,
xattr_value_len);
@@ -419,9 +424,6 @@ enum integrity_status evm_verifyxattr(struct dentry *dentry,
if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
return INTEGRITY_UNKNOWN;
- if (is_unsupported_fs(dentry))
- return INTEGRITY_UNKNOWN;
-
return evm_verify_hmac(dentry, xattr_name, xattr_value,
xattr_value_len);
}