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authorTushar Sugandhi <tusharsu@linux.microsoft.com>2021-05-10 12:09:39 -0700
committerMimi Zohar <zohar@linux.ibm.com>2021-06-11 12:54:13 -0400
commit52c208397c246f0c31d031eb8c41f9c7e9fdec0e (patch)
tree6db05a7ec72b77609154632ba1fbe6e682bb0fd3 /security
parentc67913492fec317bc53ffdff496b6ba856d2868c (diff)
IMA: support for duplicate measurement records
IMA measures contents of a given file/buffer/critical-data record, and properly re-measures it on change. However, IMA does not measure the duplicate value for a given record, since TPM extend is a very expensive operation. For example, if the record changes from value 'v#1' to 'v#2', and then back to 'v#1', IMA will not measure and log the last change to 'v#1', since the hash of 'v#1' for that record is already present in the IMA htable. This limits the ability of an external attestation service to accurately determine the current state of the system. The service would incorrectly conclude that the latest value of the given record on the system is 'v#2', and act accordingly. Define and use a new Kconfig option IMA_DISABLE_HTABLE to permit duplicate records in the IMA measurement list. In addition to the duplicate measurement records described above, other duplicate file measurement records may be included in the log, when CONFIG_IMA_DISABLE_HTABLE is enabled. For example, - i_version is not enabled, - i_generation changed, - same file present on different filesystems, - an inode is evicted from dcache Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com> Reviewed-by: Petr Vorel <pvorel@suse.cz> [zohar@linux.ibm.com: updated list of duplicate measurement records] Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security')
-rw-r--r--security/integrity/ima/Kconfig7
-rw-r--r--security/integrity/ima/ima_queue.c5
2 files changed, 10 insertions, 2 deletions
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 12e9250c1bec..d0ceada99243 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -334,3 +334,10 @@ config IMA_SECURE_AND_OR_TRUSTED_BOOT
help
This option is selected by architectures to enable secure and/or
trusted boot based on IMA runtime policies.
+
+config IMA_DISABLE_HTABLE
+ bool "Disable htable to allow measurement of duplicate records"
+ depends on IMA
+ default n
+ help
+ This option disables htable to allow measurement of duplicate records.
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index c096ef8945c7..532da87ce519 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -168,7 +168,7 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
int result = 0, tpmresult = 0;
mutex_lock(&ima_extend_list_mutex);
- if (!violation) {
+ if (!violation && !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE)) {
if (ima_lookup_digest_entry(digest, entry->pcr)) {
audit_cause = "hash_exists";
result = -EEXIST;
@@ -176,7 +176,8 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
}
}
- result = ima_add_digest_entry(entry, 1);
+ result = ima_add_digest_entry(entry,
+ !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE));
if (result < 0) {
audit_cause = "ENOMEM";
audit_info = 0;