[PATCH 5/7] ima: Introduce appraise_exec_immutable policy

[Roberto Sassu]

This patch modifies the existing "appraise_exec_tcb" policy, by adding the
appraise_type=meta_immutable requirement for executed files. This policy
can be selected by specifying
ima_policy="appraise_exec_tcb|appraise_exec_immutable" in the kernel
command line.
Signed-off-by: Roberto Sassu <roberto.sa...@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 security/integrity/ima/ima_policy.c             | 8 +++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 93c5f78905e2..265f7657f59d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1780,6 +1780,10 @@
                        appraised (with imasig requirement) instead of files
                        owned by root.
 
+                       The "appraise_exec_immutable" policy requires immutable
+                       metadata for executed files, if the "appraise_exec_tcb"
+                       policy is selected.
+
                        The "appraise_tmpfs" policy excludes the dont_appraise
                        rule for the tmpfs and ramfs filesystems for the
                        "appraise_tcb" and "appraise_exec_tcb" policies.
diff --git a/security/integrity/ima/ima_policy.c 
b/security/integrity/ima/ima_policy.c
index a45e494e06e8..6249817ebd04 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -243,6 +243,7 @@ __setup("ima_tcb", default_measure_policy_setup);
 static unsigned int ima_measure_skip_flags __initdata;
 static unsigned int ima_appraise_skip_flags __initdata;
 static bool ima_use_appraise_tcb __initdata;
+static bool ima_use_appraise_exec_immutable __initdata;
 static bool ima_use_secure_boot __initdata;
 static bool ima_use_critical_data __initdata;
 static bool ima_fail_unverifiable_sigs __ro_after_init;
@@ -267,7 +268,9 @@ static int __init policy_setup(char *str)
                else if (strcmp(p, "appraise_exec_tcb") == 0) {
                        ima_use_appraise_tcb = true;
                        ima_appraise_skip_flags |= IMA_SKIP_OPEN;
-               } else if (strcmp(p, "secure_boot") == 0)
+               } else if (strcmp(p, "appraise_exec_immutable") == 0)
+                       ima_use_appraise_exec_immutable = true;
+               else if (strcmp(p, "secure_boot") == 0)
                        ima_use_secure_boot = true;
                else if (strcmp(p, "critical_data") == 0)
                        ima_use_critical_data = true;
@@ -913,6 +916,9 @@ void __init ima_init_policy(void)
                                  IMA_DEFAULT_POLICY, 0);
        }
 
+       if (ima_use_appraise_exec_immutable)
+               appraise_exec_rules[0].flags |= IMA_META_IMMUTABLE_REQUIRED;
+
        if (ima_use_critical_data)
                add_rules(critical_data_rules,
                          ARRAY_SIZE(critical_data_rules),
-- 
2.26.2