[Linux-ima-devel] [PATCH v4 4/5] ima: define "fs_unsafe" builtin policy

Permit normally denied access/execute permission for files in policy
on IMA unsupported filesystems.  This patch defines "fs_unsafe", a
builtin policy.

Mimi Zohar [off-list ref]

---
Changelog v3:
- include dont_failsafe rule when displaying policy

 Documentation/admin-guide/kernel-parameters.txt |  8 +++++++-
 security/integrity/ima/ima_policy.c             | 12 ++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d9c171ce4190..4e303be83df6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -1502,7 +1502,7 @@

        ima_policy=     [IMA]
                        The builtin policies to load during IMA setup.
-                       Format: "tcb | appraise_tcb | secure_boot"
+                       Format: "tcb | appraise_tcb | secure_boot | fs_unsafe"

                        The "tcb" policy measures all programs exec'd, files
                        mmap'd for exec, and all files opened with the read

@@ -1517,6 +1517,12 @@
                        of files (eg. kexec kernel image, kernel modules,
                        firmware, policy, etc) based on file signatures.

+                       The "fs_unsafe" policy permits normally denied
+                       access/execute permission for files in policy on IMA
+                       unsupported filesystems.  Note this option, as the
+                       name implies, is not safe and not recommended for
+                       any environments other than testing.
+
        ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
                        Load a policy which meets the needs of the Trusted
                        Computing Base.  This means IMA will measure all

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 43b85a4fb8e8..cddd9dfb01e1 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c

@@ -169,6 +169,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
         .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
 };

+static struct ima_rule_entry dont_failsafe_rules[] __ro_after_init = {
+       {.action = DONT_FAILSAFE}
+};
+
 static LIST_HEAD(ima_default_rules);
 static LIST_HEAD(ima_policy_rules);
 static LIST_HEAD(ima_temp_rules);

@@ -188,6 +192,7 @@ __setup("ima_tcb", default_measure_policy_setup);

 static bool ima_use_appraise_tcb __initdata;
 static bool ima_use_secure_boot __initdata;
+static bool ima_use_dont_failsafe __initdata;
 static int __init policy_setup(char *str)
 {
        char *p;

@@ -201,6 +206,10 @@ static int __init policy_setup(char *str)
                        ima_use_appraise_tcb = 1;
                else if (strcmp(p, "secure_boot") == 0)
                        ima_use_secure_boot = 1;
+               else if (strcmp(p, "fs_unsafe") == 0) {
+                       ima_use_dont_failsafe = 1;
+                       set_failsafe(0);
+               }
        }

        return 1;

@@ -470,6 +479,9 @@ void __init ima_init_policy(void)
                        temp_ima_appraise |= IMA_APPRAISE_POLICY;
        }

+       if (ima_use_dont_failsafe)
+               list_add_tail(&dont_failsafe_rules[0].list, &ima_default_rules);
+
        ima_rules = &ima_default_rules;
        ima_update_policy_flag();
 }
--

2.7.4


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