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[Linux-ima-devel] [PATCH v3 3/4] ima: define "dont_failsafe" policy action rule
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From: Mimi Z. <zo...@li...> - 2017-07-13 13:55:46
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Permit normally denied access/execute permission for files in policy
on IMA unsupported filesystems. This patch defines the "dont_failsafe"
policy action rule.
Mimi Zohar <zo...@li...>
---
Changelog v3:
- include dont_failsafe rule when displaying policy
- fail attempt to add dont_failsafe rule when appending to the policy
Documentation/ABI/testing/ima_policy | 3 ++-
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_main.c | 11 ++++++++++-
security/integrity/ima/ima_policy.c | 29 ++++++++++++++++++++++++++++-
4 files changed, 41 insertions(+), 3 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index e76432b9954d..f271207743e5 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -17,7 +17,8 @@ Description:
rule format: action [condition ...]
- action: measure | dont_measure | appraise | dont_appraise | audit
+ action: measure | dont_meaure | appraise | dont_appraise |
+ audit | dont_failsafe
condition:= base | lsm [option]
base: [[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
[euid=] [fowner=]]
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d52b487ad259..c5f34f7c5b0f 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -224,6 +224,7 @@ void *ima_policy_start(struct seq_file *m, loff_t *pos);
void *ima_policy_next(struct seq_file *m, void *v, loff_t *pos);
void ima_policy_stop(struct seq_file *m, void *v);
int ima_policy_show(struct seq_file *m, void *v);
+void set_failsafe(bool flag);
/* Appraise integrity measurements */
#define IMA_APPRAISE_ENFORCE 0x01
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 63777d1210b1..59e271a20600 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -38,6 +38,11 @@ int ima_appraise;
int ima_hash_algo = HASH_ALGO_SHA1;
static int hash_setup_done;
+static bool ima_failsafe = 1;
+void set_failsafe(bool flag) {
+ ima_failsafe = flag;
+}
+
static int __init hash_setup(char *str)
{
struct ima_template_desc *template_desc = ima_template_desc_current();
@@ -263,8 +268,12 @@ static int process_measurement(struct file *file, char *buf, loff_t size,
__putname(pathbuf);
out:
inode_unlock(inode);
- if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
+ if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+ if (!ima_failsafe && rc == -EBADF)
+ return 0;
+
return -EACCES;
+ }
return 0;
}
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index f4436626ccb7..3c29aa4e7980 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -40,12 +40,14 @@
#define APPRAISE 0x0004 /* same as IMA_APPRAISE */
#define DONT_APPRAISE 0x0008
#define AUDIT 0x0040
+#define DONT_FAILSAFE 0x0400
#define INVALID_PCR(a) (((a) < 0) || \
(a) >= (FIELD_SIZEOF(struct integrity_iint_cache, measured_pcrs) * 8))
int ima_policy_flag;
static int temp_ima_appraise;
+static bool temp_failsafe = 1;
#define MAX_LSM_RULES 6
enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
@@ -513,6 +515,9 @@ void ima_update_policy(void)
if (ima_rules != policy) {
ima_policy_flag = 0;
ima_rules = policy;
+
+ /* Only update on initial policy replacement, not append */
+ set_failsafe(temp_failsafe);
}
ima_update_policy_flag();
}
@@ -529,7 +534,7 @@ enum {
Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt,
Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
Opt_appraise_type, Opt_permit_directio,
- Opt_pcr
+ Opt_pcr, Opt_dont_failsafe
};
static match_table_t policy_tokens = {
@@ -560,6 +565,7 @@ static match_table_t policy_tokens = {
{Opt_appraise_type, "appraise_type=%s"},
{Opt_permit_directio, "permit_directio"},
{Opt_pcr, "pcr=%s"},
+ {Opt_dont_failsafe, "dont_failsafe"},
{Opt_err, NULL}
};
@@ -630,6 +636,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
continue;
token = match_token(p, policy_tokens, args);
+ if (entry->action == DONT_FAILSAFE) {
+ /* no args permitted, force invalid rule */
+ token = Opt_dont_failsafe;
+ }
+
switch (token) {
case Opt_measure:
ima_log_string(ab, "action", "measure");
@@ -671,6 +682,19 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
entry->action = AUDIT;
break;
+ case Opt_dont_failsafe:
+ ima_log_string(ab, "action", "dont_failsafe");
+
+ if (entry->action != UNKNOWN)
+ result = -EINVAL;
+
+ /* Permit on initial policy replacement only */
+ if (ima_rules != &ima_policy_rules)
+ temp_failsafe = 0;
+ else
+ result = -EINVAL;
+ entry->action = DONT_FAILSAFE;
+ break;
case Opt_func:
ima_log_string(ab, "func", args[0].from);
@@ -951,6 +975,7 @@ void ima_delete_rules(void)
int i;
temp_ima_appraise = 0;
+ temp_failsafe = 1;
list_for_each_entry_safe(entry, tmp, &ima_temp_rules, list) {
for (i = 0; i < MAX_LSM_RULES; i++)
kfree(entry->lsm[i].args_p);
@@ -1042,6 +1067,8 @@ int ima_policy_show(struct seq_file *m, void *v)
seq_puts(m, pt(Opt_dont_appraise));
if (entry->action & AUDIT)
seq_puts(m, pt(Opt_audit));
+ if (entry->action & DONT_FAILSAFE)
+ seq_puts(m, pt(Opt_dont_failsafe));
seq_puts(m, " ");
--
2.7.4
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