On Wed, Jul 26, 2017 at 4:22 PM, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> 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 <zohar@xxxxxxxxxxxxxxxxxx>
>
> ---
> 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 3941371402ff..664edab0f758 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;
> +
By default IMA is failsaif. ima_failsafe is true.
Return 0 is needed in failsafe mode. right?
But in this logic it will happen if ima_failsafe is false. meaning it
is not failsafe.
Is it a typo?
> return -EACCES;
> + }
> return 0;
> }
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 95209a5f8595..43b85a4fb8e8 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);
>
> @@ -949,6 +973,7 @@ 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);
> @@ -1040,6 +1065,8 @@ 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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--
Thanks,
Dmitry
