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Message-ID: <51908b87-ae39-790e-62c7-d63c4a85b774@linux.microsoft.com>
Date: Thu, 10 Dec 2020 17:14:39 -0800
From: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To: Tyler Hicks <tyhicks@...ux.microsoft.com>
Cc: zohar@...ux.ibm.com, stephen.smalley.work@...il.com,
casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
gmazyland@...il.com, paul@...l-moore.com, sashal@...nel.org,
jmorris@...ei.org, nramas@...ux.microsoft.com,
linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH v7 1/8] IMA: generalize keyring specific measurement
constructs
On 2020-12-10 2:14 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:05, Tushar Sugandhi wrote:
>> IMA functions such as ima_match_keyring(), process_buffer_measurement(),
>> ima_match_policy() etc. handle data specific to keyrings. Currently,
>> these constructs are not generic to handle any func specific data.
>> This makes it harder to extend them without code duplication.
>>
>> Refactor the keyring specific measurement constructs to be generic and
>> reusable in other measurement scenarios.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>
> I've got a few code cleanup suggestions to ima_match_rule_data() below
> but the current patch is fine:
>
> Reviewed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
>
>> ---
>> security/integrity/ima/ima.h | 6 ++--
>> security/integrity/ima/ima_api.c | 6 ++--
>> security/integrity/ima/ima_main.c | 6 ++--
>> security/integrity/ima/ima_policy.c | 49 ++++++++++++++++++-----------
>> 4 files changed, 40 insertions(+), 27 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index 8e8b1e3cb847..e5622ce8cbb1 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -256,7 +256,7 @@ static inline void ima_process_queued_keys(void) {}
>> int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>> int mask, enum ima_hooks func, int *pcr,
>> struct ima_template_desc **template_desc,
>> - const char *keyring);
>> + const char *func_data);
>> int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
>> int ima_collect_measurement(struct integrity_iint_cache *iint,
>> struct file *file, void *buf, loff_t size,
>> @@ -268,7 +268,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
>> struct ima_template_desc *template_desc);
>> void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>> const char *eventname, enum ima_hooks func,
>> - int pcr, const char *keyring);
>> + int pcr, const char *func_data);
>> void ima_audit_measurement(struct integrity_iint_cache *iint,
>> const unsigned char *filename);
>> int ima_alloc_init_template(struct ima_event_data *event_data,
>> @@ -284,7 +284,7 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
>> int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>> enum ima_hooks func, int mask, int flags, int *pcr,
>> struct ima_template_desc **template_desc,
>> - const char *keyring);
>> + const char *func_data);
>> void ima_init_policy(void);
>> void ima_update_policy(void);
>> void ima_update_policy_flag(void);
>> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
>> index 4f39fb93f278..af218babd198 100644
>> --- a/security/integrity/ima/ima_api.c
>> +++ b/security/integrity/ima/ima_api.c
>> @@ -170,7 +170,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>> * @func: caller identifier
>> * @pcr: pointer filled in if matched measure policy sets pcr=
>> * @template_desc: pointer filled in if matched measure policy sets template=
>> - * @keyring: keyring name used to determine the action
>> + * @func_data: private data specific to @func, can be NULL.
>> *
>> * The policy is defined in terms of keypairs:
>> * subj=, obj=, type=, func=, mask=, fsmagic=
>> @@ -186,14 +186,14 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>> int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
>> int mask, enum ima_hooks func, int *pcr,
>> struct ima_template_desc **template_desc,
>> - const char *keyring)
>> + const char *func_data)
>> {
>> int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
>>
>> flags &= ima_policy_flag;
>>
>> return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
>> - template_desc, keyring);
>> + template_desc, func_data);
>> }
>>
>> /*
>> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
>> index 68956e884403..e76ef4bfd0f4 100644
>> --- a/security/integrity/ima/ima_main.c
>> +++ b/security/integrity/ima/ima_main.c
>> @@ -786,13 +786,13 @@ int ima_post_load_data(char *buf, loff_t size,
>> * @eventname: event name to be used for the buffer entry.
>> * @func: IMA hook
>> * @pcr: pcr to extend the measurement
>> - * @keyring: keyring name to determine the action to be performed
>> + * @func_data: private data specific to @func, can be NULL.
>> *
>> * Based on policy, the buffer is measured into the ima log.
>> */
>> void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>> const char *eventname, enum ima_hooks func,
>> - int pcr, const char *keyring)
>> + int pcr, const char *func_data)
>> {
>> int ret = 0;
>> const char *audit_cause = "ENOMEM";
>> @@ -831,7 +831,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
>> if (func) {
>> security_task_getsecid(current, &secid);
>> action = ima_get_action(inode, current_cred(), secid, 0, func,
>> - &pcr, &template, keyring);
>> + &pcr, &template, func_data);
>> if (!(action & IMA_MEASURE))
>> return;
>> }
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 823a0c1379cb..25419c7ff50b 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -453,30 +453,44 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
>> }
>>
>> /**
>> - * ima_match_keyring - determine whether the keyring matches the measure rule
>> - * @rule: a pointer to a rule
>> - * @keyring: name of the keyring to match against the measure rule
>> + * ima_match_rule_data - determine whether the given func_data matches
>> + * the measure rule data
>> + * @rule: IMA policy rule
>> + * @func_data: data to match against the measure rule data
>> * @cred: a pointer to a credentials structure for user validation
>> *
>> - * Returns true if keyring matches one in the rule, false otherwise.
>> + * Returns true if func_data matches one in the rule, false otherwise.
>> */
>> -static bool ima_match_keyring(struct ima_rule_entry *rule,
>> - const char *keyring, const struct cred *cred)
>> +static bool ima_match_rule_data(struct ima_rule_entry *rule,
>> + const char *func_data,
>> + const struct cred *cred)
>> {
>> + const struct ima_rule_opt_list *opt_list = NULL;
>> bool matched = false;
>> size_t i;
>>
>> if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
>> return false;
>>
>> - if (!rule->keyrings)
>> - return true;
>> + switch (rule->func) {
>> + case KEY_CHECK:
>> + if (!rule->keyrings)
>> + return true;
>> + else
>> + opt_list = rule->keyrings;
>
> You return if rule->keyrings is NULL so drop this else and simply make
> the opt_list assignment.
>
Will do.
>> + break;
>> + default:
>> + break;
>
> I would like to see the 'return false;' happen immediately here instead
> of waiting for the opt_list check below.
Will do.
>
>> + }
>>
>> - if (!keyring)
>> + if (!func_data)
>> + return false;
>> +
>> + if (!opt_list)
>> return false;
>
> If you return false in the 'default:' case above, you can just remove this
> entire conditional because you'll be assigning opt_list in all of the
> valid cases of the switch statement.
>
Yup. Agreed. Will do.
~Tushar
> Tyler
>
>>
>> - for (i = 0; i < rule->keyrings->count; i++) {
>> - if (!strcmp(rule->keyrings->items[i], keyring)) {
>> + for (i = 0; i < opt_list->count; i++) {
>> + if (!strcmp(opt_list->items[i], func_data)) {
>> matched = true;
>> break;
>> }
>> @@ -493,20 +507,20 @@ static bool ima_match_keyring(struct ima_rule_entry *rule,
>> * @secid: the secid of the task to be validated
>> * @func: LIM hook identifier
>> * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
>> - * @keyring: keyring name to check in policy for KEY_CHECK func
>> + * @func_data: private data specific to @func, can be NULL.
>> *
>> * Returns true on rule match, false on failure.
>> */
>> static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>> const struct cred *cred, u32 secid,
>> enum ima_hooks func, int mask,
>> - const char *keyring)
>> + const char *func_data)
>> {
>> int i;
>>
>> if (func == KEY_CHECK) {
>> return (rule->flags & IMA_FUNC) && (rule->func == func) &&
>> - ima_match_keyring(rule, keyring, cred);
>> + ima_match_rule_data(rule, func_data, cred);
>> }
>> if ((rule->flags & IMA_FUNC) &&
>> (rule->func != func && func != POST_SETATTR))
>> @@ -610,8 +624,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>> * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
>> * @pcr: set the pcr to extend
>> * @template_desc: the template that should be used for this rule
>> - * @keyring: the keyring name, if given, to be used to check in the policy.
>> - * keyring can be NULL if func is anything other than KEY_CHECK.
>> + * @func_data: private data specific to @func, can be NULL.
>> *
>> * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
>> * conditions.
>> @@ -623,7 +636,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
>> int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>> enum ima_hooks func, int mask, int flags, int *pcr,
>> struct ima_template_desc **template_desc,
>> - const char *keyring)
>> + const char *func_data)
>> {
>> struct ima_rule_entry *entry;
>> int action = 0, actmask = flags | (flags << 1);
>> @@ -638,7 +651,7 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
>> continue;
>>
>> if (!ima_match_rules(entry, inode, cred, secid, func, mask,
>> - keyring))
>> + func_data))
>> continue;
>>
>> action |= entry->flags & IMA_ACTION_FLAGS;
>> --
>> 2.17.1
>>
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