* [PATCH 3/4] IMA: Add support to limit measuring keys
2020-01-07 19:43 [PATCH 0/4] KEYS: Measure keys when they are created or updated Lakshmi Ramasubramanian
2020-01-07 19:43 ` [PATCH 1/4] IMA: Define an IMA hook to measure keys Lakshmi Ramasubramanian
2020-01-07 19:43 ` [PATCH 2/4] KEYS: Call the " Lakshmi Ramasubramanian
@ 2020-01-07 19:43 ` Lakshmi Ramasubramanian
2020-01-07 19:43 ` [PATCH 4/4] IMA: Read keyrings= option from the IMA policy Lakshmi Ramasubramanian
3 siblings, 0 replies; 7+ messages in thread
From: Lakshmi Ramasubramanian @ 2020-01-07 19:43 UTC (permalink / raw)
To: zohar, James.Bottomley, linux-integrity
Cc: eric.snowberg, dhowells, mathew.j.martineau, matthewgarrett,
sashal, jamorris, linux-kernel, keyrings
Limit measuring keys to those keys being loaded onto a given set of
keyrings only and when the user id (uid) matches if uid is specified
in the policy.
This patch defines a new IMA policy option namely "keyrings=" that
can be used to specify a set of keyrings. If this option is specified
in the policy for "measure func=KEY_CHECK" then only the keys
loaded onto a keyring given in the "keyrings=" option are measured.
If uid is specified in the policy then the key is measured only if
the current user id matches the one specified in the policy.
Added a new parameter namely "keyring" (name of the keyring) to
process_buffer_measurement(). The keyring name is passed to
ima_get_action() to determine the required action.
ima_match_rules() is updated to check keyring in the policy, if
specified, for KEY_CHECK function.
Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Fixes: e9085e0ad38a ("IMA: Add support to limit measuring keys")
---
Documentation/ABI/testing/ima_policy | 10 +++-
security/integrity/ima/ima.h | 8 ++-
security/integrity/ima/ima_api.c | 8 ++-
security/integrity/ima/ima_appraise.c | 4 +-
security/integrity/ima/ima_asymmetric_keys.c | 8 ++-
security/integrity/ima/ima_main.c | 9 +--
security/integrity/ima/ima_policy.c | 62 ++++++++++++++++++--
7 files changed, 91 insertions(+), 18 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 066d32797500..cd572912c593 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -25,7 +25,7 @@ Description:
lsm: [[subj_user=] [subj_role=] [subj_type=]
[obj_user=] [obj_role=] [obj_type=]]
option: [[appraise_type=]] [template=] [permit_directio]
- [appraise_flag=]
+ [appraise_flag=] [keyrings=]
base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
@@ -42,6 +42,9 @@ Description:
appraise_flag:= [check_blacklist]
Currently, blacklist check is only for files signed with appended
signature.
+ keyrings:= list of keyrings
+ (eg, .builtin_trusted_keys|.ima). Only valid
+ when action is "measure" and func is KEY_CHECK.
template:= name of a defined IMA template type
(eg, ima-ng). Only valid when action is "measure".
pcr:= decimal value
@@ -117,3 +120,8 @@ Description:
Example of measure rule using KEY_CHECK to measure all keys:
measure func=KEY_CHECK
+
+ Example of measure rule using KEY_CHECK to only measure
+ keys added to .builtin_trusted_keys or .ima keyring:
+
+ measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index fe6c698617bd..f06238e41a7c 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -208,7 +208,8 @@ struct modsig;
/* LIM API function definitions */
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);
+ struct ima_template_desc **template_desc,
+ const char *keyring);
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,
@@ -220,7 +221,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
struct ima_template_desc *template_desc);
void process_buffer_measurement(const void *buf, int size,
const char *eventname, enum ima_hooks func,
- int pcr);
+ int pcr, const char *keyring);
void ima_audit_measurement(struct integrity_iint_cache *iint,
const unsigned char *filename);
int ima_alloc_init_template(struct ima_event_data *event_data,
@@ -235,7 +236,8 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *filename);
/* IMA policy related functions */
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);
+ struct ima_template_desc **template_desc,
+ const char *keyring);
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 610759fe63b8..f6bc00914aa5 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -169,12 +169,13 @@ 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
*
* The policy is defined in terms of keypairs:
* subj=, obj=, type=, func=, mask=, fsmagic=
* subj,obj, and type: are LSM specific.
* func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
- * | KEXEC_CMDLINE
+ * | KEXEC_CMDLINE | KEY_CHECK
* mask: contains the permission mask
* fsmagic: hex value
*
@@ -183,14 +184,15 @@ 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)
+ struct ima_template_desc **template_desc,
+ const char *keyring)
{
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);
+ template_desc, keyring);
}
/*
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 300c8d2943c5..a9649b04b9f1 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -55,7 +55,7 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
security_task_getsecid(current, &secid);
return ima_match_policy(inode, current_cred(), secid, func, mask,
- IMA_APPRAISE | IMA_HASH, NULL, NULL);
+ IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL);
}
static int ima_fix_xattr(struct dentry *dentry,
@@ -330,7 +330,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
process_buffer_measurement(digest, digestsize,
"blacklisted-hash", NONE,
- pcr);
+ pcr, NULL);
}
return rc;
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 994d89d58af9..fea2e7dd3b09 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -46,7 +46,13 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
* parameter to process_buffer_measurement() and is set
* in the "eventname" field in ima_event_data for
* the key measurement IMA event.
+ *
+ * The name of the keyring is also passed in the "keyring"
+ * parameter to process_buffer_measurement() to check
+ * if the IMA policy is configured to measure a key linked
+ * to the given keyring.
*/
process_buffer_measurement(payload, payload_len,
- keyring->description, KEY_CHECK, 0);
+ keyring->description, KEY_CHECK, 0,
+ keyring->description);
}
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 9b35db2fc777..2272c3255c7d 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -215,7 +215,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
* Included is the appraise submask.
*/
action = ima_get_action(inode, cred, secid, mask, func, &pcr,
- &template_desc);
+ &template_desc, NULL);
violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
(ima_policy_flag & IMA_MEASURE));
if (!action && !violation_check)
@@ -632,12 +632,13 @@ int ima_load_data(enum kernel_load_data_id id)
* @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
*
* Based on policy, the buffer is measured into the ima log.
*/
void process_buffer_measurement(const void *buf, int size,
const char *eventname, enum ima_hooks func,
- int pcr)
+ int pcr, const char *keyring)
{
int ret = 0;
struct ima_template_entry *entry = NULL;
@@ -668,7 +669,7 @@ void process_buffer_measurement(const void *buf, int size,
if (func) {
security_task_getsecid(current, &secid);
action = ima_get_action(NULL, current_cred(), secid, 0, func,
- &pcr, &template);
+ &pcr, &template, keyring);
if (!(action & IMA_MEASURE))
return;
}
@@ -721,7 +722,7 @@ void ima_kexec_cmdline(const void *buf, int size)
{
if (buf && size != 0)
process_buffer_measurement(buf, size, "kexec-cmdline",
- KEXEC_CMDLINE, 0);
+ KEXEC_CMDLINE, 0, NULL);
}
static int __init init_ima(void)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 3f3928b3db99..7667ca546ce9 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -79,6 +79,7 @@ struct ima_rule_entry {
int type; /* audit type */
} lsm[MAX_LSM_RULES];
char *fsname;
+ char *keyrings; /* Measure keys added to these keyrings */
struct ima_template_desc *template;
};
@@ -356,6 +357,50 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
return NOTIFY_OK;
}
+/**
+ * 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
+ * @cred: a pointer to a credentials structure for user validation
+ *
+ * Returns true if keyring matches one in the rule, false otherwise.
+ */
+static bool ima_match_keyring(struct ima_rule_entry *rule,
+ const char *keyring, const struct cred *cred)
+{
+ char *keyrings, *next_keyring, *keyrings_ptr;
+ bool matched = false;
+
+ if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
+ return false;
+
+ if (!rule->keyrings)
+ return true;
+
+ if (!keyring)
+ return false;
+
+ keyrings = kstrdup(rule->keyrings, GFP_KERNEL);
+ if (!keyrings)
+ return false;
+
+ /*
+ * "keyrings=" is specified in the policy in the format below:
+ * keyrings=.builtin_trusted_keys|.ima|.evm
+ */
+ keyrings_ptr = keyrings;
+ while ((next_keyring = strsep(&keyrings_ptr, "|")) != NULL) {
+ if (!strcmp(next_keyring, keyring)) {
+ matched = true;
+ break;
+ }
+ }
+
+ kfree(keyrings);
+
+ return matched;
+}
+
/**
* ima_match_rules - determine whether an inode matches the measure rule.
* @rule: a pointer to a rule
@@ -364,18 +409,23 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
* @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
*
* 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)
+ enum ima_hooks func, int mask,
+ const char *keyring)
{
int i;
if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
- if ((rule->flags & IMA_FUNC) && (rule->func == func))
+ if ((rule->flags & IMA_FUNC) && (rule->func == func)) {
+ if (func == KEY_CHECK)
+ return ima_match_keyring(rule, keyring, cred);
return true;
+ }
return false;
}
if ((rule->flags & IMA_FUNC) &&
@@ -479,6 +529,8 @@ 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.
*
* Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
* conditions.
@@ -489,7 +541,8 @@ 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)
+ struct ima_template_desc **template_desc,
+ const char *keyring)
{
struct ima_rule_entry *entry;
int action = 0, actmask = flags | (flags << 1);
@@ -503,7 +556,8 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
if (!(entry->action & actmask))
continue;
- if (!ima_match_rules(entry, inode, cred, secid, func, mask))
+ if (!ima_match_rules(entry, inode, cred, secid, func, mask,
+ keyring))
continue;
action |= entry->flags & IMA_ACTION_FLAGS;
--
2.17.1
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH 4/4] IMA: Read keyrings= option from the IMA policy
2020-01-07 19:43 [PATCH 0/4] KEYS: Measure keys when they are created or updated Lakshmi Ramasubramanian
` (2 preceding siblings ...)
2020-01-07 19:43 ` [PATCH 3/4] IMA: Add support to limit measuring keys Lakshmi Ramasubramanian
@ 2020-01-07 19:43 ` Lakshmi Ramasubramanian
3 siblings, 0 replies; 7+ messages in thread
From: Lakshmi Ramasubramanian @ 2020-01-07 19:43 UTC (permalink / raw)
To: zohar, James.Bottomley, linux-integrity
Cc: eric.snowberg, dhowells, mathew.j.martineau, matthewgarrett,
sashal, jamorris, linux-kernel, keyrings
Read "keyrings=" option, if specified in the IMA policy, and store in
the list of IMA rules when the configured IMA policy is read.
This patch defines a new policy token enum namely Opt_keyrings
and an option flag IMA_KEYRINGS for reading "keyrings=" option
from the IMA policy.
Updated ima_parse_rule() to parse "keyrings=" option in the policy.
Updated ima_policy_show() to display "keyrings=" option.
The following example illustrates how key measurement can be verified.
Sample "key" measurement rule in the IMA policy:
measure func=KEY_CHECK uid=0 keyrings=.ima|.evm template=ima-buf
Display "key" measurement in the IMA measurement list:
cat /sys/kernel/security/ima/ascii_runtime_measurements
10 faf3...e702 ima-buf sha256:27c915b8ddb9fae7214cf0a8a7043cc3eeeaa7539bcb136f8427067b5f6c3b7b .ima 308202863082...4aee
Verify "key" measurement data for a key added to ".ima" keyring:
cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements | grep -m 1 "\.ima" | cut -d' ' -f 6 | xxd -r -p |tee ima-cert.der | sha256sum | cut -d' ' -f 1
The output of the above command should match the template hash
of the first "key" measurement entry in the IMA measurement list for
the key added to ".ima" keyring.
The file namely "ima-cert.der" generated by the above command
should be a valid x509 certificate (in DER format) and should match
the one that was used to import the key to the ".ima" keyring.
The certificate file can be verified using openssl tool.
Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Fixes: 2b60c0ecedf8 ("IMA: Read keyrings= option from the IMA policy")
---
security/integrity/ima/ima_policy.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 7667ca546ce9..8f2ca487753b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -34,6 +34,7 @@
#define IMA_EUID 0x0080
#define IMA_PCR 0x0100
#define IMA_FSNAME 0x0200
+#define IMA_KEYRINGS 0x0400
#define UNKNOWN 0
#define MEASURE 0x0001 /* same as IMA_MEASURE */
@@ -820,7 +821,8 @@ enum {
Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt,
Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
Opt_appraise_type, Opt_appraise_flag,
- Opt_permit_directio, Opt_pcr, Opt_template, Opt_err
+ Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
+ Opt_err
};
static const match_table_t policy_tokens = {
@@ -856,6 +858,7 @@ static const match_table_t policy_tokens = {
{Opt_permit_directio, "permit_directio"},
{Opt_pcr, "pcr=%s"},
{Opt_template, "template=%s"},
+ {Opt_keyrings, "keyrings=%s"},
{Opt_err, NULL}
};
@@ -1105,6 +1108,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
result = 0;
entry->flags |= IMA_FSNAME;
break;
+ case Opt_keyrings:
+ ima_log_string(ab, "keyrings", args[0].from);
+
+ if ((entry->keyrings) ||
+ (entry->action != MEASURE) ||
+ (entry->func != KEY_CHECK)) {
+ result = -EINVAL;
+ break;
+ }
+ entry->keyrings = kstrdup(args[0].from, GFP_KERNEL);
+ if (!entry->keyrings) {
+ result = -ENOMEM;
+ break;
+ }
+ result = 0;
+ entry->flags |= IMA_KEYRINGS;
+ break;
case Opt_fsuuid:
ima_log_string(ab, "fsuuid", args[0].from);
@@ -1480,6 +1500,13 @@ int ima_policy_show(struct seq_file *m, void *v)
seq_puts(m, " ");
}
+ if (entry->flags & IMA_KEYRINGS) {
+ if (entry->keyrings != NULL)
+ snprintf(tbuf, sizeof(tbuf), "%s", entry->keyrings);
+ seq_printf(m, pt(Opt_keyrings), tbuf);
+ seq_puts(m, " ");
+ }
+
if (entry->flags & IMA_PCR) {
snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
seq_printf(m, pt(Opt_pcr), tbuf);
--
2.17.1
^ permalink raw reply [flat|nested] 7+ messages in thread