Keys created or updated in the system are currently not measured.
Therefore an attestation service, for instance, would not be able to
attest whether or not the trusted keys keyring(s), for instance, contain
only known good (trusted) keys.
IMA measures system files, command line arguments passed to kexec,
boot aggregate, etc. It can be used to measure keys as well.
But there is no mechanism available in the kernel for IMA to
know when a key is created or updated.
This change aims to address measuring keys created or updated
in the system.
To achieve the above the following changes have been made:
- Added a new IMA hook namely, ima_post_key_create_or_update, which
measures the key. This IMA hook is called from key_create_or_update
function. The key measurement can be controlled through IMA policy.
A new IMA policy function KEY_CHECK has been added to measure keys.
"keyrings=" option can be specified for KEY_CHECK to limit
measuring the keys loaded onto the specified keyrings only.
uid can be specified to further restrict key measurement for keys
created by specific user.
# measure keys loaded onto any keyring
measure func=KEY_CHECK
# measure keys loaded onto the IMA keyring only for root user
measure func=KEY_CHECK uid=0 keyring=".ima"
# measure keys on the BUILTIN and IMA keyrings into a different PCR
measure func=KEY_CHECK keyring=".builtin_trusted_keys|.ima" pcr=11
Testing performed:
* Booted the kernel with this change.
* When KEY_CHECK policy is set IMA measures keys loaded
onto any keyring (keyrings= option not specified).
* Keys are not measured when KEY_CHECK is not set.
* When keyrings= option is specified for KEY_CHECK then only the keys
loaded onto a keyring specified in the option is measured.
* When uid is specified in the policy the key is measured
only when the current user id matches the one given in the policy.
* Added a new key to a keyring.
=> Added keys to .ima and .evm keyrings.
* Added the same key again.
=> Add the same key to .ima and .evm keyrings.
Change Log:
v11:
=> Rebased the changes to v5.5-rc1
=> Check user id (uid) before checking keyring in ima_match_keyring()
=> Updated patch descriptions per Mimi's feedback.
v10:
=> Added check for user id (uid) in ima_match_keyring()
=> Updated ima_match_keyring() function to use strsep() to
check for keyring match.
=> Edited key measurement validation description.
v9:
=> Changed the measured key data from just the public key to
the entire payload passed to key_create_or_update() function.
This payload is the certificate from which the key is created
or updated by key_create_or_update() function.
=> Added check in process_buffer_measurement() to return
immediately if ima_policy_flag is set to zero.
v8:
=> Updated ima_match_keyring() function to check for
whole keyring name match.
=> Used CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE instead of
CONFIG_KEYS to build ima_asymmetric_keys.c and enable
the IMA hook to measure keys since this config handles
the required build time dependencies better.
=> Updated patch description to illustrate verification
of key measurement.
v7:
=> Removed CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS option and used
CONFIG_KEYS instead for ima_asymmetric_keys.c
=> Added the patches related to "keyrings=" option support to
this patch set.
v6:
=> Rebased the changes to v5.4-rc7
=> Renamed KEYRING_CHECK to KEY_CHECK per Mimi's suggestion.
=> Excluded the patches that add support for limiting key
measurement to specific keyrings ("keyrings=" option
for "measure func=KEY_CHECK" in the IMA policy).
Also, excluded the patches that add support for deferred
processing of keys (queue support).
These patches will be added in separate patch sets later.
v5:
=> Reorganized the patches to add measurement of keys through
the IMA hook without any queuing and then added queuing support.
=> Updated the queuing functions to minimize code executed inside mutex.
=> Process queued keys after custom IMA policies have been applied.
v4:
=> Rebased the changes to v5.4-rc3
=> Applied the following dependent patch set first
and then added new changes.
https://lore.kernel.org/linux-integrity/[email protected]
=> Refactored the patch set to separate out changes related to
func KEYRING_CHECK and options keyrings into different patches.
=> Moved the functions to queue and dequeue keys for measurement
from ima_queue.c to a new file ima_asymmetric_keys.c.
=> Added a new config namely CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
to compile ima_asymmetric_keys.c
v3:
=> Added KEYRING_CHECK for measuring keys. This can optionally specify
keyrings to measure.
=> Updated ima_get_action() and related functions to return
the keyrings if specified in the policy.
=> process_buffer_measurement() function is updated to take keyring
as a parameter. The key will be measured if the policy includes
the keyring in the list of measured keyrings. If the policy does not
specify any keyrings then all keys are measured.
v2:
=> Per suggestion from Mimi reordered the patch set to first
enable measuring keys added or updated in the system.
And, then scope the measurement to keys added to
builtin_trusted_keys keyring through ima policy.
=> Removed security_key_create_or_update function and instead
call ima hook, to measure the key, directly from
key_create_or_update function.
v1:
=> LSM function for key_create_or_update. It calls ima.
=> Added ima hook for measuring keys
=> ima measures keys based on ima policy.
v0:
=> Added LSM hook for key_create_or_update.
=> Measure keys added to builtin or secondary trusted keys keyring.
Lakshmi Ramasubramanian (6):
IMA: Check IMA policy flag
IMA: Add KEY_CHECK func to measure keys
IMA: Define an IMA hook to measure keys
KEYS: Call the IMA hook to measure keys
IMA: Add support to limit measuring keys
IMA: Read keyrings= option from the IMA policy
Documentation/ABI/testing/ima_policy | 16 +++-
include/linux/ima.h | 14 +++
security/integrity/ima/Makefile | 1 +
security/integrity/ima/ima.h | 9 +-
security/integrity/ima/ima_api.c | 8 +-
security/integrity/ima/ima_appraise.c | 4 +-
security/integrity/ima/ima_asymmetric_keys.c | 58 ++++++++++++
security/integrity/ima/ima_main.c | 12 ++-
security/integrity/ima/ima_policy.c | 95 ++++++++++++++++++--
security/keys/key.c | 10 +++
10 files changed, 207 insertions(+), 20 deletions(-)
create mode 100644 security/integrity/ima/ima_asymmetric_keys.c
--
2.17.1
Measure keys loaded onto any keyring.
This patch defines a new IMA policy func namely KEY_CHECK to
measure keys. Updated ima_match_rules() to check for KEY_CHECK
and ima_parse_rule() to handle KEY_CHECK.
Signed-off-by: Lakshmi Ramasubramanian <[email protected]>
---
Documentation/ABI/testing/ima_policy | 6 +++++-
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_policy.c | 4 +++-
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 29aaedf33246..066d32797500 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -29,7 +29,7 @@ Description:
base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
- [KEXEC_CMDLINE]
+ [KEXEC_CMDLINE] [KEY_CHECK]
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
[[^]MAY_EXEC]
fsmagic:= hex value
@@ -113,3 +113,7 @@ Description:
Example of appraise rule allowing modsig appended signatures:
appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
+
+ Example of measure rule using KEY_CHECK to measure all keys:
+
+ measure func=KEY_CHECK
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index df4ca482fb53..fe6c698617bd 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -193,6 +193,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
hook(KEXEC_INITRAMFS_CHECK) \
hook(POLICY_CHECK) \
hook(KEXEC_CMDLINE) \
+ hook(KEY_CHECK) \
hook(MAX_CHECK)
#define __ima_hook_enumify(ENUM) ENUM,
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index f19a895ad7cd..1525a28fd705 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -373,7 +373,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
{
int i;
- if (func == KEXEC_CMDLINE) {
+ if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
if ((rule->flags & IMA_FUNC) && (rule->func == func))
return true;
return false;
@@ -997,6 +997,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
entry->func = POLICY_CHECK;
else if (strcmp(args[0].from, "KEXEC_CMDLINE") == 0)
entry->func = KEXEC_CMDLINE;
+ else if (strcmp(args[0].from, "KEY_CHECK") == 0)
+ entry->func = KEY_CHECK;
else
result = -EINVAL;
if (!result)
--
2.17.1
Call the IMA hook from key_create_or_update() function to measure
the payload when a new key is created or an existing key is updated.
This patch adds the call to the IMA hook from key_create_or_update()
function to measure the key on key create or update.
Signed-off-by: Lakshmi Ramasubramanian <[email protected]>
Cc: David Howells <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
---
include/linux/ima.h | 14 ++++++++++++++
security/keys/key.c | 10 ++++++++++
2 files changed, 24 insertions(+)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 6d904754d858..3b89136bc218 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -101,6 +101,20 @@ static inline void ima_add_kexec_buffer(struct kimage *image)
{}
#endif
+#if defined(CONFIG_IMA) && defined(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE)
+extern void ima_post_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const void *payload, size_t plen,
+ unsigned long flags, bool create);
+#else
+static inline void ima_post_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const void *payload,
+ size_t plen,
+ unsigned long flags,
+ bool create) {}
+#endif /* CONFIG_IMA && CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE */
+
#ifdef CONFIG_IMA_APPRAISE
extern bool is_ima_appraise_enabled(void);
extern void ima_inode_post_setattr(struct dentry *dentry);
diff --git a/security/keys/key.c b/security/keys/key.c
index 764f4c57913e..718bf7217420 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -13,6 +13,7 @@
#include <linux/security.h>
#include <linux/workqueue.h>
#include <linux/random.h>
+#include <linux/ima.h>
#include <linux/err.h>
#include "internal.h"
@@ -936,6 +937,9 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
goto error_link_end;
}
+ ima_post_key_create_or_update(keyring, key, payload, plen,
+ flags, true);
+
key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
error_link_end:
@@ -965,6 +969,12 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
}
key_ref = __key_update(key_ref, &prep);
+
+ if (!IS_ERR(key_ref))
+ ima_post_key_create_or_update(keyring, key,
+ payload, plen,
+ flags, false);
+
goto error_free_prep;
}
EXPORT_SYMBOL(key_create_or_update);
--
2.17.1
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 <[email protected]>
---
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 1525a28fd705..cca87c499c4f 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
process_buffer_measurement() may be called prior to IMA being
initialized (for instance, when the IMA hook is called when
a key is added to the .builtin_trusted_keys keyring), which
would result in a kernel panic.
This patch adds the check in process_buffer_measurement()
to return immediately if IMA is not initialized yet.
Signed-off-by: Lakshmi Ramasubramanian <[email protected]>
---
security/integrity/ima/ima_main.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index d7e987baf127..9b35db2fc777 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -655,6 +655,9 @@ void process_buffer_measurement(const void *buf, int size,
int action = 0;
u32 secid;
+ if (!ima_policy_flag)
+ return;
+
/*
* Both LSM hooks and auxilary based buffer measurements are
* based on policy. To avoid code duplication, differentiate
--
2.17.1
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 <[email protected]>
---
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 cca87c499c4f..a4dde9d575b2 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
Hi Lakshmi,
On Wed, 2019-12-11 at 08:47 -0800, Lakshmi Ramasubramanian wrote:
> Keys created or updated in the system are currently not measured.
> Therefore an attestation service, for instance, would not be able to
> attest whether or not the trusted keys keyring(s), for instance, contain
> only known good (trusted) keys.
>
> IMA measures system files, command line arguments passed to kexec,
> boot aggregate, etc. It can be used to measure keys as well.
> But there is no mechanism available in the kernel for IMA to
> know when a key is created or updated.
>
> This change aims to address measuring keys created or updated
> in the system.
Thank you! This patch set is now queued in the next-integrity-testing
branch of https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-
integrity.git/.
Mimi
On 12/12/19 6:28 AM, Mimi Zohar wrote:
> Hi Lakshmi,
>
> On Wed, 2019-12-11 at 08:47 -0800, Lakshmi Ramasubramanian wrote:
>> Keys created or updated in the system are currently not measured.
>> Therefore an attestation service, for instance, would not be able to
>> attest whether or not the trusted keys keyring(s), for instance, contain
>> only known good (trusted) keys.
>>
>> IMA measures system files, command line arguments passed to kexec,
>> boot aggregate, etc. It can be used to measure keys as well.
>> But there is no mechanism available in the kernel for IMA to
>> know when a key is created or updated.
>>
>> This change aims to address measuring keys created or updated
>> in the system.
>
> Thank you! This patch set is now queued in the next-integrity-testing
> branch of https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-
> integrity.git/.
>
> Mimi
>
Thanks Mimi.
-lakshmi