[PATCH 12/12] ima: Support additional conditionals in the KEXEC_CMDLINE hook function

From: Tyler Hicks
Date: Mon Jun 22 2020 - 20:34:41 EST

Next message: Tyler Hicks: "[PATCH 08/12] ima: Shallow copy the args_p member of ima_rule_entry.lsm elements"
Previous message: Tyler Hicks: "[PATCH 11/12] ima: Use the common function to detect LSM conditionals in a rule"
In reply to: Tyler Hicks: "[PATCH 11/12] ima: Use the common function to detect LSM conditionals in a rule"
Next in thread: Tyler Hicks: "[PATCH 08/12] ima: Shallow copy the args_p member of ima_rule_entry.lsm elements"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Take the properties of the kexec kernel's inode and the current task
ownership into consideration when matching a KEXEC_CMDLINE operation to
the rules in the IMA policy. This allows for some uniformity when
writing IMA policy rules for KEXEC_KERNEL_CHECK, KEXEC_INITRAMFS_CHECK,
and KEXEC_CMDLINE operations.

Prior to this patch, it was not possible to write a set of rules like
this:

dont_measure func=KEXEC_KERNEL_CHECK obj_type=foo_t
dont_measure func=KEXEC_INITRAMFS_CHECK obj_type=foo_t
dont_measure func=KEXEC_CMDLINE obj_type=foo_t
measure func=KEXEC_KERNEL_CHECK
measure func=KEXEC_INITRAMFS_CHECK
measure func=KEXEC_CMDLINE

The inode information associated with the kernel being loaded by a
kexec_kernel_load(2) syscall can now be included in the decision to
measure or not

Additonally, the uid, euid, and subj_* conditionals can also now be
used in KEXEC_CMDLINE rules. There was no technical reason as to why
those conditionals weren't being considered previously other than
ima_match_rules() didn't have a valid inode to use so it immediately
bailed out for KEXEC_CMDLINE operations rather than going through the
full list of conditional comparisons.

Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: kexec@xxxxxxxxxxxxxxxxxxx
---
include/linux/ima.h | 4 ++--
kernel/kexec_file.c | 2 +-
security/integrity/ima/ima.h | 3 ++-
security/integrity/ima/ima_api.c | 2 +-
security/integrity/ima/ima_appraise.c | 2 +-
security/integrity/ima/ima_asymmetric_keys.c | 2 +-
security/integrity/ima/ima_main.c | 24 +++++++++++++++-----
security/integrity/ima/ima_policy.c | 17 +++++---------
security/integrity/ima/ima_queue_keys.c | 2 +-
9 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 9164e1534ec9..d15100de6cdd 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -25,7 +25,7 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum kernel_read_file_id id);
extern void ima_post_path_mknod(struct dentry *dentry);
extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
-extern void ima_kexec_cmdline(const void *buf, int size);
+extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);

#ifdef CONFIG_IMA_KEXEC
extern void ima_add_kexec_buffer(struct kimage *image);
@@ -103,7 +103,7 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
return -EOPNOTSUPP;
}

-static inline void ima_kexec_cmdline(const void *buf, int size) {}
+static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
#endif /* CONFIG_IMA */

#ifndef CONFIG_IMA_KEXEC
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index bb05fd52de85..07df431c1f21 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -287,7 +287,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
goto out;
}

- ima_kexec_cmdline(image->cmdline_buf,
+ ima_kexec_cmdline(kernel_fd, image->cmdline_buf,
image->cmdline_buf_len - 1);
}

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index de05d7f1d3ec..ed9307dd0e60 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -251,7 +251,8 @@ 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, const char *keyring);
+ int pcr, struct inode *inode,
+ 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,
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index bf22de8b7ce0..4f39fb93f278 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -162,7 +162,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,

/**
* ima_get_action - appraise & measure decision based on policy.
- * @inode: pointer to inode to measure
+ * @inode: pointer to the inode associated with the object being validated
* @cred: pointer to credentials structure to validate
* @secid: secid of the task being validated
* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index a9649b04b9f1..0c11aeefea24 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -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, NULL);
+ pcr, NULL, NULL);
}

return rc;
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index aaae80c4e376..585b64557094 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
*/
process_buffer_measurement(payload, payload_len,
keyring->description, KEY_CHECK, 0,
- keyring->description);
+ NULL, keyring->description);
}
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index c1583d98c5e5..82acd66bf653 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -731,13 +731,15 @@ 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
+ * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
* @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, const char *keyring)
+ int pcr, struct inode *inode,
+ const char *keyring)
{
int ret = 0;
struct ima_template_entry *entry = NULL;
@@ -767,7 +769,7 @@ 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,
+ action = ima_get_action(inode, current_cred(), secid, 0, func,
&pcr, &template, keyring);
if (!(action & IMA_MEASURE))
return;
@@ -815,16 +817,26 @@ void process_buffer_measurement(const void *buf, int size,

/**
* ima_kexec_cmdline - measure kexec cmdline boot args
+ * @kernel_fd: file descriptor of the kexec kernel being loaded
* @buf: pointer to buffer
* @size: size of buffer
*
* Buffers can only be measured, not appraised.
*/
-void ima_kexec_cmdline(const void *buf, int size)
+void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
{
- if (buf && size != 0)
- process_buffer_measurement(buf, size, "kexec-cmdline",
- KEXEC_CMDLINE, 0, NULL);
+ struct fd f;
+
+ if (!buf || !size)
+ return;
+
+ f = fdget(kernel_fd);
+ if (!f.file)
+ return;
+
+ process_buffer_measurement(buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
+ file_inode(f.file), NULL);
+ fdput(f);
}

static int __init init_ima(void)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 0ca9902287bf..5a6aee530011 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -442,13 +442,9 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
{
int i;

- if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
- if ((rule->flags & IMA_FUNC) && (rule->func == func)) {
- if (func == KEY_CHECK)
- return ima_match_keyring(rule, keyring, cred);
- return true;
- }
- return false;
+ if (func == KEY_CHECK) {
+ return (rule->flags & IMA_FUNC) && (rule->func == func) &&
+ ima_match_keyring(rule, keyring, cred);
}
if ((rule->flags & IMA_FUNC) &&
(rule->func != func && func != POST_SETATTR))
@@ -1003,10 +999,9 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
if (entry->action & ~(MEASURE | DONT_MEASURE))
return false;

- if (entry->flags & ~(IMA_FUNC | IMA_PCR))
- return false;
-
- if (ima_rule_contains_lsm_cond(entry))
+ if (entry->flags & ~(IMA_FUNC | IMA_FSMAGIC | IMA_UID |
+ IMA_FOWNER | IMA_FSUUID |
+ IMA_EUID | IMA_PCR | IMA_FSNAME))
return false;

break;
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index cb3e3f501593..7c69d7397832 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -156,7 +156,7 @@ void ima_process_queued_keys(void)
process_buffer_measurement(entry->payload,
entry->payload_len,
entry->keyring_name,
- KEY_CHECK, 0,
+ KEY_CHECK, 0, NULL,
entry->keyring_name);
list_del(&entry->list);
ima_free_key_entry(entry);
--
2.25.1

Next message: Tyler Hicks: "[PATCH 08/12] ima: Shallow copy the args_p member of ima_rule_entry.lsm elements"
Previous message: Tyler Hicks: "[PATCH 11/12] ima: Use the common function to detect LSM conditionals in a rule"
In reply to: Tyler Hicks: "[PATCH 11/12] ima: Use the common function to detect LSM conditionals in a rule"
Next in thread: Tyler Hicks: "[PATCH 08/12] ima: Shallow copy the args_p member of ima_rule_entry.lsm elements"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]