IMA: Define a new hook to measure the kexec boot command line arguments

Currently during soft reboot(kexec_file_load) boot command line
arguments are not measured. Define hooks needed to measure kexec
command line arguments during soft reboot(kexec_file_load).

- A new ima hook ima_kexec_cmdline is defined to be called by the
kexec code.
- A new function process_buffer_measurement is defined to measure
the buffer hash into the IMA measurement list.
- A new func policy KEXEC_CMDLINE is defined to control the
 measurement.

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Prakhar Srivastava 2019-06-23 23:23:29 -07:00 committed by Mimi Zohar
parent 19453ce0bc
commit b0935123a1
6 changed files with 84 additions and 0 deletions

View File

@ -28,6 +28,7 @@ Description:
base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
[KEXEC_CMDLINE]
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
[[^]MAY_EXEC]
fsmagic:= hex value

View File

@ -26,6 +26,7 @@ extern int ima_read_file(struct file *file, enum kernel_read_file_id id);
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 void ima_kexec_cmdline(const void *buf, int size);
#ifdef CONFIG_IMA_KEXEC
extern void ima_add_kexec_buffer(struct kimage *image);
@ -92,6 +93,7 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
return;
}
static inline void ima_kexec_cmdline(const void *buf, int size) {}
#endif /* CONFIG_IMA */
#ifndef CONFIG_IMA_KEXEC

View File

@ -190,6 +190,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
hook(KEXEC_KERNEL_CHECK) \
hook(KEXEC_INITRAMFS_CHECK) \
hook(POLICY_CHECK) \
hook(KEXEC_CMDLINE) \
hook(MAX_CHECK)
#define __ima_hook_enumify(ENUM) ENUM,

View File

@ -178,6 +178,7 @@ err_out:
* 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
* mask: contains the permission mask
* fsmagic: hex value
*

View File

@ -609,6 +609,78 @@ int ima_load_data(enum kernel_load_data_id id)
return 0;
}
/*
* process_buffer_measurement - Measure the buffer to ima log.
* @buf: pointer to the buffer that needs to be added to the log.
* @size: size of buffer(in bytes).
* @eventname: event name to be used for the buffer entry.
* @cred: a pointer to a credentials structure for user validation.
* @secid: the secid of the task to be validated.
*
* Based on policy, the buffer is measured into the ima log.
*/
static void process_buffer_measurement(const void *buf, int size,
const char *eventname,
const struct cred *cred, u32 secid)
{
int ret = 0;
struct ima_template_entry *entry = NULL;
struct integrity_iint_cache iint = {};
struct ima_event_data event_data = {.iint = &iint,
.filename = eventname};
struct ima_template_desc *template_desc = NULL;
struct {
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} hash = {};
int violation = 0;
int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
int action = 0;
action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
&template_desc);
if (!(action & IMA_MEASURE))
return;
iint.ima_hash = &hash.hdr;
iint.ima_hash->algo = ima_hash_algo;
iint.ima_hash->length = hash_digest_size[ima_hash_algo];
ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
if (ret < 0)
goto out;
ret = ima_alloc_init_template(&event_data, &entry, template_desc);
if (ret < 0)
goto out;
ret = ima_store_template(entry, violation, NULL, buf, pcr);
if (ret < 0)
ima_free_template_entry(entry);
out:
return;
}
/**
* ima_kexec_cmdline - measure kexec cmdline boot args
* @buf: pointer to buffer
* @size: size of buffer
*
* Buffers can only be measured, not appraised.
*/
void ima_kexec_cmdline(const void *buf, int size)
{
u32 secid;
if (buf && size != 0) {
security_task_getsecid(current, &secid);
process_buffer_measurement(buf, size, "kexec-cmdline",
current_cred(), secid);
}
}
static int __init init_ima(void)
{
int error;

View File

@ -374,6 +374,11 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
{
int i;
if (func == KEXEC_CMDLINE) {
if ((rule->flags & IMA_FUNC) && (rule->func == func))
return true;
return false;
}
if ((rule->flags & IMA_FUNC) &&
(rule->func != func && func != POST_SETATTR))
return false;
@ -956,6 +961,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
entry->func = KEXEC_INITRAMFS_CHECK;
else if (strcmp(args[0].from, "POLICY_CHECK") == 0)
entry->func = POLICY_CHECK;
else if (strcmp(args[0].from, "KEXEC_CMDLINE") == 0)
entry->func = KEXEC_CMDLINE;
else
result = -EINVAL;
if (!result)