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SubjectRe: [PATCH V9 1/3] IMA:Define a new hook to measure the kexec boot command line arguments
On Mon, Jun 17, 2019 at 11:37 AM Prakhar Srivastava <prsriva02@gmail.com> wrote:
>
> 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.[Suggested by Mimi]
>
> Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
> ---
> Documentation/ABI/testing/ima_policy | 1 +
> include/linux/ima.h | 2 +
> security/integrity/ima/ima.h | 1 +
> security/integrity/ima/ima_api.c | 1 +
> security/integrity/ima/ima_main.c | 74 ++++++++++++++++++++++++++++
> security/integrity/ima/ima_policy.c | 7 +++
> 6 files changed, 86 insertions(+)
>
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index b383c1763610..fc376a323908 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -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
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index fd9f7cf4cdf5..b42f5a006042 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -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
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 18b48a6d0b80..a4ad1270bffa 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -185,6 +185,7 @@ 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,
>
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 78eb11c7ac07..ea7d8cbf712f 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -176,6 +176,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
> * 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
> *
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index af341a80118f..1e233417a7af 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -605,6 +605,80 @@ 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 };
> + 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))
> + goto out;
> +
> + event_data.filename = eventname;
> +
> + 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;
> +
> + if (action & IMA_MEASURE)
> + 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;
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index fd9b01881d17..4e8bb7eecd08 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -292,6 +292,11 @@ 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;
> @@ -880,6 +885,8 @@ 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)
> --
> 2.19.1
>

Hi Mimi,
Can you Ack this patch?
I want to make sure this looks okay to you.

Thanks,
Prakhar Srivastava

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