On 2020-12-11 15:58:02, Tushar Sugandhi wrote:
> IMA provides capabilities to measure file data, and in-memory buffer
> data. However, various data structures, policies, and states
> stored in kernel memory also impact the integrity of the system.
> Several kernel subsystems contain such integrity critical data. These
> kernel subsystems help protect the integrity of a device. Currently,
> IMA does not provide a generic function for kernel subsystems to measure
> their integrity critical data.
>
> Define a new IMA hook - ima_measure_critical_data to measure kernel
> integrity critical data.
>
> Signed-off-by: Tushar Sugandhi <tusha...@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhi...@linux.microsoft.com>
Tyler
> ---
> include/linux/ima.h | 6 ++++++
> security/integrity/ima/ima.h | 1 +
> security/integrity/ima/ima_api.c | 2 +-
> security/integrity/ima/ima_main.c | 34 +++++++++++++++++++++++++++++++
> 4 files changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index ac3d82f962f2..675f54db6264 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -30,6 +30,9 @@ extern int ima_post_read_file(struct file *file, void *buf,
> loff_t size,
> 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(int kernel_fd, const void *buf, int size);
> +extern void ima_measure_critical_data(const char *event_name,
> + const void *buf, int buf_len,
> + bool measure_buf_hash);
>
> #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
> extern void ima_appraise_parse_cmdline(void);
> @@ -122,6 +125,9 @@ static inline int ima_file_hash(struct file *file, char
> *buf, size_t buf_size)
> }
>
> static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int
> size) {}
> +static inline void ima_measure_critical_data(const char *event_name,
> + const void *buf, int buf_len,
> + bool measure_buf_hash) {}
> #endif /* CONFIG_IMA */
>
> #ifndef CONFIG_IMA_KEXEC
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index fa3044a7539f..7d9deda6a8b3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -201,6 +201,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
> hook(POLICY_CHECK, policy) \
> hook(KEXEC_CMDLINE, kexec_cmdline) \
> hook(KEY_CHECK, key) \
> + hook(CRITICAL_DATA, critical_data) \
> hook(MAX_CHECK, none)
>
> #define __ima_hook_enumify(ENUM, str) ENUM,
> diff --git a/security/integrity/ima/ima_api.c
> b/security/integrity/ima/ima_api.c
> index af218babd198..9917e1730cb6 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -176,7 +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 | KEY_CHECK
> + * | KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
> * 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 0f8409d77602..dff4bce4fb09 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -922,6 +922,40 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf,
> int size)
> fdput(f);
> }
>
> +/**
> + * ima_measure_critical_data - measure kernel integrity critical data
> + * @event_name: event name to be used for the buffer entry
> + * @buf: pointer to buffer containing data to measure
> + * @buf_len: length of buffer(in bytes)
> + * @measure_buf_hash: measure buffer hash
> + *
> + * Measure the kernel subsystem data, critical to the integrity of the
> kernel,
> + * into the IMA log and extend the @pcr.
> + *
> + * Use @event_name to describe the state/buffer data change.
> + * Examples of critical data (@buf) could be various data structures,
> + * policies, and states stored in kernel memory that can impact the integrity
> + * of the system.
> + *
> + * If @measure_buf_hash is set to true - measure hash of the buffer data,
> + * else measure the buffer data itself.
> + * @measure_buf_hash can be used to save space, if the data being measured
> + * is too large.
> + *
> + * The data (@buf) can only be measured, not appraised.
> + */
> +void ima_measure_critical_data(const char *event_name,
> + const void *buf, int buf_len,
> + bool measure_buf_hash)
> +{
> + if (!event_name || !buf || !buf_len)
> + return;
> +
> + process_buffer_measurement(NULL, buf, buf_len, event_name,
> + CRITICAL_DATA, 0, NULL,
> + measure_buf_hash);
> +}
> +
> static int __init init_ima(void)
> {
> int error;
> --
> 2.17.1
>
