Hi Tushar, On Wed, 2020-09-23 at 12:20 -0700, Tushar Sugandhi wrote: > Currently, IMA does not provide a generic function for kernel components > to measure their data. A generic function provided by IMA would > enable various parts of the kernel with easier and faster on-boarding to > use IMA infrastructure, would avoid code duplication, and consistent > usage of IMA policy option "data_sources:=" across the kernel. > > Add a new IMA func CRITICAL_DATA and a corresponding IMA hook > ima_measure_critical_data() to support measuring various critical kernel > components. Limit the measurement to the components that are specified > in the IMA policy - CRITICAL_DATA+data_sources. > > Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx> Normally the new LSM or IMA hook is defined before defining a method of constraining that hook. Please drop 2/6 (IMA: conditionally allow empty rule data) and reverse the order of 4/6 and 5/6. That will allow each patch to update the Documentation appropriately, making the change self contained. > --- > Documentation/ABI/testing/ima_policy | 8 ++++++- > include/linux/ima.h | 8 +++++++ > security/integrity/ima/ima.h | 1 + > security/integrity/ima/ima_api.c | 2 +- > security/integrity/ima/ima_main.c | 26 +++++++++++++++++++++ > security/integrity/ima/ima_policy.c | 34 ++++++++++++++++++++++++---- > 6 files changed, 72 insertions(+), 7 deletions(-) > > diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy > index a81cf79fb255..d33bb51309fc 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] [KEY_CHECK] > + [KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA] > mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND] > [[^]MAY_EXEC] > fsmagic:= hex value > @@ -51,6 +51,8 @@ Description: > data_sources:= list of kernel components > (eg, selinux|apparmor|dm-crypt) that contain data critical > to the security of the kernel. > + Only valid when action is "measure" and func is > + CRITICAL_DATA. > > default policy: > # PROC_SUPER_MAGIC > @@ -128,3 +130,7 @@ Description: > keys added to .builtin_trusted_keys or .ima keyring: > > measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima > + > + Example of measure rule using CRITICAL_DATA to measure critical data > + > + measure func=CRITICAL_DATA data_sources=selinux|apparmor|dm-crypt As data sources are added, the documentation example should be updated to reflect the new source. Please do not include examples that don't yet exist. > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index 6888fc372abf..d55896f28790 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -867,6 +867,32 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) > fdput(f); > } > > +/** > + * ima_measure_critical_data - measure critical data > + * @event_name: name for the given data > + * @event_data_source: name of the event data source > + * @buf: pointer to buffer containing data to measure > + * @buf_len: length of buffer(in bytes) > + * @measure_buf_hash: if set to true - will measure hash of the buf, > + * instead of buf > + * > + * Buffers can only be measured, not appraised. > + */ Perhaps the reason for defining both the event_name and event_data_source will become clearer with an example. At this point I can only guess as to why both are needed (e.g. perhaps a data source defines multiple events). While "Buffers can only be measured, not appraised" is true, it was cut & pasted from ima_kexec_cmdline. Measuring the kexec boot cmdline is self describing. Here, a larger, more detailed IMA hook description would be appropriate. thanks, Mimi
