| Message ID | 20200923192011.5293-6-tusharsu@linux.microsoft.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | IMA: Infrastructure for measurement of critical kernel data | expand |
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@linux.microsoft.com> 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
On 2020-10-22 3:35 p.m., Mimi Zohar wrote: > 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@linux.microsoft.com> > > 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. > Sure. I will drop 2/6, and reverse the order of 4/6 and 5/6. >> --- >> 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. > Makes sense. Will do. > >> 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). > Yes. Precisely. For example, in “dm-crypt” case: the data source is “dm-crypt” and possible events are “add_target”, “post_suspend”, "resume" etc. I will add a more detailed hook description as you suggested below, and explain this point in it. > 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. Will add. Thanks Mimi. > > thanks, > > Mimi >
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 diff --git a/include/linux/ima.h b/include/linux/ima.h index d15100de6cdd..4040f484ac63 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -26,6 +26,10 @@ 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 char *event_data_source, + const void *buf, int buf_len, + bool measure_buf_hash); #ifdef CONFIG_IMA_KEXEC extern void ima_add_kexec_buffer(struct kimage *image); @@ -104,6 +108,10 @@ 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 char *event_data_source, + 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 0f77e0b697a3..c1acf88e1b5d 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -200,6 +200,7 @@ 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 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. + */ +void ima_measure_critical_data(const char *event_name, + const char *event_data_source, + const void *buf, int buf_len, + bool measure_buf_hash) +{ + if (!event_name || !event_data_source || !buf || !buf_len) { + pr_err("Invalid arguments passed to %s().\n", __func__); + return; + } + + process_buffer_measurement(NULL, buf, buf_len, event_name, + CRITICAL_DATA, 0, event_data_source, + measure_buf_hash); +} + 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 89452245f54a..491017df7589 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -510,14 +510,23 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, { int i; - if (func == KEY_CHECK) { - return (rule->flags & IMA_FUNC) && (rule->func == func) && - ima_match_rule_data(rule, rule->keyrings, func_data, - true, cred); - } if ((rule->flags & IMA_FUNC) && (rule->func != func && func != POST_SETATTR)) return false; + + switch (func) { + case KEY_CHECK: + return ((rule->func == func) && + ima_match_rule_data(rule, rule->keyrings, + func_data, true, cred)); + case CRITICAL_DATA: + return ((rule->func == func) && + ima_match_rule_data(rule, rule->data_sources, + func_data, false, cred)); + default: + break; + } + if ((rule->flags & IMA_MASK) && (rule->mask != mask && func != POST_SETATTR)) return false; @@ -1113,6 +1122,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) if (ima_rule_contains_lsm_cond(entry)) return false; + break; + case CRITICAL_DATA: + if (entry->action & ~(MEASURE | DONT_MEASURE)) + return false; + + if (!(entry->flags & IMA_DATA_SOURCES) || + (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR | + IMA_DATA_SOURCES))) + return false; + + if (ima_rule_contains_lsm_cond(entry)) + return false; + break; default: return false; @@ -1245,6 +1267,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) && strcmp(args[0].from, "KEY_CHECK") == 0) entry->func = KEY_CHECK; + else if (strcmp(args[0].from, "CRITICAL_DATA") == 0) + entry->func = CRITICAL_DATA; else result = -EINVAL; if (!result)
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@linux.microsoft.com> --- 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(-)