| Message ID | 20210705090922.3321178-3-roberto.sassu@huawei.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | ima: Provide more info about buffer measurement | expand |
On 7/5/2021 2:09 AM, Roberto Sassu wrote: > ima_measure_critical_data() and process_buffer_measurement() currently > don't return a result. A caller wouldn't be able to know whether those > functions were executed successfully. > > This patch modifies the return type from void to int, and returns 0 if the > buffer has been successfully measured, a negative value otherwise. > > Also, this patch does not modify the behavior of existing callers by > processing the returned value. For those, the return value is ignored. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > include/linux/ima.h | 15 +++++++----- > security/integrity/ima/ima.h | 10 ++++---- > security/integrity/ima/ima_main.c | 40 ++++++++++++++++++------------- > 3 files changed, 37 insertions(+), 28 deletions(-) Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> -lakshmi > > diff --git a/include/linux/ima.h b/include/linux/ima.h > index 81e830d01ced..60492263aa64 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -35,10 +35,10 @@ extern void ima_post_path_mknod(struct user_namespace *mnt_userns, > extern int ima_file_hash(struct file *file, char *buf, size_t buf_size); > extern int ima_inode_hash(struct inode *inode, 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_label, > - const char *event_name, > - const void *buf, size_t buf_len, > - bool hash); > +extern int ima_measure_critical_data(const char *event_label, > + const char *event_name, > + const void *buf, size_t buf_len, > + bool hash); > > #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM > extern void ima_appraise_parse_cmdline(void); > @@ -144,10 +144,13 @@ static inline int ima_inode_hash(struct inode *inode, 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_label, > +static inline int ima_measure_critical_data(const char *event_label, > const char *event_name, > const void *buf, size_t buf_len, > - bool hash) {} > + bool hash) > +{ > + return -ENOENT; > +} > > #endif /* CONFIG_IMA */ > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > index f0e448ed1f9f..03db221324c3 100644 > --- a/security/integrity/ima/ima.h > +++ b/security/integrity/ima/ima.h > @@ -264,11 +264,11 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file, > struct evm_ima_xattr_data *xattr_value, > int xattr_len, const struct modsig *modsig, int pcr, > struct ima_template_desc *template_desc); > -void process_buffer_measurement(struct user_namespace *mnt_userns, > - struct inode *inode, const void *buf, int size, > - const char *eventname, enum ima_hooks func, > - int pcr, const char *func_data, > - bool buf_hash); > +int process_buffer_measurement(struct user_namespace *mnt_userns, > + struct inode *inode, const void *buf, int size, > + const char *eventname, enum ima_hooks func, > + int pcr, const char *func_data, > + bool buf_hash); > void ima_audit_measurement(struct integrity_iint_cache *iint, > const unsigned char *filename); > int ima_alloc_init_template(struct ima_event_data *event_data, > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index 8ef1fa357e0c..b512c06d8ee1 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -827,7 +827,7 @@ int ima_post_load_data(char *buf, loff_t size, > return 0; > } > > -/* > +/** > * process_buffer_measurement - Measure the buffer or the buffer data hash > * @mnt_userns: user namespace of the mount the inode was found from > * @inode: inode associated with the object being measured (NULL for KEY_CHECK) > @@ -840,12 +840,15 @@ int ima_post_load_data(char *buf, loff_t size, > * @buf_hash: measure buffer data hash > * > * Based on policy, either the buffer data or buffer data hash is measured > + * > + * Return: 0 if the buffer has been successfully measured, a negative value > + * otherwise. > */ > -void process_buffer_measurement(struct user_namespace *mnt_userns, > - struct inode *inode, const void *buf, int size, > - const char *eventname, enum ima_hooks func, > - int pcr, const char *func_data, > - bool buf_hash) > +int process_buffer_measurement(struct user_namespace *mnt_userns, > + struct inode *inode, const void *buf, int size, > + const char *eventname, enum ima_hooks func, > + int pcr, const char *func_data, > + bool buf_hash) > { > int ret = 0; > const char *audit_cause = "ENOMEM"; > @@ -867,7 +870,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, > u32 secid; > > if (!ima_policy_flag) > - return; > + return -ENOENT; > > template = ima_template_desc_buf(); > if (!template) { > @@ -889,7 +892,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, > secid, 0, func, &pcr, &template, > func_data); > if (!(action & IMA_MEASURE)) > - return; > + return -ENOENT; > } > > if (!pcr) > @@ -937,7 +940,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, > func_measure_str(func), > audit_cause, ret, 0, ret); > > - return; > + return ret; > } > > /** > @@ -977,18 +980,21 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) > * and extend the pcr. Examples of critical data could be various data > * structures, policies, and states stored in kernel memory that can > * impact the integrity of the system. > + * > + * Return: 0 if the buffer has been successfully measured, a negative value > + * otherwise. > */ > -void ima_measure_critical_data(const char *event_label, > - const char *event_name, > - const void *buf, size_t buf_len, > - bool hash) > +int ima_measure_critical_data(const char *event_label, > + const char *event_name, > + const void *buf, size_t buf_len, > + bool hash) > { > if (!event_name || !event_label || !buf || !buf_len) > - return; > + return -ENOPARAM; > > - process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, event_name, > - CRITICAL_DATA, 0, event_label, > - hash); > + return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, > + event_name, CRITICAL_DATA, 0, > + event_label, hash); > } > > static int __init init_ima(void) >
Hi Roberto, On Mon, 2021-07-05 at 11:09 +0200, Roberto Sassu wrote: > ima_measure_critical_data() and process_buffer_measurement() currently > don't return a result. A caller wouldn't be able to know whether those > functions were executed successfully. Missing is an explanation as to why these functions aren't currently returning a result. The LSM/IMA hooks only return a negative result for failure to appraise a file's integrity, not measure a file. Only failure to appraise a file's integrity results in preventing the file from being read/executed/mmaped. Other failures are only audited. > > This patch modifies the return type from void to int, and returns 0 if the > buffer has been successfully measured, a negative value otherwise. Needed here is an explanation as to why ima_measure_critical_data() is special. > > Also, this patch does not modify the behavior of existing callers by > processing the returned value. For those, the return value is ignored. I agree that the existing behavior shouldn't change, but will this result in the bots complaining? thanks, Mimi
> From: Mimi Zohar [mailto:zohar@linux.ibm.com] > Sent: Monday, July 19, 2021 10:28 PM > Hi Roberto, > > On Mon, 2021-07-05 at 11:09 +0200, Roberto Sassu wrote: > > ima_measure_critical_data() and process_buffer_measurement() currently > > don't return a result. A caller wouldn't be able to know whether those > > functions were executed successfully. > > Missing is an explanation as to why these functions aren't currently > returning a result. The LSM/IMA hooks only return a negative result > for failure to appraise a file's integrity, not measure a file. Only > failure to appraise a file's integrity results in preventing the file > from being read/executed/mmaped. Other failures are only audited. Hi Mimi ok, will add it. > > This patch modifies the return type from void to int, and returns 0 if the > > buffer has been successfully measured, a negative value otherwise. > > Needed here is an explanation as to why ima_measure_critical_data() is > special. We don't want to unnecessarily calculate the digest twice. > > Also, this patch does not modify the behavior of existing callers by > > processing the returned value. For those, the return value is ignored. > > I agree that the existing behavior shouldn't change, but will this > result in the bots complaining? If I remember correctly, I didn't get any error even with W=1. Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > thanks, > > Mimi
On Tue, 2021-07-20 at 12:38 +0000, Roberto Sassu wrote: > > > This patch modifies the return type from void to int, and returns 0 if the > > > buffer has been successfully measured, a negative value otherwise. > > > > Needed here is an explanation as to why ima_measure_critical_data() is > > special. > > We don't want to unnecessarily calculate the digest twice. That's what the "iint" cache is for. . This needs more a of an explaintion as to why ima_measure_critical_data() is special. thanks, Mimi
diff --git a/include/linux/ima.h b/include/linux/ima.h index 81e830d01ced..60492263aa64 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -35,10 +35,10 @@ extern void ima_post_path_mknod(struct user_namespace *mnt_userns, extern int ima_file_hash(struct file *file, char *buf, size_t buf_size); extern int ima_inode_hash(struct inode *inode, 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_label, - const char *event_name, - const void *buf, size_t buf_len, - bool hash); +extern int ima_measure_critical_data(const char *event_label, + const char *event_name, + const void *buf, size_t buf_len, + bool hash); #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM extern void ima_appraise_parse_cmdline(void); @@ -144,10 +144,13 @@ static inline int ima_inode_hash(struct inode *inode, 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_label, +static inline int ima_measure_critical_data(const char *event_label, const char *event_name, const void *buf, size_t buf_len, - bool hash) {} + bool hash) +{ + return -ENOENT; +} #endif /* CONFIG_IMA */ diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index f0e448ed1f9f..03db221324c3 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -264,11 +264,11 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file, struct evm_ima_xattr_data *xattr_value, int xattr_len, const struct modsig *modsig, int pcr, struct ima_template_desc *template_desc); -void process_buffer_measurement(struct user_namespace *mnt_userns, - struct inode *inode, const void *buf, int size, - const char *eventname, enum ima_hooks func, - int pcr, const char *func_data, - bool buf_hash); +int process_buffer_measurement(struct user_namespace *mnt_userns, + struct inode *inode, const void *buf, int size, + const char *eventname, enum ima_hooks func, + int pcr, const char *func_data, + bool buf_hash); void ima_audit_measurement(struct integrity_iint_cache *iint, const unsigned char *filename); int ima_alloc_init_template(struct ima_event_data *event_data, diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 8ef1fa357e0c..b512c06d8ee1 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -827,7 +827,7 @@ int ima_post_load_data(char *buf, loff_t size, return 0; } -/* +/** * process_buffer_measurement - Measure the buffer or the buffer data hash * @mnt_userns: user namespace of the mount the inode was found from * @inode: inode associated with the object being measured (NULL for KEY_CHECK) @@ -840,12 +840,15 @@ int ima_post_load_data(char *buf, loff_t size, * @buf_hash: measure buffer data hash * * Based on policy, either the buffer data or buffer data hash is measured + * + * Return: 0 if the buffer has been successfully measured, a negative value + * otherwise. */ -void process_buffer_measurement(struct user_namespace *mnt_userns, - struct inode *inode, const void *buf, int size, - const char *eventname, enum ima_hooks func, - int pcr, const char *func_data, - bool buf_hash) +int process_buffer_measurement(struct user_namespace *mnt_userns, + struct inode *inode, const void *buf, int size, + const char *eventname, enum ima_hooks func, + int pcr, const char *func_data, + bool buf_hash) { int ret = 0; const char *audit_cause = "ENOMEM"; @@ -867,7 +870,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, u32 secid; if (!ima_policy_flag) - return; + return -ENOENT; template = ima_template_desc_buf(); if (!template) { @@ -889,7 +892,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, secid, 0, func, &pcr, &template, func_data); if (!(action & IMA_MEASURE)) - return; + return -ENOENT; } if (!pcr) @@ -937,7 +940,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns, func_measure_str(func), audit_cause, ret, 0, ret); - return; + return ret; } /** @@ -977,18 +980,21 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) * and extend the pcr. Examples of critical data could be various data * structures, policies, and states stored in kernel memory that can * impact the integrity of the system. + * + * Return: 0 if the buffer has been successfully measured, a negative value + * otherwise. */ -void ima_measure_critical_data(const char *event_label, - const char *event_name, - const void *buf, size_t buf_len, - bool hash) +int ima_measure_critical_data(const char *event_label, + const char *event_name, + const void *buf, size_t buf_len, + bool hash) { if (!event_name || !event_label || !buf || !buf_len) - return; + return -ENOPARAM; - process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, event_name, - CRITICAL_DATA, 0, event_label, - hash); + return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, + event_name, CRITICAL_DATA, 0, + event_label, hash); } static int __init init_ima(void)
ima_measure_critical_data() and process_buffer_measurement() currently don't return a result. A caller wouldn't be able to know whether those functions were executed successfully. This patch modifies the return type from void to int, and returns 0 if the buffer has been successfully measured, a negative value otherwise. Also, this patch does not modify the behavior of existing callers by processing the returned value. For those, the return value is ignored. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- include/linux/ima.h | 15 +++++++----- security/integrity/ima/ima.h | 10 ++++---- security/integrity/ima/ima_main.c | 40 ++++++++++++++++++------------- 3 files changed, 37 insertions(+), 28 deletions(-)