[PATCH v3 1/4] added a new ima policy func buffer_check, and ima hook to measure the buffer hash into ima

Prakhar Srivastava
2019-04-29T21:47:55Z

added a new ima policy func buffer_check, and ima hook to
measure the buffer hash into ima logs.

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
---
Documentation/ABI/testing/ima_policy | 1 +
include/linux/ima.h | 5 ++
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_api.c | 1 +
security/integrity/ima/ima_main.c | 89 ++++++++++++++++++++++++++++
security/integrity/ima/ima_policy.c | 8 +++
6 files changed, 105 insertions(+)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 74c6702de74e..12cfe3ff2dea 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -29,6 +29,7 @@ Description:
base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
+ [BUFFER_CHECK]
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 dc12fbcf484c..f0abade74707 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -26,6 +26,8 @@ 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_buffer_check(const void *buff, int size,
+ const char *eventname);

#ifdef CONFIG_IMA_KEXEC
extern void ima_add_kexec_buffer(struct kimage *image);
@@ -92,6 +94,9 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
return;
}

+static inline void ima_buffer_check(const void *buff, int size,
+ const char *eventname)
+{}
#endif /* CONFIG_IMA */

#ifndef CONFIG_IMA_KEXEC
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d213e835c498..de70df132575 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -184,6 +184,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
hook(KEXEC_KERNEL_CHECK) \
hook(KEXEC_INITRAMFS_CHECK) \
hook(POLICY_CHECK) \
+ hook(BUFFER_CHECK) \
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 c7505fb122d4..cb3f67b366f1 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -169,6 +169,7 @@ 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
+ * | BUFFER_CHECK
* 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 357edd140c09..3db3f3966ac7 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -576,6 +576,95 @@ int ima_load_data(enum kernel_load_data_id id)
return 0;
}

+/*
+ * process_buffer_measurement - Measure the buffer passed to ima log.
+ * (Instead of using the file hash the buffer hash is used).
+ * @buff - The buffer that needs to be added to the log
+ * @size - size of buffer(in bytes)
+ * @eventname - this is eventname used for the various buffers
+ * that can be measured.
+ *
+ * The buffer passed is added to the ima logs.
+ * If the sig template is used, then the sig field contains the buffer.
+ *
+ * On success return 0.
+ * On error cases surface errors from ima calls.
+ */
+static int process_buffer_measurement(const void *buff, int size,
+ const char *eventname, const struct cred *cred,
+ u32 secid)
+{
+ int ret = -EINVAL;
+ struct ima_template_entry *entry = NULL;
+ struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
+ struct ima_event_data event_data = {iint, NULL, NULL,
+ NULL, 0, NULL};
+ struct {
+ struct ima_digest_data hdr;
+ char digest[IMA_MAX_DIGEST_SIZE];
+ } hash;
+ int violation = 0;
+ int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+
+ if (!buff || size == 0 || !eventname)
+ goto err_out;
+
+ if (ima_get_action(NULL, cred, secid, 0, BUFFER_CHECK, &pcr)
+ != IMA_MEASURE)
+ goto err_out;
+
+ memset(iint, 0, sizeof(*iint));
+ memset(&hash, 0, sizeof(hash));
+
+ 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(buff, size, iint->ima_hash);
+ if (ret < 0)
+ goto err_out;
+
+ ret = ima_alloc_init_template(&event_data, &entry);
+ if (ret < 0)
+ goto err_out;
+
+ ret = ima_store_template(entry, violation, NULL,
+ buff, pcr);
+ if (ret < 0) {
+ ima_free_template_entry(entry);
+ goto err_out;
+ }
+
+ return 0;
+
+err_out:
+ pr_err("Error in adding buffer measure: %d\n", ret);
+ return ret;
+}
+
+/**
+ * ima_buffer_check - based on policy, collect & store buffer measurement
+ * @buf: pointer to buffer
+ * @size: size of buffer
+ * @eventname: event name identifier
+ *
+ * Buffers can only be measured, not appraised. The buffer identifier
+ * is used as the measurement list entry name (eg. boot_cmdline).
+ */
+void ima_buffer_check(const void *buf, int size, const char *eventname)
+{
+ u32 secid;
+
+ if (buf && size != 0 && eventname) {
+ security_task_getsecid(current, &secid);
+ process_buffer_measurement(buf, size, eventname,
+ 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 e0cc323f948f..b12551ed191c 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -291,6 +291,12 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
{
int i;

+ // Incase of BUFFER_CHECK, Inode is NULL
+ if (!inode) {
+ 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;
@@ -869,6 +875,8 @@ 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, "BUFFER_CHECK") == 0)
+ entry->func = BUFFER_CHECK;
else
result = -EINVAL;
if (!result)
--
2.19.1