IMA: Define a new hook to measure the kexec boot command line arguments

Currently during soft reboot(kexec_file_load) boot command line
arguments are not measured. Define hooks needed to measure kexec
command line arguments during soft reboot(kexec_file_load).

- A new ima hook ima_kexec_cmdline is defined to be called by the
kexec code.
- A new function process_buffer_measurement is defined to measure
the buffer hash into the IMA measurement list.
- A new func policy KEXEC_CMDLINE is defined to control the
 measurement.

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

6 files changed, 84 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index b383c1763610..fc376a323908 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -28,6 +28,7 @@ Description:
                 base:   func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
                                 [FIRMWARE_CHECK]
                                 [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
+                                [KEXEC_CMDLINE]
                         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 fd9f7cf4cdf5..b42f5a006042 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -26,6 +26,7 @@ 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_kexec_cmdline(const void *buf, int size);
 
 #ifdef CONFIG_IMA_KEXEC
 extern void ima_add_kexec_buffer(struct kimage *image);
@@ -92,6 +93,7 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
         return;
 }
 
+static inline void ima_kexec_cmdline(const void *buf, int size) {}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e7b9ea7732d9..bdca641f9e51 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -190,6 +190,7 @@ static inline unsigned long ima_hash_key(u8 *digest)
         hook(KEXEC_KERNEL_CHECK)        \
         hook(KEXEC_INITRAMFS_CHECK)     \
         hook(POLICY_CHECK)              \
+        hook(KEXEC_CMDLINE)             \
         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 c0cf4bcfc82f..d426d4d1fe04 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -178,6 +178,7 @@ err_out:
  *              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
  *      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 a7e7e2d7224c..2507bee1b762 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -609,6 +609,78 @@ int ima_load_data(enum kernel_load_data_id id)
         return 0;
 }
 
+/*
+ * process_buffer_measurement - Measure the buffer to ima log.
+ * @buf: pointer to the buffer that needs to be added to the log.
+ * @size: size of buffer(in bytes).
+ * @eventname: event name to be used for the buffer entry.
+ * @cred: a pointer to a credentials structure for user validation.
+ * @secid: the secid of the task to be validated.
+ *
+ * Based on policy, the buffer is measured into the ima log.
+ */
+static void process_buffer_measurement(const void *buf, int size,
+                                       const char *eventname,
+                                       const struct cred *cred, u32 secid)
+{
+        int ret = 0;
+        struct ima_template_entry *entry = NULL;
+        struct integrity_iint_cache iint = {};
+        struct ima_event_data event_data = {.iint = &iint,
+                                            .filename = eventname};
+        struct ima_template_desc *template_desc = NULL;
+        struct {
+                struct ima_digest_data hdr;
+                char digest[IMA_MAX_DIGEST_SIZE];
+        } hash = {};
+        int violation = 0;
+        int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+        int action = 0;
+
+        action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
+                                &template_desc);
+        if (!(action & IMA_MEASURE))
+                return;
+
+        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(buf, size, iint.ima_hash);
+        if (ret < 0)
+                goto out;
+
+        ret = ima_alloc_init_template(&event_data, &entry, template_desc);
+        if (ret < 0)
+                goto out;
+
+        ret = ima_store_template(entry, violation, NULL, buf, pcr);
+
+        if (ret < 0)
+                ima_free_template_entry(entry);
+
+out:
+        return;
+}
+
+/**
+ * ima_kexec_cmdline - measure kexec cmdline boot args
+ * @buf: pointer to buffer
+ * @size: size of buffer
+ *
+ * Buffers can only be measured, not appraised.
+ */
+void ima_kexec_cmdline(const void *buf, int size)
+{
+        u32 secid;
+
+        if (buf && size != 0) {
+                security_task_getsecid(current, &secid);
+                process_buffer_measurement(buf, size, "kexec-cmdline",
+                                           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 98c289559079..a3058b03a955 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -374,6 +374,11 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 {
         int i;
 
+        if (func == KEXEC_CMDLINE) {
+                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;
@@ -956,6 +961,8 @@ 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, "KEXEC_CMDLINE") == 0)
+                                entry->func = KEXEC_CMDLINE;
                         else
                                 result = -EINVAL;
                         if (!result)