[PATCH v6 2/4] IMA: Define IMA hooks to measure LSM state and policy

From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
To: zohar@linux.ibm.com, stephen.smalley.work@gmail.com,
	casey@schaufler-ca.com
Cc: tyhicks@linux.microsoft.com, sashal@kernel.org,
	jmorris@namei.org, linux-integrity@vger.kernel.org,
	selinux@vger.kernel.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v6 2/4] IMA: Define IMA hooks to measure LSM state and policy
Date: Tue,  4 Aug 2020 17:43:29 -0700	[thread overview]
Message-ID: <20200805004331.20652-3-nramas@linux.microsoft.com> (raw)
In-Reply-To: <20200805004331.20652-1-nramas@linux.microsoft.com>

IMA subsystem needs to define IMA hooks that the security modules can
call to measure state and policy data.

Define two new IMA hooks, namely ima_lsm_state() and ima_lsm_policy(),
that the security modules can call to measure LSM state and LSM policy
respectively. Return the status of the measurement operation from these
two IMA hooks.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
---
 include/linux/ima.h               | 14 +++++++++
 security/integrity/ima/ima.h      |  6 ++--
 security/integrity/ima/ima_main.c | 50 ++++++++++++++++++++++++++-----
 3 files changed, 60 insertions(+), 10 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index d15100de6cdd..442ca0dce3c8 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 int ima_measure_lsm_state(const char *lsm_event_name, const void *buf,
+				 int size);
+extern int ima_measure_lsm_policy(const char *lsm_event_name, const void *buf,
+				  int size);
 
 #ifdef CONFIG_IMA_KEXEC
 extern void ima_add_kexec_buffer(struct kimage *image);
@@ -104,6 +108,16 @@ 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 int ima_measure_lsm_state(const char *lsm_event_name,
+					const void *buf, int size)
+{
+	return -EOPNOTSUPP;
+}
+static inline int ima_measure_lsm_policy(const char *lsm_event_name,
+					 const void *buf, int size)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 1b5f4b2f17d0..8ed9f5e1dd40 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -267,9 +267,9 @@ 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 inode *inode, const void *buf, int size,
-				const char *eventname, enum ima_hooks func,
-				int pcr, const char *keyring);
+int process_buffer_measurement(struct inode *inode, const void *buf, int size,
+			       const char *eventname, enum ima_hooks func,
+			       int pcr, const char *keyring);
 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 8a91711ca79b..74d421e40c8f 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -736,9 +736,9 @@ int ima_load_data(enum kernel_load_data_id id)
  *
  * Based on policy, the buffer is measured into the ima log.
  */
-void process_buffer_measurement(struct inode *inode, const void *buf, int size,
-				const char *eventname, enum ima_hooks func,
-				int pcr, const char *keyring)
+int process_buffer_measurement(struct inode *inode, const void *buf, int size,
+			       const char *eventname, enum ima_hooks func,
+			       int pcr, const char *keyring)
 {
 	int ret = 0;
 	const char *audit_cause = "ENOMEM";
@@ -758,7 +758,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 	u32 secid;
 
 	if (!ima_policy_flag)
-		return;
+		return 0;
 
 	/*
 	 * Both LSM hooks and auxilary based buffer measurements are
@@ -772,7 +772,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 		action = ima_get_action(inode, current_cred(), secid, 0, func,
 					&pcr, &template, keyring);
 		if (!(action & IMA_MEASURE))
-			return;
+			return 0;
 	}
 
 	if (!pcr)
@@ -787,7 +787,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 			pr_err("template %s init failed, result: %d\n",
 			       (strlen(template->name) ?
 				template->name : template->fmt), ret);
-			return;
+			return ret;
 		}
 	}
 
@@ -819,7 +819,7 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 					func_measure_str(func),
 					audit_cause, ret, 0, ret);
 
-	return;
+	return ret;
 }
 
 /**
@@ -846,6 +846,42 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 	fdput(f);
 }
 
+/**
+ * ima_measure_lsm_state - measure LSM specific state
+ * @lsm_event_name: LSM event
+ * @buf: pointer to buffer containing LSM specific state
+ * @size: Number of bytes in buf
+ *
+ * Buffers can only be measured, not appraised.
+ */
+int ima_measure_lsm_state(const char *lsm_event_name, const void *buf,
+			  int size)
+{
+	if (!lsm_event_name || !buf || !size)
+		return -EINVAL;
+
+	return process_buffer_measurement(NULL, buf, size, lsm_event_name,
+					  LSM_STATE, 0, NULL);
+}
+
+/**
+ * ima_measure_lsm_policy - measure LSM specific policy
+ * @lsm_event_name: LSM event
+ * @buf: pointer to buffer containing LSM specific policy
+ * @size: Number of bytes in buf
+ *
+ * Buffers can only be measured, not appraised.
+ */
+int ima_measure_lsm_policy(const char *lsm_event_name, const void *buf,
+			   int size)
+{
+	if (!lsm_event_name || !buf || !size)
+		return -EINVAL;
+
+	return process_buffer_measurement(NULL, buf, size, lsm_event_name,
+					  LSM_POLICY, 0, NULL);
+}
+
 static int __init init_ima(void)
 {
 	int error;
-- 
2.27.0

