linux-kernel - [PATCH v6 6/8] IMA: add support to critical data hook to limit data sources for measurement

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Date:   Thu, 19 Nov 2020 15:26:09 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     zohar@...ux.ibm.com, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com, paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: [PATCH v6 6/8] IMA: add support to critical data hook to limit data sources for measurement

The IMA hook ima_measure_critical_data() does not support a way to
specify the source of the critical data provider. Thus, the data
measurement cannot be constrained, based on the data source, through the
IMA policy.

Extend the IMA hook ima_measure_critical_data() to support passing 
the data source name as an input parameter, so that the policy rule can
be used to limit data sources being measured.

Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
---
 include/linux/ima.h               |  6 ++++--
 security/integrity/ima/ima_main.c | 11 ++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 9911a6e496b6..60ba073f1575 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -30,7 +30,8 @@ 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,
+extern void ima_measure_critical_data(const char *event_data_source,
+				      const char *event_name,
 				      const void *buf, int buf_len,
 				      bool measure_buf_hash);
 
@@ -119,7 +120,8 @@ 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,
+static inline void ima_measure_critical_data(const char *event_data_source,
+					     const char *event_name,
 					     const void *buf, int buf_len,
 					     bool measure_buf_hash) {}
 #endif /* CONFIG_IMA */
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 7661f09569f3..27b8b8316622 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -924,6 +924,7 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 
 /**
  * ima_measure_critical_data - measure kernel integrity critical data
+ * @event_data_source: kernel data source being measured
  * @event_name: event name to be used for the buffer entry
  * @buf: pointer to buffer containing data to measure
  * @buf_len: length of buffer(in bytes)
@@ -932,6 +933,9 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
  * Measure the kernel subsystem data, critical to the integrity of the kernel,
  * into the IMA log and extend the @pcr.
  *
+ * Use @event_data_source to describe the kernel data source for the buffer
+ * being measured.
+ *
  * Use @event_name to describe the state/buffer data change.
  * Examples of critical data (buf) could be kernel in-memory r/o structures,
  * hash of the memory structures, or data that represents subsystem state
@@ -944,17 +948,18 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
  *
  * The data (buf) can only be measured, not appraised.
  */
-void ima_measure_critical_data(const char *event_name,
+void ima_measure_critical_data(const char *event_data_source,
+			       const char *event_name,
 			       const void *buf, int buf_len,
 			       bool measure_buf_hash)
 {
-	if (!event_name || !buf || !buf_len) {
+	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, NULL,
+				   CRITICAL_DATA, 0, event_data_source,
 				   measure_buf_hash);
 }
 
-- 
2.17.1