[PATCH v5 03/12] S.A.R.A.: cred blob management

[Salvatore Mesoraca]

Creation of the S.A.R.A. cred blob management "API".
In order to allow S.A.R.A. to be stackable with other LSMs, it doesn't use
the "security" field of struct cred, instead it uses an ad hoc field named
security_sara.
This solution is probably not acceptable for upstream, so this part will
be modified as soon as the LSM stackable cred blob management will be
available.

Signed-off-by: Salvatore Mesoraca <s.mesoraca16 at gmail.com>
---
 security/sara/Makefile            |  2 +-
 security/sara/include/sara_data.h | 84 +++++++++++++++++++++++++++++++++++++++
 security/sara/main.c              |  7 ++++
 security/sara/sara_data.c         | 69 ++++++++++++++++++++++++++++++++
 4 files changed, 161 insertions(+), 1 deletion(-)
 create mode 100644 security/sara/include/sara_data.h
 create mode 100644 security/sara/sara_data.c

diff --git a/security/sara/Makefile b/security/sara/Makefile
index 8acd291..14bf7a8 100644
--- a/security/sara/Makefile
+++ b/security/sara/Makefile
@@ -1,3 +1,3 @@
 obj-$(CONFIG_SECURITY_SARA) := sara.o
 
-sara-y := main.o securityfs.o utils.o
+sara-y := main.o securityfs.o utils.o sara_data.o
diff --git a/security/sara/include/sara_data.h b/security/sara/include/sara_data.h
new file mode 100644
index 0000000..9216c47
--- /dev/null
+++ b/security/sara/include/sara_data.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * S.A.R.A. Linux Security Module
+ *
+ * Copyright (C) 2017 Salvatore Mesoraca <s.mesoraca16 at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#ifndef __SARA_DATA_H
+#define __SARA_DATA_H
+
+#include <linux/cred.h>
+#include <linux/init.h>
+#include <linux/lsm_hooks.h>
+#include <linux/spinlock.h>
+
+int sara_data_init(void) __init;
+
+extern struct lsm_blob_sizes sara_blob_sizes __lsm_ro_after_init;
+
+#ifdef CONFIG_SECURITY_SARA_WXPROT
+
+struct sara_data {
+	unsigned long	relro_page;
+	struct file	*relro_file;
+	u16		wxp_flags;
+	u16		execve_flags;
+	bool		relro_page_found;
+	bool		mmap_blocked;
+};
+
+struct sara_shm_data {
+	bool		no_exec;
+	bool		no_write;
+	spinlock_t	lock;
+};
+
+
+static inline struct sara_data *get_sara_data(const struct cred *cred)
+{
+	return cred->security + sara_blob_sizes.lbs_cred;
+}
+
+#define get_current_sara_data() get_sara_data(current_cred())
+
+#define get_sara_wxp_flags(X) (get_sara_data((X))->wxp_flags)
+#define get_current_sara_wxp_flags() get_sara_wxp_flags(current_cred())
+
+#define get_sara_execve_flags(X) (get_sara_data((X))->execve_flags)
+#define get_current_sara_execve_flags() get_sara_execve_flags(current_cred())
+
+#define get_sara_relro_page(X) (get_sara_data((X))->relro_page)
+#define get_current_sara_relro_page() get_sara_relro_page(current_cred())
+
+#define get_sara_relro_file(X) (get_sara_data((X))->relro_file)
+#define get_current_sara_relro_file() get_sara_relro_file(current_cred())
+
+#define get_sara_relro_page_found(X) (get_sara_data((X))->relro_page_found)
+#define get_current_sara_relro_page_found() \
+	get_sara_relro_page_found(current_cred())
+
+#define get_sara_mmap_blocked(X) (get_sara_data((X))->mmap_blocked)
+#define get_current_sara_mmap_blocked() get_sara_mmap_blocked(current_cred())
+
+
+static inline struct sara_shm_data *get_sara_shm_data(
+					const struct kern_ipc_perm *ipc)
+{
+	return ipc->security + sara_blob_sizes.lbs_ipc;
+}
+
+#define get_sara_shm_no_exec(X) (get_sara_shm_data((X))->no_exec)
+#define get_sara_shm_no_write(X) (get_sara_shm_data((X))->no_write)
+#define lock_sara_shm(X) (spin_lock(&get_sara_shm_data((X))->lock))
+#define unlock_sara_shm(X) (spin_unlock(&get_sara_shm_data((X))->lock))
+
+#endif
+
+#endif /* __SARA_H */
diff --git a/security/sara/main.c b/security/sara/main.c
index 52e6d18..dc5dda4 100644
--- a/security/sara/main.c
+++ b/security/sara/main.c
@@ -18,6 +18,7 @@
 #include <linux/printk.h>
 
 #include "include/sara.h"
+#include "include/sara_data.h"
 #include "include/securityfs.h"
 
 static const int sara_version = SARA_VERSION;
@@ -93,6 +94,11 @@ static int __init sara_init(void)
 		goto error;
 	}
 
+	if (sara_data_init()) {
+		pr_crit("impossible to initialize creds.\n");
+		goto error;
+	}
+
 	pr_debug("initialized.\n");
 
 	if (sara_enabled)
@@ -112,4 +118,5 @@ static int __init sara_init(void)
 	.name = "sara",
 	.enabled = &sara_enabled,
 	.init = sara_init,
+	.blobs = &sara_blob_sizes,
 };
diff --git a/security/sara/sara_data.c b/security/sara/sara_data.c
new file mode 100644
index 0000000..9afca37
--- /dev/null
+++ b/security/sara/sara_data.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * S.A.R.A. Linux Security Module
+ *
+ * Copyright (C) 2017 Salvatore Mesoraca <s.mesoraca16 at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include "include/sara_data.h"
+
+#ifdef CONFIG_SECURITY_SARA_WXPROT
+#include <linux/cred.h>
+#include <linux/lsm_hooks.h>
+#include <linux/mm.h>
+#include <linux/spinlock.h>
+
+static int sara_cred_prepare(struct cred *new, const struct cred *old,
+			     gfp_t gfp)
+{
+	*get_sara_data(new) = *get_sara_data(old);
+	return 0;
+}
+
+static void sara_cred_transfer(struct cred *new, const struct cred *old)
+{
+	*get_sara_data(new) = *get_sara_data(old);
+}
+
+static int sara_shm_alloc_security(struct kern_ipc_perm *shp)
+{
+	struct sara_shm_data *d;
+
+	d = get_sara_shm_data(shp);
+	spin_lock_init(&d->lock);
+	return 0;
+}
+
+static struct security_hook_list data_hooks[] __lsm_ro_after_init = {
+	LSM_HOOK_INIT(cred_prepare, sara_cred_prepare),
+	LSM_HOOK_INIT(cred_transfer, sara_cred_transfer),
+	LSM_HOOK_INIT(shm_alloc_security, sara_shm_alloc_security),
+};
+
+struct lsm_blob_sizes sara_blob_sizes __lsm_ro_after_init = {
+	.lbs_cred = sizeof(struct sara_data),
+	.lbs_ipc = sizeof(struct sara_shm_data),
+};
+
+int __init sara_data_init(void)
+{
+	security_add_hooks(data_hooks, ARRAY_SIZE(data_hooks), "sara");
+	return 0;
+}
+
+#else /* CONFIG_SECURITY_SARA_WXPROT */
+
+struct lsm_blob_sizes sara_blob_sizes __lsm_ro_after_init = { };
+
+int __init sara_data_init(void)
+{
+	return 0;
+}
+
+#endif
-- 
1.9.1