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From: Casey Schaufler <casey@schaufler-ca.com>
To: LSM <linux-security-module@vger.kernel.org>,
	LKLM <linux-kernel@vger.kernel.org>,
	Paul Moore <paul@paul-moore.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	SE Linux <selinux@tycho.nsa.gov>,
	"SMACK-discuss@lists.01.org" <SMACK-discuss@lists.01.org>,
	John Johansen <john.johansen@canonical.com>,
	Kees Cook <keescook@chromium.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	James Morris <jmorris@namei.org>
Subject: [PATCH 01/23] procfs: add smack subdir to attrs
Date: Thu, 10 May 2018 17:52:06 -0700	[thread overview]
Message-ID: <fcc51e4a-b0dc-bbd2-d98a-52b0835bbe31@schaufler-ca.com> (raw)
In-Reply-To: <7e8702ce-2598-e0a3-31a2-bc29157fb73d@schaufler-ca.com>

From: Casey Schaufler <casey@schaufler-ca.com>
Date: Thu, 10 May 2018 13:26:52 -0700
Subject: [PATCH 01/23] procfs: add smack subdir to attrs

Back in 2007 I made what turned out to be a rather serious
mistake in the implementation of the Smack security module.
The SELinux module used an interface in /proc to manipulate
the security context on processes. Rather than use a similar
interface, I used the same interface. The AppArmor team did
likewise. Now /proc/.../attr/current will tell you the
security "context" of the process, but it will be different
depending on the security module you're using.

This patch provides a subdirectory in /proc/.../attr for
Smack. Smack user space can use the "current" file in
this subdirectory and never have to worry about getting
SELinux attributes by mistake. Programs that use the
old interface will continue to work (or fail, as the case
may be) as before.

The original implementation is by Kees Cook.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/admin-guide/LSM/index.rst | 13 +++++--
 fs/proc/base.c                          | 63 ++++++++++++++++++++++++++++-----
 fs/proc/internal.h                      |  1 +
 include/linux/security.h                | 15 +++++---
 security/security.c                     | 24 ++++++++++---
 5 files changed, 95 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst
index c980dfe9abf1..9842e21afd4a 100644
--- a/Documentation/admin-guide/LSM/index.rst
+++ b/Documentation/admin-guide/LSM/index.rst
@@ -17,9 +17,8 @@ MAC extensions, other extensions can be built using the LSM to provide
 specific changes to system operation when these tweaks are not available
 in the core functionality of Linux itself.
 
-Without a specific LSM built into the kernel, the default LSM will be the
-Linux capabilities system. Most LSMs choose to extend the capabilities
-system, building their checks on top of the defined capability hooks.
+The Linux capabilities modules will always be included. This may be
+followed by any number of "minor" modules and at most one "major" module.
 For more details on capabilities, see ``capabilities(7)`` in the Linux
 man-pages project.
 
@@ -30,6 +29,14 @@ order in which checks are made. The capability module will always
 be first, followed by any "minor" modules (e.g. Yama) and then
 the one "major" module (e.g. SELinux) if there is one configured.
 
+Process attributes associated with "major" security modules should
+be accessed and maintained using the special files in ``/proc/.../attr``.
+A security module may maintain a module specific subdirectory there,
+named after the module. ``/proc/.../attr/smack`` is provided by the Smack
+security module and contains all its special files. The files directly
+in ``/proc/.../attr`` remain as legacy interfaces for modules that provide
+subdirectories.
+
 .. toctree::
    :maxdepth: 1
 
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1b2ede6abcdf..fa1681a0b75e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -140,9 +140,13 @@ struct pid_entry {
 #define REG(NAME, MODE, fops)				\
 	NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
 #define ONE(NAME, MODE, show)				\
-	NOD(NAME, (S_IFREG|(MODE)), 			\
+	NOD(NAME, (S_IFREG|(MODE)),			\
 		NULL, &proc_single_file_operations,	\
 		{ .proc_show = show } )
+#define ATTR(LSM, NAME, MODE)				\
+	NOD(NAME, (S_IFREG|(MODE)),			\
+		NULL, &proc_pid_attr_operations,	\
+		{ .lsm = LSM })
 
 /*
  * Count the number of hardlinks for the pid_entry table, excluding the .
@@ -2536,7 +2540,7 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
 	if (!task)
 		return -ESRCH;
 
-	length = security_getprocattr(task,
+	length = security_getprocattr(task, PROC_I(inode)->op.lsm,
 				      (char*)file->f_path.dentry->d_name.name,
 				      &p);
 	put_task_struct(task);
@@ -2582,7 +2586,8 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
 	if (length < 0)
 		goto out_free;
 
-	length = security_setprocattr(file->f_path.dentry->d_name.name,
+	length = security_setprocattr(PROC_I(inode)->op.lsm,
+				      file->f_path.dentry->d_name.name,
 				      page, count);
 	mutex_unlock(&current->signal->cred_guard_mutex);
 out_free:
@@ -2599,13 +2604,53 @@ static const struct file_operations proc_pid_attr_operations = {
 	.llseek		= generic_file_llseek,
 };
 
+#define LSM_DIR_OPS(LSM) \
+static int proc_##LSM##_attr_dir_iterate(struct file *filp, \
+			     struct dir_context *ctx) \
+{ \
+	return proc_pident_readdir(filp, ctx, \
+				   LSM##_attr_dir_stuff, \
+				   ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct file_operations proc_##LSM##_attr_dir_ops = { \
+	.read		= generic_read_dir, \
+	.iterate	= proc_##LSM##_attr_dir_iterate, \
+	.llseek		= default_llseek, \
+}; \
+\
+static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
+				struct dentry *dentry, unsigned int flags) \
+{ \
+	return proc_pident_lookup(dir, dentry, \
+				  LSM##_attr_dir_stuff, \
+				  ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
+	.lookup		= proc_##LSM##_attr_dir_lookup, \
+	.getattr	= pid_getattr, \
+	.setattr	= proc_setattr, \
+}
+
+#ifdef CONFIG_SECURITY_SMACK
+static const struct pid_entry smack_attr_dir_stuff[] = {
+	ATTR("smack", "current",	0666),
+};
+LSM_DIR_OPS(smack);
+#endif
+
 static const struct pid_entry attr_dir_stuff[] = {
-	REG("current",    S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("prev",       S_IRUGO,	   proc_pid_attr_operations),
-	REG("exec",       S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("fscreate",   S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("keycreate",  S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
+	ATTR(NULL, "current",		0666),
+	ATTR(NULL, "prev",		0444),
+	ATTR(NULL, "exec",		0666),
+	ATTR(NULL, "fscreate",		0666),
+	ATTR(NULL, "keycreate",		0666),
+	ATTR(NULL, "sockcreate",	0666),
+#ifdef CONFIG_SECURITY_SMACK
+	DIR("smack",			0555,
+	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
+#endif
 };
 
 static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 0f1692e63cb6..e3a655a788a7 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -72,6 +72,7 @@ union proc_op {
 	int (*proc_show)(struct seq_file *m,
 		struct pid_namespace *ns, struct pid *pid,
 		struct task_struct *task);
+	const char *lsm;
 };
 
 struct proc_inode {
diff --git a/include/linux/security.h b/include/linux/security.h
index ecb06e1357dd..9afe7a509030 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -368,8 +368,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
 int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
 			unsigned nsops, int alter);
 void security_d_instantiate(struct dentry *dentry, struct inode *inode);
-int security_getprocattr(struct task_struct *p, char *name, char **value);
-int security_setprocattr(const char *name, void *value, size_t size);
+int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
+			 char **value);
+int security_setprocattr(const char *lsm, const char *name, void *value,
+			 size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
@@ -1113,15 +1115,18 @@ static inline int security_sem_semop(struct kern_ipc_perm *sma,
 	return 0;
 }
 
-static inline void security_d_instantiate(struct dentry *dentry, struct inode *inode)
+static inline void security_d_instantiate(struct dentry *dentry,
+					  struct inode *inode)
 { }
 
-static inline int security_getprocattr(struct task_struct *p, char *name, char **value)
+static inline int security_getprocattr(struct task_struct *p, const char *lsm,
+				       char *name, char **value)
 {
 	return -EINVAL;
 }
 
-static inline int security_setprocattr(char *name, void *value, size_t size)
+static inline int security_setprocattr(const char *lsm, char *name,
+				       void *value, size_t size)
 {
 	return -EINVAL;
 }
diff --git a/security/security.c b/security/security.c
index 7bc2fde023a7..3d3c746fd517 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1267,14 +1267,30 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
 }
 EXPORT_SYMBOL(security_d_instantiate);
 
-int security_getprocattr(struct task_struct *p, char *name, char **value)
+int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
+				char **value)
 {
-	return call_int_hook(getprocattr, -EINVAL, p, name, value);
+	struct security_hook_list *hp;
+
+	hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
+		if (lsm != NULL && strcmp(lsm, hp->lsm))
+			continue;
+		return hp->hook.getprocattr(p, name, value);
+	}
+	return -EINVAL;
 }
 
-int security_setprocattr(const char *name, void *value, size_t size)
+int security_setprocattr(const char *lsm, const char *name, void *value,
+			 size_t size)
 {
-	return call_int_hook(setprocattr, -EINVAL, name, value, size);
+	struct security_hook_list *hp;
+
+	hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
+		if (lsm != NULL && strcmp(lsm, hp->lsm))
+			continue;
+		return hp->hook.setprocattr(name, value, size);
+	}
+	return -EINVAL;
 }
 
 int security_netlink_send(struct sock *sk, struct sk_buff *skb)
-- 
2.14.3



  reply	other threads:[~2018-05-11  0:52 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-11  0:30 [PATCH 00/23] LSM: Full security module stacking Casey Schaufler
2018-05-11  0:52 ` Casey Schaufler [this message]
2018-05-11  0:52 ` [PATCH 02/23] Smack: Abstract use of cred security blob Casey Schaufler
2018-05-11  0:52 ` [PATCH 03/23] SELinux: " Casey Schaufler
2018-05-11  0:52 ` [PATCH 04/23] LSM: Infrastructure management of the cred security Casey Schaufler
2018-05-11  0:52 ` [PATCH 05/23] SELinux: Abstract use of file security blob Casey Schaufler
2018-05-11  0:53 ` [PATCH 06/23] LSM: Infrastructure management of the file security Casey Schaufler
2018-05-11  0:53 ` [PATCH 07/23] LSM: Infrastructure management of the task security Casey Schaufler
2018-05-11  0:53 ` [PATCH 08/23] SELinux: Abstract use of inode security blob Casey Schaufler
2018-05-11  0:53 ` [PATCH 09/23] Smack: " Casey Schaufler
2018-05-11  0:53 ` [PATCH 10/23] LSM: Infrastructure management of the inode security Casey Schaufler
2018-05-14 15:04   ` Stephen Smalley
2018-05-14 16:32     ` Casey Schaufler
2018-05-11  0:54 ` [PATCH 11/23] LSM: Infrastructure management of the superblock Casey Schaufler
2018-05-11  0:54 ` [PATCH 12/23] LSM: Infrastructure management of the sock security Casey Schaufler
2018-05-11  0:54 ` [PATCH 13/23] LSM: Infrastructure management of the ipc security blob Casey Schaufler
2018-05-11  0:54 ` [PATCH 14/23] LSM: Infrastructure management of the key " Casey Schaufler
2018-05-11  0:55 ` [PATCH 15/23] LSM: Mark security blob allocation failures as unlikely Casey Schaufler
2018-05-11  0:55 ` [PATCH 16/23] LSM: Sharing of security blobs Casey Schaufler
2018-05-11  0:55 ` [PATCH 17/23] LSM: Allow mount options from multiple security modules Casey Schaufler
2018-05-11  0:55 ` [PATCH 18/23] LSM: Use multiple secids in security module interfaces Casey Schaufler
2018-05-11  0:55 ` [PATCH 19/23] LSM: Use multiple secids in LSM interfaces Casey Schaufler
2018-05-11  0:55 ` [PATCH 20/23] LSM: Move common usercopy into Casey Schaufler
2018-05-14 15:12   ` Stephen Smalley
2018-05-14 16:53     ` Stephen Smalley
2018-05-14 18:55       ` Casey Schaufler
2018-05-11  0:56 ` [PATCH 21/23] LSM: Multiple concurrent major security modules Casey Schaufler
2018-05-11  0:56 ` [PATCH 22/23] LSM: Fix setting of the IMA data in inode init Casey Schaufler
2018-05-11  0:56 ` [PATCH 23/23] Netfilter: Add a selection for Smack Casey Schaufler
2018-05-11  0:58 ` [PATCH 00/23] LSM: Full security module stacking Casey Schaufler
2018-05-11 20:25 ` [PATCH 24/23] LSM: Functions for dealing with struct secids Casey Schaufler

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