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From: Casey Schaufler <casey@schaufler-ca.com>
To: jmorris@namei.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, selinux@vger.kernel.org
Cc: john.johansen@canonical.com, keescook@chromium.org,
	penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com,
	linux-fsdevel@vger.kernel.org, sds@tycho.nsa.gov,
	adobriyan@gmail.com, mic@digikod.net, s.mesoraca16@gmail.com,
	casey@schaufler-ca.com
Subject: [PATCH v5 20/38] procfs: add smack subdir to attrs
Date: Tue, 11 Dec 2018 14:42:56 -0800
Message-ID: <20181211224314.22412-21-casey@schaufler-ca.com> (raw)
In-Reply-To: <20181211224314.22412-1-casey@schaufler-ca.com>

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 proposed S.A.R.A security module is dependent on
the mechanism to create its own attr subdirectory.

The original implementation is by Kees Cook.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 Documentation/admin-guide/LSM/index.rst | 13 +++++--
 fs/proc/base.c                          | 64 ++++++++++++++++++++++++++++-----
 fs/proc/internal.h                      |  1 +
 include/linux/security.h                | 15 +++++---
 security/security.c                     | 24 ++++++++++---
 5 files changed, 96 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 ce3465479447..e133de4897df 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 .
@@ -2517,7 +2521,7 @@ 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);
@@ -2566,7 +2570,9 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
 	if (rv < 0)
 		goto out_free;
 
-	rv = security_setprocattr(file->f_path.dentry->d_name.name, page, count);
+	rv = 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:
 	kfree(page);
@@ -2580,13 +2586,53 @@ 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 5185d7f6a51e..d4f9989063d0 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -81,6 +81,7 @@ 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 d170a5b031f3..35691877c3e1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -390,8 +390,10 @@ 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);
@@ -1139,15 +1141,18 @@ 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 eab64bdc60fb..81ff6a71e78e 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1472,14 +1472,30 @@ 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)
-- 
2.14.5


  parent reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-11 22:42 [PATCH v5 00/38] LSM: Module stacking for SARA and Landlock Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 01/38] LSM: Introduce LSM_FLAG_LEGACY_MAJOR Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 02/38] LSM: Provide separate ordered initialization Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 03/38] LSM: Plumb visibility into optional "enabled" state Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 04/38] LSM: Lift LSM selection out of individual LSMs Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 05/38] LSM: Build ordered list of LSMs to initialize Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 06/38] LSM: Introduce CONFIG_LSM Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 07/38] LSM: Introduce "lsm=" for boottime LSM selection Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 08/38] LSM: Tie enabling logic to presence in ordered list Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 09/38] LSM: Prepare for reorganizing "security=" logic Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 10/38] LSM: Refactor "security=" in terms of enable/disable Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 11/38] LSM: Separate idea of "major" LSM from "exclusive" LSM Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 12/38] apparmor: Remove SECURITY_APPARMOR_BOOTPARAM_VALUE Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 13/38] selinux: Remove SECURITY_SELINUX_BOOTPARAM_VALUE Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 14/38] LSM: Add all exclusive LSMs to ordered initialization Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 15/38] LSM: Split LSM preparation from initialization Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 16/38] LoadPin: Initialize as ordered LSM Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 17/38] Yama: " Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 18/38] LSM: Introduce enum lsm_order Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 19/38] capability: Initialize as LSM_ORDER_FIRST Casey Schaufler
2018-12-11 22:42 ` Casey Schaufler [this message]
2018-12-11 22:42 ` [PATCH v5 21/38] Smack: Abstract use of cred security blob Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 22/38] SELinux: " Casey Schaufler
2018-12-11 22:42 ` [PATCH v5 23/38] SELinux: Remove cred security blob poisoning Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 24/38] SELinux: Remove unused selinux_is_enabled Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 25/38] AppArmor: Abstract use of cred security blob Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 26/38] TOMOYO: " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 27/38] Infrastructure management of the " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 28/38] SELinux: Abstract use of file " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 29/38] Smack: " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 30/38] LSM: Infrastructure management of the file security Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 31/38] SELinux: Abstract use of inode security blob Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 32/38] Smack: " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 33/38] LSM: Infrastructure management of the inode security Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 34/38] LSM: Infrastructure management of the task security Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 35/38] SELinux: Abstract use of ipc security blobs Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 36/38] Smack: " Casey Schaufler
2018-12-11 22:43 ` [PATCH v5 37/38] LSM: Infrastructure management of the ipc security blob Casey Schaufler
2018-12-12 16:05 ` [PATCH v5 38/38] TOMOYO: Update LSM flags to no longer be exclusive Casey Schaufler
  -- strict thread matches above, loose matches on Subject: below --
2018-11-26 23:22 [PATCH v5 00/38] LSM: Module stacking for SARA and Landlock Casey Schaufler
2018-11-26 23:41 ` [PATCH v5 20/38] procfs: add smack subdir to attrs Casey Schaufler

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