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Message-Id: <20230315224704.2672-8-casey@schaufler-ca.com>
Date: Wed, 15 Mar 2023 15:47:00 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: casey@...aufler-ca.com, paul@...l-moore.com,
linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org, keescook@...omium.org,
john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
linux-api@...r.kernel.org, mic@...ikod.net
Subject: [PATCH v7 07/11] LSM: Helpers for attribute names and filling an lsm_ctx
Add lsm_name_to_attr(), which translates a text string to a
LSM_ATTR value if one is available.
Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
the trailing attribute value.
All are used in module specific components of LSM system calls.
Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
include/linux/security.h | 13 ++++++++++
security/lsm_syscalls.c | 51 ++++++++++++++++++++++++++++++++++++++++
security/security.c | 31 ++++++++++++++++++++++++
3 files changed, 95 insertions(+)
diff --git a/include/linux/security.h b/include/linux/security.h
index 329cd9d2be50..a5e860d332b5 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -263,6 +263,7 @@ int unregister_blocking_lsm_notifier(struct notifier_block *nb);
/* prototypes */
extern int security_init(void);
extern int early_security_init(void);
+extern u64 lsm_name_to_attr(const char *name);
/* Security operations */
int security_binder_set_context_mgr(const struct cred *mgr);
@@ -491,6 +492,8 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
int security_locked_down(enum lockdown_reason what);
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+ size_t context_size, u64 id, u64 flags);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -508,6 +511,11 @@ static inline int unregister_blocking_lsm_notifier(struct notifier_block *nb)
return 0;
}
+static inline u64 lsm_name_to_attr(const char *name)
+{
+ return 0;
+}
+
static inline void security_free_mnt_opts(void **mnt_opts)
{
}
@@ -1420,6 +1428,11 @@ static inline int security_locked_down(enum lockdown_reason what)
{
return 0;
}
+static inline int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+ size_t context_size, u64 id, u64 flags)
+{
+ return 0;
+}
#endif /* CONFIG_SECURITY */
#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
index 6efbe244d304..55d849ad5d6e 100644
--- a/security/lsm_syscalls.c
+++ b/security/lsm_syscalls.c
@@ -17,6 +17,57 @@
#include <linux/lsm_hooks.h>
#include <uapi/linux/lsm.h>
+struct attr_map {
+ char *name;
+ u64 attr;
+};
+
+static const struct attr_map lsm_attr_names[] = {
+ {
+ .name = "current",
+ .attr = LSM_ATTR_CURRENT,
+ },
+ {
+ .name = "exec",
+ .attr = LSM_ATTR_EXEC,
+ },
+ {
+ .name = "fscreate",
+ .attr = LSM_ATTR_FSCREATE,
+ },
+ {
+ .name = "keycreate",
+ .attr = LSM_ATTR_KEYCREATE,
+ },
+ {
+ .name = "prev",
+ .attr = LSM_ATTR_PREV,
+ },
+ {
+ .name = "sockcreate",
+ .attr = LSM_ATTR_SOCKCREATE,
+ },
+};
+
+/**
+ * lsm_name_to_attr - map an LSM attribute name to its ID
+ * @name: name of the attribute
+ *
+ * Look the given @name up in the table of know attribute names.
+ *
+ * Returns the LSM attribute value associated with @name, or 0 if
+ * there is no mapping.
+ */
+u64 lsm_name_to_attr(const char *name)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
+ if (!strcmp(name, lsm_attr_names[i].name))
+ return lsm_attr_names[i].attr;
+ return 0;
+}
+
/**
* sys_lsm_set_self_attr - Set current task's security module attribute
* @attr: which attribute to set
diff --git a/security/security.c b/security/security.c
index 2c57fe28c4f7..f7b814a3940c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
return 0;
}
+/**
+ * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
+ * @ctx: an LSM context to be filled
+ * @context: the new context value
+ * @context_size: the size of the new context value
+ * @id: LSM id
+ * @flags: LSM defined flags
+ *
+ * Fill all of the fields in a user space lsm_ctx structure.
+ * Caller is assumed to have verified that @ctx has enough space
+ * for @context.
+ * Returns 0 on success, -EFAULT on a copyout error.
+ */
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+ size_t context_size, u64 id, u64 flags)
+{
+ struct lsm_ctx local;
+ void __user *vc = ctx;
+
+ local.id = id;
+ local.flags = flags;
+ local.ctx_len = context_size;
+ local.len = context_size + sizeof(local);
+ vc += sizeof(local);
+ if (copy_to_user(ctx, &local, sizeof(local)))
+ return -EFAULT;
+ if (context_size > 0 && copy_to_user(vc, context, context_size))
+ return -EFAULT;
+ return 0;
+}
+
/*
* The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
* can be accessed with:
--
2.39.2
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