LSM: Helpers for attribute names and filling 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.

Both are used in module specific components of LSM system calls.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>

2 files changed, 65 insertions, 0 deletions

diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
index 329aaca5efc0..5d391b1f7e69 100644
--- a/security/lsm_syscalls.c
+++ b/security/lsm_syscalls.c
@@ -18,6 +18,30 @@
 #include <uapi/linux/lsm.h>
 
 /**
+ * lsm_name_to_attr - map an LSM attribute name to its ID
+ * @name: name of the attribute
+ *
+ * Returns the LSM attribute value associated with @name, or 0 if
+ * there is no mapping.
+ */
+u64 lsm_name_to_attr(const char *name)
+{
+	if (!strcmp(name, "current"))
+		return LSM_ATTR_CURRENT;
+	if (!strcmp(name, "exec"))
+		return LSM_ATTR_EXEC;
+	if (!strcmp(name, "fscreate"))
+		return LSM_ATTR_FSCREATE;
+	if (!strcmp(name, "keycreate"))
+		return LSM_ATTR_KEYCREATE;
+	if (!strcmp(name, "prev"))
+		return LSM_ATTR_PREV;
+	if (!strcmp(name, "sockcreate"))
+		return LSM_ATTR_SOCKCREATE;
+	return LSM_ATTR_UNDEF;
+}
+
+/**
  * sys_lsm_set_self_attr - Set current task's security module attribute
  * @attr: which attribute to set
  * @ctx: the LSM contexts
diff --git a/security/security.c b/security/security.c
index 9757d009113f..988483fcf153 100644
--- a/security/security.c
+++ b/security/security.c
@@ -771,6 +771,47 @@ 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, -ENOMEM
+ * if memory can't be allocated.
+ */
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags)
+{
+	struct lsm_ctx *lctx;
+	size_t locallen = struct_size(lctx, ctx, context_size);
+	int rc = 0;
+
+	lctx = kzalloc(locallen, GFP_KERNEL);
+	if (lctx == NULL)
+		return -ENOMEM;
+
+	lctx->id = id;
+	lctx->flags = flags;
+	lctx->ctx_len = context_size;
+	lctx->len = locallen;
+
+	memcpy(lctx->ctx, context, context_size);
+
+	if (copy_to_user(ctx, lctx, locallen))
+		rc = -EFAULT;
+
+	kfree(lctx);
+
+	return rc;
+}
+
 /*
  * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
  * can be accessed with: