TOMOYO: Add environment variable name restriction support.

This patch adds support for checking environment variable's names.
Although TOMOYO already provides ability to check argv[]/envp[] passed to
execve() requests,

  file execute /bin/sh exec.envp["LD_LIBRARY_PATH"]="bar"

will reject execution of /bin/sh if environment variable LD_LIBRARY_PATH is not
defined. To grant execution of /bin/sh if LD_LIBRARY_PATH is not defined,
administrators have to specify like

  file execute /bin/sh exec.envp["LD_LIBRARY_PATH"]="/system/lib"
  file execute /bin/sh exec.envp["LD_LIBRARY_PATH"]=NULL

. Since there are many environment variables whereas conditional checks are
applied as "&&", it is difficult to cover all combinations. Therefore, this
patch supports conditional checks that are applied as "||", by specifying like

  file execute /bin/sh
  misc env LD_LIBRARY_PATH exec.envp["LD_LIBRARY_PATH"]="/system/lib"

which means "grant execution of /bin/sh if environment variable is not defined
or is defined and its value is /system/lib".

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 122 insertions, 0 deletions

diff --git a/security/tomoyo/environ.c b/security/tomoyo/environ.c
new file mode 100644
index 000000000000..ad4c6e18a437
--- /dev/null
+++ b/security/tomoyo/environ.c
@@ -0,0 +1,122 @@
+/*
+ * security/tomoyo/environ.c
+ *
+ * Copyright (C) 2005-2011  NTT DATA CORPORATION
+ */
+
+#include "common.h"
+
+/**
+ * tomoyo_check_env_acl - Check permission for environment variable's name.
+ *
+ * @r:   Pointer to "struct tomoyo_request_info".
+ * @ptr: Pointer to "struct tomoyo_acl_info".
+ *
+ * Returns true if granted, false otherwise.
+ */
+static bool tomoyo_check_env_acl(struct tomoyo_request_info *r,
+				 const struct tomoyo_acl_info *ptr)
+{
+	const struct tomoyo_env_acl *acl =
+		container_of(ptr, typeof(*acl), head);
+
+	return tomoyo_path_matches_pattern(r->param.environ.name, acl->env);
+}
+
+/**
+ * tomoyo_audit_env_log - Audit environment variable name log.
+ *
+ * @r: Pointer to "struct tomoyo_request_info".
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+static int tomoyo_audit_env_log(struct tomoyo_request_info *r)
+{
+	return tomoyo_supervisor(r, "misc env %s\n",
+				 r->param.environ.name->name);
+}
+
+/**
+ * tomoyo_env_perm - Check permission for environment variable's name.
+ *
+ * @r:   Pointer to "struct tomoyo_request_info".
+ * @env: The name of environment variable.
+ *
+ * Returns 0 on success, negative value otherwise.
+ *
+ * Caller holds tomoyo_read_lock().
+ */
+int tomoyo_env_perm(struct tomoyo_request_info *r, const char *env)
+{
+	struct tomoyo_path_info environ;
+	int error;
+
+	if (!env || !*env)
+		return 0;
+	environ.name = env;
+	tomoyo_fill_path_info(&environ);
+	r->param_type = TOMOYO_TYPE_ENV_ACL;
+	r->param.environ.name = &environ;
+	do {
+		tomoyo_check_acl(r, tomoyo_check_env_acl);
+		error = tomoyo_audit_env_log(r);
+	} while (error == TOMOYO_RETRY_REQUEST);
+	return error;
+}
+
+/**
+ * tomoyo_same_env_acl - Check for duplicated "struct tomoyo_env_acl" entry.
+ *
+ * @a: Pointer to "struct tomoyo_acl_info".
+ * @b: Pointer to "struct tomoyo_acl_info".
+ *
+ * Returns true if @a == @b, false otherwise.
+ */
+static bool tomoyo_same_env_acl(const struct tomoyo_acl_info *a,
+				const struct tomoyo_acl_info *b)
+{
+	const struct tomoyo_env_acl *p1 = container_of(a, typeof(*p1), head);
+	const struct tomoyo_env_acl *p2 = container_of(b, typeof(*p2), head);
+
+	return p1->env == p2->env;
+}
+
+/**
+ * tomoyo_write_env - Write "struct tomoyo_env_acl" list.
+ *
+ * @param: Pointer to "struct tomoyo_acl_param".
+ *
+ * Returns 0 on success, negative value otherwise.
+ *
+ * Caller holds tomoyo_read_lock().
+ */
+static int tomoyo_write_env(struct tomoyo_acl_param *param)
+{
+	struct tomoyo_env_acl e = { .head.type = TOMOYO_TYPE_ENV_ACL };
+	int error = -ENOMEM;
+	const char *data = tomoyo_read_token(param);
+
+	if (!tomoyo_correct_word(data) || strchr(data, '='))
+		return -EINVAL;
+	e.env = tomoyo_get_name(data);
+	if (!e.env)
+		return error;
+	error = tomoyo_update_domain(&e.head, sizeof(e), param,
+				  tomoyo_same_env_acl, NULL);
+	tomoyo_put_name(e.env);
+	return error;
+}
+
+/**
+ * tomoyo_write_misc - Update environment variable list.
+ *
+ * @param: Pointer to "struct tomoyo_acl_param".
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+int tomoyo_write_misc(struct tomoyo_acl_param *param)
+{
+	if (tomoyo_str_starts(&param->data, "env "))
+		return tomoyo_write_env(param);
+	return -EINVAL;
+}