TOMOYO: Allow specifying domain transition preference.

I got an opinion that it is difficult to use exception policy's domain
transition control directives because they need to match the pathname specified
to "file execute" directives. For example, if "file execute /bin/\*\-ls\-cat"
is given, corresponding domain transition control directive needs to be like
"no_keep_domain /bin/\*\-ls\-cat from any".

If we can specify like below, it will become more convenient.

  file execute /bin/ls keep exec.realpath="/bin/ls" exec.argv[0]="ls"
  file execute /bin/cat keep exec.realpath="/bin/cat" exec.argv[0]="cat"
  file execute /bin/\*\-ls\-cat child
  file execute /usr/sbin/httpd <apache> exec.realpath="/usr/sbin/httpd" exec.argv[0]="/usr/sbin/httpd"

In above examples, "keep" works as if keep_domain is specified, "child" works
as if "no_reset_domain" and "no_initialize_domain" and "no_keep_domain" are
specified, "<apache>" causes domain transition to <apache> domain upon
successful execve() operation.

Moreover, we can also allow transition to different domains based on conditions
like below example.

  <kernel> /usr/sbin/sshd
  file execute /bin/bash <kernel> /usr/sbin/sshd //batch-session exec.argc=2 exec.argv[1]="-c"
  file execute /bin/bash <kernel> /usr/sbin/sshd //root-session task.uid=0
  file execute /bin/bash <kernel> /usr/sbin/sshd //nonroot-session task.uid!=0

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

1 files changed, 47 insertions, 3 deletions

diff --git a/security/tomoyo/condition.c b/security/tomoyo/condition.c
index 3a05eb3e2a64..b854959c0fd4 100644
--- a/security/tomoyo/condition.c
+++ b/security/tomoyo/condition.c
@@ -348,7 +348,7 @@ static inline bool tomoyo_same_condition(const struct tomoyo_condition *a,
                 a->numbers_count == b->numbers_count &&
                 a->names_count == b->names_count &&
                 a->argc == b->argc && a->envc == b->envc &&
-                a->grant_log == b->grant_log &&
+                a->grant_log == b->grant_log && a->transit == b->transit &&
                 !memcmp(a + 1, b + 1, a->size - sizeof(*a));
 }
 
@@ -429,6 +429,46 @@ out:
 }
 
 /**
+ * tomoyo_get_transit_preference - Parse domain transition preference for execve().
+ *
+ * @param: Pointer to "struct tomoyo_acl_param".
+ * @e:     Pointer to "struct tomoyo_condition".
+ *
+ * Returns the condition string part.
+ */
+static char *tomoyo_get_transit_preference(struct tomoyo_acl_param *param,
+                                           struct tomoyo_condition *e)
+{
+        char * const pos = param->data;
+        bool flag;
+        if (*pos == '<') {
+                e->transit = tomoyo_get_domainname(param);
+                goto done;
+        }
+        {
+                char *cp = strchr(pos, ' ');
+                if (cp)
+                        *cp = '\0';
+                flag = tomoyo_correct_path(pos) || !strcmp(pos, "keep") ||
+                        !strcmp(pos, "initialize") || !strcmp(pos, "reset") ||
+                        !strcmp(pos, "child") || !strcmp(pos, "parent");
+                if (cp)
+                        *cp = ' ';
+        }
+        if (!flag)
+                return pos;
+        e->transit = tomoyo_get_name(tomoyo_read_token(param));
+done:
+        if (e->transit)
+                return param->data;
+        /*
+         * Return a bad read-only condition string that will let
+         * tomoyo_get_condition() return NULL.
+         */
+        return "/";
+}
+
+/**
  * tomoyo_get_condition - Parse condition part.
  *
  * @param: Pointer to "struct tomoyo_acl_param".
@@ -444,7 +484,8 @@ struct tomoyo_condition *tomoyo_get_condition(struct tomoyo_acl_param *param)
         struct tomoyo_argv *argv = NULL;
         struct tomoyo_envp *envp = NULL;
         struct tomoyo_condition e = { };
-        char * const start_of_string = param->data;
+        char * const start_of_string =
+                tomoyo_get_transit_preference(param, &e);
         char * const end_of_string = start_of_string + strlen(start_of_string);
         char *pos;
 rerun:
@@ -608,8 +649,9 @@ store_value:
                 + e.envc * sizeof(struct tomoyo_envp);
         entry = kzalloc(e.size, GFP_NOFS);
         if (!entry)
-                return NULL;
+                goto out2;
         *entry = e;
+        e.transit = NULL;
         condp = (struct tomoyo_condition_element *) (entry + 1);
         numbers_p = (struct tomoyo_number_union *) (condp + e.condc);
         names_p = (struct tomoyo_name_union *) (numbers_p + e.numbers_count);
@@ -636,6 +678,8 @@ out:
                 tomoyo_del_condition(&entry->head.list);
                 kfree(entry);
         }
+out2:
+        tomoyo_put_name(e.transit);
         return NULL;
 }