@@ -503,3 +503,226 @@ richacl_set_other_permissions(struct richacl_alloc *alloc, unsigned int *added)
}
return 0;
}
+
+/**
+ * richacl_max_allowed - maximum permissions that anybody is allowed
+ */
+static unsigned int
+richacl_max_allowed(struct richacl *acl)
+{
+ struct richace *ace;
+ unsigned int allowed = 0;
+
+ richacl_for_each_entry_reverse(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_allow(ace))
+ allowed |= ace->e_mask;
+ else if (richace_is_deny(ace)) {
+ if (richace_is_everyone(ace))
+ allowed &= ~ace->e_mask;
+ }
+ }
+ return allowed;
+}
+
+/**
+ * richacl_isolate_owner_class - limit the owner class to the owner file mask
+ * @alloc: acl and number of allocated entries
+ *
+ * POSIX requires that after a chmod, the owner class is granted no more
+ * permissions than the owner file permission bits. For richacls, this
+ * means that the owner class must not be granted any permissions that the
+ * owner mask does not include.
+ *
+ * When we apply file masks to an acl which grant more permissions to the group
+ * or other class than to the owner class, we may end up in a situation where
+ * the owner is granted additional permissions from other aces. For example,
+ * given this acl:
+ *
+ * everyone@:rwx::allow
+ *
+ * when file masks corresponding to mode 0406 are applied, after
+ * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with:
+ *
+ * owner@:r::allow
+ * everyone@:rw::allow
+ *
+ * This acl still grants the owner rw access through the everyone@ allow ace.
+ * To fix this, we must deny the owner w access:
+ *
+ * owner@:w::deny
+ * owner@:r::allow
+ * everyone@:rw::allow
+ */
+static int
+richacl_isolate_owner_class(struct richacl_alloc *alloc)
+{
+ struct richacl *acl = alloc->acl;
+ struct richace *ace;
+ unsigned int deny;
+
+ deny = richacl_max_allowed(acl) & ~acl->a_owner_mask;
+ if (!deny)
+ return 0;
+
+ /*
+ * Figure out if we can update an existig OWNER@ DENY entry.
+ */
+ richacl_for_each_entry(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_allow(ace))
+ break;
+ if (richace_is_owner(ace))
+ return richace_change_mask(alloc, &ace,
+ ace->e_mask | deny);
+ }
+
+ /* Insert an owner@ deny entry at the front. */
+ ace = acl->a_entries;
+ if (richacl_insert_entry(alloc, &ace))
+ return -1;
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = deny;
+ ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
+ return 0;
+}
+
+/**
+ * __richacl_isolate_who - isolate entry from everyone@ allow entry
+ * @alloc: acl and number of allocated entries
+ * @who: identifier to isolate
+ * @deny: permissions this identifier should not be allowed
+ *
+ * See richacl_isolate_group_class().
+ */
+static int
+__richacl_isolate_who(struct richacl_alloc *alloc, struct richace *who,
+ unsigned int deny)
+{
+ struct richacl *acl = alloc->acl;
+ struct richace *ace, who_copy;
+ int n;
+
+ /*
+ * Compute the permissions already defined for @who. There are no
+ * everyone@ deny aces left in the acl at this stage.
+ */
+ richacl_for_each_entry(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_same_identifier(ace, who))
+ deny &= ~ace->e_mask;
+ }
+ if (!deny)
+ return 0;
+
+ /*
+ * Figure out if we can update an existig deny entry. Start from the
+ * entry before the trailing everyone@ allow entry. We will not hit
+ * everyone@ entries in the loop.
+ */
+ for (n = acl->a_count - 2; n != -1; n--) {
+ ace = acl->a_entries + n;
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_deny(ace)) {
+ if (richace_is_same_identifier(ace, who))
+ return richace_change_mask(alloc, &ace,
+ ace->e_mask | deny);
+ } else if (richace_is_allow(ace) &&
+ (ace->e_mask & deny))
+ break;
+ }
+
+ /*
+ * Insert a new entry before the trailing everyone@ deny entry.
+ */
+ richace_copy(&who_copy, who);
+ ace = acl->a_entries + acl->a_count - 1;
+ if (richacl_insert_entry(alloc, &ace))
+ return -1;
+ richace_copy(ace, &who_copy);
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ ace->e_flags &= ~RICHACE_INHERITANCE_FLAGS;
+ ace->e_mask = deny;
+ return 0;
+}
+
+/**
+ * richacl_isolate_group_class - limit the group class to the group file mask
+ * @alloc: acl and number of allocated entries
+ * @deny: additional permissions to deny
+ *
+ * POSIX requires that after a chmod, the group class is granted no more
+ * permissions than the group file permission bits. For richacls, this
+ * means that the group class must not be granted any permissions that the
+ * group mask does not include.
+ *
+ * When we apply file masks to an acl which grant more permissions to the other
+ * class than to the group class, we may end up in a situation where processes
+ * in the group class are granted additional permission from other aces. For
+ * example, given this acl:
+ *
+ * joe:rwx::allow
+ * everyone@:rwx::allow
+ *
+ * when file masks corresponding to mode 0646 are applied, after
+ * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with:
+ *
+ * joe:r::allow
+ * owner@:rw::allow
+ * group@:r::allow
+ * everyone@:rw::allow
+ *
+ * This acl still grants joe and group@ rw access through the everyone@ allow
+ * ace. To fix this, we must deny w access to group class aces before the
+ * everyone@ allow ace at the end of the acl:
+ *
+ * joe:r::allow
+ * owner@:rw::allow
+ * group@:r::allow
+ * joe:w::deny
+ * group@:w::deny
+ * everyone@:rw::allow
+ */
+static int
+richacl_isolate_group_class(struct richacl_alloc *alloc, unsigned int deny)
+{
+ struct richace who = {
+ .e_flags = RICHACE_SPECIAL_WHO,
+ .e_id.special = RICHACE_GROUP_SPECIAL_ID,
+ };
+ struct richace *ace;
+
+ if (!alloc->acl->a_count)
+ return 0;
+ ace = alloc->acl->a_entries + alloc->acl->a_count - 1;
+ if (richace_is_inherit_only(ace) || !richace_is_everyone(ace))
+ return 0;
+ deny |= ace->e_mask & ~alloc->acl->a_group_mask;
+
+ if (deny) {
+ unsigned int n;
+
+ if (__richacl_isolate_who(alloc, &who, deny))
+ return -1;
+ /*
+ * Start from the entry before the trailing everyone@ allow
+ * entry. We will not hit everyone@ entries in the loop.
+ */
+ for (n = alloc->acl->a_count - 2; n != -1; n--) {
+ ace = alloc->acl->a_entries + n;
+
+ if (richace_is_inherit_only(ace) ||
+ richace_is_owner(ace) ||
+ richace_is_group(ace))
+ continue;
+ if (__richacl_isolate_who(alloc, ace, deny))
+ return -1;
+ }
+ }
+ return 0;
+}