From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Date: Thu, 12 Oct 2017 13:42:27 -0700 Subject: [LTP] [PATCH v2 4/4] syscalls/add_key03: new test for forging user keyrings In-Reply-To: <20171012204227.116510-1-ebiggers3@gmail.com> References: <20171012204227.116510-1-ebiggers3@gmail.com> Message-ID: <20171012204227.116510-5-ebiggers3@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it From: Eric Biggers Add a test for a bug which allowed a user to create the user and user session keyrings for another user. Signed-off-by: Eric Biggers --- runtest/syscalls | 1 + testcases/kernel/syscalls/.gitignore | 1 + testcases/kernel/syscalls/add_key/add_key03.c | 98 +++++++++++++++++++++++++++ 3 files changed, 100 insertions(+) create mode 100644 testcases/kernel/syscalls/add_key/add_key03.c diff --git a/runtest/syscalls b/runtest/syscalls index 822608613..e345325a2 100644 --- a/runtest/syscalls +++ b/runtest/syscalls @@ -13,6 +13,7 @@ acct01 acct01 add_key01 add_key01 add_key02 add_key02 +add_key03 add_key03 adjtimex01 adjtimex01 adjtimex02 adjtimex02 diff --git a/testcases/kernel/syscalls/.gitignore b/testcases/kernel/syscalls/.gitignore index 8a2a8d21e..2a770a998 100644 --- a/testcases/kernel/syscalls/.gitignore +++ b/testcases/kernel/syscalls/.gitignore @@ -8,6 +8,7 @@ /acct/acct01 /add_key/add_key01 /add_key/add_key02 +/add_key/add_key03 /adjtimex/adjtimex01 /adjtimex/adjtimex02 /alarm/alarm01 diff --git a/testcases/kernel/syscalls/add_key/add_key03.c b/testcases/kernel/syscalls/add_key/add_key03.c new file mode 100644 index 000000000..27edcb27f --- /dev/null +++ b/testcases/kernel/syscalls/add_key/add_key03.c @@ -0,0 +1,98 @@ +/* + * Copyright (c) 2017 Google, Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program, if not, see . + */ + +/* + * Regression test for commit 237bbd29f7a0 ("KEYS: prevent creating a different + * user's keyrings"). The bug allowed any random user to create a keyring named + * "_uid.$UID" (or "_uid_ses.$UID"), and it would become the user keyring (or + * user session keyring) for user $UID, provided that it hadn't already been + * created. + * + * This test must be run as root so that it has permission to switch to another + * user ID and check whether the keyrings are wrong. However, the underlying + * bug is actually reachable/exploitable by a non-root user. + */ + +#include +#include +#include + +#include "tst_test.h" +#include "lapi/keyctl.h" + +static key_serial_t create_keyring(const char *description) +{ + TEST(add_key("keyring", description, NULL, 0, + KEY_SPEC_PROCESS_KEYRING)); + if (TEST_RETURN < 0) { + tst_brk(TBROK | TTERRNO, + "unable to create keyring '%s'", description); + } + return TEST_RETURN; +} + +static key_serial_t get_keyring_id(key_serial_t special_id) +{ + TEST(keyctl(KEYCTL_GET_KEYRING_ID, special_id, 1)); + if (TEST_RETURN < 0) { + tst_brk(TBROK | TTERRNO, + "unable to get ID of keyring %d", special_id); + } + return TEST_RETURN; +} + +static void do_test(void) +{ + uid_t uid = 1; + char description[32]; + key_serial_t fake_user_keyring; + key_serial_t fake_user_session_keyring; + + /* + * We need a user to forge the keyrings for. But the bug is not + * reproducible for a UID which already has its keyrings, so find an + * unused UID. Note that it would be better to directly check for the + * presence of the UID's keyrings than to search the passwd file. + * However, that's not easy to do given that even if we assumed the UID + * temporarily to check, KEYCTL_GET_KEYRING_ID for the user and user + * session keyrings will create them rather than failing (even if the + * 'create' argument is 0). + */ + while (getpwuid(uid)) + uid++; + + sprintf(description, "_uid.%u", uid); + fake_user_keyring = create_keyring(description); + sprintf(description, "_uid_ses.%u", uid); + fake_user_session_keyring = create_keyring(description); + + SAFE_SETUID(uid); + + if (fake_user_keyring == get_keyring_id(KEY_SPEC_USER_KEYRING)) + tst_brk(TFAIL, "created user keyring for another user"); + + if (fake_user_session_keyring == + get_keyring_id(KEY_SPEC_USER_SESSION_KEYRING)) + tst_brk(TFAIL, "created user session keyring for another user"); + + tst_res(TPASS, "expectedly could not create another user's keyrings"); +} + +static struct tst_test test = { + .test_all = do_test, + .needs_root = 1, +}; -- 2.15.0.rc0.271.g36b669edcc-goog