From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9AB9C433FE for ; Wed, 5 Oct 2022 18:57:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230476AbiJES5T (ORCPT ); Wed, 5 Oct 2022 14:57:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230241AbiJES5R (ORCPT ); Wed, 5 Oct 2022 14:57:17 -0400 Received: from smtp-1909.mail.infomaniak.ch (smtp-1909.mail.infomaniak.ch [IPv6:2001:1600:3:17::1909]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8BE97DF68 for ; Wed, 5 Oct 2022 11:57:15 -0700 (PDT) Received: from smtp-2-0000.mail.infomaniak.ch (unknown [10.5.36.107]) by smtp-2-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4MjP2K5sDWzMqW4W; Wed, 5 Oct 2022 20:57:13 +0200 (CEST) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-2-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4MjP2K1zJRzMpnPc; Wed, 5 Oct 2022 20:57:13 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1664996233; bh=gfbjZCGaoWDDixy3buW/DN9CPUJWe7eBmnD67qFzLtI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YTCycN96tKqEYiNqEtaVgrRrEOuwmZX+OJNBbOXbkmI92fkPHVeJ4H0CNbRuCw+16 xRU3Mu+HfRBoSwcMBM/Txe/jf82E4ZOvjReJqEBLJ0rlVe9O8Y82/tWJD3gfKpWmSC 3frviJKjj8d1AUuUmKTVmyW31geJOOrOEpfD6bb0= Message-ID: Date: Wed, 5 Oct 2022 20:57:12 +0200 MIME-Version: 1.0 User-Agent: Subject: Re: [PATCH v8 7/9] selftests/landlock: Test FD passing from a Landlock-restricted to an unrestricted process Content-Language: en-US To: =?UTF-8?Q?G=c3=bcnther_Noack?= , linux-security-module@vger.kernel.org Cc: James Morris , Paul Moore , "Serge E . Hallyn" , linux-fsdevel@vger.kernel.org, Konstantin Meskhidze References: <20221001154908.49665-1-gnoack3000@gmail.com> <20221001154908.49665-8-gnoack3000@gmail.com> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= In-Reply-To: <20221001154908.49665-8-gnoack3000@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: Thanks for this refactoring. We need a shorter subject though. ;) On 01/10/2022 17:49, Günther Noack wrote: > A file descriptor created in a restricted process carries Landlock > restrictions with it which will apply even if the same opened file is > used from an unrestricted process. > > This change extracts suitable FD-passing helpers from base_test.c and > moves them to common.h. We use the fixture variants from the ftruncate > fixture to exercise the same scenarios as in the open_and_ftruncate > test, but doing the Landlock restriction and open() in a different > process than the ftruncate() call. > > Signed-off-by: Günther Noack > --- > tools/testing/selftests/landlock/base_test.c | 36 +---------- > tools/testing/selftests/landlock/common.h | 67 ++++++++++++++++++++ > tools/testing/selftests/landlock/fs_test.c | 62 ++++++++++++++++++ > 3 files changed, 132 insertions(+), 33 deletions(-) > > diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c > index 72cdae277b02..6d1b6eedb432 100644 > --- a/tools/testing/selftests/landlock/base_test.c > +++ b/tools/testing/selftests/landlock/base_test.c > @@ -263,23 +263,6 @@ TEST(ruleset_fd_transfer) > .allowed_access = LANDLOCK_ACCESS_FS_READ_DIR, > }; > int ruleset_fd_tx, dir_fd; > - union { > - /* Aligned ancillary data buffer. */ > - char buf[CMSG_SPACE(sizeof(ruleset_fd_tx))]; > - struct cmsghdr _align; > - } cmsg_tx = {}; > - char data_tx = '.'; > - struct iovec io = { > - .iov_base = &data_tx, > - .iov_len = sizeof(data_tx), > - }; > - struct msghdr msg = { > - .msg_iov = &io, > - .msg_iovlen = 1, > - .msg_control = &cmsg_tx.buf, > - .msg_controllen = sizeof(cmsg_tx.buf), > - }; > - struct cmsghdr *cmsg; > int socket_fds[2]; > pid_t child; > int status; > @@ -298,33 +281,20 @@ TEST(ruleset_fd_transfer) > &path_beneath_attr, 0)); > ASSERT_EQ(0, close(path_beneath_attr.parent_fd)); > > - cmsg = CMSG_FIRSTHDR(&msg); > - ASSERT_NE(NULL, cmsg); > - cmsg->cmsg_len = CMSG_LEN(sizeof(ruleset_fd_tx)); > - cmsg->cmsg_level = SOL_SOCKET; > - cmsg->cmsg_type = SCM_RIGHTS; > - memcpy(CMSG_DATA(cmsg), &ruleset_fd_tx, sizeof(ruleset_fd_tx)); > - > /* Sends the ruleset FD over a socketpair and then close it. */ > ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, > socket_fds)); > - ASSERT_EQ(sizeof(data_tx), sendmsg(socket_fds[0], &msg, 0)); > + ASSERT_EQ(0, send_fd(socket_fds[0], ruleset_fd_tx)); > ASSERT_EQ(0, close(socket_fds[0])); > ASSERT_EQ(0, close(ruleset_fd_tx)); > > child = fork(); > ASSERT_LE(0, child); > if (child == 0) { > - int ruleset_fd_rx; > + int ruleset_fd_rx = recv_fd(socket_fds[1]); We can now make it const. > > - *(char *)msg.msg_iov->iov_base = '\0'; > - ASSERT_EQ(sizeof(data_tx), > - recvmsg(socket_fds[1], &msg, MSG_CMSG_CLOEXEC)); > - ASSERT_EQ('.', *(char *)msg.msg_iov->iov_base); > + ASSERT_LE(0, ruleset_fd_rx); > ASSERT_EQ(0, close(socket_fds[1])); > - cmsg = CMSG_FIRSTHDR(&msg); > - ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(ruleset_fd_tx))); > - memcpy(&ruleset_fd_rx, CMSG_DATA(cmsg), sizeof(ruleset_fd_tx)); > > /* Enforces the received ruleset on the child. */ > ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); > diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h > index 7d34592471db..15149d34e43b 100644 > --- a/tools/testing/selftests/landlock/common.h > +++ b/tools/testing/selftests/landlock/common.h > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -189,3 +190,69 @@ static void __maybe_unused clear_cap(struct __test_metadata *const _metadata, > { > _effective_cap(_metadata, caps, CAP_CLEAR); > } > + > +/* Receives an FD from a UNIX socket. Returns the received FD, -1 on error. */ > +static int __maybe_unused recv_fd(int usock) > +{ > + int fd_rx; > + union { > + /* Aligned ancillary data buffer. */ > + char buf[CMSG_SPACE(sizeof(fd_rx))]; > + struct cmsghdr _align; > + } cmsg_rx = {}; > + char data = '\0'; > + struct iovec io = { > + .iov_base = &data, > + .iov_len = sizeof(data), > + }; > + struct msghdr msg = { > + .msg_iov = &io, > + .msg_iovlen = 1, > + .msg_control = &cmsg_rx.buf, > + .msg_controllen = sizeof(cmsg_rx.buf), > + }; > + struct cmsghdr *cmsg; > + int res; > + > + res = recvmsg(usock, &msg, MSG_CMSG_CLOEXEC); > + if (res < 0) > + return -1; It could be useful to return -errno for recv_fd() and send_fd(), and update the description accordingly. That would enable to quickly know the error with the ASSERT_*() calls. > + > + cmsg = CMSG_FIRSTHDR(&msg); > + if (cmsg->cmsg_len != CMSG_LEN(sizeof(fd_rx))) > + return -1; > + > + memcpy(&fd_rx, CMSG_DATA(cmsg), sizeof(fd_rx)); > + return fd_rx; > +} > + > +/* Sends an FD on a UNIX socket. Returns 0 on success or -1 on error. */ > +static int __maybe_unused send_fd(int usock, int fd_tx) > +{ > + union { > + /* Aligned ancillary data buffer. */ > + char buf[CMSG_SPACE(sizeof(fd_tx))]; > + struct cmsghdr _align; > + } cmsg_tx = {}; > + char data_tx = '.'; > + struct iovec io = { > + .iov_base = &data_tx, > + .iov_len = sizeof(data_tx), > + }; > + struct msghdr msg = { > + .msg_iov = &io, > + .msg_iovlen = 1, > + .msg_control = &cmsg_tx.buf, > + .msg_controllen = sizeof(cmsg_tx.buf), > + }; > + struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); > + > + cmsg->cmsg_len = CMSG_LEN(sizeof(fd_tx)); > + cmsg->cmsg_level = SOL_SOCKET; > + cmsg->cmsg_type = SCM_RIGHTS; > + memcpy(CMSG_DATA(cmsg), &fd_tx, sizeof(fd_tx)); > + > + if (sendmsg(usock, &msg, 0) < 0) > + return -1; > + return 0; > +} > diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c > index 308f6f36e8c0..93ed80a25a74 100644 > --- a/tools/testing/selftests/landlock/fs_test.c > +++ b/tools/testing/selftests/landlock/fs_test.c > @@ -3541,6 +3541,68 @@ TEST_F_FORK(ftruncate, open_and_ftruncate) > } > } > > +TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes) > +{ > + int child, fd, status; > + int socket_fds[2]; > + > + ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, > + socket_fds)); > + > + child = fork(); > + ASSERT_LE(0, child); > + if (child == 0) { > + /* > + * Enable Landlock in the child process, open a file descriptor "Enables"… > + * where truncation is forbidden and send it to the > + * non-landlocked parent process. > + */ > + const char *const path = file1_s1d1; > + const struct rule rules[] = { > + { > + .path = path, > + .access = variant->permitted, > + }, > + {}, > + }; > + int fd, ruleset_fd; > + > + /* Enable Landlock. */ This comment is not necessary. > + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); > + ASSERT_LE(0, ruleset_fd); > + enforce_ruleset(_metadata, ruleset_fd); > + ASSERT_EQ(0, close(ruleset_fd)); > + > + fd = open(path, O_WRONLY); > + ASSERT_EQ(variant->expected_open_result, (fd < 0 ? errno : 0)); > + > + if (fd >= 0) { > + ASSERT_EQ(0, send_fd(socket_fds[0], fd)); > + ASSERT_EQ(0, close(fd)); > + } > + > + ASSERT_EQ(0, close(socket_fds[0])); > + > + _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE); You might want to add a "return" here to help the compiler (and the reader). > + } > + > + if (variant->expected_open_result == 0) { > + fd = recv_fd(socket_fds[1]); > + ASSERT_LE(0, fd); > + > + EXPECT_EQ(variant->expected_ftruncate_result, > + test_ftruncate(fd)); > + ASSERT_EQ(0, close(fd)); > + } > + > + ASSERT_EQ(child, waitpid(child, &status, 0)); > + ASSERT_EQ(1, WIFEXITED(status)); > + ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status)); > + > + ASSERT_EQ(0, close(socket_fds[0])); > + ASSERT_EQ(0, close(socket_fds[1])); > +} > + > /* clang-format off */ > FIXTURE(layout1_bind) {}; > /* clang-format on */