From patchwork Tue Mar 16 07:06:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 1453707 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=sourceware.org; envelope-from=libc-alpha-bounces@sourceware.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.a=rsa-sha256 header.s=default header.b=XMAXsmpv; dkim-atps=neutral Received: from sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4F048M72ffz9sVm for ; Tue, 16 Mar 2021 18:06:27 +1100 (AEDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id CE913385482D; Tue, 16 Mar 2021 07:06:25 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CE913385482D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1615878385; bh=Q3di8jQ6wm+X0gl6XQz2jEtc640s/88dLvOhlKdreMo=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=XMAXsmpvFcTejfNZA4Cz+PDMI3m875O0U+6A/PRJoqmDV5w/2WrojxZQ94lomOw2/ OKwFTnEayv4ykeHVFylEVagsQON22LFTszosRZJrMozPNl4TOy3Mp6SgEmFH1+0OMQ CsJyuJptwMA13srO9ZHgqyWdYJPkYpsrziTmv/44= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from fossa.birch.relay.mailchannels.net (fossa.birch.relay.mailchannels.net [23.83.209.62]) by sourceware.org (Postfix) with ESMTPS id 755F93854820 for ; Tue, 16 Mar 2021 07:06:21 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 755F93854820 X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 07E82780A9E; Tue, 16 Mar 2021 07:06:20 +0000 (UTC) Received: from pdx1-sub0-mail-a59.g.dreamhost.com (100-96-17-75.trex.outbound.svc.cluster.local [100.96.17.75]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id 8FDD27809C2; Tue, 16 Mar 2021 07:06:19 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org Received: from pdx1-sub0-mail-a59.g.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384) by 100.96.17.75 (trex/6.1.1); Tue, 16 Mar 2021 07:06:20 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|siddhesh@gotplt.org X-MailChannels-Auth-Id: dreamhost X-Wipe-Average: 67d8f81458bf23a5_1615878379880_3816167313 X-MC-Loop-Signature: 1615878379880:3736824954 X-MC-Ingress-Time: 1615878379880 Received: from pdx1-sub0-mail-a59.g.dreamhost.com (localhost [127.0.0.1]) by pdx1-sub0-mail-a59.g.dreamhost.com (Postfix) with ESMTP id 4C6C78A69E; Tue, 16 Mar 2021 00:06:19 -0700 (PDT) Received: from rhbox.redhat.com (unknown [1.186.101.110]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: siddhesh@gotplt.org) by pdx1-sub0-mail-a59.g.dreamhost.com (Postfix) with ESMTPSA id BB4FB801E1; Tue, 16 Mar 2021 00:06:17 -0700 (PDT) X-DH-BACKEND: pdx1-sub0-mail-a59 To: libc-alpha@sourceware.org Subject: [PATCH 1/4] support: Add capability to fork an sgid child Date: Tue, 16 Mar 2021 12:36:05 +0530 Message-Id: <20210316070608.329892-2-siddhesh@sourceware.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210316070608.329892-1-siddhesh@sourceware.org> References: <20210316070608.329892-1-siddhesh@sourceware.org> MIME-Version: 1.0 X-Spam-Status: No, score=-3495.1 required=5.0 tests=BAYES_00, GIT_PATCH_0, JMQ_SPF_NEUTRAL, KAM_DMARC_NONE, KAM_DMARC_STATUS, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NEUTRAL, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Siddhesh Poyarekar via Libc-alpha From: Siddhesh Poyarekar Reply-To: Siddhesh Poyarekar Cc: adhemerval-zanella@linaro.org Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Add a new function support_capture_subprogram_self_sgid that spawns an sgid child of the running program with its own image and returns the exit code of the child process. This functionality is used by at least three tests in the testsuite at the moment, so it makes sense to consolidate. There is also a new function support_subprogram_wait which should provide simple system() like functionality that does not set up file actions. This is useful in cases where only the return code of the spawned subprocess is interesting. This patch also ports tst-secure-getenv to this new function. A subsequent patch will port other tests. This also brings an important change to tst-secure-getenv behaviour. Now instead of succeeding, the test fails as UNSUPPORTED if it is unable to spawn a setgid child, which is how it should have been in the first place. --- stdlib/tst-secure-getenv.c | 199 +++------------------------ support/capture_subprocess.h | 6 + support/check.h | 12 ++ support/subprocess.h | 5 + support/support_capture_subprocess.c | 114 +++++++++++++++ support/support_subprocess.c | 13 ++ 6 files changed, 168 insertions(+), 181 deletions(-) diff --git a/stdlib/tst-secure-getenv.c b/stdlib/tst-secure-getenv.c index c9ec03866f..5567c9ae21 100644 --- a/stdlib/tst-secure-getenv.c +++ b/stdlib/tst-secure-getenv.c @@ -30,167 +30,12 @@ #include #include +#include #include +#include #include static char MAGIC_ARGUMENT[] = "run-actual-test"; -#define MAGIC_STATUS 19 - -/* Return a GID which is not our current GID, but is present in the - supplementary group list. */ -static gid_t -choose_gid (void) -{ - int count = getgroups (0, NULL); - if (count < 0) - { - printf ("getgroups: %m\n"); - exit (1); - } - gid_t *groups; - groups = xcalloc (count, sizeof (*groups)); - int ret = getgroups (count, groups); - if (ret < 0) - { - printf ("getgroups: %m\n"); - exit (1); - } - gid_t current = getgid (); - gid_t not_current = 0; - for (int i = 0; i < ret; ++i) - { - if (groups[i] != current) - { - not_current = groups[i]; - break; - } - } - free (groups); - return not_current; -} - - -/* Copies the executable into a restricted directory, so that we can - safely make it SGID with the TARGET group ID. Then runs the - executable. */ -static int -run_executable_sgid (gid_t target) -{ - char *dirname = xasprintf ("%s/secure-getenv.%jd", - test_dir, (intmax_t) getpid ()); - char *execname = xasprintf ("%s/bin", dirname); - int infd = -1; - int outfd = -1; - int ret = -1; - if (mkdir (dirname, 0700) < 0) - { - printf ("mkdir: %m\n"); - goto err; - } - infd = open ("/proc/self/exe", O_RDONLY); - if (infd < 0) - { - printf ("open (/proc/self/exe): %m\n"); - goto err; - } - outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700); - if (outfd < 0) - { - printf ("open (%s): %m\n", execname); - goto err; - } - char buf[4096]; - for (;;) - { - ssize_t rdcount = read (infd, buf, sizeof (buf)); - if (rdcount < 0) - { - printf ("read: %m\n"); - goto err; - } - if (rdcount == 0) - break; - char *p = buf; - char *end = buf + rdcount; - while (p != end) - { - ssize_t wrcount = write (outfd, buf, end - p); - if (wrcount == 0) - errno = ENOSPC; - if (wrcount <= 0) - { - printf ("write: %m\n"); - goto err; - } - p += wrcount; - } - } - if (fchown (outfd, getuid (), target) < 0) - { - printf ("fchown (%s): %m\n", execname); - goto err; - } - if (fchmod (outfd, 02750) < 0) - { - printf ("fchmod (%s): %m\n", execname); - goto err; - } - if (close (outfd) < 0) - { - printf ("close (outfd): %m\n"); - goto err; - } - if (close (infd) < 0) - { - printf ("close (infd): %m\n"); - goto err; - } - - int kid = fork (); - if (kid < 0) - { - printf ("fork: %m\n"); - goto err; - } - if (kid == 0) - { - /* Child process. */ - char *args[] = { execname, MAGIC_ARGUMENT, NULL }; - execve (execname, args, environ); - printf ("execve (%s): %m\n", execname); - _exit (1); - } - int status; - if (waitpid (kid, &status, 0) < 0) - { - printf ("waitpid: %m\n"); - goto err; - } - if (!WIFEXITED (status) || WEXITSTATUS (status) != MAGIC_STATUS) - { - printf ("Unexpected exit status %d from child process\n", - status); - goto err; - } - ret = 0; - -err: - if (outfd >= 0) - close (outfd); - if (infd >= 0) - close (infd); - if (execname) - { - unlink (execname); - free (execname); - } - if (dirname) - { - rmdir (dirname); - free (dirname); - } - return ret; -} static int do_test (void) @@ -212,15 +57,15 @@ do_test (void) exit (1); } - gid_t target = choose_gid (); - if (target == 0) - { - fprintf (stderr, - "Could not find a suitable GID for user %jd, skipping test\n", - (intmax_t) getuid ()); - exit (0); - } - return run_executable_sgid (target); + int status = support_capture_subprogram_self_sgid (MAGIC_ARGUMENT); + + if (WEXITSTATUS (status) == EXIT_UNSUPPORTED) + return EXIT_UNSUPPORTED; + + if (!WIFEXITED (status)) + FAIL_EXIT1 ("Unexpected exit status %d from child process\n", status); + + return 0; } static void @@ -229,23 +74,15 @@ alternative_main (int argc, char **argv) if (argc == 2 && strcmp (argv[1], MAGIC_ARGUMENT) == 0) { if (getgid () == getegid ()) - { - /* This can happen if the file system is mounted nosuid. */ - fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n", - (intmax_t) getgid ()); - exit (MAGIC_STATUS); - } + /* This can happen if the file system is mounted nosuid. */ + FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n", + (intmax_t) getgid ()); if (getenv ("PATH") == NULL) - { - printf ("PATH variable not present\n"); - exit (3); - } + FAIL_EXIT (3, "PATH variable not present\n"); if (secure_getenv ("PATH") != NULL) - { - printf ("PATH variable not filtered out\n"); - exit (4); - } - exit (MAGIC_STATUS); + FAIL_EXIT (4, "PATH variable not filtered out\n"); + + exit (EXIT_SUCCESS); } } diff --git a/support/capture_subprocess.h b/support/capture_subprocess.h index 8969d4a99a..4be430f099 100644 --- a/support/capture_subprocess.h +++ b/support/capture_subprocess.h @@ -41,6 +41,12 @@ struct support_capture_subprocess support_capture_subprocess struct support_capture_subprocess support_capture_subprogram (const char *file, char *const argv[]); +/* Copy the running program into a setgid binary and run it with CHILD_ID + argument. If execution is successful, return the exit status of the child + program, otherwise return a non-zero failure exit code. */ +int support_capture_subprogram_self_sgid + (char *child_id); + /* Deallocate the subprocess data captured by support_capture_subprocess. */ void support_capture_subprocess_free (struct support_capture_subprocess *); diff --git a/support/check.h b/support/check.h index 83662b2d10..801e34e943 100644 --- a/support/check.h +++ b/support/check.h @@ -54,6 +54,18 @@ __BEGIN_DECLS support_test_verify_impl (__FILE__, __LINE__, #expr); \ }) +/* Record a test failure and jump to LABEL if EXPR evaluates to false. */ +#define TEST_VERIFY_GOTO(expr, label) \ + ({ \ + if ((expr)) \ + ; \ + else \ + { \ + support_test_verify_impl (__FILE__, __LINE__, #expr); \ + goto label; \ + } \ + }) + /* Record a test failure and exit if EXPR evaluates to false. */ #define TEST_VERIFY_EXIT(expr) \ ({ \ diff --git a/support/subprocess.h b/support/subprocess.h index 11cfc6a07f..40d82c7e4d 100644 --- a/support/subprocess.h +++ b/support/subprocess.h @@ -38,6 +38,11 @@ struct support_subprocess support_subprocess struct support_subprocess support_subprogram (const char *file, char *const argv[]); +/* Invoke program FILE with ARGV arguments by using posix_spawn and wait for it + to complete. Return program exit status. */ +int support_subprogram_wait + (const char *file, char *const argv[]); + /* Wait for the subprocess indicated by PROC::PID. Return the status indicate by waitpid call. */ int support_process_wait (struct support_subprocess *proc); diff --git a/support/support_capture_subprocess.c b/support/support_capture_subprocess.c index 3eb825b9af..bb61fecaaf 100644 --- a/support/support_capture_subprocess.c +++ b/support/support_capture_subprocess.c @@ -20,11 +20,14 @@ #include #include +#include #include #include #include #include #include +#include +#include static void transfer (const char *what, struct pollfd *pfd, struct xmemstream *stream) @@ -102,6 +105,117 @@ support_capture_subprogram (const char *file, char *const argv[]) return result; } +/* Copies the executable into a restricted directory, so that we can + safely make it SGID with the TARGET group ID. Then runs the + executable. */ +static int +copy_and_spawn_sgid (char *child_id, gid_t gid) +{ + char *dirname = xasprintf ("%s/tst-tunables-setuid.%jd", + test_dir, (intmax_t) getpid ()); + char *execname = xasprintf ("%s/bin", dirname); + int infd = -1; + int outfd = -1; + int ret = 1, status = 1; + + TEST_VERIFY_GOTO (mkdir (dirname, 0700) >= 0, err); + + infd = open ("/proc/self/exe", O_RDONLY); + if (infd < 0) + FAIL_UNSUPPORTED ("unsupported: Cannot read binary from procfs\n"); + + outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700); + TEST_VERIFY_GOTO (outfd >= 0, err); + + char buf[4096]; + for (;;) + { + ssize_t rdcount = read (infd, buf, sizeof (buf)); + TEST_VERIFY_GOTO (rdcount >= 0, err); + if (rdcount == 0) + break; + char *p = buf; + char *end = buf + rdcount; + while (p != end) + { + ssize_t wrcount = write (outfd, buf, end - p); + if (wrcount == 0) + errno = ENOSPC; + TEST_VERIFY_GOTO (wrcount > 0, err); + p += wrcount; + } + } + int goto_ret = fchown (outfd, getuid (), gid); + TEST_VERIFY_GOTO (goto_ret == 0, err); + goto_ret = fchmod (outfd, 02750); + TEST_VERIFY_GOTO (goto_ret == 0, err); + goto_ret = close (outfd); + TEST_VERIFY_GOTO (goto_ret == 0, err); + goto_ret = close (infd); + TEST_VERIFY_GOTO (goto_ret == 0, err); + + /* We have the binary, now spawn the subprocess. Avoid using + support_subprogram because we only want the program exit status, not the + contents. */ + ret = 0; + + char * const args[] = {execname, child_id, NULL}; + + status = support_subprogram_wait (args[0], args); + +err: + if (outfd >= 0) + close (outfd); + if (infd >= 0) + close (infd); + if (execname != NULL) + { + unlink (execname); + free (execname); + } + if (dirname != NULL) + { + rmdir (dirname); + free (dirname); + } + + if (ret != 0) + FAIL_EXIT1("Failed to make sgid executable for test\n"); + + return status; +} + +int +support_capture_subprogram_self_sgid (char *child_id) +{ + gid_t target = 0; + const int count = 64; + gid_t groups[count]; + + /* Get a GID which is not our current GID, but is present in the + supplementary group list. */ + int ret = getgroups (count, groups); + if (ret < 0) + FAIL_UNSUPPORTED("Could not get group list for user %jd\n", + (intmax_t) getuid ()); + + gid_t current = getgid (); + for (int i = 0; i < ret; ++i) + { + if (groups[i] != current) + { + target = groups[i]; + break; + } + } + + if (target == 0) + FAIL_UNSUPPORTED("Could not find a suitable GID for user %jd\n", + (intmax_t) getuid ()); + + return copy_and_spawn_sgid (child_id, target); +} + void support_capture_subprocess_free (struct support_capture_subprocess *p) { diff --git a/support/support_subprocess.c b/support/support_subprocess.c index 2acfc57b7e..89e767ae47 100644 --- a/support/support_subprocess.c +++ b/support/support_subprocess.c @@ -92,6 +92,19 @@ support_subprogram (const char *file, char *const argv[]) return result; } +int +support_subprogram_wait (const char *file, char *const argv[]) +{ + posix_spawn_file_actions_t fa; + + posix_spawn_file_actions_init (&fa); + struct support_subprocess res = support_subprocess_init (); + + res.pid = xposix_spawn (file, &fa, NULL, argv, environ); + + return support_process_wait (&res); +} + int support_process_wait (struct support_subprocess *proc) {