From patchwork Wed Jan 19 08:21:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 50224 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 4124B385781A for ; Wed, 19 Jan 2022 08:24:33 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4124B385781A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1642580673; bh=Gp3vUCRflElvH7l1NeeDXeH7sUlyMZmzbt1t0VWUPy8=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=HotuNmoTWU9e0p6qJvftIA3v608MXQmQGCNdM9VbBH2MXds89L1zUKw0Q7CoU/nnl Cefz3XrbpA+pBuIiNUhcA371TyDffeDOpMHwY39k2tMLQxk2WCBYL3HA6+e2kbBA9G 3uAy99mIMY947fy9Snk93V9hKwJbNkVJDOILk2Vk= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from camel.birch.relay.mailchannels.net (camel.birch.relay.mailchannels.net [23.83.209.29]) by sourceware.org (Postfix) with ESMTPS id 608193857C6A for ; Wed, 19 Jan 2022 08:22:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 608193857C6A 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 8C6B46C10BA; Wed, 19 Jan 2022 08:22:05 +0000 (UTC) Received: from pdx1-sub0-mail-a305.dreamhost.com (unknown [127.0.0.6]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id C9A716C2180; Wed, 19 Jan 2022 08:22:04 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org Received: from pdx1-sub0-mail-a305.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384) by 100.126.0.19 (trex/6.4.3); Wed, 19 Jan 2022 08:22:05 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|siddhesh@gotplt.org X-MailChannels-Auth-Id: dreamhost X-Vacuous-Whispering: 406ea61850f5bc83_1642580525416_3727799508 X-MC-Loop-Signature: 1642580525416:2690116414 X-MC-Ingress-Time: 1642580525416 Received: from rhbox.redhat.com (unknown [1.186.224.209]) (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) (Authenticated sender: siddhesh@gotplt.org) by pdx1-sub0-mail-a305.dreamhost.com (Postfix) with ESMTPSA id 4JdzBy6QVnz24; Wed, 19 Jan 2022 00:22:02 -0800 (PST) To: libc-alpha@sourceware.org Subject: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Date: Wed, 19 Jan 2022 13:51:45 +0530 Message-Id: <20220119082147.3352868-2-siddhesh@sourceware.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220119082147.3352868-1-siddhesh@sourceware.org> References: <20220119082147.3352868-1-siddhesh@sourceware.org> MIME-Version: 1.0 X-Spam-Status: No, score=-3493.5 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=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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 Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" Add new helpers support_create_and_chdir_toolong_temp_directory and support_chdir_toolong_temp_directory to create and descend into directory trees longer than PATH_MAX. Signed-off-by: Siddhesh Poyarekar --- support/temp_file.c | 173 +++++++++++++++++++++++++++++++++++++++++--- support/temp_file.h | 9 +++ 2 files changed, 173 insertions(+), 9 deletions(-) diff --git a/support/temp_file.c b/support/temp_file.c index e7bb8aadb9..59060e573f 100644 --- a/support/temp_file.c +++ b/support/temp_file.c @@ -1,5 +1,6 @@ /* Temporary file handling for tests. Copyright (C) 1998-2022 Free Software Foundation, Inc. + Copyright The GNU Tools Authors. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -20,15 +21,17 @@ some 32-bit platforms. */ #define _FILE_OFFSET_BITS 64 +#include #include #include #include +#include #include #include #include #include -#include +#include /* List of temporary files. */ static struct temp_name_list @@ -36,14 +39,32 @@ static struct temp_name_list struct temp_name_list *next; char *name; pid_t owner; + bool toolong; } *temp_name_list; /* Location of the temporary files. Set by the test skeleton via support_set_test_dir. The string is not be freed. */ static const char *test_dir = _PATH_TMP; -void -add_temp_file (const char *name) +/* Name of subdirectories in a too long temporary directory tree. */ +static char *toolong_subdir; +static bool toolong_subdir_initialized; + +/* Return the maximum size of path on the target. */ +static inline size_t +get_path_max (void) +{ +#ifdef PATH_MAX + return PATH_MAX; +#else + size_t path_max = pathconf ("/", _PC_PATH_MAX); + return (path_max < 0 ? 1024 + : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX); +#endif +} + +static void +add_temp_file_internal (const char *name, bool toolong) { struct temp_name_list *newp = (struct temp_name_list *) xcalloc (sizeof (*newp), 1); @@ -53,12 +74,19 @@ add_temp_file (const char *name) newp->name = newname; newp->next = temp_name_list; newp->owner = getpid (); + newp->toolong = toolong; temp_name_list = newp; } else free (newp); } +void +add_temp_file (const char *name) +{ + add_temp_file_internal (name, false); +} + int create_temp_file_in_dir (const char *base, const char *dir, char **filename) { @@ -90,8 +118,8 @@ create_temp_file (const char *base, char **filename) return create_temp_file_in_dir (base, test_dir, filename); } -char * -support_create_temp_directory (const char *base) +static char * +create_temp_directory_internal (const char *base, bool toolong) { char *path = xasprintf ("%s/%sXXXXXX", test_dir, base); if (mkdtemp (path) == NULL) @@ -99,16 +127,132 @@ support_create_temp_directory (const char *base) printf ("error: mkdtemp (\"%s\"): %m", path); exit (1); } - add_temp_file (path); + add_temp_file_internal (path, toolong); return path; } -/* Helper functions called by the test skeleton follow. */ +char * +support_create_temp_directory (const char *base) +{ + return create_temp_directory_internal (base, false); +} + +static void +ensure_toolong_subdir_initialized (void) +{ + if (!toolong_subdir_initialized) + FAIL_EXIT1 ("uninitialized toolong directory tree\n"); +} + +static void +initialize_toolong_subdir (void) +{ + size_t sz = NAME_MAX; + char testname[NAME_MAX]; + int ret; + + if (toolong_subdir_initialized) + return; + + memset (testname, 'X', sz - 1); + + /* Explore the name limit on the file system. This should typically be + NAME_MAX, but it could be less on some fuse filesystems. */ + do + { + struct stat statbuf; + + testname[sz - 1] = '\0'; + ret = stat (testname, &statbuf); + } + while (ret != 0 && errno == ENAMETOOLONG && (sz = sz / 2) > 0); + + if (ret != 0 && errno == ENAMETOOLONG) + FAIL_EXIT1 ("stat (%s) failed with ENAMETOOLONG\n", testname); + + toolong_subdir = xmalloc (sz); + strcpy (toolong_subdir, testname); + toolong_subdir_initialized = true; +} + +char * +support_create_and_chdir_toolong_temp_directory (const char *basename) +{ + size_t path_max = get_path_max (); + + char *base = create_temp_directory_internal (basename, true); + + xchdir (base); + + initialize_toolong_subdir (); + + size_t sz = strlen (toolong_subdir); + + /* Create directories and descend into them so that the final path is larger + than PATH_MAX. */ + for (size_t i = 0; i <= path_max / sz; i++) + { + xmkdir (toolong_subdir, S_IRWXU); + xchdir (toolong_subdir); + } + return base; +} void -support_set_test_dir (const char *path) +support_chdir_toolong_temp_directory (const char *base) { - test_dir = path; + size_t path_max = get_path_max (); + ensure_toolong_subdir_initialized (); + + xchdir (base); + + size_t sz = strlen (toolong_subdir); + for (size_t i = 0; i <= path_max / sz; i++) + xchdir (toolong_subdir); +} + +/* Helper functions called by the test skeleton follow. */ + +static void +remove_toolong_subdirs (const char *base) +{ + size_t path_max = get_path_max (); + + ensure_toolong_subdir_initialized (); + + if (chdir (base) != 0) + { + printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n", + base); + return; + } + + /* Descend. */ + int levels = 0; + size_t sz = strlen (toolong_subdir); + for (levels = 0; levels <= path_max / sz; levels++) + if (chdir (toolong_subdir) != 0) + { + printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n", + toolong_subdir); + return; + } + + /* Ascend and remove. */ + while (--levels >= 0) + { + if (chdir ("..") != 0) + { + printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n"); + return; + } + if (remove (toolong_subdir) != 0) + { + printf ("warning: could not remove subdirectory: %s: %m\n", + toolong_subdir); + return; + } + } } void @@ -123,6 +267,9 @@ support_delete_temp_files (void) around, to prevent PID reuse.) */ if (temp_name_list->owner == pid) { + if (temp_name_list->toolong) + remove_toolong_subdirs (temp_name_list->name); + if (remove (temp_name_list->name) != 0) printf ("warning: could not remove temporary file: %s: %m\n", temp_name_list->name); @@ -133,6 +280,8 @@ support_delete_temp_files (void) free (temp_name_list); temp_name_list = next; } + + free (toolong_subdir); } void @@ -147,3 +296,9 @@ support_print_temp_files (FILE *f) fprintf (f, ")\n"); } } + +void +support_set_test_dir (const char *path) +{ + test_dir = path; +} diff --git a/support/temp_file.h b/support/temp_file.h index 50a443abe4..8459ddda72 100644 --- a/support/temp_file.h +++ b/support/temp_file.h @@ -44,6 +44,15 @@ int create_temp_file_in_dir (const char *base, const char *dir, returns. The caller should free this string. */ char *support_create_temp_directory (const char *base); +/* Create a temporary directory tree that is longer than PATH_MAX and schedule + it for deletion. BASENAME is used as a prefix for the unique directory + name, which the function returns. The caller should free this string. */ +char *support_create_and_chdir_toolong_temp_directory (const char *basename); + +/* Change into the innermost directory of the directory tree BASE, which was + created using support_create_and_chdir_toolong_temp_directory. */ +void support_chdir_toolong_temp_directory (const char *base); + __END_DECLS #endif /* SUPPORT_TEMP_FILE_H */ From patchwork Wed Jan 19 08:21:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 50223 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id D041E3857831 for ; Wed, 19 Jan 2022 08:23:50 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D041E3857831 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1642580630; bh=S4Nii/H8kZDwSxNWa2nAuiZIkHrezu+KJy02bqocvTs=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=E3p1+JlpgD+bS+o34I480R8j3BOCw/kJDS0mH9a6BHIgxst8S2BsVHJ7R9QEot3IU DgiJsjEA4l43ycRRsCDTPSsAevClY6lnkdXKw1s8NVN3WYjCfDrGDBuKGMqjPkCgCN Bci6ld943AwH8FTbHyNqoDUBpa9Qt8LnkXp9J1jE= 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 724B53857810 for ; Wed, 19 Jan 2022 08:22:09 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 724B53857810 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 35C83821E18; Wed, 19 Jan 2022 08:22:08 +0000 (UTC) Received: from pdx1-sub0-mail-a305.dreamhost.com (unknown [127.0.0.6]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id BC165821A2A; Wed, 19 Jan 2022 08:22:07 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org Received: from pdx1-sub0-mail-a305.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384) by 100.124.31.69 (trex/6.4.3); Wed, 19 Jan 2022 08:22:08 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|siddhesh@gotplt.org X-MailChannels-Auth-Id: dreamhost X-Abortive-Quick: 755569c516fc8511_1642580528042_2749727900 X-MC-Loop-Signature: 1642580528042:162089014 X-MC-Ingress-Time: 1642580528042 Received: from rhbox.redhat.com (unknown [1.186.224.209]) (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) (Authenticated sender: siddhesh@gotplt.org) by pdx1-sub0-mail-a305.dreamhost.com (Postfix) with ESMTPSA id 4JdzC12TWjz1P2; Wed, 19 Jan 2022 00:22:04 -0800 (PST) To: libc-alpha@sourceware.org Subject: [PATCH v2 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX (CVE-2021-3998) Date: Wed, 19 Jan 2022 13:51:46 +0530 Message-Id: <20220119082147.3352868-3-siddhesh@sourceware.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220119082147.3352868-1-siddhesh@sourceware.org> References: <20220119082147.3352868-1-siddhesh@sourceware.org> MIME-Version: 1.0 X-Spam-Status: No, score=-3493.5 required=5.0 tests=BAYES_00, GIT_PATCH_0, JMQ_SPF_NEUTRAL, KAM_DMARC_NONE, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NEUTRAL, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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 Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" realpath returns an allocated string when the result exceeds PATH_MAX, which is unexpected when its second argument is not NULL. This results in the second argument (resolved) being uninitialized and also results in a memory leak since the caller expects resolved to be the same as the returned value. Return NULL and set errno to ENAMETOOLONG if the result exceeds PATH_MAX. This fixes BZ #28770, which is CVE-2021-3998. Reviewed-by: Adhemerval Zanella Signed-off-by: Siddhesh Poyarekar --- NEWS | 4 +++ stdlib/Makefile | 1 + stdlib/canonicalize.c | 12 +++++++-- stdlib/tst-realpath-toolong.c | 49 +++++++++++++++++++++++++++++++++++ 4 files changed, 64 insertions(+), 2 deletions(-) create mode 100644 stdlib/tst-realpath-toolong.c diff --git a/NEWS b/NEWS index 6ed9fa9787..4c392a445e 100644 --- a/NEWS +++ b/NEWS @@ -166,6 +166,10 @@ Security related changes: CVE-2022-23218: Passing an overlong file name to the svcunix_create legacy function could result in a stack-based buffer overflow. + CVE-2021-3998: Passing a path longer than PATH_MAX to the realpath + function could result in a memory leak and potential access of + uninitialized memory. Reported by Qualys. + The following bugs are resolved with this release: [The release manager will add the list generated by diff --git a/stdlib/Makefile b/stdlib/Makefile index 1e81f98fac..8236741984 100644 --- a/stdlib/Makefile +++ b/stdlib/Makefile @@ -109,6 +109,7 @@ tests := \ tst-random \ tst-random2 \ tst-realpath \ + tst-realpath-toolong \ tst-secure-getenv \ tst-setcontext \ tst-setcontext2 \ diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c index f36bdf4c76..732dc7ea46 100644 --- a/stdlib/canonicalize.c +++ b/stdlib/canonicalize.c @@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved, error: *dest++ = '\0'; - if (resolved != NULL && dest - rname <= get_path_max ()) - rname = strcpy (resolved, rname); + if (resolved != NULL) + { + if (dest - rname <= get_path_max ()) + rname = strcpy (resolved, rname); + else + { + failed = true; + __set_errno (ENAMETOOLONG); + } + } error_nomem: scratch_buffer_free (&extra_buffer); diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c new file mode 100644 index 0000000000..8bed772460 --- /dev/null +++ b/stdlib/tst-realpath-toolong.c @@ -0,0 +1,49 @@ +/* Verify that realpath returns NULL with ENAMETOOLONG if the result exceeds + NAME_MAX. + Copyright The GNU Toolchain Authors. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define BASENAME "tst-realpath-toolong." + +int +do_test (void) +{ + char *base = support_create_and_chdir_toolong_temp_directory (BASENAME); + + char buf[PATH_MAX + 1]; + const char *res = realpath (".", buf); + + /* canonicalize.c states that if the real path is >= PATH_MAX, then + realpath returns NULL and sets ENAMETOOLONG. */ + TEST_VERIFY (res == NULL); + TEST_VERIFY (errno == ENAMETOOLONG); + + free (base); + return 0; +} + +#include From patchwork Wed Jan 19 08:21:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 50225 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 4CFF13857818 for ; Wed, 19 Jan 2022 08:25:20 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4CFF13857818 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1642580720; bh=UTHhklEEJPpz9WQCaQHVa9sGzPyn/ECEQn9ls8i+3C0=; 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=STR1iHMiSq+rB5qHiKO50KWYonO+y6QLsLZJVmQPHPI6AGYu26HtoDxlvXhpnkyd4 bBTdF+F8ZRUCtEIP4DTTfWl3cfaqxMAV5vh1S/4KGfKY4vqWqNk2VQRuvZCsnxj5Qq nR8FQYXuuOr7mGEJT7EdHuQguC95YLjs/Z0Af9Hc= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from firebrick.maple.relay.mailchannels.net (firebrick.maple.relay.mailchannels.net [23.83.214.59]) by sourceware.org (Postfix) with ESMTPS id 835FA3857C7F for ; Wed, 19 Jan 2022 08:22:15 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 835FA3857C7F 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 3BE0D461506; Wed, 19 Jan 2022 08:22:11 +0000 (UTC) Received: from pdx1-sub0-mail-a305.dreamhost.com (unknown [127.0.0.6]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id DB7F646140B; Wed, 19 Jan 2022 08:22:10 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|siddhesh@gotplt.org Received: from pdx1-sub0-mail-a305.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384) by 100.121.92.82 (trex/6.4.3); Wed, 19 Jan 2022 08:22:11 +0000 X-MC-Relay: Bad X-MailChannels-SenderId: dreamhost|x-authsender|siddhesh@gotplt.org X-MailChannels-Auth-Id: dreamhost X-Wipe-Eyes: 249d47ca7edc076d_1642580531054_3902181326 X-MC-Loop-Signature: 1642580531054:2166836535 X-MC-Ingress-Time: 1642580531053 Received: from rhbox.redhat.com (unknown [1.186.224.209]) (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) (Authenticated sender: siddhesh@gotplt.org) by pdx1-sub0-mail-a305.dreamhost.com (Postfix) with ESMTPSA id 4JdzC42Cmbz3h; Wed, 19 Jan 2022 00:22:07 -0800 (PST) To: libc-alpha@sourceware.org Subject: [PATCH v2 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Date: Wed, 19 Jan 2022 13:51:47 +0530 Message-Id: <20220119082147.3352868-4-siddhesh@sourceware.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220119082147.3352868-1-siddhesh@sourceware.org> References: <20220119082147.3352868-1-siddhesh@sourceware.org> MIME-Version: 1.0 X-Spam-Status: No, score=-3493.5 required=5.0 tests=BAYES_00, GIT_PATCH_0, JMQ_SPF_NEUTRAL, KAM_DMARC_NONE, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NEUTRAL, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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: Qualys Security Advisory Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" No valid path returned by getcwd would fit into 1 byte, so reject the size early and return NULL with errno set to ERANGE. This change is prompted by CVE-2021-3999, which describes a single byte buffer underflow and overflow when all of the following conditions are met: - The buffer size (i.e. the second argument of getcwd) is 1 byte - The current working directory is too long - '/' is also mounted on the current working directory Sequence of events: - In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG because the linux kernel checks for name length before it checks buffer size - The code falls back to the generic getcwd in sysdeps/posix - In the generic func, the buf[0] is set to '\0' on line 250 - this while loop on line 262 is bypassed: while (!(thisdev == rootdev && thisino == rootino)) since the rootfs (/) is bind mounted onto the directory and the flow goes on to line 449, where it puts a '/' in the byte before the buffer. - Finally on line 458, it moves 2 bytes (the underflowed byte and the '\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow. - buf is returned on line 469 and errno is not set. This resolves BZ #28769. Signed-off-by: Qualys Security Advisory Signed-off-by: Siddhesh Poyarekar --- NEWS | 6 + sysdeps/posix/getcwd.c | 7 + sysdeps/unix/sysv/linux/Makefile | 7 +- .../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++ 4 files changed, 264 insertions(+), 1 deletion(-) create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c diff --git a/NEWS b/NEWS index 4c392a445e..07e9eac52d 100644 --- a/NEWS +++ b/NEWS @@ -170,6 +170,12 @@ Security related changes: function could result in a memory leak and potential access of uninitialized memory. Reported by Qualys. + CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd + function may result in an off-by-one buffer underflow and overflow + when the current working directory is longer than PATH_MAX and also + corresponds to the / directory through an unprivileged mount + namespace. Reported by Qualys. + The following bugs are resolved with this release: [The release manager will add the list generated by diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c index e147a31a81..9d5787b6f4 100644 --- a/sysdeps/posix/getcwd.c +++ b/sysdeps/posix/getcwd.c @@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size) size_t allocated = size; size_t used; + /* A size of 1 byte is never useful. */ + if (allocated == 1) + { + __set_errno (ERANGE); + return NULL; + } + #if HAVE_MINIMALLY_WORKING_GETCWD /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and this is much slower than the system getcwd (at least on diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile index 85fc8cbf75..7ca9350c99 100644 --- a/sysdeps/unix/sysv/linux/Makefile +++ b/sysdeps/unix/sysv/linux/Makefile @@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \ sysdep_headers += bits/fcntl-linux.h -tests += tst-fallocate tst-fallocate64 tst-o_path-locks +tests += \ + tst-fallocate \ + tst-fallocate64 \ + tst-getcwd-smallbuff \ + tst-o_path-locks \ +# tests endif ifeq ($(subdir),elf) diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c new file mode 100644 index 0000000000..791dfe4d02 --- /dev/null +++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c @@ -0,0 +1,245 @@ +/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow + buffer when the CWD is too long and is also a mount target of /. See bug + #28769 or CVE-2021-3999 for more context. + Copyright The GNU Toolchain Authors. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#ifndef PATH_MAX +# define PATH_MAX 1024 +#endif + +static char *base; +#define BASENAME "tst-getcwd-smallbuff" +#define MOUNT_NAME "mpoint" +static int sockfd[2]; + +static void +do_cleanup (void) +{ + support_chdir_toolong_temp_directory (base); + TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0); + free (base); +} + +static void +send_fd (const int sock, const int fd) +{ + struct msghdr msg; + union + { + struct cmsghdr hdr; + char buf[CMSG_SPACE (sizeof (int))]; + } cmsgbuf; + struct cmsghdr *cmsg; + struct iovec vec; + char ch = 'A'; + ssize_t n; + + memset (&msg, 0, sizeof (msg)); + memset (&cmsgbuf, 0, sizeof (cmsgbuf)); + msg.msg_control = &cmsgbuf.buf; + msg.msg_controllen = sizeof (cmsgbuf.buf); + + cmsg = CMSG_FIRSTHDR (&msg); + cmsg->cmsg_len = CMSG_LEN (sizeof (int)); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + *(int *) CMSG_DATA (cmsg) = fd; + + vec.iov_base = &ch; + vec.iov_len = 1; + msg.msg_iov = &vec; + msg.msg_iovlen = 1; + + while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR); + + TEST_VERIFY_EXIT (n == 1); +} + +static int +recv_fd (const int sock) +{ + struct msghdr msg; + union + { + struct cmsghdr hdr; + char buf[CMSG_SPACE(sizeof(int))]; + } cmsgbuf; + struct cmsghdr *cmsg; + struct iovec vec; + ssize_t n; + char ch = '\0'; + int fd = -1; + + memset (&msg, 0, sizeof (msg)); + vec.iov_base = &ch; + vec.iov_len = 1; + msg.msg_iov = &vec; + msg.msg_iovlen = 1; + + memset (&cmsgbuf, 0, sizeof (cmsgbuf)); + msg.msg_control = &cmsgbuf.buf; + msg.msg_controllen = sizeof (cmsgbuf.buf); + + while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR); + if (n != 1 || ch != 'A') + return -1; + + cmsg = CMSG_FIRSTHDR (&msg); + if (cmsg == NULL) + return -1; + if (cmsg->cmsg_type != SCM_RIGHTS) + return -1; + fd = *(const int *) CMSG_DATA (cmsg); + if (fd < 0) + return -1; + return fd; +} + +static int +child_func (void * const arg) +{ + xclose (sockfd[0]); + const int sock = sockfd[1]; + char ch; + + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1); + TEST_VERIFY_EXIT (ch == '1'); + + if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL)) + FAIL_EXIT1 ("mount failed: %m\n"); + const int fd = xopen ("mpoint", + O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0); + + send_fd (sock, fd); + xclose (fd); + + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1); + TEST_VERIFY_EXIT (ch == 'a'); + + xclose (sock); + return 0; +} + +static void +update_map (char * const mapping, const char * const map_file) +{ + const size_t map_len = strlen (mapping); + + const int fd = xopen (map_file, O_WRONLY, 0); + xwrite (fd, mapping, map_len); + xclose (fd); +} + +static void +proc_setgroups_write (const long child_pid, const char * const str) +{ + const size_t str_len = strlen(str); + + char setgroups_path[64]; + snprintf (setgroups_path, sizeof (setgroups_path), + "/proc/%ld/setgroups", child_pid); + + const int fd = open (setgroups_path, O_WRONLY); + + if (fd < 0) + { + TEST_VERIFY_EXIT (errno == ENOENT); + FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid); + } + + xwrite (fd, str, str_len); + xclose(fd); +} + +static char child_stack[1024 * 1024]; + +int +do_test (void) +{ + base = support_create_and_chdir_toolong_temp_directory (BASENAME); + + xmkdir (MOUNT_NAME, S_IRWXU); + atexit (do_cleanup); + + TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0); + pid_t child_pid = xclone (child_func, NULL, child_stack, + sizeof (child_stack), + CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD); + + xclose (sockfd[1]); + const int sock = sockfd[0]; + + char map_path[64], map_buf[64]; + snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map", + (long) child_pid); + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid()); + update_map (map_buf, map_path); + + proc_setgroups_write ((long) child_pid, "deny"); + snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map", + (long) child_pid); + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid()); + update_map (map_buf, map_path); + + TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1); + const int fd = recv_fd (sock); + TEST_VERIFY_EXIT (fd >= 0); + TEST_VERIFY_EXIT (fchdir (fd) == 0); + + static char buf[2 * 10 + 1]; + memset (buf, 'A', sizeof(buf)); + + /* Finally, call getcwd and check if it resulted in a buffer underflow. */ + char * cwd = getcwd (buf + sizeof(buf) / 2, 1); + TEST_VERIFY (cwd == NULL); + TEST_VERIFY (errno == ERANGE); + + for (int i = 0; i < sizeof (buf); i++) + if (buf[i] != 'A') + { + printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]); + support_record_failure (); + } + + TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1); + xclose (sock); + TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid); + + return 0; +} + +#define CLEANUP_HANDLER do_cleanup +#include