bug#33847: 27.0.50; emacsclient does not find server socket

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> Looks like you didn't attach the right patch?

Yup; 2nd attempt now.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index 1c8b442700..c12e83dd2f 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -33,7 +33,7 @@ GNULIB_MODULES=
   crypto/md5-buffer crypto/sha1-buffer crypto/sha256-buffer 
crypto/sha512-buffer
   d-type diffseq double-slash-root dtoastr dtotimespec dup2
   environ execinfo explicit_bzero faccessat
-  fchmodat fcntl fcntl-h fdopendir
+  fchmodat fcntl fcntl-h fdopendir file-has-acl
   filemode filename filevercmp flexmember fpieee
   free-posix fstatat fsusage fsync futimens
   getloadavg getopt-gnu getrandom gettime gettimeofday gitlog-to-changelog
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 12ced4aadb..3972cbba45 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -80,6 +80,7 @@ Copyright (C) 1986-1987, 1994, 1999-2021 Free Software 
Foundation, Inc.
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <acl.h>
 #include <filename.h>
 #include <intprops.h>
 #include <min-max.h>
@@ -91,6 +92,10 @@ Copyright (C) 1986-1987, 1994, 1999-2021 Free Software 
Foundation, Inc.
 # pragma GCC diagnostic ignored "-Wformat-truncation=2"
 #endif
 
+#ifndef O_PATH
+# define O_PATH O_SEARCH
+#endif
+

 /* Name used to invoke this program.  */
 static char const *progname;
@@ -1128,24 +1133,74 @@ process_grouping (void)
 
 #ifdef SOCKETS_IN_FILE_SYSTEM
 
-/* Return the file status of NAME, ordinarily a socket.
-   It should be owned by UID.  Return one of the following:
-  >0 - 'stat' failed with this errno value
-  -1 - isn't owned by us
-   0 - success: none of the above */
+/* A local socket address.  The union avoids the need to cast.  */
+union local_sockaddr
+{
+  struct sockaddr_un un;
+  struct sockaddr sa;
+};
+
+/* Relative to the directory DIRFD, connect the socket file named ADDR
+   to the socket S.  Return 0 if successful, -1 if DIRFD is not
+   AT_FDCWD and DIRFD's permissions would allow a symlink attack, an
+   errno otherwise.  */
 
 static int
-socket_status (const char *name, uid_t uid)
+connect_socket (int dirfd, char const *addr, int s, uid_t uid)
 {
-  struct stat statbfr;
+  int sock_status = 0;
 
-  if (stat (name, &statbfr) != 0)
-    return errno;
+  union local_sockaddr server;
+  if (sizeof server.un.sun_path <= strlen (addr))
+    return ENAMETOOLONG;
+  server.un.sun_family = AF_UNIX;
+  strcpy (server.un.sun_path, addr);
 
-  if (statbfr.st_uid != uid)
-    return -1;
+  /* If -1, WDFD is not set yet.  If nonnegative, WDFD is a file
+     descriptor for the initial working directory.  Otherwise -1 - WDFD is
+     the error number for the initial working directory.  */
+  static int wdfd = -1;
 
-  return 0;
+  if (dirfd != AT_FDCWD)
+    {
+      /* Fail if DIRFD's permissions are bogus.  */
+      struct stat st;
+      if (fstat (dirfd, &st) != 0)
+       return errno;
+      if (st.st_uid != uid || (st.st_mode & (S_IWGRP | S_IWOTH)))
+       return -1;
+
+      if (wdfd == -1)
+       {
+         /* Save the initial working directory.  */
+         wdfd = open (".", O_PATH | O_CLOEXEC);
+         if (wdfd < 0)
+           wdfd = -1 - errno;
+       }
+      if (wdfd < 0)
+       return -1 - wdfd;
+      if (fchdir (dirfd) != 0)
+       return errno;
+
+      /* Fail if DIRFD has an ACL, which means its permissions are
+        almost surely bogus.  */
+      int has_acl = file_has_acl (".", &st);
+      if (has_acl)
+       sock_status = has_acl < 0 ? errno : -1;
+    }
+
+  if (!sock_status)
+    sock_status = connect (s, &server.sa, sizeof server.un) == 0 ? 0 : errno;
+
+  /* Fail immediately if we cannot change back to the initial working
+     directory, as that can mess up the rest of execution.  */
+  if (dirfd != AT_FDCWD && fchdir (wdfd) != 0)
+    {
+      message (true, "%s: .: %s\n", progname, strerror (errno));
+      exit (EXIT_FAILURE);
+    }
+
+  return sock_status;
 }
 

@@ -1322,32 +1377,49 @@ act_on_signals (HSOCKET emacs_socket)
     }
 }
 
-/* Create in SOCKNAME (of size SOCKNAMESIZE) a name for a local socket.
-   The first TMPDIRLEN bytes of SOCKNAME are already initialized to be
-   the name of a temporary directory.  Use UID and SERVER_NAME to
-   concoct the name.  Return the total length of the name if successful,
-   -1 if it does not fit (and store a truncated name in that case).
-   Fail if TMPDIRLEN is out of range.  */
+enum { socknamesize = sizeof ((struct sockaddr_un *) NULL)->sun_path };
+
+/* Given a local socket S, create in *SOCKNAME a name for a local socket
+   and connect to that socket.  The first TMPDIRLEN bytes of *SOCKNAME are
+   already initialized to be the name of a temporary directory.
+   Use UID and SERVER_NAME to concoct the name.  Return 0 if
+   successful, -1 if the socket's parent directory is not safe, and an
+   errno if there is some other problem.  */
 
 static int
-local_sockname (char *sockname, int socknamesize, int tmpdirlen,
-               uintmax_t uid, char const *server_name)
+local_sockname (int s, char sockname[socknamesize], int tmpdirlen,
+               uid_t uid, char const *server_name)
 {
   /* If ! (0 <= TMPDIRLEN && TMPDIRLEN < SOCKNAMESIZE) the truncated
      temporary directory name is already in SOCKNAME, so nothing more
      need be stored.  */
-  if (0 <= tmpdirlen)
-    {
-      int remaining = socknamesize - tmpdirlen;
-      if (0 < remaining)
-       {
-         int suffixlen = snprintf (&sockname[tmpdirlen], remaining,
-                                   "/emacs%"PRIuMAX"/%s", uid, server_name);
-         if (0 <= suffixlen && suffixlen < remaining)
-           return tmpdirlen + suffixlen;
-       }
-    }
-  return -1;
+  if (! (0 <= tmpdirlen && tmpdirlen < socknamesize))
+    return ENAMETOOLONG;
+
+  /* Put the full address name into the buffer, since the caller might
+     need it for diagnostics.  But don't overrun the buffer.  */
+  uintmax_t uidmax = uid;
+  int emacsdirlen;
+  int suffixlen = snprintf (sockname + tmpdirlen, socknamesize - tmpdirlen,
+                           "/emacs%"PRIuMAX"%n/%s", uidmax, &emacsdirlen,
+                           server_name);
+  if (! (0 <= suffixlen && suffixlen < socknamesize - tmpdirlen))
+    return ENAMETOOLONG;
+
+  /* Make sure the address's parent directory is not a symlink and is
+     this user's directory and does not let others write to it; this
+     fends off some symlink attacks.  To avoid races, keep the parent
+     directory open while checking.  */
+  char *emacsdirend = sockname + tmpdirlen + emacsdirlen;
+  *emacsdirend = '\0';
+  int dir = openat (AT_FDCWD, sockname,
+                   O_PATH | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  *emacsdirend = '/';
+  if (dir < 0)
+    return errno;
+  int sock_status = connect_socket (dir, server_name, s, uid);
+  close (dir);
+  return sock_status;
 }
 
 /* Create a local socket for SERVER_NAME and connect it to Emacs.  If
@@ -1358,28 +1430,43 @@ local_sockname (char *sockname, int socknamesize, int 
tmpdirlen,
 static HSOCKET
 set_local_socket (char const *server_name)
 {
-  union {
-    struct sockaddr_un un;
-    struct sockaddr sa;
-  } server = {{ .sun_family = AF_UNIX }};
+  union local_sockaddr server;
+  int sock_status;
   char *sockname = server.un.sun_path;
-  enum { socknamesize = sizeof server.un.sun_path };
   int tmpdirlen = -1;
   int socknamelen = -1;
   uid_t uid = geteuid ();
   bool tmpdir_used = false;
+  int s = cloexec_socket (AF_UNIX, SOCK_STREAM, 0);
+  if (s < 0)
+    {
+      message (true, "%s: can't create socket: %s\n",
+              progname, strerror (errno));
+      fail ();
+    }
 
   if (strchr (server_name, '/')
       || (ISSLASH ('\\') && strchr (server_name, '\\')))
-    socknamelen = snprintf (sockname, socknamesize, "%s", server_name);
+    {
+      socknamelen = snprintf (sockname, socknamesize, "%s", server_name);
+      sock_status = (0 <= socknamelen && socknamelen < socknamesize
+                    ? connect_socket (AT_FDCWD, sockname, s, 0)
+                    : ENAMETOOLONG);
+    }
   else
     {
       /* socket_name is a file name component.  */
+      sock_status = ENOENT;
       char const *xdg_runtime_dir = egetenv ("XDG_RUNTIME_DIR");
       if (xdg_runtime_dir)
-       socknamelen = snprintf (sockname, socknamesize, "%s/emacs/%s",
-                               xdg_runtime_dir, server_name);
-      else
+       {
+         socknamelen = snprintf (sockname, socknamesize, "%s/emacs/%s",
+                                 xdg_runtime_dir, server_name);
+         sock_status = (0 <= socknamelen && socknamelen < socknamesize
+                        ? connect_socket (AT_FDCWD, sockname, s, 0)
+                        : ENAMETOOLONG);
+       }
+      if (sock_status == ENOENT)
        {
          char const *tmpdir = egetenv ("TMPDIR");
          if (tmpdir)
@@ -1398,23 +1485,24 @@ set_local_socket (char const *server_name)
              if (tmpdirlen < 0)
                tmpdirlen = snprintf (sockname, socknamesize, "/tmp");
            }
-         socknamelen = local_sockname (sockname, socknamesize, tmpdirlen,
+         sock_status = local_sockname (s, sockname, tmpdirlen,
                                        uid, server_name);
          tmpdir_used = true;
        }
     }
 
-  if (! (0 <= socknamelen && socknamelen < socknamesize))
+  if (sock_status == 0)
+    return s;
+
+  if (sock_status == ENAMETOOLONG)
     {
       message (true, "%s: socket-name %s... too long\n", progname, sockname);
       fail ();
     }
 
-  /* See if the socket exists, and if it's owned by us. */
-  int sock_status = socket_status (sockname, uid);
-  if (sock_status)
+  if (tmpdir_used)
     {
-      /* Failing that, see if LOGNAME or USER exist and differ from
+      /* See whether LOGNAME or USER exist and differ from
         our euid.  If so, look for a socket based on the UID
         associated with the name.  This is reminiscent of the logic
         that init_editfns uses to set the global Vuser_full_name.  */
@@ -1431,48 +1519,26 @@ set_local_socket (char const *server_name)
          if (pw && pw->pw_uid != uid)
            {
              /* We're running under su, apparently. */
-             socknamelen = local_sockname (sockname, socknamesize, tmpdirlen,
+             sock_status = local_sockname (s, sockname, tmpdirlen,
                                            pw->pw_uid, server_name);
-             if (socknamelen < 0)
+             if (sock_status == 0)
+               return s;
+             if (sock_status == ENAMETOOLONG)
                {
                  message (true, "%s: socket-name %s... too long\n",
                           progname, sockname);
                  exit (EXIT_FAILURE);
                }
-
-             sock_status = socket_status (sockname, uid);
            }
        }
     }
 
-  if (sock_status == 0)
-    {
-      HSOCKET s = cloexec_socket (AF_UNIX, SOCK_STREAM, 0);
-      if (s < 0)
-       {
-         message (true, "%s: socket: %s\n", progname, strerror (errno));
-         return INVALID_SOCKET;
-       }
-      if (connect (s, &server.sa, sizeof server.un) != 0)
-       {
-         message (true, "%s: connect: %s\n", progname, strerror (errno));
-         CLOSE_SOCKET (s);
-         return INVALID_SOCKET;
-       }
-
-      struct stat connect_stat;
-      if (fstat (s, &connect_stat) != 0)
-       sock_status = errno;
-      else if (connect_stat.st_uid == uid)
-       return s;
-      else
-       sock_status = -1;
-
-      CLOSE_SOCKET (s);
-    }
+  close (s);
 
-  if (sock_status < 0)
-    message (true, "%s: Invalid socket owner\n", progname);
+  if (sock_status == -1)
+    message (true,
+            "%s: Invalid permissions on parent directory of socket: %s\n",
+            progname, sockname);
   else if (sock_status == ENOENT)
     {
       if (tmpdir_used)
@@ -1502,7 +1568,7 @@ set_local_socket (char const *server_name)
        }
     }
   else
-    message (true, "%s: can't stat %s: %s\n",
+    message (true, "%s: can't connect to %s: %s\n",
             progname, sockname, strerror (sock_status));
 
   return INVALID_SOCKET;
diff --git a/lib/file-has-acl.c b/lib/file-has-acl.c
new file mode 100644
index 0000000000..c667ae9d24
--- /dev/null
+++ b/lib/file-has-acl.c
@@ -0,0 +1,510 @@
+/* Test whether a file has a nontrivial ACL.  -*- coding: utf-8 -*-
+
+   Copyright (C) 2002-2003, 2005-2020 Free Software Foundation, 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 3 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 <https://www.gnu.org/licenses/>.
+
+   Written by Paul Eggert, Andreas Grünbacher, and Bruno Haible.  */
+
+/* Without this pragma, gcc 4.7.0 20120126 may suggest that the
+   file_has_acl function might be candidate for attribute 'const'  */
+#if (__GNUC__ == 4 && 6 <= __GNUC_MINOR__) || 4 < __GNUC__
+# pragma GCC diagnostic ignored "-Wsuggest-attribute=const"
+#endif
+
+#include <config.h>
+
+#include "acl.h"
+
+#include "acl-internal.h"
+
+#if GETXATTR_WITH_POSIX_ACLS
+# include <sys/xattr.h>
+# include <linux/xattr.h>
+#endif
+
+/* Return 1 if NAME has a nontrivial access control list,
+   0 if ACLs are not supported, or if NAME has no or only a base ACL,
+   and -1 (setting errno) on error.  Note callers can determine
+   if ACLs are not supported as errno is set in that case also.
+   SB must be set to the stat buffer of NAME,
+   obtained through stat() or lstat().  */
+
+int
+file_has_acl (char const *name, struct stat const *sb)
+{
+#if USE_ACL
+  if (! S_ISLNK (sb->st_mode))
+    {
+
+# if GETXATTR_WITH_POSIX_ACLS
+
+      ssize_t ret;
+
+      ret = getxattr (name, XATTR_NAME_POSIX_ACL_ACCESS, NULL, 0);
+      if (ret < 0 && errno == ENODATA)
+        ret = 0;
+      else if (ret > 0)
+        return 1;
+
+      if (ret == 0 && S_ISDIR (sb->st_mode))
+        {
+          ret = getxattr (name, XATTR_NAME_POSIX_ACL_DEFAULT, NULL, 0);
+          if (ret < 0 && errno == ENODATA)
+            ret = 0;
+          else if (ret > 0)
+            return 1;
+        }
+
+      if (ret < 0)
+        return - acl_errno_valid (errno);
+      return ret;
+
+# elif HAVE_ACL_GET_FILE
+
+      /* POSIX 1003.1e (draft 17 -- abandoned) specific version.  */
+      /* Linux, FreeBSD, Mac OS X, IRIX, Tru64, Cygwin >= 2.5 */
+      int ret;
+
+      if (HAVE_ACL_EXTENDED_FILE) /* Linux */
+        {
+          /* On Linux, acl_extended_file is an optimized function: It only
+             makes two calls to getxattr(), one for ACL_TYPE_ACCESS, one for
+             ACL_TYPE_DEFAULT.  */
+          ret = acl_extended_file (name);
+        }
+      else /* FreeBSD, Mac OS X, IRIX, Tru64, Cygwin >= 2.5 */
+        {
+#  if HAVE_ACL_TYPE_EXTENDED /* Mac OS X */
+          /* On Mac OS X, acl_get_file (name, ACL_TYPE_ACCESS)
+             and acl_get_file (name, ACL_TYPE_DEFAULT)
+             always return NULL / EINVAL.  There is no point in making
+             these two useless calls.  The real ACL is retrieved through
+             acl_get_file (name, ACL_TYPE_EXTENDED).  */
+          acl_t acl = acl_get_file (name, ACL_TYPE_EXTENDED);
+          if (acl)
+            {
+              ret = acl_extended_nontrivial (acl);
+              acl_free (acl);
+            }
+          else
+            ret = -1;
+#  else /* FreeBSD, IRIX, Tru64, Cygwin >= 2.5 */
+          acl_t acl = acl_get_file (name, ACL_TYPE_ACCESS);
+          if (acl)
+            {
+              int saved_errno;
+
+              ret = acl_access_nontrivial (acl);
+              saved_errno = errno;
+              acl_free (acl);
+              errno = saved_errno;
+#   if HAVE_ACL_FREE_TEXT /* Tru64 */
+              /* On OSF/1, acl_get_file (name, ACL_TYPE_DEFAULT) always
+                 returns NULL with errno not set.  There is no point in
+                 making this call.  */
+#   else /* FreeBSD, IRIX, Cygwin >= 2.5 */
+              /* On Linux, FreeBSD, IRIX, acl_get_file (name, ACL_TYPE_ACCESS)
+                 and acl_get_file (name, ACL_TYPE_DEFAULT) on a directory
+                 either both succeed or both fail; it depends on the
+                 file system.  Therefore there is no point in making the second
+                 call if the first one already failed.  */
+              if (ret == 0 && S_ISDIR (sb->st_mode))
+                {
+                  acl = acl_get_file (name, ACL_TYPE_DEFAULT);
+                  if (acl)
+                    {
+#    ifdef __CYGWIN__ /* Cygwin >= 2.5 */
+                      ret = acl_access_nontrivial (acl);
+                      saved_errno = errno;
+                      acl_free (acl);
+                      errno = saved_errno;
+#    else
+                      ret = (0 < acl_entries (acl));
+                      acl_free (acl);
+#    endif
+                    }
+                  else
+                    ret = -1;
+                }
+#   endif
+            }
+          else
+            ret = -1;
+#  endif
+        }
+      if (ret < 0)
+        return - acl_errno_valid (errno);
+      return ret;
+
+# elif HAVE_FACL && defined GETACL /* Solaris, Cygwin < 2.5, not HP-UX */
+
+#  if defined ACL_NO_TRIVIAL
+
+      /* Solaris 10 (newer version), which has additional API declared in
+         <sys/acl.h> (acl_t) and implemented in libsec (acl_set, acl_trivial,
+         acl_fromtext, ...).  */
+      return acl_trivial (name);
+
+#  else /* Solaris, Cygwin, general case */
+
+      /* Solaris 2.5 through Solaris 10, Cygwin, and contemporaneous versions
+         of Unixware.  The acl() call returns the access and default ACL both
+         at once.  */
+      {
+        /* Initially, try to read the entries into a stack-allocated buffer.
+           Use malloc if it does not fit.  */
+        enum
+          {
+            alloc_init = 4000 / sizeof (aclent_t), /* >= 3 */
+            alloc_max = MIN (INT_MAX, SIZE_MAX / sizeof (aclent_t))
+          };
+        aclent_t buf[alloc_init];
+        size_t alloc = alloc_init;
+        aclent_t *entries = buf;
+        aclent_t *malloced = NULL;
+        int count;
+
+        for (;;)
+          {
+            count = acl (name, GETACL, alloc, entries);
+            if (count < 0 && errno == ENOSPC)
+              {
+                /* Increase the size of the buffer.  */
+                free (malloced);
+                if (alloc > alloc_max / 2)
+                  {
+                    errno = ENOMEM;
+                    return -1;
+                  }
+                alloc = 2 * alloc; /* <= alloc_max */
+                entries = malloced =
+                  (aclent_t *) malloc (alloc * sizeof (aclent_t));
+                if (entries == NULL)
+                  {
+                    errno = ENOMEM;
+                    return -1;
+                  }
+                continue;
+              }
+            break;
+          }
+        if (count < 0)
+          {
+            if (errno == ENOSYS || errno == ENOTSUP)
+              ;
+            else
+              {
+                int saved_errno = errno;
+                free (malloced);
+                errno = saved_errno;
+                return -1;
+              }
+          }
+        else if (count == 0)
+          ;
+        else
+          {
+            /* Don't use MIN_ACL_ENTRIES:  It's set to 4 on Cygwin, but Cygwin
+               returns only 3 entries for files with no ACL.  But this is safe:
+               If there are more than 4 entries, there cannot be only the
+               "user::", "group::", "other:", and "mask:" entries.  */
+            if (count > 4)
+              {
+                free (malloced);
+                return 1;
+              }
+
+            if (acl_nontrivial (count, entries))
+              {
+                free (malloced);
+                return 1;
+              }
+          }
+        free (malloced);
+      }
+
+#   ifdef ACE_GETACL
+      /* Solaris also has a different variant of ACLs, used in ZFS and NFSv4
+         file systems (whereas the other ones are used in UFS file systems).  
*/
+      {
+        /* Initially, try to read the entries into a stack-allocated buffer.
+           Use malloc if it does not fit.  */
+        enum
+          {
+            alloc_init = 4000 / sizeof (ace_t), /* >= 3 */
+            alloc_max = MIN (INT_MAX, SIZE_MAX / sizeof (ace_t))
+          };
+        ace_t buf[alloc_init];
+        size_t alloc = alloc_init;
+        ace_t *entries = buf;
+        ace_t *malloced = NULL;
+        int count;
+
+        for (;;)
+          {
+            count = acl (name, ACE_GETACL, alloc, entries);
+            if (count < 0 && errno == ENOSPC)
+              {
+                /* Increase the size of the buffer.  */
+                free (malloced);
+                if (alloc > alloc_max / 2)
+                  {
+                    errno = ENOMEM;
+                    return -1;
+                  }
+                alloc = 2 * alloc; /* <= alloc_max */
+                entries = malloced = (ace_t *) malloc (alloc * sizeof (ace_t));
+                if (entries == NULL)
+                  {
+                    errno = ENOMEM;
+                    return -1;
+                  }
+                continue;
+              }
+            break;
+          }
+        if (count < 0)
+          {
+            if (errno == ENOSYS || errno == EINVAL)
+              ;
+            else
+              {
+                int saved_errno = errno;
+                free (malloced);
+                errno = saved_errno;
+                return -1;
+              }
+          }
+        else if (count == 0)
+          ;
+        else
+          {
+            /* In the old (original Solaris 10) convention:
+               If there are more than 3 entries, there cannot be only the
+               ACE_OWNER, ACE_GROUP, ACE_OTHER entries.
+               In the newer Solaris 10 and Solaris 11 convention:
+               If there are more than 6 entries, there cannot be only the
+               ACE_OWNER, ACE_GROUP, ACE_EVERYONE entries, each once with
+               NEW_ACE_ACCESS_ALLOWED_ACE_TYPE and once with
+               NEW_ACE_ACCESS_DENIED_ACE_TYPE.  */
+            if (count > 6)
+              {
+                free (malloced);
+                return 1;
+              }
+
+            if (acl_ace_nontrivial (count, entries))
+              {
+                free (malloced);
+                return 1;
+              }
+          }
+        free (malloced);
+      }
+#   endif
+
+      return 0;
+#  endif
+
+# elif HAVE_GETACL /* HP-UX */
+
+      {
+        struct acl_entry entries[NACLENTRIES];
+        int count;
+
+        count = getacl (name, NACLENTRIES, entries);
+
+        if (count < 0)
+          {
+            /* ENOSYS is seen on newer HP-UX versions.
+               EOPNOTSUPP is typically seen on NFS mounts.
+               ENOTSUP was seen on Quantum StorNext file systems (cvfs).  */
+            if (errno == ENOSYS || errno == EOPNOTSUPP || errno == ENOTSUP)
+              ;
+            else
+              return -1;
+          }
+        else if (count == 0)
+          return 0;
+        else /* count > 0 */
+          {
+            if (count > NACLENTRIES)
+              /* If NACLENTRIES cannot be trusted, use dynamic memory
+                 allocation.  */
+              abort ();
+
+            /* If there are more than 3 entries, there cannot be only the
+               (uid,%), (%,gid), (%,%) entries.  */
+            if (count > 3)
+              return 1;
+
+            {
+              struct stat statbuf;
+
+              if (stat (name, &statbuf) < 0)
+                return -1;
+
+              return acl_nontrivial (count, entries);
+            }
+          }
+      }
+
+#  if HAVE_ACLV_H /* HP-UX >= 11.11 */
+
+      {
+        struct acl entries[NACLVENTRIES];
+        int count;
+
+        count = acl ((char *) name, ACL_GET, NACLVENTRIES, entries);
+
+        if (count < 0)
+          {
+            /* EOPNOTSUPP is seen on NFS in HP-UX 11.11, 11.23.
+               EINVAL is seen on NFS in HP-UX 11.31.  */
+            if (errno == ENOSYS || errno == EOPNOTSUPP || errno == EINVAL)
+              ;
+            else
+              return -1;
+          }
+        else if (count == 0)
+          return 0;
+        else /* count > 0 */
+          {
+            if (count > NACLVENTRIES)
+              /* If NACLVENTRIES cannot be trusted, use dynamic memory
+                 allocation.  */
+              abort ();
+
+            /* If there are more than 4 entries, there cannot be only the
+               four base ACL entries.  */
+            if (count > 4)
+              return 1;
+
+            return aclv_nontrivial (count, entries);
+          }
+      }
+
+#  endif
+
+# elif HAVE_ACLX_GET && defined ACL_AIX_WIP /* AIX */
+
+      acl_type_t type;
+      char aclbuf[1024];
+      void *acl = aclbuf;
+      size_t aclsize = sizeof (aclbuf);
+      mode_t mode;
+
+      for (;;)
+        {
+          /* The docs say that type being 0 is equivalent to ACL_ANY, but it
+             is not true, in AIX 5.3.  */
+          type.u64 = ACL_ANY;
+          if (aclx_get (name, 0, &type, aclbuf, &aclsize, &mode) >= 0)
+            break;
+          if (errno == ENOSYS)
+            return 0;
+          if (errno != ENOSPC)
+            {
+              if (acl != aclbuf)
+                {
+                  int saved_errno = errno;
+                  free (acl);
+                  errno = saved_errno;
+                }
+              return -1;
+            }
+          aclsize = 2 * aclsize;
+          if (acl != aclbuf)
+            free (acl);
+          acl = malloc (aclsize);
+          if (acl == NULL)
+            {
+              errno = ENOMEM;
+              return -1;
+            }
+        }
+
+      if (type.u64 == ACL_AIXC)
+        {
+          int result = acl_nontrivial ((struct acl *) acl);
+          if (acl != aclbuf)
+            free (acl);
+          return result;
+        }
+      else if (type.u64 == ACL_NFS4)
+        {
+          int result = acl_nfs4_nontrivial ((nfs4_acl_int_t *) acl);
+          if (acl != aclbuf)
+            free (acl);
+          return result;
+        }
+      else
+        {
+          /* A newer type of ACL has been introduced in the system.
+             We should better support it.  */
+          if (acl != aclbuf)
+            free (acl);
+          errno = EINVAL;
+          return -1;
+        }
+
+# elif HAVE_STATACL /* older AIX */
+
+      union { struct acl a; char room[4096]; } u;
+
+      if (statacl ((char *) name, STX_NORMAL, &u.a, sizeof (u)) < 0)
+        return -1;
+
+      return acl_nontrivial (&u.a);
+
+# elif HAVE_ACLSORT /* NonStop Kernel */
+
+      {
+        struct acl entries[NACLENTRIES];
+        int count;
+
+        count = acl ((char *) name, ACL_GET, NACLENTRIES, entries);
+
+        if (count < 0)
+          {
+            if (errno == ENOSYS || errno == ENOTSUP)
+              ;
+            else
+              return -1;
+          }
+        else if (count == 0)
+          return 0;
+        else /* count > 0 */
+          {
+            if (count > NACLENTRIES)
+              /* If NACLENTRIES cannot be trusted, use dynamic memory
+                 allocation.  */
+              abort ();
+
+            /* If there are more than 4 entries, there cannot be only the
+               four base ACL entries.  */
+            if (count > 4)
+              return 1;
+
+            return acl_nontrivial (count, entries);
+          }
+      }
+
+# endif
+    }
+#endif
+
+  return 0;
+}
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 07736f9b8b..0b9aaf6d9e 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -98,6 +98,7 @@
 #  fcntl \
 #  fcntl-h \
 #  fdopendir \
+#  file-has-acl \
 #  filemode \
 #  filename \
 #  filevercmp \
@@ -1788,6 +1789,16 @@ EXTRA_libgnu_a_SOURCES += fdopendir.c
 endif
 ## end   gnulib module fdopendir
 
+## begin gnulib module file-has-acl
+ifeq (,$(OMIT_GNULIB_MODULE_file-has-acl))
+
+libgnu_a_SOURCES += file-has-acl.c
+
+EXTRA_DIST += acl-internal.h
+
+endif
+## end   gnulib module file-has-acl
+
 ## begin gnulib module filemode
 ifeq (,$(OMIT_GNULIB_MODULE_filemode))
 
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index cd6f7b4bbd..05e7faa993 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -89,6 +89,7 @@ AC_DEFUN
   # Code from module fcntl:
   # Code from module fcntl-h:
   # Code from module fdopendir:
+  # Code from module file-has-acl:
   # Code from module filemode:
   # Code from module filename:
   # Code from module filevercmp:
@@ -287,6 +288,7 @@ AC_DEFUN
   fi
   gl_DIRENT_MODULE_INDICATOR([fdopendir])
   gl_MODULE_INDICATOR([fdopendir])
+  gl_FILE_HAS_ACL
   gl_FILEMODE
   AC_C_FLEXIBLE_ARRAY_MEMBER
   gl_FUNC_FPENDING
@@ -1045,6 +1047,7 @@ AC_DEFUN
   lib/fcntl.c
   lib/fcntl.in.h
   lib/fdopendir.c
+  lib/file-has-acl.c
   lib/filemode.c
   lib/filemode.h
   lib/filename.h