diff options
Diffstat (limited to 'lib/open.c')
| -rw-r--r-- | lib/open.c | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/lib/open.c b/lib/open.c new file mode 100644 index 0000000..0f7c6e9 --- /dev/null +++ b/lib/open.c @@ -0,0 +1,209 @@ +/* Open a descriptor to a file. + Copyright (C) 2007-2020 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 Bruno Haible <bruno@clisp.org>, 2007. */ + +/* If the user's config.h happens to include <fcntl.h>, let it include only + the system's <fcntl.h> here, so that orig_open doesn't recurse to + rpl_open. */ +#define __need_system_fcntl_h +#include <config.h> + +/* Get the original definition of open. It might be defined as a macro. */ +#include <fcntl.h> +#include <sys/types.h> +#undef __need_system_fcntl_h + +static int +orig_open (const char *filename, int flags, mode_t mode) +{ +#if defined _WIN32 && !defined __CYGWIN__ + return _open (filename, flags, mode); +#else + return open (filename, flags, mode); +#endif +} + +/* Specification. */ +/* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates + this include because of the preliminary #include <fcntl.h> above. */ +#include "fcntl.h" + +#include "cloexec.h" + +#include <errno.h> +#include <stdarg.h> +#include <string.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <unistd.h> + +#ifndef REPLACE_OPEN_DIRECTORY +# define REPLACE_OPEN_DIRECTORY 0 +#endif + +int +open (const char *filename, int flags, ...) +{ + /* 0 = unknown, 1 = yes, -1 = no. */ +#if GNULIB_defined_O_CLOEXEC + int have_cloexec = -1; +#else + static int have_cloexec; +#endif + + mode_t mode; + int fd; + + mode = 0; + if (flags & O_CREAT) + { + va_list arg; + va_start (arg, flags); + + /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4 + creates crashing code when 'mode_t' is smaller than 'int'. */ + mode = va_arg (arg, PROMOTED_MODE_T); + + va_end (arg); + } + +#if GNULIB_defined_O_NONBLOCK + /* The only known platform that lacks O_NONBLOCK is mingw, but it + also lacks named pipes and Unix sockets, which are the only two + file types that require non-blocking handling in open(). + Therefore, it is safe to ignore O_NONBLOCK here. It is handy + that mingw also lacks openat(), so that is also covered here. */ + flags &= ~O_NONBLOCK; +#endif + +#if defined _WIN32 && ! defined __CYGWIN__ + if (strcmp (filename, "/dev/null") == 0) + filename = "NUL"; +#endif + +#if OPEN_TRAILING_SLASH_BUG + /* Fail if one of O_CREAT, O_WRONLY, O_RDWR is specified and the filename + ends in a slash, as POSIX says such a filename must name a directory + <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: + "A pathname that contains at least one non-<slash> character and that + ends with one or more trailing <slash> characters shall not be resolved + successfully unless the last pathname component before the trailing + <slash> characters names an existing directory" + If the named file already exists as a directory, then + - if O_CREAT is specified, open() must fail because of the semantics + of O_CREAT, + - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX + <https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html> + says that it fails with errno = EISDIR in this case. + If the named file does not exist or does not name a directory, then + - if O_CREAT is specified, open() must fail since open() cannot create + directories, + - if O_WRONLY or O_RDWR is specified, open() must fail because the + file does not contain a '.' directory. */ + if ((flags & O_CREAT) + || (flags & O_ACCMODE) == O_RDWR + || (flags & O_ACCMODE) == O_WRONLY) + { + size_t len = strlen (filename); + if (len > 0 && filename[len - 1] == '/') + { + errno = EISDIR; + return -1; + } + } +#endif + + fd = orig_open (filename, + flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode); + + if (flags & O_CLOEXEC) + { + if (! have_cloexec) + { + if (0 <= fd) + have_cloexec = 1; + else if (errno == EINVAL) + { + fd = orig_open (filename, flags & ~O_CLOEXEC, mode); + have_cloexec = -1; + } + } + if (have_cloexec < 0 && 0 <= fd) + set_cloexec_flag (fd, true); + } + + +#if REPLACE_FCHDIR + /* Implementing fchdir and fdopendir requires the ability to open a + directory file descriptor. If open doesn't support that (as on + mingw), we use a dummy file that behaves the same as directories + on Linux (ie. always reports EOF on attempts to read()), and + override fstat() in fchdir.c to hide the fact that we have a + dummy. */ + if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES + && ((flags & O_ACCMODE) == O_RDONLY + || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH))) + { + struct stat statbuf; + if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode)) + { + /* Maximum recursion depth of 1. */ + fd = open ("/dev/null", flags, mode); + if (0 <= fd) + fd = _gl_register_fd (fd, filename); + } + else + errno = EACCES; + } +#endif + +#if OPEN_TRAILING_SLASH_BUG + /* If the filename ends in a slash and fd does not refer to a directory, + then fail. + Rationale: POSIX says such a filename must name a directory + <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: + "A pathname that contains at least one non-<slash> character and that + ends with one or more trailing <slash> characters shall not be resolved + successfully unless the last pathname component before the trailing + <slash> characters names an existing directory" + If the named file without the slash is not a directory, open() must fail + with ENOTDIR. */ + if (fd >= 0) + { + /* We know len is positive, since open did not fail with ENOENT. */ + size_t len = strlen (filename); + if (filename[len - 1] == '/') + { + struct stat statbuf; + + if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode)) + { + close (fd); + errno = ENOTDIR; + return -1; + } + } + } +#endif + +#if REPLACE_FCHDIR + if (!REPLACE_OPEN_DIRECTORY && 0 <= fd) + fd = _gl_register_fd (fd, filename); +#endif + + return fd; +} |