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/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
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
<https://www.gnu.org/licenses/>. */
#include <unistd.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <paths.h>
#include <confstr.h>
#include <sys/param.h>
#ifndef PATH_MAX
# ifdef MAXPATHLEN
# define PATH_MAX MAXPATHLEN
# else
# define PATH_MAX 1024
# endif
#endif
/* The file is accessible but it is not an executable file. Invoke
the shell to interpret it as a script. */
static void
maybe_script_execute (const char *file, char *const argv[], char *const envp[])
{
ptrdiff_t argc;
for (argc = 0; argv[argc] != NULL; argc++)
{
if (argc == INT_MAX - 1)
{
errno = E2BIG;
return;
}
}
/* Construct an argument list for the shell based on original arguments:
1. Empty list (argv = { NULL }, argc = 1 }: new argv will contain 3
arguments - default shell, script to execute, and ending NULL.
2. Non empty argument list (argc = { ..., NULL }, argc > 1}: new argv
will contain also the default shell and the script to execute. It
will also skip the script name in arguments and only copy script
arguments. */
char *new_argv[argc > 1 ? 2 + argc : 3];
new_argv[0] = (char *) _PATH_BSHELL;
new_argv[1] = (char *) file;
if (argc > 1)
memcpy (new_argv + 2, argv + 1, argc * sizeof (char *));
else
new_argv[2] = NULL;
/* Execute the shell. */
__execve (new_argv[0], new_argv, envp);
}
static int
__execvpe_common (const char *file, char *const argv[], char *const envp[],
bool exec_script)
{
/* We check the simple case first. */
if (*file == '\0')
{
__set_errno (ENOENT);
return -1;
}
/* Don't search when it contains a slash. */
if (strchr (file, '/') != NULL)
{
__execve (file, argv, envp);
if (errno == ENOEXEC && exec_script)
maybe_script_execute (file, argv, envp);
return -1;
}
const char *path = getenv ("PATH");
if (!path)
path = CS_PATH;
/* Although GLIBC does not enforce NAME_MAX, we set it as the maximum
size to avoid unbounded stack allocation. Same applies for
PATH_MAX. */
size_t file_len = __strnlen (file, NAME_MAX) + 1;
size_t path_len = __strnlen (path, PATH_MAX - 1) + 1;
/* NAME_MAX does not include the terminating null character. */
if ((file_len - 1 > NAME_MAX)
|| !__libc_alloca_cutoff (path_len + file_len + 1))
{
errno = ENAMETOOLONG;
return -1;
}
const char *subp;
bool got_eacces = false;
/* The resulting string maximum size would be potentially a entry
in PATH plus '/' (path_len + 1) and then the the resulting file name
plus '\0' (file_len since it already accounts for the '\0'). */
char buffer[path_len + file_len + 1];
for (const char *p = path; ; p = subp)
{
subp = __strchrnul (p, ':');
/* PATH is larger than PATH_MAX and thus potentially larger than
the stack allocation. */
if (subp - p >= path_len)
{
/* If there is only one path, bail out. */
if (*subp == '\0')
break;
/* Otherwise skip to next one. */
continue;
}
/* Use the current path entry, plus a '/' if nonempty, plus the file to
execute. */
char *pend = mempcpy (buffer, p, subp - p);
*pend = '/';
memcpy (pend + (p < subp), file, file_len);
__execve (buffer, argv, envp);
if (errno == ENOEXEC && exec_script)
/* This has O(P*C) behavior, where P is the length of the path and C
is the argument count. A better strategy would be allocate the
substitute argv and reuse it each time through the loop (so it
behaves as O(P+C) instead. */
maybe_script_execute (buffer, argv, envp);
switch (errno)
{
case EACCES:
/* Record that we got a 'Permission denied' error. If we end
up finding no executable we can use, we want to diagnose
that we did find one but were denied access. */
got_eacces = true;
case ENOENT:
case ESTALE:
case ENOTDIR:
/* Those errors indicate the file is missing or not executable
by us, in which case we want to just try the next path
directory. */
case ENODEV:
case ETIMEDOUT:
/* Some strange filesystems like AFS return even
stranger error numbers. They cannot reasonably mean
anything else so ignore those, too. */
break;
default:
/* Some other error means we found an executable file, but
something went wrong executing it; return the error to our
caller. */
return -1;
}
if (*subp++ == '\0')
break;
}
/* We tried every element and none of them worked. */
if (got_eacces)
/* At least one failure was due to permissions, so report that
error. */
__set_errno (EACCES);
return -1;
}
/* Execute FILE, searching in the `PATH' environment variable if it contains
no slashes, with arguments ARGV and environment from ENVP. */
int
__execvpe (const char *file, char *const argv[], char *const envp[])
{
return __execvpe_common (file, argv, envp, true);
}
weak_alias (__execvpe, execvpe)
/* Same as __EXECVPE, but does not try to execute NOEXEC files. */
int
__execvpex (const char *file, char *const argv[], char *const envp[])
{
return __execvpe_common (file, argv, envp, false);
}
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