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/*
libfakechroot -- fake chroot environment
Copyright (c) 2010, 2013 Piotr Roszatycki <dexter@debian.org>
This 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.
This 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 this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <config.h>
#define _GNU_SOURCE
#include <errno.h>
#include <stddef.h>
#ifdef HAVE_ALLOCA_H
# include <alloca.h>
#endif
#include <stdlib.h>
#include <unistd.h>
#include "strchrnul.h"
#include "libfakechroot.h"
#ifndef __GLIBC__
extern char **environ;
#endif
#define DEFAULT_PATH ":/usr/bin:/bin"
/*
execvp function taken from GNU C Library.
Copyright (C) 1991,92, 1995-99, 2002, 2004, 2005, 2007, 2009
Free Software Foundation, Inc.
*/
wrapper(execvp, int, (const char * file, char * const argv[]))
{
debug("execvp(\"%s\", {\"%s\", ...})", file, argv[0]);
if (*file == '\0') {
/* We check the simple case first. */
__set_errno(ENOENT);
return -1;
}
if (strchr(file, '/') != NULL) {
/* Don't search when it contains a slash. */
return execve(file, argv, environ);
} else {
int got_eacces = 0;
char *path, *p, *name;
size_t len;
size_t pathlen;
path = getenv("PATH");
if (path == NULL) {
/* There is no `PATH' in the environment.
The default search path is the current directory
followed by the path `confstr' returns for `_CS_PATH'. */
#ifdef _CS_PATH
len = confstr(_CS_PATH, (char *) NULL, 0);
path = (char *) alloca(1 + len);
path[0] = ':';
(void) confstr(_CS_PATH, path + 1, len);
#else
path = (char *) alloca(sizeof(DEFAULT_PATH));
strcpy(path, DEFAULT_PATH);
#endif
}
len = strlen(file) + 1;
pathlen = strlen(path);
name = alloca(pathlen + len + 1);
/* Copy the file name at the top. */
name = (char *) memcpy(name + pathlen + 1, file, len);
/* And add the slash. */
*--name = '/';
p = path;
do {
char *startp;
path = p;
p = strchrnul(path, ':');
if (p == path)
/* Two adjacent colons, or a colon at the beginning or the end
of `PATH' means to search the current directory. */
startp = name + 1;
else
startp = (char *) memcpy(name - (p - path), path, p - path);
/* Try to execute this name. If it works, execv will not return. */
execve(startp, argv, environ);
switch (errno) {
case EACCES:
/* Record the 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 = 1;
break;
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. */
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;
}
} while (*p++ != '\0');
/* 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 the error from the last attempt (probably ENOENT). */
return -1;
}
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