shadow/libmisc/shell.c

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/*
* Copyright (c) 1989 - 1991, Julianne Frances Haugh
* Copyright (c) 1996 - 1998, Marek Michałkiewicz
* Copyright (c) 2003 - 2006, Tomasz Kłoczko
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the copyright holders or contributors may not be used to
* endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <config.h>
#ident "$Id$"
#include <stdio.h>
#include <errno.h>
#include "prototypes.h"
#include "defines.h"
extern char **newenvp;
extern size_t newenvc;
/*
* shell - execute the named program
*
* shell begins by trying to figure out what argv[0] is going to
* be for the named process. The user may pass in that argument,
* or it will be the last pathname component of the file with a
* '-' prepended. The first attempt is to just execute the named
* file. If the errno comes back "ENOEXEC", the file is assumed
* at first glance to be a shell script. The first two characters
* must be "#!", in which case "/bin/sh" is executed to process
* the file. If all that fails, give up in disgust ...
*/
int shell (const char *file, const char *arg, char *const envp[])
{
char arg0[1024];
int err;
if (file == (char *) 0) {
errno = EINVAL;
return errno;
}
/*
* The argv[0]'th entry is usually the path name, but
* for various reasons the invoker may want to override
* that. So, we determine the 0'th entry only if they
* don't want to tell us what it is themselves.
*/
if (arg == (char *) 0) {
snprintf (arg0, sizeof arg0, "-%s", Basename ((char *) file));
arg = arg0;
}
/*
* First we try the direct approach. The system should be
* able to figure out what we are up to without too much
* grief.
*/
execle (file, arg, (char *) 0, envp);
err = errno;
/* Linux handles #! in the kernel, and bash doesn't make
sense of "#!" so it wouldn't work anyway... --marekm */
#ifndef __linux__
/*
* It is perfectly OK to have a shell script for a login
* shell, and this code attempts to support that. It
* relies on the standard shell being able to make sense
* of the "#!" magic number.
*/
if (err == ENOEXEC) {
FILE *fp;
if ((fp = fopen (file, "r"))) {
if (getc (fp) == '#' && getc (fp) == '!') {
fclose (fp);
execle ("/bin/sh", "sh",
file, (char *) 0, envp);
err = errno;
} else {
fclose (fp);
}
}
}
#endif
/*
* Obviously something is really wrong - I can't figure out
* how to execute this stupid shell, so I might as well give
* up in disgust ...
*/
snprintf (arg0, sizeof arg0, _("Cannot execute %s"), file);
errno = err;
perror (arg0);
return err;
}