/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 1993, David Greenman
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/vnode.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/exec.h>
#include <sys/imgact.h>
#include <sys/kernel.h>
#if BYTE_ORDER == LITTLE_ENDIAN
#define SHELLMAGIC 0x2123 /* #! */
#else
#define SHELLMAGIC 0x2321
#endif
/*
* At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is
* significant because the caller has only mapped in one page of the
* file we're reading.
*/
#if MAXSHELLCMDLEN > PAGE_SIZE
#error "MAXSHELLCMDLEN is larger than a single page!"
#endif
/*
* MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!'
* prefix and terminating newline.
*/
CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3);
/**
* Shell interpreter image activator. An interpreter name beginning at
* imgp->args->begin_argv is the minimal successful exit requirement.
*
* If the given file is a shell-script, then the first line will start
* with the two characters `#!' (aka SHELLMAGIC), followed by the name
* of the shell-interpreter to run, followed by zero or more tokens.
*
* The interpreter is then started up such that it will see:
* arg[0] -> The name of interpreter as specified after `#!' in the
* first line of the script. The interpreter name must
* not be longer than MAXSHELLCMDLEN bytes.
* arg[1] -> *If* there are any additional tokens on the first line,
* then we add a new arg[1], which is a copy of the rest of
* that line. The copy starts at the first token after the
* interpreter name. We leave it to the interpreter to
* parse the tokens in that value.
* arg[x] -> the full pathname of the script. This will either be
* arg[2] or arg[1], depending on whether or not tokens
* were found after the interpreter name.
* arg[x+1] -> all the arguments that were specified on the original
* command line.
*
* This processing is described in the execve(2) man page.
*/
/*
* HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
* found on the first line of the script, and setup each token as a separate
* value in arg[]. This extra processing did not match the behavior of other
* OS's, and caused a few subtle problems. For one, it meant the kernel was
* deciding how those values should be parsed (wrt characters for quoting or
* comments, etc), while the interpreter might have other rules for parsing.
* It also meant the interpreter had no way of knowing which arguments came
* from the first line of the shell script, and which arguments were specified
* by the user on the command line. That extra processing was dropped in the
* 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029).
*/
int
exec_shell_imgact(struct image_params *imgp)
{
const char *image_header = imgp->image_header;
const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname;
int error, offset;
size_t length;
struct vattr vattr;
struct sbuf *sname;
/* a shell script? */
if (((const short *)image_header)[0] != SHELLMAGIC)
return (-1);
/*
* Don't allow a shell script to be the shell for a shell
* script. :-)
*/
if (imgp->interpreted & IMGACT_SHELL)
return (ENOEXEC);
imgp->interpreted |= IMGACT_SHELL;
/*
* At this point we have the first page of the file mapped.
* However, we don't know how far into the page the contents are
* valid -- the actual file might be much shorter than the page.
* So find out the file size.
*/
error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred);
if (error)
return (error);
/*
* Copy shell name and arguments from image_header into a string
* buffer.
*/
maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)];
ihp = &image_header[2];
/*
* Find the beginning and end of the interpreter_name. If the
* line does not include any interpreter, or if the name which
* was found is too long, we bail out.
*/
while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
ihp++;
interpb = ihp;
while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
&& (*ihp != '\0')))
ihp++;
interpe = ihp;
if (interpb == interpe)
return (ENOEXEC);
if (interpe - interpb >= MAXINTERP)
return (ENAMETOOLONG);
/*
* Find the beginning of the options (if any), and the end-of-line.
* Then trim the trailing blanks off the value. Note that some
* other operating systems do *not* trim the trailing whitespace...
*/
while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
ihp++;
optb = ihp;
while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
ihp++;
opte = ihp;
if (opte == maxp)
return (ENOEXEC);
while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t')))
opte = ihp;
if (imgp->args->fname != NULL) {
fname = imgp->args->fname;
sname = NULL;
} else {
sname = sbuf_new_auto();
sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd);
sbuf_finish(sname);
fname = sbuf_data(sname);
}
/*
* We need to "pop" (remove) the present value of arg[0], and "push"
* either two or three new values in the arg[] list. To do this,
* we first shift all the other values in the `begin_argv' area to
* provide the exact amount of room for the values added. Set up
* `offset' as the number of bytes to be added to the `begin_argv'
* area, and 'length' as the number of bytes being removed.
*/
offset = interpe - interpb + 1; /* interpreter */
if (opte > optb) /* options (if any) */
offset += opte - optb + 1;
offset += strlen(fname) + 1; /* fname of script */
length = (imgp->args->argc == 0) ? 0 :
strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
error = exec_args_adjust_args(imgp->args, length, offset);
if (error != 0) {
if (sname != NULL)
sbuf_delete(sname);
return (error);
}
/*
* If there was no arg[0] when we started, then the interpreter_name
* is adding an argument (instead of replacing the arg[0] we started
* with). And we're always adding an argument when we include the
* full pathname of the original script.
*/
if (imgp->args->argc == 0)
imgp->args->argc = 1;
imgp->args->argc++;
/*
* The original arg[] list has been shifted appropriately. Copy in
* the interpreter name and options-string.
*/
length = interpe - interpb;
bcopy(interpb, imgp->args->begin_argv, length);
*(imgp->args->begin_argv + length) = '\0';
offset = length + 1;
if (opte > optb) {
length = opte - optb;
bcopy(optb, imgp->args->begin_argv + offset, length);
*(imgp->args->begin_argv + offset + length) = '\0';
offset += length + 1;
imgp->args->argc++;
}
/*
* Finally, add the filename onto the end for the interpreter to
* use and copy the interpreter's name to imgp->interpreter_name
* for exec to use.
*/
error = copystr(fname, imgp->args->begin_argv + offset,
imgp->args->stringspace, NULL);
if (error == 0)
imgp->interpreter_name = imgp->args->begin_argv;
if (sname != NULL)
sbuf_delete(sname);
return (error);
}
/*
* Tell kern_execve.c about it, with a little help from the linker.
*/
static struct execsw shell_execsw = {
.ex_imgact = exec_shell_imgact,
.ex_name = "#!"
};
EXEC_SET(shell, shell_execsw);
