imgact_shell.c revision 142444 
1/*-
2 * Copyright (c) 1993, David Greenman
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/sys/kern/imgact_shell.c 142444 2005-02-25 08:42:04Z sobomax $");
29
30#include <sys/param.h>
31#include <sys/systm.h>
32#include <sys/sysproto.h>
33#include <sys/exec.h>
34#include <sys/imgact.h>
35#include <sys/kernel.h>
36
37#if BYTE_ORDER == LITTLE_ENDIAN
38#define SHELLMAGIC	0x2123 /* #! */
39#else
40#define SHELLMAGIC	0x2321
41#endif
42
43/*
44 * Shell interpreter image activator. An interpreter name beginning
45 *	at imgp->args->begin_argv is the minimal successful exit requirement.
46 */
47int
48exec_shell_imgact(imgp)
49	struct image_params *imgp;
50{
51	const char *image_header = imgp->image_header;
52	const char *ihp;
53	int error, offset;
54	size_t length;
55
56	/* a shell script? */
57	if (((const short *) image_header)[0] != SHELLMAGIC)
58		return(-1);
59
60	/*
61	 * Don't allow a shell script to be the shell for a shell
62	 *	script. :-)
63	 */
64	if (imgp->interpreted)
65		return(ENOEXEC);
66
67	imgp->interpreted = 1;
68
69	/*
70	 * Figure out the number of bytes that need to be reserved in the
71	 * argument string to copy the contents of the interpreter's command
72	 * line into the argument string.
73	 */
74	ihp = &image_header[2];
75	offset = 0;
76	while (ihp < &image_header[MAXSHELLCMDLEN]) {
77		/* Skip any whitespace */
78		if ((*ihp == ' ') || (*ihp == '\t')) {
79			ihp++;
80			continue;
81		}
82
83		/* End of line? */
84		if ((*ihp == '\n') || (*ihp == '#') || (*ihp == '\0'))
85			break;
86
87		/* Found a token */
88		while ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') &&
89		    (*ihp != '#') && (*ihp != '\0') &&
90		    (ihp < &image_header[MAXSHELLCMDLEN])) {
91			offset++;
92			ihp++;
93		}
94		/* Include terminating nulls in the offset */
95		offset++;
96	}
97
98	/* If the script gives a null line as the interpreter, we bail */
99	if (offset == 0)
100		return (ENOEXEC);
101
102	/* Check that we aren't too big */
103	if (offset > MAXSHELLCMDLEN)
104		return (ENAMETOOLONG);
105
106	/*
107	 * The full path name of the original script file must be tagged
108	 * onto the end, adjust the offset to deal with it.
109	 *
110	 * The original argv[0] is being replaced, set 'length' to the number
111	 * of bytes being removed.  So 'offset' is the number of bytes being
112	 * added and 'length' is the number of bytes being removed.
113	 */
114	offset += strlen(imgp->args->fname) + 1;	/* add fname */
115	length = (imgp->args->argc == 0) ? 0 :
116	    strlen(imgp->args->begin_argv) + 1;		/* bytes to delete */
117
118	if (offset - length > imgp->args->stringspace)
119		return (E2BIG);
120
121	bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
122	    imgp->args->endp - (imgp->args->begin_argv + length));
123
124	offset -= length;		/* calculate actual adjustment */
125	imgp->args->begin_envv += offset;
126	imgp->args->endp += offset;
127	imgp->args->stringspace -= offset;
128
129	/*
130	 * If there were no arguments then we've added one, otherwise
131	 * decr argc remove old argv[0], incr argc for fname add, net 0
132	 */
133	if (imgp->args->argc == 0)
134		imgp->args->argc = 1;
135
136	/*
137	 * Loop through the interpreter name yet again, copying as
138	 * we go.
139	 */
140	ihp = &image_header[2];
141	offset = 0;
142	while (ihp < &image_header[MAXSHELLCMDLEN]) {
143		/* Skip whitespace */
144		if ((*ihp == ' ') || (*ihp == '\t')) {
145			ihp++;
146			continue;
147		}
148
149		/* End of line? */
150		if ((*ihp == '\n') || (*ihp == '#') || (*ihp == '\0'))
151			break;
152
153		/* Found a token, copy it */
154		while ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') &&
155		    (*ihp != '#') && (*ihp != '\0') &&
156		    (ihp < &image_header[MAXSHELLCMDLEN])) {
157			imgp->args->begin_argv[offset++] = *ihp++;
158		}
159		imgp->args->begin_argv[offset++] = '\0';
160		imgp->args->argc++;
161	}
162
163	/*
164	 * Finally, add the filename onto the end for the interpreter to
165	 * use and copy the interpreter's name to imgp->interpreter_name
166	 * for exec to use.
167	 */
168	error = copystr(imgp->args->fname, imgp->args->buf + offset,
169	    imgp->args->stringspace, &length);
170
171	if (error == 0)
172		error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
173		    MAXSHELLCMDLEN, &length);
174
175	return (error);
176}
177
178/*
179 * Tell kern_execve.c about it, with a little help from the linker.
180 */
181static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
182EXEC_SET(shell, shell_execsw);
183