imgact_shell.c revision 141028 
1104349Sphk/*-
2104349Sphk * Copyright (c) 1993, David Greenman
3104349Sphk * All rights reserved.
4104349Sphk *
5104349Sphk * Redistribution and use in source and binary forms, with or without
6104349Sphk * 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 141028 2005-01-30 06:43:17Z 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		while ((*ihp == ' ') || (*ihp == '\t')) {
79			ihp++;
80			continue;
81		}
82
83		/* End of line? */
84		if ((*ihp == '\n') || (*ihp == '#'))
85			break;
86
87		/* Found a token */
88		while ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') &&
89		    (*ihp != '#')) {
90			offset++;
91			ihp++;
92		}
93		/* Include terminating nulls in the offset */
94		offset++;
95	}
96
97	/* If the script gives a null line as the interpreter, we bail */
98	if (offset == 0)
99		return (ENOEXEC);
100
101	/* Check that we aren't too big */
102	if (offset > MAXSHELLCMDLEN)
103		return (ENAMETOOLONG);
104
105	/*
106	 * The full path name of the original script file must be tagged
107	 * onto the end, adjust the offset to deal with it.
108	 *
109	 * The original argv[0] is being replaced, set 'length' to the number
110	 * of bytes being removed.  So 'offset' is the number of bytes being
111	 * added and 'length' is the number of bytes being removed.
112	 */
113	offset += strlen(imgp->args->fname) + 1;	/* add fname */
114	length = (imgp->args->argc == 0) ? 0 :
115	    strlen(imgp->args->begin_argv) + 1;		/* bytes to delete */
116
117	if (offset - length > imgp->args->stringspace)
118		return (E2BIG);
119
120	bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
121	    imgp->args->endp - (imgp->args->begin_argv + length));
122
123	offset -= length;		/* calculate actual adjustment */
124	imgp->args->begin_envv += offset;
125	imgp->args->endp += offset;
126	imgp->args->stringspace -= offset;
127
128	/*
129	 * If there were no arguments then we've added one, otherwise
130	 * decr argc remove old argv[0], incr argc for fname add, net 0
131	 */
132	if (imgp->args->argc == 0)
133		imgp->args->argc = 1;
134
135	/*
136	 * Loop through the interpreter name yet again, copying as
137	 * we go.
138	 */
139	ihp = &image_header[2];
140	offset = 0;
141	while (ihp < &image_header[MAXSHELLCMDLEN]) {
142		/* Skip whitespace */
143		while ((*ihp == ' ' || *ihp == '\t')) {
144			ihp++;
145			continue;
146		}
147
148		/* End of line? */
149		if ((*ihp == '\n') || (*ihp == '#'))
150			break;
151
152		/* Found a token, copy it */
153		while ((*ihp != ' ') && (*ihp != '\t') &&
154		    (*ihp != '\n') && (*ihp != '#')) {
155			imgp->args->begin_argv[offset++] = *ihp++;
156		}
157		imgp->args->begin_argv[offset++] = '\0';
158		imgp->args->argc++;
159	}
160
161	/*
162	 * Finally, add the filename onto the end for the interpreter to
163	 * use and copy the interpreter's name to imgp->interpreter_name
164	 * for exec to use.
165	 */
166	error = copystr(imgp->args->fname, imgp->args->buf + offset,
167	    imgp->args->stringspace, &length);
168
169	if (error == 0)
170		error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
171		    MAXSHELLCMDLEN, &length);
172
173	return (error);
174}
175
176/*
177 * Tell kern_execve.c about it, with a little help from the linker.
178 */
179static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
180EXEC_SET(shell, shell_execsw);
181