xref: /freebsd/sys/kern/imgact_shell.c (revision 41466b50c1d5bfd1cf6adaae547a579a75d7c04e)
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  * $FreeBSD$
27  */
28 
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/sysproto.h>
32 #include <sys/exec.h>
33 #include <sys/imgact.h>
34 #include <sys/kernel.h>
35 
36 #if BYTE_ORDER == LITTLE_ENDIAN
37 #define SHELLMAGIC	0x2123 /* #! */
38 #else
39 #define SHELLMAGIC	0x2321
40 #endif
41 
42 /*
43  * Shell interpreter image activator. A interpreter name beginning
44  *	at imgp->stringbase is the minimal successful exit requirement.
45  */
46 int
47 exec_shell_imgact(imgp)
48 	struct image_params *imgp;
49 {
50 	const char *image_header = imgp->image_header;
51 	const char *ihp, *line_endp;
52 	char *interp;
53 
54 	/* a shell script? */
55 	if (((const short *) image_header)[0] != SHELLMAGIC)
56 		return(-1);
57 
58 	/*
59 	 * Don't allow a shell script to be the shell for a shell
60 	 *	script. :-)
61 	 */
62 	if (imgp->interpreted)
63 		return(ENOEXEC);
64 
65 	imgp->interpreted = 1;
66 
67 	/*
68 	 * Copy shell name and arguments from image_header into string
69 	 *	buffer.
70 	 */
71 
72 	/*
73 	 * Find end of line; return if the line > MAXSHELLCMDLEN long.
74 	 */
75 	for (ihp = &image_header[2]; *ihp != '\n' && *ihp != '#'; ++ihp) {
76 		if (ihp >= &image_header[MAXSHELLCMDLEN])
77 			return(ENOEXEC);
78 	}
79 	line_endp = ihp;
80 
81 	/* reset for another pass */
82 	ihp = &image_header[2];
83 
84 	/* Skip over leading spaces - until the interpreter name */
85 	while ((*ihp == ' ') || (*ihp == '\t')) ihp++;
86 
87 	/* copy the interpreter name */
88 	interp = imgp->interpreter_name;
89 	while ((ihp < line_endp) && (*ihp != ' ') && (*ihp != '\t'))
90 		*interp++ = *ihp++;
91 	*interp = '\0';
92 
93 	/* Disallow a null interpreter filename */
94 	if (*imgp->interpreter_name == '\0')
95 		return(ENOEXEC);
96 
97 	/* reset for another pass */
98 	ihp = &image_header[2];
99 
100 	/* copy the interpreter name and arguments */
101 	while (ihp < line_endp) {
102 		/* Skip over leading spaces */
103 		while ((*ihp == ' ') || (*ihp == '\t')) ihp++;
104 
105 		if (ihp < line_endp) {
106 			/*
107 			 * Copy to end of token. No need to watch stringspace
108 			 *	because this is at the front of the string buffer
109 			 *	and the maximum shell command length is tiny.
110 			 */
111 			while ((ihp < line_endp) && (*ihp != ' ') && (*ihp != '\t')) {
112 				*imgp->stringp++ = *ihp++;
113 				imgp->stringspace--;
114 			}
115 
116 			*imgp->stringp++ = 0;
117 			imgp->stringspace--;
118 
119 			imgp->argc++;
120 		}
121 	}
122 
123 	imgp->argv0 = imgp->uap->fname;
124 
125 	return(0);
126 }
127 
128 /*
129  * Tell kern_execve.c about it, with a little help from the linker.
130  */
131 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
132 EXEC_SET(shell, shell_execsw);
133