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: releng/10.1/sys/kern/imgact_shell.c 272450 2014-10-02 21:19:13Z sbruno $");
29
30 #include <sys/param.h>
31 #include <sys/vnode.h>
32 #include <sys/proc.h>
33 #include <sys/sbuf.h>
34 #include <sys/systm.h>
35 #include <sys/sysproto.h>
36 #include <sys/exec.h>
37 #include <sys/imgact.h>
38 #include <sys/kernel.h>
39
40 #if BYTE_ORDER == LITTLE_ENDIAN
41 #define SHELLMAGIC 0x2123 /* #! */
42 #else
43 #define SHELLMAGIC 0x2321
44 #endif
45
46 /*
47 * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is
48 * significant because the caller has only mapped in one page of the
49 * file we're reading.
50 */
51 #if MAXSHELLCMDLEN > PAGE_SIZE
52 #error "MAXSHELLCMDLEN is larger than a single page!"
53 #endif
54
55 /*
56 * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!'
57 * prefix and terminating newline.
58 */
59 CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3);
60
61 /**
62 * Shell interpreter image activator. An interpreter name beginning at
63 * imgp->args->begin_argv is the minimal successful exit requirement.
64 *
65 * If the given file is a shell-script, then the first line will start
66 * with the two characters `#!' (aka SHELLMAGIC), followed by the name
67 * of the shell-interpreter to run, followed by zero or more tokens.
68 *
69 * The interpreter is then started up such that it will see:
70 * arg[0] -> The name of interpreter as specified after `#!' in the
71 * first line of the script. The interpreter name must
72 * not be longer than MAXSHELLCMDLEN bytes.
73 * arg[1] -> *If* there are any additional tokens on the first line,
74 * then we add a new arg[1], which is a copy of the rest of
75 * that line. The copy starts at the first token after the
76 * interpreter name. We leave it to the interpreter to
77 * parse the tokens in that value.
78 * arg[x] -> the full pathname of the script. This will either be
79 * arg[2] or arg[1], depending on whether or not tokens
80 * were found after the interpreter name.
81 * arg[x+1] -> all the arguments that were specified on the original
82 * command line.
83 *
84 * This processing is described in the execve(2) man page.
85 */
86
87 /*
88 * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
89 * found on the first line of the script, and setup each token as a separate
90 * value in arg[]. This extra processing did not match the behavior of other
91 * OS's, and caused a few subtle problems. For one, it meant the kernel was
92 * deciding how those values should be parsed (wrt characters for quoting or
93 * comments, etc), while the interpreter might have other rules for parsing.
94 * It also meant the interpreter had no way of knowing which arguments came
95 * from the first line of the shell script, and which arguments were specified
96 * by the user on the command line. That extra processing was dropped in the
97 * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029).
98 */
99 int
100 exec_shell_imgact(imgp)
101 struct image_params *imgp;
102 {
103 const char *image_header = imgp->image_header;
104 const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname;
105 int error, offset;
106 size_t length;
107 struct vattr vattr;
108 struct sbuf *sname;
109
110 /* a shell script? */
111 if (((const short *)image_header)[0] != SHELLMAGIC)
112 return (-1);
113
114 /*
115 * Don't allow a shell script to be the shell for a shell
116 * script. :-)
117 */
118 if (imgp->interpreted & IMGACT_SHELL)
119 return (ENOEXEC);
120
121 imgp->interpreted |= IMGACT_SHELL;
122
123 /*
124 * At this point we have the first page of the file mapped.
125 * However, we don't know how far into the page the contents are
126 * valid -- the actual file might be much shorter than the page.
127 * So find out the file size.
128 */
129 error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred);
130 if (error)
131 return (error);
132
133 /*
134 * Copy shell name and arguments from image_header into a string
135 * buffer.
136 */
137 maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)];
138 ihp = &image_header[2];
139
140 /*
141 * Find the beginning and end of the interpreter_name. If the
142 * line does not include any interpreter, or if the name which
143 * was found is too long, we bail out.
144 */
145 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
146 ihp++;
147 interpb = ihp;
148 while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
149 && (*ihp != '\0')))
150 ihp++;
151 interpe = ihp;
152 if (interpb == interpe)
153 return (ENOEXEC);
154 if (interpe - interpb >= MAXINTERP)
155 return (ENAMETOOLONG);
156
157 /*
158 * Find the beginning of the options (if any), and the end-of-line.
159 * Then trim the trailing blanks off the value. Note that some
160 * other operating systems do *not* trim the trailing whitespace...
161 */
162 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
163 ihp++;
164 optb = ihp;
165 while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
166 ihp++;
167 opte = ihp;
168 if (opte == maxp)
169 return (ENOEXEC);
170 while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t')))
171 opte = ihp;
172
173 if (imgp->args->fname != NULL) {
174 fname = imgp->args->fname;
175 sname = NULL;
176 } else {
177 sname = sbuf_new_auto();
178 sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd);
179 sbuf_finish(sname);
180 fname = sbuf_data(sname);
181 }
182
183 /*
184 * We need to "pop" (remove) the present value of arg[0], and "push"
185 * either two or three new values in the arg[] list. To do this,
186 * we first shift all the other values in the `begin_argv' area to
187 * provide the exact amount of room for the values added. Set up
188 * `offset' as the number of bytes to be added to the `begin_argv'
189 * area, and 'length' as the number of bytes being removed.
190 */
191 offset = interpe - interpb + 1; /* interpreter */
192 if (opte > optb) /* options (if any) */
193 offset += opte - optb + 1;
194 offset += strlen(fname) + 1; /* fname of script */
195 length = (imgp->args->argc == 0) ? 0 :
196 strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
197
198 if (offset > imgp->args->stringspace + length) {
199 if (sname != NULL)
200 sbuf_delete(sname);
201 return (E2BIG);
202 }
203
204 bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
205 imgp->args->endp - (imgp->args->begin_argv + length));
206
207 offset -= length; /* calculate actual adjustment */
208 imgp->args->begin_envv += offset;
209 imgp->args->endp += offset;
210 imgp->args->stringspace -= offset;
211
212 /*
213 * If there was no arg[0] when we started, then the interpreter_name
214 * is adding an argument (instead of replacing the arg[0] we started
215 * with). And we're always adding an argument when we include the
216 * full pathname of the original script.
217 */
218 if (imgp->args->argc == 0)
219 imgp->args->argc = 1;
220 imgp->args->argc++;
221
222 /*
223 * The original arg[] list has been shifted appropriately. Copy in
224 * the interpreter name and options-string.
225 */
226 length = interpe - interpb;
227 bcopy(interpb, imgp->args->begin_argv, length);
228 *(imgp->args->begin_argv + length) = '\0';
229 offset = length + 1;
230 if (opte > optb) {
231 length = opte - optb;
232 bcopy(optb, imgp->args->begin_argv + offset, length);
233 *(imgp->args->begin_argv + offset + length) = '\0';
234 offset += length + 1;
235 imgp->args->argc++;
236 }
237
238 /*
239 * Finally, add the filename onto the end for the interpreter to
240 * use and copy the interpreter's name to imgp->interpreter_name
241 * for exec to use.
242 */
243 error = copystr(fname, imgp->args->begin_argv + offset,
244 imgp->args->stringspace, NULL);
245
246 if (error == 0)
247 imgp->interpreter_name = imgp->args->begin_argv;
248
249 if (sname != NULL)
250 sbuf_delete(sname);
251 return (error);
252 }
253
254 /*
255 * Tell kern_execve.c about it, with a little help from the linker.
256 */
257 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
258 EXEC_SET(shell, shell_execsw);
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