1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2010 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #include <sys/types.h>
28 #include <sys/param.h>
29 #include <sys/sysmacros.h>
30 #include <sys/signal.h>
31 #include <sys/cred.h>
32 #include <sys/user.h>
33 #include <sys/errno.h>
34 #include <sys/vnode.h>
35 #include <sys/proc.h>
36 #include <sys/cmn_err.h>
37 #include <sys/debug.h>
38 #include <sys/pathname.h>
39 #include <sys/disp.h>
40 #include <sys/exec.h>
41 #include <sys/kmem.h>
42 #include <sys/note.h>
43
44 /*
45 * This is the loadable module wrapper.
46 */
47 #include <sys/modctl.h>
48
49 /* Local prototypes */
50 static int
51 shbinexec(
52 struct vnode *vp,
53 struct execa *uap,
54 struct uarg *args,
55 struct intpdata *idatap,
56 int level,
57 long *execsz,
58 int setid,
59 caddr_t exec_file,
60 struct cred *cred,
61 int brand_action);
62
63 #define SHBIN_CNTL(x) ((x)&037)
64 #define SHBINMAGIC_LEN 4
65 extern char shbinmagicstr[];
66
67 /*
68 * Our list where we may find a copy of ksh93. The ordering is:
69 * 1. 64bit (may not be installed or not supported in hardware)
70 * 2. 32bit
71 * 3. Use /sbin/ksh93 when /usr is not available
72 *
73 * ([1] and [2] explicitly bypass /usr/bin/ksh93 to avoid the
74 * isaexec overhead).
75 */
76 static char *shell_list[] =
77 {
78 /* Bypass /usr/bin/ksh93 (which is "isaexec") for performance */
79 #if defined(__sparc)
80 "/usr/bin/sparcv9/ksh93",
81 "/usr/bin/sparcv7/ksh93",
82 #elif defined(__amd64)
83 "/usr/bin/amd64/ksh93",
84 "/usr/bin/i86/ksh93",
85 #elif defined(__i386)
86 "/usr/bin/i86/ksh93",
87 #else
88 #error "Unrecognized platform/CPU (use /usr/bin/ksh93 when in doubt)."
89 #endif
90 "/sbin/ksh93",
91 NULL
92 };
93
94 static struct execsw esw = {
95 shbinmagicstr,
96 0,
97 SHBINMAGIC_LEN,
98 shbinexec,
99 NULL
100 };
101
102 /*
103 * Module linkage information for the kernel.
104 */
105 extern struct mod_ops mod_execops;
106
107 static struct modlexec modlexec = {
108 &mod_execops, "exec mod for shell binaries (ksh93)", &esw
109 };
110
111 static struct modlinkage modlinkage = {
112 MODREV_1, { (void *)&modlexec, NULL }
113 };
114
115 int
116 _init(void)
117 {
118 return (mod_install(&modlinkage));
119 }
120
121 int
122 _fini(void)
123 {
124 return (mod_remove(&modlinkage));
125 }
126
127 int
128 _info(struct modinfo *modinfop)
129 {
130 return (mod_info(&modlinkage, modinfop));
131 }
132
133 static int
134 checkshbinmagic(struct vnode *vp)
135 {
136 int error;
137 char linep[SHBINMAGIC_LEN];
138 ssize_t resid;
139
140 /*
141 * Read the entire line and confirm that it starts with the magic
142 * sequence for compiled ksh93 shell scripts.
143 */
144 if (error = vn_rdwr(UIO_READ, vp, linep, sizeof (linep), (offset_t)0,
145 UIO_SYSSPACE, 0, (rlim64_t)0, CRED(), &resid))
146 return (error);
147
148 if (memcmp(linep, shbinmagicstr, SHBINMAGIC_LEN) != 0)
149 return (ENOEXEC);
150
151 return (0);
152 }
153
154 static int
155 shbinexec(
156 struct vnode *vp,
157 struct execa *uap,
158 struct uarg *args,
159 struct intpdata *idatap,
160 int level,
161 long *execsz,
162 int setid,
163 caddr_t exec_file,
164 struct cred *cred,
165 int brand_action)
166 {
167 _NOTE(ARGUNUSED(brand_action))
168 vnode_t *nvp;
169 int error = 0;
170 struct intpdata idata;
171 struct pathname intppn;
172 struct pathname resolvepn;
173 char *opath;
174 char devfd[19]; /* 32-bit int fits in 10 digits + 8 for "/dev/fd/" */
175 int fd = -1;
176 int i;
177
178 if (level) { /* Can't recurse */
179 error = ENOEXEC;
180 goto bad;
181 }
182
183 ASSERT(idatap == (struct intpdata *)NULL);
184
185 /*
186 * Check whether the executable has the correct magic value.
187 */
188 if (error = checkshbinmagic(vp))
189 goto fail;
190
191 pn_alloc(&resolvepn);
192
193 /*
194 * Travel the list of shells and look for one which is available...
195 */
196 for (i = 0; shell_list[i] != NULL; i++) {
197 error = pn_get(shell_list[i], UIO_SYSSPACE, &intppn);
198 if (error != 0) {
199 break;
200 }
201
202 error = lookuppn(&intppn, &resolvepn, FOLLOW, NULLVPP, &nvp);
203 if (!error) {
204 /* Found match */
205 break;
206 }
207
208 /* No match found ? Then continue with the next item... */
209 pn_free(&intppn);
210 }
211
212 if (error) {
213 pn_free(&resolvepn);
214 goto fail;
215 }
216
217 /*
218 * Setup interpreter data
219 * "--" is passed to mark the end-of-arguments before adding
220 * the scripts file name, preventing problems when a
221 * a script's name starts with a '-' character.
222 */
223 idata.intp = NULL;
224 idata.intp_name[0] = shell_list[i];
225 idata.intp_arg[0] = "--";
226
227 opath = args->pathname;
228 args->pathname = resolvepn.pn_path;
229 /* don't free resolvepn until we are done with args */
230 pn_free(&intppn);
231
232 /*
233 * When we're executing a set-uid script resulting in uids
234 * mismatching or when we execute with additional privileges,
235 * we close the "replace script between exec and open by shell"
236 * hole by passing the script as /dev/fd parameter.
237 */
238 if ((setid & EXECSETID_PRIVS) != 0 ||
239 (setid & (EXECSETID_UGIDS|EXECSETID_SETID)) ==
240 (EXECSETID_UGIDS|EXECSETID_SETID)) {
241 (void) strcpy(devfd, "/dev/fd/");
242 if (error = execopen(&vp, &fd))
243 goto done;
244 numtos(fd, &devfd[8]);
245 args->fname = devfd;
246 }
247
248 error = gexec(&nvp, uap, args, &idata, ++level, execsz, exec_file, cred,
249 EBA_NONE);
250
251 if (!error) {
252 /*
253 * Close this script as the sh interpreter
254 * will open and close it later on.
255 */
256 (void) VOP_CLOSE(vp, FREAD, 1, (offset_t)0, cred, NULL);
257 }
258 done:
259 VN_RELE(nvp);
260 args->pathname = opath;
261 pn_free(&resolvepn);
262 fail:
263 if (error && fd != -1)
264 (void) execclose(fd);
265 bad:
266 return (error);
267 }