exec_script.c revision 1.63.8.3
1 /* $NetBSD: exec_script.c,v 1.63.8.3 2011/03/05 20:55:12 rmind Exp $ */ 2 3 /* 4 * Copyright (c) 1993, 1994, 1996 Christopher G. Demetriou 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by Christopher G. Demetriou. 18 * 4. The name of the author may not be used to endorse or promote products 19 * derived from this software without specific prior written permission 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 #include <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: exec_script.c,v 1.63.8.3 2011/03/05 20:55:12 rmind Exp $"); 35 36 #if defined(SETUIDSCRIPTS) && !defined(FDSCRIPTS) 37 #define FDSCRIPTS /* Need this for safe set-id scripts. */ 38 #endif 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/proc.h> 43 #include <sys/kmem.h> 44 #include <sys/vnode.h> 45 #include <sys/namei.h> 46 #include <sys/file.h> 47 #ifdef SETUIDSCRIPTS 48 #include <sys/stat.h> 49 #endif 50 #include <sys/filedesc.h> 51 #include <sys/exec.h> 52 #include <sys/resourcevar.h> 53 #include <sys/module.h> 54 #include <sys/exec_script.h> 55 #include <sys/exec_elf.h> 56 57 MODULE(MODULE_CLASS_MISC, exec_script, NULL); 58 59 static struct execsw exec_script_execsw[] = { 60 { SCRIPT_HDR_SIZE, 61 exec_script_makecmds, 62 { NULL }, 63 NULL, 64 EXECSW_PRIO_ANY, 65 0, 66 NULL, 67 NULL, 68 NULL, 69 exec_setup_stack }, 70 }; 71 72 static int 73 exec_script_modcmd(modcmd_t cmd, void *arg) 74 { 75 76 switch (cmd) { 77 case MODULE_CMD_INIT: 78 return exec_add(exec_script_execsw, 79 __arraycount(exec_script_execsw)); 80 81 case MODULE_CMD_FINI: 82 return exec_remove(exec_script_execsw, 83 __arraycount(exec_script_execsw)); 84 85 case MODULE_CMD_AUTOUNLOAD: 86 /* 87 * We don't want to be autounloaded because our use is 88 * transient: no executables with p_execsw equal to 89 * exec_script_execsw will exist, so FINI will never 90 * return EBUSY. However, the system will run scripts 91 * often. Return EBUSY here to prevent this module from 92 * ping-ponging in and out of the kernel. 93 */ 94 return EBUSY; 95 96 default: 97 return ENOTTY; 98 } 99 } 100 101 /* 102 * exec_script_makecmds(): Check if it's an executable shell script. 103 * 104 * Given a proc pointer and an exec package pointer, see if the referent 105 * of the epp is in shell script. If it is, then set thing up so that 106 * the script can be run. This involves preparing the address space 107 * and arguments for the shell which will run the script. 108 * 109 * This function is ultimately responsible for creating a set of vmcmds 110 * which can be used to build the process's vm space and inserting them 111 * into the exec package. 112 */ 113 int 114 exec_script_makecmds(struct lwp *l, struct exec_package *epp) 115 { 116 int error, hdrlinelen, shellnamelen, shellarglen; 117 char *hdrstr = epp->ep_hdr; 118 char *cp, *shellname, *shellarg; 119 size_t shellargp_len; 120 struct exec_fakearg *shellargp; 121 struct exec_fakearg *tmpsap; 122 struct pathbuf *shell_pathbuf; 123 struct vnode *scriptvp; 124 #ifdef SETUIDSCRIPTS 125 /* Gcc needs those initialized for spurious uninitialized warning */ 126 uid_t script_uid = (uid_t) -1; 127 gid_t script_gid = NOGROUP; 128 u_short script_sbits; 129 #endif 130 131 /* 132 * if the magic isn't that of a shell script, or we've already 133 * done shell script processing for this exec, punt on it. 134 */ 135 if ((epp->ep_flags & EXEC_INDIR) != 0 || 136 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 137 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 138 return ENOEXEC; 139 140 /* 141 * check that the shell spec is terminated by a newline, 142 * and that it isn't too large. Don't modify the 143 * buffer unless we're ready to commit to handling it. 144 * (The latter requirement means that we have to check 145 * for both spaces and tabs later on.) 146 */ 147 hdrlinelen = min(epp->ep_hdrvalid, SCRIPT_HDR_SIZE); 148 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 149 cp++) { 150 if (*cp == '\n') { 151 *cp = '\0'; 152 break; 153 } 154 } 155 if (cp >= hdrstr + hdrlinelen) 156 return ENOEXEC; 157 158 /* 159 * If the script has an ELF header, don't exec it. 160 */ 161 if (epp->ep_hdrvalid >= sizeof(ELFMAG)-1 && 162 memcmp(hdrstr, ELFMAG, sizeof(ELFMAG)-1) == 0) 163 return ENOEXEC; 164 165 shellname = NULL; 166 shellarg = NULL; 167 shellarglen = 0; 168 169 /* strip spaces before the shell name */ 170 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 171 cp++) 172 ; 173 174 /* collect the shell name; remember it's length for later */ 175 shellname = cp; 176 shellnamelen = 0; 177 if (*cp == '\0') 178 goto check_shell; 179 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 180 shellnamelen++; 181 if (*cp == '\0') 182 goto check_shell; 183 *cp++ = '\0'; 184 185 /* skip spaces before any argument */ 186 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 187 ; 188 if (*cp == '\0') 189 goto check_shell; 190 191 /* 192 * collect the shell argument. everything after the shell name 193 * is passed as ONE argument; that's the correct (historical) 194 * behaviour. 195 */ 196 shellarg = cp; 197 for ( /* cp = cp */ ; *cp != '\0'; cp++) 198 shellarglen++; 199 *cp++ = '\0'; 200 201 check_shell: 202 #ifdef SETUIDSCRIPTS 203 /* 204 * MNT_NOSUID has already taken care of by check_exec, 205 * so we don't need to worry about it now or later. We 206 * will need to check PSL_TRACED later, however. 207 */ 208 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 209 if (script_sbits != 0) { 210 script_uid = epp->ep_vap->va_uid; 211 script_gid = epp->ep_vap->va_gid; 212 } 213 #endif 214 #ifdef FDSCRIPTS 215 /* 216 * if the script isn't readable, or it's set-id, then we've 217 * gotta supply a "/dev/fd/..." for the shell to read. 218 * Note that stupid shells (csh) do the wrong thing, and 219 * close all open fd's when the start. That kills this 220 * method of implementing "safe" set-id and x-only scripts. 221 */ 222 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 223 error = VOP_ACCESS(epp->ep_vp, VREAD, l->l_cred); 224 VOP_UNLOCK(epp->ep_vp); 225 if (error == EACCES 226 #ifdef SETUIDSCRIPTS 227 || script_sbits 228 #endif 229 ) { 230 struct file *fp; 231 232 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 233 if (epp->ep_flags & EXEC_HASFD) 234 panic("exec_script_makecmds: epp already has a fd"); 235 #endif 236 237 if ((error = fd_allocfile(&fp, &epp->ep_fd)) != 0) { 238 scriptvp = NULL; 239 shellargp = NULL; 240 goto fail; 241 } 242 epp->ep_flags |= EXEC_HASFD; 243 fp->f_type = DTYPE_VNODE; 244 fp->f_ops = &vnops; 245 fp->f_data = (void *) epp->ep_vp; 246 fp->f_flag = FREAD; 247 fd_affix(curproc, fp, epp->ep_fd); 248 } 249 #endif 250 251 /* set up the fake args list */ 252 shellargp_len = 4 * sizeof(*shellargp); 253 shellargp = kmem_alloc(shellargp_len, KM_SLEEP); 254 tmpsap = shellargp; 255 tmpsap->fa_len = shellnamelen + 1; 256 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 257 strlcpy(tmpsap->fa_arg, shellname, tmpsap->fa_len); 258 tmpsap++; 259 if (shellarg != NULL) { 260 tmpsap->fa_len = shellarglen + 1; 261 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 262 strlcpy(tmpsap->fa_arg, shellarg, tmpsap->fa_len); 263 tmpsap++; 264 } 265 tmpsap->fa_len = MAXPATHLEN; 266 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 267 #ifdef FDSCRIPTS 268 if ((epp->ep_flags & EXEC_HASFD) == 0) { 269 #endif 270 /* normally can't fail, but check for it if diagnostic */ 271 error = copystr(epp->ep_kname, tmpsap->fa_arg, MAXPATHLEN, 272 (size_t *)0); 273 tmpsap++; 274 #ifdef DIAGNOSTIC 275 if (error != 0) 276 panic("exec_script: copystr couldn't fail"); 277 #endif 278 #ifdef FDSCRIPTS 279 } else { 280 snprintf(tmpsap->fa_arg, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 281 tmpsap++; 282 } 283 #endif 284 tmpsap->fa_arg = NULL; 285 286 /* Save the old vnode so we can clean it up later. */ 287 scriptvp = epp->ep_vp; 288 epp->ep_vp = NULL; 289 290 /* Note that we're trying recursively. */ 291 epp->ep_flags |= EXEC_INDIR; 292 293 /* 294 * mark the header we have as invalid; check_exec will read 295 * the header from the new executable 296 */ 297 epp->ep_hdrvalid = 0; 298 299 /* try loading the interpreter */ 300 shell_pathbuf = pathbuf_create(shellname); 301 if (shell_pathbuf == NULL) { 302 error = ENOMEM; 303 } else { 304 error = check_exec(l, epp, shell_pathbuf); 305 pathbuf_destroy(shell_pathbuf); 306 } 307 308 /* note that we've clobbered the header */ 309 epp->ep_flags |= EXEC_DESTR; 310 311 if (error == 0) { 312 /* 313 * It succeeded. Unlock the script and 314 * close it if we aren't using it any more. 315 * Also, set things up so that the fake args 316 * list will be used. 317 */ 318 if ((epp->ep_flags & EXEC_HASFD) == 0) { 319 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 320 VOP_CLOSE(scriptvp, FREAD, l->l_cred); 321 vput(scriptvp); 322 } 323 324 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 325 epp->ep_fa = shellargp; 326 epp->ep_fa_len = shellargp_len; 327 #ifdef SETUIDSCRIPTS 328 /* 329 * set thing up so that set-id scripts will be 330 * handled appropriately. PSL_TRACED will be 331 * checked later when the shell is actually 332 * exec'd. 333 */ 334 epp->ep_vap->va_mode |= script_sbits; 335 if (script_sbits & S_ISUID) 336 epp->ep_vap->va_uid = script_uid; 337 if (script_sbits & S_ISGID) 338 epp->ep_vap->va_gid = script_gid; 339 #endif 340 return (0); 341 } 342 343 #ifdef FDSCRIPTS 344 fail: 345 #endif 346 347 /* kill the opened file descriptor, else close the file */ 348 if (epp->ep_flags & EXEC_HASFD) { 349 epp->ep_flags &= ~EXEC_HASFD; 350 fd_close(epp->ep_fd); 351 } else if (scriptvp) { 352 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 353 VOP_CLOSE(scriptvp, FREAD, l->l_cred); 354 vput(scriptvp); 355 } 356 357 /* free the fake arg list, because we're not returning it */ 358 if ((tmpsap = shellargp) != NULL) { 359 while (tmpsap->fa_arg != NULL) { 360 kmem_free(tmpsap->fa_arg, tmpsap->fa_len); 361 tmpsap++; 362 } 363 kmem_free(shellargp, shellargp_len); 364 } 365 366 /* 367 * free any vmspace-creation commands, 368 * and release their references 369 */ 370 kill_vmcmds(&epp->ep_vmcmds); 371 372 return error; 373 } 374
Indexes created Fri Oct 03 14:09:59 GMT 2025