1 /* $NetBSD: exec_script.c,v 1.65 2010/06/24 13:03:11 hannken 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 1.65 2010/06/24 13:03:11 hannken 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 vnode *scriptvp; 123 #ifdef SETUIDSCRIPTS 124 /* Gcc needs those initialized for spurious uninitialized warning */ 125 uid_t script_uid = (uid_t) -1; 126 gid_t script_gid = NOGROUP; 127 u_short script_sbits; 128 #endif 129 130 /* 131 * if the magic isn't that of a shell script, or we've already 132 * done shell script processing for this exec, punt on it. 133 */ 134 if ((epp->ep_flags & EXEC_INDIR) != 0 || 135 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 136 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 137 return ENOEXEC; 138 139 /* 140 * check that the shell spec is terminated by a newline, 141 * and that it isn't too large. Don't modify the 142 * buffer unless we're ready to commit to handling it. 143 * (The latter requirement means that we have to check 144 * for both spaces and tabs later on.) 145 */ 146 hdrlinelen = min(epp->ep_hdrvalid, SCRIPT_HDR_SIZE); 147 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 148 cp++) { 149 if (*cp == '\n') { 150 *cp = '\0'; 151 break; 152 } 153 } 154 if (cp >= hdrstr + hdrlinelen) 155 return ENOEXEC; 156 157 /* 158 * If the script has an ELF header, don't exec it. 159 */ 160 if (epp->ep_hdrvalid >= sizeof(ELFMAG)-1 && 161 memcmp(hdrstr, ELFMAG, sizeof(ELFMAG)-1) == 0) 162 return ENOEXEC; 163 164 shellname = NULL; 165 shellarg = NULL; 166 shellarglen = 0; 167 168 /* strip spaces before the shell name */ 169 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 170 cp++) 171 ; 172 173 /* collect the shell name; remember it's length for later */ 174 shellname = cp; 175 shellnamelen = 0; 176 if (*cp == '\0') 177 goto check_shell; 178 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 179 shellnamelen++; 180 if (*cp == '\0') 181 goto check_shell; 182 *cp++ = '\0'; 183 184 /* skip spaces before any argument */ 185 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 186 ; 187 if (*cp == '\0') 188 goto check_shell; 189 190 /* 191 * collect the shell argument. everything after the shell name 192 * is passed as ONE argument; that's the correct (historical) 193 * behaviour. 194 */ 195 shellarg = cp; 196 for ( /* cp = cp */ ; *cp != '\0'; cp++) 197 shellarglen++; 198 *cp++ = '\0'; 199 200 check_shell: 201 #ifdef SETUIDSCRIPTS 202 /* 203 * MNT_NOSUID has already taken care of by check_exec, 204 * so we don't need to worry about it now or later. We 205 * will need to check PSL_TRACED later, however. 206 */ 207 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 208 if (script_sbits != 0) { 209 script_uid = epp->ep_vap->va_uid; 210 script_gid = epp->ep_vap->va_gid; 211 } 212 #endif 213 #ifdef FDSCRIPTS 214 /* 215 * if the script isn't readable, or it's set-id, then we've 216 * gotta supply a "/dev/fd/..." for the shell to read. 217 * Note that stupid shells (csh) do the wrong thing, and 218 * close all open fd's when the start. That kills this 219 * method of implementing "safe" set-id and x-only scripts. 220 */ 221 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 222 error = VOP_ACCESS(epp->ep_vp, VREAD, l->l_cred); 223 VOP_UNLOCK(epp->ep_vp); 224 if (error == EACCES 225 #ifdef SETUIDSCRIPTS 226 || script_sbits 227 #endif 228 ) { 229 struct file *fp; 230 231 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 232 if (epp->ep_flags & EXEC_HASFD) 233 panic("exec_script_makecmds: epp already has a fd"); 234 #endif 235 236 if ((error = fd_allocfile(&fp, &epp->ep_fd)) != 0) { 237 scriptvp = NULL; 238 shellargp = NULL; 239 goto fail; 240 } 241 epp->ep_flags |= EXEC_HASFD; 242 fp->f_type = DTYPE_VNODE; 243 fp->f_ops = &vnops; 244 fp->f_data = (void *) epp->ep_vp; 245 fp->f_flag = FREAD; 246 fd_affix(curproc, fp, epp->ep_fd); 247 } 248 #endif 249 250 /* set up the fake args list */ 251 shellargp_len = 4 * sizeof(*shellargp); 252 shellargp = kmem_alloc(shellargp_len, KM_SLEEP); 253 tmpsap = shellargp; 254 tmpsap->fa_len = shellnamelen + 1; 255 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 256 strlcpy(tmpsap->fa_arg, shellname, tmpsap->fa_len); 257 tmpsap++; 258 if (shellarg != NULL) { 259 tmpsap->fa_len = shellarglen + 1; 260 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 261 strlcpy(tmpsap->fa_arg, shellarg, tmpsap->fa_len); 262 tmpsap++; 263 } 264 tmpsap->fa_len = MAXPATHLEN; 265 tmpsap->fa_arg = kmem_alloc(tmpsap->fa_len, KM_SLEEP); 266 #ifdef FDSCRIPTS 267 if ((epp->ep_flags & EXEC_HASFD) == 0) { 268 #endif 269 /* normally can't fail, but check for it if diagnostic */ 270 error = copystr(epp->ep_kname, tmpsap->fa_arg, MAXPATHLEN, 271 (size_t *)0); 272 tmpsap++; 273 #ifdef DIAGNOSTIC 274 if (error != 0) 275 panic("exec_script: copystr couldn't fail"); 276 #endif 277 #ifdef FDSCRIPTS 278 } else { 279 snprintf(tmpsap->fa_arg, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 280 tmpsap++; 281 } 282 #endif 283 tmpsap->fa_arg = NULL; 284 285 /* Save the old vnode so we can clean it up later. */ 286 scriptvp = epp->ep_vp; 287 epp->ep_vp = NULL; 288 289 /* Note that we're trying recursively. */ 290 epp->ep_flags |= EXEC_INDIR; 291 292 /* 293 * mark the header we have as invalid; check_exec will read 294 * the header from the new executable 295 */ 296 epp->ep_hdrvalid = 0; 297 298 /* try loading the interpreter */ 299 error = check_exec(l, epp, shellname); 300 301 /* note that we've clobbered the header */ 302 epp->ep_flags |= EXEC_DESTR; 303 304 if (error == 0) { 305 /* 306 * It succeeded. Unlock the script and 307 * close it if we aren't using it any more. 308 * Also, set things up so that the fake args 309 * list will be used. 310 */ 311 if ((epp->ep_flags & EXEC_HASFD) == 0) { 312 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 313 VOP_CLOSE(scriptvp, FREAD, l->l_cred); 314 vput(scriptvp); 315 } 316 317 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 318 epp->ep_fa = shellargp; 319 epp->ep_fa_len = shellargp_len; 320 #ifdef SETUIDSCRIPTS 321 /* 322 * set thing up so that set-id scripts will be 323 * handled appropriately. PSL_TRACED will be 324 * checked later when the shell is actually 325 * exec'd. 326 */ 327 epp->ep_vap->va_mode |= script_sbits; 328 if (script_sbits & S_ISUID) 329 epp->ep_vap->va_uid = script_uid; 330 if (script_sbits & S_ISGID) 331 epp->ep_vap->va_gid = script_gid; 332 #endif 333 return (0); 334 } 335 336 #ifdef FDSCRIPTS 337 fail: 338 #endif 339 340 /* kill the opened file descriptor, else close the file */ 341 if (epp->ep_flags & EXEC_HASFD) { 342 epp->ep_flags &= ~EXEC_HASFD; 343 fd_close(epp->ep_fd); 344 } else if (scriptvp) { 345 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 346 VOP_CLOSE(scriptvp, FREAD, l->l_cred); 347 vput(scriptvp); 348 } 349 350 /* free the fake arg list, because we're not returning it */ 351 if ((tmpsap = shellargp) != NULL) { 352 while (tmpsap->fa_arg != NULL) { 353 kmem_free(tmpsap->fa_arg, tmpsap->fa_len); 354 tmpsap++; 355 } 356 kmem_free(shellargp, shellargp_len); 357 } 358 359 /* 360 * free any vmspace-creation commands, 361 * and release their references 362 */ 363 kill_vmcmds(&epp->ep_vmcmds); 364 365 return error; 366 } 367