1 /* $NetBSD: exec_script.c,v 1.45 2005/12/11 12:24:29 christos 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 1.45 2005/12/11 12:24:29 christos Exp $"); 35 36 #if defined(SETUIDSCRIPTS) && !defined(FDSCRIPTS) 37 #define FDSCRIPTS /* Need this for safe set-id scripts. */ 38 #endif 39 40 #include "opt_verified_exec.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/proc.h> 45 #include <sys/malloc.h> 46 #include <sys/vnode.h> 47 #include <sys/namei.h> 48 #include <sys/file.h> 49 #ifdef SETUIDSCRIPTS 50 #include <sys/stat.h> 51 #endif 52 #include <sys/filedesc.h> 53 #include <sys/exec.h> 54 #include <sys/resourcevar.h> 55 56 #include <sys/exec_script.h> 57 #include <sys/exec_elf.h> 58 59 #ifdef VERIFIED_EXEC 60 #include <sys/verified_exec.h> 61 #endif /* VERIFIED_EXEC */ 62 63 #ifdef SYSTRACE 64 #include <sys/systrace.h> 65 #endif /* SYSTRACE */ 66 67 /* 68 * exec_script_makecmds(): Check if it's an executable shell script. 69 * 70 * Given a proc pointer and an exec package pointer, see if the referent 71 * of the epp is in shell script. If it is, then set thing up so that 72 * the script can be run. This involves preparing the address space 73 * and arguments for the shell which will run the script. 74 * 75 * This function is ultimately responsible for creating a set of vmcmds 76 * which can be used to build the process's vm space and inserting them 77 * into the exec package. 78 */ 79 int 80 exec_script_makecmds(struct lwp *l, struct exec_package *epp) 81 { 82 int error, hdrlinelen, shellnamelen, shellarglen; 83 char *hdrstr = epp->ep_hdr; 84 char *cp, *shellname, *shellarg, *oldpnbuf; 85 char **shellargp, **tmpsap; 86 struct vnode *scriptvp; 87 struct proc *p = l->l_proc; 88 #ifdef SETUIDSCRIPTS 89 /* Gcc needs those initialized for spurious uninitialized warning */ 90 uid_t script_uid = (uid_t) -1; 91 gid_t script_gid = NOGROUP; 92 u_short script_sbits; 93 #endif 94 95 /* 96 * if the magic isn't that of a shell script, or we've already 97 * done shell script processing for this exec, punt on it. 98 */ 99 if ((epp->ep_flags & EXEC_INDIR) != 0 || 100 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 101 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 102 return ENOEXEC; 103 104 /* 105 * check that the shell spec is terminated by a newline, 106 * and that it isn't too large. Don't modify the 107 * buffer unless we're ready to commit to handling it. 108 * (The latter requirement means that we have to check 109 * for both spaces and tabs later on.) 110 */ 111 hdrlinelen = min(epp->ep_hdrvalid, SCRIPT_HDR_SIZE); 112 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 113 cp++) { 114 if (*cp == '\n') { 115 *cp = '\0'; 116 break; 117 } 118 } 119 if (cp >= hdrstr + hdrlinelen) 120 return ENOEXEC; 121 122 /* 123 * If the script has an ELF header, don't exec it. 124 */ 125 if (epp->ep_hdrvalid >= sizeof(ELFMAG)-1 && 126 memcmp(hdrstr, ELFMAG, sizeof(ELFMAG)-1) == 0) 127 return ENOEXEC; 128 129 shellname = NULL; 130 shellarg = NULL; 131 shellarglen = 0; 132 133 /* strip spaces before the shell name */ 134 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 135 cp++) 136 ; 137 138 /* collect the shell name; remember it's length for later */ 139 shellname = cp; 140 shellnamelen = 0; 141 if (*cp == '\0') 142 goto check_shell; 143 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 144 shellnamelen++; 145 if (*cp == '\0') 146 goto check_shell; 147 *cp++ = '\0'; 148 149 /* skip spaces before any argument */ 150 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 151 ; 152 if (*cp == '\0') 153 goto check_shell; 154 155 /* 156 * collect the shell argument. everything after the shell name 157 * is passed as ONE argument; that's the correct (historical) 158 * behaviour. 159 */ 160 shellarg = cp; 161 for ( /* cp = cp */ ; *cp != '\0'; cp++) 162 shellarglen++; 163 *cp++ = '\0'; 164 165 check_shell: 166 #ifdef SETUIDSCRIPTS 167 /* 168 * MNT_NOSUID has already taken care of by check_exec, 169 * so we don't need to worry about it now or later. We 170 * will need to check P_TRACED later, however. 171 */ 172 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 173 if (script_sbits != 0) { 174 script_uid = epp->ep_vap->va_uid; 175 script_gid = epp->ep_vap->va_gid; 176 } 177 #endif 178 #ifdef FDSCRIPTS 179 /* 180 * if the script isn't readable, or it's set-id, then we've 181 * gotta supply a "/dev/fd/..." for the shell to read. 182 * Note that stupid shells (csh) do the wrong thing, and 183 * close all open fd's when the start. That kills this 184 * method of implementing "safe" set-id and x-only scripts. 185 */ 186 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 187 error = VOP_ACCESS(epp->ep_vp, VREAD, l->l_proc->p_ucred, l); 188 VOP_UNLOCK(epp->ep_vp, 0); 189 if (error == EACCES 190 #ifdef SETUIDSCRIPTS 191 || script_sbits 192 #endif 193 ) { 194 struct file *fp; 195 196 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 197 if (epp->ep_flags & EXEC_HASFD) 198 panic("exec_script_makecmds: epp already has a fd"); 199 #endif 200 201 /* falloc() will use the descriptor for us */ 202 if ((error = falloc(p, &fp, &epp->ep_fd)) != 0) { 203 scriptvp = NULL; 204 shellargp = NULL; 205 goto fail; 206 } 207 208 epp->ep_flags |= EXEC_HASFD; 209 fp->f_type = DTYPE_VNODE; 210 fp->f_ops = &vnops; 211 fp->f_data = (caddr_t) epp->ep_vp; 212 fp->f_flag = FREAD; 213 FILE_SET_MATURE(fp); 214 FILE_UNUSE(fp, l); 215 } 216 #endif 217 218 /* set up the parameters for the recursive check_exec() call */ 219 epp->ep_ndp->ni_dirp = shellname; 220 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 221 epp->ep_flags |= EXEC_INDIR; 222 223 /* and set up the fake args list, for later */ 224 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 225 tmpsap = shellargp; 226 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 227 strlcpy(*tmpsap++, shellname, shellnamelen + 1); 228 if (shellarg != NULL) { 229 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 230 strlcpy(*tmpsap++, shellarg, shellarglen + 1); 231 } 232 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 233 #ifdef FDSCRIPTS 234 if ((epp->ep_flags & EXEC_HASFD) == 0) { 235 #endif 236 /* normally can't fail, but check for it if diagnostic */ 237 #ifdef SYSTRACE 238 error = 1; 239 if (ISSET(p->p_flag, P_SYSTRACE)) { 240 error = systrace_scriptname(p, *tmpsap); 241 if (error == 0) 242 tmpsap++; 243 } 244 if (error) { 245 /* 246 * Since systrace_scriptname() provides a 247 * convenience, not a security issue, we are 248 * safe to do this. 249 */ 250 error = copystr(epp->ep_name, *tmpsap++, MAXPATHLEN, 251 NULL); 252 } 253 #else 254 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 255 (size_t *)0); 256 #endif /* SYSTRACE */ 257 #ifdef DIAGNOSTIC 258 if (error != 0) 259 panic("exec_script: copyinstr couldn't fail"); 260 #endif 261 #ifdef FDSCRIPTS 262 } else 263 snprintf(*tmpsap++, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 264 #endif 265 *tmpsap = NULL; 266 267 /* 268 * mark the header we have as invalid; check_exec will read 269 * the header from the new executable 270 */ 271 epp->ep_hdrvalid = 0; 272 273 /* 274 * remember the old vp and pnbuf for later, so we can restore 275 * them if check_exec() fails. 276 */ 277 scriptvp = epp->ep_vp; 278 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 279 280 #ifdef VERIFIED_EXEC 281 if ((error = check_exec(l, epp, VERIEXEC_INDIRECT)) == 0) { 282 #else 283 if ((error = check_exec(l, epp, 0)) == 0) { 284 #endif 285 /* note that we've clobbered the header */ 286 epp->ep_flags |= EXEC_DESTR|EXEC_HASES; 287 288 /* 289 * It succeeded. Unlock the script and 290 * close it if we aren't using it any more. 291 * Also, set things up so that the fake args 292 * list will be used. 293 */ 294 if ((epp->ep_flags & EXEC_HASFD) == 0) { 295 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 296 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, l); 297 vput(scriptvp); 298 } 299 300 /* free the old pathname buffer */ 301 PNBUF_PUT(oldpnbuf); 302 303 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 304 epp->ep_fa = shellargp; 305 #ifdef SETUIDSCRIPTS 306 /* 307 * set thing up so that set-id scripts will be 308 * handled appropriately. P_TRACED will be 309 * checked later when the shell is actually 310 * exec'd. 311 */ 312 epp->ep_vap->va_mode |= script_sbits; 313 if (script_sbits & S_ISUID) 314 epp->ep_vap->va_uid = script_uid; 315 if (script_sbits & S_ISGID) 316 epp->ep_vap->va_gid = script_gid; 317 #endif 318 return (0); 319 } 320 321 /* XXX oldpnbuf not set for "goto fail" path */ 322 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 323 #ifdef FDSCRIPTS 324 fail: 325 #endif 326 /* note that we've clobbered the header */ 327 epp->ep_flags |= EXEC_DESTR; 328 329 /* kill the opened file descriptor, else close the file */ 330 if (epp->ep_flags & EXEC_HASFD) { 331 epp->ep_flags &= ~EXEC_HASFD; 332 (void) fdrelease(l, epp->ep_fd); 333 } else if (scriptvp) { 334 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 335 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, l); 336 vput(scriptvp); 337 } 338 339 PNBUF_PUT(epp->ep_ndp->ni_cnd.cn_pnbuf); 340 341 /* free the fake arg list, because we're not returning it */ 342 if ((tmpsap = shellargp) != NULL) { 343 while (*tmpsap != NULL) { 344 FREE(*tmpsap, M_EXEC); 345 tmpsap++; 346 } 347 FREE(shellargp, M_EXEC); 348 } 349 350 /* 351 * free any vmspace-creation commands, 352 * and release their references 353 */ 354 kill_vmcmds(&epp->ep_vmcmds); 355 356 return error; 357 } 358