1 /* $NetBSD: exec_script.c,v 1.38 2004/11/04 23:55:28 matt 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 1.38 2004/11/04 23:55:28 matt 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/malloc.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 54 #include <sys/exec_script.h> 55 #include <sys/exec_elf.h> 56 57 /* 58 * exec_script_makecmds(): Check if it's an executable shell script. 59 * 60 * Given a proc pointer and an exec package pointer, see if the referent 61 * of the epp is in shell script. If it is, then set thing up so that 62 * the script can be run. This involves preparing the address space 63 * and arguments for the shell which will run the script. 64 * 65 * This function is ultimately responsible for creating a set of vmcmds 66 * which can be used to build the process's vm space and inserting them 67 * into the exec package. 68 */ 69 int 70 exec_script_makecmds(struct proc *p, struct exec_package *epp) 71 { 72 int error, hdrlinelen, shellnamelen, shellarglen; 73 char *hdrstr = epp->ep_hdr; 74 char *cp, *shellname, *shellarg, *oldpnbuf; 75 char **shellargp, **tmpsap; 76 struct vnode *scriptvp; 77 #ifdef SETUIDSCRIPTS 78 /* Gcc needs those initialized for spurious uninitialized warning */ 79 uid_t script_uid = (uid_t) -1; 80 gid_t script_gid = NOGROUP; 81 u_short script_sbits; 82 #endif 83 84 /* 85 * if the magic isn't that of a shell script, or we've already 86 * done shell script processing for this exec, punt on it. 87 */ 88 if ((epp->ep_flags & EXEC_INDIR) != 0 || 89 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 90 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 91 return ENOEXEC; 92 93 /* 94 * check that the shell spec is terminated by a newline, 95 * and that it isn't too large. Don't modify the 96 * buffer unless we're ready to commit to handling it. 97 * (The latter requirement means that we have to check 98 * for both spaces and tabs later on.) 99 */ 100 hdrlinelen = min(epp->ep_hdrvalid, SCRIPT_HDR_SIZE); 101 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 102 cp++) { 103 if (*cp == '\n') { 104 *cp = '\0'; 105 break; 106 } 107 } 108 if (cp >= hdrstr + hdrlinelen) 109 return ENOEXEC; 110 111 /* 112 * If the script has an ELF header, don't exec it. 113 */ 114 if (epp->ep_hdrvalid >= sizeof(ELFMAG)-1 && 115 memcmp(hdrstr, ELFMAG, sizeof(ELFMAG)-1) == 0) 116 return ENOEXEC; 117 118 shellname = NULL; 119 shellarg = NULL; 120 shellarglen = 0; 121 122 /* strip spaces before the shell name */ 123 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 124 cp++) 125 ; 126 127 /* collect the shell name; remember it's length for later */ 128 shellname = cp; 129 shellnamelen = 0; 130 if (*cp == '\0') 131 goto check_shell; 132 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 133 shellnamelen++; 134 if (*cp == '\0') 135 goto check_shell; 136 *cp++ = '\0'; 137 138 /* skip spaces before any argument */ 139 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 140 ; 141 if (*cp == '\0') 142 goto check_shell; 143 144 /* 145 * collect the shell argument. everything after the shell name 146 * is passed as ONE argument; that's the correct (historical) 147 * behaviour. 148 */ 149 shellarg = cp; 150 for ( /* cp = cp */ ; *cp != '\0'; cp++) 151 shellarglen++; 152 *cp++ = '\0'; 153 154 check_shell: 155 #ifdef SETUIDSCRIPTS 156 /* 157 * MNT_NOSUID has already taken care of by check_exec, 158 * so we don't need to worry about it now or later. We 159 * will need to check P_TRACED later, however. 160 */ 161 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 162 if (script_sbits != 0) { 163 script_uid = epp->ep_vap->va_uid; 164 script_gid = epp->ep_vap->va_gid; 165 } 166 #endif 167 #ifdef FDSCRIPTS 168 /* 169 * if the script isn't readable, or it's set-id, then we've 170 * gotta supply a "/dev/fd/..." for the shell to read. 171 * Note that stupid shells (csh) do the wrong thing, and 172 * close all open fd's when the start. That kills this 173 * method of implementing "safe" set-id and x-only scripts. 174 */ 175 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 176 error = VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p); 177 VOP_UNLOCK(epp->ep_vp, 0); 178 if (error == EACCES 179 #ifdef SETUIDSCRIPTS 180 || script_sbits 181 #endif 182 ) { 183 struct file *fp; 184 185 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 186 if (epp->ep_flags & EXEC_HASFD) 187 panic("exec_script_makecmds: epp already has a fd"); 188 #endif 189 190 /* falloc() will use the descriptor for us */ 191 if ((error = falloc(p, &fp, &epp->ep_fd)) != 0) { 192 scriptvp = NULL; 193 shellargp = NULL; 194 goto fail; 195 } 196 197 epp->ep_flags |= EXEC_HASFD; 198 fp->f_type = DTYPE_VNODE; 199 fp->f_ops = &vnops; 200 fp->f_data = (caddr_t) epp->ep_vp; 201 fp->f_flag = FREAD; 202 FILE_SET_MATURE(fp); 203 FILE_UNUSE(fp, p); 204 } 205 #endif 206 207 /* set up the parameters for the recursive check_exec() call */ 208 epp->ep_ndp->ni_dirp = shellname; 209 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 210 epp->ep_flags |= EXEC_INDIR; 211 212 /* and set up the fake args list, for later */ 213 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 214 tmpsap = shellargp; 215 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 216 strlcpy(*tmpsap++, shellname, shellnamelen + 1); 217 if (shellarg != NULL) { 218 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 219 strlcpy(*tmpsap++, shellarg, shellarglen + 1); 220 } 221 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 222 #ifdef FDSCRIPTS 223 if ((epp->ep_flags & EXEC_HASFD) == 0) { 224 #endif 225 /* normally can't fail, but check for it if diagnostic */ 226 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 227 (size_t *)0); 228 #ifdef DIAGNOSTIC 229 if (error != 0) 230 panic("exec_script: copyinstr couldn't fail"); 231 #endif 232 #ifdef FDSCRIPTS 233 } else 234 snprintf(*tmpsap++, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 235 #endif 236 *tmpsap = NULL; 237 238 /* 239 * mark the header we have as invalid; check_exec will read 240 * the header from the new executable 241 */ 242 epp->ep_hdrvalid = 0; 243 244 /* 245 * remember the old vp and pnbuf for later, so we can restore 246 * them if check_exec() fails. 247 */ 248 scriptvp = epp->ep_vp; 249 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 250 251 #ifdef VERIFIED_EXEC 252 if ((error = check_exec(p, epp, 0)) == 0) { 253 #else 254 if ((error = check_exec(p, epp)) == 0) { 255 #endif 256 /* note that we've clobbered the header */ 257 epp->ep_flags |= EXEC_DESTR|EXEC_HASES; 258 259 /* 260 * It succeeded. Unlock the script and 261 * close it if we aren't using it any more. 262 * Also, set things up so that the fake args 263 * list will be used. 264 */ 265 if ((epp->ep_flags & EXEC_HASFD) == 0) { 266 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 267 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 268 vput(scriptvp); 269 } 270 271 /* free the old pathname buffer */ 272 PNBUF_PUT(oldpnbuf); 273 274 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 275 epp->ep_fa = shellargp; 276 #ifdef SETUIDSCRIPTS 277 /* 278 * set thing up so that set-id scripts will be 279 * handled appropriately. P_TRACED will be 280 * checked later when the shell is actually 281 * exec'd. 282 */ 283 epp->ep_vap->va_mode |= script_sbits; 284 if (script_sbits & S_ISUID) 285 epp->ep_vap->va_uid = script_uid; 286 if (script_sbits & S_ISGID) 287 epp->ep_vap->va_gid = script_gid; 288 #endif 289 return (0); 290 } 291 292 /* XXX oldpnbuf not set for "goto fail" path */ 293 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 294 #ifdef FDSCRIPTS 295 fail: 296 #endif 297 /* note that we've clobbered the header */ 298 epp->ep_flags |= EXEC_DESTR; 299 300 /* kill the opened file descriptor, else close the file */ 301 if (epp->ep_flags & EXEC_HASFD) { 302 epp->ep_flags &= ~EXEC_HASFD; 303 (void) fdrelease(p, epp->ep_fd); 304 } else if (scriptvp) { 305 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 306 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 307 vput(scriptvp); 308 } 309 310 PNBUF_PUT(epp->ep_ndp->ni_cnd.cn_pnbuf); 311 312 /* free the fake arg list, because we're not returning it */ 313 if ((tmpsap = shellargp) != NULL) { 314 while (*tmpsap != NULL) { 315 FREE(*tmpsap, M_EXEC); 316 tmpsap++; 317 } 318 FREE(shellargp, M_EXEC); 319 } 320 321 /* 322 * free any vmspace-creation commands, 323 * and release their references 324 */ 325 kill_vmcmds(&epp->ep_vmcmds); 326 327 return error; 328 } 329