1 /* $NetBSD: exec_script.c,v 1.30 2001/11/12 15:25:04 lukem 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 1.30 2001/11/12 15:25:04 lukem 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 56 /* 57 * exec_script_makecmds(): Check if it's an executable shell script. 58 * 59 * Given a proc pointer and an exec package pointer, see if the referent 60 * of the epp is in shell script. If it is, then set thing up so that 61 * the script can be run. This involves preparing the address space 62 * and arguments for the shell which will run the script. 63 * 64 * This function is ultimately responsible for creating a set of vmcmds 65 * which can be used to build the process's vm space and inserting them 66 * into the exec package. 67 */ 68 int 69 exec_script_makecmds(struct proc *p, struct exec_package *epp) 70 { 71 int error, hdrlinelen, shellnamelen, shellarglen; 72 char *hdrstr = epp->ep_hdr; 73 char *cp, *shellname, *shellarg, *oldpnbuf; 74 char **shellargp, **tmpsap; 75 struct vnode *scriptvp; 76 #ifdef SETUIDSCRIPTS 77 /* Gcc needs those initialized for spurious uninitialized warning */ 78 uid_t script_uid = (uid_t) -1; 79 gid_t script_gid = NOGROUP; 80 u_short script_sbits; 81 #endif 82 83 /* 84 * if the magic isn't that of a shell script, or we've already 85 * done shell script processing for this exec, punt on it. 86 */ 87 if ((epp->ep_flags & EXEC_INDIR) != 0 || 88 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 89 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 90 return ENOEXEC; 91 92 /* 93 * check that the shell spec is terminated by a newline, 94 * and that it isn't too large. Don't modify the 95 * buffer unless we're ready to commit to handling it. 96 * (The latter requirement means that we have to check 97 * for both spaces and tabs later on.) 98 */ 99 hdrlinelen = min(epp->ep_hdrvalid, MAXINTERP); 100 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 101 cp++) { 102 if (*cp == '\n') { 103 *cp = '\0'; 104 break; 105 } 106 } 107 if (cp >= hdrstr + hdrlinelen) 108 return ENOEXEC; 109 110 shellname = NULL; 111 shellarg = NULL; 112 shellarglen = 0; 113 114 /* strip spaces before the shell name */ 115 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 116 cp++) 117 ; 118 119 /* collect the shell name; remember it's length for later */ 120 shellname = cp; 121 shellnamelen = 0; 122 if (*cp == '\0') 123 goto check_shell; 124 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 125 shellnamelen++; 126 if (*cp == '\0') 127 goto check_shell; 128 *cp++ = '\0'; 129 130 /* skip spaces before any argument */ 131 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 132 ; 133 if (*cp == '\0') 134 goto check_shell; 135 136 /* 137 * collect the shell argument. everything after the shell name 138 * is passed as ONE argument; that's the correct (historical) 139 * behaviour. 140 */ 141 shellarg = cp; 142 for ( /* cp = cp */ ; *cp != '\0'; cp++) 143 shellarglen++; 144 *cp++ = '\0'; 145 146 check_shell: 147 #ifdef SETUIDSCRIPTS 148 /* 149 * MNT_NOSUID has already taken care of by check_exec, 150 * so we don't need to worry about it now or later. We 151 * will need to check P_TRACED later, however. 152 */ 153 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 154 if (script_sbits != 0) { 155 script_uid = epp->ep_vap->va_uid; 156 script_gid = epp->ep_vap->va_gid; 157 } 158 #endif 159 #ifdef FDSCRIPTS 160 /* 161 * if the script isn't readable, or it's set-id, then we've 162 * gotta supply a "/dev/fd/..." for the shell to read. 163 * Note that stupid shells (csh) do the wrong thing, and 164 * close all open fd's when the start. That kills this 165 * method of implementing "safe" set-id and x-only scripts. 166 */ 167 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 168 error = VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p); 169 VOP_UNLOCK(epp->ep_vp, 0); 170 if (error == EACCES 171 #ifdef SETUIDSCRIPTS 172 || script_sbits 173 #endif 174 ) { 175 struct file *fp; 176 177 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 178 if (epp->ep_flags & EXEC_HASFD) 179 panic("exec_script_makecmds: epp already has a fd"); 180 #endif 181 182 /* falloc() will use the descriptor for us */ 183 if ((error = falloc(p, &fp, &epp->ep_fd)) != 0) { 184 scriptvp = NULL; 185 shellargp = NULL; 186 goto fail; 187 } 188 189 epp->ep_flags |= EXEC_HASFD; 190 fp->f_type = DTYPE_VNODE; 191 fp->f_ops = &vnops; 192 fp->f_data = (caddr_t) epp->ep_vp; 193 fp->f_flag = FREAD; 194 FILE_SET_MATURE(fp); 195 FILE_UNUSE(fp, p); 196 } 197 #endif 198 199 /* set up the parameters for the recursive check_exec() call */ 200 epp->ep_ndp->ni_dirp = shellname; 201 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 202 epp->ep_flags |= EXEC_INDIR; 203 204 /* and set up the fake args list, for later */ 205 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 206 tmpsap = shellargp; 207 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 208 strcpy(*tmpsap++, shellname); 209 if (shellarg != NULL) { 210 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 211 strcpy(*tmpsap++, shellarg); 212 } 213 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 214 #ifdef FDSCRIPTS 215 if ((epp->ep_flags & EXEC_HASFD) == 0) { 216 #endif 217 /* normally can't fail, but check for it if diagnostic */ 218 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 219 (size_t *)0); 220 #ifdef DIAGNOSTIC 221 if (error != 0) 222 panic("exec_script: copyinstr couldn't fail\n"); 223 #endif 224 #ifdef FDSCRIPTS 225 } else 226 sprintf(*tmpsap++, "/dev/fd/%d", epp->ep_fd); 227 #endif 228 *tmpsap = NULL; 229 230 /* 231 * mark the header we have as invalid; check_exec will read 232 * the header from the new executable 233 */ 234 epp->ep_hdrvalid = 0; 235 236 /* 237 * remember the old vp and pnbuf for later, so we can restore 238 * them if check_exec() fails. 239 */ 240 scriptvp = epp->ep_vp; 241 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 242 243 if ((error = check_exec(p, epp)) == 0) { 244 /* note that we've clobbered the header */ 245 epp->ep_flags |= EXEC_DESTR|EXEC_HASES; 246 247 /* 248 * It succeeded. Unlock the script and 249 * close it if we aren't using it any more. 250 * Also, set things up so that the fake args 251 * list will be used. 252 */ 253 if ((epp->ep_flags & EXEC_HASFD) == 0) { 254 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 255 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 256 vput(scriptvp); 257 } 258 259 /* free the old pathname buffer */ 260 PNBUF_PUT(oldpnbuf); 261 262 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 263 epp->ep_fa = shellargp; 264 #ifdef SETUIDSCRIPTS 265 /* 266 * set thing up so that set-id scripts will be 267 * handled appropriately. P_TRACED will be 268 * checked later when the shell is actually 269 * exec'd. 270 */ 271 epp->ep_vap->va_mode |= script_sbits; 272 if (script_sbits & S_ISUID) 273 epp->ep_vap->va_uid = script_uid; 274 if (script_sbits & S_ISGID) 275 epp->ep_vap->va_gid = script_gid; 276 #endif 277 return (0); 278 } 279 280 /* XXX oldpnbuf not set for "goto fail" path */ 281 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 282 #ifdef FDSCRIPTS 283 fail: 284 #endif 285 /* note that we've clobbered the header */ 286 epp->ep_flags |= EXEC_DESTR; 287 288 /* kill the opened file descriptor, else close the file */ 289 if (epp->ep_flags & EXEC_HASFD) { 290 epp->ep_flags &= ~EXEC_HASFD; 291 (void) fdrelease(p, epp->ep_fd); 292 } else if (scriptvp) { 293 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 294 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 295 vput(scriptvp); 296 } 297 298 PNBUF_PUT(epp->ep_ndp->ni_cnd.cn_pnbuf); 299 300 /* free the fake arg list, because we're not returning it */ 301 if ((tmpsap = shellargp) != NULL) { 302 while (*tmpsap != NULL) { 303 FREE(*tmpsap, M_EXEC); 304 tmpsap++; 305 } 306 FREE(shellargp, M_EXEC); 307 } 308 309 /* 310 * free any vmspace-creation commands, 311 * and release their references 312 */ 313 kill_vmcmds(&epp->ep_vmcmds); 314 315 return error; 316 } 317