exec_script.c revision 1.29
1 /* $NetBSD: exec_script.c,v 1.29 2001/06/15 17:24:19 thorpej 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 #if defined(SETUIDSCRIPTS) && !defined(FDSCRIPTS) 34 #define FDSCRIPTS /* Need this for safe set-id scripts. */ 35 #endif 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/proc.h> 40 #include <sys/malloc.h> 41 #include <sys/vnode.h> 42 #include <sys/namei.h> 43 #include <sys/file.h> 44 #ifdef SETUIDSCRIPTS 45 #include <sys/stat.h> 46 #endif 47 #include <sys/filedesc.h> 48 #include <sys/exec.h> 49 #include <sys/resourcevar.h> 50 51 #include <sys/exec_script.h> 52 53 /* 54 * exec_script_makecmds(): Check if it's an executable shell script. 55 * 56 * Given a proc pointer and an exec package pointer, see if the referent 57 * of the epp is in shell script. If it is, then set thing up so that 58 * the script can be run. This involves preparing the address space 59 * and arguments for the shell which will run the script. 60 * 61 * This function is ultimately responsible for creating a set of vmcmds 62 * which can be used to build the process's vm space and inserting them 63 * into the exec package. 64 */ 65 int 66 exec_script_makecmds(struct proc *p, struct exec_package *epp) 67 { 68 int error, hdrlinelen, shellnamelen, shellarglen; 69 char *hdrstr = epp->ep_hdr; 70 char *cp, *shellname, *shellarg, *oldpnbuf; 71 char **shellargp, **tmpsap; 72 struct vnode *scriptvp; 73 #ifdef SETUIDSCRIPTS 74 /* Gcc needs those initialized for spurious uninitialized warning */ 75 uid_t script_uid = (uid_t) -1; 76 gid_t script_gid = NOGROUP; 77 u_short script_sbits; 78 #endif 79 80 /* 81 * if the magic isn't that of a shell script, or we've already 82 * done shell script processing for this exec, punt on it. 83 */ 84 if ((epp->ep_flags & EXEC_INDIR) != 0 || 85 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 86 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 87 return ENOEXEC; 88 89 /* 90 * check that the shell spec is terminated by a newline, 91 * and that it isn't too large. Don't modify the 92 * buffer unless we're ready to commit to handling it. 93 * (The latter requirement means that we have to check 94 * for both spaces and tabs later on.) 95 */ 96 hdrlinelen = min(epp->ep_hdrvalid, MAXINTERP); 97 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 98 cp++) { 99 if (*cp == '\n') { 100 *cp = '\0'; 101 break; 102 } 103 } 104 if (cp >= hdrstr + hdrlinelen) 105 return ENOEXEC; 106 107 shellname = NULL; 108 shellarg = NULL; 109 shellarglen = 0; 110 111 /* strip spaces before the shell name */ 112 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 113 cp++) 114 ; 115 116 /* collect the shell name; remember it's length for later */ 117 shellname = cp; 118 shellnamelen = 0; 119 if (*cp == '\0') 120 goto check_shell; 121 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 122 shellnamelen++; 123 if (*cp == '\0') 124 goto check_shell; 125 *cp++ = '\0'; 126 127 /* skip spaces before any argument */ 128 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 129 ; 130 if (*cp == '\0') 131 goto check_shell; 132 133 /* 134 * collect the shell argument. everything after the shell name 135 * is passed as ONE argument; that's the correct (historical) 136 * behaviour. 137 */ 138 shellarg = cp; 139 for ( /* cp = cp */ ; *cp != '\0'; cp++) 140 shellarglen++; 141 *cp++ = '\0'; 142 143 check_shell: 144 #ifdef SETUIDSCRIPTS 145 /* 146 * MNT_NOSUID has already taken care of by check_exec, 147 * so we don't need to worry about it now or later. We 148 * will need to check P_TRACED later, however. 149 */ 150 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 151 if (script_sbits != 0) { 152 script_uid = epp->ep_vap->va_uid; 153 script_gid = epp->ep_vap->va_gid; 154 } 155 #endif 156 #ifdef FDSCRIPTS 157 /* 158 * if the script isn't readable, or it's set-id, then we've 159 * gotta supply a "/dev/fd/..." for the shell to read. 160 * Note that stupid shells (csh) do the wrong thing, and 161 * close all open fd's when the start. That kills this 162 * method of implementing "safe" set-id and x-only scripts. 163 */ 164 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 165 error = VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p); 166 VOP_UNLOCK(epp->ep_vp, 0); 167 if (error == EACCES 168 #ifdef SETUIDSCRIPTS 169 || script_sbits 170 #endif 171 ) { 172 struct file *fp; 173 174 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 175 if (epp->ep_flags & EXEC_HASFD) 176 panic("exec_script_makecmds: epp already has a fd"); 177 #endif 178 179 /* falloc() will use the descriptor for us */ 180 if ((error = falloc(p, &fp, &epp->ep_fd)) != 0) { 181 scriptvp = NULL; 182 shellargp = NULL; 183 goto fail; 184 } 185 186 epp->ep_flags |= EXEC_HASFD; 187 fp->f_type = DTYPE_VNODE; 188 fp->f_ops = &vnops; 189 fp->f_data = (caddr_t) epp->ep_vp; 190 fp->f_flag = FREAD; 191 FILE_SET_MATURE(fp); 192 FILE_UNUSE(fp, p); 193 } 194 #endif 195 196 /* set up the parameters for the recursive check_exec() call */ 197 epp->ep_ndp->ni_dirp = shellname; 198 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 199 epp->ep_flags |= EXEC_INDIR; 200 201 /* and set up the fake args list, for later */ 202 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 203 tmpsap = shellargp; 204 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 205 strcpy(*tmpsap++, shellname); 206 if (shellarg != NULL) { 207 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 208 strcpy(*tmpsap++, shellarg); 209 } 210 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 211 #ifdef FDSCRIPTS 212 if ((epp->ep_flags & EXEC_HASFD) == 0) { 213 #endif 214 /* normally can't fail, but check for it if diagnostic */ 215 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 216 (size_t *)0); 217 #ifdef DIAGNOSTIC 218 if (error != 0) 219 panic("exec_script: copyinstr couldn't fail\n"); 220 #endif 221 #ifdef FDSCRIPTS 222 } else 223 sprintf(*tmpsap++, "/dev/fd/%d", epp->ep_fd); 224 #endif 225 *tmpsap = NULL; 226 227 /* 228 * mark the header we have as invalid; check_exec will read 229 * the header from the new executable 230 */ 231 epp->ep_hdrvalid = 0; 232 233 /* 234 * remember the old vp and pnbuf for later, so we can restore 235 * them if check_exec() fails. 236 */ 237 scriptvp = epp->ep_vp; 238 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 239 240 if ((error = check_exec(p, epp)) == 0) { 241 /* note that we've clobbered the header */ 242 epp->ep_flags |= EXEC_DESTR|EXEC_HASES; 243 244 /* 245 * It succeeded. Unlock the script and 246 * close it if we aren't using it any more. 247 * Also, set things up so that the fake args 248 * list will be used. 249 */ 250 if ((epp->ep_flags & EXEC_HASFD) == 0) { 251 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 252 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 253 vput(scriptvp); 254 } 255 256 /* free the old pathname buffer */ 257 PNBUF_PUT(oldpnbuf); 258 259 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 260 epp->ep_fa = shellargp; 261 #ifdef SETUIDSCRIPTS 262 /* 263 * set thing up so that set-id scripts will be 264 * handled appropriately. P_TRACED will be 265 * checked later when the shell is actually 266 * exec'd. 267 */ 268 epp->ep_vap->va_mode |= script_sbits; 269 if (script_sbits & S_ISUID) 270 epp->ep_vap->va_uid = script_uid; 271 if (script_sbits & S_ISGID) 272 epp->ep_vap->va_gid = script_gid; 273 #endif 274 return (0); 275 } 276 277 /* XXX oldpnbuf not set for "goto fail" path */ 278 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 279 #ifdef FDSCRIPTS 280 fail: 281 #endif 282 /* note that we've clobbered the header */ 283 epp->ep_flags |= EXEC_DESTR; 284 285 /* kill the opened file descriptor, else close the file */ 286 if (epp->ep_flags & EXEC_HASFD) { 287 epp->ep_flags &= ~EXEC_HASFD; 288 (void) fdrelease(p, epp->ep_fd); 289 } else if (scriptvp) { 290 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 291 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 292 vput(scriptvp); 293 } 294 295 PNBUF_PUT(epp->ep_ndp->ni_cnd.cn_pnbuf); 296 297 /* free the fake arg list, because we're not returning it */ 298 if ((tmpsap = shellargp) != NULL) { 299 while (*tmpsap != NULL) { 300 FREE(*tmpsap, M_EXEC); 301 tmpsap++; 302 } 303 FREE(shellargp, M_EXEC); 304 } 305 306 /* 307 * free any vmspace-creation commands, 308 * and release their references 309 */ 310 kill_vmcmds(&epp->ep_vmcmds); 311 312 return error; 313 } 314
Indexes created Fri Oct 03 17:10:05 GMT 2025