1 /* $OpenBSD: exec_script.c,v 1.25 2007/10/29 14:12:19 chl Exp $ */ 2 /* $NetBSD: exec_script.c,v 1.13 1996/02/04 02:15:06 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1993, 1994 Christopher G. Demetriou 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by Christopher G. Demetriou. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 #include <sys/param.h> 35 #include <sys/systm.h> 36 #include <sys/proc.h> 37 #include <sys/malloc.h> 38 #include <sys/pool.h> 39 #include <sys/vnode.h> 40 #include <sys/namei.h> 41 #include <sys/file.h> 42 #include <sys/filedesc.h> 43 #include <sys/exec.h> 44 #include <sys/resourcevar.h> 45 #include <uvm/uvm_extern.h> 46 47 #include <sys/exec_script.h> 48 49 #include "systrace.h" 50 51 #if NSYSTRACE > 0 52 #include <dev/systrace.h> 53 #endif 54 55 #if defined(SETUIDSCRIPTS) && !defined(FDSCRIPTS) 56 #define FDSCRIPTS /* Need this for safe set-id scripts. */ 57 #endif 58 59 /* 60 * exec_script_makecmds(): Check if it's an executable shell script. 61 * 62 * Given a proc pointer and an exec package pointer, see if the referent 63 * of the epp is in shell script. If it is, then set things up so that 64 * the script can be run. This involves preparing the address space 65 * and arguments for the shell which will run the script. 66 * 67 * This function is ultimately responsible for creating a set of vmcmds 68 * which can be used to build the process's vm space and inserting them 69 * into the exec package. 70 */ 71 int 72 exec_script_makecmds(struct proc *p, struct exec_package *epp) 73 { 74 int error, hdrlinelen, shellnamelen, shellarglen; 75 char *hdrstr = epp->ep_hdr; 76 char *cp, *shellname, *shellarg, *oldpnbuf; 77 char **shellargp = NULL, **tmpsap; 78 struct vnode *scriptvp; 79 #ifdef SETUIDSCRIPTS 80 uid_t script_uid = -1; 81 gid_t script_gid = -1; 82 u_short script_sbits; 83 #endif 84 85 /* 86 * remember the old vp and pnbuf for later, so we can restore 87 * them if check_exec() fails. 88 */ 89 scriptvp = epp->ep_vp; 90 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 91 92 /* 93 * if the magic isn't that of a shell script, or we've already 94 * done shell script processing for this exec, punt on it. 95 */ 96 if ((epp->ep_flags & EXEC_INDIR) != 0 || 97 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 98 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 99 return ENOEXEC; 100 101 /* 102 * check that the shell spec is terminated by a newline, 103 * and that it isn't too large. Don't modify the 104 * buffer unless we're ready to commit to handling it. 105 * (The latter requirement means that we have to check 106 * for both spaces and tabs later on.) 107 */ 108 hdrlinelen = min(epp->ep_hdrvalid, MAXINTERP); 109 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 110 cp++) { 111 if (*cp == '\n') { 112 *cp = '\0'; 113 break; 114 } 115 } 116 if (cp >= hdrstr + hdrlinelen) 117 return ENOEXEC; 118 119 shellname = NULL; 120 shellarg = NULL; 121 shellarglen = 0; 122 123 /* strip spaces before the shell name */ 124 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 125 cp++) 126 ; 127 128 /* collect the shell name; remember its length for later */ 129 shellname = cp; 130 shellnamelen = 0; 131 if (*cp == '\0') 132 goto check_shell; 133 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 134 shellnamelen++; 135 if (*cp == '\0') 136 goto check_shell; 137 *cp++ = '\0'; 138 139 /* skip spaces before any argument */ 140 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 141 ; 142 if (*cp == '\0') 143 goto check_shell; 144 145 /* 146 * collect the shell argument. everything after the shell name 147 * is passed as ONE argument; that's the correct (historical) 148 * behaviour. 149 */ 150 shellarg = cp; 151 for ( /* cp = cp */ ; *cp != '\0'; cp++) 152 shellarglen++; 153 *cp++ = '\0'; 154 155 check_shell: 156 #ifdef SETUIDSCRIPTS 157 /* 158 * MNT_NOSUID and STRC are already taken care of by check_exec, 159 * so we don't need to worry about them now or later. 160 */ 161 script_sbits = epp->ep_vap->va_mode & (VSUID | VSGID); 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 they start. That kills this 173 * method of implementing "safe" set-id and x-only scripts. 174 */ 175 vn_lock(scriptvp, LK_EXCLUSIVE|LK_RETRY, p); 176 error = VOP_ACCESS(scriptvp, VREAD, p->p_ucred, p); 177 VOP_UNLOCK(scriptvp, 0, p); 178 if (error == EACCES 179 #ifdef SETUIDSCRIPTS 180 || script_sbits 181 #endif 182 ) { 183 struct file *fp; 184 185 #ifdef DIAGNOSTIC 186 if (epp->ep_flags & EXEC_HASFD) 187 panic("exec_script_makecmds: epp already has a fd"); 188 #endif 189 190 if ((error = falloc(p, &fp, &epp->ep_fd))) 191 goto fail; 192 193 epp->ep_flags |= EXEC_HASFD; 194 fp->f_type = DTYPE_VNODE; 195 fp->f_ops = &vnops; 196 fp->f_data = (caddr_t) scriptvp; 197 fp->f_flag = FREAD; 198 FILE_SET_MATURE(fp); 199 } 200 #endif 201 202 /* set up the parameters for the recursive check_exec() call */ 203 epp->ep_ndp->ni_dirp = shellname; 204 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 205 epp->ep_flags |= EXEC_INDIR; 206 207 /* and set up the fake args list, for later */ 208 shellargp = malloc(4 * sizeof(char *), M_EXEC, M_WAITOK); 209 tmpsap = shellargp; 210 *tmpsap = malloc(shellnamelen + 1, M_EXEC, M_WAITOK); 211 strlcpy(*tmpsap++, shellname, shellnamelen + 1); 212 if (shellarg != NULL) { 213 *tmpsap = malloc(shellarglen + 1, M_EXEC, M_WAITOK); 214 strlcpy(*tmpsap++, shellarg, shellarglen + 1); 215 } 216 *tmpsap = malloc(MAXPATHLEN, M_EXEC, M_WAITOK); 217 #ifdef FDSCRIPTS 218 if ((epp->ep_flags & EXEC_HASFD) == 0) { 219 #endif 220 /* normally can't fail, but check for it if diagnostic */ 221 #if NSYSTRACE > 0 222 if (ISSET(p->p_flag, P_SYSTRACE)) { 223 error = systrace_scriptname(p, *tmpsap); 224 if (error == 0) 225 tmpsap++; 226 else 227 /* 228 * Since systrace_scriptname() provides a 229 * convenience, not a security issue, we are 230 * safe to do this. 231 */ 232 error = copystr(epp->ep_name, *tmpsap++, 233 MAXPATHLEN, NULL); 234 } else 235 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 236 NULL); 237 #else 238 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 239 (size_t *)0); 240 #endif 241 #ifdef DIAGNOSTIC 242 if (error != 0) 243 panic("exec_script: copyinstr couldn't fail"); 244 #endif 245 #ifdef FDSCRIPTS 246 } else 247 snprintf(*tmpsap++, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 248 #endif 249 *tmpsap = NULL; 250 251 /* 252 * mark the header we have as invalid; check_exec will read 253 * the header from the new executable 254 */ 255 epp->ep_hdrvalid = 0; 256 257 if ((error = check_exec(p, epp)) == 0) { 258 /* note that we've clobbered the header */ 259 epp->ep_flags |= EXEC_DESTR; 260 261 /* 262 * It succeeded. Unlock the script and 263 * close it if we aren't using it any more. 264 * Also, set things up so that the fake args 265 * list will be used. 266 */ 267 if ((epp->ep_flags & EXEC_HASFD) == 0) 268 vn_close(scriptvp, FREAD, p->p_ucred, p); 269 270 /* free the old pathname buffer */ 271 pool_put(&namei_pool, oldpnbuf); 272 273 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 274 epp->ep_fa = shellargp; 275 #ifdef SETUIDSCRIPTS 276 /* 277 * set things up so that set-id scripts will be 278 * handled appropriately 279 */ 280 epp->ep_vap->va_mode |= script_sbits; 281 if (script_sbits & VSUID) 282 epp->ep_vap->va_uid = script_uid; 283 if (script_sbits & VSGID) 284 epp->ep_vap->va_gid = script_gid; 285 #endif 286 return (0); 287 } 288 289 /* XXX oldpnbuf not set for "goto fail" path */ 290 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 291 #ifdef FDSCRIPTS 292 fail: 293 #endif 294 /* note that we've clobbered the header */ 295 epp->ep_flags |= EXEC_DESTR; 296 297 /* kill the opened file descriptor, else close the file */ 298 if (epp->ep_flags & EXEC_HASFD) { 299 epp->ep_flags &= ~EXEC_HASFD; 300 (void) fdrelease(p, epp->ep_fd); 301 } else 302 vn_close(scriptvp, FREAD, p->p_ucred, p); 303 304 pool_put(&namei_pool, epp->ep_ndp->ni_cnd.cn_pnbuf); 305 306 /* free the fake arg list, because we're not returning it */ 307 if ((tmpsap = shellargp) != NULL) { 308 while (*tmpsap != NULL) { 309 free(*tmpsap, M_EXEC); 310 tmpsap++; 311 } 312 free(shellargp, M_EXEC); 313 } 314 315 /* 316 * free any vmspace-creation commands, 317 * and release their references 318 */ 319 kill_vmcmds(&epp->ep_vmcmds); 320 321 return error; 322 } 323