exec_script.c revision 1.28
1 /* $NetBSD: exec_script.c,v 1.28 2001/06/14 20:32:47 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 and STRC are already taken care of by check_exec, 147 * so we don't need to worry about them now or later. 148 */ 149 script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID); 150 if (script_sbits != 0) { 151 script_uid = epp->ep_vap->va_uid; 152 script_gid = epp->ep_vap->va_gid; 153 } 154 #endif 155 #ifdef FDSCRIPTS 156 /* 157 * if the script isn't readable, or it's set-id, then we've 158 * gotta supply a "/dev/fd/..." for the shell to read. 159 * Note that stupid shells (csh) do the wrong thing, and 160 * close all open fd's when the start. That kills this 161 * method of implementing "safe" set-id and x-only scripts. 162 */ 163 vn_lock(epp->ep_vp, LK_EXCLUSIVE | LK_RETRY); 164 error = VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p); 165 VOP_UNLOCK(epp->ep_vp, 0); 166 if (error == EACCES 167 #ifdef SETUIDSCRIPTS 168 || script_sbits 169 #endif 170 ) { 171 struct file *fp; 172 173 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 174 if (epp->ep_flags & EXEC_HASFD) 175 panic("exec_script_makecmds: epp already has a fd"); 176 #endif 177 178 /* falloc() will use the descriptor for us */ 179 if ((error = falloc(p, &fp, &epp->ep_fd)) != 0) { 180 scriptvp = NULL; 181 shellargp = NULL; 182 goto fail; 183 } 184 185 epp->ep_flags |= EXEC_HASFD; 186 fp->f_type = DTYPE_VNODE; 187 fp->f_ops = &vnops; 188 fp->f_data = (caddr_t) epp->ep_vp; 189 fp->f_flag = FREAD; 190 FILE_SET_MATURE(fp); 191 FILE_UNUSE(fp, p); 192 } 193 #endif 194 195 /* set up the parameters for the recursive check_exec() call */ 196 epp->ep_ndp->ni_dirp = shellname; 197 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 198 epp->ep_flags |= EXEC_INDIR; 199 200 /* and set up the fake args list, for later */ 201 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 202 tmpsap = shellargp; 203 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 204 strcpy(*tmpsap++, shellname); 205 if (shellarg != NULL) { 206 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 207 strcpy(*tmpsap++, shellarg); 208 } 209 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 210 #ifdef FDSCRIPTS 211 if ((epp->ep_flags & EXEC_HASFD) == 0) { 212 #endif 213 /* normally can't fail, but check for it if diagnostic */ 214 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 215 (size_t *)0); 216 #ifdef DIAGNOSTIC 217 if (error != 0) 218 panic("exec_script: copyinstr couldn't fail\n"); 219 #endif 220 #ifdef FDSCRIPTS 221 } else 222 sprintf(*tmpsap++, "/dev/fd/%d", epp->ep_fd); 223 #endif 224 *tmpsap = NULL; 225 226 /* 227 * mark the header we have as invalid; check_exec will read 228 * the header from the new executable 229 */ 230 epp->ep_hdrvalid = 0; 231 232 /* 233 * remember the old vp and pnbuf for later, so we can restore 234 * them if check_exec() fails. 235 */ 236 scriptvp = epp->ep_vp; 237 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 238 239 if ((error = check_exec(p, epp)) == 0) { 240 /* note that we've clobbered the header */ 241 epp->ep_flags |= EXEC_DESTR|EXEC_HASES; 242 243 /* 244 * It succeeded. Unlock the script and 245 * close it if we aren't using it any more. 246 * Also, set things up so that the fake args 247 * list will be used. 248 */ 249 if ((epp->ep_flags & EXEC_HASFD) == 0) { 250 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 251 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 252 vput(scriptvp); 253 } 254 255 /* free the old pathname buffer */ 256 PNBUF_PUT(oldpnbuf); 257 258 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 259 epp->ep_fa = shellargp; 260 #ifdef SETUIDSCRIPTS 261 /* 262 * set thing up so that set-id scripts will be 263 * handled appropriately 264 */ 265 epp->ep_vap->va_mode |= script_sbits; 266 if (script_sbits & S_ISUID) 267 epp->ep_vap->va_uid = script_uid; 268 if (script_sbits & S_ISGID) 269 epp->ep_vap->va_gid = script_gid; 270 #endif 271 return (0); 272 } 273 274 /* XXX oldpnbuf not set for "goto fail" path */ 275 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 276 #ifdef FDSCRIPTS 277 fail: 278 #endif 279 /* note that we've clobbered the header */ 280 epp->ep_flags |= EXEC_DESTR; 281 282 /* kill the opened file descriptor, else close the file */ 283 if (epp->ep_flags & EXEC_HASFD) { 284 epp->ep_flags &= ~EXEC_HASFD; 285 (void) fdrelease(p, epp->ep_fd); 286 } else if (scriptvp) { 287 vn_lock(scriptvp, LK_EXCLUSIVE | LK_RETRY); 288 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 289 vput(scriptvp); 290 } 291 292 PNBUF_PUT(epp->ep_ndp->ni_cnd.cn_pnbuf); 293 294 /* free the fake arg list, because we're not returning it */ 295 if ((tmpsap = shellargp) != NULL) { 296 while (*tmpsap != NULL) { 297 FREE(*tmpsap, M_EXEC); 298 tmpsap++; 299 } 300 FREE(shellargp, M_EXEC); 301 } 302 303 /* 304 * free any vmspace-creation commands, 305 * and release their references 306 */ 307 kill_vmcmds(&epp->ep_vmcmds); 308 309 return error; 310 } 311
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