exec_script.c revision 1.16
1 /* $NetBSD: exec_script.c,v 1.16 1996/10/13 02:32:29 christos 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 #include <sys/filedesc.h> 45 #include <sys/exec.h> 46 #include <sys/resourcevar.h> 47 #include <vm/vm.h> 48 49 #include <sys/exec_script.h> 50 51 /* 52 * exec_script_makecmds(): Check if it's an executable shell script. 53 * 54 * Given a proc pointer and an exec package pointer, see if the referent 55 * of the epp is in shell script. If it is, then set thing up so that 56 * the script can be run. This involves preparing the address space 57 * and arguments for the shell which will run the script. 58 * 59 * This function is ultimately responsible for creating a set of vmcmds 60 * which can be used to build the process's vm space and inserting them 61 * into the exec package. 62 */ 63 int 64 exec_script_makecmds(p, epp) 65 struct proc *p; 66 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 uid_t script_uid; 75 gid_t script_gid; 76 u_short script_sbits; 77 #endif 78 79 /* 80 * if the magic isn't that of a shell script, or we've already 81 * done shell script processing for this exec, punt on it. 82 */ 83 if ((epp->ep_flags & EXEC_INDIR) != 0 || 84 epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || 85 strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) 86 return ENOEXEC; 87 88 /* 89 * check that the shell spec is terminated by a newline, 90 * and that it isn't too large. Don't modify the 91 * buffer unless we're ready to commit to handling it. 92 * (The latter requirement means that we have to check 93 * for both spaces and tabs later on.) 94 */ 95 hdrlinelen = min(epp->ep_hdrvalid, MAXINTERP); 96 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; 97 cp++) { 98 if (*cp == '\n') { 99 *cp = '\0'; 100 break; 101 } 102 } 103 if (cp >= hdrstr + hdrlinelen) 104 return ENOEXEC; 105 106 shellname = NULL; 107 shellarg = NULL; 108 shellarglen = 0; 109 110 /* strip spaces before the shell name */ 111 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 112 cp++) 113 ; 114 115 /* collect the shell name; remember it's length for later */ 116 shellname = cp; 117 shellnamelen = 0; 118 if (*cp == '\0') 119 goto check_shell; 120 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 121 shellnamelen++; 122 if (*cp == '\0') 123 goto check_shell; 124 *cp++ = '\0'; 125 126 /* skip spaces before any argument */ 127 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 128 ; 129 if (*cp == '\0') 130 goto check_shell; 131 132 /* 133 * collect the shell argument. everything after the shell name 134 * is passed as ONE argument; that's the correct (historical) 135 * behaviour. 136 */ 137 shellarg = cp; 138 for ( /* cp = cp */ ; *cp != '\0'; cp++) 139 shellarglen++; 140 *cp++ = '\0'; 141 142 check_shell: 143 #ifdef SETUIDSCRIPTS 144 /* 145 * MNT_NOSUID and STRC are already taken care of by check_exec, 146 * so we don't need to worry about them now or later. 147 */ 148 script_sbits = epp->ep_vap->va_mode & (VSUID | VSGID); 149 if (script_sbits != 0) { 150 script_uid = epp->ep_vap->va_uid; 151 script_gid = epp->ep_vap->va_gid; 152 } 153 #endif 154 #ifdef FDSCRIPTS 155 /* 156 * if the script isn't readable, or it's set-id, then we've 157 * gotta supply a "/dev/fd/..." for the shell to read. 158 * Note that stupid shells (csh) do the wrong thing, and 159 * close all open fd's when the start. That kills this 160 * method of implementing "safe" set-id and x-only scripts. 161 */ 162 VOP_LOCK(epp->ep_vp); 163 error = VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p); 164 VOP_UNLOCK(epp->ep_vp); 165 if (error == EACCES 166 #ifdef SETUIDSCRIPTS 167 || script_sbits 168 #endif 169 ) { 170 struct file *fp; 171 extern struct fileops vnops; 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 if (error = falloc(p, &fp, &epp->ep_fd)) 179 goto fail; 180 181 epp->ep_flags |= EXEC_HASFD; 182 fp->f_type = DTYPE_VNODE; 183 fp->f_ops = &vnops; 184 fp->f_data = (caddr_t) epp->ep_vp; 185 fp->f_flag = FREAD; 186 } 187 #endif 188 189 /* set up the parameters for the recursive check_exec() call */ 190 epp->ep_ndp->ni_dirp = shellname; 191 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 192 epp->ep_flags |= EXEC_INDIR; 193 194 /* and set up the fake args list, for later */ 195 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 196 tmpsap = shellargp; 197 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 198 strcpy(*tmpsap++, shellname); 199 if (shellarg != NULL) { 200 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 201 strcpy(*tmpsap++, shellarg); 202 } 203 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 204 #ifdef FDSCRIPTS 205 if ((epp->ep_flags & EXEC_HASFD) == 0) { 206 #endif 207 /* normally can't fail, but check for it if diagnostic */ 208 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 209 (size_t *)0); 210 #ifdef DIAGNOSTIC 211 if (error != 0) 212 panic("exec_script: copyinstr couldn't fail\n"); 213 #endif 214 #ifdef FDSCRIPTS 215 } else 216 sprintf(*tmpsap++, "/dev/fd/%d", epp->ep_fd); 217 #endif 218 *tmpsap = NULL; 219 220 /* 221 * mark the header we have as invalid; check_exec will read 222 * the header from the new executable 223 */ 224 epp->ep_hdrvalid = 0; 225 226 /* 227 * remember the old vp and pnbuf for later, so we can restore 228 * them if check_exec() fails. 229 */ 230 scriptvp = epp->ep_vp; 231 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 232 233 if ((error = check_exec(p, epp)) == 0) { 234 /* note that we've clobbered the header */ 235 epp->ep_flags |= EXEC_DESTR; 236 237 /* 238 * It succeeded. Unlock the script and 239 * close it if we aren't using it any more. 240 * Also, set things up so that the fake args 241 * list will be used. 242 */ 243 if ((epp->ep_flags & EXEC_HASFD) == 0) { 244 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 245 vrele(scriptvp); 246 } 247 248 /* free the old pathname buffer */ 249 FREE(oldpnbuf, M_NAMEI); 250 251 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 252 epp->ep_fa = shellargp; 253 #ifdef SETUIDSCRIPTS 254 /* 255 * set thing up so that set-id scripts will be 256 * handled appropriately 257 */ 258 epp->ep_vap->va_mode |= script_sbits; 259 if (script_sbits & VSUID) 260 epp->ep_vap->va_uid = script_uid; 261 if (script_sbits & VSGID) 262 epp->ep_vap->va_gid = script_gid; 263 #endif 264 return (0); 265 } 266 267 /* XXX oldpnbuf not set for "goto fail" path */ 268 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 269 #ifdef FDSCRIPTS 270 fail: 271 #endif 272 /* note that we've clobbered the header */ 273 epp->ep_flags |= EXEC_DESTR; 274 275 /* kill the opened file descriptor, else close the file */ 276 if (epp->ep_flags & EXEC_HASFD) { 277 epp->ep_flags &= ~EXEC_HASFD; 278 (void) fdrelease(p, epp->ep_fd); 279 } else { 280 VOP_CLOSE(scriptvp, FREAD, p->p_ucred, p); 281 vrele(scriptvp); 282 } 283 284 FREE(epp->ep_ndp->ni_cnd.cn_pnbuf, M_NAMEI); 285 286 /* free the fake arg list, because we're not returning it */ 287 tmpsap = shellargp; 288 while (*tmpsap != NULL) { 289 FREE(*tmpsap, M_EXEC); 290 tmpsap++; 291 } 292 FREE(shellargp, M_EXEC); 293 294 /* 295 * free any vmspace-creation commands, 296 * and release their references 297 */ 298 kill_vmcmds(&epp->ep_vmcmds); 299 300 return error; 301 } 302
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