exec_script.c revision 1.2
1 /* 2 * Copyright (c) 1993, 1994 Christopher G. Demetriou 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by Christopher G. Demetriou. 16 * 4. The name of the author may not be used to endorse or promote products 17 * derived from this software withough specific prior written permission 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 * 30 * $Id: exec_script.c,v 1.2 1994/01/22 06:15:54 cgd Exp $ 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; 108 109 /* strip spaces before the shell name */ 110 for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; 111 cp++) 112 ; 113 114 /* collect the shell name; remember it's length for later */ 115 shellname = cp; 116 shellnamelen = 0; 117 if (*cp == '\0') 118 goto check_shell; 119 for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) 120 shellnamelen++; 121 if (*cp == '\0') 122 goto check_shell; 123 *cp++ = '\0'; 124 125 /* skip spaces before any argument */ 126 for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) 127 ; 128 if (*cp == '\0') 129 goto check_shell; 130 131 /* 132 * collect the shell argument. everything after the shell name 133 * is passed as ONE argument; that's the correct (historical) 134 * behaviour. 135 */ 136 shellarg = cp; 137 shellarglen = 0; 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 if (VOP_ACCESS(epp->ep_vp, VREAD, p->p_ucred, p) == EACCES || 163 script_sbits) { 164 struct file *fp; 165 extern struct fileops vnops; 166 167 #if defined(DIAGNOSTIC) && defined(FDSCRIPTS) 168 if (epp->ep_flags & EXEC_HASFD) 169 panic("exec_script_makecmds: epp already has a fd"); 170 #endif 171 172 if (error = falloc(p, &fp, &epp->ep_fd)) 173 return error; 174 175 epp->ep_flags |= EXEC_HASFD; 176 fp->f_type = DTYPE_VNODE; 177 fp->f_ops = &vnops; 178 fp->f_data = (caddr_t) epp->ep_vp; 179 fp->f_flag = FREAD; 180 } 181 #endif 182 183 /* set up the parameters for the recursive check_exec() call */ 184 epp->ep_ndp->ni_dirp = shellname; 185 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 186 epp->ep_flags |= EXEC_INDIR; 187 188 /* and set up the fake args list, for later */ 189 MALLOC(shellargp, char **, 4 * sizeof(char *), M_EXEC, M_WAITOK); 190 tmpsap = shellargp; 191 MALLOC(*tmpsap, char *, shellnamelen + 1, M_EXEC, M_WAITOK); 192 strcpy(*tmpsap++, shellname); 193 if (shellarg != NULL) { 194 MALLOC(*tmpsap, char *, shellarglen + 1, M_EXEC, M_WAITOK); 195 strcpy(*tmpsap++, shellarg); 196 } 197 MALLOC(*tmpsap, char *, MAXPATHLEN, M_EXEC, M_WAITOK); 198 #ifdef FDSCRIPTS 199 if ((epp->ep_flags & EXEC_HASFD) == 0) { 200 #endif 201 /* normally can't fail, but check for it if diagnostic */ 202 error = copyinstr(epp->ep_name, *tmpsap++, MAXPATHLEN, 0); 203 #ifdef DIAGNOSTIC 204 if (error != 0) 205 panic("exec_script: copyinstr couldn't fail\n"); 206 #endif 207 #ifdef FDSCRIPTS 208 } else 209 sprintf(*tmpsap++, "/dev/fd/%d", epp->ep_fd); 210 #endif 211 *tmpsap = NULL; 212 213 /* 214 * mark the header we have as invalid; check_exec will read 215 * the header from the new executable 216 */ 217 epp->ep_hdrvalid = 0; 218 219 /* 220 * remember the old vp and pnbuf for later, so we can restore 221 * them if check_exec() fails. 222 */ 223 scriptvp = epp->ep_vp; 224 oldpnbuf = epp->ep_ndp->ni_pnbuf; 225 226 if ((error = check_exec(p, epp)) == 0) { 227 /* 228 * It succeeded. Unlock the script and 229 * close it if we aren't using it any more. 230 * Also, et things up so that the fake args 231 * list will be used. 232 */ 233 VOP_UNLOCK(scriptvp); 234 if ((epp->ep_flags & EXEC_HASFD) == 0) 235 vn_close(scriptvp, FREAD, p->p_ucred, p); 236 237 /* free the old pathname buffer */ 238 FREE(oldpnbuf, M_NAMEI); 239 240 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 241 epp->ep_fa = shellargp; 242 #ifdef SETUIDSCRIPTS 243 /* 244 * set thing up so that set-id scripts will be 245 * handled appropriately 246 */ 247 epp->ep_vap->va_mode |= script_sbits; 248 if (script_sbits & VSUID) 249 epp->ep_vap->va_uid = script_uid; 250 if (script_sbits & VSGID) 251 epp->ep_vap->va_gid = script_gid; 252 #endif 253 } else { 254 /* 255 * Failed. restore the vnode ptr and pnbuf so that 256 * check_exec() will be able to kill them when it punts. 257 */ 258 epp->ep_vp = scriptvp; 259 epp->ep_ndp->ni_pnbuf = oldpnbuf; 260 261 /* free the fake arg list, because we're not returning it */ 262 tmpsap = shellargp; 263 while (*tmpsap != NULL) { 264 FREE(*tmpsap, M_EXEC); 265 tmpsap++; 266 } 267 FREE(shellargp, M_EXEC); 268 } 269 270 return error; 271 } 272
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