1 /* $OpenBSD: exec_script.c,v 1.39 2016/04/25 20:00:33 tedu 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/lock.h> 41 #include <sys/namei.h> 42 #include <sys/file.h> 43 #include <sys/filedesc.h> 44 #include <sys/exec.h> 45 46 #include <sys/exec_script.h> 47 48 49 /* 50 * exec_script_makecmds(): Check if it's an executable shell script. 51 * 52 * Given a proc pointer and an exec package pointer, see if the referent 53 * of the epp is in shell script. If it is, then set things up so that 54 * the script can be run. This involves preparing the address space 55 * and arguments for the shell which will run the script. 56 * 57 * This function is ultimately responsible for creating a set of vmcmds 58 * which can be used to build the process's vm space and inserting them 59 * into the exec package. 60 */ 61 int 62 exec_script_makecmds(struct proc *p, struct exec_package *epp) 63 { 64 int error, hdrlinelen, shellnamelen, shellarglen; 65 char *hdrstr = epp->ep_hdr; 66 char *cp, *shellname, *shellarg, *oldpnbuf; 67 char **shellargp = NULL, **tmpsap; 68 struct vnode *scriptvp; 69 uid_t script_uid = -1; 70 gid_t script_gid = -1; 71 u_short script_sbits; 72 73 /* 74 * remember the old vp and pnbuf for later, so we can restore 75 * them if check_exec() fails. 76 */ 77 scriptvp = epp->ep_vp; 78 oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; 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 its 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 /* 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 /* 154 * if the script isn't readable, or it's set-id, then we've 155 * gotta supply a "/dev/fd/..." for the shell to read. 156 * Note that stupid shells (csh) do the wrong thing, and 157 * close all open fd's when they start. That kills this 158 * method of implementing "safe" set-id and x-only scripts. 159 */ 160 vn_lock(scriptvp, LK_EXCLUSIVE|LK_RETRY, p); 161 error = VOP_ACCESS(scriptvp, VREAD, p->p_ucred, p); 162 VOP_UNLOCK(scriptvp, p); 163 if (error == EACCES || script_sbits) { 164 struct file *fp; 165 166 #ifdef DIAGNOSTIC 167 if (epp->ep_flags & EXEC_HASFD) 168 panic("exec_script_makecmds: epp already has a fd"); 169 #endif 170 171 fdplock(p->p_fd); 172 error = falloc(p, &fp, &epp->ep_fd); 173 fdpunlock(p->p_fd); 174 if (error) 175 goto fail; 176 177 epp->ep_flags |= EXEC_HASFD; 178 fp->f_type = DTYPE_VNODE; 179 fp->f_ops = &vnops; 180 fp->f_data = (caddr_t) scriptvp; 181 fp->f_flag = FREAD; 182 FILE_SET_MATURE(fp, p); 183 } 184 185 /* set up the parameters for the recursive check_exec() call */ 186 epp->ep_ndp->ni_dirfd = AT_FDCWD; 187 epp->ep_ndp->ni_dirp = shellname; 188 epp->ep_ndp->ni_segflg = UIO_SYSSPACE; 189 epp->ep_flags |= EXEC_INDIR; 190 191 /* and set up the fake args list, for later */ 192 shellargp = mallocarray(4, sizeof(char *), M_EXEC, M_WAITOK); 193 tmpsap = shellargp; 194 *tmpsap = malloc(shellnamelen + 1, M_EXEC, M_WAITOK); 195 strlcpy(*tmpsap++, shellname, shellnamelen + 1); 196 if (shellarg != NULL) { 197 *tmpsap = malloc(shellarglen + 1, M_EXEC, M_WAITOK); 198 strlcpy(*tmpsap++, shellarg, shellarglen + 1); 199 } 200 *tmpsap = malloc(MAXPATHLEN, M_EXEC, M_WAITOK); 201 if ((epp->ep_flags & EXEC_HASFD) == 0) { 202 error = copyinstr(epp->ep_name, *tmpsap, MAXPATHLEN, 203 NULL); 204 if (error != 0) { 205 *(tmpsap + 1) = NULL; 206 goto fail; 207 } 208 } else 209 snprintf(*tmpsap, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); 210 tmpsap++; 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 if ((error = check_exec(p, epp)) == 0) { 220 /* note that we've clobbered the header */ 221 epp->ep_flags |= EXEC_DESTR; 222 223 /* 224 * It succeeded. Unlock the script and 225 * close it if we aren't using it any more. 226 * Also, set things up so that the fake args 227 * list will be used. 228 */ 229 if ((epp->ep_flags & EXEC_HASFD) == 0) 230 vn_close(scriptvp, FREAD, p->p_ucred, p); 231 232 /* free the old pathname buffer */ 233 pool_put(&namei_pool, oldpnbuf); 234 235 epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); 236 epp->ep_fa = shellargp; 237 /* 238 * set things up so that set-id scripts will be 239 * handled appropriately 240 */ 241 epp->ep_vap->va_mode |= script_sbits; 242 if (script_sbits & VSUID) 243 epp->ep_vap->va_uid = script_uid; 244 if (script_sbits & VSGID) 245 epp->ep_vap->va_gid = script_gid; 246 return (0); 247 } 248 249 /* XXX oldpnbuf not set for "goto fail" path */ 250 epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; 251 fail: 252 /* note that we've clobbered the header */ 253 epp->ep_flags |= EXEC_DESTR; 254 255 /* kill the opened file descriptor, else close the file */ 256 if (epp->ep_flags & EXEC_HASFD) { 257 epp->ep_flags &= ~EXEC_HASFD; 258 fdplock(p->p_fd); 259 (void) fdrelease(p, epp->ep_fd); 260 fdpunlock(p->p_fd); 261 } else 262 vn_close(scriptvp, FREAD, p->p_ucred, p); 263 264 pool_put(&namei_pool, epp->ep_ndp->ni_cnd.cn_pnbuf); 265 266 /* free the fake arg list, because we're not returning it */ 267 if ((tmpsap = shellargp) != NULL) { 268 while (*tmpsap != NULL) { 269 free(*tmpsap, M_EXEC, 0); 270 tmpsap++; 271 } 272 free(shellargp, M_EXEC, 4 * sizeof(char *)); 273 } 274 275 /* 276 * free any vmspace-creation commands, 277 * and release their references 278 */ 279 kill_vmcmds(&epp->ep_vmcmds); 280 281 return error; 282 } 283