/* $OpenBSD: exec_script.c,v 1.48 2019/07/15 04:11:03 visa Exp $ */ /* $NetBSD: exec_script.c,v 1.13 1996/02/04 02:15:06 christos Exp $ */ /* * Copyright (c) 1993, 1994 Christopher G. Demetriou * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by Christopher G. Demetriou. * 4. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include <sys/param.h> #include <sys/systm.h> #include <sys/proc.h> #include <sys/malloc.h> #include <sys/pool.h> #include <sys/vnode.h> #include <sys/lock.h> #include <sys/namei.h> #include <sys/fcntl.h> #include <sys/file.h> #include <sys/filedesc.h> #include <sys/exec.h> #include <sys/exec_script.h> /* * exec_script_makecmds(): Check if it's an executable shell script. * * Given a proc pointer and an exec package pointer, see if the referent * of the epp is in shell script. If it is, then set things up so that * the script can be run. This involves preparing the address space * and arguments for the shell which will run the script. * * This function is ultimately responsible for creating a set of vmcmds * which can be used to build the process's vm space and inserting them * into the exec package. */ int exec_script_makecmds(struct proc *p, struct exec_package *epp) { int error, hdrlinelen, shellnamelen, shellarglen; char *hdrstr = epp->ep_hdr; char *cp, *shellname, *shellarg, *oldpnbuf; char **shellargp = NULL, **tmpsap; struct vnode *scriptvp; uid_t script_uid = -1; gid_t script_gid = -1; u_short script_sbits; /* * remember the old vp and pnbuf for later, so we can restore * them if check_exec() fails. */ scriptvp = epp->ep_vp; oldpnbuf = epp->ep_ndp->ni_cnd.cn_pnbuf; /* * if the magic isn't that of a shell script, or we've already * done shell script processing for this exec, punt on it. */ if ((epp->ep_flags & EXEC_INDIR) != 0 || epp->ep_hdrvalid < EXEC_SCRIPT_MAGICLEN || strncmp(hdrstr, EXEC_SCRIPT_MAGIC, EXEC_SCRIPT_MAGICLEN)) return ENOEXEC; /* * check that the shell spec is terminated by a newline, * and that it isn't too large. Don't modify the * buffer unless we're ready to commit to handling it. * (The latter requirement means that we have to check * for both spaces and tabs later on.) */ hdrlinelen = min(epp->ep_hdrvalid, MAXINTERP); for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; cp < hdrstr + hdrlinelen; cp++) { if (*cp == '\n') { *cp = '\0'; break; } } if (cp >= hdrstr + hdrlinelen) return ENOEXEC; shellname = NULL; shellarg = NULL; shellarglen = 0; /* strip spaces before the shell name */ for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t'; cp++) ; /* collect the shell name; remember its length for later */ shellname = cp; shellnamelen = 0; if (*cp == '\0') goto check_shell; for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++) shellnamelen++; if (*cp == '\0') goto check_shell; *cp++ = '\0'; /* skip spaces before any argument */ for ( /* cp = cp */ ; *cp == ' ' || *cp == '\t'; cp++) ; if (*cp == '\0') goto check_shell; /* * collect the shell argument. everything after the shell name * is passed as ONE argument; that's the correct (historical) * behaviour. */ shellarg = cp; for ( /* cp = cp */ ; *cp != '\0'; cp++) shellarglen++; *cp++ = '\0'; check_shell: /* * MNT_NOSUID and STRC are already taken care of by check_exec, * so we don't need to worry about them now or later. */ script_sbits = epp->ep_vap->va_mode & (VSUID | VSGID); if (script_sbits != 0) { script_uid = epp->ep_vap->va_uid; script_gid = epp->ep_vap->va_gid; } /* * if the script isn't readable, or it's set-id, then we've * gotta supply a "/dev/fd/..." for the shell to read. * Note that stupid shells (csh) do the wrong thing, and * close all open fd's when they start. That kills this * method of implementing "safe" set-id and x-only scripts. */ vn_lock(scriptvp, LK_EXCLUSIVE|LK_RETRY); error = VOP_ACCESS(scriptvp, VREAD, p->p_ucred, p); VOP_UNLOCK(scriptvp); if (error == EACCES || script_sbits) { struct file *fp; #ifdef DIAGNOSTIC if (epp->ep_flags & EXEC_HASFD) panic("exec_script_makecmds: epp already has a fd"); #endif fdplock(p->p_fd); error = falloc(p, &fp, &epp->ep_fd); if (error) { fdpunlock(p->p_fd); goto fail; } epp->ep_flags |= EXEC_HASFD; fp->f_type = DTYPE_VNODE; fp->f_ops = &vnops; fp->f_data = (caddr_t) scriptvp; fp->f_flag = FREAD; fdinsert(p->p_fd, epp->ep_fd, 0, fp); fdpunlock(p->p_fd); FRELE(fp, p); } /* set up the parameters for the recursive check_exec() call */ epp->ep_ndp->ni_dirfd = AT_FDCWD; epp->ep_ndp->ni_dirp = shellname; epp->ep_ndp->ni_segflg = UIO_SYSSPACE; epp->ep_flags |= EXEC_INDIR; /* and set up the fake args list, for later */ shellargp = mallocarray(4, sizeof(char *), M_EXEC, M_WAITOK); tmpsap = shellargp; *tmpsap = malloc(shellnamelen + 1, M_EXEC, M_WAITOK); strlcpy(*tmpsap++, shellname, shellnamelen + 1); if (shellarg != NULL) { *tmpsap = malloc(shellarglen + 1, M_EXEC, M_WAITOK); strlcpy(*tmpsap++, shellarg, shellarglen + 1); } *tmpsap = malloc(MAXPATHLEN, M_EXEC, M_WAITOK); if ((epp->ep_flags & EXEC_HASFD) == 0) { error = copyinstr(epp->ep_name, *tmpsap, MAXPATHLEN, NULL); if (error != 0) { *(tmpsap + 1) = NULL; goto fail; } } else snprintf(*tmpsap, MAXPATHLEN, "/dev/fd/%d", epp->ep_fd); tmpsap++; *tmpsap = NULL; /* * mark the header we have as invalid; check_exec will read * the header from the new executable */ epp->ep_hdrvalid = 0; if ((error = check_exec(p, epp)) == 0) { /* note that we've clobbered the header */ epp->ep_flags |= EXEC_DESTR; /* * It succeeded. Unlock the script and * close it if we aren't using it any more. * Also, set things up so that the fake args * list will be used. */ if ((epp->ep_flags & EXEC_HASFD) == 0) vn_close(scriptvp, FREAD, p->p_ucred, p); /* free the old pathname buffer */ pool_put(&namei_pool, oldpnbuf); epp->ep_flags |= (EXEC_HASARGL | EXEC_SKIPARG); epp->ep_fa = shellargp; /* * set things up so that set-id scripts will be * handled appropriately */ epp->ep_vap->va_mode |= script_sbits; if (script_sbits & VSUID) epp->ep_vap->va_uid = script_uid; if (script_sbits & VSGID) epp->ep_vap->va_gid = script_gid; return (0); } /* XXX oldpnbuf not set for "goto fail" path */ epp->ep_ndp->ni_cnd.cn_pnbuf = oldpnbuf; fail: /* note that we've clobbered the header */ epp->ep_flags |= EXEC_DESTR; /* kill the opened file descriptor, else close the file */ if (epp->ep_flags & EXEC_HASFD) { epp->ep_flags &= ~EXEC_HASFD; fdplock(p->p_fd); /* fdrelease() unlocks p->p_fd. */ (void) fdrelease(p, epp->ep_fd); } else vn_close(scriptvp, FREAD, p->p_ucred, p); pool_put(&namei_pool, epp->ep_ndp->ni_cnd.cn_pnbuf); /* free the fake arg list, because we're not returning it */ if (shellargp != NULL) { free(shellargp[0], M_EXEC, shellnamelen + 1); if (shellargp[2] != NULL) { free(shellargp[1], M_EXEC, shellarglen + 1); free(shellargp[2], M_EXEC, MAXPATHLEN); } else free(shellargp[1], M_EXEC, MAXPATHLEN); free(shellargp, M_EXEC, 4 * sizeof(char *)); } /* * free any vmspace-creation commands, * and release their references */ kill_vmcmds(&epp->ep_vmcmds); return error; }
