common/path/pathshell.c

da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin/***********************************************************************
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                                                                      *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*               This software is part of the ast package               *
3e14f97f673e8a630f076077de35afdd43dc1587Roger A. Faulkner*          Copyright (c) 1985-2010 AT&T Intellectual Property          *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                      and is licensed under the                       *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                  Common Public License, Version 1.0                  *
7c2fbfb345896881c631598ee3852ce9ce33fb07April Chin*                    by AT&T Intellectual Property                     *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                                                                      *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                A copy of the License is available at                 *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*            http://www.opensource.org/licenses/cpl1.0.txt             *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                                                                      *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*              Information and Software Systems Research               *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                            AT&T Research                             *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                           Florham Park NJ                            *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                                                                      *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                 Glenn Fowler <gsf@research.att.com>                  *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                  David Korn <dgk@research.att.com>                   *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                   Phong Vo <kpv@research.att.com>                    *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin*                                                                      *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin***********************************************************************/
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin#pragma prototyped
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin/*
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * G. S. Fowler
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * D. G. Korn
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * AT&T Bell Laboratories
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * shell library support
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin#include <ast.h>
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin#include <sys/stat.h>
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin/*
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * return pointer to the full path name of the shell
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * SHELL is read from the environment and must start with /
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * if set-uid or set-gid then the executable and its containing
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * directory must not be owned by the real user/group
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * root/administrator has its own test
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * astconf("SH",NiL,NiL) is returned by default
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin * NOTE: csh is rejected because the bsh/csh differentiation is
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin *       not done for `csh script arg ...'
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chinchar*
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chinpathshell(void)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin{
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    register char*  sh;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    int     ru;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    int     eu;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    int     rg;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    int     eg;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    struct stat st;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    static char*    val;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    if ((sh = getenv("SHELL")) && *sh == '/' && strmatch(sh, "*/(sh|*[!cC]sh)*([[:digit:]])?(-+([.[:alnum:]]))?(.exe)"))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        if (!(ru = getuid()) || !eaccess("/bin", W_OK))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            if (stat(sh, &st))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            if (ru != st.st_uid && !strmatch(sh, "?(/usr)?(/local)/?([ls])bin/?([[:lower:]])sh?(.exe)"))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        else
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            eu = geteuid();
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            rg = getgid();
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            eg = getegid();
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            if (ru != eu || rg != eg)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                char*   s;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                char    dir[PATH_MAX];
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                s = sh;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                for (;;)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (stat(s, &st))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (ru != eu && st.st_uid == ru)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (rg != eg && st.st_gid == rg)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (s != sh)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        break;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (strlen(s) >= sizeof(dir))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        goto defshell;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    strcpy(dir, s);
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    if (!(s = strrchr(dir, '/')))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                        break;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    *s = 0;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                    s = dir;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin                }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        return sh;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin defshell:
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    if (!(sh = val))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    {
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        if (!*(sh = astconf("SH", NiL, NiL)) || *sh != '/' || eaccess(sh, X_OK) || !(sh = strdup(sh)))
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin            sh = "/bin/sh";
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin        val = sh;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    }
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin    return sh;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin}