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      1 /*	$NetBSD: main.c,v 1.90 2023/04/07 10:34:13 kre Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Kenneth Almquist.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 __COPYRIGHT("@(#) Copyright (c) 1991, 1993\
     38  The Regents of the University of California.  All rights reserved.");
     39 #endif /* not lint */
     40 
     41 #ifndef lint
     42 #if 0
     43 static char sccsid[] = "@(#)main.c	8.7 (Berkeley) 7/19/95";
     44 #else
     45 __RCSID("$NetBSD: main.c,v 1.90 2023/04/07 10:34:13 kre Exp $");
     46 #endif
     47 #endif /* not lint */
     48 
     49 #include <errno.h>
     50 #include <stdio.h>
     51 #include <signal.h>
     52 #include <sys/stat.h>
     53 #include <unistd.h>
     54 #include <stdbool.h>
     55 #include <stdlib.h>
     56 #include <locale.h>
     57 #include <fcntl.h>
     58 
     59 
     60 #include "shell.h"
     61 #include "main.h"
     62 #include "mail.h"
     63 #include "options.h"
     64 #include "builtins.h"
     65 #include "output.h"
     66 #include "parser.h"
     67 #include "nodes.h"
     68 #include "expand.h"
     69 #include "eval.h"
     70 #include "jobs.h"
     71 #include "input.h"
     72 #include "trap.h"
     73 #include "var.h"
     74 #include "show.h"
     75 #include "memalloc.h"
     76 #include "error.h"
     77 #include "init.h"
     78 #include "mystring.h"
     79 #include "exec.h"
     80 #include "cd.h"
     81 #include "redir.h"
     82 
     83 #define PROFILE 0
     84 
     85 int rootpid;
     86 int rootshell;
     87 struct jmploc main_handler;
     88 int max_user_fd;
     89 long user_fd_limit;
     90 bool privileged;
     91 #if PROFILE
     92 short profile_buf[16384];
     93 extern int etext();
     94 #endif
     95 
     96 STATIC void read_profile(const char *);
     97 
     98 /*
     99  * Main routine.  We initialize things, parse the arguments, execute
    100  * profiles if we're a login shell, and then call cmdloop to execute
    101  * commands.  The setjmp call sets up the location to jump to when an
    102  * exception occurs.  When an exception occurs the variable "state"
    103  * is used to figure out how far we had gotten.
    104  */
    105 
    106 int
    107 main(int argc, char **argv)
    108 {
    109 	struct stackmark smark;
    110 	volatile int state;
    111 	char *shinit;
    112 	uid_t uid;
    113 	gid_t gid;
    114 	sigset_t mask;
    115 	bool waspriv;
    116 
    117 	/*
    118 	 * If we happen to be invoked with SIGCHLD ignored, we cannot
    119 	 * successfully do almost anything.   Perhaps we should remember
    120 	 * its state and pass it on ignored to children if it was ignored
    121 	 * on entry, but that seems like just leaving the shit on the
    122 	 * footpath for someone else to fall into...
    123 	 */
    124 	(void)signal(SIGCHLD, SIG_DFL);
    125 	/*
    126 	 * Similarly, SIGCHLD must not be blocked
    127 	 */
    128 	sigemptyset(&mask);
    129 	sigaddset(&mask, SIGCHLD);
    130 	sigprocmask(SIG_UNBLOCK, &mask, NULL);
    131 
    132 	uid = getuid();
    133 	gid = getgid();
    134 
    135 	waspriv = privileged = (uid != geteuid()) || (gid != getegid());
    136 
    137 	max_user_fd = fcntl(0, F_MAXFD);
    138 	if (max_user_fd < 2)
    139 		max_user_fd = 2;
    140 	user_fd_limit = sysconf(_SC_OPEN_MAX);
    141 
    142 	setlocale(LC_ALL, "");
    143 
    144 	posix = getenv("POSIXLY_CORRECT") != NULL;
    145 #if PROFILE
    146 	monitor(4, etext, profile_buf, sizeof profile_buf, 50);
    147 #endif
    148 	state = 0;
    149 	if (setjmp(main_handler.loc)) {
    150 		/*
    151 		 * When a shell procedure is executed, we raise the
    152 		 * exception EXSHELLPROC to clean up before executing
    153 		 * the shell procedure.
    154 		 */
    155 		switch (exception) {
    156 		case EXSHELLPROC:
    157 			rootpid = getpid();
    158 			rootshell = 1;
    159 			minusc = NULL;
    160 			state = 3;
    161 			break;
    162 
    163 		case EXEXEC:
    164 			exitstatus = exerrno;
    165 			break;
    166 
    167 		case EXERROR:
    168 			exitstatus = 2;
    169 			break;
    170 
    171 		default:
    172 			break;
    173 		}
    174 
    175 		if (exception != EXSHELLPROC) {
    176 			if (state == 0 || iflag == 0 || ! rootshell ||
    177 			    exception == EXEXIT)
    178 				exitshell(exitstatus);
    179 		}
    180 		reset();
    181 		if (exception == EXINT) {
    182 			out2c('\n');
    183 			flushout(&errout);
    184 		}
    185 		popstackmark(&smark);
    186 		FORCEINTON;				/* enable interrupts */
    187 		if (state == 1)
    188 			goto state1;
    189 		else if (state == 2)
    190 			goto state2;
    191 		else if (state == 3)
    192 			goto state3;
    193 		else
    194 			goto state4;
    195 	}
    196 	handler = &main_handler;
    197 #ifdef DEBUG
    198 #if DEBUG >= 2
    199 	debug = 1;	/* this may be reset by procargs() later */
    200 #endif
    201 	opentrace();
    202 	if (privileged)
    203 		trputs("Privileged ");
    204 	trputs("Shell args:  ");  trargs(argv);
    205 #if DEBUG >= 3
    206 	set_debug(((DEBUG)==3 ? "_@" : "++"), 1);
    207 #endif
    208 #endif
    209 	rootpid = getpid();
    210 	rootshell = 1;
    211 	init();
    212 	initpwd();
    213 	setstackmark(&smark);
    214 	procargs(argc, argv);
    215 	setvar_invocation(argc, argv);
    216 
    217 #if 0	/* This now happens (indirectly) in the procargs() just above */
    218 	/*
    219 	 * Limit bogus system(3) or popen(3) calls in setuid binaries,
    220 	 * by requiring the -p flag
    221 	 */
    222 	if (!pflag && (uid != geteuid() || gid != getegid())) {
    223 		setuid(uid);
    224 		setgid(gid);
    225 		/* PS1 might need to be changed accordingly. */
    226 		choose_ps1();
    227 	}
    228 #else	/* except for this one little bit */
    229 	if (waspriv && !privileged)
    230 		choose_ps1();
    231 #endif
    232 
    233 	if (loginsh) {
    234 		state = 1;
    235 		read_profile("/etc/profile");
    236  state1:
    237 		state = 2;
    238 		if (!privileged) {
    239 			char *profile;
    240 			const char *home;
    241 
    242 			home = lookupvar("HOME");
    243 			if (home == NULL)
    244 				home = nullstr;
    245 			profile = ststrcat(NULL, home, "/.profile", STSTRC_END);
    246 			read_profile(profile);
    247 			stunalloc(profile);
    248 		}
    249 #if 0	/* FreeBSD does (effectively) ...*/
    250 		else
    251 			read_profile("/etc/suid_profile");
    252 #endif
    253 	}
    254  state2:
    255 	state = 3;
    256 	if ((iflag || !posix) && !privileged) {
    257 		struct stackmark env_smark;
    258 
    259 		setstackmark(&env_smark);
    260 		if ((shinit = lookupvar("ENV")) != NULL && *shinit != '\0') {
    261 			state = 3;
    262 			read_profile(expandenv(shinit));
    263 		}
    264 		popstackmark(&env_smark);
    265 	}
    266  state3:
    267 	state = 4;
    268 	line_number = 1;	/* undo anything from profile files */
    269 
    270 	if (sflag == 0 || minusc) {
    271 		static int sigs[] =  {
    272 		    SIGINT, SIGQUIT, SIGHUP,
    273 #ifdef SIGTSTP
    274 		    SIGTSTP,
    275 #endif
    276 		    SIGPIPE
    277 		};
    278 #define SIGSSIZE (sizeof(sigs)/sizeof(sigs[0]))
    279 		size_t i;
    280 
    281 		for (i = 0; i < SIGSSIZE; i++)
    282 		    setsignal(sigs[i], 0);
    283 	}
    284 
    285 	rststackmark(&smark);	/* this one is never popped */
    286 
    287 	if (minusc)
    288 		evalstring(minusc, sflag ? 0 : EV_EXIT);
    289 
    290 	if (sflag || minusc == NULL) {
    291  state4:	/* XXX ??? - why isn't this before the "if" statement */
    292 		cmdloop(1);
    293 		if (iflag) {
    294 			out2str("\n");
    295 			flushout(&errout);
    296 		}
    297 	}
    298 #if PROFILE
    299 	monitor(0);
    300 #endif
    301 	line_number = plinno;
    302 	exitshell(exitstatus);
    303 	/* NOTREACHED */
    304 }
    305 
    306 
    307 /*
    308  * Read and execute commands.  "Top" is nonzero for the top level command
    309  * loop; it turns on prompting if the shell is interactive.
    310  */
    311 
    312 void
    313 cmdloop(int top)
    314 {
    315 	union node *n;
    316 	struct stackmark smark;
    317 	int inter;
    318 	int numeof = 0;
    319 	enum skipstate skip;
    320 
    321 	CTRACE(DBG_ALWAYS, ("cmdloop(%d) called\n", top));
    322 	setstackmark(&smark);
    323 	for (;;) {
    324 		if (pendingsigs)
    325 			dotrap();
    326 		inter = 0;
    327 		if (iflag == 1 && top) {
    328 			inter = 1;
    329 			showjobs(out2, SHOW_CHANGED);
    330 			chkmail(0);
    331 			flushout(&errout);
    332 			nflag = 0;
    333 		}
    334 		n = parsecmd(inter);
    335 		VXTRACE(DBG_PARSE|DBG_EVAL|DBG_CMDS,("cmdloop: "),showtree(n));
    336 		if (n == NEOF) {
    337 			if (!top || numeof >= 50)
    338 				break;
    339 			if (nflag)
    340 				break;
    341 			if (!stoppedjobs()) {
    342 				if (!iflag || !Iflag)
    343 					break;
    344 				out2str("\nUse \"exit\" to leave shell.\n");
    345 			}
    346 			numeof++;
    347 		} else if (n != NULL && nflag == 0) {
    348 			job_warning = (job_warning == 2) ? 1 : 0;
    349 			numeof = 0;
    350 			evaltree(n, 0);
    351 		}
    352 		rststackmark(&smark);
    353 
    354 		/*
    355 		 * Any SKIP* can occur here!  SKIP(FUNC|BREAK|CONT) occur when
    356 		 * a dotcmd is in a loop or a function body and appropriate
    357 		 * built-ins occurs in file scope in the sourced file.  Values
    358 		 * other than SKIPFILE are reset by the appropriate eval*()
    359 		 * that contained the dotcmd() call.
    360 		 */
    361 		skip = current_skipstate();
    362 		if (skip != SKIPNONE) {
    363 			if (skip == SKIPFILE)
    364 				stop_skipping();
    365 			break;
    366 		}
    367 	}
    368 	popstackmark(&smark);
    369 }
    370 
    371 
    372 
    373 /*
    374  * Read /etc/profile or .profile.  Return on error.
    375  */
    376 
    377 STATIC void
    378 read_profile(const char *name)
    379 {
    380 	int fd;
    381 	int xflag_set = 0;
    382 	int vflag_set = 0;
    383 
    384 	if (*name == '\0')
    385 		return;
    386 
    387 	INTOFF;
    388 	if ((fd = open(name, O_RDONLY)) >= 0)
    389 		setinputfd(fd, 1);
    390 	INTON;
    391 	if (fd < 0)
    392 		return;
    393 	/* -q turns off -x and -v just when executing init files */
    394 	if (qflag)  {
    395 	    if (xflag)
    396 		    xflag = 0, xflag_set = 1;
    397 	    if (vflag)
    398 		    vflag = 0, vflag_set = 1;
    399 	}
    400 	(void)set_dot_funcnest(1);	/* allow profile to "return" */
    401 	cmdloop(0);
    402 	(void)set_dot_funcnest(0);
    403 	if (qflag)  {
    404 	    if (xflag_set)
    405 		    xflag = 1;
    406 	    if (vflag_set)
    407 		    vflag = 1;
    408 	}
    409 	popfile();
    410 }
    411 
    412 
    413 
    414 /*
    415  * Read a file containing shell functions.
    416  */
    417 
    418 void
    419 readcmdfile(char *name)
    420 {
    421 	int fd;
    422 
    423 	INTOFF;
    424 	if ((fd = open(name, O_RDONLY)) >= 0)
    425 		setinputfd(fd, 1);
    426 	else
    427 		error("Can't open %s", name);
    428 	INTON;
    429 	cmdloop(0);
    430 	popfile();
    431 }
    432 
    433 
    434 
    435 int
    436 exitcmd(int argc, char **argv)
    437 {
    438 	if (stoppedjobs())
    439 		return 0;
    440 	if (argc > 1)
    441 		exitshell(number(argv[1]));
    442 	else
    443 		exitshell_savedstatus();
    444 	/* NOTREACHED */
    445 }
    446