1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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/types.h>
36#include <sys/stat.h>
37#include <signal.h>
38#include <string.h>
39#include <fcntl.h>
40#include <errno.h>
41#include <unistd.h>
42#include <stdlib.h>
43
44/*
45 * Code for dealing with input/output redirection.
46 */
47
48#include "shell.h"
49#include "nodes.h"
50#include "jobs.h"
51#include "expand.h"
52#include "redir.h"
53#include "output.h"
54#include "memalloc.h"
55#include "error.h"
56#include "options.h"
57
58
59#define EMPTY -2		/* marks an unused slot in redirtab */
60#define CLOSED -1		/* fd was not open before redir */
61
62
63struct redirtab {
64	struct redirtab *next;
65	int renamed[10];
66	int fd0_redirected;
67	unsigned int empty_redirs;
68};
69
70
71static struct redirtab *redirlist;
72
73/*
74 * We keep track of whether or not fd0 has been redirected.  This is for
75 * background commands, where we want to redirect fd0 to /dev/null only
76 * if it hasn't already been redirected.
77*/
78static int fd0_redirected = 0;
79
80/* Number of redirtabs that have not been allocated. */
81static unsigned int empty_redirs = 0;
82
83static void openredirect(union node *, char[10 ]);
84static int openhere(union node *);
85
86
87/*
88 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
89 * old file descriptors are stashed away so that the redirection can be
90 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
91 * standard output, and the standard error if it becomes a duplicate of
92 * stdout, is saved in memory.
93*
94 * We suppress interrupts so that we won't leave open file
95 * descriptors around.  Because the signal handler remains
96 * installed and we do not use system call restart, interrupts
97 * will still abort blocking opens such as fifos (they will fail
98 * with EINTR). There is, however, a race condition if an interrupt
99 * arrives after INTOFF and before open blocks.
100 */
101
102void
103redirect(union node *redir, int flags)
104{
105	union node *n;
106	struct redirtab *sv = NULL;
107	int i;
108	int fd;
109	char memory[10];	/* file descriptors to write to memory */
110
111	INTOFF;
112	for (i = 10 ; --i >= 0 ; )
113		memory[i] = 0;
114	memory[1] = flags & REDIR_BACKQ;
115	if (flags & REDIR_PUSH) {
116		empty_redirs++;
117		if (redir != NULL) {
118			sv = ckmalloc(sizeof (struct redirtab));
119			for (i = 0 ; i < 10 ; i++)
120				sv->renamed[i] = EMPTY;
121			sv->fd0_redirected = fd0_redirected;
122			sv->empty_redirs = empty_redirs - 1;
123			sv->next = redirlist;
124			redirlist = sv;
125			empty_redirs = 0;
126		}
127	}
128	for (n = redir ; n ; n = n->nfile.next) {
129		fd = n->nfile.fd;
130		if (fd == 0)
131			fd0_redirected = 1;
132		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
133		    n->ndup.dupfd == fd)
134			continue; /* redirect from/to same file descriptor */
135
136		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
137			INTOFF;
138			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
139				switch (errno) {
140				case EBADF:
141					i = CLOSED;
142					break;
143				default:
144					INTON;
145					error("%d: %s", fd, strerror(errno));
146					break;
147				}
148			}
149			sv->renamed[fd] = i;
150			INTON;
151		}
152		openredirect(n, memory);
153		INTON;
154		INTOFF;
155	}
156	if (memory[1])
157		out1 = &memout;
158	if (memory[2])
159		out2 = &memout;
160	INTON;
161}
162
163
164static void
165openredirect(union node *redir, char memory[10])
166{
167	struct stat sb;
168	int fd = redir->nfile.fd;
169	const char *fname;
170	int f;
171	int e;
172
173	memory[fd] = 0;
174	switch (redir->nfile.type) {
175	case NFROM:
176		fname = redir->nfile.expfname;
177		if ((f = open(fname, O_RDONLY)) < 0)
178			error("cannot open %s: %s", fname, strerror(errno));
179		break;
180	case NFROMTO:
181		fname = redir->nfile.expfname;
182		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
183			error("cannot create %s: %s", fname, strerror(errno));
184		break;
185	case NTO:
186		if (Cflag) {
187			fname = redir->nfile.expfname;
188			if (stat(fname, &sb) == -1) {
189				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
190					error("cannot create %s: %s", fname, strerror(errno));
191			} else if (!S_ISREG(sb.st_mode)) {
192				if ((f = open(fname, O_WRONLY, 0666)) < 0)
193					error("cannot create %s: %s", fname, strerror(errno));
194				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
195					close(f);
196					error("cannot create %s: %s", fname,
197					    strerror(EEXIST));
198				}
199			} else
200				error("cannot create %s: %s", fname,
201				    strerror(EEXIST));
202			break;
203		}
204		/* FALLTHROUGH */
205	case NCLOBBER:
206		fname = redir->nfile.expfname;
207		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
208			error("cannot create %s: %s", fname, strerror(errno));
209		break;
210	case NAPPEND:
211		fname = redir->nfile.expfname;
212		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
213			error("cannot create %s: %s", fname, strerror(errno));
214		break;
215	case NTOFD:
216	case NFROMFD:
217		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
218			if (memory[redir->ndup.dupfd])
219				memory[fd] = 1;
220			else {
221				if (dup2(redir->ndup.dupfd, fd) < 0)
222					error("%d: %s", redir->ndup.dupfd,
223							strerror(errno));
224			}
225		} else {
226			close(fd);
227		}
228		return;
229	case NHERE:
230	case NXHERE:
231		f = openhere(redir);
232		break;
233	default:
234		abort();
235	}
236	if (f != fd) {
237		if (dup2(f, fd) == -1) {
238			e = errno;
239			close(f);
240			error("%d: %s", fd, strerror(e));
241		}
242		close(f);
243	}
244}
245
246
247/*
248 * Handle here documents.  Normally we fork off a process to write the
249 * data to a pipe.  If the document is short, we can stuff the data in
250 * the pipe without forking.
251 */
252
253static int
254openhere(union node *redir)
255{
256	const char *p;
257	int pip[2];
258	size_t len = 0;
259	int flags;
260	ssize_t written = 0;
261
262	if (pipe(pip) < 0)
263		error("Pipe call failed: %s", strerror(errno));
264
265	if (redir->type == NXHERE)
266		p = redir->nhere.expdoc;
267	else
268		p = redir->nhere.doc->narg.text;
269	len = strlen(p);
270	if (len == 0)
271		goto out;
272	flags = fcntl(pip[1], F_GETFL, 0);
273	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
274		written = write(pip[1], p, len);
275		if (written < 0)
276			written = 0;
277		if ((size_t)written == len)
278			goto out;
279		fcntl(pip[1], F_SETFL, flags);
280	}
281
282	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
283		close(pip[0]);
284		signal(SIGINT, SIG_IGN);
285		signal(SIGQUIT, SIG_IGN);
286		signal(SIGHUP, SIG_IGN);
287		signal(SIGTSTP, SIG_IGN);
288		signal(SIGPIPE, SIG_DFL);
289		xwrite(pip[1], p + written, len - written);
290		_exit(0);
291	}
292out:
293	close(pip[1]);
294	return pip[0];
295}
296
297
298
299/*
300 * Undo the effects of the last redirection.
301 */
302
303void
304popredir(void)
305{
306	struct redirtab *rp = redirlist;
307	int i;
308
309	INTOFF;
310	if (empty_redirs > 0) {
311		empty_redirs--;
312		INTON;
313		return;
314	}
315	for (i = 0 ; i < 10 ; i++) {
316		if (rp->renamed[i] != EMPTY) {
317			if (rp->renamed[i] >= 0) {
318				dup2(rp->renamed[i], i);
319				close(rp->renamed[i]);
320			} else {
321				close(i);
322			}
323		}
324	}
325	fd0_redirected = rp->fd0_redirected;
326	empty_redirs = rp->empty_redirs;
327	redirlist = rp->next;
328	ckfree(rp);
329	INTON;
330}
331
332/* Return true if fd 0 has already been redirected at least once.  */
333int
334fd0_redirected_p(void)
335{
336        return fd0_redirected != 0;
337}
338
339/*
340 * Discard all saved file descriptors.
341 */
342
343void
344clearredir(void)
345{
346	struct redirtab *rp;
347	int i;
348
349	for (rp = redirlist ; rp ; rp = rp->next) {
350		for (i = 0 ; i < 10 ; i++) {
351			if (rp->renamed[i] >= 0) {
352				close(rp->renamed[i]);
353			}
354			rp->renamed[i] = EMPTY;
355		}
356	}
357}
358