/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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/types.h>
#include <sys/stat.h>
#include <signal.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

/*
 * Code for dealing with input/output redirection.
 */

#include "shell.h"
#include "nodes.h"
#include "jobs.h"
#include "expand.h"
#include "redir.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "options.h"


#define EMPTY -2                /* marks an unused slot in redirtab */
#define CLOSED -1               /* fd was not open before redir */


struct redirtab {
        struct redirtab *next;
        int renamed[10];
        int fd0_redirected;
        unsigned int empty_redirs;
};


static struct redirtab *redirlist;

/*
 * We keep track of whether or not fd0 has been redirected.  This is for
 * background commands, where we want to redirect fd0 to /dev/null only
 * if it hasn't already been redirected.
*/
static int fd0_redirected = 0;

/* Number of redirtabs that have not been allocated. */
static unsigned int empty_redirs = 0;

static void openredirect(union node *, char[10 ]);
static int openhere(union node *);


/*
 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
 * old file descriptors are stashed away so that the redirection can be
 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
 * standard output, and the standard error if it becomes a duplicate of
 * stdout, is saved in memory.
*
 * We suppress interrupts so that we won't leave open file
 * descriptors around.  Because the signal handler remains
 * installed and we do not use system call restart, interrupts
 * will still abort blocking opens such as fifos (they will fail
 * with EINTR). There is, however, a race condition if an interrupt
 * arrives after INTOFF and before open blocks.
 */

void
redirect(union node *redir, int flags)
{
        union node *n;
        struct redirtab *sv = NULL;
        int i;
        int fd;
        char memory[10];        /* file descriptors to write to memory */

        INTOFF;
        for (i = 10 ; --i >= 0 ; )
                memory[i] = 0;
        memory[1] = flags & REDIR_BACKQ;
        if (flags & REDIR_PUSH) {
                empty_redirs++;
                if (redir != NULL) {
                        sv = ckmalloc(sizeof (struct redirtab));
                        for (i = 0 ; i < 10 ; i++)
                                sv->renamed[i] = EMPTY;
                        sv->fd0_redirected = fd0_redirected;
                        sv->empty_redirs = empty_redirs - 1;
                        sv->next = redirlist;
                        redirlist = sv;
                        empty_redirs = 0;
                }
        }
        for (n = redir ; n ; n = n->nfile.next) {
                fd = n->nfile.fd;
                if (fd == 0)
                        fd0_redirected = 1;
                if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
                    n->ndup.dupfd == fd)
                        continue; /* redirect from/to same file descriptor */

                if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
                        INTOFF;
                        if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
                                switch (errno) {
                                case EBADF:
                                        i = CLOSED;
                                        break;
                                default:
                                        INTON;
                                        error("%d: %s", fd, strerror(errno));
                                        break;
                                }
                        }
                        sv->renamed[fd] = i;
                        INTON;
                }
                openredirect(n, memory);
                INTON;
                INTOFF;
        }
        if (memory[1])
                out1 = &memout;
        if (memory[2])
                out2 = &memout;
        INTON;
}


static void
openredirect(union node *redir, char memory[10])
{
        struct stat sb;
        int fd = redir->nfile.fd;
        const char *fname;
        int f;
        int e;

        memory[fd] = 0;
        switch (redir->nfile.type) {
        case NFROM:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_RDONLY)) < 0)
                        error("cannot open %s: %s", fname, strerror(errno));
                break;
        case NFROMTO:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
                        error("cannot create %s: %s", fname, strerror(errno));
                break;
        case NTO:
                if (Cflag) {
                        fname = redir->nfile.expfname;
                        if (stat(fname, &sb) == -1) {
                                if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
                                        error("cannot create %s: %s", fname, strerror(errno));
                        } else if (!S_ISREG(sb.st_mode)) {
                                if ((f = open(fname, O_WRONLY, 0666)) < 0)
                                        error("cannot create %s: %s", fname, strerror(errno));
                                if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
                                        close(f);
                                        error("cannot create %s: %s", fname,
                                            strerror(EEXIST));
                                }
                        } else
                                error("cannot create %s: %s", fname,
                                    strerror(EEXIST));
                        break;
                }
                /* FALLTHROUGH */
        case NCLOBBER:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
                        error("cannot create %s: %s", fname, strerror(errno));
                break;
        case NAPPEND:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
                        error("cannot create %s: %s", fname, strerror(errno));
                break;
        case NTOFD:
        case NFROMFD:
                if (redir->ndup.dupfd >= 0) {   /* if not ">&-" */
                        if (memory[redir->ndup.dupfd])
                                memory[fd] = 1;
                        else {
                                if (dup2(redir->ndup.dupfd, fd) < 0)
                                        error("%d: %s", redir->ndup.dupfd,
                                                        strerror(errno));
                        }
                } else {
                        close(fd);
                }
                return;
        case NHERE:
        case NXHERE:
                f = openhere(redir);
                break;
        default:
                abort();
        }
        if (f != fd) {
                if (dup2(f, fd) == -1) {
                        e = errno;
                        close(f);
                        error("%d: %s", fd, strerror(e));
                }
                close(f);
        }
}


/*
 * Handle here documents.  Normally we fork off a process to write the
 * data to a pipe.  If the document is short, we can stuff the data in
 * the pipe without forking.
 */

static int
openhere(union node *redir)
{
        const char *p;
        int pip[2];
        size_t len = 0;
        int flags;
        ssize_t written = 0;

        if (pipe(pip) < 0)
                error("Pipe call failed: %s", strerror(errno));

        if (redir->type == NXHERE)
                p = redir->nhere.expdoc;
        else
                p = redir->nhere.doc->narg.text;
        len = strlen(p);
        if (len == 0)
                goto out;
        flags = fcntl(pip[1], F_GETFL, 0);
        if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
                written = write(pip[1], p, len);
                if (written < 0)
                        written = 0;
                if ((size_t)written == len)
                        goto out;
                fcntl(pip[1], F_SETFL, flags);
        }

        if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
                close(pip[0]);
                signal(SIGINT, SIG_IGN);
                signal(SIGQUIT, SIG_IGN);
                signal(SIGHUP, SIG_IGN);
                signal(SIGTSTP, SIG_IGN);
                signal(SIGPIPE, SIG_DFL);
                xwrite(pip[1], p + written, len - written);
                _exit(0);
        }
out:
        close(pip[1]);
        return pip[0];
}



/*
 * Undo the effects of the last redirection.
 */

void
popredir(void)
{
        struct redirtab *rp = redirlist;
        int i;

        INTOFF;
        if (empty_redirs > 0) {
                empty_redirs--;
                INTON;
                return;
        }
        for (i = 0 ; i < 10 ; i++) {
                if (rp->renamed[i] != EMPTY) {
                        if (rp->renamed[i] >= 0) {
                                dup2(rp->renamed[i], i);
                                close(rp->renamed[i]);
                        } else {
                                close(i);
                        }
                }
        }
        fd0_redirected = rp->fd0_redirected;
        empty_redirs = rp->empty_redirs;
        redirlist = rp->next;
        ckfree(rp);
        INTON;
}

/* Return true if fd 0 has already been redirected at least once.  */
int
fd0_redirected_p(void)
{
        return fd0_redirected != 0;
}

/*
 * Discard all saved file descriptors.
 */

void
clearredir(void)
{
        struct redirtab *rp;
        int i;

        for (rp = redirlist ; rp ; rp = rp->next) {
                for (i = 0 ; i < 10 ; i++) {
                        if (rp->renamed[i] >= 0) {
                                close(rp->renamed[i]);
                        }
                        rp->renamed[i] = EMPTY;
                }
        }
}