/*      $OpenBSD: popen.c,v 1.40 2023/03/08 04:43:11 guenther Exp $     */
/*      $NetBSD: popen.c,v 1.6 1997/05/13 06:48:42 mikel Exp $  */

/*
 * Copyright (c) 1980, 1993
 *      The Regents of the University of California.  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. 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 "rcv.h"
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <stdarg.h>
#include "extern.h"

#define READ 0
#define WRITE 1

struct fp {
        FILE *fp;
        int pipe;
        pid_t pid;
        struct fp *link;
};
static struct fp *fp_head;

struct child {
        pid_t pid;
        char done;
        char free;
        int status;
        struct child *link;
};
static struct child *child, *child_freelist = NULL;

static struct child *findchild(pid_t, int);
static void delchild(struct child *);
static pid_t file_pid(FILE *);
static int handle_spool_locks(int);

FILE *
Fopen(char *file, char *mode)
{
        FILE *fp;

        if ((fp = fopen(file, mode)) != NULL) {
                register_file(fp, 0, 0);
                (void)fcntl(fileno(fp), F_SETFD, FD_CLOEXEC);
        }
        return(fp);
}

FILE *
Fdopen(int fd, char *mode)
{
        FILE *fp;

        if ((fp = fdopen(fd, mode)) != NULL) {
                register_file(fp, 0, 0);
                (void)fcntl(fileno(fp), F_SETFD, FD_CLOEXEC);
        }
        return(fp);
}

int
Fclose(FILE *fp)
{

        unregister_file(fp);
        return(fclose(fp));
}

FILE *
Popen(char *cmd, char *mode)
{
        int p[2];
        int myside, hisside, fd0, fd1;
        pid_t pid;
        sigset_t nset;
        FILE *fp;

        if (pipe(p) == -1)
                return(NULL);
        (void)fcntl(p[READ], F_SETFD, FD_CLOEXEC);
        (void)fcntl(p[WRITE], F_SETFD, FD_CLOEXEC);
        if (*mode == 'r') {
                myside = p[READ];
                hisside = fd0 = fd1 = p[WRITE];
        } else {
                myside = p[WRITE];
                hisside = fd0 = p[READ];
                fd1 = -1;
        }
        sigemptyset(&nset);
        pid = start_command(value("SHELL"), &nset, fd0, fd1, "-c", cmd, NULL);
        if (pid < 0) {
                (void)close(p[READ]);
                (void)close(p[WRITE]);
                return(NULL);
        }
        (void)close(hisside);
        if ((fp = fdopen(myside, mode)) != NULL)
                register_file(fp, 1, pid);
        return(fp);
}

int
Pclose(FILE *ptr)
{
        int i;
        sigset_t nset, oset;

        i = file_pid(ptr);
        unregister_file(ptr);
        (void)fclose(ptr);
        sigemptyset(&nset);
        sigaddset(&nset, SIGINT);
        sigaddset(&nset, SIGHUP);
        sigprocmask(SIG_BLOCK, &nset, &oset);
        i = wait_child(i);
        sigprocmask(SIG_SETMASK, &oset, NULL);
        return(i);
}

void
close_all_files(void)
{

        while (fp_head)
                if (fp_head->pipe)
                        (void)Pclose(fp_head->fp);
                else
                        (void)Fclose(fp_head->fp);
}

void
register_file(FILE *fp, int pipe, pid_t pid)
{
        struct fp *fpp;

        if ((fpp = malloc(sizeof(*fpp))) == NULL)
                err(1, "malloc");
        fpp->fp = fp;
        fpp->pipe = pipe;
        fpp->pid = pid;
        fpp->link = fp_head;
        fp_head = fpp;
}

void
unregister_file(FILE *fp)
{
        struct fp **pp, *p;

        for (pp = &fp_head; (p = *pp) != NULL; pp = &p->link)
                if (p->fp == fp) {
                        *pp = p->link;
                        (void)free(p);
                        return;
                }
        errx(1, "Invalid file pointer");
}

static pid_t
file_pid(FILE *fp)
{
        struct fp *p;

        for (p = fp_head; p; p = p->link)
                if (p->fp == fp)
                        return(p->pid);
        errx(1, "Invalid file pointer");
        /*NOTREACHED*/
}

/*
 * Run a command without a shell, with optional arguments and splicing
 * of stdin (-1 means none) and stdout.  The command name can be a sequence
 * of words.
 * Signals must be handled by the caller.
 * "nset" contains the signals to ignore in the new process.
 * SIGINT is enabled unless it's in "nset".
 */
pid_t
start_commandv(char *cmd, sigset_t *nset, int infd, int outfd, va_list args)
{
        pid_t pid;

        if ((pid = fork()) == -1) {
                warn("fork");
                return(-1);
        }
        if (pid == 0) {
                char *argv[100];
                int i = getrawlist(cmd, argv, sizeof(argv)/ sizeof(*argv));

                while ((argv[i++] = va_arg(args, char *)))
                        ;
                argv[i] = NULL;
                prepare_child(nset, infd, outfd);
                execvp(argv[0], argv);
                warn("%s", argv[0]);
                _exit(1);
        }
        return(pid);
}

int
run_command(char *cmd, sigset_t *nset, int infd, int outfd, ...)
{
        pid_t pid;
        va_list args;

        va_start(args, outfd);
        pid = start_commandv(cmd, nset, infd, outfd, args);
        va_end(args);
        if (pid < 0)
                return(-1);
        return(wait_command(pid));
}

int
start_command(char *cmd, sigset_t *nset, int infd, int outfd, ...)
{
        va_list args;
        int r;

        va_start(args, outfd);
        r = start_commandv(cmd, nset, infd, outfd, args);
        va_end(args);
        return(r);
}

void
prepare_child(sigset_t *nset, int infd, int outfd)
{
        int i;
        sigset_t eset;

        /*
         * All file descriptors other than 0, 1, and 2 are supposed to be
         * close-on-exec.
         */
        if (infd > 0) {
                dup2(infd, 0);
        } else if (infd != 0) {
                /* we don't want the child stealing my stdin input */
                close(0);
                open(_PATH_DEVNULL, O_RDONLY, 0);
        }
        if (outfd >= 0 && outfd != 1)
                dup2(outfd, 1);
        if (nset == NULL)
                return;
        if (nset != NULL) {
                for (i = 1; i < NSIG; i++)
                        if (sigismember(nset, i))
                                (void)signal(i, SIG_IGN);
        }
        if (nset == NULL || !sigismember(nset, SIGINT))
                (void)signal(SIGINT, SIG_DFL);
        sigemptyset(&eset);
        (void)sigprocmask(SIG_SETMASK, &eset, NULL);
}

int
wait_command(pid_t pid)
{

        if (wait_child(pid) < 0) {
                puts("Fatal error in process.");
                return(-1);
        }
        return(0);
}

static struct child *
findchild(pid_t pid, int dont_alloc)
{
        struct child **cpp;

        for (cpp = &child; *cpp != NULL && (*cpp)->pid != pid;
             cpp = &(*cpp)->link)
                        ;
        if (*cpp == NULL) {
                if (dont_alloc)
                        return(NULL);
                if (child_freelist) {
                        *cpp = child_freelist;
                        child_freelist = (*cpp)->link;
                } else {
                        *cpp = malloc(sizeof(struct child));
                        if (*cpp == NULL)
                                err(1, "malloc");
                }
                (*cpp)->pid = pid;
                (*cpp)->done = (*cpp)->free = 0;
                (*cpp)->link = NULL;
        }
        return(*cpp);
}

static void
delchild(struct child *cp)
{
        struct child **cpp;

        for (cpp = &child; *cpp != cp; cpp = &(*cpp)->link)
                ;
        *cpp = cp->link;
        cp->link = child_freelist;
        child_freelist = cp;
}

void
sigchild(int signo)
{
        pid_t pid;
        int status;
        struct child *cp;
        int save_errno = errno;

        while ((pid = waitpid((pid_t)-1, &status, WNOHANG)) > 0) {
                cp = findchild(pid, 1);
                if (!cp)
                        continue;
                if (cp->free)
                        delchild(cp);
                else {
                        cp->done = 1;
                        cp->status = status;
                }
        }
        errno = save_errno;
}

int wait_status;

/*
 * Wait for a specific child to die.
 */
int
wait_child(pid_t pid)
{
        struct child *cp;
        sigset_t nset, oset;
        pid_t rv = 0;

        sigemptyset(&nset);
        sigaddset(&nset, SIGCHLD);
        sigprocmask(SIG_BLOCK, &nset, &oset);
        /*
         * If we have not already waited on the pid (via sigchild)
         * wait on it now.  Otherwise, use the wait status stashed
         * by sigchild.
         */
        cp = findchild(pid, 1);
        if (cp == NULL || !cp->done)
                rv = waitpid(pid, &wait_status, 0);
        else
                wait_status = cp->status;
        if (cp != NULL)
                delchild(cp);
        sigprocmask(SIG_SETMASK, &oset, NULL);
        if (rv == -1 || (WIFEXITED(wait_status) && WEXITSTATUS(wait_status)))
                return(-1);
        else
                return(0);
}

/*
 * Mark a child as don't care.
 */
void
free_child(pid_t pid)
{
        struct child *cp;
        sigset_t nset, oset;

        sigemptyset(&nset);
        sigaddset(&nset, SIGCHLD);
        sigprocmask(SIG_BLOCK, &nset, &oset);
        if ((cp = findchild(pid, 0)) != NULL) {
                if (cp->done)
                        delchild(cp);
                else
                        cp->free = 1;
        }
        sigprocmask(SIG_SETMASK, &oset, NULL);
}

/*
 * Lock(1)/unlock(0) mail spool using lockspool(1).
 * Returns 1 for success, 0 for failure, -1 for bad usage.
 */
static int
handle_spool_locks(int action)
{
        static FILE *lockfp = NULL;

        if (action == 0) {
                /* Clear the lock */
                if (lockfp == NULL) {
                        fputs("handle_spool_locks: no spool lock to remove.\n",
                            stderr);
                        return(-1);
                }
                (void)Pclose(lockfp);
                lockfp = NULL;
        } else if (action == 1) {
                char *cmd;
                char buf[sizeof(_PATH_LOCKSPOOL) + LOGIN_NAME_MAX + 1];

                /* XXX - lockspool requires root for user arg, we do not */
                if (uflag) {
                        snprintf(buf, sizeof(buf), "%s %s", _PATH_LOCKSPOOL,
                            myname);
                        cmd = buf;
                } else
                        cmd = _PATH_LOCKSPOOL;

                /* Create the lock */
                lockfp = Popen(cmd, "r");
                if (lockfp == NULL)
                        return(0);
                if (getc(lockfp) != '1') {
                        Pclose(lockfp);
                        lockfp = NULL;
                        return(0);
                }
        } else {
                (void)fprintf(stderr, "handle_spool_locks: unknown action %d\n",
                    action);
                return(-1);
        }

        return(1);
}

int
spool_lock(void)
{

        return(handle_spool_locks(1));
}

int
spool_unlock(void)
{

        return(handle_spool_locks(0));
}