/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1983, 1988, 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 "namespace.h"
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <sys/time.h>
#include <sys/uio.h>
#include <sys/un.h>
#include <netdb.h>

#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <stdarg.h>
#include "un-namespace.h"

#include "libc_private.h"

/* Maximum number of characters of syslog message */
#define MAXLINE         8192

static int      LogFile = -1;           /* fd for log */
static bool     connected;              /* have done connect */
static int      opened;                 /* have done openlog() */
static int      LogStat = 0;            /* status bits, set by openlog() */
static pid_t    LogPid = -1;            /* process id to tag the entry with */
static const char *LogTag = NULL;       /* string to tag the entry with */
static int      LogTagLength = -1;      /* usable part of LogTag */
static int      LogFacility = LOG_USER; /* default facility code */
static int      LogMask = 0xff;         /* mask of priorities to be logged */
static pthread_mutex_t  syslog_mutex = PTHREAD_MUTEX_INITIALIZER;

#define THREAD_LOCK()                                                   \
        do {                                                            \
                if (__isthreaded) _pthread_mutex_lock(&syslog_mutex);   \
        } while(0)
#define THREAD_UNLOCK()                                                 \
        do {                                                            \
                if (__isthreaded) _pthread_mutex_unlock(&syslog_mutex); \
        } while(0)

/* RFC5424 defined value. */
#define NILVALUE "-"

static void     disconnectlog(void); /* disconnect from syslogd */
static void     connectlog(void);       /* (re)connect to syslogd */
static void     openlog_unlocked(const char *, int, int);
static void     parse_tag(void);        /* parse ident[NNN] if needed */

/*
 * Format of the magic cookie passed through the stdio hook
 */
struct bufcookie {
        char    *base;  /* start of buffer */
        int     left;
};

/*
 * stdio write hook for writing to a static string buffer
 * XXX: Maybe one day, dynamically allocate it so that the line length
 *      is `unlimited'.
 */
static int
writehook(void *cookie, const char *buf, int len)
{
        struct bufcookie *h;    /* private `handle' */

        h = (struct bufcookie *)cookie;
        if (len > h->left) {
                /* clip in case of wraparound */
                len = h->left;
        }
        if (len > 0) {
                (void)memcpy(h->base, buf, len); /* `write' it. */
                h->base += len;
                h->left -= len;
        }
        return len;
}

/*
 * syslog, vsyslog --
 *      print message on log file; output is intended for syslogd(8).
 */
void
syslog(int pri, const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        vsyslog(pri, fmt, ap);
        va_end(ap);
}

static void
vsyslog1(int pri, const char *fmt, va_list ap)
{
        struct timeval now;
        struct tm tm;
        char ch, *p;
        long tz_offset;
        int cnt, fd, saved_errno;
        char hostname[MAXHOSTNAMELEN], *stdp, tbuf[MAXLINE], fmt_cpy[MAXLINE],
            errstr[64], tz_sign;
        FILE *fp, *fmt_fp;
        struct bufcookie tbuf_cookie;
        struct bufcookie fmt_cookie;

#define INTERNALLOG     LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID
        /* Check for invalid bits. */
        if (pri & ~(LOG_PRIMASK|LOG_FACMASK)) {
                syslog(INTERNALLOG,
                    "syslog: unknown facility/priority: %x", pri);
                pri &= LOG_PRIMASK|LOG_FACMASK;
        }

        saved_errno = errno;

        /* Check priority against setlogmask values. */
        if (!(LOG_MASK(LOG_PRI(pri)) & LogMask))
                return;

        /* Set default facility if none specified. */
        if ((pri & LOG_FACMASK) == 0)
                pri |= LogFacility;

        /* Create the primary stdio hook */
        tbuf_cookie.base = tbuf;
        tbuf_cookie.left = sizeof(tbuf);
        fp = fwopen(&tbuf_cookie, writehook);
        if (fp == NULL)
                return;

        /* Build the message according to RFC 5424. Tag and version. */
        (void)fprintf(fp, "<%d>1 ", pri);
        /* Timestamp similar to RFC 3339. */
        if (gettimeofday(&now, NULL) == 0 &&
            localtime_r(&now.tv_sec, &tm) != NULL) {
                if (tm.tm_gmtoff < 0) {
                        tz_sign = '-';
                        tz_offset = -tm.tm_gmtoff;
                } else {
                        tz_sign = '+';
                        tz_offset = tm.tm_gmtoff;
                }

                (void)fprintf(fp,
                    "%04d-%02d-%02d"            /* Date. */
                    "T%02d:%02d:%02d.%06ld"     /* Time. */
                    "%c%02ld:%02ld ",           /* Time zone offset. */
                    tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
                    tm.tm_hour, tm.tm_min, tm.tm_sec, now.tv_usec,
                    tz_sign, tz_offset / 3600, (tz_offset % 3600) / 60);
        } else
                (void)fputs(NILVALUE " ", fp);
        /* Hostname. */
        (void)gethostname(hostname, sizeof(hostname));
        (void)fprintf(fp, "%s ",
            hostname[0] == '\0' ? NILVALUE : hostname);
        if (LogStat & LOG_PERROR) {
                /* Transfer to string buffer */
                (void)fflush(fp);
                stdp = tbuf + (sizeof(tbuf) - tbuf_cookie.left);
        }
        /* Application name. */
        if (LogTag == NULL)
                LogTag = _getprogname();
        else if (LogTagLength == -1)
                parse_tag();
        if (LogTagLength > 0)
                (void)fprintf(fp, "%.*s ", LogTagLength, LogTag);
        else
                (void)fprintf(fp, "%s ", LogTag == NULL ? NILVALUE : LogTag);
        /*
         * Provide the process ID regardless of whether LOG_PID has been
         * specified, as it provides valuable information. Many
         * applications tend not to use this, even though they should.
         */
        if (LogTagLength <= 0)
                LogPid = getpid();
        (void)fprintf(fp, "%d ", (int)LogPid);
        /* Message ID. */
        (void)fputs(NILVALUE " ", fp);
        /* Structured data. */
        (void)fputs(NILVALUE " ", fp);

        /* Check to see if we can skip expanding the %m */
        if (strstr(fmt, "%m")) {

                /* Create the second stdio hook */
                fmt_cookie.base = fmt_cpy;
                fmt_cookie.left = sizeof(fmt_cpy) - 1;
                fmt_fp = fwopen(&fmt_cookie, writehook);
                if (fmt_fp == NULL) {
                        fclose(fp);
                        return;
                }

                /*
                 * Substitute error message for %m.  Be careful not to
                 * molest an escaped percent "%%m".  We want to pass it
                 * on untouched as the format is later parsed by vfprintf.
                 */
                for ( ; (ch = *fmt); ++fmt) {
                        if (ch == '%' && fmt[1] == 'm') {
                                ++fmt;
                                strerror_r(saved_errno, errstr, sizeof(errstr));
                                fputs(errstr, fmt_fp);
                        } else if (ch == '%' && fmt[1] == '%') {
                                ++fmt;
                                fputc(ch, fmt_fp);
                                fputc(ch, fmt_fp);
                        } else {
                                fputc(ch, fmt_fp);
                        }
                }

                /* Null terminate if room */
                fputc(0, fmt_fp);
                fclose(fmt_fp);

                /* Guarantee null termination */
                fmt_cpy[sizeof(fmt_cpy) - 1] = '\0';

                fmt = fmt_cpy;
        }

        /* Message. */
        (void)vfprintf(fp, fmt, ap);
        (void)fclose(fp);

        cnt = sizeof(tbuf) - tbuf_cookie.left;

        /* Remove a trailing newline */
        if (tbuf[cnt - 1] == '\n')
                cnt--;

        /* Output to stderr if requested. */
        if (LogStat & LOG_PERROR) {
                struct iovec iov[2];
                struct iovec *v = iov;

                v->iov_base = stdp;
                v->iov_len = cnt - (stdp - tbuf);
                ++v;
                v->iov_base = "\n";
                v->iov_len = 1;
                (void)_writev(STDERR_FILENO, iov, 2);
        }

        /* Get connected, output the message to the local logger. */
        if (!opened)
                openlog_unlocked(LogTag, LogStat | LOG_NDELAY, 0);
        connectlog();

        /*
         * If the send() failed, there are two likely scenarios:
         * 1) syslogd was restarted.  In this case make one (only) attempt
         *    to reconnect.
         * 2) We filled our buffer due to syslogd not being able to read
         *    as fast as we write.  In this case prefer to lose the current
         *    message rather than whole buffer of previously logged data.
         */
        if (send(LogFile, tbuf, cnt, 0) < 0) {
                if (errno != ENOBUFS) {
                        disconnectlog();
                        connectlog();
                        if (send(LogFile, tbuf, cnt, 0) >= 0)
                                return;
                }
        } else
                return;

        /*
         * Output the message to the console; try not to block
         * as a blocking console should not stop other processes.
         * Make sure the error reported is the one from the syslogd failure.
         */
        if (LogStat & LOG_CONS &&
            (fd = _open(_PATH_CONSOLE, O_WRONLY|O_NONBLOCK|O_CLOEXEC, 0)) >=
            0) {
                struct iovec iov[2];
                struct iovec *v = iov;

                p = strchr(tbuf, '>') + 3;
                v->iov_base = p;
                v->iov_len = cnt - (p - tbuf);
                ++v;
                v->iov_base = "\r\n";
                v->iov_len = 2;
                (void)_writev(fd, iov, 2);
                (void)_close(fd);
        }
}

static void
syslog_cancel_cleanup(void *arg __unused)
{

        THREAD_UNLOCK();
}

void
vsyslog(int pri, const char *fmt, va_list ap)
{

        THREAD_LOCK();
        pthread_cleanup_push(syslog_cancel_cleanup, NULL);
        vsyslog1(pri, fmt, ap);
        pthread_cleanup_pop(1);
}

/* Should be called with mutex acquired */
static void
disconnectlog(void)
{
        /*
         * If the user closed the FD and opened another in the same slot,
         * that's their problem.  They should close it before calling on
         * system services.
         */
        if (LogFile != -1) {
                _close(LogFile);
                LogFile = -1;
        }
        connected = false;                      /* retry connect */
}

/* Should be called with mutex acquired */
static void
connectlog(void)
{
        struct sockaddr_un SyslogAddr;  /* AF_UNIX address of local logger */

        if (LogFile == -1) {
                socklen_t len;

                if ((LogFile = _socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC,
                    0)) == -1)
                        return;
                if (_getsockopt(LogFile, SOL_SOCKET, SO_SNDBUF, &len,
                    &(socklen_t){sizeof(len)}) == 0) {
                        if (len < MAXLINE) {
                                len = MAXLINE;
                                (void)_setsockopt(LogFile, SOL_SOCKET, SO_SNDBUF,
                                    &len, sizeof(len));
                        }
                }
        }
        if (!connected) {
                SyslogAddr.sun_len = sizeof(SyslogAddr);
                SyslogAddr.sun_family = AF_UNIX;

                (void)strncpy(SyslogAddr.sun_path, _PATH_LOG,
                    sizeof SyslogAddr.sun_path);
                if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
                    sizeof(SyslogAddr)) != -1)
                        connected = true;
                else {
                        (void)_close(LogFile);
                        LogFile = -1;
                }
        }
}

static void
openlog_unlocked(const char *ident, int logstat, int logfac)
{
        if (ident != NULL) {
                LogTag = ident;
                LogTagLength = -1;
        }
        LogStat = logstat;
        parse_tag();
        if (logfac != 0 && (logfac &~ LOG_FACMASK) == 0)
                LogFacility = logfac;

        if (LogStat & LOG_NDELAY)       /* open immediately */
                connectlog();

        opened = 1;     /* ident and facility has been set */
}

void
openlog(const char *ident, int logstat, int logfac)
{

        THREAD_LOCK();
        pthread_cleanup_push(syslog_cancel_cleanup, NULL);
        openlog_unlocked(ident, logstat, logfac);
        pthread_cleanup_pop(1);
}


void
closelog(void)
{
        THREAD_LOCK();
        if (LogFile != -1) {
                (void)_close(LogFile);
                LogFile = -1;
        }
        LogTag = NULL;
        LogTagLength = -1;
        connected = false;
        THREAD_UNLOCK();
}

/* setlogmask -- set the log mask level */
int
setlogmask(int pmask)
{
        int omask;

        THREAD_LOCK();
        omask = LogMask;
        if (pmask != 0)
                LogMask = pmask;
        THREAD_UNLOCK();
        return (omask);
}

/*
 * Obtain LogPid from LogTag formatted as per RFC 3164,
 * Section 5.3 Originating Process Information:
 *
 * ident[NNN]
 */
static void
parse_tag(void)
{
        char *begin, *end, *p;
        pid_t pid;

        if (LogTag == NULL || (LogStat & LOG_PID) != 0)
                return;
        /*
         * LogTagLength is -1 if LogTag was not parsed yet.
         * Avoid multiple passes over same LogTag.
         */
        LogTagLength = 0;

        /* Check for presence of opening [ and non-empty ident. */
        if ((begin = strchr(LogTag, '[')) == NULL || begin == LogTag)
                return;
        /* Check for presence of closing ] at the very end and non-empty pid. */
        if ((end = strchr(begin + 1, ']')) == NULL || end[1] != 0 ||
            (end - begin) < 2)
                return;

        /* Check for pid to contain digits only. */
        pid = (pid_t)strtol(begin + 1, &p, 10);
        if (p != end)
                return;

        LogPid = pid;
        LogTagLength = begin - LogTag;
}