/*
 * Copyright (c) 2008-2014, Simon Schubert <2@0x2c.org>.
 * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Simon Schubert <2@0x2c.org>.
 *
 * 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 DragonFly Project 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 COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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 <errno.h>
#include <inttypes.h>
#include <malloc_np.h>
#include <signal.h>
#include <strings.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#include "dma.h"

#define MAX_LINE_RFC822	999 /* 998 characters plus \n */

void
bounce(struct qitem *it, const char *reason)
{
	struct queue bounceq;
	char line[1000];
	size_t pos;
	int error;

	/* Don't bounce bounced mails */
	if (it->sender[0] == 0) {
		syslog(LOG_INFO, "can not bounce a bounce message, discarding");
		exit(EX_SOFTWARE);
	}

	bzero(&bounceq, sizeof(bounceq));
	LIST_INIT(&bounceq.queue);
	bounceq.sender = "";
	if (add_recp(&bounceq, it->sender, EXPAND_WILDCARD) != 0)
		goto fail;

	if (newspoolf(&bounceq) != 0)
		goto fail;

	syslog(LOG_ERR, "delivery failed, bouncing as %s", bounceq.id);
	setlogident("%s", bounceq.id);

	error = fprintf(bounceq.mailf,
		"Received: from MAILER-DAEMON\n"
		"\tid %s\n"
		"\tby %s (%s on %s);\n"
		"\t%s\n"
		"X-Original-To: <%s>\n"
		"From: MAILER-DAEMON <>\n"
		"To: %s\n"
		"Subject: Mail delivery failed\n"
		"Message-Id: <%s@%s>\n"
		"Date: %s\n"
		"\n"
		"This is the %s at %s.\n"
		"\n"
		"There was an error delivering your mail to <%s>.\n"
		"\n"
		"%s\n"
		"\n"
		"%s\n"
		"\n",
		bounceq.id,
		hostname(), VERSION, systemhostname(),
		rfc822date(),
		it->addr,
		it->sender,
		bounceq.id, hostname(),
		rfc822date(),
		VERSION, hostname(),
		it->addr,
		reason,
		config.features & FULLBOUNCE ?
		    "Original message follows." :
		    "Message headers follow.");
	if (error < 0)
		goto fail;

	if (fseek(it->mailf, 0, SEEK_SET) != 0)
		goto fail;
	if (config.features & FULLBOUNCE) {
		while ((pos = fread(line, 1, sizeof(line), it->mailf)) > 0) {
			if (fwrite(line, 1, pos, bounceq.mailf) != pos)
				goto fail;
		}
	} else {
		while (!feof(it->mailf)) {
			if (fgets(line, sizeof(line), it->mailf) == NULL)
				break;
			if (line[0] == '\n')
				break;
			if (fwrite(line, strlen(line), 1, bounceq.mailf) != 1)
				goto fail;
		}
	}

	if (linkspool(&bounceq) != 0)
		goto fail;
	/* bounce is safe */

	delqueue(it);

	run_queue(&bounceq);
	/* NOTREACHED */

fail:
	syslog(LOG_CRIT, "error creating bounce: %m");
	delqueue(it);
	exit(EX_IOERR);
}

struct parse_state {
	char addr[1000];
	int pos;

	enum {
		NONE = 0,
		START,
		MAIN,
		EOL,
		QUIT
	} state;
	int comment;
	int quote;
	int brackets;
	int esc;
};

/*
 * Simplified RFC2822 header/address parsing.
 * We copy escapes and quoted strings directly, since
 * we have to pass them like this to the mail server anyways.
 * XXX local addresses will need treatment
 */
static int
parse_addrs(struct parse_state *ps, char *s, struct queue *queue)
{
	char *addr;

again:
	switch (ps->state) {
	case NONE:
		return (-1);

	case START:
		/* init our data */
		bzero(ps, sizeof(*ps));

		/* skip over header name */
		while (*s != ':')
			s++;
		s++;
		ps->state = MAIN;
		break;

	case MAIN:
		/* all fine */
		break;

	case EOL:
		switch (*s) {
		case ' ':
		case '\t':
			ps->state = MAIN;
			break;

		default:
			ps->state = QUIT;
			if (ps->pos != 0)
				goto newaddr;
			return (0);
		}
		break;

	case QUIT:
		return (0);
	}

	for (; *s != 0; s++) {
		if (ps->esc) {
			ps->esc = 0;

			switch (*s) {
			case '\r':
			case '\n':
				goto err;

			default:
				goto copy;
			}
		}

		if (ps->quote) {
			switch (*s) {
			case '"':
				ps->quote = 0;
				goto copy;

			case '\\':
				ps->esc = 1;
				goto copy;

			case '\r':
			case '\n':
				goto eol;

			default:
				goto copy;
			}
		}

		switch (*s) {
		case '(':
			ps->comment++;
			break;

		case ')':
			if (ps->comment)
				ps->comment--;
			else
				goto err;
			goto skip;

		case '"':
			ps->quote = 1;
			goto copy;

		case '\\':
			ps->esc = 1;
			goto copy;

		case '\r':
		case '\n':
			goto eol;
		}

		if (ps->comment)
			goto skip;

		switch (*s) {
		case ' ':
		case '\t':
			/* ignore whitespace */
			goto skip;

		case '<':
			/* this is the real address now */
			ps->brackets = 1;
			ps->pos = 0;
			goto skip;

		case '>':
			if (!ps->brackets)
				goto err;
			ps->brackets = 0;

			s++;
			goto newaddr;

		case ':':
			/* group - ignore */
			ps->pos = 0;
			goto skip;

		case ',':
		case ';':
			/*
			 * Next address, copy previous one.
			 * However, we might be directly after
			 * a <address>, or have two consecutive
			 * commas.
			 * Skip the comma unless there is
			 * really something to copy.
			 */
			if (ps->pos == 0)
				goto skip;
			s++;
			goto newaddr;

		default:
			goto copy;
		}

copy:
		if (ps->comment)
			goto skip;

		if (ps->pos + 1 == sizeof(ps->addr))
			goto err;
		ps->addr[ps->pos++] = *s;

skip:
		;
	}

eol:
	ps->state = EOL;
	return (0);

err:
	ps->state = QUIT;
	return (-1);

newaddr:
	ps->addr[ps->pos] = 0;
	ps->pos = 0;
	addr = strdup(ps->addr);
	if (addr == NULL)
		errlog(EX_SOFTWARE, "strdup");

	if (add_recp(queue, addr, EXPAND_WILDCARD) != 0)
		errlogx(EX_DATAERR, "invalid recipient `%s'", addr);

	goto again;
}

static int
writeline(struct queue *queue, const char *line, ssize_t linelen)
{
	ssize_t len;

	while (linelen > 0) {
		len = linelen;
		if (linelen > MAX_LINE_RFC822) {
			len = MAX_LINE_RFC822 - 10;
		}

		if (fwrite(line, len, 1, queue->mailf) != 1)
			return (-1);

		if (linelen <= MAX_LINE_RFC822)
			break;

		if (fwrite("\n", 1, 1, queue->mailf) != 1)
			return (-1);

		line += MAX_LINE_RFC822 - 10;
		linelen = strlen(line);
	}
	return (0);
}

int
readmail(struct queue *queue, int nodot, int recp_from_header)
{
	struct parse_state parse_state;
	char *line = NULL;
	ssize_t linelen;
	size_t linecap = 0;
	char newline[MAX_LINE_RFC822 + 1];
	size_t error;
	int had_headers = 0;
	int had_from = 0;
	int had_messagid = 0;
	int had_date = 0;
	int had_first_line = 0;
	int had_last_line = 0;
	int nocopy = 0;
	int ret = -1;

	parse_state.state = NONE;

	error = fprintf(queue->mailf,
		"Received: from %s (uid %d)\n"
		"\t(envelope-from %s)\n"
		"\tid %s\n"
		"\tby %s (%s on %s);\n"
		"\t%s\n",
		username, useruid,
		queue->sender,
		queue->id,
		hostname(), VERSION, systemhostname(),
		rfc822date());
	if ((ssize_t)error < 0)
		return (-1);

	while ((linelen = getline(&line, &linecap, stdin)) > 0) {
		newline[0] = '\0';
		if (had_last_line)
			errlogx(EX_DATAERR, "bad mail input format:"
				" from %s (uid %d) (envelope-from %s)",
				username, useruid, queue->sender);
		linelen = strlen(line);
		if (linelen == 0 || line[linelen - 1] != '\n') {
			/*
			 * This line did not end with a newline character.
			 * If we fix it, it better be the last line of
			 * the file.
			 */
			if ((size_t)linelen + 1 > linecap) {
				line = realloc(line, linelen + 2);
				if (line == NULL)
					errlogx(EX_SOFTWARE, "realloc");
				linecap = malloc_usable_size(line);
			}
			line[linelen++] = '\n';
			line[linelen] = 0;
			had_last_line = 1;
		}
		if (!had_first_line) {
			/*
			 * Ignore a leading RFC-976 From_ or >From_ line mistakenly
			 * inserted by some programs.
			 */
			if (strprefixcmp(line, "From ") == 0 || strprefixcmp(line, ">From ") == 0)
				continue;
			had_first_line = 1;
		}
		if (!had_headers) {
			if (linelen > MAX_LINE_RFC822) {
				/* XXX also split headers */
				errlogx(EX_DATAERR, "bad mail input format:"
				    " from %s (uid %d) (envelope-from %s)",
				    username, useruid, queue->sender);
			}
			/*
			 * Unless this is a continuation, switch of
			 * the Bcc: nocopy flag.
			 */
			if (!(line[0] == ' ' || line[0] == '\t'))
				nocopy = 0;

			if (strprefixcmp(line, "Date:") == 0)
				had_date = 1;
			else if (strprefixcmp(line, "Message-Id:") == 0)
				had_messagid = 1;
			else if (strprefixcmp(line, "From:") == 0)
				had_from = 1;
			else if (strprefixcmp(line, "Bcc:") == 0)
				nocopy = 1;

			if (parse_state.state != NONE) {
				if (parse_addrs(&parse_state, line, queue) < 0) {
					errlogx(EX_DATAERR, "invalid address in header\n");
					/* NOTREACHED */
				}
			}

			if (recp_from_header && (
					strprefixcmp(line, "To:") == 0 ||
					strprefixcmp(line, "Cc:") == 0 ||
					strprefixcmp(line, "Bcc:") == 0)) {
				parse_state.state = START;
				if (parse_addrs(&parse_state, line, queue) < 0) {
					errlogx(EX_DATAERR, "invalid address in header\n");
					/* NOTREACHED */
				}
			}
		}

		if (strcmp(line, "\n") == 0 && !had_headers) {
			had_headers = 1;
			while (!had_date || !had_messagid || !had_from) {
				if (!had_date) {
					had_date = 1;
					snprintf(newline, sizeof(newline), "Date: %s\n", rfc822date());
				} else if (!had_messagid) {
					/* XXX msgid, assign earlier and log? */
					had_messagid = 1;
					snprintf(newline, sizeof(newline), "Message-Id: <%"PRIxMAX".%s.%"PRIxMAX"@%s>\n",
						 (uintmax_t)time(NULL),
						 queue->id,
						 (uintmax_t)random(),
						 hostname());
				} else if (!had_from) {
					had_from = 1;
					snprintf(newline, sizeof(newline), "From: <%s>\n", queue->sender);
				}
				if (fwrite(newline, strlen(newline), 1, queue->mailf) != 1)
					goto fail;
			}
			strlcpy(newline, "\n", sizeof(newline));
		}
		if (!nodot && linelen == 2 && line[0] == '.')
			break;
		if (!nocopy) {
			if (newline[0]) {
				if (fwrite(newline, strlen(newline), 1, queue->mailf) != 1)
					goto fail;
			} else {
				if (writeline(queue, line, linelen) != 0)
					goto fail;
			}
		}
	}
	if (ferror(stdin) == 0)
		ret = 0;
fail:
	free(line);
	return (ret);
}
