ServiceRegistration/config-parse.c

/* -*- Mode: C; tab-width: 4; c-file-style: "bsd"; c-basic-offset: 4; fill-column: 108 -*-
 *
 * Copyright (c) 2002-2004 Apple Computer, Inc. All rights reserved.
 * Copyright (c) 2018 Apple Computer, Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

//*************************************************************************************************************
//
// General purpose stupid little parser, currently used by dnssd-proxy for its configuration file
//
//*************************************************************************************************************
// Headers

#include <stdio.h>          // For printf()
#include <stdlib.h>         // For malloc()
#include <string.h>         // For strrchr(), strcmp()
#include <time.h>           // For "struct tm" etc.
#include <signal.h>         // For SIGINT, SIGTERM
#include <assert.h>
#include <netdb.h>           // For gethostbyname()
#include <sys/socket.h>      // For AF_INET, AF_INET6, etc.
#include <net/if.h>          // For IF_NAMESIZE
#include <netinet/in.h>      // For INADDR_NONE
#include <netinet/tcp.h>     // For SOL_TCP, TCP_NOTSENT_LOWAT
#include <arpa/inet.h>       // For inet_addr()
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>

#include "srp.h"
#include "config-parse.h"

#ifdef STANDALONE
#undef LogMsg
#define LogMsg(fmt, ...) fprintf(stderr, fmt "\n", ##__VA_ARGS__)
#endif // STANDALONE

// Parse one line of a config file.
// A line consists of a verb followed by one or more hunks of text.
// We parse the verb first, then that tells us how many hunks of text to expect.
// Each hunk is space-delineated; the last hunk can contain spaces.
static bool config_parse_line(void *context, const char *filename, char *line, int lineno,
							  config_file_verb_t *verbs, int num_verbs)
{
	char *sp;
#define MAXCFHUNKS 10
	char *hunks[MAXCFHUNKS];
	int num_hunks = 0;
	config_file_verb_t *config_file_verb = NULL;
	int i;

	sp = line;
	do {
		// Skip leading spaces.
		while (*sp && (*sp == ' ' || *sp == '\t'))
			sp++;
		if (num_hunks == 0) {
			// If this is a blank line with spaces on it or a comment line, we ignore it.
			if (!*sp || *sp == '#')
				return true;
		}
		hunks[num_hunks++] = sp;
		// Find EOL or hunk
		while (*sp && (*sp != ' ' && *sp != '\t')) {
			sp++;
		}
		if (*sp) {
			*sp++ = 0;
		}
		if (num_hunks == 1) {
			for (i = 0; i < num_verbs; i++) {
				// If the verb name matches, or the verb name is NULL (meaning whatever doesn't
				// match a preceding verb), we've found our verb.
				if (verbs[i].name == NULL || !strcmp(verbs[i].name, hunks[0])) {
					config_file_verb = &verbs[i];
					break;
				}
			}
			if (config_file_verb == NULL) {
				INFO("unknown verb %s at line %d", hunks[0], lineno);
				return false;
			}
		}				
	} while (*sp && num_hunks < MAXCFHUNKS && config_file_verb->max_hunks > num_hunks);
	
	// If we didn't get the hunks we needed, bail.
	if (config_file_verb->min_hunks > num_hunks) {
		INFO("error: verb %s requires between %d and %d modifiers; %d given at line %d",
			 hunks[0], config_file_verb->min_hunks, config_file_verb->max_hunks, num_hunks, lineno);
		return false;
	}

	return config_file_verb->handler(context, filename, hunks, num_hunks, lineno);
}

// Parse a configuration file
bool config_parse(void *context, const char *filename, config_file_verb_t *verbs, int num_verbs)
{
	int file;
	char *buf, *line, *eof, *eol, *nextCR, *nextNL;
	off_t flen, have;
    ssize_t len;
    int lineno;
	bool success = true;

	file = open(filename, O_RDONLY);
	if (file < 0) {
		INFO("fatal: %s: %s", filename, strerror(errno));
		return false;
	}

	// Get the length of the file.
	flen = lseek(file, 0, SEEK_END);
	lseek(file, 0, SEEK_SET);
	buf = malloc(flen + 1);
	if (buf == NULL) {
		INFO("fatal: not enough memory for %s", filename);
		goto outclose;
	}
	
	// Just in case we have a read() syscall that doesn't always read the whole file at once
	have = 0;
	while (have < flen) {
		len = read(file, &buf[have], flen - have);
		if (len < 0) {
			INFO("fatal: read of %s at %lld len %lld: %s",
				 filename, (long long)have, (long long)(flen - have), strerror(errno));
			goto outfree;
		}
		if (len == 0) {
			INFO("fatal: read of %s at %lld len %lld: zero bytes read",
				 filename, (long long)have, (long long)(flen - have));
		outfree:
			free(buf);
		outclose:
			close(file);
			return false;
		}
		have += len;
	}
	close(file);
	buf[flen] = 0; // NUL terminate.
	eof = buf + flen;
	
	// Parse through the file line by line.
	line = buf;
	lineno = 1;
	while (line < eof) { // < because NUL at eof could be last eol.
		nextCR = strchr(line, '\r');
		nextNL = strchr(line, '\n');

		// Added complexity for CR/LF agnostic line endings.   Necessary?
		if (nextNL != NULL) {
			if (nextCR != NULL && nextCR < nextNL)
				eol = nextCR;
			else
				eol = nextNL;
		} else {
			if (nextCR != NULL)
				eol = nextCR;
			else
				eol = buf + flen;
		}

		// If this isn't a blank line or a comment line, parse it.
		if (eol - line != 1 && line[0] != '#') {
			*eol = 0;
			// If we get a bad config line, we're going to return failure later, but continue parsing now.
			if (!config_parse_line(context, filename, line, lineno, verbs, num_verbs))
				success = false;
        }
        line = eol + 1;
        lineno++;
	}		
	free(buf);
	return success;
}