lib/lwres/lwconfig.c

/*
 * Copyright (C) 2000-2008, 2011, 2012, 2014, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*! \file */

/**
 * Module for parsing resolv.conf files.
 *
 *    lwres_conf_init() creates an empty lwres_conf_t structure for
 *    lightweight resolver context ctx.
 *
 *    lwres_conf_clear() frees up all the internal memory used by that
 *    lwres_conf_t structure in resolver context ctx.
 *
 *    lwres_conf_parse() opens the file filename and parses it to initialise
 *    the resolver context ctx's lwres_conf_t structure.
 *
 *    lwres_conf_print() prints the lwres_conf_t structure for resolver
 *    context ctx to the FILE fp.
 *
 * \section lwconfig_return Return Values
 *
 *    lwres_conf_parse() returns #LWRES_R_SUCCESS if it successfully read and
 *    parsed filename. It returns #LWRES_R_FAILURE if filename could not be
 *    opened or contained incorrect resolver statements.
 *
 *    lwres_conf_print() returns #LWRES_R_SUCCESS unless an error occurred
 *    when converting the network addresses to a numeric host address
 *    string. If this happens, the function returns #LWRES_R_FAILURE.
 *
 * \section lwconfig_see See Also
 *
 *    stdio(3), \link resolver resolver \endlink
 *
 * \section files Files
 *
 *    /etc/resolv.conf
 */

#include <config.h>

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <lwres/lwbuffer.h>
#include <lwres/lwres.h>
#include <lwres/net.h>
#include <lwres/result.h>
#include <lwres/stdlib.h>
#include <lwres/string.h>

#include "assert_p.h"
#include "context_p.h"
#include "print_p.h"


#if ! defined(NS_INADDRSZ)
#define NS_INADDRSZ  4
#endif

#if ! defined(NS_IN6ADDRSZ)
#define NS_IN6ADDRSZ    16
#endif

static lwres_result_t
lwres_conf_parsenameserver(lwres_context_t *ctx,  FILE *fp);

static lwres_result_t
lwres_conf_parselwserver(lwres_context_t *ctx,  FILE *fp);

static lwres_result_t
lwres_conf_parsedomain(lwres_context_t *ctx, FILE *fp);

static lwres_result_t
lwres_conf_parsesearch(lwres_context_t *ctx,  FILE *fp);

static lwres_result_t
lwres_conf_parsesortlist(lwres_context_t *ctx,  FILE *fp);

static lwres_result_t
lwres_conf_parseoption(lwres_context_t *ctx,  FILE *fp);

static void
lwres_resetaddr(lwres_addr_t *addr);

static lwres_result_t
lwres_create_addr(const char *buff, lwres_addr_t *addr, int convert_zero);

static int lwresaddr2af(int lwresaddrtype);


static int
lwresaddr2af(int lwresaddrtype)
{
    int af = 0;

    switch (lwresaddrtype) {
    case LWRES_ADDRTYPE_V4:
        af = AF_INET;
        break;

    case LWRES_ADDRTYPE_V6:
        af = AF_INET6;
        break;
    }

    return (af);
}


/*!
 * Eat characters from FP until EOL or EOF. Returns EOF or '\n'
 */
static int
eatline(FILE *fp) {
    int ch;

    ch = fgetc(fp);
    while (ch != '\n' && ch != EOF)
        ch = fgetc(fp);

    return (ch);
}


/*!
 * Eats white space up to next newline or non-whitespace character (of
 * EOF). Returns the last character read. Comments are considered white
 * space.
 */
static int
eatwhite(FILE *fp) {
    int ch;

    ch = fgetc(fp);
    while (ch != '\n' && ch != EOF && isspace((unsigned char)ch))
        ch = fgetc(fp);

    if (ch == ';' || ch == '#')
        ch = eatline(fp);

    return (ch);
}


/*!
 * Skip over any leading whitespace and then read in the next sequence of
 * non-whitespace characters. In this context newline is not considered
 * whitespace. Returns EOF on end-of-file, or the character
 * that caused the reading to stop.
 */
static int
getword(FILE *fp, char *buffer, size_t size) {
    int ch;
    char *p = buffer;

    REQUIRE(buffer != NULL);
    REQUIRE(size > 0U);

    *p = '\0';

    ch = eatwhite(fp);

    if (ch == EOF)
        return (EOF);

    do {
        *p = '\0';

        if (ch == EOF || isspace((unsigned char)ch))
            break;
        else if ((size_t) (p - buffer) == size - 1)
            return (EOF);   /* Not enough space. */

        *p++ = (char)ch;
        ch = fgetc(fp);
    } while (1);

    return (ch);
}

static void
lwres_resetaddr(lwres_addr_t *addr) {
    REQUIRE(addr != NULL);

    memset(addr->address, 0, LWRES_ADDR_MAXLEN);
    addr->family = 0;
    addr->length = 0;
    addr->zone = 0;
}

static char *
lwres_strdup(lwres_context_t *ctx, const char *str) {
    char *p;

    REQUIRE(str != NULL);
    REQUIRE(strlen(str) > 0U);

    p = CTXMALLOC(strlen(str) + 1);
    if (p != NULL)
        strcpy(p, str);

    return (p);
}

/*% intializes data structure for subsequent config parsing. */
void
lwres_conf_init(lwres_context_t *ctx) {
    int i;
    lwres_conf_t *confdata;

    REQUIRE(ctx != NULL);
    confdata = &ctx->confdata;

    confdata->nsnext = 0;
    confdata->lwnext = 0;
    confdata->domainname = NULL;
    confdata->searchnxt = 0;
    confdata->sortlistnxt = 0;
    confdata->resdebug = 0;
    confdata->ndots = 1;
    confdata->no_tld_query = 0;
    confdata->attempts = 0;
    confdata->timeout = 0;

    for (i = 0; i < LWRES_CONFMAXNAMESERVERS; i++)
        lwres_resetaddr(&confdata->nameservers[i]);

    for (i = 0; i < LWRES_CONFMAXSEARCH; i++)
        confdata->search[i] = NULL;

    for (i = 0; i < LWRES_CONFMAXSORTLIST; i++) {
        lwres_resetaddr(&confdata->sortlist[i].addr);
        lwres_resetaddr(&confdata->sortlist[i].mask);
    }
}

/*% Frees up all the internal memory used by the config data structure, returning it to the lwres_context_t. */
void
lwres_conf_clear(lwres_context_t *ctx) {
    int i;
    lwres_conf_t *confdata;

    REQUIRE(ctx != NULL);
    confdata = &ctx->confdata;

    for (i = 0; i < confdata->nsnext; i++)
        lwres_resetaddr(&confdata->nameservers[i]);

    if (confdata->domainname != NULL) {
        CTXFREE(confdata->domainname,
            strlen(confdata->domainname) + 1);
        confdata->domainname = NULL;
    }

    for (i = 0; i < confdata->searchnxt; i++) {
        if (confdata->search[i] != NULL) {
            CTXFREE(confdata->search[i],
                strlen(confdata->search[i]) + 1);
            confdata->search[i] = NULL;
        }
    }

    for (i = 0; i < LWRES_CONFMAXSORTLIST; i++) {
        lwres_resetaddr(&confdata->sortlist[i].addr);
        lwres_resetaddr(&confdata->sortlist[i].mask);
    }

    confdata->nsnext = 0;
    confdata->lwnext = 0;
    confdata->domainname = NULL;
    confdata->searchnxt = 0;
    confdata->sortlistnxt = 0;
    confdata->resdebug = 0;
    confdata->ndots = 1;
    confdata->no_tld_query = 0;
    confdata->attempts = 0;
    confdata->timeout = 0;
}

static lwres_result_t
lwres_conf_parsenameserver(lwres_context_t *ctx,  FILE *fp) {
    char word[LWRES_CONFMAXLINELEN];
    int res;
    lwres_conf_t *confdata;
    lwres_addr_t address;

    confdata = &ctx->confdata;

    if (confdata->nsnext == LWRES_CONFMAXNAMESERVERS)
        return (LWRES_R_SUCCESS);

    res = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Nothing on line. */
    else if (res == ' ' || res == '\t')
        res = eatwhite(fp);

    if (res != EOF && res != '\n')
        return (LWRES_R_FAILURE); /* Extra junk on line. */

    res = lwres_create_addr(word, &address, 1);
    if (res == LWRES_R_SUCCESS &&
        ((address.family == LWRES_ADDRTYPE_V4 && ctx->use_ipv4 == 1) ||
         (address.family == LWRES_ADDRTYPE_V6 && ctx->use_ipv6 == 1))) {
        confdata->nameservers[confdata->nsnext++] = address;
    }

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_conf_parselwserver(lwres_context_t *ctx,  FILE *fp) {
    char word[LWRES_CONFMAXLINELEN];
    int res;
    lwres_conf_t *confdata;

    confdata = &ctx->confdata;

    if (confdata->lwnext == LWRES_CONFMAXLWSERVERS)
        return (LWRES_R_SUCCESS);

    res = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Nothing on line. */
    else if (res == ' ' || res == '\t')
        res = eatwhite(fp);

    if (res != EOF && res != '\n')
        return (LWRES_R_FAILURE); /* Extra junk on line. */

    res = lwres_create_addr(word,
                &confdata->lwservers[confdata->lwnext++], 1);
    if (res != LWRES_R_SUCCESS)
        return (res);

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_conf_parsedomain(lwres_context_t *ctx,  FILE *fp) {
    char word[LWRES_CONFMAXLINELEN];
    int res, i;
    lwres_conf_t *confdata;

    confdata = &ctx->confdata;

    res = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Nothing else on line. */
    else if (res == ' ' || res == '\t')
        res = eatwhite(fp);

    if (res != EOF && res != '\n')
        return (LWRES_R_FAILURE); /* Extra junk on line. */

    if (confdata->domainname != NULL)
        CTXFREE(confdata->domainname,
            strlen(confdata->domainname) + 1); /*  */

    /*
     * Search and domain are mutually exclusive.
     */
    for (i = 0; i < LWRES_CONFMAXSEARCH; i++) {
        if (confdata->search[i] != NULL) {
            CTXFREE(confdata->search[i],
                strlen(confdata->search[i])+1);
            confdata->search[i] = NULL;
        }
    }
    confdata->searchnxt = 0;

    confdata->domainname = lwres_strdup(ctx, word);

    if (confdata->domainname == NULL)
        return (LWRES_R_FAILURE);

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_conf_parsesearch(lwres_context_t *ctx,  FILE *fp) {
    int idx, delim;
    char word[LWRES_CONFMAXLINELEN];
    lwres_conf_t *confdata;

    confdata = &ctx->confdata;

    if (confdata->domainname != NULL) {
        /*
         * Search and domain are mutually exclusive.
         */
        CTXFREE(confdata->domainname,
            strlen(confdata->domainname) + 1);
        confdata->domainname = NULL;
    }

    /*
     * Remove any previous search definitions.
     */
    for (idx = 0; idx < LWRES_CONFMAXSEARCH; idx++) {
        if (confdata->search[idx] != NULL) {
            CTXFREE(confdata->search[idx],
                strlen(confdata->search[idx])+1);
            confdata->search[idx] = NULL;
        }
    }
    confdata->searchnxt = 0;

    delim = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Nothing else on line. */

    idx = 0;
    while (strlen(word) > 0U) {
        if (confdata->searchnxt == LWRES_CONFMAXSEARCH)
            goto ignore; /* Too many domains. */

        confdata->search[idx] = lwres_strdup(ctx, word);
        if (confdata->search[idx] == NULL)
            return (LWRES_R_FAILURE);
        idx++;
        confdata->searchnxt++;

    ignore:
        if (delim == EOF || delim == '\n')
            break;
        else
            delim = getword(fp, word, sizeof(word));
    }

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_create_addr(const char *buffer, lwres_addr_t *addr, int convert_zero) {
    struct in_addr v4;
    struct in6_addr v6;
    char buf[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255") +
         sizeof("%4294967295")];
    char *percent;
    size_t n;

    n = strlcpy(buf, buffer, sizeof(buf));
    if (n >= sizeof(buf))
        return (LWRES_R_FAILURE);

    percent = strchr(buf, '%');
    if (percent != NULL)
        *percent = 0;

    if (lwres_net_aton(buffer, &v4) == 1) {
        if (convert_zero) {
            unsigned char zeroaddress[] = {0, 0, 0, 0};
            unsigned char loopaddress[] = {127, 0, 0, 1};
            if (memcmp(&v4, zeroaddress, 4) == 0)
                memmove(&v4, loopaddress, 4);
        }
        addr->family = LWRES_ADDRTYPE_V4;
        addr->length = NS_INADDRSZ;
        addr->zone = 0;
        memmove((void *)addr->address, &v4, NS_INADDRSZ);

    } else if (lwres_net_pton(AF_INET6, buf, &v6) == 1) {
        addr->family = LWRES_ADDRTYPE_V6;
        addr->length = NS_IN6ADDRSZ;
        memmove((void *)addr->address, &v6, NS_IN6ADDRSZ);
        if (percent != NULL) {
            unsigned long zone;
            char *ep;

            percent++;

#ifdef HAVE_IF_NAMETOINDEX
            zone = if_nametoindex(percent);
            if (zone != 0U) {
                addr->zone = zone;
                return (LWRES_R_SUCCESS);
            }
#endif
            zone = strtoul(percent, &ep, 10);
            if (ep != percent && *ep == 0)
                addr->zone = zone;
            else
                return (LWRES_R_FAILURE);
        } else
            addr->zone = 0;
    } else
        return (LWRES_R_FAILURE); /* Unrecognised format. */

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_conf_parsesortlist(lwres_context_t *ctx,  FILE *fp) {
    int delim, res, idx;
    char word[LWRES_CONFMAXLINELEN];
    char *p;
    lwres_conf_t *confdata;

    confdata = &ctx->confdata;

    delim = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Empty line after keyword. */

    while (strlen(word) > 0U) {
        if (confdata->sortlistnxt == LWRES_CONFMAXSORTLIST)
            return (LWRES_R_FAILURE); /* Too many values. */

        p = strchr(word, '/');
        if (p != NULL)
            *p++ = '\0';

        idx = confdata->sortlistnxt;
        res = lwres_create_addr(word, &confdata->sortlist[idx].addr, 1);
        if (res != LWRES_R_SUCCESS)
            return (res);

        if (p != NULL) {
            res = lwres_create_addr(p,
                        &confdata->sortlist[idx].mask,
                        0);
            if (res != LWRES_R_SUCCESS)
                return (res);
        } else {
            /*
             * Make up a mask.
             */
            confdata->sortlist[idx].mask =
                confdata->sortlist[idx].addr;

            memset(&confdata->sortlist[idx].mask.address, 0xff,
                   confdata->sortlist[idx].addr.length);
        }

        confdata->sortlistnxt++;

        if (delim == EOF || delim == '\n')
            break;
        else
            delim = getword(fp, word, sizeof(word));
    }

    return (LWRES_R_SUCCESS);
}

static lwres_result_t
lwres_conf_parseoption(lwres_context_t *ctx,  FILE *fp) {
    int delim;
    long ndots;
    long attempts;
    long timeout;
    char *p;
    char word[LWRES_CONFMAXLINELEN];
    lwres_conf_t *confdata;

    REQUIRE(ctx != NULL);
    confdata = &ctx->confdata;

    delim = getword(fp, word, sizeof(word));
    if (strlen(word) == 0U)
        return (LWRES_R_FAILURE); /* Empty line after keyword. */

    while (strlen(word) > 0U) {
        if (strcmp("debug", word) == 0) {
            confdata->resdebug = 1;
        } else if (strcmp("no_tld_query", word) == 0) {
            confdata->no_tld_query = 1;
        } else if (strcmp("debug", word) == 0) {
            confdata->resdebug = 1;
        } else if (strncmp("ndots:", word, 6) == 0) {
            ndots = strtol(word + 6, &p, 10);
            if (*p != '\0') /* Bad string. */
                return (LWRES_R_FAILURE);
            if (ndots < 0 || ndots > 0xff) /* Out of range. */
                return (LWRES_R_FAILURE);
            confdata->ndots = (lwres_uint8_t)ndots;
        } else if (strncmp("timeout:", word, 8) == 0) {
            timeout = strtol(word + 8, &p, 10);
            if (*p != '\0') /* Bad string. */
                return (LWRES_R_FAILURE);
            confdata->timeout = (lwres_int32_t)timeout;
        } else if (strncmp("attempts:", word, 9) == 0) {
            attempts = strtol(word + 9, &p, 10);
            if (*p != '\0') /* Bad string. */
                return (LWRES_R_FAILURE);
            if (attempts < 0) /* Out of range. */
                return (LWRES_R_FAILURE);
            confdata->attempts = (lwres_int32_t)attempts;
        }

        if (delim == EOF || delim == '\n')
            break;
        else
            delim = getword(fp, word, sizeof(word));
    }

    return (LWRES_R_SUCCESS);
}

/*% parses a file and fills in the data structure. */
lwres_result_t
lwres_conf_parse(lwres_context_t *ctx, const char *filename) {
    FILE *fp = NULL;
    char word[256];
    lwres_result_t rval, ret;
    lwres_conf_t *confdata;
    int stopchar;

    REQUIRE(ctx != NULL);
    confdata = &ctx->confdata;

    REQUIRE(filename != NULL);
    REQUIRE(strlen(filename) > 0U);
    REQUIRE(confdata != NULL);

    errno = 0;
    if ((fp = fopen(filename, "r")) == NULL)
        return (LWRES_R_NOTFOUND);

    ret = LWRES_R_SUCCESS;
    do {
        stopchar = getword(fp, word, sizeof(word));
        if (stopchar == EOF) {
            rval = LWRES_R_SUCCESS;
            POST(rval);
            break;
        }

        if (strlen(word) == 0U)
            rval = LWRES_R_SUCCESS;
        else if (strcmp(word, "nameserver") == 0)
            rval = lwres_conf_parsenameserver(ctx, fp);
        else if (strcmp(word, "lwserver") == 0)
            rval = lwres_conf_parselwserver(ctx, fp);
        else if (strcmp(word, "domain") == 0)
            rval = lwres_conf_parsedomain(ctx, fp);
        else if (strcmp(word, "search") == 0)
            rval = lwres_conf_parsesearch(ctx, fp);
        else if (strcmp(word, "sortlist") == 0)
            rval = lwres_conf_parsesortlist(ctx, fp);
        else if (strcmp(word, "options") == 0)
            rval = lwres_conf_parseoption(ctx, fp);
        else {
            /* unrecognised word. Ignore entire line */
            rval = LWRES_R_SUCCESS;
            stopchar = eatline(fp);
            if (stopchar == EOF) {
                break;
            }
        }
        if (ret == LWRES_R_SUCCESS && rval != LWRES_R_SUCCESS)
            ret = rval;
    } while (1);

    fclose(fp);

    return (ret);
}

/*% Prints the config data structure to the FILE. */
lwres_result_t
lwres_conf_print(lwres_context_t *ctx, FILE *fp) {
    int i;
    int af;
    char tmp[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
    char buf[sizeof("%4000000000")];
    const char *p;
    lwres_conf_t *confdata;
    lwres_addr_t tmpaddr;

    REQUIRE(ctx != NULL);
    confdata = &ctx->confdata;

    REQUIRE(confdata->nsnext <= LWRES_CONFMAXNAMESERVERS);

    for (i = 0; i < confdata->nsnext; i++) {
        af = lwresaddr2af(confdata->nameservers[i].family);

        p = lwres_net_ntop(af, confdata->nameservers[i].address,
                   tmp, sizeof(tmp));
        if (p != tmp)
            return (LWRES_R_FAILURE);

        if (af == AF_INET6 && confdata->lwservers[i].zone != 0) {
            snprintf(buf, sizeof(buf), "%%%u",
                confdata->nameservers[i].zone);
        } else
            buf[0] = 0;

        fprintf(fp, "nameserver %s%s\n", tmp, buf);
    }

    for (i = 0; i < confdata->lwnext; i++) {
        af = lwresaddr2af(confdata->lwservers[i].family);

        p = lwres_net_ntop(af, confdata->lwservers[i].address,
                   tmp, sizeof(tmp));
        if (p != tmp)
            return (LWRES_R_FAILURE);

        if (af == AF_INET6 && confdata->lwservers[i].zone != 0) {
            snprintf(buf, sizeof(buf), "%%%u",
                confdata->nameservers[i].zone);
        } else
            buf[0] = 0;

        fprintf(fp, "lwserver %s%s\n", tmp, buf);
    }

    if (confdata->domainname != NULL) {
        fprintf(fp, "domain %s\n", confdata->domainname);
    } else if (confdata->searchnxt > 0) {
        REQUIRE(confdata->searchnxt <= LWRES_CONFMAXSEARCH);

        fprintf(fp, "search");
        for (i = 0; i < confdata->searchnxt; i++)
            fprintf(fp, " %s", confdata->search[i]);
        fputc('\n', fp);
    }

    REQUIRE(confdata->sortlistnxt <= LWRES_CONFMAXSORTLIST);

    if (confdata->sortlistnxt > 0) {
        fputs("sortlist", fp);
        for (i = 0; i < confdata->sortlistnxt; i++) {
            af = lwresaddr2af(confdata->sortlist[i].addr.family);

            p = lwres_net_ntop(af,
                       confdata->sortlist[i].addr.address,
                       tmp, sizeof(tmp));
            if (p != tmp)
                return (LWRES_R_FAILURE);

            fprintf(fp, " %s", tmp);

            tmpaddr = confdata->sortlist[i].mask;
            memset(&tmpaddr.address, 0xff, tmpaddr.length);

            if (memcmp(&tmpaddr.address,
                   confdata->sortlist[i].mask.address,
                   confdata->sortlist[i].mask.length) != 0) {
                af = lwresaddr2af(
                        confdata->sortlist[i].mask.family);
                p = lwres_net_ntop
                    (af,
                     confdata->sortlist[i].mask.address,
                     tmp, sizeof(tmp));
                if (p != tmp)
                    return (LWRES_R_FAILURE);

                fprintf(fp, "/%s", tmp);
            }
        }
        fputc('\n', fp);
    }

    if (confdata->resdebug)
        fprintf(fp, "options debug\n");

    if (confdata->ndots > 0)
        fprintf(fp, "options ndots:%d\n", confdata->ndots);

    if (confdata->no_tld_query)
        fprintf(fp, "options no_tld_query\n");

    if (confdata->attempts)
        fprintf(fp, "options attempts:%d\n", confdata->attempts);

    if (confdata->timeout)
        fprintf(fp, "options timeout:%d\n", confdata->timeout);

    return (LWRES_R_SUCCESS);
}

/*% Returns a pointer to the current config structure. */
lwres_conf_t *
lwres_conf_get(lwres_context_t *ctx) {
    REQUIRE(ctx != NULL);

    return (&ctx->confdata);
}