source: mainline/uspace/srv/net/dnsrsrv/dns_msg.c

/*
 * Copyright (c) 2013 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/** @addtogroup dnsrsrv
 * @{
 */
/**
 * @file
 */

#include <bitops.h>
#include <byteorder.h>
#include <errno.h>
#include <io/log.h>
#include <macros.h>
#include <stdint.h>
#include <stdlib.h>
#include <str.h>

#include "dns_msg.h"
#include "dns_std.h"

#define NAME  "dnsres"

static uint16_t dns_uint16_t_decode(uint8_t *, size_t);

/** Extend dynamically allocated string with suffix.
 *
 * @a *dstr points to a dynamically allocated buffer containing a string.
 * Reallocate this buffer so that concatenation of @a *dstr and @a suff can
 * fit in and append @a suff.
 */
static errno_t dns_dstr_ext(char **dstr, const char *suff)
{
        size_t s1, s2;
        size_t nsize;
        char *nstr;

        if (*dstr == NULL) {
                *dstr = str_dup(suff);
                if (*dstr == NULL)
                        return ENOMEM;
                return EOK;
        }

        s1 = str_size(*dstr);
        s2 = str_size(suff);
        nsize = s1 + s2 + 1;

        nstr = realloc(*dstr, nsize);
        if (nstr == NULL)
                return ENOMEM;

        str_cpy(nstr + s1, nsize - s1, suff);

        *dstr = nstr;
        return EOK;
}

/** Encode DNS name.
 *
 * Encode DNS name or measure the size of encoded name (with @a buf NULL,
 * and @a buf_size 0).
 *
 * @param name          String to encode
 * @param buf           Buffer or NULL
 * @param buf_size      Buffer size or 0 if @a buf is NULL
 * @param act_size      Place to store actual encoded size
 */
static errno_t dns_name_encode(char *name, uint8_t *buf, size_t buf_size,
    size_t *act_size)
{
        size_t off;
        char32_t c;
        size_t lsize;
        size_t pi, di;

        pi = 0;
        di = 1;
        off = 0;

        lsize = 0;
        while (true) {
                c = str_decode(name, &off, STR_NO_LIMIT);
                if (c >= 127) {
                        /* Non-ASCII character */
                        log_msg(LOG_DEFAULT, LVL_DEBUG, "Non-ascii character");
                        return EINVAL;
                }

                if (c == '.' || c == '\0') {
                        /* Empty string, starting with period or two consecutive periods. */
                        if (lsize == 0) {
                                log_msg(LOG_DEFAULT, LVL_DEBUG, "Empty token");
                                return EINVAL;
                        }

                        if (lsize > DNS_LABEL_MAX_SIZE) {
                                /* Label too long */
                                log_msg(LOG_DEFAULT, LVL_DEBUG, "Label too long");
                                return EINVAL;
                        }

                        if (buf != NULL && pi < buf_size)
                                buf[pi] = (uint8_t)lsize;

                        lsize = 0;
                        pi = di;
                        ++di;

                        if (c == '\0')
                                break;
                } else {
                        if (buf != NULL && di < buf_size)
                                buf[di] = c;
                        ++di;
                        ++lsize;
                }
        }

        if (buf != NULL && pi < buf_size)
                buf[pi] = 0;

        *act_size = di;
        return EOK;
}

/** Decode DNS name.
 *
 * @param pdu   PDU from which we are decoding
 * @param boff  Starting offset within PDU
 * @param rname Place to return dynamically allocated string
 * @param eoff  Place to store end offset (offset after last decoded byte)
 */
errno_t dns_name_decode(dns_pdu_t *pdu, size_t boff, char **rname,
    size_t *eoff)
{
        uint8_t *bp;
        size_t bsize;
        size_t lsize;
        size_t i;
        size_t ptr;
        size_t eptr;
        char *name;
        char dbuf[2];
        errno_t rc;
        bool first;

        name = NULL;

        if (boff > pdu->size)
                return EINVAL;

        bp = pdu->data + boff;
        bsize = min(pdu->size - boff, DNS_NAME_MAX_SIZE);
        first = true;
        *eoff = 0;

        while (true) {
                if (bsize == 0) {
                        rc = EINVAL;
                        goto error;
                }

                lsize = *bp;
                ++bp;
                --bsize;

                if (lsize == 0)
                        break;

                if ((lsize & 0xc0) == 0xc0) {
                        /* Pointer */
                        if (bsize < 1) {
                                log_msg(LOG_DEFAULT, LVL_DEBUG, "Pointer- bsize < 1");
                                rc = EINVAL;
                                goto error;
                        }

                        ptr = dns_uint16_t_decode(bp - 1, bsize) & 0x3fff;
                        ++bp;
                        --bsize;

                        if (ptr >= (size_t)(bp - pdu->data)) {
                                log_msg(LOG_DEFAULT, LVL_DEBUG,
                                    "Pointer- forward ref %zu, pos=%zu",
                                    ptr, (size_t)(bp - pdu->data));
                                /* Forward reference */
                                rc = EINVAL;
                                goto error;
                        }

                        /*
                         * Make sure we will not decode any byte twice.
                         * XXX Is assumption correct?
                         */
                        eptr = bp - pdu->data;
                        /*
                         * This is where encoded name ends in terms where
                         * the message continues
                         */
                        if (*eoff == 0)
                                *eoff = eptr;

                        bp = pdu->data + ptr;
                        bsize = eptr - ptr;
                        continue;
                }

                if (lsize > bsize) {
                        rc = EINVAL;
                        goto error;
                }

                if (!first) {
                        rc = dns_dstr_ext(&name, ".");
                        if (rc != EOK) {
                                rc = ENOMEM;
                                goto error;
                        }
                }

                for (i = 0; i < lsize; i++) {
                        if (*bp < 32 || *bp >= 127) {
                                rc = EINVAL;
                                goto error;
                        }

                        dbuf[0] = *bp;
                        dbuf[1] = '\0';

                        rc = dns_dstr_ext(&name, dbuf);
                        if (rc != EOK) {
                                rc = ENOMEM;
                                goto error;
                        }
                        ++bp;
                        --bsize;
                }

                first = false;
        }

        *rname = name;
        if (*eoff == 0)
                *eoff = bp - pdu->data;
        return EOK;
error:
        free(name);
        return rc;
}

/** Decode unaligned big-endian 16-bit integer */
static uint16_t dns_uint16_t_decode(uint8_t *buf, size_t buf_size)
{
        assert(buf_size >= 2);

        return ((uint16_t)buf[0] << 8) + buf[1];
}

/** Encode unaligned big-endian 16-bit integer */
static void dns_uint16_t_encode(uint16_t w, uint8_t *buf, size_t buf_size)
{
        if (buf != NULL && buf_size >= 1)
                buf[0] = w >> 8;

        if (buf != NULL && buf_size >= 2)
                buf[1] = w & 0xff;
}

/** Decode unaligned big-endian 32-bit integer */
uint32_t dns_uint32_t_decode(uint8_t *buf, size_t buf_size)
{
        assert(buf_size >= 4);

        uint32_t w = ((uint32_t) buf[0] << 24) +
            ((uint32_t) buf[1] << 16) +
            ((uint32_t) buf[2] << 8) +
            buf[3];

        return w;
}

/** Decode unaligned big-endian 128-bit integer */
void dns_addr128_t_decode(uint8_t *buf, size_t buf_size, addr128_t addr)
{
        assert(buf_size >= 16);

        addr128_t_be2host(buf, addr);
}

/** Encode DNS question.
 *
 * Encode DNS question or measure the size of encoded question (with @a buf NULL,
 * and @a buf_size 0).
 *
 * @param question      Question to encode
 * @param buf           Buffer or NULL
 * @param buf_size      Buffer size or 0 if @a buf is NULL
 * @param act_size      Place to store actual encoded size
 */
static errno_t dns_question_encode(dns_question_t *question, uint8_t *buf,
    size_t buf_size, size_t *act_size)
{
        size_t name_size;
        size_t di;
        errno_t rc;

        rc = dns_name_encode(question->qname, buf, buf_size, &name_size);
        if (rc != EOK)
                return rc;

        *act_size = name_size + sizeof(uint16_t) + sizeof(uint16_t);
        if (buf == NULL)
                return EOK;

        di = name_size;

        dns_uint16_t_encode(question->qtype, buf + di, buf_size - di);
        di += sizeof(uint16_t);

        dns_uint16_t_encode(question->qclass, buf + di, buf_size - di);
        di += sizeof(uint16_t);

        return EOK;
}

/** Decode DNS question.
 *
 * @param pdu           PDU from which we are decoding
 * @param boff          Starting offset within PDU
 * @param rquestion     Place to return dynamically allocated question
 * @param eoff          Place to store end offset (offset after last decoded byte)
 */
static errno_t dns_question_decode(dns_pdu_t *pdu, size_t boff,
    dns_question_t **rquestion, size_t *eoff)
{
        dns_question_t *question;
        size_t name_eoff;
        errno_t rc;

        question = calloc(1, sizeof (dns_question_t));
        if (question == NULL)
                return ENOMEM;

        rc = dns_name_decode(pdu, boff, &question->qname, &name_eoff);
        if (rc != EOK) {
                log_msg(LOG_DEFAULT, LVL_DEBUG, "Error decoding name");
                free(question);
                return ENOMEM;
        }

        if (name_eoff + 2 * sizeof(uint16_t) > pdu->size) {
                free(question);
                return EINVAL;
        }

        question->qtype = dns_uint16_t_decode(pdu->data + name_eoff,
            pdu->size - name_eoff);
        question->qclass = dns_uint16_t_decode(pdu->data + sizeof(uint16_t) +
            name_eoff, pdu->size - sizeof(uint16_t) - name_eoff);
        *eoff = name_eoff + 2 * sizeof(uint16_t);

        *rquestion = question;
        return EOK;
}

/** Decode DNS resource record.
 *
 * @param pdu           PDU from which we are decoding
 * @param boff          Starting offset within PDU
 * @param retrr         Place to return dynamically allocated resource record
 * @param eoff          Place to store end offset (offset after last decoded byte)
 */
static errno_t dns_rr_decode(dns_pdu_t *pdu, size_t boff, dns_rr_t **retrr,
    size_t *eoff)
{
        dns_rr_t *rr;
        size_t name_eoff;
        uint8_t *bp;
        size_t bsz;
        size_t rdlength;
        errno_t rc;

        rr = calloc(1, sizeof(dns_rr_t));
        if (rr == NULL)
                return ENOMEM;

        rc = dns_name_decode(pdu, boff, &rr->name, &name_eoff);
        if (rc != EOK) {
                log_msg(LOG_DEFAULT, LVL_DEBUG, "dns_rr_decode: error decoding name");
                free(rr);
                return ENOMEM;
        }

        if (name_eoff + 2 * sizeof(uint16_t) > pdu->size) {
                free(rr->name);
                free(rr);
                log_msg(LOG_DEFAULT, LVL_DEBUG, "dns_rr_decode: error name_off");
                return EINVAL;
        }

        bp = pdu->data + name_eoff;
        bsz = pdu->size - name_eoff;

        if (bsz < 3 * sizeof(uint16_t) + sizeof(uint32_t)) {
                free(rr->name);
                free(rr);
                log_msg(LOG_DEFAULT, LVL_DEBUG, "dns_rr_decode: error bsz");
                return EINVAL;
        }

        rr->rtype = dns_uint16_t_decode(bp, bsz);
        bp += sizeof(uint16_t);
        bsz -= sizeof(uint16_t);

        rr->rclass = dns_uint16_t_decode(bp, bsz);
        bp += sizeof(uint16_t);
        bsz -= sizeof(uint16_t);

        rr->ttl = dns_uint32_t_decode(bp, bsz);
        bp += sizeof(uint32_t);
        bsz -= sizeof(uint32_t);

        log_msg(LOG_DEFAULT, LVL_DEBUG2, "dns_rr_decode: rtype=0x%x, rclass=0x%x, ttl=0x%x",
            rr->rtype, rr->rclass, rr->ttl);

        rdlength = dns_uint16_t_decode(bp, bsz);
        bp += sizeof(uint16_t);
        bsz -= sizeof(uint16_t);

        if (rdlength > bsz) {
                free(rr->name);
                free(rr);
                log_msg(LOG_DEFAULT, LVL_DEBUG, "dns_rr_decode: Error rdlength %zu > bsz %zu", rdlength, bsz);
                return EINVAL;
        }

        rr->rdata_size = rdlength;
        log_msg(LOG_DEFAULT, LVL_DEBUG2, "dns_rr_decode: rdlength=%zu", rdlength);
        rr->rdata = calloc(1, rdlength);
        if (rr->rdata == NULL) {
                free(rr->name);
                free(rr);
                log_msg(LOG_DEFAULT, LVL_DEBUG, "dns_rr_decode: Error memory");
                return ENOMEM;
        }

        memcpy(rr->rdata, bp, rdlength);
        rr->roff = bp - pdu->data;
        bp += rdlength;
        bsz -= rdlength;

        *eoff = bp - pdu->data;
        *retrr = rr;
        log_msg(LOG_DEFAULT, LVL_DEBUG2, "dns_rr_decode: done");
        return EOK;
}

/** Encode DNS message.
 *
 * @param msg   Message
 * @param rdata Place to store encoded data pointer
 * @param rsize Place to store encoded data size
 *
 * @return      EOK on success, EINVAL if message contains invalid data,
 *              ENOMEM if out of memory
 */
errno_t dns_message_encode(dns_message_t *msg, void **rdata, size_t *rsize)
{
        uint8_t *data;
        size_t size;
        dns_header_t hdr;
        size_t q_size = 0;
        size_t di;
        errno_t rc;

        hdr.id = host2uint16_t_be(msg->id);

        hdr.opbits = host2uint16_t_be(
            (msg->qr << OPB_QR) |
            (msg->opcode << OPB_OPCODE_l) |
            (msg->aa ? BIT_V(uint16_t, OPB_AA) : 0) |
            (msg->tc ? BIT_V(uint16_t, OPB_TC) : 0) |
            (msg->rd ? BIT_V(uint16_t, OPB_RD) : 0) |
            (msg->ra ? BIT_V(uint16_t, OPB_RA) : 0) |
            msg->rcode);

        hdr.qd_count = host2uint16_t_be(list_count(&msg->question));
        hdr.an_count = 0;
        hdr.ns_count = 0;
        hdr.ar_count = 0;

        size = sizeof(dns_header_t);

        list_foreach(msg->question, msg, dns_question_t, q) {
                rc = dns_question_encode(q, NULL, 0, &q_size);
                if (rc != EOK)
                        return rc;

                assert(q_size > 0);

                size += q_size;
        }

        data = calloc(1, size);
        if (data == NULL)
                return ENOMEM;

        memcpy(data, &hdr, sizeof(dns_header_t));
        di = sizeof(dns_header_t);

        list_foreach(msg->question, msg, dns_question_t, q) {
                rc = dns_question_encode(q, data + di, size - di, &q_size);
                if (rc != EOK) {
                        assert(rc == ENOMEM || rc == EINVAL);
                        free(data);
                        return rc;
                }

                assert(q_size > 0);

                di += q_size;
        }

        *rdata = data;
        *rsize = size;
        return EOK;
}

/** Decode DNS message.
 *
 * @param data  Encoded PDU data
 * @param size  Encoded PDU size
 * @param rmsg  Place to store pointer to decoded message
 *
 * @return      EOK on success, EINVAL if message contains invalid data,
 *              ENOMEM if out of memory
 */
errno_t dns_message_decode(void *data, size_t size, dns_message_t **rmsg)
{
        dns_message_t *msg;
        dns_header_t *hdr;
        size_t doff;
        size_t field_eoff;
        dns_question_t *question;
        dns_rr_t *rr;
        size_t qd_count;
        size_t an_count;
        size_t i;
        errno_t rc;

        msg = dns_message_new();
        if (msg == NULL)
                return ENOMEM;

        if (size < sizeof(dns_header_t)) {
                rc = EINVAL;
                goto error;
        }

        /* Store a copy of raw message data for string decompression */

        msg->pdu.data = malloc(size);
        if (msg->pdu.data == NULL) {
                rc = ENOMEM;
                goto error;
        }

        memcpy(msg->pdu.data, data, size);
        msg->pdu.size = size;
        log_msg(LOG_DEFAULT, LVL_DEBUG2, "dns_message_decode: pdu->data = %p, "
            "pdu->size=%zu", msg->pdu.data, msg->pdu.size);

        hdr = data;

        msg->id = uint16_t_be2host(hdr->id);
        msg->qr = BIT_RANGE_EXTRACT(uint16_t, OPB_QR, OPB_QR, hdr->opbits);
        msg->opcode = BIT_RANGE_EXTRACT(uint16_t, OPB_OPCODE_h, OPB_OPCODE_l,
            hdr->opbits);
        msg->aa = BIT_RANGE_EXTRACT(uint16_t, OPB_AA, OPB_AA, hdr->opbits);
        msg->tc = BIT_RANGE_EXTRACT(uint16_t, OPB_TC, OPB_TC, hdr->opbits);
        msg->rd = BIT_RANGE_EXTRACT(uint16_t, OPB_RD, OPB_RD, hdr->opbits);
        msg->ra = BIT_RANGE_EXTRACT(uint16_t, OPB_RA, OPB_RA, hdr->opbits);
        msg->rcode = BIT_RANGE_EXTRACT(uint16_t, OPB_RCODE_h, OPB_RCODE_l,
            hdr->opbits);

        doff = sizeof(dns_header_t);

        qd_count = uint16_t_be2host(hdr->qd_count);
        log_msg(LOG_DEFAULT, LVL_DEBUG2, "qd_count=%zu", qd_count);

        for (i = 0; i < qd_count; i++) {
                rc = dns_question_decode(&msg->pdu, doff, &question, &field_eoff);
                if (rc != EOK) {
                        log_msg(LOG_DEFAULT, LVL_DEBUG, "error decoding question");
                        goto error;
                }

                list_append(&question->msg, &msg->question);
                doff = field_eoff;
        }

        an_count = uint16_t_be2host(hdr->an_count);
        log_msg(LOG_DEFAULT, LVL_DEBUG2, "an_count=%zu", an_count);

        for (i = 0; i < an_count; i++) {
                rc = dns_rr_decode(&msg->pdu, doff, &rr, &field_eoff);
                if (rc != EOK) {
                        log_msg(LOG_DEFAULT, LVL_DEBUG, "Error decoding answer");
                        goto error;
                }

                list_append(&rr->msg, &msg->answer);
                doff = field_eoff;
        }

        *rmsg = msg;
        return EOK;
error:
        dns_message_destroy(msg);
        return rc;
}

/** Destroy question. */
static void dns_question_destroy(dns_question_t *question)
{
        free(question->qname);
        free(question);
}

/** Destroy resource record. */
static void dns_rr_destroy(dns_rr_t *rr)
{
        free(rr->name);
        free(rr->rdata);
        free(rr);
}

/** Create new empty message. */
dns_message_t *dns_message_new(void)
{
        dns_message_t *msg;

        msg = calloc(1, sizeof(dns_message_t));
        if (msg == NULL)
                return NULL;

        list_initialize(&msg->question);
        list_initialize(&msg->answer);
        list_initialize(&msg->authority);
        list_initialize(&msg->additional);

        return msg;
}

/** Destroy message. */
void dns_message_destroy(dns_message_t *msg)
{
        link_t *link;
        dns_question_t *question;
        dns_rr_t *rr;

        while (!list_empty(&msg->question)) {
                link = list_first(&msg->question);
                question = list_get_instance(link, dns_question_t, msg);
                list_remove(&question->msg);
                dns_question_destroy(question);
        }

        while (!list_empty(&msg->answer)) {
                link = list_first(&msg->answer);
                rr = list_get_instance(link, dns_rr_t, msg);
                list_remove(&rr->msg);
                dns_rr_destroy(rr);
        }

        while (!list_empty(&msg->authority)) {
                link = list_first(&msg->authority);
                rr = list_get_instance(link, dns_rr_t, msg);
                list_remove(&rr->msg);
                dns_rr_destroy(rr);
        }

        while (!list_empty(&msg->additional)) {
                link = list_first(&msg->additional);
                rr = list_get_instance(link, dns_rr_t, msg);
                list_remove(&rr->msg);
                dns_rr_destroy(rr);
        }

        free(msg->pdu.data);
        free(msg);
}

/** @}
 */