/***************************************************************************

 *                                  _   _ ____  _

 *  Project                     ___| | | |  _ \| |

 *                             / __| | | | |_) | |

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.

 *

 * This software is licensed as described in the file COPYING, which

 * you should have received as part of this distribution. The terms

 * are also available at https://curl.se/docs/copyright.html.

 *

 * You may opt to use, copy, modify, merge, publish, distribute and/or sell

 * copies of the Software, and permit persons to whom the Software is

 * furnished to do so, under the terms of the COPYING file.

 *

 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY

 * KIND, either express or implied.

 *

 * SPDX-License-Identifier: curl

 *

 ***************************************************************************/

#include "curl_setup.h"

#ifndef CURL_DISABLE_DOH

#include "urldata.h"

#include "curl_addrinfo.h"

#include "doh.h"

#include "curl_trc.h"

#include "httpsrr.h"

#include "multiif.h"

#include "url.h"

#include "connect.h"

#include "curlx/strdup.h"

#include "curlx/dynbuf.h"

#include "escape.h"  /* for Curl_hexencode() */

#include "urlapi-int.h"

#define DNS_CLASS_IN 0x01

#ifdef CURLVERBOSE

static const char * const errors[] = {

  "",

  "Bad label",

  "Out of range",

  "Label loop",

  "Too small",

  "Out of memory",

  "RDATA length",

  "Malformat",

  "Bad RCODE",

  "Unexpected TYPE",

  "Unexpected CLASS",

  "No content",

  "Bad ID",

  "Name too long"

};

static const char *doh_strerror(DOHcode code)

{

  if((code >= DOH_OK) && (code <= DOH_DNS_NAME_TOO_LONG))

    return errors[code];

  return "bad error code";

}

#endif /* CURLVERBOSE */

/* @unittest 1655

 */

UNITTEST DOHcode doh_req_encode(const char *host,

                                DNStype dnstype,

                                unsigned char *dnsp, /* buffer */

                                size_t len,   /* buffer size */

                                size_t *olen) /* output length */

{

  const size_t hostlen = strlen(host);

  unsigned char *orig = dnsp;

  const char *hostp = host;

  /* The expected output length is 16 bytes more than the length of

   * the QNAME-encoding of the hostname.

   *

   * A valid DNS name may not contain a zero-length label, except at

   * the end. For this reason, a name beginning with a dot, or

   * containing a sequence of two or more consecutive dots, is invalid

   * and cannot be encoded as a QNAME.

   *

   * If the hostname ends with a trailing dot, the corresponding

   * QNAME-encoding is one byte longer than the hostname. If (as is

   * also valid) the hostname is shortened by the omission of the

   * trailing dot, then its QNAME-encoding will be two bytes longer

   * than the hostname.

   *

   * Each [ label, dot ] pair is encoded as [ length, label ],

   * preserving overall length. A final [ label ] without a dot is

   * also encoded as [ length, label ], increasing overall length

   * by one. The encoding is completed by appending a zero byte,

   * representing the zero-length root label, again increasing

   * the overall length by one.

   */

  size_t expected_len;

  DEBUGASSERT(hostlen);

  expected_len = 12 + 1 + hostlen + 4;

  if(host[hostlen - 1] != '.')

    expected_len++;

  if(expected_len > DOH_MAX_DNSREQ_SIZE)

    return DOH_DNS_NAME_TOO_LONG;

  if(len < expected_len)

    return DOH_TOO_SMALL_BUFFER;

  *dnsp++ = 0; /* 16-bit id */

  *dnsp++ = 0;

  *dnsp++ = 0x01; /* |QR|   Opcode  |AA|TC|RD| Set the RD bit */

  *dnsp++ = '\0'; /* |RA|   Z    |   RCODE   |                */

  *dnsp++ = '\0';

  *dnsp++ = 1;    /* QDCOUNT (number of entries in the question section) */

  *dnsp++ = '\0';

  *dnsp++ = '\0'; /* ANCOUNT */

  *dnsp++ = '\0';

  *dnsp++ = '\0'; /* NSCOUNT */

  *dnsp++ = '\0';

  *dnsp++ = '\0'; /* ARCOUNT */

  /* encode each label and store it in the QNAME */

  while(*hostp) {

    size_t labellen;

    const char *dot = strchr(hostp, '.');

    if(dot)

      labellen = dot - hostp;

    else

      labellen = strlen(hostp);

    if((labellen > 63) || (!labellen)) {

      /* label is too long or too short, error out */

      *olen = 0;

      return DOH_DNS_BAD_LABEL;

    }

    /* label is non-empty, process it */

    *dnsp++ = (unsigned char)labellen;

    memcpy(dnsp, hostp, labellen);

    dnsp += labellen;

    hostp += labellen;

    /* advance past dot, but only if there is one */

    if(dot)

      hostp++;

  } /* next label */

  *dnsp++ = 0; /* append zero-length label for root */

  /* There are assigned TYPE codes beyond 255: use range [1..65535] */

  *dnsp++ = (unsigned char)(255 & (dnstype >> 8)); /* upper 8-bit TYPE */

  *dnsp++ = (unsigned char)(255 & dnstype);        /* lower 8-bit TYPE */

  *dnsp++ = '\0'; /* upper 8-bit CLASS */

  *dnsp++ = DNS_CLASS_IN; /* IN - "the Internet" */

  *olen = dnsp - orig;

  /* verify that our estimation of length is valid, since

   * this has led to buffer overflows in this function */

  DEBUGASSERT(*olen == expected_len);

  return DOH_OK;

}

static size_t doh_probe_write_cb(char *contents, size_t size, size_t nmemb,

                                 void *userp)

{

  size_t realsize = size * nmemb;

  struct Curl_easy *data = userp;

  struct doh_request *doh_req = Curl_meta_get(data, CURL_EZM_DOH_PROBE);

  if(!doh_req)

    return CURL_WRITEFUNC_ERROR;

  if(curlx_dyn_addn(&doh_req->resp_body, contents, realsize))

    return 0;

  return realsize;

}

#if defined(USE_HTTPSRR) && defined(DEBUGBUILD) && defined(CURLVERBOSE)

/* doh_print_buf truncates if the hex string will be more than this */

#define LOCAL_PB_HEXMAX 400

static void doh_print_buf(struct Curl_easy *data,

                          const char *prefix,

                          unsigned char *buf, size_t len)

{

  unsigned char hexstr[LOCAL_PB_HEXMAX];

  size_t hlen = LOCAL_PB_HEXMAX;

  bool truncated = FALSE;

  if(len > (LOCAL_PB_HEXMAX / 2))

    truncated = TRUE;

  Curl_hexencode(buf, len, hexstr, hlen);

  if(!truncated)

    infof(data, "%s: len=%d, val=%s", prefix, (int)len, hexstr);

  else

    infof(data, "%s: len=%d (truncated)val=%s", prefix, (int)len, hexstr);

}

#endif

/* called from multi when a sub transfer, e.g. doh probe, is done.

 * This looks up the the probe response at its meta CURL_EZM_DOH_PROBE

 * and copies the response body over to the struct at the master's

 * meta at CURL_EZM_DOH_MASTER. */

static void doh_probe_done(struct Curl_easy *data,

                           struct Curl_easy *doh, CURLcode result)

{

  struct doh_probes *dohp = data->state.async.doh;

  DEBUGASSERT(dohp);

  if(dohp) {

    struct doh_request *doh_req = Curl_meta_get(doh, CURL_EZM_DOH_PROBE);

    int i;

    for(i = 0; i < DOH_SLOT_COUNT; ++i) {

      if(dohp->probe_resp[i].probe_mid == doh->mid)

        break;

    }

    if(i >= DOH_SLOT_COUNT) {

      failf(data, "unknown sub request done");

      return;

    }

    dohp->pending--;

    infof(doh, "a DoH request is completed, %u to go", dohp->pending);

    dohp->probe_resp[i].result = result;

    /* We expect either the meta data still to exist or the sub request

     * to have already failed. */

    DEBUGASSERT(doh_req || result);

    if(doh_req) {

      if(!result) {

        dohp->probe_resp[i].dnstype = doh_req->dnstype;

        result = curlx_dyn_addn(&dohp->probe_resp[i].body,

                                curlx_dyn_ptr(&doh_req->resp_body),

                                curlx_dyn_len(&doh_req->resp_body));

        curlx_dyn_free(&doh_req->resp_body);

      }

      Curl_meta_remove(doh, CURL_EZM_DOH_PROBE);

    }

    if(result)

      infof(doh, "DoH request %s", curl_easy_strerror(result));

    if(!dohp->pending) {

      /* DoH completed, run the transfer picking up the results */

      Curl_multi_mark_dirty(data);

    }

  }

}

static void doh_probe_dtor(void *key, size_t klen, void *e)

{

  (void)key;

  (void)klen;

  if(e) {

    struct doh_request *doh_req = e;

    curl_slist_free_all(doh_req->req_hds);

    curlx_dyn_free(&doh_req->resp_body);

    curlx_free(e);

  }

}

#define ERROR_CHECK_SETOPT(x, y)                        \

  do {                                                  \

    result = curl_easy_setopt((CURL *)doh, x, y);       \

    if(result &&                                        \

       result != CURLE_NOT_BUILT_IN &&                  \

       result != CURLE_UNKNOWN_OPTION)                  \

      goto error;                                       \

  } while(0)

static CURLcode doh_probe_run(struct Curl_easy *data,

                              DNStype dnstype,

                              const char *host,

                              const char *url, CURLM *multi,

                              uint32_t *pmid)

{

  struct Curl_easy *doh = NULL;

  CURLcode result = CURLE_OK;

  timediff_t timeout_ms;

  struct doh_request *doh_req;

  DOHcode d;

  *pmid = UINT32_MAX;

  doh_req = curlx_calloc(1, sizeof(*doh_req));

  if(!doh_req)

    return CURLE_OUT_OF_MEMORY;

  doh_req->dnstype = dnstype;

  curlx_dyn_init(&doh_req->resp_body, DYN_DOH_RESPONSE);

  d = doh_req_encode(host, dnstype, doh_req->req_body,

                     sizeof(doh_req->req_body),

                     &doh_req->req_body_len);

  if(d) {

    failf(data, "Failed to encode DoH packet [%d]", d);

    result = CURLE_OUT_OF_MEMORY;

    goto error;

  }

  timeout_ms = Curl_timeleft_ms(data);

  if(timeout_ms < 0) {

    result = CURLE_OPERATION_TIMEDOUT;

    goto error;

  }

  doh_req->req_hds =

    curl_slist_append(NULL, "Content-Type: application/dns-message");

  if(!doh_req->req_hds) {

    result = CURLE_OUT_OF_MEMORY;

    goto error;

  }

  /* Curl_open() is the internal version of curl_easy_init() */

  result = Curl_open(&doh);

  if(result)

    goto error;

  /* pass in the struct pointer via a local variable to please coverity and

     the gcc typecheck helpers */

  VERBOSE(doh->state.feat = &Curl_trc_feat_dns);

  ERROR_CHECK_SETOPT(CURLOPT_URL, url);

  ERROR_CHECK_SETOPT(CURLOPT_DEFAULT_PROTOCOL, "https");

  ERROR_CHECK_SETOPT(CURLOPT_WRITEFUNCTION, doh_probe_write_cb);

  ERROR_CHECK_SETOPT(CURLOPT_WRITEDATA, doh);

  ERROR_CHECK_SETOPT(CURLOPT_POSTFIELDS, doh_req->req_body);

  ERROR_CHECK_SETOPT(CURLOPT_POSTFIELDSIZE, (long)doh_req->req_body_len);

  ERROR_CHECK_SETOPT(CURLOPT_HTTPHEADER, doh_req->req_hds);

#ifdef USE_HTTP2

  ERROR_CHECK_SETOPT(CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2TLS);

  ERROR_CHECK_SETOPT(CURLOPT_PIPEWAIT, 1L);

#endif

#ifndef DEBUGBUILD

  /* enforce HTTPS if not debug */

  ERROR_CHECK_SETOPT(CURLOPT_PROTOCOLS, CURLPROTO_HTTPS);

#else

  /* in debug mode, also allow http */

  ERROR_CHECK_SETOPT(CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);

#endif

  ERROR_CHECK_SETOPT(CURLOPT_TIMEOUT_MS, (long)timeout_ms);

  ERROR_CHECK_SETOPT(CURLOPT_SHARE, (CURLSH *)data->share);

  if(data->set.err && data->set.err != stderr)

    ERROR_CHECK_SETOPT(CURLOPT_STDERR, data->set.err);

  if(Curl_trc_ft_is_verbose(data, &Curl_trc_feat_dns))

    ERROR_CHECK_SETOPT(CURLOPT_VERBOSE, 1L);

  if(data->set.no_signal)

    ERROR_CHECK_SETOPT(CURLOPT_NOSIGNAL, 1L);

  ERROR_CHECK_SETOPT(CURLOPT_SSL_VERIFYHOST,

                     data->set.doh_verifyhost ? 2L : 0L);

  ERROR_CHECK_SETOPT(CURLOPT_SSL_VERIFYPEER,

                     data->set.doh_verifypeer ? 1L : 0L);

  ERROR_CHECK_SETOPT(CURLOPT_SSL_VERIFYSTATUS,

                     data->set.doh_verifystatus ? 1L : 0L);

  /* Inherit *some* SSL options from the user's transfer. This is a

     best-guess as to which options are needed for compatibility. #3661

     Note DoH does not inherit the user's proxy server so proxy SSL settings

     have no effect and are not inherited. If that changes then two new

     options should be added to check doh proxy insecure separately,

     CURLOPT_DOH_PROXY_SSL_VERIFYHOST and CURLOPT_DOH_PROXY_SSL_VERIFYPEER.

     */

  doh->set.ssl.custom_cafile = data->set.ssl.custom_cafile;

  doh->set.ssl.custom_capath = data->set.ssl.custom_capath;

  doh->set.ssl.custom_cablob = data->set.ssl.custom_cablob;

  if(data->set.str[STRING_SSL_CAFILE]) {

    ERROR_CHECK_SETOPT(CURLOPT_CAINFO, data->set.str[STRING_SSL_CAFILE]);

  }

  if(data->set.blobs[BLOB_CAINFO]) {

    ERROR_CHECK_SETOPT(CURLOPT_CAINFO_BLOB, data->set.blobs[BLOB_CAINFO]);

  }

  if(data->set.str[STRING_SSL_CAPATH]) {

    ERROR_CHECK_SETOPT(CURLOPT_CAPATH, data->set.str[STRING_SSL_CAPATH]);

  }

  if(data->set.str[STRING_SSL_CRLFILE]) {

    ERROR_CHECK_SETOPT(CURLOPT_CRLFILE, data->set.str[STRING_SSL_CRLFILE]);

  }

  if(data->set.ssl.certinfo)

    ERROR_CHECK_SETOPT(CURLOPT_CERTINFO, 1L);

  if(data->set.ssl.fsslctx)

    ERROR_CHECK_SETOPT(CURLOPT_SSL_CTX_FUNCTION, data->set.ssl.fsslctx);

  if(data->set.ssl.fsslctxp)

    ERROR_CHECK_SETOPT(CURLOPT_SSL_CTX_DATA, data->set.ssl.fsslctxp);

  if(data->set.fdebug)

    ERROR_CHECK_SETOPT(CURLOPT_DEBUGFUNCTION, data->set.fdebug);

  if(data->set.debugdata)

    ERROR_CHECK_SETOPT(CURLOPT_DEBUGDATA, data->set.debugdata);

  if(data->set.str[STRING_SSL_EC_CURVES]) {

    ERROR_CHECK_SETOPT(CURLOPT_SSL_EC_CURVES,

                       data->set.str[STRING_SSL_EC_CURVES]);

  }

  (void)curl_easy_setopt(doh, CURLOPT_SSL_OPTIONS,

                         (long)data->set.ssl.primary.ssl_options);

  doh->state.internal = TRUE;

  doh->master_mid = data->mid; /* master transfer of this one */

  result = Curl_meta_set(doh, CURL_EZM_DOH_PROBE, doh_req, doh_probe_dtor);

  doh_req = NULL; /* call took ownership */

  if(result)

    goto error;

  /* DoH handles must not inherit private_data. The handles may be passed to

     the user via callbacks and the user will be able to identify them as

     internal handles because private data is not set. The user can then set

     private_data via CURLOPT_PRIVATE if they so choose. */

  DEBUGASSERT(!doh->set.private_data);

  if(curl_multi_add_handle(multi, doh))

    goto error;

  *pmid = doh->mid;

  return CURLE_OK;

error:

  Curl_close(&doh);

  if(doh_req)

    doh_probe_dtor(NULL, 0, doh_req);

  return result;

}

/*

 * Curl_doh() starts a name resolve using DoH. It resolves a name and returns

 * a 'Curl_addrinfo *' with the address information.

 */

CURLcode Curl_doh(struct Curl_easy *data, const char *hostname,

                  int port, int ip_version)

{

  CURLcode result = CURLE_OK;

  struct doh_probes *dohp = NULL;

  struct connectdata *conn = data->conn;

  size_t i;

  DEBUGASSERT(conn);

  DEBUGASSERT(!data->state.async.doh);

  DEBUGASSERT(hostname && hostname[0]);

  if(data->state.async.doh)

    Curl_doh_cleanup(data);

  data->state.async.done = FALSE;

  data->state.async.port = port;

  data->state.async.ip_version = ip_version;

  data->state.async.hostname = curlx_strdup(hostname);

  if(!data->state.async.hostname)

    return CURLE_OUT_OF_MEMORY;

  /* start clean, consider allocating this struct on demand */

  data->state.async.doh = dohp = curlx_calloc(1, sizeof(struct doh_probes));

  if(!dohp)

    return CURLE_OUT_OF_MEMORY;

  for(i = 0; i < DOH_SLOT_COUNT; ++i) {

    dohp->probe_resp[i].probe_mid = UINT32_MAX;

    curlx_dyn_init(&dohp->probe_resp[i].body, DYN_DOH_RESPONSE);

  }

  conn->bits.doh = TRUE;

  dohp->host = data->state.async.hostname;

  dohp->port = data->state.async.port;

  /* We are making sub easy handles and want to be called back when

   * one is done. */

  data->sub_xfer_done = doh_probe_done;

  /* create IPv4 DoH request */

  result = doh_probe_run(data, CURL_DNS_TYPE_A,

                         hostname, data->set.str[STRING_DOH],

                         data->multi,

                         &dohp->probe_resp[DOH_SLOT_IPV4].probe_mid);

  if(result)

    goto error;

  dohp->pending++;

#ifdef USE_IPV6

  if((ip_version != CURL_IPRESOLVE_V4) && Curl_ipv6works(data)) {

    /* create IPv6 DoH request */

    result = doh_probe_run(data, CURL_DNS_TYPE_AAAA,

                           hostname, data->set.str[STRING_DOH],

                           data->multi,

                           &dohp->probe_resp[DOH_SLOT_IPV6].probe_mid);

    if(result)

      goto error;

    dohp->pending++;

  }

#endif

#ifdef USE_HTTPSRR

  if(conn->scheme->protocol & PROTO_FAMILY_HTTP) {

    /* Only use HTTPS RR for HTTP(S) transfers */

    char *qname = NULL;

    if(port != PORT_HTTPS) {

      qname = curl_maprintf("_%d._https.%s", port, hostname);

      if(!qname)

        goto error;

    }

    result = doh_probe_run(data, CURL_DNS_TYPE_HTTPS,

                           qname ? qname : hostname, data->set.str[STRING_DOH],

                           data->multi,

                           &dohp->probe_resp[DOH_SLOT_HTTPS_RR].probe_mid);

    curlx_free(qname);

    if(result)

      goto error;

    dohp->pending++;

  }

#endif

  return CURLE_OK;

error:

  Curl_doh_cleanup(data);

  return result;

}

static DOHcode doh_skipqname(const unsigned char *doh, size_t dohlen,

                             unsigned int *indexp)

{

  unsigned char length;

  do {

    if(dohlen < (*indexp + 1))

      return DOH_DNS_OUT_OF_RANGE;

    length = doh[*indexp];

    if((length & 0xc0) == 0xc0) {

      /* name pointer, advance over it and be done */

      if(dohlen < (*indexp + 2))

        return DOH_DNS_OUT_OF_RANGE;

      *indexp += 2;

      break;

    }

    if(length & 0xc0)

      return DOH_DNS_BAD_LABEL;

    if(dohlen < (*indexp + 1 + length))

      return DOH_DNS_OUT_OF_RANGE;

    *indexp += (unsigned int)(1 + length);

  } while(length);

  return DOH_OK;

}

static unsigned short doh_get16bit(const unsigned char *doh,

                                   unsigned int index)

{

  return (unsigned short)((doh[index] << 8) | doh[index + 1]);

}

static unsigned int doh_get32bit(const unsigned char *doh, unsigned int index)

{

  /* make clang and gcc optimize this to bswap by incrementing

     the pointer first. */

  doh += index;

  /* avoid undefined behavior by casting to unsigned before shifting

     24 bits, possibly into the sign bit. codegen is same, but

     ub sanitizer will not be upset */

  return ((unsigned)doh[0] << 24) | ((unsigned)doh[1] << 16) |

         ((unsigned)doh[2] << 8) | doh[3];

}

static void doh_store_a(const unsigned char *doh, int index,

                        struct dohentry *d)

{

  /* silently ignore addresses over the limit */

  if(d->numaddr < DOH_MAX_ADDR) {

    struct dohaddr *a = &d->addr[d->numaddr];

    a->type = CURL_DNS_TYPE_A;

    memcpy(&a->ip.v4, &doh[index], 4);

    d->numaddr++;

  }

}

static void doh_store_aaaa(const unsigned char *doh, int index,

                           struct dohentry *d)

{

  /* silently ignore addresses over the limit */

  if(d->numaddr < DOH_MAX_ADDR) {

    struct dohaddr *a = &d->addr[d->numaddr];

    a->type = CURL_DNS_TYPE_AAAA;

    memcpy(&a->ip.v6, &doh[index], 16);

    d->numaddr++;

  }

}

#ifdef USE_HTTPSRR

static DOHcode doh_store_https(const unsigned char *doh, int index,

                               struct dohentry *d, uint16_t len)

{

  /* silently ignore RRs over the limit */

  if(d->numhttps_rrs < DOH_MAX_HTTPS) {

    struct dohhttps_rr *h = &d->https_rrs[d->numhttps_rrs];

    h->val = curlx_memdup(&doh[index], len);

    if(!h->val)

      return DOH_OUT_OF_MEM;

    h->len = len;

    d->numhttps_rrs++;

  }

  return DOH_OK;

}

#endif

static DOHcode doh_store_cname(const unsigned char *doh, size_t dohlen,

                               unsigned int index, struct dohentry *d)

{

  struct dynbuf *c;

  unsigned int loop = 128; /* a valid DNS name can never loop this much */

  unsigned char length;

  if(d->numcname == DOH_MAX_CNAME)

    return DOH_OK; /* skip! */

  c = &d->cname[d->numcname++];

  do {

    if(index >= dohlen)

      return DOH_DNS_OUT_OF_RANGE;

    length = doh[index];

    if((length & 0xc0) == 0xc0) {

      int newpos;

      /* name pointer, get the new offset (14 bits) */

      if((index + 1) >= dohlen)

        return DOH_DNS_OUT_OF_RANGE;

      /* move to the new index */

      newpos = (length & 0x3f) << 8 | doh[index + 1];

      index = (unsigned int)newpos;

      continue;

    }

    else if(length & 0xc0)

      return DOH_DNS_BAD_LABEL; /* bad input */

    else

      index++;

    if(length) {

      if(curlx_dyn_len(c)) {

        if(curlx_dyn_addn(c, STRCONST(".")))

          return DOH_OUT_OF_MEM;

      }

      if((index + length) > dohlen)

        return DOH_DNS_BAD_LABEL;

      if(curlx_dyn_addn(c, &doh[index], length))

        return DOH_OUT_OF_MEM;

      index += length;

    }

  } while(length && --loop);

  if(!loop)

    return DOH_DNS_LABEL_LOOP;

  return DOH_OK;

}

static DOHcode doh_rdata(const unsigned char *doh,

                         size_t dohlen,

                         unsigned short rdlength,

                         unsigned short type,

                         int index,

                         struct dohentry *d)

{

  /* RDATA

     - A (TYPE 1): 4 bytes

     - AAAA (TYPE 28): 16 bytes

     - NS (TYPE 2): N bytes

     - HTTPS (TYPE 65): N bytes */

  DOHcode rc;

  switch(type) {

  case CURL_DNS_TYPE_A:

    if(rdlength != 4)

      return DOH_DNS_RDATA_LEN;

    doh_store_a(doh, index, d);

    break;

  case CURL_DNS_TYPE_AAAA:

    if(rdlength != 16)

      return DOH_DNS_RDATA_LEN;

    doh_store_aaaa(doh, index, d);

    break;

#ifdef USE_HTTPSRR

  case CURL_DNS_TYPE_HTTPS:

    rc = doh_store_https(doh, index, d, rdlength);

    if(rc)

      return rc;

    break;

#endif

  case CURL_DNS_TYPE_CNAME:

    rc = doh_store_cname(doh, dohlen, (unsigned int)index, d);

    if(rc)

      return rc;

    break;

  case CURL_DNS_TYPE_DNAME:

    /* explicit for clarity; skip; rely on synthesized CNAME */

    break;

  default:

    /* unsupported type, skip it */

    break;

  }

  return DOH_OK;

}

UNITTEST void de_init(struct dohentry *de)

{

  int i;

  memset(de, 0, sizeof(*de));

  de->ttl = INT_MAX;

  for(i = 0; i < DOH_MAX_CNAME; i++)

    curlx_dyn_init(&de->cname[i], DYN_DOH_CNAME);

}

UNITTEST DOHcode doh_resp_decode(const unsigned char *doh,

                                 size_t dohlen,

                                 DNStype dnstype,

                                 struct dohentry *d)

{

  unsigned char rcode;

  unsigned short qdcount;

  unsigned short ancount;

  unsigned short type = 0;

  unsigned short rdlength;

  unsigned short nscount;

  unsigned short arcount;

  unsigned int index = 12;

  DOHcode rc;

  if(dohlen < 12)

    return DOH_TOO_SMALL_BUFFER; /* too small */

  if(!doh || doh[0] || doh[1])

    return DOH_DNS_BAD_ID; /* bad ID */

  rcode = doh[3] & 0x0f;

  if(rcode)

    return DOH_DNS_BAD_RCODE; /* bad rcode */

  qdcount = doh_get16bit(doh, 4);

  while(qdcount) {

    rc = doh_skipqname(doh, dohlen, &index);

    if(rc)

      return rc; /* bad qname */

    if(dohlen < (index + 4))

      return DOH_DNS_OUT_OF_RANGE;

    index += 4; /* skip question's type and class */

    qdcount--;

  }

  ancount = doh_get16bit(doh, 6);

  while(ancount) {

    unsigned short dnsclass;

    unsigned int ttl;

    rc = doh_skipqname(doh, dohlen, &index);

    if(rc)

      return rc; /* bad qname */

    if(dohlen < (index + 2))

      return DOH_DNS_OUT_OF_RANGE;

    type = doh_get16bit(doh, index);

    if((type != CURL_DNS_TYPE_CNAME) &&  /* may be synthesized from DNAME */

       (type != CURL_DNS_TYPE_DNAME) &&  /* if present, accept and ignore */

       (type != dnstype))

      /* Not the same type as was asked for nor CNAME nor DNAME */

      return DOH_DNS_UNEXPECTED_TYPE;

    index += 2;

    if(dohlen < (index + 2))

      return DOH_DNS_OUT_OF_RANGE;

    dnsclass = doh_get16bit(doh, index);

    if(DNS_CLASS_IN != dnsclass)

      return DOH_DNS_UNEXPECTED_CLASS; /* unsupported */

    index += 2;

    if(dohlen < (index + 4))

      return DOH_DNS_OUT_OF_RANGE;

    ttl = doh_get32bit(doh, index);

    if(ttl < d->ttl)

      d->ttl = ttl;

    index += 4;

    if(dohlen < (index + 2))

      return DOH_DNS_OUT_OF_RANGE;

    rdlength = doh_get16bit(doh, index);

    index += 2;

    if(dohlen < (index + rdlength))

      return DOH_DNS_OUT_OF_RANGE;

    rc = doh_rdata(doh, dohlen, rdlength, type, (int)index, d);

    if(rc)

      return rc; /* bad doh_rdata */

    index += rdlength;

    ancount--;

  }

  nscount = doh_get16bit(doh, 8);

  while(nscount) {

    rc = doh_skipqname(doh, dohlen, &index);

    if(rc)

      return rc; /* bad qname */

    if(dohlen < (index + 8))

      return DOH_DNS_OUT_OF_RANGE;

    index += 2 + 2 + 4; /* type, dnsclass and ttl */

    if(dohlen < (index + 2))

      return DOH_DNS_OUT_OF_RANGE;

    rdlength = doh_get16bit(doh, index);

    index += 2;

    if(dohlen < (index + rdlength))

      return DOH_DNS_OUT_OF_RANGE;

    index += rdlength;

    nscount--;

  }

  arcount = doh_get16bit(doh, 10);

  while(arcount) {

    rc = doh_skipqname(doh, dohlen, &index);

    if(rc)

      return rc; /* bad qname */

    if(dohlen < (index + 8))

      return DOH_DNS_OUT_OF_RANGE;

    index += 2 + 2 + 4; /* type, dnsclass and ttl */

    if(dohlen < (index + 2))

      return DOH_DNS_OUT_OF_RANGE;

    rdlength = doh_get16bit(doh, index);

    index += 2;

    if(dohlen < (index + rdlength))

      return DOH_DNS_OUT_OF_RANGE;

    index += rdlength;

    arcount--;

  }

  if(index != dohlen)

    return DOH_DNS_MALFORMAT; /* something is wrong */

#ifdef USE_HTTTPS

  if((type != CURL_DNS_TYPE_NS) && !d->numcname && !d->numaddr &&

     !d->numhttps_rrs)

#else

  if((type != CURL_DNS_TYPE_NS) && !d->numcname && !d->numaddr)

#endif

    /* nothing stored! */

    return DOH_NO_CONTENT;

  return DOH_OK; /* ok */

}

#ifdef CURLVERBOSE

static void doh_show(struct Curl_easy *data,

                     const struct dohentry *d)

{

  int i;

  infof(data, "[DoH] TTL: %u seconds", d->ttl);

  for(i = 0; i < d->numaddr; i++) {

    const struct dohaddr *a = &d->addr[i];

    if(a->type == CURL_DNS_TYPE_A) {

      infof(data, "[DoH] A: %u.%u.%u.%u",

            a->ip.v4[0], a->ip.v4[1],

            a->ip.v4[2], a->ip.v4[3]);

    }

    else if(a->type == CURL_DNS_TYPE_AAAA) {

      int j;

      char buffer[128] = "[DoH] AAAA: ";

      size_t len = strlen(buffer);

      char *ptr = &buffer[len];

      len = sizeof(buffer) - len;

      for(j = 0; j < 16; j += 2) {

        size_t l;

        curl_msnprintf(ptr, len, "%s%02x%02x", j ? ":" : "",

                       d->addr[i].ip.v6[j],

                       d->addr[i].ip.v6[j + 1]);

        l = strlen(ptr);

        len -= l;

        ptr += l;

      }

      infof(data, "%s", buffer);

    }

  }

#ifdef USE_HTTPSRR

  for(i = 0; i < d->numhttps_rrs; i++) {

#if defined(DEBUGBUILD) && defined(CURLVERBOSE)

    doh_print_buf(data, "DoH HTTPS", d->https_rrs[i].val, d->https_rrs[i].len);

#else

    infof(data, "DoH HTTPS RR: length %d", d->https_rrs[i].len);

#endif

  }

#endif /* USE_HTTPSRR */

  for(i = 0; i < d->numcname; i++) {