coap_uri.c

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/* coap_uri.c -- helper functions for URI treatment
 *
 * Copyright (C) 2010--2012,2015-2016,2022-2024 Olaf Bergmann <bergmann@tzi.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * This file is part of the CoAP library libcoap. Please see
 * README for terms of use.
 */
 
#include "coap3/coap_libcoap_build.h"
 
#if defined(HAVE_LIMITS_H)
#include <limits.h>
#endif
 
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
 
COAP_STATIC_INLINE const uint8_t *
strnchr(const uint8_t *s, size_t len, unsigned char c) {
  while (len && *s++ != c)
    --len;
 
  return len ? s : NULL;
}
 
typedef enum coap_uri_check_t {
  COAP_URI_CHECK_URI,
  COAP_URI_CHECK_PROXY
} coap_uri_check_t;
 
coap_uri_info_t coap_uri_scheme[COAP_URI_SCHEME_LAST] = {
  { "coap",       COAP_DEFAULT_PORT,  0, COAP_URI_SCHEME_COAP },
  { "coaps",      COAPS_DEFAULT_PORT, 0, COAP_URI_SCHEME_COAPS },
  { "coap+tcp",   COAP_DEFAULT_PORT,  0, COAP_URI_SCHEME_COAP_TCP },
  { "coaps+tcp",  COAPS_DEFAULT_PORT, 0, COAP_URI_SCHEME_COAPS_TCP },
  { "http",         80,               1, COAP_URI_SCHEME_HTTP },
  { "https",       443,               1, COAP_URI_SCHEME_HTTPS },
  { "coap+ws",      80,               0, COAP_URI_SCHEME_COAP_WS },
  { "coaps+ws",    443,               0, COAP_URI_SCHEME_COAPS_WS }
};
 
static int
coap_split_uri_sub(const uint8_t *str_var,
                   size_t len,
                   coap_uri_t *uri,
                   coap_uri_check_t check_proxy) {
  const uint8_t *p, *q;
  int res = 0;
  size_t i;
  int is_unix_domain = 0;
 
  if (!str_var || !uri || len == 0)
    return -1;
 
  memset(uri, 0, sizeof(coap_uri_t));
  uri->port = COAP_DEFAULT_PORT;
 
  /* search for scheme */
  p = str_var;
  if (*p == '/') {
    /* no scheme, host or port */
    if (check_proxy == COAP_URI_CHECK_PROXY) {
      /* Must have ongoing host if proxy definition */
      return -1;
    }
    q = p;
    goto path;
  }
 
  /* find scheme terminating :// */
  while (len >= 3 && !(p[0] == ':' && p[1] == '/' && p[2] == '/')) {
    ++p;
    --len;
  }
  if (len < 3) {
    /* scheme not defined with a :// terminator */
    res = -2;
    goto error;
  }
  for (i = 0; i < COAP_URI_SCHEME_LAST; i++) {
    if ((p - str_var) == (int)strlen(coap_uri_scheme[i].name) &&
        memcmp(str_var, coap_uri_scheme[i].name, p - str_var) == 0) {
      if (check_proxy != COAP_URI_CHECK_PROXY && coap_uri_scheme[i].proxy_only) {
        coap_log_err("%.*s URI scheme not enabled (not a proxy)\n",
                     (int)(p - str_var), str_var);
        return -1;
      }
      uri->scheme = coap_uri_scheme[i].scheme;
      uri->port = coap_uri_scheme[i].port;
      break;
    }
  }
  if (i == COAP_URI_SCHEME_LAST) {
    /* scheme unknown */
    coap_log_err("%.*s URI scheme unknown\n", (int)(p - str_var), str_var);
    res = -1;
    goto error;
  }
  switch (uri->scheme) {
  case COAP_URI_SCHEME_COAP:
    break;
  case COAP_URI_SCHEME_COAPS:
    if (!coap_dtls_is_supported()) {
      coap_log_err("coaps URI scheme not supported in this version of libcoap\n");
      return -1;
    }
    break;
  case COAP_URI_SCHEME_COAP_TCP:
    if (!coap_tcp_is_supported()) {
      coap_log_err("coap+tcp URI scheme not supported in this version of libcoap\n");
      return -1;
    }
    break;
  case COAP_URI_SCHEME_COAPS_TCP:
    if (!coap_tls_is_supported()) {
      coap_log_err("coaps+tcp URI scheme not supported in this version of libcoap\n");
      return -1;
    }
    break;
  case COAP_URI_SCHEME_COAP_WS:
    if (!coap_ws_is_supported()) {
      coap_log_err("coap+ws URI scheme not supported in this version of libcoap\n");
      return -1;
    }
    break;
  case COAP_URI_SCHEME_COAPS_WS:
    if (!coap_wss_is_supported()) {
      coap_log_err("coaps+ws URI scheme not supported in this version of libcoap\n");
      return -1;
    }
    break;
  case COAP_URI_SCHEME_HTTP:
  case COAP_URI_SCHEME_HTTPS:
    /* Not proxy, caught above.  For proxy, assume app is doing CoAP <> HTTP mapping. */
    break;
  case COAP_URI_SCHEME_LAST:
  default:
    coap_log_warn("Unsupported URI type %d\n", uri->scheme);
    return -1;
  }
  /* skip :// */
  p += 3;
  len -= 3;
 
  /* p points to beginning of Uri-Host */
  q = p;
  if (len && *p == '[') {
    /* IPv6 address reference */
    ++p;
 
    while (len && *q != ']') {
      ++q;
      --len;
    }
 
    if (!len || *q != ']' || p == q) {
      res = -3;
      goto error;
    }
 
    COAP_SET_STR(&uri->host, q - p, p);
    ++q;
    --len;
  } else {
    /* IPv4 address, FQDN or Unix domain socket */
    if (len >= 3 && p[0] == '%' && p[1] == '2' &&
        (p[2] == 'F' || p[2] == 'f')) {
      /* Unix domain definition */
      uri->port = 0;
      is_unix_domain = 1;
    }
    while (len && *q != ':' && *q != '/' && *q != '?') {
      ++q;
      --len;
    }
 
    if (p == q) {
      res = -3;
      goto error;
    }
 
    COAP_SET_STR(&uri->host, q - p, p);
  }
 
  /* check for Uri-Port (invalid for Unix) */
  if (len && *q == ':') {
    if (is_unix_domain) {
      res = -5;
      goto error;
    }
    p = ++q;
    --len;
 
    while (len && isdigit(*q)) {
      ++q;
      --len;
    }
 
    if (p < q) {                /* explicit port number given */
      long uri_port = 0;
 
      while ((p < q) && (uri_port <= UINT16_MAX))
        uri_port = uri_port * 10 + (*p++ - '0');
 
      /* check if port number is in allowed range */
      if (uri_port > UINT16_MAX) {
        res = -4;
        goto error;
      }
 
      uri->port = (uint16_t)uri_port;
    }
  }
 
path:                 /* at this point, p must point to an absolute path */
 
  if (!len)
    goto end;
 
  if (*q == '/') {
    p = ++q;
    --len;
 
    while (len && *q != '?') {
      ++q;
      --len;
    }
 
    if (p < q) {
      COAP_SET_STR(&uri->path, q - p, p);
      p = q;
    }
  }
 
  /* Uri_Query */
  if (len && *p == '?') {
    ++p;
    --len;
    COAP_SET_STR(&uri->query, len, p);
    len = 0;
  }
 
end:
  return len ? -1 : 0;
 
error:
  return res;
}
 
int
coap_split_uri(const uint8_t *str_var, size_t len, coap_uri_t *uri) {
  return coap_split_uri_sub(str_var, len, uri, COAP_URI_CHECK_URI);
}
 
int
coap_split_proxy_uri(const uint8_t *str_var, size_t len, coap_uri_t *uri) {
  return coap_split_uri_sub(str_var, len, uri, COAP_URI_CHECK_PROXY);
}
 
static void
coap_replace_upper_lower(coap_optlist_t *optlist) {
  size_t i;
 
  for (i = 0; i < optlist->length; i++) {
    if (optlist->data[i] >= 'A' && optlist->data[i] <= 'Z') {
      optlist->data[i] += 'a' - 'A';
    }
  }
}
 
int
coap_uri_into_options(const coap_uri_t *uri, const coap_address_t *dst,
                      coap_optlist_t **optlist_chain, int create_port_host_opt,
                      uint8_t *_buf COAP_UNUSED, size_t buflen COAP_UNUSED) {
  return !coap_uri_into_optlist(uri, dst, optlist_chain, create_port_host_opt) ? -1 : 0;
}
 
int
coap_uri_into_optlist(const coap_uri_t *uri, const coap_address_t *dst,
                      coap_optlist_t **optlist_chain, int create_port_host_opt) {
  if (create_port_host_opt && !coap_host_is_unix_domain(&uri->host)) {
    int add_option = 0;
 
    if (dst && uri->host.length) {
#if !defined(WITH_LWIP) && !defined(WITH_CONTIKI)
      char addr[INET6_ADDRSTRLEN];
#else /* WITH_LWIP || WITH_CONTIKI */
      char addr[40];
#endif /* WITH_LWIP || WITH_CONTIKI */
      coap_optlist_t *optlist;
 
      /* Add in Uri-Host if not match (need to strip off %iface) */
      size_t uri_host_len = uri->host.length;
      const uint8_t *cp = uri->host.s;
 
      /* Unfortunately not null terminated */
      for (size_t i = 0; i < uri_host_len; i++) {
        if (cp[i] == '%') {
          /* %iface specified in host name */
          uri_host_len = i;
          break;
        }
      }
 
      if (coap_print_ip_addr(dst, addr, sizeof(addr)) &&
          (strlen(addr) != uri_host_len ||
           memcmp(addr, uri->host.s, uri_host_len) != 0)) {
        /* add Uri-Host */
        optlist = coap_new_optlist(COAP_OPTION_URI_HOST, uri->host.length,
                                   uri->host.s);
        if (!coap_host_is_unix_domain(&uri->host)) {
          coap_replace_percents(optlist);
          coap_replace_upper_lower(optlist);
        }
        if (!coap_insert_optlist(optlist_chain, optlist)) {
          return 0;
        }
      }
    }
    /* Add in UriPort if not default */
    switch ((int)uri->scheme) {
    case COAP_URI_SCHEME_HTTP:
    case COAP_URI_SCHEME_COAP_WS:
      if (uri->port != 80)
        add_option = 1;
      break;
    case COAP_URI_SCHEME_HTTPS:
    case COAP_URI_SCHEME_COAPS_WS:
      if (uri->port != 443)
        add_option = 1;
      break;
    default:
      if (uri->port != (coap_uri_scheme_is_secure(uri) ? COAPS_DEFAULT_PORT :
                        COAP_DEFAULT_PORT))
        add_option = 1;
      break;
    }
    if (add_option) {
      uint8_t tbuf[4];
 
      coap_insert_optlist(optlist_chain,
                          coap_new_optlist(COAP_OPTION_URI_PORT,
                                           coap_encode_var_safe(tbuf, 4,
                                                                (uri->port & 0xffff)),
                                           tbuf));
    }
  }
 
  if (uri->path.length) {
    if (!coap_path_into_optlist(uri->path.s, uri->path.length, COAP_OPTION_URI_PATH,
                                optlist_chain))
      return 0;
  }
 
  if (uri->query.length) {
    if (!coap_query_into_optlist(uri->query.s, uri->query.length, COAP_OPTION_URI_QUERY,
                                 optlist_chain))
      return 0;
  }
  return 1;
}
 
int
coap_host_is_unix_domain(const coap_str_const_t *host) {
  if (host->length >= 3 && host->s[0] == '%' &&
      host->s[1] == '2' &&
      (host->s[2] == 'F' || host->s[2] == 'f')) {
    return 1;
  }
  if (host->length >= 1 && host->s[0] == '/')
    return 1;
  return 0;
}
 
#define hexchar_to_dec(c) ((c) & 0x40 ? ((c) & 0x0F) + 9 : ((c) & 0x0F))
 
static void
decode_segment(const uint8_t *seg, size_t length, unsigned char *buf) {
 
  while (length--) {
 
    if (*seg == '%') {
      *buf = (hexchar_to_dec(seg[1]) << 4) + hexchar_to_dec(seg[2]);
 
      seg += 2;
      length -= 2;
    } else {
      *buf = *seg;
    }
 
    ++buf;
    ++seg;
  }
}
 
static int
check_segment(const uint8_t *s, size_t length, size_t *segment_size) {
  size_t n = 0;
 
  while (length) {
    if (*s == '%') {
      if (length < 2 || !(isxdigit(s[1]) && isxdigit(s[2])))
        return -1;
 
      s += 2;
      length -= 2;
    }
 
    ++s;
    ++n;
    --length;
  }
 
  *segment_size = n;
 
  return 0;
}
 
static int
make_decoded_option(const uint8_t *s, size_t length,
                    unsigned char *buf, size_t buflen, size_t *optionsize) {
  int res;
  size_t segmentlen;
  size_t written;
 
  if (!buflen) {
    coap_log_debug("make_decoded_option(): buflen is 0!\n");
    return -1;
  }
 
  res = check_segment(s, length, &segmentlen);
  if (res < 0)
    return -1;
 
  /* write option header using delta 0 and length res */
  written = coap_opt_setheader(buf, buflen, 0, segmentlen);
 
  assert(written <= buflen);
 
  if (!written)                        /* encoding error */
    return -1;
 
  buf += written;                /* advance past option type/length */
  buflen -= written;
 
  if (buflen < segmentlen) {
    coap_log_debug("buffer too small for option\n");
    return -1;
  }
 
  decode_segment(s, length, buf);
 
  *optionsize = written + segmentlen;
 
  return 0;
}
 
 
#ifndef min
#define min(a,b) ((a) < (b) ? (a) : (b))
#endif
 
typedef void (*segment_handler_t)(const uint8_t *, size_t, void *);
 
static int
dots(const uint8_t *s, size_t len) {
  uint8_t p;
 
  if (!len)
    return 0;
 
  p = *s;
 
  /* Check 'first' char */
  if (p == '%' && len >=3) {
    if (s[1] == '2' && (s[2] == 'E' || s[2] == 'e')) {
      s += 2;
      len -= 2;
    }
    p = '.';
  }
  if (p != '.')
    return 0;
  if (len == 1)
    return 1;
 
  /* Check 'second' char, first is '.' */
  s++;
  len--;
  assert(len);
  p = *s;
  if (p == '%' && len >=3) {
    if (s[1] == '2' && (s[2] == 'E' || s[2] == 'e')) {
      len -= 2;
    }
    p = '.';
  }
  if (p != '.')
    return 0;
  if (len == 1)
    return 2;
 
  return 0;
}
 
struct cnt_str {
  coap_string_t base_buf;
  coap_string_t buf;
  int n;
};
 
static void
backup_segment(void *data) {
  struct cnt_str *state = (struct cnt_str *)data;
  int i;
  uint8_t *buf;
 
  if (state->n == 0)
    return;
 
  state->n--;
  buf = state->base_buf.s;
  for (i = 0; i < state->n; i++) {
    buf += coap_opt_size(buf);
  }
  state->buf.s = buf;
  state->buf.length = state->base_buf.length - (buf - state->base_buf.s);
}
 
static size_t
coap_split_path_impl(const uint8_t *path, size_t len,
                     segment_handler_t h, void *data) {
  const uint8_t *p, *q;
  size_t length = len;
  int num_dots;
 
  p = q = path;
  while (length > 0 && !strnchr((const uint8_t *)"?#", 2, *q)) {
    if (*q == '/') {
      /* start new segment */
      num_dots = dots(p, q - p);
      switch (num_dots) {
      case 1:
        /* drop segment */
        break;
      case 2:
        /* backup segment */
        backup_segment(data);
        break;
      case 0:
      default:
        /* add segment */
        h(p, q - p, data);
        break;
      }
 
      p = q + 1;
    }
 
    q++;
    length--;
  }
 
  /* write last segment */
  num_dots = dots(p, q - p);
  switch (num_dots) {
  case 1:
    /* drop segment */
    break;
  case 2:
    /* backup segment */
    backup_segment(data);
    break;
  case 0:
  default:
    /* add segment */
    h(p, q - p, data);
    break;
  }
 
  return q - path;
}
 
static void
write_option(const uint8_t *s, size_t len, void *data) {
  struct cnt_str *state = (struct cnt_str *)data;
  int res;
  size_t optionsize;
  assert(state);
 
  res = make_decoded_option(s, len, state->buf.s, state->buf.length, &optionsize);
  if (res == 0) {
    state->buf.s += optionsize;
    state->buf.length -= optionsize;
    state->n++;
  }
}
 
int
coap_split_path(const uint8_t *s, size_t length,
                unsigned char *buf, size_t *buflen) {
  struct cnt_str tmp = { { *buflen, buf }, { *buflen, buf }, 0 };
 
  coap_split_path_impl(s, length, write_option, &tmp);
 
  *buflen = *buflen - tmp.buf.length;
 
  return tmp.n;
}
 
void
coap_replace_percents(coap_optlist_t *optlist) {
  size_t i;
  size_t o = 0;
 
  for (i = 0; i < optlist->length; i++) {
    if (optlist->data[i] == '%' && optlist->length - i >= 3) {
      optlist->data[o] = (hexchar_to_dec(optlist->data[i+1]) << 4) +
                         hexchar_to_dec(optlist->data[i+2]);
      i+= 2;
    } else if (o != i) {
      optlist->data[o] = optlist->data[i];
    }
    o++;
  }
  optlist->length = o;
}
 
static void
backup_optlist(coap_optlist_t **optlist_begin) {
  coap_optlist_t *last = NULL;
  coap_optlist_t *cur = *optlist_begin;
 
  if (!cur)
    return;
 
  while (cur) {
    if (!cur->next)
      break;
    last = cur;
    cur = cur->next;
  }
  coap_delete_optlist(cur);
  if (last) {
    last->next = NULL;
  } else {
    *optlist_begin = NULL;
  }
}
 
int
coap_path_into_optlist(const uint8_t *s, size_t length, coap_option_num_t optnum,
                       coap_optlist_t **optlist_chain) {
  const uint8_t *p = s;
  coap_optlist_t *optlist;
  int num_dots;
  coap_optlist_t **optlist_start;
 
  if (*optlist_chain) {
    /* Something previously in optlist_chain. Need to make that the start */
    optlist_start = &((*optlist_chain)->next);
  } else {
    optlist_start = optlist_chain;
  }
 
  while (length > 0 && !strnchr((const uint8_t *)"?#", 2, *s)) {
    if (*s == '/') {                /* start of new path element */
      /* start new segment */
      num_dots = dots(p, s - p);
      switch (num_dots) {
      case 1:
        /* drop segment */
        break;
      case 2:
        /* backup segment */
        backup_optlist(optlist_start);
        break;
      case 0:
      default:
        /* add segment */
        optlist = coap_new_optlist(optnum, s - p, p);
        coap_replace_percents(optlist);
        if (!coap_insert_optlist(optlist_chain, optlist)) {
          return 0;
        }
        break;
      }
      p = s + 1;
    }
    s++;
    length--;
 
  }
  /* add last path element */
  num_dots = dots(p, s - p);
  switch (num_dots) {
  case 1:
    /* drop segment */
    break;
  case 2:
    /* backup segment */
    backup_optlist(optlist_start);
    break;
  case 0:
  default:
    /* add segment */
    optlist = coap_new_optlist(optnum, s - p, p);
    coap_replace_percents(optlist);
    if (!coap_insert_optlist(optlist_chain, optlist)) {
      return 0;
    }
    break;
  }
  return 1;
}
 
int
coap_split_query(const uint8_t *s, size_t length,
                 unsigned char *buf, size_t *buflen) {
  struct cnt_str tmp = { { *buflen, buf }, { *buflen, buf }, 0 };
  const uint8_t *p;
 
  p = s;
  while (length > 0 && *s != '#') {
    if (*s == '&') {                /* start new query element */
      write_option(p, s - p, &tmp);
      p = s + 1;
    }
 
    s++;
    length--;
  }
 
  /* write last query element */
  write_option(p, s - p, &tmp);
 
  *buflen = *buflen - tmp.buf.length;
  return tmp.n;
}
 
int
coap_query_into_optlist(const uint8_t *s, size_t length, coap_option_num_t optnum,
                        coap_optlist_t **optlist_chain) {
  const uint8_t *p = s;
  coap_optlist_t *optlist;
 
  while (length > 0 && *s != '#') {
    if (*s == '&') {                /* start of new query element */
      /* add previous query element */
      optlist = coap_new_optlist(optnum, s - p, p);
      coap_replace_percents(optlist);
      if (!coap_insert_optlist(optlist_chain, optlist)) {
        return 0;
      }
      p = s + 1;
    }
    s++;
    length--;
  }
  /* add last query element */
  optlist = coap_new_optlist(optnum, s - p, p);
  coap_replace_percents(optlist);
  if (!coap_insert_optlist(optlist_chain, optlist)) {
    return 0;
  }
  return 1;
}
 
#define URI_DATA(uriobj) ((unsigned char *)(uriobj) + sizeof(coap_uri_t))
 
coap_uri_t *
coap_new_uri(const uint8_t *uri, unsigned int length) {
  uint8_t *result;
  coap_uri_t *out_uri;
 
  out_uri = (coap_uri_t *)coap_malloc_type(COAP_STRING, length + 1 + sizeof(coap_uri_t));
 
  if (!out_uri)
    return NULL;
 
  result = (uint8_t *)out_uri;
  memcpy(URI_DATA(result), uri, length);
  URI_DATA(result)[length] = '\0'; /* make it zero-terminated */
 
  if (coap_split_uri(URI_DATA(result), length, out_uri) < 0) {
    coap_free_type(COAP_STRING, out_uri);
    return NULL;
  }
  return out_uri;
}
 
coap_uri_t *
coap_clone_uri(const coap_uri_t *uri) {
  coap_uri_t *result;
  uint8_t *p;
 
  if (!uri)
    return  NULL;
 
  result = (coap_uri_t *)coap_malloc_type(COAP_STRING,  uri->query.length + uri->host.length +
                                          uri->path.length + sizeof(coap_uri_t) + 1);
 
  if (!result)
    return NULL;
 
  memset(result, 0, sizeof(coap_uri_t));
 
  result->port = uri->port;
 
  if (uri->host.length) {
    result->host.s = p = URI_DATA(result);
    result->host.length = uri->host.length;
 
    memcpy(p, uri->host.s, uri->host.length);
  }
 
  if (uri->path.length) {
    result->path.s = p = URI_DATA(result) + uri->host.length;
    result->path.length = uri->path.length;
 
    memcpy(p, uri->path.s, uri->path.length);
  }
 
  if (uri->query.length) {
    result->query.s = p = URI_DATA(result) + uri->host.length + uri->path.length;
    result->query.length = uri->query.length;
 
    memcpy(p, uri->query.s, uri->query.length);
  }
 
  return result;
}
 
void
coap_delete_uri(coap_uri_t *uri) {
  coap_free_type(COAP_STRING, uri);
}
 
static int
is_unescaped_in_path(const uint8_t c) {
  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') ||
         (c >= '0' && c <= '9') || c == '-' || c == '.' || c == '_' ||
         c == '~' || c == '!' || c == '$' || c == '\'' || c == '(' ||
         c == ')' || c == '*' || c == '+' || c == ',' || c == ';' ||
         c=='=' || c==':' || c=='@' || c == '&';
}
 
static int
is_unescaped_in_query(const uint8_t c) {
  return is_unescaped_in_path(c) || c=='/' || c=='?';
}
 
coap_string_t *
coap_get_query(const coap_pdu_t *request) {
  coap_opt_iterator_t opt_iter;
  coap_opt_filter_t f;
  coap_opt_t *q;
  coap_string_t *query = NULL;
  size_t length = 0;
  static const uint8_t hex[] = "0123456789ABCDEF";
 
  coap_option_filter_clear(&f);
  coap_option_filter_set(&f, COAP_OPTION_URI_QUERY);
  coap_option_iterator_init(request, &opt_iter, &f);
  while ((q = coap_option_next(&opt_iter))) {
    uint16_t seg_len = coap_opt_length(q), i;
    const uint8_t *seg= coap_opt_value(q);
    for (i = 0; i < seg_len; i++) {
      if (is_unescaped_in_query(seg[i]))
        length += 1;
      else
        length += 3;
    }
    length += 1;
  }
  if (length > 0)
    length -= 1;
  if (length > 0) {
    query = coap_new_string(length);
    if (query) {
      query->length = length;
      unsigned char *s = query->s;
      coap_option_iterator_init(request, &opt_iter, &f);
      while ((q = coap_option_next(&opt_iter))) {
        if (s != query->s)
          *s++ = '&';
        uint16_t seg_len = coap_opt_length(q), i;
        const uint8_t *seg= coap_opt_value(q);
        for (i = 0; i < seg_len; i++) {
          if (is_unescaped_in_query(seg[i])) {
            *s++ = seg[i];
          } else {
            *s++ = '%';
            *s++ = hex[seg[i]>>4];
            *s++ = hex[seg[i]&0x0F];
          }
        }
      }
    }
  }
  return query;
}
 
coap_string_t *
coap_get_uri_path(const coap_pdu_t *request) {
  coap_opt_iterator_t opt_iter;
  coap_opt_filter_t f;
  coap_opt_t *q;
  coap_string_t *uri_path = NULL;
  size_t length = 0;
  static const uint8_t hex[] = "0123456789ABCDEF";
 
  q = coap_check_option(request, COAP_OPTION_PROXY_URI, &opt_iter);
  if (q) {
    coap_uri_t uri;
 
    if (coap_split_proxy_uri(coap_opt_value(q),
                             coap_opt_length(q), &uri) < 0) {
      return NULL;
    }
    uri_path = coap_new_string(uri.path.length);
    if (uri_path) {
      memcpy(uri_path->s, uri.path.s, uri.path.length);
    }
    return uri_path;
  }
 
  coap_option_filter_clear(&f);
  coap_option_filter_set(&f, COAP_OPTION_URI_PATH);
  coap_option_iterator_init(request, &opt_iter, &f);
  while ((q = coap_option_next(&opt_iter))) {
    uint16_t seg_len = coap_opt_length(q), i;
    const uint8_t *seg= coap_opt_value(q);
    for (i = 0; i < seg_len; i++) {
      if (is_unescaped_in_path(seg[i]))
        length += 1;
      else
        length += 3;
    }
    /* bump for the leading "/" */
    length += 1;
  }
  /* The first entry does not have a leading "/" */
  if (length > 0)
    length -= 1;
 
  /* if 0, either no URI_PATH Option, or the first one was empty */
  uri_path = coap_new_string(length);
  if (uri_path) {
    uri_path->length = length;
    unsigned char *s = uri_path->s;
    int n = 0;
    coap_option_iterator_init(request, &opt_iter, &f);
    while ((q = coap_option_next(&opt_iter))) {
      if (n++) {
        *s++ = '/';
      }
      uint16_t seg_len = coap_opt_length(q), i;
      const uint8_t *seg= coap_opt_value(q);
      for (i = 0; i < seg_len; i++) {
        if (is_unescaped_in_path(seg[i])) {
          *s++ = seg[i];
        } else {
          *s++ = '%';
          *s++ = hex[seg[i]>>4];
          *s++ = hex[seg[i]&0x0F];
        }
      }
    }
  }
  return uri_path;
}