release/src/router/dnscrypt/src/plugins/example-ldns-opendns-set-client-ip/example-ldns-opendns-set-client-ip.c

   1
   2 #include <assert.h>
   3 #include <stdio.h>
   4 #include <string.h>
   5
   6 #include <dnscrypt/plugin.h>
   7 #include <ldns/ldns.h>
   8 #include <ldns/util.h>
   9
  10 DCPLUGIN_MAIN(__FILE__);
  11
  12 #define EDNS_HEADER           "4f56" "0014" "4f444e5300" "00"
  13 #define EDNS_HEADER_CLIENT_IP "10"
  14 #define EDNS_CLIENT_IP        "7f000001"
  15 #define EDNS_HEADER_FODDER    "40"
  16 #define EDNS_FODDER           "deadbeefabad1dea"
  17
  18 #define EDNS_DATA EDNS_HEADER \
  19     EDNS_HEADER_CLIENT_IP EDNS_CLIENT_IP EDNS_HEADER_FODDER EDNS_FODDER
  20
  21 #define EDNS_CLIENT_IP_OFFSET (sizeof EDNS_HEADER - 1U + \
  22                                sizeof EDNS_HEADER_CLIENT_IP - 1U)
  23
  24 #define EDNS_FODDER_OFFSET (sizeof EDNS_HEADER - 1U + \
  25                             sizeof EDNS_HEADER_CLIENT_IP - 1U + \
  26                             sizeof EDNS_CLIENT_IP - 1U + \
  27                             sizeof EDNS_HEADER_FODDER - 1U)
  28
  29 const char *
  30 dcplugin_description(DCPlugin * const dcplugin)
  31 {
  32     return "Apply the OpenDNS settings defined for a specific IP address";
  33 }
  34
  35 const char *
  36 dcplugin_long_description(DCPlugin * const dcplugin)
  37 {
  38     return
  39         "The IP address must be a hex-encoded IPv4 address.\n"
  40         "\n"
  41         "Usage:\n"
  42         "\n"
  43         "# dnscrypt-proxy --plugin \\\n"
  44         "  libdcplugin_example_ldns_opendns_set_client_ip.la,7f000001";
  45 }
  46
  47 int
  48 dcplugin_init(DCPlugin * const dcplugin, int argc, char *argv[])
  49 {
  50     char   *edns_hex;
  51     size_t  edns_hex_size = sizeof EDNS_DATA;
  52
  53     ldns_init_random(NULL, 0U);
  54     edns_hex = malloc(edns_hex_size);
  55     dcplugin_set_user_data(dcplugin, edns_hex);
  56     if (edns_hex == NULL) {
  57         return -1;
  58     }
  59     memcpy(edns_hex, EDNS_DATA, edns_hex_size);
  60     assert(sizeof EDNS_CLIENT_IP - 1U == (size_t) 8U);
  61     if (argc > 1 && strlen(argv[1]) == (size_t) 8U) {
  62         memcpy(edns_hex + EDNS_CLIENT_IP_OFFSET,
  63                argv[1], sizeof EDNS_CLIENT_IP - 1U);
  64     }
  65     return 0;
  66 }
  67
  68 int
  69 dcplugin_destroy(DCPlugin *dcplugin)
  70 {
  71     free(dcplugin_get_user_data(dcplugin));
  72
  73     return 0;
  74 }
  75
  76 static void
  77 fill_with_random_hex_data(char * const str, size_t size)
  78 {
  79     size_t   i = (size_t) 0U;
  80     uint16_t rnd;
  81
  82     while (i < size) {
  83         rnd = ldns_get_random();
  84         str[i++] = "0123456789abcdef"[rnd & 0xf];
  85         str[i++] = "0123456789abcdef"[(rnd >> 8) & 0xf];
  86     }
  87 }
  88
  89 DCPluginSyncFilterResult
  90 dcplugin_sync_pre_filter(DCPlugin *dcplugin, DCPluginDNSPacket *dcp_packet)
  91 {
  92     uint8_t  *new_packet;
  93     ldns_rdf *edns_data;
  94     char     *edns_data_str;
  95     ldns_pkt *packet;
  96     size_t    new_packet_size;
  97
  98     ldns_wire2pkt(&packet, dcplugin_get_wire_data(dcp_packet),
  99                   dcplugin_get_wire_data_len(dcp_packet));
 100
 101     edns_data_str = dcplugin_get_user_data(dcplugin);
 102     fill_with_random_hex_data(edns_data_str + EDNS_FODDER_OFFSET,
 103                               sizeof EDNS_FODDER - 1U);
 104     edns_data = ldns_rdf_new_frm_str(LDNS_RDF_TYPE_HEX, edns_data_str);
 105     ldns_pkt_set_edns_data(packet, edns_data);
 106
 107     ldns_pkt2wire(&new_packet, packet, &new_packet_size);
 108     if (dcplugin_get_wire_data_max_len(dcp_packet) >= new_packet_size) {
 109         dcplugin_set_wire_data(dcp_packet, new_packet, new_packet_size);
 110     }
 111
 112     free(new_packet);
 113     ldns_pkt_free(packet);
 114
 115     return DCP_SYNC_FILTER_RESULT_OK;
 116 }