src/opendns.c

#include "dnsmasq.h"
#include "opendns.h"

const unsigned char *
opendns_ssid_to_device_id(size_t * const device_id_len_p,
                          const unsigned char * const ssid,
                          const size_t ssid_len)
{
    unsigned char *map = daemon->ssid_device_id_map.map;
    unsigned char *map_tmp;
    unsigned char *ssid_tmp;
    unsigned char *device_id_tmp;
    size_t         ssid_tmp_len;
    size_t         device_id_len;

    if (map == NULL || ssid == NULL) {
        return NULL;
    }
    map_tmp = map;
    while ((ssid_tmp_len = (size_t) *map_tmp) > 0U) {
        ssid_tmp = ++map_tmp;
        map_tmp += ssid_tmp_len;
        device_id_len = (size_t) *map_tmp;
        device_id_tmp = ++map_tmp;
        if (ssid_tmp_len == ssid_len &&
            memcmp(ssid_tmp, ssid, ssid_len) == 0) {
            *device_id_len_p = device_id_len;
            return device_id_tmp;
        }
        map_tmp += device_id_len;
    }
    return NULL;
}

static int
opendns_parse_hex_char(unsigned char * const device_id,
                       size_t * const device_id_pos_p, int * const state_p,
                       unsigned char * const val_p, size_t device_id_len_max,
                       const int c)
{
    unsigned char c_val;

    switch (*state_p) {
    case 0:
    case 1:
        if (isspace(c) || (c == ':' && *state_p == 0)) {
            break;
        }
        if (c == '#') {
            *state_p = 2;
            break;
        }
        if (!isxdigit(c)) {
            return -1;
        }
        c_val = (c >= '0' && c <= '9') ? c - '0' : c - 'a' + 10;
        if (*state_p == 0) {
            *val_p = c_val * 16U;
            *state_p = 1;
        } else {
            *val_p |= c_val;
            device_id[(*device_id_pos_p)++] = *val_p;
            if (*device_id_pos_p >= device_id_len_max) {
                return 0;
            }
            *state_p = 0;
        }
        break;
    case 2:
        if (c == '\n') {
            *state_p = 0;
        }
    }
    return 1;
}

size_t
opendns_parse_hex(const char * const device_id_hex,
                  unsigned char * const device_id,
                  const size_t device_id_len_max)
{
    const char   *p = device_id_hex;
    size_t        device_id_pos = (size_t) 0U;
    int           c;
    int           ret;
    int           state = 0;
    unsigned char val = 0U;

    if (device_id_hex == NULL) {
        return (size_t) 0U;
    }
    while ((c = tolower((int) (unsigned char) *p)) != 0) {
        ret = opendns_parse_hex_char(device_id, &device_id_pos,
                                     &state, &val, device_id_len_max, c);
        if (ret < 0) {
            return (size_t) 0U;
        }
        if (ret == 0) {
            break;
        }
        p++;
    }
    return device_id_pos;
}

char *
opendns_parse_device_id_opt(char * const arg)
{
    struct ssid_device_id_map * const ssid_device_id_map =
        &daemon->ssid_device_id_map;
    unsigned char *device_id;
    unsigned char *tmp_map;
    char          *device_id_hex;
    char          *sep;
    char          *ssid;
    size_t         device_id_hex_len;
    size_t         device_id_len;
    size_t         device_id_len_max;
    size_t         pos;
    size_t         ssid_len;
    size_t         tmp_map_size;

    if ((sep = strrchr(arg, ',')) == NULL ||
        *(device_id_hex = sep + 1) == 0) {
        return _("missing device id");
    }
    *sep = 0;
    if (*(ssid = arg) == 0) {
        return _("missing SSID");
    }
    ssid_len = (size_t) (sep - ssid);
    if (ssid_len > 255U) {
        return _("SSID too long");
    }
    device_id_hex_len = strlen(device_id_hex);
    device_id_len_max = (device_id_hex_len + 1U) / 2U;
    device_id = safe_malloc(device_id_len_max);
    if (device_id_len_max > 255U) {
        free(device_id);
        return _("device id too long");
    }
    device_id_len = opendns_parse_hex(device_id_hex, device_id,
                                      device_id_len_max);
    if (device_id_len <= 0U) {
        free(device_id);
        return _("unable to parse a hex device id");
    }
    if (device_id_len > device_id_len_max) {
        free(device_id);
        return _("parsed device id too long");
    }
    tmp_map_size = ssid_device_id_map->map_size + 1U +
        ssid_len + 1U + device_id_len;
    if (ssid_device_id_map->map == NULL) {
        tmp_map_size++;
    }
    if ((tmp_map = realloc(ssid_device_id_map->map,
                           tmp_map_size)) == NULL) {
        die(_("could not get memory"), NULL, EC_NOMEM);
    }
    if (ssid_device_id_map->map_size <= 0U) {
        pos = 0U;
    } else {
        pos = ssid_device_id_map->map_size - 1U;
    }
    tmp_map[pos++] = (unsigned char) ssid_len;
    memcpy(&tmp_map[pos], ssid, ssid_len);
    pos += ssid_len;
    tmp_map[pos++] = (unsigned char) device_id_len;
    memcpy(&tmp_map[pos], device_id, device_id_len);
    pos += device_id_len;
    free(device_id);
    tmp_map[pos] = 0U;
    ssid_device_id_map->map = tmp_map;
    ssid_device_id_map->map_size = tmp_map_size;

    return NULL;
}

int
opendns_pop_tag_from_query(unsigned char * const packet,
                           size_t * const packet_size_p,
                           unsigned char * * const edns_options,
                           size_t *edns_options_len_p)
{
    static unsigned char edns_options_tpl[2U + 2U + 7U + 255U] = {
        0U, 4U, 0U, 0U, 'O', 'p', 'e', 'n', 'D', 'N', 'S'
    };
    const unsigned char *device_id;
    const unsigned char *tag;
    unsigned char       *tmp;
    size_t               edns_options_len;
    size_t               device_id_len;
    size_t               packet_size = *packet_size_p;
    size_t               tag_len;

    if (packet_size <= 0U) {
        *edns_options = NULL;
        *edns_options_len_p = 0U;
        return -1;
    }
    tag_len = (size_t) packet[packet_size - 1U];
    if (tag_len >= packet_size) {
        *edns_options = NULL;
        *edns_options_len_p = 0U;
        return -1;
    }
    tag = &packet[packet_size - tag_len - 1U];
    if ((device_id = opendns_ssid_to_device_id(&device_id_len,
                                                 tag, tag_len)) == NULL) {
        return -1;
    }
    edns_options_len = 2U + 2U + sizeof "OpenDNS" - 1U + device_id_len;
    if (edns_options_len > sizeof edns_options_tpl) {
        return -1;
    }
    memcpy(edns_options_tpl + 2U + 2U + sizeof "OpenDNS" - 1U,
           device_id, device_id_len);
    if (packet_size <= 1U + device_id_len) {
        return -1;
    }
    tmp = edns_options_tpl + 2U;
    PUTSHORT(sizeof "OpenDNS" - 1U + device_id_len, tmp);
    *edns_options = edns_options_tpl;
    *edns_options_len_p = edns_options_len;
    packet_size -= 1U + tag_len;
    *packet_size_p = packet_size;

    return 0;
}