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Native DNS request decompression

This commit is contained in:
M66B 2016-01-23 10:57:20 +01:00
parent 26852ebfc3
commit 4d932657a0
1 changed files with 30 additions and 15 deletions
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45
app/src/main/jni/netguard/netguard.c
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@ -917,30 +917,45 @@ jboolean handle_udp(const struct arguments *args, const uint8_t *buffer, uint16_
// Check for DNS
if (ntohs(udphdr->dest) == 53 && datalen > sizeof(struct dns_header)) {
char *h = hex(buffer + dataoff, datalen);
log_android(ANDROID_LOG_DEBUG, "DNS off %d len %d hex %s", dataoff, datalen, h);
free(h);
struct dns_header *dns = (struct dns_header *) (buffer + dataoff);
uint16_t flags = ntohs(dns->flags);
// Check if standard query
if ((flags & DNS_QR) == 0 && (flags & DNS_OPCODE) == 0 && dns->qdcount != 0) {
uint16_t qdoff = dataoff + sizeof(struct dns_header);
// TODO DNS compression
char name[64];
uint8_t noff = 0;
uint8_t len = *(buffer + qdoff);
while (len && len < 64 && qdoff + 1 + len <= dataoff + datalen) {
memcpy(name + noff, buffer + qdoff + 1, len);
*(name + noff + len) = '.';
noff += (len + 1);
qdoff += (1 + len);
len = *(buffer + qdoff);
}
if (len < 64 && noff > 0 && qdoff + 5 <= dataoff + datalen) {
// http://tools.ietf.org/html/rfc1035
uint8_t len;
uint16_t ptr;
uint16_t qdoff = dataoff + sizeof(struct dns_header);
do {
len = *(buffer + qdoff);
if (len < 63) {
ptr = qdoff;
qdoff += (1 + len);
} else {
// TODO check top 2 bits
ptr = dataoff + (len & 63);
len = *(buffer + ptr);
qdoff += 1;
}
log_android(ANDROID_LOG_DEBUG, "DNS len %d ptr %d qdoff %d", len, ptr, qdoff);
if (len && ptr + 1 + len <= dataoff + datalen) {
memcpy(name + noff, buffer + ptr + 1, len);
*(name + noff + len) = '.';
noff += (len + 1);
}
} while (len && ptr + 1 + len <= dataoff + datalen);
if (noff > 0 && qdoff + 4 <= dataoff + datalen) {
*(name + noff - 1) = 0;
uint16_t qtype = ntohs(*((uint16_t *) (buffer + qdoff + 1)));
uint16_t qclass = ntohs(*((uint16_t *) (buffer + qdoff + 3)));
uint16_t qtype = ntohs(*((uint16_t *) (buffer + qdoff)));
uint16_t qclass = ntohs(*((uint16_t *) (buffer + qdoff + 2)));
log_android(ANDROID_LOG_WARN, "DNS %s qtype %d qclass %d", name, qtype, qclass);
}
}