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ping: Handle optional field in the IPv4 header

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dayarthvader 2022-01-21 21:30:06 +02:00 • committed by Linus Groh
parent 194cad0fc1
commit 67b7bbe1f6
1 changed files with 13 additions and 3 deletions
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16
Userland/Utilities/ping.cpp
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@ -30,6 +30,10 @@ static int min_ms;
static int max_ms; static int max_ms;
static const char* host; static const char* host;
static int payload_size = -1; static int payload_size = -1;
// variable part of header can be 0 to 40 bytes
// https://datatracker.ietf.org/doc/html/rfc791#section-3.1
static constexpr int max_optional_header_size_in_bytes = 40;
static constexpr int min_header_size_in_bytes = 5;
static void closing_statistics() static void closing_statistics()
{ {
@ -161,14 +165,13 @@ int main(int argc, char** argv)
total_pings++; total_pings++;
for (;;) { for (;;) {
// FIXME: IPv4 headers are not actually fixed-size, handle other sizes. auto pong_packet_result = ByteBuffer::create_uninitialized(
auto pong_packet_result = ByteBuffer::create_uninitialized(sizeof(struct ip) + sizeof(struct icmphdr) + payload_size); sizeof(struct ip) + max_optional_header_size_in_bytes + sizeof(struct icmphdr) + payload_size);
if (!pong_packet_result.has_value()) { if (!pong_packet_result.has_value()) {
warnln("failed to allocate a large enough buffer for the pong packet"); warnln("failed to allocate a large enough buffer for the pong packet");
return 1; return 1;
} }
auto& pong_packet = pong_packet_result.value(); auto& pong_packet = pong_packet_result.value();
struct icmphdr* pong_hdr = reinterpret_cast<struct icmphdr*>(pong_packet.data() + sizeof(struct ip));
socklen_t peer_address_size = sizeof(peer_address); socklen_t peer_address_size = sizeof(peer_address);
rc = recvfrom(fd, pong_packet.data(), pong_packet.size(), 0, (struct sockaddr*)&peer_address, &peer_address_size); rc = recvfrom(fd, pong_packet.data(), pong_packet.size(), 0, (struct sockaddr*)&peer_address, &peer_address_size);
if (rc < 0) { if (rc < 0) {
@ -180,6 +183,13 @@ int main(int argc, char** argv)
return 1; return 1;
} }
i8 internet_header_length = *pong_packet.data() & 0x0F;
if (internet_header_length < min_header_size_in_bytes) {
outln("ping: illegal ihl field value {:x}", internet_header_length);
continue;
}
struct icmphdr* pong_hdr = reinterpret_cast<struct icmphdr*>(pong_packet.data() + (internet_header_length * 4));
if (pong_hdr->type != ICMP_ECHOREPLY) if (pong_hdr->type != ICMP_ECHOREPLY)
continue; continue;
if (pong_hdr->code != 0) if (pong_hdr->code != 0)