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QUIC: handle retransmissions and overlapping fragments in reassembler (#1195) #1498

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merged 9 commits into from
Apr 7, 2022
Merged

QUIC: handle retransmissions and overlapping fragments in reassembler (#1195) #1498

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4709d6f
QUIC: handle retransmissions and overlapping fragments in reassembler
viniciussn Mar 25, 2022
09eef77
Trigger CI
viniciussn Mar 25, 2022
7da7942
minor fix: parentheses
viniciussn Mar 25, 2022
53d4173
Changing ndpi_malloc to ndpi_calloc
viniciussn Mar 25, 2022
85419db
fix memory leak
viniciussn Mar 25, 2022
ad4f83a
quic_reasm_buf calloc to malloc
viniciussn Mar 28, 2022
c54db53
change order of is_ch_complete && is_reasm_buf_complete call
viniciussn Mar 28, 2022
268c1db
is_reasm_buf_complete: added handling for case where frame size is no…
viniciussn Mar 28, 2022
fa3e1ab
add extra check
viniciussn Apr 7, 2022
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2 changes: 1 addition & 1 deletion src/include/ndpi_typedefs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -716,7 +716,7 @@ struct ndpi_flow_udp_struct {

/* NDPI_PROTOCOL_QUIC */
u_int8_t *quic_reasm_buf;
u_int32_t quic_reasm_buf_len;
u_int8_t *quic_reasm_buf_bitmap;
u_int32_t quic_reasm_buf_last_pos;

/* NDPI_PROTOCOL_CSGO */
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7 changes: 5 additions & 2 deletions src/lib/ndpi_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4590,8 +4590,11 @@ void ndpi_free_flow_data(struct ndpi_flow_struct* flow) {
}

if(flow->l4_proto == IPPROTO_UDP) {
if(flow->l4.udp.quic_reasm_buf)
ndpi_free(flow->l4.udp.quic_reasm_buf);
if(flow->l4.udp.quic_reasm_buf){
ndpi_free(flow->l4.udp.quic_reasm_buf);
if(flow->l4.udp.quic_reasm_buf_bitmap)
ndpi_free(flow->l4.udp.quic_reasm_buf_bitmap);
}
}
}
}
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64 changes: 49 additions & 15 deletions src/lib/protocols/quic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1002,41 +1002,74 @@ static uint8_t *decrypt_initial_packet(struct ndpi_detection_module_struct *ndpi
return NULL;
}

static void update_reasm_buf_bitmap(u_int8_t *buffer_bitmap,
const u_int32_t buffer_bitmap_size,
const u_int32_t recv_pos,
const u_int32_t recv_len)
{
if (!recv_len || !buffer_bitmap_size || recv_pos + recv_len > buffer_bitmap_size * 8)
return;
const u_int32_t start_byte = recv_pos / 8;
const u_int32_t end_byte = (recv_pos + recv_len - 1) / 8;
const u_int32_t start_bit = recv_pos % 8;
const u_int32_t end_bit = (start_bit + recv_len - 1) % 8;
if (start_byte == end_byte)
buffer_bitmap[start_byte] |= (((1U << recv_len) - 1U) << start_bit); // fill from bit 'start_bit' until bit 'end_bit', both inclusive
else{
for (u_int32_t i = start_byte + 1; i <= end_byte - 1; i++)
buffer_bitmap[i] = 0xff; // completely received byte
buffer_bitmap[start_byte] |= ~((1U << start_bit) - 1U); // fill from bit 'start_bit' until bit 7, both inclusive
buffer_bitmap[end_byte] |= (1U << (end_bit + 1U)) - 1U; // fill from bit 0 until bit 'end_bit', both inclusive
}
}

static int is_reasm_buf_complete(const u_int8_t *buffer_bitmap,
const u_int32_t buffer_len)
{
const u_int32_t complete_bytes = buffer_len / 8;
const u_int32_t remaining_bits = buffer_len % 8;

for(u_int32_t i = 0; i < complete_bytes; i++)
if (buffer_bitmap[i] != 0xff)
return 0;

if (remaining_bits && buffer_bitmap[complete_bytes] != (1U << (remaining_bits)) - 1)
return 0;

return 1;
}

static int __reassemble(struct ndpi_flow_struct *flow, const u_int8_t *frag,
uint64_t frag_len, uint64_t frag_offset,
const u_int8_t **buf, u_int64_t *buf_len)
{
const uint64_t max_quic_reasm_buffer_len = 4096; /* Let's say a couple of full-MTU packets... */
const uint64_t max_quic_reasm_buffer_len = 4096; /* Let's say a couple of full-MTU packets... Must be multiple of 8*/
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const uint64_t quic_reasm_buffer_bitmap_len = max_quic_reasm_buffer_len / 8;
const uint64_t last_pos = frag_offset + frag_len;
/*
Working: in-order and out-of order, non overlapping, fragments
Not supported: retransmissions and (partial) overlapping
*/

if(!flow->l4.udp.quic_reasm_buf) {
flow->l4.udp.quic_reasm_buf = (uint8_t *)ndpi_malloc(max_quic_reasm_buffer_len);
if(!flow->l4.udp.quic_reasm_buf)
flow->l4.udp.quic_reasm_buf_bitmap = (uint8_t *)ndpi_calloc(quic_reasm_buffer_bitmap_len, sizeof(uint8_t));
if(!flow->l4.udp.quic_reasm_buf || !flow->l4.udp.quic_reasm_buf_bitmap)
return -1; /* Memory error */
flow->l4.udp.quic_reasm_buf_len = 0;
flow->l4.udp.quic_reasm_buf_last_pos = 0;
}
if(last_pos > max_quic_reasm_buffer_len)
return -3; /* Buffer too small */

memcpy(&flow->l4.udp.quic_reasm_buf[frag_offset], frag, frag_len);
flow->l4.udp.quic_reasm_buf_len += frag_len;
flow->l4.udp.quic_reasm_buf_last_pos = last_pos > flow->l4.udp.quic_reasm_buf_last_pos ? last_pos : flow->l4.udp.quic_reasm_buf_last_pos;
update_reasm_buf_bitmap(flow->l4.udp.quic_reasm_buf_bitmap, quic_reasm_buffer_bitmap_len, frag_offset, frag_len);

*buf = flow->l4.udp.quic_reasm_buf;
*buf_len = flow->l4.udp.quic_reasm_buf_len;
*buf_len = flow->l4.udp.quic_reasm_buf_last_pos;
return 0;
}
static int is_ch_complete(const u_int8_t *buf, uint64_t buf_len, uint64_t last_pos)
static int is_ch_complete(const u_int8_t *buf, uint64_t buf_len)
{
uint32_t msg_len;

if(buf_len >= 4 && last_pos == buf_len) {
if(buf_len >= 4) {
msg_len = (buf[1] << 16) + (buf[2] << 8) + buf[3];
if (4 + msg_len == buf_len) {
return 1;
Expand All @@ -1047,8 +1080,8 @@ static int is_ch_complete(const u_int8_t *buf, uint64_t buf_len, uint64_t last_p
static int is_ch_reassembler_pending(struct ndpi_flow_struct *flow)
{
return flow->l4.udp.quic_reasm_buf != NULL &&
!is_ch_complete(flow->l4.udp.quic_reasm_buf,
flow->l4.udp.quic_reasm_buf_len, flow->l4.udp.quic_reasm_buf_last_pos);
!(is_reasm_buf_complete(flow->l4.udp.quic_reasm_buf_bitmap, flow->l4.udp.quic_reasm_buf_last_pos)
&& is_ch_complete(flow->l4.udp.quic_reasm_buf, flow->l4.udp.quic_reasm_buf_last_pos));
}
static const uint8_t *get_reassembled_crypto_data(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow,
Expand All @@ -1063,7 +1096,7 @@ static const uint8_t *get_reassembled_crypto_data(struct ndpi_detection_module_s

/* Fast path: no need of reassembler stuff */
if(frag_offset == 0 &&
is_ch_complete(frag, frag_len, frag_len)) {
is_ch_complete(frag, frag_len)) {
NDPI_LOG_DBG2(ndpi_struct, "Complete CH (fast path)\n");
*crypto_data_len = frag_len;
return frag;
Expand All @@ -1072,7 +1105,8 @@ static const uint8_t *get_reassembled_crypto_data(struct ndpi_detection_module_s
rc = __reassemble(flow, frag, frag_len, frag_offset,
&crypto_data, crypto_data_len);
if(rc == 0) {
if(is_ch_complete(crypto_data, *crypto_data_len, flow->l4.udp.quic_reasm_buf_last_pos)) {
if(is_reasm_buf_complete(flow->l4.udp.quic_reasm_buf_bitmap, *crypto_data_len) &&
is_ch_complete(crypto_data, *crypto_data_len)) {
NDPI_LOG_DBG2(ndpi_struct, "Reassembler completed!\n");
return crypto_data;
}
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