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MEDIUM: ssl: Capture more info from Client Hello

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When we set tune.ssl.capture-cipherlist-size to a non-zero value
we are able to capture cipherlist supported by the client. To be able to
provide JA3 compatible TLS fingerprinting we need to capture more
information from Client Hello message:
- SSL Version
- SSL Extensions
- Elliptic Curves
- Elliptic Curve Point Formats
This patch allows HAProxy to capture such information and store it for
later use.
This commit is contained in:
Marcin Deranek 2021-07-12 14:16:55 +02:00 committed by Willy Tarreau
parent 5ef965606b
commit 769fd2e447
4 changed files with 142 additions and 18 deletions
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7
doc/configuration.txt
View File

@ -2806,9 +2806,10 @@ tune.ssl.ssl-ctx-cache-size <number>
1000 entries.
tune.ssl.capture-cipherlist-size <number>
Sets the maximum size of the buffer used for capturing client-hello cipher
list. If the value is 0 (default value) the capture is disabled, otherwise
a buffer is allocated for each SSL/TLS connection.
Sets the maximum size of the buffer used for capturing client hello cipher
list, extensions list, elliptic curves list and elliptic curve point
formats. If the value is 0 (default value) the capture is disabled,
otherwise a buffer is allocated for each SSL/TLS connection.
tune.vars.global-max-size <size>
tune.vars.proc-max-size <size>

14
include/haproxy/ssl_sock-t.h
View File

@ -201,9 +201,17 @@ struct ssl_sock_msg_callback {
/* This memory pool is used for capturing clienthello parameters. */
struct ssl_capture {
unsigned long long int xxh64;
unsigned char ciphersuite_len;
char ciphersuite[VAR_ARRAY];
ullong xxh64;
ushort protocol_version;
ushort ciphersuite_len;
ushort extensions_len;
ushort ec_len;
uint ciphersuite_offset;
uint extensions_offset;
uint ec_offset;
uint ec_formats_offset;
uchar ec_formats_len;
char data[VAR_ARRAY];
};
#ifdef HAVE_SSL_KEYLOG

2
src/ssl_sample.c
View File

@ -1145,7 +1145,7 @@ smp_fetch_ssl_fc_cl_bin(const struct arg *args, struct sample *smp, const char *
smp->flags = SMP_F_VOL_TEST | SMP_F_CONST;
smp->data.type = SMP_T_BIN;
smp->data.u.str.area = capture->ciphersuite;
smp->data.u.str.area = capture->data + capture->ciphersuite_offset;
smp->data.u.str.data = capture->ciphersuite_len;
return 1;
}

137
src/ssl_sock.c
View File

@ -1682,9 +1682,18 @@ static void ssl_sock_parse_clienthello(struct connection *conn, int write_p, int
SSL *ssl)
{
struct ssl_capture *capture;
unsigned char *msg;
unsigned char *end;
size_t rec_len;
uchar *msg;
uchar *end;
uchar *extensions_end;
uchar *ec_start = NULL;
uchar *ec_formats_start = NULL;
uchar *list_end;
ushort protocol_version;
ushort extension_id;
ushort ec_len = 0;
uchar ec_formats_len = 0;
int offset = 0;
int rec_len;
/* This function is called for "from client" and "to server"
* connections. The combination of write_p == 0 and content_type == 22
@ -1746,11 +1755,18 @@ static void ssl_sock_parse_clienthello(struct connection *conn, int write_p, int
if (end < msg)
return;
/* Expect 2 bytes for protocol version (1 byte for major and 1 byte
* for minor, the random, composed by 4 bytes for the unix time and
* 28 bytes for unix payload. So we jump 1 + 1 + 4 + 28.
/* Expect 2 bytes for protocol version
* (1 byte for major and 1 byte for minor)
*/
msg += 1 + 1 + 4 + 28;
if (msg + 2 > end)
return;
protocol_version = (msg[0] << 8) + msg[1];
msg += 2;
/* Expect the random, composed by 4 bytes for the unix time and
* 28 bytes for unix payload. So we jump 4 + 28.
*/
msg += 4 + 28;
if (msg > end)
return;
@ -1772,17 +1788,116 @@ static void ssl_sock_parse_clienthello(struct connection *conn, int write_p, int
if (msg + rec_len > end || msg + rec_len < msg)
return;
capture = pool_alloc(pool_head_ssl_capture);
capture = pool_zalloc(pool_head_ssl_capture);
if (!capture)
return;
/* Compute the xxh64 of the ciphersuite. */
capture->xxh64 = XXH64(msg, rec_len, 0);
/* Capture the ciphersuite. */
capture->ciphersuite_len = (global_ssl.capture_cipherlist < rec_len) ?
global_ssl.capture_cipherlist : rec_len;
memcpy(capture->ciphersuite, msg, capture->ciphersuite_len);
capture->ciphersuite_len = MIN(global_ssl.capture_cipherlist, rec_len);
capture->ciphersuite_offset = 0;
memcpy(capture->data, msg, capture->ciphersuite_len);
msg += rec_len;
offset += capture->ciphersuite_len;
/* Initialize other data */
capture->protocol_version = protocol_version;
/* Next, compression methods:
* if present, we have to jump by length + 1 for the size information
* if not present, we have to jump by 1 only
*/
if (msg[0] > 0)
msg += msg[0];
msg += 1;
if (msg > end)
goto store_capture;
/* We reached extensions */
if (msg + 2 > end)
goto store_capture;
rec_len = (msg[0] << 8) + msg[1];
msg += 2;
if (msg + rec_len > end || msg + rec_len < msg)
goto store_capture;
extensions_end = msg + rec_len;
capture->extensions_offset = offset;
/* Parse each extension */
while (msg + 4 < extensions_end) {
/* Add 2 bytes of extension_id */
if (global_ssl.capture_cipherlist >= offset + 2) {
capture->data[offset++] = msg[0];
capture->data[offset++] = msg[1];
capture->extensions_len += 2;
}
else
break;
extension_id = (msg[0] << 8) + msg[1];
/* Length of the extension */
rec_len = (msg[2] << 8) + msg[3];
/* Expect 2 bytes extension id + 2 bytes extension size */
msg += 2 + 2;
if (msg + rec_len > extensions_end || msg + rec_len < msg)
goto store_capture;
/* TLS Extensions
* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
if (extension_id == 0x000a) {
/* Elliptic Curves:
* https://www.rfc-editor.org/rfc/rfc8422.html
* https://www.rfc-editor.org/rfc/rfc7919.html */
list_end = msg + rec_len;
if (msg + 2 > list_end)
goto store_capture;
rec_len = (msg[0] << 8) + msg[1];
msg += 2;
if (msg + rec_len > list_end || msg + rec_len < msg)
goto store_capture;
/* Store location/size of the list */
ec_start = msg;
ec_len = rec_len;
}
else if (extension_id == 0x000b) {
/* Elliptic Curves Point Formats:
* https://www.rfc-editor.org/rfc/rfc8422.html */
list_end = msg + rec_len;
if (msg + 1 > list_end)
goto store_capture;
rec_len = msg[0];
msg += 1;
if (msg + rec_len > list_end || msg + rec_len < msg)
goto store_capture;
/* Store location/size of the list */
ec_formats_start = msg;
ec_formats_len = rec_len;
}
msg += rec_len;
}
if (ec_start) {
rec_len = ec_len;
if (offset + rec_len > global_ssl.capture_cipherlist)
rec_len = global_ssl.capture_cipherlist - offset;
memcpy(capture->data + offset, ec_start, rec_len);
capture->ec_offset = offset;
capture->ec_len = rec_len;
offset += rec_len;
}
if (ec_formats_start) {
rec_len = ec_formats_len;
if (offset + rec_len > global_ssl.capture_cipherlist)
rec_len = global_ssl.capture_cipherlist - offset;
memcpy(capture->data + offset, ec_formats_start, rec_len);
capture->ec_formats_offset = offset;
capture->ec_formats_len = rec_len;
offset += rec_len;
}
store_capture:
SSL_set_ex_data(ssl, ssl_capture_ptr_index, capture);
}