summaryrefslogtreecommitdiff
path: root/src/openvpn/ps.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/openvpn/ps.c')
-rw-r--r--src/openvpn/ps.c34
1 files changed, 29 insertions, 5 deletions
diff --git a/src/openvpn/ps.c b/src/openvpn/ps.c
index 2089e6b..5d76078 100644
--- a/src/openvpn/ps.c
+++ b/src/openvpn/ps.c
@@ -983,14 +983,38 @@ is_openvpn_protocol(const struct buffer *buf)
const int len = BLEN(buf);
if (len >= 3)
{
- return p[0] == 0
- && p[1] >= 14
- && (p[2] == (P_CONTROL_HARD_RESET_CLIENT_V2 << P_OPCODE_SHIFT)
- || p[2] == (P_CONTROL_HARD_RESET_CLIENT_V3 << P_OPCODE_SHIFT));
+ int plen = (p[0] << 8) | p[1];
+
+ if (p[2] == (P_CONTROL_HARD_RESET_CLIENT_V3 << P_OPCODE_SHIFT))
+ {
+ /* WKc is at least 290 byte (not including metadata):
+ *
+ * 16 bit len + 256 bit HMAC + 2048 bit Kc = 2320 bit
+ *
+ * This is increased by the normal length of client handshake +
+ * tls-crypt overhead (32)
+ *
+ * For metadata tls-crypt-v2.txt does not explicitly specify
+ * an upper limit but we also have TLS_CRYPT_V2_MAX_WKC_LEN
+ * as 1024 bytes. We err on the safe side with 255 extra overhead
+ *
+ * We don't do the 2 byte check for tls-crypt-v2 because it is very
+ * unrealistic to have only 2 bytes available.
+ */
+ return (plen >= 336 && plen < (1024 + 255));
+ }
+ else
+ {
+ /* For non tls-crypt2 we assume the packet length to valid between
+ * 14 and 255 */
+ return plen >= 14 && plen <= 255
+ && (p[2] == (P_CONTROL_HARD_RESET_CLIENT_V2 << P_OPCODE_SHIFT));
+ }
}
else if (len >= 2)
{
- return p[0] == 0 && p[1] >= 14;
+ int plen = (p[0] << 8) | p[1];
+ return plen >= 14 && plen <= 255;
}
else
{