diff options
Diffstat (limited to 'src/openvpn/ps.c')
| -rw-r--r-- | src/openvpn/ps.c | 34 |
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 { |