GlobalProtect doesn't try to calculate MTU until after it has information on the ESP ciphersuite, so it can use the real HMAC/encryption key lengths when calculating ESP overhead. In practice, I have never seen or heard of a GP VPN that uses anything other than AES128+SHA1, but both the clients and servers appear to include support for AES256.
DTLS_OVERHEAD was not correctly accounting for possibility of AES256 (32-byte IV). Signed-off-by: Daniel Lenski <[email protected]> --- gpst.c | 9 +++++---- openconnect-internal.h | 2 +- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/gpst.c b/gpst.c index 71bd968..8eb925a 100644 --- a/gpst.c +++ b/gpst.c @@ -267,9 +267,8 @@ out: } #define ESP_OVERHEAD (4 /* SPI */ + 4 /* sequence number */ + \ - 20 /* biggest supported MAC (SHA1) */ + 16 /* biggest supported IV (AES-128) */ + \ - 1 /* pad length */ + 1 /* next header */ + \ - 16 /* max padding */ ) + 1 /* pad length */ + 1 /* next header */ + \ + 16 /* max padding */ ) #define UDP_HEADER_SIZE 8 #define IPV4_HEADER_SIZE 20 #define IPV6_HEADER_SIZE 40 @@ -323,7 +322,9 @@ static int calculate_mtu(struct openconnect_info *vpninfo) if (!mtu) { /* remove IP/UDP and ESP overhead from base MTU to calculate tunnel MTU */ - mtu = base_mtu - ESP_OVERHEAD - UDP_HEADER_SIZE; + mtu = ( base_mtu - UDP_HEADER_SIZE - ESP_OVERHEAD + - (vpninfo->hmac_key_len ? : 20) /* biggest supported MAC (SHA1) */ + - (vpninfo->enc_key_len ? : 32) /* biggest supported IV (AES-256) */ ); if (vpninfo->peer_addr->sa_family == AF_INET6) mtu -= IPV6_HEADER_SIZE; else diff --git a/openconnect-internal.h b/openconnect-internal.h index 3526ce6..af35791 100644 --- a/openconnect-internal.h +++ b/openconnect-internal.h @@ -334,7 +334,7 @@ static inline void init_pkt_queue(struct pkt_q *q) } #define DTLS_OVERHEAD (1 /* packet + header */ + 13 /* DTLS header */ + \ - 20 /* biggest supported MAC (SHA1) */ + 16 /* biggest supported IV (AES-128) */ + \ + 20 /* biggest supported MAC (SHA1) */ + 32 /* biggest supported IV (AES-256) */ + \ 16 /* max padding */) struct esp { -- 2.7.4 _______________________________________________ openconnect-devel mailing list [email protected] http://lists.infradead.org/mailman/listinfo/openconnect-devel
