Please note that the implementation is not 100% conformant to the protocol whitepaper (https://www.wireguard.com/papers/wireguard.pdf).
More specifically: all peers are expected to send a handshake initiation once the current keypair is about to expire or is expired.
I decided not to do that because our implementation is meant to act as a server only. A true WireGuard peer acts, instead, as both a client and a server.
Once the keypair is expired, we immediately delete the session.
The cookie mechanism can be implemented in future.
As for authentication: unfortunately using the already existing methods is not possible due to the protocol not providing a way to send strings to a peer.
That's because WireGuard doesn't have a concept of "users": it identifies a peer through the public key, which is determined using the source address.
As a solution, this commit adds a special authentication method: once we receive the handshake initiation message and decrypt the peer's public key, we check whether it's in the allowed key list.
If it is, we retrieve the associated Virtual Hub and user; if the hub exists and the user is in it, the authentication is successful.
The allowed key list is stored in the configuration file like this:
declare WireGuardKeyList
{
declare 96oA7iMvjn7oXiG3ghBDPaSUytT75uXceLV+Fx3XMlM=
{
string Hub DEFAULT
string User user
}
}
The WireGuard implementation will have two options that should not have a fixed default value, because they represent two keys (one is preshared, the other is private).
Instead of handling these two options differently in ProtoNewContainer(), this commit adds a new function to PROTO_IMPL: ProtoOptionString().
ProtoOptionString() takes the option's name as argument and returns a heap-allocated string that will be used as value. The function returns NULL when the option doesn't need a randomized value.
ProtoHandleDatagrams() takes care of deleting a session if marked as halted.
However, the check is performed when a packet for that session is received; that never happens if the remote host doesn't send at least a packet.
This commit fixes the issue by moving the check into the loop that iterates through all sessions.
PROTO_OPTION is a structure that describes an option (who would've guessed?).
It's designed in a way that allows it to occupy as low memory as possible, while providing great flexibility.
The idea is similar to the one implemented in LIST for trivial types, with the difference that PROTO_OPTION doesn't require casting due to the use of union.
The SSTP implementation doesn't provide packet identification, because it's not required: the protocol is identified by the HTTP header it sends to the server.
*** CID 358434: Null pointer dereferences (REVERSE_INULL)
/src/Cedar/Proto.c: 451 in ProtoHandleDatagrams()
445 void ProtoHandleDatagrams(UDPLISTENER *listener, LIST *datagrams)
446 {
447 UINT i;
448 HASH_LIST *sessions;
449 PROTO *proto = listener->Param;
450
>>> CID 358434: Null pointer dereferences (REVERSE_INULL)
>>> Null-checking "listener" suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
451 if (proto == NULL || listener == NULL || datagrams == NULL)
452 {
453 return;
454 }
455
456 sessions = proto->Sessions;
When a datagram is received, the matching session is looked up in a hash list; if it's not found, a new session is created.
This method allows to use a single UDP port for multiple protocols, as we do with TCP.
Also, each session has its own dedicated thread, used to process the received datagrams and generate the ones that are then sent through the UDP listener.
In addition to guaranteeing constant performance, separate threads also prevent a single one from blocking all sessions.
- An additional parameter is added to IsPacketForMe(), used to specify the protocol type (currently either TCP or UDP).
- SupportedModes() is dropped because it's now redundant.
- IsOk() and EstablishedSessions() are dropped because error checking should be handled by the implementation.
- ProtoImplDetect() now takes a buffer and its size rather than a SOCK, so that it can be used to detect UDP protocols.
- The OpenVPN toggle check is moved to ProtoImplDetect(), so that we don't have to duplicate it once UDP support is implemented.
The PROTO structure is now used to identify the system as a whole, rather than a single protocol. It's stored and initialized in Server.
ProtoCompare(), ProtoAdd() and ProtoDetected() are renamed to make the difference between PROTO and PROTO_IMPL more clear.
ProtoGet() and ProtoNum() are removed because the related list can now be accessed directly by Server.
This commit adds a protocol interface to the server, its purpose is to manage TCP connections and the various third-party protocols.
More specifically, ProtoHandleConnection() takes care of exchanging the packets between the local and remote endpoint; the protocol implementation only has to parse them and act accordingly.
The interface knows which protocol is the connection for by calling IsPacketForMe(), a function implemented for each protocol.
