4 extern cvar_t crypto_developer;
5 extern cvar_t crypto_aeslevel;
6 #define ENCRYPTION_REQUIRED (crypto_aeslevel.integer >= 3)
8 extern int crypto_keyfp_recommended_length; // applies to LOCAL IDs, and to ALL keys
10 #define CRYPTO_HEADERSIZE 31
11 // AES case causes 16 to 31 bytes overhead
12 // SHA256 case causes 16 bytes overhead as we truncate to 128bit
21 unsigned char dhkey[DHKEY_SIZE]; // shared key, not NUL terminated
22 char client_idfp[FP64_SIZE+1];
23 char client_keyfp[FP64_SIZE+1];
24 qbool client_issigned;
25 char server_idfp[FP64_SIZE+1];
26 char server_keyfp[FP64_SIZE+1];
27 qbool server_issigned;
34 void Crypto_Init(void);
35 void Crypto_Init_Commands(void);
36 void Crypto_LoadKeys(void); // NOTE: when this is called, the SV_LockThreadMutex MUST be active
37 void Crypto_Shutdown(void);
38 qbool Crypto_Available(void);
39 void sha256(unsigned char *out, const unsigned char *in, int n); // may ONLY be called if Crypto_Available()
40 const void *Crypto_EncryptPacket(crypto_t *crypto, const void *data_src, size_t len_src, void *data_dst, size_t *len_dst, size_t len);
41 const void *Crypto_DecryptPacket(crypto_t *crypto, const void *data_src, size_t len_src, void *data_dst, size_t *len_dst, size_t len);
42 #define CRYPTO_NOMATCH 0 // process as usual (packet was not used)
43 #define CRYPTO_MATCH 1 // process as usual (packet was used)
44 #define CRYPTO_DISCARD 2 // discard this packet
45 #define CRYPTO_REPLACE 3 // make the buffer the current packet
46 int Crypto_ClientParsePacket(const char *data_in, size_t len_in, char *data_out, size_t *len_out, lhnetaddress_t *peeraddress);
47 int Crypto_ServerParsePacket(const char *data_in, size_t len_in, char *data_out, size_t *len_out, lhnetaddress_t *peeraddress);
49 // if len_out is nonzero, the packet is to be sent to the client
51 qbool Crypto_ServerAppendToChallenge(const char *data_in, size_t len_in, char *data_out, size_t *len_out, size_t maxlen);
52 crypto_t *Crypto_ServerGetInstance(lhnetaddress_t *peeraddress);
53 qbool Crypto_FinishInstance(crypto_t *out, crypto_t *in); // also clears allocated memory, and frees the instance received by ServerGetInstance
54 const char *Crypto_GetInfoResponseDataString(void);
56 // retrieves a host key for an address (can be exposed to menuqc, or used by the engine to look up stored keys e.g. for server bookmarking)
57 // pointers may be NULL
58 qbool Crypto_RetrieveHostKey(lhnetaddress_t *peeraddress, int *keyid, char *keyfp, size_t keyfplen, char *idfp, size_t idfplen, int *aeslevel, qbool *issigned);
59 int Crypto_RetrieveLocalKey(int keyid, char *keyfp, size_t keyfplen, char *idfp, size_t idfplen, qbool *issigned); // return value: -1 if more to come, +1 if valid, 0 if end of list
61 size_t Crypto_SignData(const void *data, size_t datasize, int keyid, void *signed_data, size_t signed_size);
62 size_t Crypto_SignDataDetached(const void *data, size_t datasize, int keyid, void *signed_data, size_t signed_size);
69 // < accept (or: reject)
72 // < challenge SP <challenge> NUL vlen <size> d0pk <fingerprints I can auth to> NUL NUL <other fingerprints I accept>
75 // d0pk\cnt\0\challenge\<challenge>\aeslevel\<level> NUL <serverfp> NUL <clientfp>
77 // check if client would get accepted; if not, do "reject" now
78 // require non-control packets to be encrypted require non-control packets to be encrypted
79 // do not send anything yet do not send anything yet
80 // RESET to serverfp RESET to serverfp
81 // d0_blind_id_authenticate_with_private_id_start() = 1
82 // < d0pk\cnt\1\aes\<aesenabled> NUL *startdata*
83 // d0_blind_id_authenticate_with_private_id_challenge() = 1
84 // d0pk\cnt\2 NUL *challengedata* >
85 // d0_blind_id_authenticate_with_private_id_response() = 0
86 // < d0pk\cnt\3 NUL *responsedata*
87 // d0_blind_id_authenticate_with_private_id_verify() = 1
88 // store server's fingerprint NOW
89 // d0_blind_id_sessionkey_public_id() = 1 d0_blind_id_sessionkey_public_id() = 1
91 // IF clientfp AND NOT serverfp:
92 // RESET to clientfp RESET to clientfp
93 // d0_blind_id_authenticate_with_private_id_start() = 1
94 // d0pk\cnt\0\challenge\<challenge>\aeslevel\<level> NUL NUL <clientfp> NUL *startdata*
96 // check if client would get accepted; if not, do "reject" now
97 // require non-control packets to be encrypted require non-control packets to be encrypted
98 // d0_blind_id_authenticate_with_private_id_challenge() = 1
99 // < d0pk\cnt\5\aes\<aesenabled> NUL *challengedata*
101 // IF clientfp AND serverfp:
102 // RESET to clientfp RESET to clientfp
103 // d0_blind_id_authenticate_with_private_id_start() = 1
104 // d0pk\cnt\4 NUL *startdata* >
105 // d0_blind_id_authenticate_with_private_id_challenge() = 1
106 // < d0pk\cnt\5 NUL *challengedata*
109 // d0_blind_id_authenticate_with_private_id_response() = 0
110 // d0pk\cnt\6 NUL *responsedata* >
111 // d0_blind_id_authenticate_with_private_id_verify() = 1
112 // store client's fingerprint NOW
113 // d0_blind_id_sessionkey_public_id() = 1 d0_blind_id_sessionkey_public_id() = 1
114 // note: the ... is the "connect" message, except without the challenge. Reinterpret as regular connect message on server side
116 // enforce encrypted transmission (key is XOR of the two DH keys)
119 // < challenge (mere sync message)
122 // < accept (ALWAYS accept if connection is encrypted, ignore challenge as it had been checked before)
124 // commence with ingame protocol
128 // getchallenge NUL d0_blind_id: reply with challenge with added fingerprints
129 // cnt=0: IF server will auth, cnt=1, ELSE cnt=5
132 // cnt=6: send "challenge"
134 // challenge with added fingerprints: cnt=0; if client will auth but not server, append client auth start
136 // cnt=3: IF client will auth, cnt=4, ELSE rewrite as "challenge"
137 // cnt=5: cnt=6, server will continue by sending "challenge" (let's avoid sending two packets as response to one)
139 // accept empty "challenge", and challenge-less connect in case crypto protocol has executed and finished
140 // statusResponse and infoResponse get an added d0_blind_id key that lists
141 // the keys the server can auth with and to in key@ca SPACE key@ca notation
142 // any d0pk\ message has an appended "id" parameter; messages with an unexpected "id" are ignored to prevent errors from multiple concurrent auth runs
145 // comparison to OTR:
147 // - authentication: yes
148 // - deniability: no (attacker requires the temporary session key to prove you
149 // have sent a specific message, the private key itself does not suffice), no
150 // measures are taken to provide forgeability to even provide deniability
151 // against an attacker who knows the temporary session key, as using CTR mode
152 // for the encryption - which, together with deriving the MAC key from the
153 // encryption key, and MACing the ciphertexts instead of the plaintexts,
154 // would provide forgeability and thus deniability - requires longer
155 // encrypted packets and deniability was not a goal of this, as we may e.g.
156 // reserve the right to capture packet dumps + extra state info to prove a
157 // client/server has sent specific packets to prove cheating)
158 // - perfect forward secrecy: yes (session key is derived via DH key exchange)