1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
use crate::cipher::{MessageEncrypter, MessageDecrypter};
use crate::error::TLSError;
use crate::msgs::message::{Message, BorrowMessage};
static SEQ_SOFT_LIMIT: u64 = 0xffff_ffff_ffff_0000u64;
static SEQ_HARD_LIMIT: u64 = 0xffff_ffff_ffff_fffeu64;
#[derive(PartialEq)]
enum DirectionState {
/// No keying material.
Invalid,
/// Keying material present, but not yet in use.
Prepared,
/// Keying material in use.
Active,
}
pub struct RecordLayer {
message_encrypter: Box<dyn MessageEncrypter>,
message_decrypter: Box<dyn MessageDecrypter>,
write_seq: u64,
read_seq: u64,
encrypt_state: DirectionState,
decrypt_state: DirectionState,
}
impl RecordLayer {
pub fn new() -> RecordLayer {
RecordLayer {
message_encrypter: MessageEncrypter::invalid(),
message_decrypter: MessageDecrypter::invalid(),
write_seq: 0,
read_seq: 0,
encrypt_state: DirectionState::Invalid,
decrypt_state: DirectionState::Invalid,
}
}
pub fn is_encrypting(&self) -> bool {
self.encrypt_state == DirectionState::Active
}
pub fn is_decrypting(&self) -> bool {
self.decrypt_state == DirectionState::Active
}
/// Prepare to use the given `MessageEncrypter` for future message encryption.
/// It is not used until you call `start_encrypting`.
pub fn prepare_message_encrypter(&mut self, cipher: Box<dyn MessageEncrypter>) {
self.message_encrypter = cipher;
self.write_seq = 0;
self.encrypt_state = DirectionState::Prepared;
}
/// Prepare to use the given `MessageDecrypter` for future message decryption.
/// It is not use duntil you call `start_decrypting`.
pub fn prepare_message_decrypter(&mut self, cipher: Box<dyn MessageDecrypter>) {
self.message_decrypter = cipher;
self.read_seq = 0;
self.decrypt_state = DirectionState::Prepared;
}
/// Start using the `MessageEncrypter` previously provided to the previous
/// call to `prepare_message_encrypter`.
pub fn start_encrypting(&mut self) {
debug_assert!(self.encrypt_state == DirectionState::Prepared);
self.encrypt_state = DirectionState::Active;
}
/// Start using the `MessageDecrypter` previously provided to the previous
/// call to `prepare_message_decrypter`.
pub fn start_decrypting(&mut self) {
debug_assert!(self.decrypt_state == DirectionState::Prepared);
self.decrypt_state = DirectionState::Active;
}
/// Set and start using the given `MessageEncrypter` for future outgoing
/// message encryption.
pub fn set_message_encrypter(&mut self, cipher: Box<dyn MessageEncrypter>) {
self.prepare_message_encrypter(cipher);
self.start_encrypting();
}
/// Set and start using the given `MessageDecrypter` for future incoming
/// message decryption.
pub fn set_message_decrypter(&mut self, cipher: Box<dyn MessageDecrypter>) {
self.prepare_message_decrypter(cipher);
self.start_decrypting();
}
/// Return true if the peer appears to getting close to encrypting
/// too many messages with this key.
///
/// Perhaps if we send an alert well before their counter wraps, a
/// buggy peer won't make a terrible mistake here?
///
/// Note that there's no reason to refuse to decrypt: the security
/// failure has already happened.
pub fn wants_close_before_decrypt(&self) -> bool {
self.read_seq == SEQ_SOFT_LIMIT
}
/// Return true if we are getting close to encrypting too many
/// messages with our encryption key.
pub fn wants_close_before_encrypt(&self) -> bool {
self.write_seq == SEQ_SOFT_LIMIT
}
/// Return true if we outright refuse to do anything with the
/// encryption key.
pub fn encrypt_exhausted(&self) -> bool {
self.write_seq >= SEQ_HARD_LIMIT
}
/// Decrypt a TLS message.
///
/// `encr` is a decoded message allegedly received from the peer.
/// If it can be decrypted, its decryption is returned. Otherwise,
/// an error is returned.
pub fn decrypt_incoming(&mut self, encr: Message) -> Result<Message, TLSError> {
debug_assert!(self.decrypt_state == DirectionState::Active);
let seq = self.read_seq;
self.read_seq += 1;
self.message_decrypter.decrypt(encr, seq)
}
/// Encrypt a TLS message.
///
/// `plain` is a TLS message we'd like to send. This function
/// panics if the requisite keying material hasn't been established yet.
pub fn encrypt_outgoing(&mut self, plain: BorrowMessage) -> Message {
debug_assert!(self.encrypt_state == DirectionState::Active);
assert!(!self.encrypt_exhausted());
let seq = self.write_seq;
self.write_seq += 1;
self.message_encrypter.encrypt(plain, seq).unwrap()
}
}