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
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
use core::fmt;

use crate::common_state::Protocol;
use crate::crypto::cipher::{AeadKey, Iv};
use crate::crypto::{self, KeyExchangeAlgorithm};
use crate::enums::{CipherSuite, SignatureAlgorithm, SignatureScheme};
use crate::msgs::handshake::ALL_KEY_EXCHANGE_ALGORITHMS;
#[cfg(feature = "tls12")]
use crate::tls12::Tls12CipherSuite;
use crate::tls13::Tls13CipherSuite;
#[cfg(feature = "tls12")]
use crate::versions::TLS12;
use crate::versions::{SupportedProtocolVersion, TLS13};

/// Common state for cipher suites (both for TLS 1.2 and TLS 1.3)
pub struct CipherSuiteCommon {
    /// The TLS enumeration naming this cipher suite.
    pub suite: CipherSuite,

    /// Which hash function the suite uses.
    pub hash_provider: &'static dyn crypto::hash::Hash,

    /// Number of TCP-TLS messages that can be safely encrypted with a single key of this type
    ///
    /// Once a `MessageEncrypter` produced for this suite has encrypted more than
    /// `confidentiality_limit` messages, an attacker gains an advantage in distinguishing it
    /// from an ideal pseudorandom permutation (PRP).
    ///
    /// This is to be set on the assumption that messages are maximally sized --
    /// each is 2<sup>14</sup> bytes. It **does not** consider confidentiality limits for
    /// QUIC connections - see the [`quic::KeyBuilder.confidentiality_limit`] field for
    /// this context.
    ///
    /// For AES-GCM implementations, this should be set to 2<sup>24</sup> to limit attack
    /// probability to one in 2<sup>60</sup>.  See [AEBounds] (Table 1) and [draft-irtf-aead-limits-08]:
    ///
    /// ```python
    /// >>> p = 2 ** -60
    /// >>> L = (2 ** 14 // 16) + 1
    /// >>> qlim = (math.sqrt(p) * (2 ** (129 // 2)) - 1) / (L + 1)
    /// >>> print(int(qlim).bit_length())
    /// 24
    /// ```
    /// [AEBounds]: https://eprint.iacr.org/2024/051.pdf
    /// [draft-irtf-aead-limits-08]: https://www.ietf.org/archive/id/draft-irtf-cfrg-aead-limits-08.html#section-5.1.1
    ///
    /// For chacha20-poly1305 implementations, this should be set to `u64::MAX`:
    /// see <https://www.ietf.org/archive/id/draft-irtf-cfrg-aead-limits-08.html#section-5.2.1>
    pub confidentiality_limit: u64,
}

impl CipherSuiteCommon {
    /// Return `true` if this is backed by a FIPS-approved implementation.
    ///
    /// This means all the constituent parts that do cryptography return `true` for `fips()`.
    pub fn fips(&self) -> bool {
        self.hash_provider.fips()
    }
}

/// A cipher suite supported by rustls.
///
/// This type carries both configuration and implementation. Compare with
/// [`CipherSuite`], which carries solely a cipher suite identifier.
#[derive(Clone, Copy, PartialEq)]
pub enum SupportedCipherSuite {
    /// A TLS 1.2 cipher suite
    #[cfg(feature = "tls12")]
    Tls12(&'static Tls12CipherSuite),
    /// A TLS 1.3 cipher suite
    Tls13(&'static Tls13CipherSuite),
}

impl SupportedCipherSuite {
    /// The cipher suite's identifier
    pub fn suite(&self) -> CipherSuite {
        self.common().suite
    }

    /// The hash function the ciphersuite uses.
    pub(crate) fn hash_provider(&self) -> &'static dyn crypto::hash::Hash {
        self.common().hash_provider
    }

    pub(crate) fn common(&self) -> &CipherSuiteCommon {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(inner) => &inner.common,
            Self::Tls13(inner) => &inner.common,
        }
    }

    /// Return the inner `Tls13CipherSuite` for this suite, if it is a TLS1.3 suite.
    pub fn tls13(&self) -> Option<&'static Tls13CipherSuite> {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(_) => None,
            Self::Tls13(inner) => Some(inner),
        }
    }

    /// Return supported protocol version for the cipher suite.
    pub fn version(&self) -> &'static SupportedProtocolVersion {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(_) => &TLS12,
            Self::Tls13(_) => &TLS13,
        }
    }

    /// Return true if this suite is usable for a key only offering `sig_alg`
    /// signatures.  This resolves to true for all TLS1.3 suites.
    pub fn usable_for_signature_algorithm(&self, _sig_alg: SignatureAlgorithm) -> bool {
        match self {
            Self::Tls13(_) => true, // no constraint expressed by ciphersuite (e.g., TLS1.3)
            #[cfg(feature = "tls12")]
            Self::Tls12(inner) => inner
                .sign
                .iter()
                .any(|scheme| scheme.algorithm() == _sig_alg),
        }
    }

    /// Return true if this suite is usable for the given [`Protocol`].
    ///
    /// All cipher suites are usable for TCP-TLS.  Only TLS1.3 suites
    /// with `Tls13CipherSuite::quic` provided are usable for QUIC.
    pub(crate) fn usable_for_protocol(&self, proto: Protocol) -> bool {
        match proto {
            Protocol::Tcp => true,
            Protocol::Quic => self
                .tls13()
                .and_then(|cs| cs.quic)
                .is_some(),
        }
    }

    /// Return `true` if this is backed by a FIPS-approved implementation.
    pub fn fips(&self) -> bool {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(cs) => cs.fips(),
            Self::Tls13(cs) => cs.fips(),
        }
    }

    /// Return the list of `KeyExchangeAlgorithm`s supported by this cipher suite.
    ///
    /// TLS 1.3 cipher suites support both ECDHE and DHE key exchange, but TLS 1.2 suites
    /// support one or the other.
    pub(crate) fn key_exchange_algorithms(&self) -> &[KeyExchangeAlgorithm] {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(tls12) => core::slice::from_ref(&tls12.kx),
            Self::Tls13(_) => ALL_KEY_EXCHANGE_ALGORITHMS,
        }
    }

    /// Say if the given `KeyExchangeAlgorithm` is supported by this cipher suite.
    ///
    /// TLS 1.3 cipher suites support all key exchange types, but TLS 1.2 suites
    /// support only one.
    pub(crate) fn usable_for_kx_algorithm(&self, _kxa: KeyExchangeAlgorithm) -> bool {
        match self {
            #[cfg(feature = "tls12")]
            Self::Tls12(tls12) => tls12.kx == _kxa,
            Self::Tls13(_) => true,
        }
    }
}

impl fmt::Debug for SupportedCipherSuite {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.suite().fmt(f)
    }
}

/// Return true if `sigscheme` is usable by any of the given suites.
pub(crate) fn compatible_sigscheme_for_suites(
    sigscheme: SignatureScheme,
    common_suites: &[SupportedCipherSuite],
) -> bool {
    let sigalg = sigscheme.algorithm();
    common_suites
        .iter()
        .any(|&suite| suite.usable_for_signature_algorithm(sigalg))
}

/// Secrets for transmitting/receiving data over a TLS session.
///
/// After performing a handshake with rustls, these secrets can be extracted
/// to configure kTLS for a socket, and have the kernel take over encryption
/// and/or decryption.
pub struct ExtractedSecrets {
    /// sequence number and secrets for the "tx" (transmit) direction
    pub tx: (u64, ConnectionTrafficSecrets),

    /// sequence number and secrets for the "rx" (receive) direction
    pub rx: (u64, ConnectionTrafficSecrets),
}

/// [ExtractedSecrets] minus the sequence numbers
pub(crate) struct PartiallyExtractedSecrets {
    /// secrets for the "tx" (transmit) direction
    pub(crate) tx: ConnectionTrafficSecrets,

    /// secrets for the "rx" (receive) direction
    pub(crate) rx: ConnectionTrafficSecrets,
}

/// Secrets used to encrypt/decrypt data in a TLS session.
///
/// These can be used to configure kTLS for a socket in one direction.
/// The only other piece of information needed is the sequence number,
/// which is in [ExtractedSecrets].
#[non_exhaustive]
pub enum ConnectionTrafficSecrets {
    /// Secrets for the AES_128_GCM AEAD algorithm
    Aes128Gcm {
        /// AEAD Key
        key: AeadKey,
        /// Initialization vector
        iv: Iv,
    },

    /// Secrets for the AES_256_GCM AEAD algorithm
    Aes256Gcm {
        /// AEAD Key
        key: AeadKey,
        /// Initialization vector
        iv: Iv,
    },

    /// Secrets for the CHACHA20_POLY1305 AEAD algorithm
    Chacha20Poly1305 {
        /// AEAD Key
        key: AeadKey,
        /// Initialization vector
        iv: Iv,
    },
}

test_for_each_provider! {
    use std::println;

    use provider::tls13::*;

    #[test]
    fn test_scs_is_debug() {
        println!("{:?}", provider::ALL_CIPHER_SUITES);
    }

    #[test]
    fn test_can_resume_to() {
        assert!(TLS13_AES_128_GCM_SHA256
            .tls13()
            .unwrap()
            .can_resume_from(TLS13_CHACHA20_POLY1305_SHA256_INTERNAL)
            .is_some());
        assert!(TLS13_AES_256_GCM_SHA384
            .tls13()
            .unwrap()
            .can_resume_from(TLS13_CHACHA20_POLY1305_SHA256_INTERNAL)
            .is_none());
    }
}