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
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
#![allow(clippy::duplicate_mod)]

use crate::crypto::cipher::{AeadKey, Iv, Nonce};
use crate::error::Error;
use crate::quic;

use alloc::boxed::Box;

use super::ring_like::aead;

pub(crate) struct HeaderProtectionKey(aead::quic::HeaderProtectionKey);

impl HeaderProtectionKey {
    pub(crate) fn new(key: AeadKey, alg: &'static aead::quic::Algorithm) -> Self {
        Self(aead::quic::HeaderProtectionKey::new(alg, key.as_ref()).unwrap())
    }

    fn xor_in_place(
        &self,
        sample: &[u8],
        first: &mut u8,
        packet_number: &mut [u8],
        masked: bool,
    ) -> Result<(), Error> {
        // This implements "Header Protection Application" almost verbatim.
        // <https://datatracker.ietf.org/doc/html/rfc9001#section-5.4.1>

        let mask = self
            .0
            .new_mask(sample)
            .map_err(|_| Error::General("sample of invalid length".into()))?;

        // The `unwrap()` will not panic because `new_mask` returns a
        // non-empty result.
        let (first_mask, pn_mask) = mask.split_first().unwrap();

        // It is OK for the `mask` to be longer than `packet_number`,
        // but a valid `packet_number` will never be longer than `mask`.
        if packet_number.len() > pn_mask.len() {
            return Err(Error::General("packet number too long".into()));
        }

        // Infallible from this point on. Before this point, `first` and
        // `packet_number` are unchanged.

        const LONG_HEADER_FORM: u8 = 0x80;
        let bits = match *first & LONG_HEADER_FORM == LONG_HEADER_FORM {
            true => 0x0f,  // Long header: 4 bits masked
            false => 0x1f, // Short header: 5 bits masked
        };

        let first_plain = match masked {
            // When unmasking, use the packet length bits after unmasking
            true => *first ^ (first_mask & bits),
            // When masking, use the packet length bits before masking
            false => *first,
        };
        let pn_len = (first_plain & 0x03) as usize + 1;

        *first ^= first_mask & bits;
        for (dst, m) in packet_number
            .iter_mut()
            .zip(pn_mask)
            .take(pn_len)
        {
            *dst ^= m;
        }

        Ok(())
    }
}

impl quic::HeaderProtectionKey for HeaderProtectionKey {
    fn encrypt_in_place(
        &self,
        sample: &[u8],
        first: &mut u8,
        packet_number: &mut [u8],
    ) -> Result<(), Error> {
        self.xor_in_place(sample, first, packet_number, false)
    }

    fn decrypt_in_place(
        &self,
        sample: &[u8],
        first: &mut u8,
        packet_number: &mut [u8],
    ) -> Result<(), Error> {
        self.xor_in_place(sample, first, packet_number, true)
    }

    #[inline]
    fn sample_len(&self) -> usize {
        self.0.algorithm().sample_len()
    }
}

pub(crate) struct PacketKey {
    /// Encrypts or decrypts a packet's payload
    key: aead::LessSafeKey,
    /// Computes unique nonces for each packet
    iv: Iv,
}

impl PacketKey {
    pub(crate) fn new(key: AeadKey, iv: Iv, aead_algorithm: &'static aead::Algorithm) -> Self {
        Self {
            key: aead::LessSafeKey::new(
                aead::UnboundKey::new(aead_algorithm, key.as_ref()).unwrap(),
            ),
            iv,
        }
    }
}

impl quic::PacketKey for PacketKey {
    fn encrypt_in_place(
        &self,
        packet_number: u64,
        header: &[u8],
        payload: &mut [u8],
    ) -> Result<quic::Tag, Error> {
        let aad = aead::Aad::from(header);
        let nonce = aead::Nonce::assume_unique_for_key(Nonce::new(&self.iv, packet_number).0);
        let tag = self
            .key
            .seal_in_place_separate_tag(nonce, aad, payload)
            .map_err(|_| Error::EncryptError)?;
        Ok(quic::Tag::from(tag.as_ref()))
    }

    /// Decrypt a QUIC packet
    ///
    /// Takes the packet `header`, which is used as the additional authenticated data, and the
    /// `payload`, which includes the authentication tag.
    ///
    /// If the return value is `Ok`, the decrypted payload can be found in `payload`, up to the
    /// length found in the return value.
    fn decrypt_in_place<'a>(
        &self,
        packet_number: u64,
        header: &[u8],
        payload: &'a mut [u8],
    ) -> Result<&'a [u8], Error> {
        let payload_len = payload.len();
        let aad = aead::Aad::from(header);
        let nonce = aead::Nonce::assume_unique_for_key(Nonce::new(&self.iv, packet_number).0);
        self.key
            .open_in_place(nonce, aad, payload)
            .map_err(|_| Error::DecryptError)?;

        let plain_len = payload_len - self.key.algorithm().tag_len();
        Ok(&payload[..plain_len])
    }

    /// Tag length for the underlying AEAD algorithm
    #[inline]
    fn tag_len(&self) -> usize {
        self.key.algorithm().tag_len()
    }
}

pub(crate) struct KeyBuilder(
    pub(crate) &'static aead::Algorithm,
    pub(crate) &'static aead::quic::Algorithm,
);

impl quic::Algorithm for KeyBuilder {
    fn packet_key(&self, key: AeadKey, iv: Iv) -> Box<dyn quic::PacketKey> {
        Box::new(PacketKey::new(key, iv, self.0))
    }

    fn header_protection_key(&self, key: AeadKey) -> Box<dyn quic::HeaderProtectionKey> {
        Box::new(HeaderProtectionKey::new(key, self.1))
    }

    fn aead_key_len(&self) -> usize {
        self.0.key_len()
    }
}

#[cfg(test)]
mod tests {
    use crate::common_state::Side;
    use crate::crypto::tls13::OkmBlock;
    use crate::quic::*;
    use crate::test_provider::tls13::{
        TLS13_AES_128_GCM_SHA256_INTERNAL, TLS13_CHACHA20_POLY1305_SHA256_INTERNAL,
    };
    use std::dbg;

    fn test_short_packet(version: Version, expected: &[u8]) {
        const PN: u64 = 654360564;
        const SECRET: &[u8] = &[
            0x9a, 0xc3, 0x12, 0xa7, 0xf8, 0x77, 0x46, 0x8e, 0xbe, 0x69, 0x42, 0x27, 0x48, 0xad,
            0x00, 0xa1, 0x54, 0x43, 0xf1, 0x82, 0x03, 0xa0, 0x7d, 0x60, 0x60, 0xf6, 0x88, 0xf3,
            0x0f, 0x21, 0x63, 0x2b,
        ];

        let secret = OkmBlock::new(SECRET);
        let builder = KeyBuilder::new(
            &secret,
            version,
            TLS13_CHACHA20_POLY1305_SHA256_INTERNAL
                .quic
                .unwrap(),
            TLS13_CHACHA20_POLY1305_SHA256_INTERNAL.hkdf_provider,
        );
        let packet = builder.packet_key();
        let hpk = builder.header_protection_key();

        const PLAIN: &[u8] = &[0x42, 0x00, 0xbf, 0xf4, 0x01];

        let mut buf = PLAIN.to_vec();
        let (header, payload) = buf.split_at_mut(4);
        let tag = packet
            .encrypt_in_place(PN, header, payload)
            .unwrap();
        buf.extend(tag.as_ref());

        let pn_offset = 1;
        let (header, sample) = buf.split_at_mut(pn_offset + 4);
        let (first, rest) = header.split_at_mut(1);
        let sample = &sample[..hpk.sample_len()];
        hpk.encrypt_in_place(sample, &mut first[0], dbg!(rest))
            .unwrap();

        assert_eq!(&buf, expected);

        let (header, sample) = buf.split_at_mut(pn_offset + 4);
        let (first, rest) = header.split_at_mut(1);
        let sample = &sample[..hpk.sample_len()];
        hpk.decrypt_in_place(sample, &mut first[0], rest)
            .unwrap();

        let (header, payload_tag) = buf.split_at_mut(4);
        let plain = packet
            .decrypt_in_place(PN, header, payload_tag)
            .unwrap();

        assert_eq!(plain, &PLAIN[4..]);
    }

    #[test]
    fn short_packet_header_protection() {
        // https://www.rfc-editor.org/rfc/rfc9001.html#name-chacha20-poly1305-short-hea
        test_short_packet(
            Version::V1,
            &[
                0x4c, 0xfe, 0x41, 0x89, 0x65, 0x5e, 0x5c, 0xd5, 0x5c, 0x41, 0xf6, 0x90, 0x80, 0x57,
                0x5d, 0x79, 0x99, 0xc2, 0x5a, 0x5b, 0xfb,
            ],
        );
    }

    #[test]
    fn key_update_test_vector() {
        fn equal_okm(x: &OkmBlock, y: &OkmBlock) -> bool {
            x.as_ref() == y.as_ref()
        }

        let mut secrets = Secrets::new(
            // Constant dummy values for reproducibility
            OkmBlock::new(
                &[
                    0xb8, 0x76, 0x77, 0x08, 0xf8, 0x77, 0x23, 0x58, 0xa6, 0xea, 0x9f, 0xc4, 0x3e,
                    0x4a, 0xdd, 0x2c, 0x96, 0x1b, 0x3f, 0x52, 0x87, 0xa6, 0xd1, 0x46, 0x7e, 0xe0,
                    0xae, 0xab, 0x33, 0x72, 0x4d, 0xbf,
                ][..],
            ),
            OkmBlock::new(
                &[
                    0x42, 0xdc, 0x97, 0x21, 0x40, 0xe0, 0xf2, 0xe3, 0x98, 0x45, 0xb7, 0x67, 0x61,
                    0x34, 0x39, 0xdc, 0x67, 0x58, 0xca, 0x43, 0x25, 0x9b, 0x87, 0x85, 0x06, 0x82,
                    0x4e, 0xb1, 0xe4, 0x38, 0xd8, 0x55,
                ][..],
            ),
            TLS13_AES_128_GCM_SHA256_INTERNAL,
            TLS13_AES_128_GCM_SHA256_INTERNAL
                .quic
                .unwrap(),
            Side::Client,
            Version::V1,
        );
        secrets.update();

        assert!(equal_okm(
            &secrets.client,
            &OkmBlock::new(
                &[
                    0x42, 0xca, 0xc8, 0xc9, 0x1c, 0xd5, 0xeb, 0x40, 0x68, 0x2e, 0x43, 0x2e, 0xdf,
                    0x2d, 0x2b, 0xe9, 0xf4, 0x1a, 0x52, 0xca, 0x6b, 0x22, 0xd8, 0xe6, 0xcd, 0xb1,
                    0xe8, 0xac, 0xa9, 0x6, 0x1f, 0xce
                ][..]
            )
        ));
        assert!(equal_okm(
            &secrets.server,
            &OkmBlock::new(
                &[
                    0xeb, 0x7f, 0x5e, 0x2a, 0x12, 0x3f, 0x40, 0x7d, 0xb4, 0x99, 0xe3, 0x61, 0xca,
                    0xe5, 0x90, 0xd4, 0xd9, 0x92, 0xe1, 0x4b, 0x7a, 0xce, 0x3, 0xc2, 0x44, 0xe0,
                    0x42, 0x21, 0x15, 0xb6, 0xd3, 0x8a
                ][..]
            )
        ));
    }

    #[test]
    fn short_packet_header_protection_v2() {
        // https://www.ietf.org/archive/id/draft-ietf-quic-v2-10.html#name-chacha20-poly1305-short-head
        test_short_packet(
            Version::V2,
            &[
                0x55, 0x58, 0xb1, 0xc6, 0x0a, 0xe7, 0xb6, 0xb9, 0x32, 0xbc, 0x27, 0xd7, 0x86, 0xf4,
                0xbc, 0x2b, 0xb2, 0x0f, 0x21, 0x62, 0xba,
            ],
        );
    }

    #[test]
    fn initial_test_vector_v2() {
        // https://www.ietf.org/archive/id/draft-ietf-quic-v2-10.html#name-sample-packet-protection-2
        let icid = [0x83, 0x94, 0xc8, 0xf0, 0x3e, 0x51, 0x57, 0x08];
        let server = Keys::initial(
            Version::V2,
            TLS13_AES_128_GCM_SHA256_INTERNAL,
            TLS13_AES_128_GCM_SHA256_INTERNAL
                .quic
                .unwrap(),
            &icid,
            Side::Server,
        );
        let mut server_payload = [
            0x02, 0x00, 0x00, 0x00, 0x00, 0x06, 0x00, 0x40, 0x5a, 0x02, 0x00, 0x00, 0x56, 0x03,
            0x03, 0xee, 0xfc, 0xe7, 0xf7, 0xb3, 0x7b, 0xa1, 0xd1, 0x63, 0x2e, 0x96, 0x67, 0x78,
            0x25, 0xdd, 0xf7, 0x39, 0x88, 0xcf, 0xc7, 0x98, 0x25, 0xdf, 0x56, 0x6d, 0xc5, 0x43,
            0x0b, 0x9a, 0x04, 0x5a, 0x12, 0x00, 0x13, 0x01, 0x00, 0x00, 0x2e, 0x00, 0x33, 0x00,
            0x24, 0x00, 0x1d, 0x00, 0x20, 0x9d, 0x3c, 0x94, 0x0d, 0x89, 0x69, 0x0b, 0x84, 0xd0,
            0x8a, 0x60, 0x99, 0x3c, 0x14, 0x4e, 0xca, 0x68, 0x4d, 0x10, 0x81, 0x28, 0x7c, 0x83,
            0x4d, 0x53, 0x11, 0xbc, 0xf3, 0x2b, 0xb9, 0xda, 0x1a, 0x00, 0x2b, 0x00, 0x02, 0x03,
            0x04,
        ];
        let mut server_header = [
            0xd1, 0x6b, 0x33, 0x43, 0xcf, 0x00, 0x08, 0xf0, 0x67, 0xa5, 0x50, 0x2a, 0x42, 0x62,
            0xb5, 0x00, 0x40, 0x75, 0x00, 0x01,
        ];
        let tag = server
            .local
            .packet
            .encrypt_in_place(1, &server_header, &mut server_payload)
            .unwrap();
        let (first, rest) = server_header.split_at_mut(1);
        let rest_len = rest.len();
        server
            .local
            .header
            .encrypt_in_place(
                &server_payload[2..18],
                &mut first[0],
                &mut rest[rest_len - 2..],
            )
            .unwrap();
        let mut server_packet = server_header.to_vec();
        server_packet.extend(server_payload);
        server_packet.extend(tag.as_ref());
        let expected_server_packet = [
            0xdc, 0x6b, 0x33, 0x43, 0xcf, 0x00, 0x08, 0xf0, 0x67, 0xa5, 0x50, 0x2a, 0x42, 0x62,
            0xb5, 0x00, 0x40, 0x75, 0xd9, 0x2f, 0xaa, 0xf1, 0x6f, 0x05, 0xd8, 0xa4, 0x39, 0x8c,
            0x47, 0x08, 0x96, 0x98, 0xba, 0xee, 0xa2, 0x6b, 0x91, 0xeb, 0x76, 0x1d, 0x9b, 0x89,
            0x23, 0x7b, 0xbf, 0x87, 0x26, 0x30, 0x17, 0x91, 0x53, 0x58, 0x23, 0x00, 0x35, 0xf7,
            0xfd, 0x39, 0x45, 0xd8, 0x89, 0x65, 0xcf, 0x17, 0xf9, 0xaf, 0x6e, 0x16, 0x88, 0x6c,
            0x61, 0xbf, 0xc7, 0x03, 0x10, 0x6f, 0xba, 0xf3, 0xcb, 0x4c, 0xfa, 0x52, 0x38, 0x2d,
            0xd1, 0x6a, 0x39, 0x3e, 0x42, 0x75, 0x75, 0x07, 0x69, 0x80, 0x75, 0xb2, 0xc9, 0x84,
            0xc7, 0x07, 0xf0, 0xa0, 0x81, 0x2d, 0x8c, 0xd5, 0xa6, 0x88, 0x1e, 0xaf, 0x21, 0xce,
            0xda, 0x98, 0xf4, 0xbd, 0x23, 0xf6, 0xfe, 0x1a, 0x3e, 0x2c, 0x43, 0xed, 0xd9, 0xce,
            0x7c, 0xa8, 0x4b, 0xed, 0x85, 0x21, 0xe2, 0xe1, 0x40,
        ];
        assert_eq!(server_packet[..], expected_server_packet[..]);
    }
}