about summary refs log tree commit diff
path: root/tvix/nix-compat/src/wire/bytes/reader/mod.rs
blob: 3bc8fcf688c4de22b20f92ae52c6fea999c47a2f (plain) (blame)
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
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
use std::{
    io,
    ops::{Bound, RangeBounds},
    pin::Pin,
    task::{self, ready, Poll},
};
use tokio::io::{AsyncRead, ReadBuf};

use trailer::TrailerReader;
mod trailer;

/// Reads a "bytes wire packet" from the underlying reader.
/// The format is the same as in [crate::wire::bytes::read_bytes],
/// however this structure provides a [AsyncRead] interface,
/// allowing to not having to pass around the entire payload in memory.
///
/// After being constructed with the underlying reader and an allowed size,
/// subsequent requests to poll_read will return payload data until the end
/// of the packet is reached.
///
/// Internally, it will first read over the size packet, filling payload_size,
/// ensuring it fits allowed_size, then return payload data.
///
/// It will not return the final bytes before all padding has been successfully
/// consumed as well, but the full length of the reader must be consumed.
///
/// In case of an error due to size constraints, or in case of not reading
/// all the way to the end (and getting a EOF), the underlying reader is no
/// longer usable and might return garbage.
pub struct BytesReader<R> {
    state: State<R>,
}

#[derive(Debug)]
enum State<R> {
    Size {
        reader: Option<R>,
        /// Minimum length (inclusive)
        user_len_min: u64,
        /// Maximum length (inclusive)
        user_len_max: u64,
        filled: u8,
        buf: [u8; 8],
    },
    Body {
        reader: Option<R>,
        consumed: u64,
        user_len: u64,
    },
    Trailer(TrailerReader<R>),
}

impl<R> BytesReader<R>
where
    R: AsyncRead + Unpin,
{
    /// Constructs a new BytesReader, using the underlying passed reader.
    pub fn new<S: RangeBounds<u64>>(reader: R, allowed_size: S) -> Self {
        let user_len_min = match allowed_size.start_bound() {
            Bound::Included(&n) => n,
            Bound::Excluded(&n) => n.saturating_add(1),
            Bound::Unbounded => 0,
        };

        let user_len_max = match allowed_size.end_bound() {
            Bound::Included(&n) => n,
            Bound::Excluded(&n) => n.checked_sub(1).unwrap(),
            Bound::Unbounded => u64::MAX,
        };

        Self {
            state: State::Size {
                reader: Some(reader),
                user_len_min,
                user_len_max,
                filled: 0,
                buf: [0; 8],
            },
        }
    }

    /// Construct a new BytesReader with a known, and already-read size.
    pub fn with_size(reader: R, size: u64) -> Self {
        Self {
            state: State::Body {
                reader: Some(reader),
                consumed: 0,
                user_len: size,
            },
        }
    }
}

impl<R: AsyncRead + Unpin> AsyncRead for BytesReader<R> {
    fn poll_read(
        mut self: Pin<&mut Self>,
        cx: &mut task::Context,
        buf: &mut ReadBuf,
    ) -> Poll<io::Result<()>> {
        let this = &mut self.state;

        loop {
            match this {
                State::Size {
                    reader,
                    user_len_min,
                    user_len_max,
                    filled: 8,
                    buf,
                } => {
                    let reader = reader.take().unwrap();

                    let data_len = u64::from_le_bytes(*buf);
                    if data_len < *user_len_min || data_len > *user_len_max {
                        return Err(io::Error::new(io::ErrorKind::InvalidData, "invalid size"))
                            .into();
                    }

                    *this = State::Body {
                        reader: Some(reader),
                        consumed: 0,
                        user_len: data_len,
                    };
                }
                State::Size {
                    reader,
                    filled,
                    buf,
                    ..
                } => {
                    let reader = reader.as_mut().unwrap();

                    let mut read_buf = ReadBuf::new(&mut buf[..]);
                    read_buf.advance(*filled as usize);
                    ready!(Pin::new(reader).poll_read(cx, &mut read_buf))?;

                    let new_filled = read_buf.filled().len() as u8;
                    if *filled == new_filled {
                        return Err(io::ErrorKind::UnexpectedEof.into()).into();
                    }

                    *filled = new_filled;
                }
                State::Body {
                    reader,
                    consumed,
                    user_len,
                } => {
                    let body_len = *user_len & !7;
                    let remaining = body_len - *consumed;

                    let reader = if remaining == 0 {
                        let reader = reader.take().unwrap();
                        let user_len = (*user_len & 7) as u8;
                        *this = State::Trailer(TrailerReader::new(reader, user_len));
                        continue;
                    } else {
                        reader.as_mut().unwrap()
                    };

                    let mut bytes_read = 0;
                    ready!(with_limited(buf, remaining, |buf| {
                        let ret = Pin::new(reader).poll_read(cx, buf);
                        bytes_read = buf.initialized().len();
                        ret
                    }))?;

                    *consumed += bytes_read as u64;

                    return if bytes_read != 0 {
                        Ok(())
                    } else {
                        Err(io::ErrorKind::UnexpectedEof.into())
                    }
                    .into();
                }
                State::Trailer(reader) => {
                    return Pin::new(reader).poll_read(cx, buf);
                }
            }
        }
    }
}

/// Make a limited version of `buf`, consisting only of up to `n` bytes of the unfilled section, and call `f` with it.
/// After `f` returns, we propagate the filled cursor advancement back to `buf`.
fn with_limited<R>(buf: &mut ReadBuf, n: u64, f: impl FnOnce(&mut ReadBuf) -> R) -> R {
    let mut nbuf = buf.take(n.try_into().unwrap_or(usize::MAX));
    let ptr = nbuf.initialized().as_ptr();
    let ret = f(&mut nbuf);

    // SAFETY: `ReadBuf::take` only returns the *unfilled* section of `buf`,
    // so anything filled is new, initialized data.
    //
    // We verify that `nbuf` still points to the same buffer,
    // so we're sure it hasn't been swapped out.
    unsafe {
        // ensure our buffer hasn't been swapped out
        assert_eq!(nbuf.initialized().as_ptr(), ptr);

        let n = nbuf.filled().len();
        buf.assume_init(n);
        buf.advance(n);
    }

    ret
}

#[cfg(test)]
mod tests {
    use std::time::Duration;

    use crate::wire::bytes::{padding_len, write_bytes};
    use hex_literal::hex;
    use lazy_static::lazy_static;
    use rstest::rstest;
    use tokio::io::AsyncReadExt;
    use tokio_test::{assert_err, io::Builder};

    use super::*;

    /// The maximum length of bytes packets we're willing to accept in the test
    /// cases.
    const MAX_LEN: u64 = 1024;

    lazy_static! {
        pub static ref LARGE_PAYLOAD: Vec<u8> = (0..255).collect::<Vec<u8>>().repeat(4 * 1024);
    }

    /// Helper function, calling the (simpler) write_bytes with the payload.
    /// We use this to create data we want to read from the wire.
    async fn produce_packet_bytes(payload: &[u8]) -> Vec<u8> {
        let mut exp = vec![];
        write_bytes(&mut exp, payload).await.unwrap();
        exp
    }

    /// Read bytes packets of various length, and ensure read_to_end returns the
    /// expected payload.
    #[rstest]
    #[case::empty(&[])] // empty bytes packet
    #[case::size_1b(&[0xff])] // 1 bytes payload
    #[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding)
    #[case::size_9b( &hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding)
    #[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet
    #[tokio::test]
    async fn read_payload_correct(#[case] payload: &[u8]) {
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await)
            .build();

        let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64);
        let mut buf = Vec::new();
        r.read_to_end(&mut buf).await.expect("must succeed");

        assert_eq!(payload, &buf[..]);
    }

    /// Read bytes packets of various length, and ensure read_to_end returns the
    /// expected payload.
    #[rstest]
    #[case::empty(&[])] // empty bytes packet
    #[case::size_1b(&[0xff])] // 1 bytes payload
    #[case::size_8b(&hex!("0001020304050607"))] // 8 bytes payload (no padding)
    #[case::size_9b( &hex!("000102030405060708"))] // 9 bytes payload (7 bytes padding)
    #[case::size_1m(LARGE_PAYLOAD.as_slice())] // larger bytes packet
    #[tokio::test]
    async fn read_payload_correct_known(#[case] payload: &[u8]) {
        let packet = produce_packet_bytes(payload).await;

        let size = u64::from_le_bytes({
            let mut buf = [0; 8];
            buf.copy_from_slice(&packet[..8]);
            buf
        });

        let mut mock = Builder::new().read(&packet[8..]).build();

        let mut r = BytesReader::with_size(&mut mock, size);
        let mut buf = Vec::new();
        r.read_to_end(&mut buf).await.expect("must succeed");

        assert_eq!(payload, &buf[..]);
    }

    /// Fail if the bytes packet is larger than allowed
    #[tokio::test]
    async fn read_bigger_than_allowed_fail() {
        let payload = LARGE_PAYLOAD.as_slice();
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet
            .build();

        let mut r = BytesReader::new(&mut mock, ..2048);
        let mut buf = Vec::new();
        assert_err!(r.read_to_end(&mut buf).await);
    }

    /// Fail if the bytes packet is smaller than allowed
    #[tokio::test]
    async fn read_smaller_than_allowed_fail() {
        let payload = &[0x00, 0x01, 0x02];
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[0..8]) // We stop reading after the size packet
            .build();

        let mut r = BytesReader::new(&mut mock, 1024..2048);
        let mut buf = Vec::new();
        assert_err!(r.read_to_end(&mut buf).await);
    }

    /// Fail if the padding is not all zeroes
    #[tokio::test]
    async fn read_fail_if_nonzero_padding() {
        let payload = &[0x00, 0x01, 0x02];
        let mut packet_bytes = produce_packet_bytes(payload).await;
        // Flip some bits in the padding
        packet_bytes[12] = 0xff;
        let mut mock = Builder::new().read(&packet_bytes).build(); // We stop reading after the faulty bit

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);
        let mut buf = Vec::new();

        r.read_to_end(&mut buf).await.expect_err("must fail");
    }

    /// Start a 9 bytes payload packet, but have the underlying reader return
    /// EOF in the middle of the size packet (after 4 bytes).
    /// We should get an unexpected EOF error, already when trying to read the
    /// first byte (of payload)
    #[tokio::test]
    async fn read_9b_eof_during_size() {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[..4])
            .build();

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);
        let mut buf = [0u8; 1];

        assert_eq!(
            r.read_exact(&mut buf).await.expect_err("must fail").kind(),
            std::io::ErrorKind::UnexpectedEof
        );

        assert_eq!(&[0], &buf, "buffer should stay empty");
    }

    /// Start a 9 bytes payload packet, but have the underlying reader return
    /// EOF in the middle of the payload (4 bytes into the payload).
    /// We should get an unexpected EOF error, after reading the first 4 bytes
    /// (successfully).
    #[tokio::test]
    async fn read_9b_eof_during_payload() {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[..8 + 4])
            .build();

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);
        let mut buf = [0; 9];

        r.read_exact(&mut buf[..4]).await.expect("must succeed");

        assert_eq!(
            r.read_exact(&mut buf[4..=4])
                .await
                .expect_err("must fail")
                .kind(),
            std::io::ErrorKind::UnexpectedEof
        );
    }

    /// Start a 9 bytes payload packet, but don't supply the necessary padding.
    /// This is expected to always fail before returning the final data.
    #[rstest]
    #[case::before_padding(8 + 9)]
    #[case::during_padding(8 + 9 + 2)]
    #[case::after_padding(8 + 9 + padding_len(9) as usize - 1)]
    #[tokio::test]
    async fn read_9b_eof_after_payload(#[case] offset: usize) {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[..offset])
            .build();

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);

        // read_exact of the payload *body* will succeed, but a subsequent read will
        // return UnexpectedEof error.
        assert_eq!(r.read_exact(&mut [0; 8]).await.unwrap(), 8);
        assert_eq!(
            r.read_exact(&mut [0]).await.unwrap_err().kind(),
            std::io::ErrorKind::UnexpectedEof
        );
    }

    /// Start a 9 bytes payload packet, but return an error after a certain position.
    /// Ensure that error is propagated.
    #[rstest]
    #[case::during_size(4)]
    #[case::before_payload(8)]
    #[case::during_payload(8 + 4)]
    #[case::before_padding(8 + 4)]
    #[case::during_padding(8 + 9 + 2)]
    #[tokio::test]
    async fn propagate_error_from_reader(#[case] offset: usize) {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[..offset])
            .read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
            .build();

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);
        let mut buf = Vec::new();

        let err = r.read_to_end(&mut buf).await.expect_err("must fail");
        assert_eq!(
            err.kind(),
            std::io::ErrorKind::Other,
            "error kind must match"
        );

        assert_eq!(
            err.into_inner().unwrap().to_string(),
            "foo",
            "error payload must contain foo"
        );
    }

    /// If there's an error right after the padding, we don't propagate it, as
    /// we're done reading. We just return EOF.
    #[tokio::test]
    async fn no_error_after_eof() {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await)
            .read_error(std::io::Error::new(std::io::ErrorKind::Other, "foo"))
            .build();

        let mut r = BytesReader::new(&mut mock, ..MAX_LEN);
        let mut buf = Vec::new();

        r.read_to_end(&mut buf).await.expect("must succeed");
        assert_eq!(buf.as_slice(), payload);
    }

    /// Introduce various stalls in various places of the packet, to ensure we
    /// handle these cases properly, too.
    #[rstest]
    #[case::beginning(0)]
    #[case::before_payload(8)]
    #[case::during_payload(8 + 4)]
    #[case::before_padding(8 + 4)]
    #[case::during_padding(8 + 9 + 2)]
    #[tokio::test]
    async fn read_payload_correct_pending(#[case] offset: usize) {
        let payload = &hex!("FF0102030405060708");
        let mut mock = Builder::new()
            .read(&produce_packet_bytes(payload).await[..offset])
            .wait(Duration::from_nanos(0))
            .read(&produce_packet_bytes(payload).await[offset..])
            .build();

        let mut r = BytesReader::new(&mut mock, ..=LARGE_PAYLOAD.len() as u64);
        let mut buf = Vec::new();
        r.read_to_end(&mut buf).await.expect("must succeed");

        assert_eq!(payload, &buf[..]);
    }
}