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
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
//! Key type wrappers of various kinds used in onion services.
//!
//! (We define wrappers here as a safety net against confusing one kind of
//! key for another: without a system like this, it can get pretty hard making
//! sure that each key is used only in the right way.)

use std::fmt::{self, Debug, Display};
use std::str::FromStr;

use digest::Digest;
use itertools::{chain, Itertools};
use thiserror::Error;
use tor_basic_utils::{impl_debug_hex, StrExt as _};
use tor_llcrypto::d::Sha3_256;
use tor_llcrypto::pk::ed25519::{Ed25519PublicKey, Signer};
use tor_llcrypto::pk::{curve25519, ed25519, keymanip};
use tor_llcrypto::util::ct::CtByteArray;

use crate::macros::{define_bytes, define_pk_keypair};
use crate::time::TimePeriod;

#[allow(deprecated)]
pub use hs_client_intro_auth::{HsClientIntroAuthKey, HsClientIntroAuthKeypair};

define_bytes! {
/// The identity of a v3 onion service. (KP_hs_id)
///
/// This is the decoded and validated ed25519 public key that is encoded as a
/// `${base32}.onion` address.  When expanded, it is a public key whose
/// corresponding secret key is controlled by the onion service.
///
/// `HsId`'s `Display` and `FromStr` representation is the domain name
/// `"${base32}.onion"`.  (Without any subdomains.)
///
/// Note: This is a separate type from [`HsIdKey`] because it is about 6x
/// smaller.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct HsId([u8; 32]);
}

impl fmt::LowerHex for HsId {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "HsId(0x")?;
        for v in self.0.as_ref() {
            write!(f, "{:02x}", v)?;
        }
        write!(f, ")")?;
        Ok(())
    }
}

impl Debug for HsId {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "HsId({})", self)
    }
}

define_pk_keypair! {
/// The identity of a v3 onion service, expanded into a public key. (KP_hs_id)
///
/// This is the decoded and validated ed25519 public key that is encoded as
/// a `${base32}.onion` address.
///
/// This key is not used to sign or validate anything on its own; instead, it is
/// used to derive a [`HsBlindIdKey`].
///
/// Note: This is a separate type from [`HsId`] because it is about 6x
/// larger.  It is an expanded form, used for doing actual cryptography.
//
// NOTE: This is called the "master" key in rend-spec-v3, but we're deprecating
// that vocabulary generally.
pub struct HsIdKey(ed25519::PublicKey) /
    ///
    /// This is stored as an expanded secret key, for compatibility with the C
    /// tor implementation, and in order to support custom-generated addresses.
    ///
    /// (About custom generated addresses: When making a vanity onion address,
    /// it is inefficient to search for a compact secret key `s` and compute
    /// `SHA512(s)=(a,r)` and `A=aB` until you find an `s` that produces an `A`
    /// that you like.  Instead, most folks use the algorithm of
    /// rend-spec-v3.txt appendix C, wherein you search for a good `a` directly
    /// by repeatedly adding `8B` to A until you find an `A` you like.  The only
    /// major drawback is that once you have found a good `a`, you can't get an
    /// `s` for it, since you presumably can't find SHA512 preimages.  And that
    /// is why we store the private key in (a,r) form.)
    HsIdKeypair(ed25519::ExpandedKeypair);
}

impl HsIdKey {
    /// Return a representation of this key as an [`HsId`].
    ///
    /// ([`HsId`] is much smaller, and easier to store.)
    pub fn id(&self) -> HsId {
        HsId(self.0.to_bytes().into())
    }
}
impl TryFrom<HsId> for HsIdKey {
    type Error = signature::Error;

    fn try_from(value: HsId) -> Result<Self, Self::Error> {
        ed25519::PublicKey::from_bytes(value.0.as_ref()).map(HsIdKey)
    }
}
impl From<HsIdKey> for HsId {
    fn from(value: HsIdKey) -> Self {
        value.id()
    }
}

impl From<&HsIdKeypair> for HsIdKey {
    fn from(value: &HsIdKeypair) -> Self {
        Self(*value.0.public())
    }
}

/// VERSION from rend-spec-v3 s.6 \[ONIONADDRESS]
const HSID_ONION_VERSION: u8 = 0x03;

/// The fixed string `.onion`
pub const HSID_ONION_SUFFIX: &str = ".onion";

impl Display for HsId {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // rend-spec-v3 s.6 [ONIONADDRESS]
        let checksum = self.onion_checksum();
        let binary = chain!(self.0.as_ref(), &checksum, &[HSID_ONION_VERSION],)
            .cloned()
            .collect_vec();
        let mut b32 = data_encoding::BASE32_NOPAD.encode(&binary);
        b32.make_ascii_lowercase();
        write!(f, "{}{}", b32, HSID_ONION_SUFFIX)
    }
}

impl safelog::Redactable for HsId {
    // We here display some of the end.  We don't want to display the
    // *start* because vanity domains, which would perhaps suffer from
    // reduced deniability.
    fn display_redacted(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let unredacted = self.to_string();
        /// Length of the base32 data part of the address
        const DATA: usize = 56;
        assert_eq!(unredacted.len(), DATA + HSID_ONION_SUFFIX.len());

        // We show this part of the domain:
        //     e     n     l     5     s     i     d     .onion
        //   KKKKK KKKKK KCCCC CCCCC CCCCC CCVVV VVVVV
        //                           ^^^^^^^^^^^^^^^^^ ^^^^^^^^^
        // This contains 3 characters of base32, which is 15 bits.
        // 8 of those bits are the version, which is currently always 0x03.
        // So we are showing 7 bits derived from the site key.

        write!(f, "???{}", &unredacted[DATA - 3..])
    }
}

impl FromStr for HsId {
    type Err = HsIdParseError;
    fn from_str(s: &str) -> Result<Self, HsIdParseError> {
        use HsIdParseError as PE;

        let s = s
            .strip_suffix_ignore_ascii_case(HSID_ONION_SUFFIX)
            .ok_or(PE::NotOnionDomain)?;

        if s.contains('.') {
            return Err(PE::HsIdContainsSubdomain);
        }

        // We must convert to uppercase because RFC4648 says so and that's what Rust
        // ecosystem libraries for base32 expect.  All this allocation and copying is
        // still probably less work than the SHA3 for the checksum.
        // However, we are going to use this function to *detect* and filter .onion
        // addresses, so it should have a fast path to reject thm.
        let mut s = s.to_owned();
        s.make_ascii_uppercase();

        // Ideally we'd have code here that would provide a clear error message if
        // we encounter an address with the wrong version.  But that is very complicated
        // because the encoding format does not make that at all convenient.
        // So instead our errors tell you what aspect of the parsing went wrong.
        let binary = data_encoding::BASE32_NOPAD.decode(s.as_bytes())?;
        let mut binary = tor_bytes::Reader::from_slice(&binary);

        let pubkey: [u8; 32] = binary.extract()?;
        let checksum: [u8; 2] = binary.extract()?;
        let version: u8 = binary.extract()?;
        let tentative = HsId(pubkey.into());

        // Check version before checksum; maybe a future version does checksum differently
        if version != HSID_ONION_VERSION {
            return Err(PE::UnsupportedVersion(version));
        }
        if checksum != tentative.onion_checksum() {
            return Err(PE::WrongChecksum);
        }
        Ok(tentative)
    }
}

/// Error that can occur parsing an `HsId` from a v3 `.onion` domain name
#[derive(Error, Clone, Debug)]
#[non_exhaustive]
pub enum HsIdParseError {
    /// Supplied domain name string does not end in `.onion`
    #[error("Domain name does not end in .onion")]
    NotOnionDomain,

    /// Base32 decoding failed
    ///
    /// `position` is indeed the (byte) position in the input string
    #[error("Invalid base32 in .onion address")]
    InvalidBase32(#[from] data_encoding::DecodeError),

    /// Encoded binary data is invalid
    #[error("Invalid encoded binary data in .onion address")]
    InvalidData(#[from] tor_bytes::Error),

    /// Unsupported `.onion` address version
    #[error("Unsupported .onion address version, v{0}")]
    UnsupportedVersion(u8),

    /// Checksum failed
    #[error("Checksum failed, .onion address corrupted")]
    WrongChecksum,

    /// If you try to parse a domain with subdomains as an `HsId`
    #[error("`.onion` address with subdomain passed where not expected")]
    HsIdContainsSubdomain,
}

impl tor_error::HasKind for HsIdParseError {
    fn kind(&self) -> tor_error::ErrorKind {
        use tor_error::ErrorKind as EK;
        match self {
            HsIdParseError::InvalidBase32(_)
            | HsIdParseError::InvalidData(_)
            | HsIdParseError::UnsupportedVersion(_)
            | HsIdParseError::WrongChecksum => EK::OnionServiceAddressInvalid,
            HsIdParseError::NotOnionDomain | HsIdParseError::HsIdContainsSubdomain => {
                EK::BadApiUsage
            }
        }
    }
}

impl HsId {
    /// Calculates CHECKSUM rend-spec-v3 s.6 \[ONIONADDRESS]
    fn onion_checksum(&self) -> [u8; 2] {
        let mut h = Sha3_256::new();
        h.update(b".onion checksum");
        h.update(self.0.as_ref());
        h.update([HSID_ONION_VERSION]);
        h.finalize()[..2]
            .try_into()
            .expect("slice of fixed size wasn't that size")
    }
}

impl HsIdKey {
    /// Derive the blinded key and subcredential for this identity during `cur_period`.
    pub fn compute_blinded_key(
        &self,
        cur_period: TimePeriod,
    ) -> Result<(HsBlindIdKey, crate::Subcredential), keymanip::BlindingError> {
        // TODO: someday we might want to support this kinds of a shared secret
        // in our protocol. (C tor does not.)  If we did, it would be an
        // additional piece of information about an onion service that you would
        // need to know in order to connect to it.
        //
        // This is the "optional secret s" mentioned in the key-blinding
        // appendix to rend-spec.txt.
        let secret = b"";
        let h = self.blinding_factor(secret, cur_period);

        let blinded_key = keymanip::blind_pubkey(&self.0, h)?.into();
        // rend-spec-v3 section 2.1
        let subcredential = self.compute_subcredential(&blinded_key, cur_period);

        Ok((blinded_key, subcredential))
    }

    /// Given a time period and a blinded public key, compute the subcredential.
    pub fn compute_subcredential(
        &self,
        blinded_key: &HsBlindIdKey,
        cur_period: TimePeriod,
    ) -> crate::Subcredential {
        // rend-spec-v3 section 2.1
        let subcredential_bytes: [u8; 32] = {
            // N_hs_subcred = H("subcredential" | N_hs_cred | blinded-public-key).
            // where
            //    N_hs_cred = H("credential" | public-identity-key)
            let n_hs_cred: [u8; 32] = {
                let mut h = Sha3_256::new();
                h.update(b"credential");
                h.update(self.0.as_bytes());
                h.finalize().into()
            };
            let mut h = Sha3_256::new();
            h.update(b"subcredential");
            h.update(n_hs_cred);
            h.update(blinded_key.as_ref());
            h.finalize().into()
        };

        subcredential_bytes.into()
    }

    /// Compute the 32-byte "blinding factor" used to compute blinded public
    /// (and secret) keys.
    ///
    /// Returns the value `h = H(...)`, from rend-spec-v3 A.2., before clamping.
    fn blinding_factor(&self, secret: &[u8], cur_period: TimePeriod) -> [u8; 32] {
        // rend-spec-v3 appendix A.2
        // We generate our key blinding factor as
        //    h = H(BLIND_STRING | A | s | B | N)
        // Where:
        //    H is SHA3-256.
        //    A is this public key.
        //    BLIND_STRING = "Derive temporary signing key" | INT_1(0)
        //    s is an optional secret (not implemented here.)
        //    B is the ed25519 basepoint.
        //    N = "key-blind" || INT_8(period_num) || INT_8(period_length).

        /// String used as part of input to blinding hash.
        const BLIND_STRING: &[u8] = b"Derive temporary signing key\0";
        /// String representation of our Ed25519 basepoint.
        const ED25519_BASEPOINT: &[u8] =
            b"(15112221349535400772501151409588531511454012693041857206046113283949847762202, \
               46316835694926478169428394003475163141307993866256225615783033603165251855960)";

        let mut h = Sha3_256::new();
        h.update(BLIND_STRING);
        h.update(self.0.as_bytes());
        h.update(secret);
        h.update(ED25519_BASEPOINT);
        h.update(b"key-blind");
        h.update(cur_period.interval_num.to_be_bytes());
        h.update((u64::from(cur_period.length.as_minutes())).to_be_bytes());

        h.finalize().into()
    }
}

impl HsIdKeypair {
    /// Derive the blinded key and subcredential for this identity during `cur_period`.
    pub fn compute_blinded_key(
        &self,
        cur_period: TimePeriod,
    ) -> Result<(HsBlindIdKey, HsBlindIdKeypair, crate::Subcredential), keymanip::BlindingError>
    {
        // TODO: as discussed above in `HsId::compute_blinded_key`, we might
        // someday want to implement nonempty values for this secret, if we
        // decide it would be good for something.
        let secret = b"";

        let public_key = HsIdKey(*self.0.public());

        // Note: This implementation is somewhat inefficient, as it recomputes
        // the PublicKey, and computes our blinding factor twice.  But we
        // only do this on an onion service once per time period: the
        // performance does not matter.
        let (blinded_public_key, subcredential) = public_key.compute_blinded_key(cur_period)?;

        let h = public_key.blinding_factor(secret, cur_period);

        let blinded_keypair = keymanip::blind_keypair(&self.0, h)?;

        Ok((blinded_public_key, blinded_keypair.into(), subcredential))
    }
}

define_pk_keypair! {
/// The "blinded" identity of a v3 onion service. (`KP_hs_blind_id`)
///
/// This key is derived via a one-way transformation from an
/// `HsIdKey` and the current time period.
///
/// It is used for two purposes: first, to compute an index into the HSDir
/// ring, and second, to sign a `DescSigningKey`.
///
/// Note: This is a separate type from [`HsBlindId`] because it is about 6x
/// larger.  It is an expanded form, used for doing actual cryptography.
pub struct HsBlindIdKey(ed25519::PublicKey) / HsBlindIdKeypair(ed25519::ExpandedKeypair);
}

define_bytes! {
/// A blinded onion service identity, represented in a compact format. (`KP_hs_blind_id`)
///
/// Note: This is a separate type from [`HsBlindIdKey`] because it is about
/// 6x smaller.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct HsBlindId([u8; 32]);
}
impl_debug_hex! { HsBlindId .0 }

impl HsBlindIdKey {
    /// Return a representation of this key as a [`HsBlindId`].
    ///
    /// ([`HsBlindId`] is much smaller, and easier to store.)
    pub fn id(&self) -> HsBlindId {
        HsBlindId(self.0.to_bytes().into())
    }
}
impl TryFrom<HsBlindId> for HsBlindIdKey {
    type Error = signature::Error;

    fn try_from(value: HsBlindId) -> Result<Self, Self::Error> {
        ed25519::PublicKey::from_bytes(value.0.as_ref()).map(HsBlindIdKey)
    }
}

impl From<&HsBlindIdKeypair> for HsBlindIdKey {
    fn from(value: &HsBlindIdKeypair) -> Self {
        HsBlindIdKey(*value.0.public())
    }
}

impl From<HsBlindIdKey> for HsBlindId {
    fn from(value: HsBlindIdKey) -> Self {
        value.id()
    }
}
impl From<ed25519::Ed25519Identity> for HsBlindId {
    fn from(value: ed25519::Ed25519Identity) -> Self {
        Self(CtByteArray::from(<[u8; 32]>::from(value)))
    }
}

impl Signer<ed25519::Signature> for HsBlindIdKeypair {
    fn try_sign(&self, msg: &[u8]) -> Result<ed25519::Signature, signature::Error> {
        Ok(self.0.sign(msg))
    }
}

impl Ed25519PublicKey for HsBlindIdKeypair {
    fn public_key(&self) -> &ed25519::PublicKey {
        self.0.public()
    }
}

define_pk_keypair! {
/// A key used to sign onion service descriptors. (`KP_desc_sign`)
///
/// It is authenticated with a [`HsBlindIdKey`] to prove that it belongs to
/// the right onion service, and is used in turn to sign the descriptor that
/// tells clients what they need to know about contacting an onion service.
///
/// Onion services create a new `DescSigningKey` every time the
/// `HsBlindIdKey` rotates, to prevent descriptors made in one time period
/// from being linkable to those made in another.
///
/// Note: we use a separate signing key here, rather than using the
/// `HsBlindIdKey` directly, so that the [`HsBlindIdKeypair`]
/// can be kept offline.
pub struct HsDescSigningKey(ed25519::PublicKey) / HsDescSigningKeypair(ed25519::Keypair);
}

define_pk_keypair! {
/// A key used to identify and authenticate an onion service at a single
/// introduction point. (`KP_hs_ipt_sid`)
///
/// This key is included in the onion service's descriptor; a different one is
/// used at each introduction point.  Introduction points don't know the
/// relation of this key to the onion service: they only recognize the same key
/// when they see it again.
pub struct HsIntroPtSessionIdKey(ed25519::PublicKey) / HsIntroPtSessionIdKeypair(ed25519::Keypair);
}

define_pk_keypair! {
/// A key used in the HsNtor handshake between the client and the onion service.
/// (`KP_hss_ntor`)
///
/// The onion service chooses a different one of these to use with each
/// introduction point, though it does not need to tell the introduction points
/// about these keys.
pub struct HsSvcNtorKey(curve25519::PublicKey) / HsSvcNtorSecretKey(curve25519::StaticSecret);
curve25519_pair as HsSvcNtorKeypair;
}

mod hs_client_intro_auth {
    #![allow(deprecated)]
    //! Key type wrappers for the deprecated `HsClientIntroKey`/`HsClientIntroKeypair` types.

    use tor_llcrypto::pk::ed25519;

    use crate::macros::define_pk_keypair;

    define_pk_keypair! {
    /// First type of client authorization key, used for the introduction protocol.
    /// (`KP_hsc_intro_auth`)
    ///
    /// This is used to sign a nonce included in an extension in the encrypted
    /// portion of an introduce cell.
    #[deprecated(note = "This key type is not used in the protocol implemented today.")]
    pub struct HsClientIntroAuthKey(ed25519::PublicKey) /
    #[deprecated(note = "This key type is not used in the protocol implemented today.")]
    HsClientIntroAuthKeypair(ed25519::Keypair);
    }
}

define_pk_keypair! {
/// Second type of client authorization key, used for onion descriptor
/// decryption. (`KP_hsc_desc_enc`)
///
/// Any client who knows the secret key corresponding to this key can decrypt
/// the inner layer of the onion service descriptor.
pub struct HsClientDescEncKey(curve25519::PublicKey) / HsClientDescEncSecretKey(curve25519::StaticSecret);
curve25519_pair as HsClientDescEncKeypair;
}

impl PartialEq for HsClientDescEncKey {
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
}

define_pk_keypair! {
/// Server key, used for diffie hellman during onion descriptor decryption.
/// (`KP_hss_desc_enc`)
///
/// This key is created for a single descriptor, and then thrown away.
pub struct HsSvcDescEncKey(curve25519::PublicKey) / HsSvcDescEncSecretKey(curve25519::StaticSecret);
}

impl From<&HsClientDescEncSecretKey> for HsClientDescEncKey {
    fn from(ks: &HsClientDescEncSecretKey) -> Self {
        Self(curve25519::PublicKey::from(&ks.0))
    }
}

impl From<&HsClientDescEncKeypair> for HsClientDescEncKey {
    fn from(ks: &HsClientDescEncKeypair) -> Self {
        Self(**ks.public())
    }
}

/// An ephemeral x25519 keypair, generated by an onion service
/// and used to for onion service encryption.
#[allow(clippy::exhaustive_structs)]
#[derive(Debug)]
pub struct HsSvcDescEncKeypair {
    /// The public part of the key.
    pub public: HsSvcDescEncKey,
    /// The secret part of the key.
    pub secret: HsSvcDescEncSecretKey,
}

#[cfg(test)]
mod test {
    // @@ begin test lint list maintained by maint/add_warning @@
    #![allow(clippy::bool_assert_comparison)]
    #![allow(clippy::clone_on_copy)]
    #![allow(clippy::dbg_macro)]
    #![allow(clippy::print_stderr)]
    #![allow(clippy::print_stdout)]
    #![allow(clippy::single_char_pattern)]
    #![allow(clippy::unwrap_used)]
    #![allow(clippy::unchecked_duration_subtraction)]
    #![allow(clippy::useless_vec)]
    #![allow(clippy::needless_pass_by_value)]
    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use hex_literal::hex;
    use itertools::izip;
    use safelog::Redactable;
    use signature::Verifier;
    use std::time::{Duration, SystemTime};
    use tor_basic_utils::test_rng::testing_rng;

    use super::*;

    #[test]
    fn hsid_strings() {
        use HsIdParseError as PE;

        // From C Tor src/test/test_hs_common.c test_build_address
        let hex = "d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a";
        let b32 = "25njqamcweflpvkl73j4szahhihoc4xt3ktcgjnpaingr5yhkenl5sid";

        let hsid: [u8; 32] = hex::decode(hex).unwrap().try_into().unwrap();
        let hsid = HsId::from(hsid);
        let onion = format!("{}.onion", b32);

        assert_eq!(onion.parse::<HsId>().unwrap(), hsid);
        assert_eq!(hsid.to_string(), onion);

        let weird_case: String = izip!(onion.chars(), [false, true].iter().cloned().cycle(),)
            .map(|(c, swap)| if swap { c.to_ascii_uppercase() } else { c })
            .collect();
        dbg!(&weird_case);
        assert_eq!(weird_case.parse::<HsId>().unwrap(), hsid);

        macro_rules! chk_err { { $s:expr, $($pat:tt)* } => {
            let e = $s.parse::<HsId>();
            assert!(matches!(e, Err($($pat)*)), "{:?}", &e);
        } }
        let edited = |i, c| {
            let mut s = b32.to_owned().into_bytes();
            s[i] = c;
            format!("{}.onion", String::from_utf8(s).unwrap())
        };

        chk_err!("wrong", PE::NotOnionDomain);
        chk_err!("@.onion", PE::InvalidBase32(..));
        chk_err!("aaaaaaaa.onion", PE::InvalidData(..));
        chk_err!(edited(55, b'E'), PE::UnsupportedVersion(4));
        chk_err!(edited(53, b'X'), PE::WrongChecksum);
        chk_err!(&format!("www.{}", &onion), PE::HsIdContainsSubdomain);

        assert_eq!(format!("{:x}", &hsid), format!("HsId(0x{})", hex));
        assert_eq!(format!("{:?}", &hsid), format!("HsId({})", onion));

        assert_eq!(format!("{}", hsid.redacted()), "???sid.onion");
    }

    #[test]
    fn key_blinding_blackbox() {
        let mut rng = testing_rng();
        let offset = Duration::new(12 * 60 * 60, 0);
        let when = TimePeriod::new(Duration::from_secs(3600), SystemTime::now(), offset).unwrap();
        let keypair = ed25519::Keypair::generate(&mut rng);
        let id_pub = HsIdKey::from(keypair.verifying_key());
        let id_keypair = HsIdKeypair::from(ed25519::ExpandedKeypair::from(&keypair));

        let (blinded_pub, subcred1) = id_pub.compute_blinded_key(when).unwrap();
        let (blinded_pub2, blinded_keypair, subcred2) =
            id_keypair.compute_blinded_key(when).unwrap();

        assert_eq!(subcred1.as_ref(), subcred2.as_ref());
        assert_eq!(blinded_pub.0.to_bytes(), blinded_pub2.0.to_bytes());
        assert_eq!(blinded_pub.id(), blinded_pub2.id());

        let message = b"Here is a terribly important string to authenticate.";
        let other_message = b"Hey, that is not what I signed!";
        let sign = blinded_keypair.sign(message);

        assert!(blinded_pub.as_ref().verify(message, &sign).is_ok());
        assert!(blinded_pub.as_ref().verify(other_message, &sign).is_err());
    }

    #[test]
    fn key_blinding_testvec() {
        // Test vectors generated with C tor.
        let id = HsId::from(hex!(
            "833990B085C1A688C1D4C8B1F6B56AFAF5A2ECA674449E1D704F83765CCB7BC6"
        ));
        let id_pubkey = HsIdKey::try_from(id).unwrap();
        let id_seckey = HsIdKeypair::from(
            ed25519::ExpandedKeypair::from_secret_key_bytes(hex!(
                "D8C7FF0E31295B66540D789AF3E3DF992038A9592EEA01D8B7CBA06D6E66D159
                 4D6167696320576F7264733A20737065697373636F62616C742062697669756D"
            ))
            .unwrap(),
        );
        let time_period = TimePeriod::new(
            humantime::parse_duration("1 day").unwrap(),
            humantime::parse_rfc3339("1973-05-20T01:50:33Z").unwrap(),
            humantime::parse_duration("12 hours").unwrap(),
        )
        .unwrap();
        assert_eq!(time_period.interval_num, 1234);

        let h = id_pubkey.blinding_factor(b"", time_period);
        assert_eq!(
            h,
            hex!("379E50DB31FEE6775ABD0AF6FB7C371E060308F4F847DB09FE4CFE13AF602287")
        );

        let (blinded_pub1, subcred1) = id_pubkey.compute_blinded_key(time_period).unwrap();
        assert_eq!(
            blinded_pub1.0.to_bytes(),
            hex!("3A50BF210E8F9EE955AE0014F7A6917FB65EBF098A86305ABB508D1A7291B6D5")
        );
        assert_eq!(
            subcred1.as_ref(),
            &hex!("635D55907816E8D76398A675A50B1C2F3E36B42A5CA77BA3A0441285161AE07D")
        );

        let (blinded_pub2, blinded_sec, subcred2) =
            id_seckey.compute_blinded_key(time_period).unwrap();
        assert_eq!(blinded_pub1.0.to_bytes(), blinded_pub2.0.to_bytes());
        assert_eq!(subcred1.as_ref(), subcred2.as_ref());
        assert_eq!(
            blinded_sec.0.to_secret_key_bytes(),
            hex!(
                "A958DC83AC885F6814C67035DE817A2C604D5D2F715282079448F789B656350B
                 4540FE1F80AA3F7E91306B7BF7A8E367293352B14A29FDCC8C19F3558075524B"
            )
        );
    }
}