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
// Bitcoin secp256k1 bindings
// Written in 2014 by
//   Dawid Ciężarkiewicz
//   Andrew Poelstra
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! # Recovery module
//! Provides a signing function that allows recovering the public key from the
//! signature.

use core::ptr;
use key;
use super::{Secp256k1, Message, Error, Signature, Verification, Signing};
use super::ffi as super_ffi;
pub use key::SecretKey;
pub use key::PublicKey;
use self::super_ffi::CPtr;

use ffi::recovery as ffi;

/// A tag used for recovering the public key from a compact signature
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct RecoveryId(i32);

/// An ECDSA signature with a recovery ID for pubkey recovery
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct RecoverableSignature(ffi::RecoverableSignature);

impl RecoveryId {
#[inline]
/// Allows library users to create valid recovery IDs from i32.
pub fn from_i32(id: i32) -> Result<RecoveryId, Error> {
    match id {
        0 | 1 | 2 | 3 => Ok(RecoveryId(id)),
        _ => Err(Error::InvalidRecoveryId)
    }
}

#[inline]
/// Allows library users to convert recovery IDs to i32.
pub fn to_i32(self) -> i32 {
    self.0
}
}

impl RecoverableSignature {
    #[inline]
    /// Converts a compact-encoded byte slice to a signature. This
    /// representation is nonstandard and defined by the libsecp256k1
    /// library.
    pub fn from_compact(data: &[u8], recid: RecoveryId) -> Result<RecoverableSignature, Error> {
        if data.is_empty() {return Err(Error::InvalidSignature);}

        let mut ret = ffi::RecoverableSignature::new();

        unsafe {
            if data.len() != 64 {
                Err(Error::InvalidSignature)
            } else if ffi::secp256k1_ecdsa_recoverable_signature_parse_compact(
                super_ffi::secp256k1_context_no_precomp,
                &mut ret,
                data.as_c_ptr(),
                recid.0,
            ) == 1
            {
                Ok(RecoverableSignature(ret))
            } else {
                Err(Error::InvalidSignature)
            }
        }
    }

    /// Obtains a raw pointer suitable for use with FFI functions
    #[inline]
    pub fn as_ptr(&self) -> *const ffi::RecoverableSignature {
        &self.0
    }

    /// Obtains a raw mutable pointer suitable for use with FFI functions
    #[inline]
    pub fn as_mut_ptr(&mut self) -> *mut ffi::RecoverableSignature {
        &mut self.0
    }

    #[inline]
    /// Serializes the recoverable signature in compact format
    pub fn serialize_compact(&self) -> (RecoveryId, [u8; 64]) {
        let mut ret = [0u8; 64];
        let mut recid = 0i32;
        unsafe {
            let err = ffi::secp256k1_ecdsa_recoverable_signature_serialize_compact(
                super_ffi::secp256k1_context_no_precomp,
                ret.as_mut_c_ptr(),
                &mut recid,
                self.as_c_ptr(),
            );
            assert!(err == 1);
        }
        (RecoveryId(recid), ret)
    }

    /// Converts a recoverable signature to a non-recoverable one (this is needed
    /// for verification
    #[inline]
    pub fn to_standard(&self) -> Signature {
        unsafe {
            let mut ret = super_ffi::Signature::new();
            let err = ffi::secp256k1_ecdsa_recoverable_signature_convert(
                super_ffi::secp256k1_context_no_precomp,
                &mut ret,
                self.as_c_ptr(),
            );
            assert!(err == 1);
            Signature(ret)
        }
    }
}


impl CPtr for RecoverableSignature {
    type Target = ffi::RecoverableSignature;
    fn as_c_ptr(&self) -> *const Self::Target {
        self.as_ptr()
    }

    fn as_mut_c_ptr(&mut self) -> *mut Self::Target {
        self.as_mut_ptr()
    }
}

/// Creates a new recoverable signature from a FFI one
impl From<ffi::RecoverableSignature> for RecoverableSignature {
    #[inline]
    fn from(sig: ffi::RecoverableSignature) -> RecoverableSignature {
        RecoverableSignature(sig)
    }
}

impl<C: Signing> Secp256k1<C> {
    /// Constructs a signature for `msg` using the secret key `sk` and RFC6979 nonce
    /// Requires a signing-capable context.
    pub fn sign_recoverable(&self, msg: &Message, sk: &key::SecretKey)
                            -> RecoverableSignature {

        let mut ret = ffi::RecoverableSignature::new();
        unsafe {
            // We can assume the return value because it's not possible to construct
            // an invalid signature from a valid `Message` and `SecretKey`
            assert_eq!(
                ffi::secp256k1_ecdsa_sign_recoverable(
                    self.ctx,
                    &mut ret,
                    msg.as_c_ptr(),
                    sk.as_c_ptr(),
                    super_ffi::secp256k1_nonce_function_rfc6979,
                    ptr::null()
                ),
                1
            );
        }

        RecoverableSignature::from(ret)
    }
}

impl<C: Verification> Secp256k1<C> {
    /// Determines the public key for which `sig` is a valid signature for
    /// `msg`. Requires a verify-capable context.
    pub fn recover(&self, msg: &Message, sig: &RecoverableSignature)
                   -> Result<key::PublicKey, Error> {

        unsafe {
            let mut pk = super_ffi::PublicKey::new();
            if ffi::secp256k1_ecdsa_recover(self.ctx, &mut pk,
                                            sig.as_c_ptr(), msg.as_c_ptr()) != 1 {
                return Err(Error::InvalidSignature);
            }
            Ok(key::PublicKey::from(pk))
        }
    }
}


#[cfg(test)]
mod tests {
    use rand::{RngCore, thread_rng};

    use key::SecretKey;
    use super::{RecoveryId, RecoverableSignature};
    use super::super::{Secp256k1, Message};
    use super::super::Error::{IncorrectSignature, InvalidSignature};

    #[cfg(target_arch = "wasm32")]
    use wasm_bindgen_test::wasm_bindgen_test as test;

    #[test]
    fn capabilities() {
        let sign = Secp256k1::signing_only();
        let vrfy = Secp256k1::verification_only();
        let full = Secp256k1::new();

        let mut msg = [0u8; 32];
        thread_rng().fill_bytes(&mut msg);
        let msg = Message::from_slice(&msg).unwrap();

        // Try key generation
        let (sk, pk) = full.generate_keypair(&mut thread_rng());

        // Try signing
        assert_eq!(sign.sign_recoverable(&msg, &sk), full.sign_recoverable(&msg, &sk));
        let sigr = full.sign_recoverable(&msg, &sk);

        // Try pk recovery
        assert!(vrfy.recover(&msg, &sigr).is_ok());
        assert!(full.recover(&msg, &sigr).is_ok());

        assert_eq!(vrfy.recover(&msg, &sigr),
                   full.recover(&msg, &sigr));
        assert_eq!(full.recover(&msg, &sigr), Ok(pk));
    }

    #[test]
    fn recid_sanity_check() {
        let one = RecoveryId(1);
        assert_eq!(one, one.clone());
    }

    #[test]
    #[cfg(not(fuzzing))]  // fixed sig vectors can't work with fuzz-sigs
    fn sign() {
        let mut s = Secp256k1::new();
        s.randomize(&mut thread_rng());
        let one = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1];

        let sk = SecretKey::from_slice(&one).unwrap();
        let msg = Message::from_slice(&one).unwrap();

        let sig = s.sign_recoverable(&msg, &sk);
        assert_eq!(Ok(sig), RecoverableSignature::from_compact(&[
            0x66, 0x73, 0xff, 0xad, 0x21, 0x47, 0x74, 0x1f,
            0x04, 0x77, 0x2b, 0x6f, 0x92, 0x1f, 0x0b, 0xa6,
            0xaf, 0x0c, 0x1e, 0x77, 0xfc, 0x43, 0x9e, 0x65,
            0xc3, 0x6d, 0xed, 0xf4, 0x09, 0x2e, 0x88, 0x98,
            0x4c, 0x1a, 0x97, 0x16, 0x52, 0xe0, 0xad, 0xa8,
            0x80, 0x12, 0x0e, 0xf8, 0x02, 0x5e, 0x70, 0x9f,
            0xff, 0x20, 0x80, 0xc4, 0xa3, 0x9a, 0xae, 0x06,
            0x8d, 0x12, 0xee, 0xd0, 0x09, 0xb6, 0x8c, 0x89],
            RecoveryId(1)))
    }

    #[test]
    fn sign_and_verify_fail() {
        let mut s = Secp256k1::new();
        s.randomize(&mut thread_rng());

        let mut msg = [0u8; 32];
        thread_rng().fill_bytes(&mut msg);
        let msg = Message::from_slice(&msg).unwrap();

        let (sk, pk) = s.generate_keypair(&mut thread_rng());

        let sigr = s.sign_recoverable(&msg, &sk);
        let sig = sigr.to_standard();

        let mut msg = [0u8; 32];
        thread_rng().fill_bytes(&mut msg);
        let msg = Message::from_slice(&msg).unwrap();
        assert_eq!(s.verify(&msg, &sig, &pk), Err(IncorrectSignature));

        let recovered_key = s.recover(&msg, &sigr).unwrap();
        assert!(recovered_key != pk);
    }

    #[test]
    fn sign_with_recovery() {
        let mut s = Secp256k1::new();
        s.randomize(&mut thread_rng());

        let mut msg = [0u8; 32];
        thread_rng().fill_bytes(&mut msg);
        let msg = Message::from_slice(&msg).unwrap();

        let (sk, pk) = s.generate_keypair(&mut thread_rng());

        let sig = s.sign_recoverable(&msg, &sk);

        assert_eq!(s.recover(&msg, &sig), Ok(pk));
    }

    #[test]
    fn bad_recovery() {
        let mut s = Secp256k1::new();
        s.randomize(&mut thread_rng());

        let msg = Message::from_slice(&[0x55; 32]).unwrap();

        // Zero is not a valid sig
        let sig = RecoverableSignature::from_compact(&[0; 64], RecoveryId(0)).unwrap();
        assert_eq!(s.recover(&msg, &sig), Err(InvalidSignature));
        // ...but 111..111 is
        let sig = RecoverableSignature::from_compact(&[1; 64], RecoveryId(0)).unwrap();
        assert!(s.recover(&msg, &sig).is_ok());
    }

    #[test]
    fn test_debug_output() {
        let sig = RecoverableSignature::from_compact(&[
            0x66, 0x73, 0xff, 0xad, 0x21, 0x47, 0x74, 0x1f,
            0x04, 0x77, 0x2b, 0x6f, 0x92, 0x1f, 0x0b, 0xa6,
            0xaf, 0x0c, 0x1e, 0x77, 0xfc, 0x43, 0x9e, 0x65,
            0xc3, 0x6d, 0xed, 0xf4, 0x09, 0x2e, 0x88, 0x98,
            0x4c, 0x1a, 0x97, 0x16, 0x52, 0xe0, 0xad, 0xa8,
            0x80, 0x12, 0x0e, 0xf8, 0x02, 0x5e, 0x70, 0x9f,
            0xff, 0x20, 0x80, 0xc4, 0xa3, 0x9a, 0xae, 0x06,
            0x8d, 0x12, 0xee, 0xd0, 0x09, 0xb6, 0x8c, 0x89],
            RecoveryId(1)).unwrap();
        assert_eq!(&format!("{:?}", sig), "RecoverableSignature(98882e09f4ed6dc3659e43fc771e0cafa60b1f926f2b77041f744721adff7366898cb609d0ee128d06ae9aa3c48020ff9f705e02f80e1280a8ade05216971a4c01)");
    }

    #[test]
    fn test_recov_sig_serialize_compact() {
        let recid_in = RecoveryId(1);
        let bytes_in = &[
            0x66, 0x73, 0xff, 0xad, 0x21, 0x47, 0x74, 0x1f,
            0x04, 0x77, 0x2b, 0x6f, 0x92, 0x1f, 0x0b, 0xa6,
            0xaf, 0x0c, 0x1e, 0x77, 0xfc, 0x43, 0x9e, 0x65,
            0xc3, 0x6d, 0xed, 0xf4, 0x09, 0x2e, 0x88, 0x98,
            0x4c, 0x1a, 0x97, 0x16, 0x52, 0xe0, 0xad, 0xa8,
            0x80, 0x12, 0x0e, 0xf8, 0x02, 0x5e, 0x70, 0x9f,
            0xff, 0x20, 0x80, 0xc4, 0xa3, 0x9a, 0xae, 0x06,
            0x8d, 0x12, 0xee, 0xd0, 0x09, 0xb6, 0x8c, 0x89];
        let sig = RecoverableSignature::from_compact(
            bytes_in,
            recid_in,
        ).unwrap();
        let (recid_out, bytes_out) = sig.serialize_compact();
        assert_eq!(recid_in, recid_out);
        assert_eq!(&bytes_in[..], &bytes_out[..]);
    }

    #[test]
    fn test_recov_id_conversion_between_i32() {
        assert!(RecoveryId::from_i32(-1).is_err());
        assert!(RecoveryId::from_i32(0).is_ok());
        assert!(RecoveryId::from_i32(1).is_ok());
        assert!(RecoveryId::from_i32(2).is_ok());
        assert!(RecoveryId::from_i32(3).is_ok());
        assert!(RecoveryId::from_i32(4).is_err());
        let id0 = RecoveryId::from_i32(0).unwrap();
        assert_eq!(id0.to_i32(), 0);
        let id1 = RecoveryId(1);
        assert_eq!(id1.to_i32(), 1);
    }
}


#[cfg(all(test, feature = "unstable"))]
mod benches {
    use rand::{thread_rng, RngCore};
    use test::{Bencher, black_box};
    use super::{Message, Secp256k1};

    #[bench]
    pub fn bench_recover(bh: &mut Bencher) {
        let s = Secp256k1::new();
        let mut msg = [0u8; 32];
        thread_rng().fill_bytes(&mut msg);
        let msg = Message::from_slice(&msg).unwrap();
        let (sk, _) = s.generate_keypair(&mut thread_rng());
        let sig = s.sign_recoverable(&msg, &sk);

        bh.iter(|| {
            let res = s.recover(&msg, &sig).unwrap();
            black_box(res);
        });
    }
}