1
package pow
2
 
3
import (
4
	"crypto/ed25519"
5
	"fmt"
6
	"time"
7
 
8
	"go.miragespace.co/specter/spec/protocol"
9
	"go.miragespace.co/specter/util/hashcash"
10
 
11
	"github.com/twitchtv/twirp"
12
)
13
 
14
type Parameters struct {
15
	GetSubject func(pubKey ed25519.PublicKey) string
16
	Expires    time.Duration
17
	Difficulty int
18
}
19
 
20
type Decoded struct {
21
	PubKey  ed25519.PublicKey
22
	Subject string
23
}
24
 
25
func VerifySolution(req *protocol.ProofOfWork, p Parameters) (*Decoded, error) {
26
	if len(req.GetPubKey()) != ed25519.PublicKeySize {
27
		return nil, twirp.InvalidArgumentError("pub_key", "public key length is not ed25519")
28
	}
29
 
30
	if len(req.GetSignature()) != ed25519.SignatureSize {
31
		return nil, twirp.InvalidArgumentError("signature", "signature length is not ed25519")
32
	}
33
 
34
	if len(req.GetSolution()) == 0 {
35
		return nil, twirp.RequiredArgumentError("solution")
36
	}
37
 
38
	pubKey := ed25519.PublicKey(req.GetPubKey())
39
 
40
	if !ed25519.Verify(pubKey, []byte(req.GetSolution()), req.GetSignature()) {
41
		return nil, twirp.InvalidArgumentError("signature", "not a valid signature of solution by pub_key")
42
	}
43
 
44
	hc, err := hashcash.Parse(req.GetSolution())
45
	if err != nil {
46
		return nil, twirp.InvalidArgumentError("solution", err.Error())
47
	}
48
 
49
	if hc.Difficulty != p.Difficulty {
50
		return nil, twirp.InvalidArgumentError("solution", "solution the wrong difficulty")
51
	}
52
 
53
	if hc.ExpiresAt.IsZero() {
54
		return nil, twirp.InvalidArgumentError("solution", "solution cannot have zero-value expiresAt")
55
	}
56
 
57
	if time.Since(hc.ExpiresAt).Abs() > p.Expires*2 {
58
		return nil, twirp.InvalidArgumentError("solution", "solution expires too far away from now")
59
	}
60
 
61
	subject := p.GetSubject(pubKey)
62
	if err := hc.Verify(subject); err != nil {
63
		return nil, twirp.InvalidArgumentError("solution", err.Error())
64
	}
65
 
66
	return &Decoded{
67
		PubKey:  pubKey,
68
		Subject: subject,
69
	}, nil
70
}
71
 
72
func GenerateSolution(privKey ed25519.PrivateKey, p Parameters) (*protocol.ProofOfWork, error) {
73
	if len(privKey) != ed25519.PrivateKeySize {
74
		return nil, fmt.Errorf("private key length is not ed25519")
75
	}
76
 
77
	var (
78
		pubKey  = privKey.Public().(ed25519.PublicKey)
79
		subject = p.GetSubject(pubKey)
80
	)
81
 
82
	hc := hashcash.New(hashcash.Hashcash{
83
		Subject:    subject,
84
		Difficulty: p.Difficulty,
85
		ExpiresAt:  time.Now().Add(p.Expires),
86
	})
87
 
88
	if err := hc.Solve(p.Difficulty); err != nil {
89
		return nil, err
90
	}
91
 
92
	sig := ed25519.Sign(privKey, []byte(hc.String()))
93
	return &protocol.ProofOfWork{
94
		PubKey:    pubKey,
95
		Signature: sig,
96
		Solution:  hc.String(),
97
	}, nil
98
}