torsign.py (2787B)
1 import argparse 2 import base64 3 import hashlib 4 5 # All the code come from onionbalance codebase 6 # https://gitlab.torproject.org/tpo/core/onionbalance/-/blob/main/onionbalance/hs_v3/ext/slow_ed25519.py 7 8 9 def load_tor_key_from_disk(key_bytes): 10 if key_bytes[:29] != b'== ed25519v1-secret: type0 ==': 11 raise "Tor key does not start with Tor header" 12 expanded_sk = key_bytes[32:] 13 if len(expanded_sk) != 64: 14 raise "Tor private key has the wrong length" 15 return expanded_sk 16 17 18 def sign(priv_key, msg): 19 return signatureWithESK(msg, priv_key, publickeyFromESK(priv_key)) 20 21 22 def publickeyFromESK(h): 23 a = decodeint(h[:32]) 24 A = scalarmult(B,a) 25 return encodepoint(A) 26 27 28 def signatureWithESK(m,h,pk): 29 a = decodeint(h[:32]) 30 tohint = b''.join([bytes([h[i]]) for i in range(b//8,b//4)]) + m 31 r = Hint(tohint) 32 R = scalarmult(B,r) 33 S = (r + Hint(encodepoint(R) + pk + m) * a) % l 34 return encodepoint(R) + encodeint(S) 35 36 37 def scalarmult(P,e): 38 if e == 0: return [0,1] 39 Q = scalarmult(P,e//2) 40 Q = edwards(Q,Q) 41 if e & 1: Q = edwards(Q,P) 42 return Q 43 44 45 def inv(x): 46 return expmod(x,q-2,q) 47 48 49 def expmod(b,e,m): 50 if e == 0: return 1 51 t = expmod(b,e//2,m)**2 % m 52 if e & 1: t = (t*b) % m 53 return t 54 55 56 q = 2**255 - 19 57 d = -121665 * inv(121666) 58 I = expmod(2,(q-1)//4,q) 59 60 61 def xrecover(y): 62 xx = (y*y-1) * inv(d*y*y+1) 63 x = expmod(xx,(q+3)//8,q) 64 if (x*x - xx) % q != 0: x = (x*I) % q 65 if x % 2 != 0: x = q-x 66 return x 67 68 69 b = 256 70 l = 2**252 + 27742317777372353535851937790883648493 71 By = 4 * inv(5) 72 Bx = xrecover(By) 73 B = [Bx % q,By % q] 74 75 def edwards(P,Q): 76 x1 = P[0] 77 y1 = P[1] 78 x2 = Q[0] 79 y2 = Q[1] 80 x3 = (x1*y2+x2*y1) * inv(1+d*x1*x2*y1*y2) 81 y3 = (y1*y2+x1*x2) * inv(1-d*x1*x2*y1*y2) 82 return [x3 % q,y3 % q] 83 84 85 def H(m): 86 return hashlib.sha512(m).digest() 87 88 89 def bit(h,i): 90 return (h[i//8] >> (i%8)) & 1 91 92 93 def Hint(m): 94 h = H(m) 95 return sum(2**i * bit(h,i) for i in range(2*b)) 96 97 98 def encodepoint(P): 99 x = P[0] 100 y = P[1] 101 bits = [(y >> i) & 1 for i in range(b - 1)] + [x & 1] 102 return b''.join([bytes([sum([bits[i * 8 + j] << j for j in range(8)])]) for i in range(b//8)]) 103 104 105 def encodeint(y): 106 bits = [(y >> i) & 1 for i in range(b)] 107 return b''.join([bytes([sum([bits[i * 8 + j] << j for j in range(8)])]) for i in range(b//8)]) 108 109 110 def decodeint(s): 111 return sum(2**i * bit(s,i) for i in range(0,b)) 112 113 114 parser = argparse.ArgumentParser() 115 parser.add_argument('cert') 116 parser.add_argument('-s', '--secret', default="hs_ed25519_secret_key") 117 args = parser.parse_args() 118 119 msg = open(args.cert, 'rb').read() 120 pem_key_bytes = open(args.secret, 'rb').read() 121 privkey = load_tor_key_from_disk(pem_key_bytes) 122 msg_sig = sign(privkey, msg) 123 print(base64.b64encode(msg_sig).decode())