Module: Bitcoin::OpenSSL_EC

Extended by:
FFI::Library
Defined in:
lib/bitcoin/ffi/openssl.rb

Constant Summary collapse

NID_secp256k1 = 
714
POINT_CONVERSION_COMPRESSED = 
2
POINT_CONVERSION_UNCOMPRESSED = 
4

Class Method Summary collapse

Class Method Details

.BN_num_bytes(ptr) ⇒ Object 



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# File 'lib/bitcoin/ffi/openssl.rb', line 65

def self.BN_num_bytes(ptr); (BN_num_bits(ptr) + 7) / 8; end

.der_to_private_key(der_hex) ⇒ Object

extract private key from uncompressed DER format



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# File 'lib/bitcoin/ffi/openssl.rb', line 125

def self.der_to_private_key(der_hex)
  init_ffi_ssl
  #k  = EC_KEY_new_by_curve_name(NID_secp256k1)
  #kp = FFI::MemoryPointer.new(:pointer).put_pointer(0, eckey)

  buf = FFI::MemoryPointer.from_string([der_hex].pack("H*"))
  ptr = FFI::MemoryPointer.new(:pointer).put_pointer(0, buf)

  #ec_key = d2i_ECPrivateKey(kp, ptr, buf.size-1)
  ec_key = d2i_ECPrivateKey(nil, ptr, buf.size-1)
  return nil if ec_key.null?
  bn = EC_KEY_get0_private_key(ec_key)
  BN_bn2bin(bn, buf)
  buf.read_string(32).unpack("H*")[0]
end

.init_ffi_ssl ⇒ Object 



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# File 'lib/bitcoin/ffi/openssl.rb', line 282

def self.init_ffi_ssl
  return if @ssl_loaded
  SSL_library_init()
  ERR_load_crypto_strings()
  SSL_load_error_strings()
  RAND_poll()
  @ssl_loaded = true
end

.recover_compact(hash, signature) ⇒ Object 



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# File 'lib/bitcoin/ffi/openssl.rb', line 270

def self.recover_compact(hash, signature)
  return false if signature.bytesize != 65
  #i = signature.unpack("C")[0] - 27
  #pubkey = recover_public_key_from_signature(hash, signature, (i & ~4), i >= 4)

  version = signature.unpack('C')[0]
  return false if version < 27 or version > 34

  compressed = (version >= 31) ? (version -= 4; true) : false
  pubkey = recover_public_key_from_signature(hash, signature, version-27, compressed)
end

.recover_public_key_from_signature(message_hash, signature, rec_id, is_compressed) ⇒ Object

Given the components of a signature and a selector value, recover and return the public key that generated the signature according to the algorithm in SEC1v2 section 4.1.6.

rec_id is an index from 0 to 3 that indicates which of the 4 possible keys is the correct one. Because the key recovery operation yields multiple potential keys, the correct key must either be stored alongside the signature, or you must be willing to try each rec_id in turn until you find one that outputs the key you are expecting.

If this method returns nil, it means recovery was not possible and rec_id should be iterated.

Given the above two points, a correct usage of this method is inside a for loop from 0 to 3, and if the output is nil OR a key that is not the one you expect, you try again with the next rec_id.

message_hash = hash of the signed message.
signature = the R and S components of the signature, wrapped.
rec_id = which possible key to recover.
is_compressed = whether or not the original pubkey was compressed.



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# File 'lib/bitcoin/ffi/openssl.rb', line 162

def self.recover_public_key_from_signature(message_hash, signature, rec_id, is_compressed)
  return nil if rec_id < 0 or signature.bytesize != 65
  init_ffi_ssl

  signature = FFI::MemoryPointer.from_string(signature)
  #signature_bn = BN_bin2bn(signature, 65, BN_new())
  r = BN_bin2bn(signature[1], 32, BN_new())
  s = BN_bin2bn(signature[33], 32, BN_new())

  n, i = 0, rec_id / 2
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)

  EC_KEY_set_conv_form(eckey, POINT_CONVERSION_COMPRESSED) if is_compressed

  group = EC_KEY_get0_group(eckey)
  order = BN_new()
  EC_GROUP_get_order(group, order, nil)
  x = BN_dup(order)
  BN_mul_word(x, i)
  BN_add(x, x, r)

  field = BN_new()
  EC_GROUP_get_curve_GFp(group, field, nil, nil, nil)

  if BN_cmp(x, field) >= 0
    [r, s, order, x, field].each{|i| BN_free(i) }
    EC_KEY_free(eckey)
    return nil
  end

  big_r = EC_POINT_new(group)
  EC_POINT_set_compressed_coordinates_GFp(group, big_r, x, rec_id % 2, nil)

  big_q = EC_POINT_new(group)
  n = EC_GROUP_get_degree(group)
  e = BN_bin2bn(message_hash, message_hash.bytesize, BN_new())
  BN_rshift(e, e, 8 - (n & 7)) if 8 * message_hash.bytesize > n

  ctx = BN_CTX_new()
  zero, rr, sor, eor = BN_new(), BN_new(), BN_new(), BN_new()
  BN_set_word(zero, 0)
  BN_mod_sub(e, zero, e, order, ctx)
  BN_mod_inverse(rr, r, order, ctx)
  BN_mod_mul(sor, s, rr, order, ctx)
  BN_mod_mul(eor, e, rr, order, ctx)
  EC_POINT_mul(group, big_q, eor, big_r, sor, ctx)
  EC_KEY_set_public_key(eckey, big_q)
  BN_CTX_free(ctx)

  [r, s, order, x, field, e, zero, rr, sor, eor].each{|i| BN_free(i) }
  [big_r, big_q].each{|i| EC_POINT_free(i) }

  length = i2o_ECPublicKey(eckey, nil)
  buf = FFI::MemoryPointer.new(:uint8, length)
  ptr = FFI::MemoryPointer.new(:pointer).put_pointer(0, buf)
  pub_hex = if i2o_ECPublicKey(eckey, ptr) == length
    buf.read_string(length).unpack("H*")[0]
  end

  EC_KEY_free(eckey)

  pub_hex
end

.regenerate_key(private_key) ⇒ Object

resolve public from private key, using ffi and libssl.so example:

keypair = Bitcoin.generate_key; Bitcoin::OpenSSL_EC.regenerate_key(keypair.first) == keypair



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# File 'lib/bitcoin/ffi/openssl.rb', line 71

def self.regenerate_key(private_key)
  private_key = [private_key].pack("H*") if private_key.bytesize >= (32*2)
  private_key_hex = private_key.unpack("H*")[0]

  #private_key = FFI::MemoryPointer.new(:uint8, private_key.bytesize)
  #                .put_bytes(0, private_key, 0, private_key.bytesize)
  private_key = FFI::MemoryPointer.from_string(private_key)

  init_ffi_ssl
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  #priv_key = BN_bin2bn(private_key, private_key.size, BN_new())
  priv_key = BN_bin2bn(private_key, private_key.size-1, BN_new())

  group, order, ctx = EC_KEY_get0_group(eckey), BN_new(), BN_CTX_new()
  EC_GROUP_get_order(group, order, ctx)

  pub_key = EC_POINT_new(group)
  EC_POINT_mul(group, pub_key, priv_key, nil, nil, ctx)
  EC_KEY_set_private_key(eckey, priv_key)
  EC_KEY_set_public_key(eckey, pub_key)

  BN_free(order)
  BN_CTX_free(ctx)
  EC_POINT_free(pub_key)
  BN_free(priv_key)


  length = i2d_ECPrivateKey(eckey, nil)
  buf = FFI::MemoryPointer.new(:uint8, length)
  ptr = FFI::MemoryPointer.new(:pointer).put_pointer(0, buf)
  priv_hex = if i2d_ECPrivateKey(eckey, ptr) == length
    size = buf.get_array_of_uint8(8, 1)[0]
    buf.get_array_of_uint8(9, size).pack("C*").rjust(32, "\x00").unpack("H*")[0]
    #der_to_private_key( ptr.read_pointer.read_string(length).unpack("H*")[0] )
  end

  if priv_hex != private_key_hex
    raise "regenerated wrong private_key, raise here before generating a faulty public_key too!"
  end


  length = i2o_ECPublicKey(eckey, nil)
  buf = FFI::MemoryPointer.new(:uint8, length)
  ptr = FFI::MemoryPointer.new(:pointer).put_pointer(0, buf)
  pub_hex = if i2o_ECPublicKey(eckey, ptr) == length
    buf.read_string(length).unpack("H*")[0]
  end

  EC_KEY_free(eckey)

  [ priv_hex, pub_hex ]
end

.sign_compact(hash, private_key, public_key_hex = nil, pubkey_compressed = nil) ⇒ Object 



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# File 'lib/bitcoin/ffi/openssl.rb', line 226

def self.sign_compact(hash, private_key, public_key_hex = nil, pubkey_compressed = nil)
  private_key = [private_key].pack("H*") if private_key.bytesize >= 64
  private_key_hex = private_key.unpack("H*")[0]

  public_key_hex = regenerate_key(private_key_hex).last unless public_key_hex
  pubkey_compressed = (public_key_hex[0..1] == "04" ? false : true) unless pubkey_compressed

  init_ffi_ssl
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  priv_key = BN_bin2bn(private_key, private_key.bytesize, BN_new())

  group, order, ctx = EC_KEY_get0_group(eckey), BN_new(), BN_CTX_new()
  EC_GROUP_get_order(group, order, ctx)

  pub_key = EC_POINT_new(group)
  EC_POINT_mul(group, pub_key, priv_key, nil, nil, ctx)
  EC_KEY_set_private_key(eckey, priv_key)
  EC_KEY_set_public_key(eckey, pub_key)

  signature = ECDSA_do_sign(hash, hash.bytesize, eckey)

  BN_free(order)
  BN_CTX_free(ctx)
  EC_POINT_free(pub_key)
  BN_free(priv_key)
  EC_KEY_free(eckey)

  buf, rec_id, head = FFI::MemoryPointer.new(:uint8, 32), nil, nil
  r, s = signature.get_array_of_pointer(0, 2).map{|i| BN_bn2bin(i, buf); buf.read_string(BN_num_bytes(i)).rjust(32, "\x00") }

  if signature.get_array_of_pointer(0, 2).all?{|i| BN_num_bits(i) <= 256 }
    4.times{|i|
      head = [ 27 + i + (pubkey_compressed ? 4 : 0) ].pack("C")
      if public_key_hex == recover_public_key_from_signature(hash, [head, r, s].join, i, pubkey_compressed)
        rec_id = i; break
      end
    }
  end

  ECDSA_SIG_free(signature)

  [ head, [r,s] ].join if rec_id
end