Module: Bitcoin::OpenSSL_EC

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

Overview

autoload when you need to re-generate a public_key from only its private_key. ported from: github.com/sipa/bitcoin/blob/2d40fe4da9ea82af4b652b691a4185431d6e47a8/key.h

Constant Summary collapse

NID_secp256k1 =

rubocop:disable Naming/ConstantName

714
POINT_CONVERSION_COMPRESSED = 
2
POINT_CONVERSION_UNCOMPRESSED = 
4

Class Method Summary collapse

Class Method Details

.BN_num_bytes(ptr) ⇒ Object

rubocop:disable Naming/MethodName



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# File 'lib/bitcoin/ffi/openssl.rb', line 74

def self.BN_num_bytes(ptr) # rubocop:disable Naming/MethodName
  (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 133

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

.ec_add(point0, point1) ⇒ Object

lifted from github.com/GemHQ/money-tree



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# File 'lib/bitcoin/ffi/openssl.rb', line 351

def self.ec_add(point0, point1)
  init_ffi_ssl

  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  group = EC_KEY_get0_group(eckey)

  point_0_hex = point0.to_bn.to_s(16)
  point_0_pt = EC_POINT_hex2point(group, point_0_hex, nil, nil)
  point_1_hex = point1.to_bn.to_s(16)
  point_1_pt = EC_POINT_hex2point(group, point_1_hex, nil, nil)

  sum_point = EC_POINT_new(group)
  EC_POINT_add(group, sum_point, point_0_pt, point_1_pt, nil)
  hex = EC_POINT_point2hex(group, sum_point, POINT_CONVERSION_UNCOMPRESSED, nil)
  EC_KEY_free(eckey)
  EC_POINT_free(sum_point)
  hex
end

.init_ffi_ssl ⇒ Object 



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# File 'lib/bitcoin/ffi/openssl.rb', line 395

def self.init_ffi_ssl
  @ssl_loaded ||= false
  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 337

def self.recover_compact(hash, signature)
  return false if signature.bytesize != 65
  msg32 = FFI::MemoryPointer.new(:uchar, 32).put_bytes(0, hash)

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

  compressed = version >= 31
  version -= 4 if compressed

  recover_public_key_from_signature(msg32.read_string(32), 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 170

def self.recover_public_key_from_signature(message_hash, signature, rec_id, is_compressed)
  return nil if rec_id < 0 || 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())

  i = 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 { |item| BN_free(item) }
    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 = BN_new()
  rr = BN_new()
  sor = BN_new()
  eor = 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 { |item| BN_free(item) }
  [big_r, big_q].each { |item| EC_POINT_free(item) }

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

  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 81

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 = EC_KEY_get0_group(eckey)
  order = BN_new()
  ctx = 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 = buf.read_string(length).unpack('H*')[0] if i2o_ECPublicKey(eckey, ptr) == length

  EC_KEY_free(eckey)

  [priv_hex, pub_hex]
end

.repack_der_signature(signature) ⇒ Object

repack signature for OpenSSL 1.0.1k handling of DER signatures github.com/bitcoin/bitcoin/pull/5634/files



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# File 'lib/bitcoin/ffi/openssl.rb', line 372

def self.repack_der_signature(signature)
  init_ffi_ssl

  return false if signature.empty?

  # New versions of OpenSSL will reject non-canonical DER signatures. de/re-serialize first.
  norm_der = FFI::MemoryPointer.new(:pointer)
  sig_ptr  = FFI::MemoryPointer.new(:pointer).put_pointer(
    0, FFI::MemoryPointer.from_string(signature)
  )

  norm_sig = d2i_ECDSA_SIG(nil, sig_ptr, signature.bytesize)

  derlen = i2d_ECDSA_SIG(norm_sig, norm_der)
  ECDSA_SIG_free(norm_sig)
  return false if derlen <= 0

  ret = norm_der.read_pointer.read_string(derlen)
  OPENSSL_free(norm_der.read_pointer)

  ret
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 280

def self.sign_compact(hash, private_key, public_key_hex = nil, pubkey_compressed = nil)
  msg32 = FFI::MemoryPointer.new(:uchar, 32).put_bytes(0, hash)

  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
  pubkey_compressed ||= public_key_hex[0..1] != '04'

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

  group = EC_KEY_get0_group(eckey)
  order = BN_new()
  ctx = 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(msg32, msg32.size, eckey)

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

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

  rec_id = nil
  if signature.get_array_of_pointer(0, 2).all? { |i| BN_num_bits(i) <= 256 }
    4.times do |i|
      head = [27 + i + (pubkey_compressed ? 4 : 0)].pack('C')
      recovered_key = recover_public_key_from_signature(
        msg32.read_string(32), [head, r, s].join, i, pubkey_compressed
      )
      if public_key_hex == recovered_key
        rec_id = i
        break
      end
    end
  end

  ECDSA_SIG_free(signature)

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

.signature_to_low_s(signature) ⇒ Object

Regenerate a DER-encoded signature such that the S-value complies with the BIP62 specification.



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# File 'lib/bitcoin/ffi/openssl.rb', line 238

def self.signature_to_low_s(signature)
  init_ffi_ssl

  buf = FFI::MemoryPointer.new(:uint8, 34)
  temp = signature.unpack('C*')
  length_r = temp[3]
  length_s = temp[5 + length_r]
  sig = FFI::MemoryPointer.from_string(signature)

  # Calculate the lower s value
  s = BN_bin2bn(sig[6 + length_r], length_s, BN_new())
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  group = EC_KEY_get0_group(eckey)
  order = BN_new()
  halforder = BN_new()
  ctx = BN_CTX_new()

  EC_GROUP_get_order(group, order, ctx)
  BN_rshift1(halforder, order)
  BN_sub(s, order, s) if BN_cmp(s, halforder) > 0

  BN_free(halforder)
  BN_free(order)
  BN_CTX_free(ctx)

  length_s = BN_bn2bin(s, buf)
  # p buf.read_string(length_s).unpack("H*")

  # Re-encode the signature in DER format
  sig = [0x30, 0, 0x02, length_r]
  sig.concat(temp.slice(4, length_r))
  sig << 0x02
  sig << length_s
  sig.concat(buf.read_string(length_s).unpack('C*'))
  sig[1] = sig.size - 2

  BN_free(s)
  EC_KEY_free(eckey)

  sig.pack('C*')
end