module OpenSSL::PKCS1
Public Class Methods
add_oaep_mgf1(str, len, label = '', md = nil, mgf1md = nil)
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# File lib/openssl/oaep.rb, line 23 def add_oaep_mgf1(str, len, label = '', md = nil, mgf1md = nil) md ||= OpenSSL::Digest::SHA1 mgf1md ||= md mdlen = md.new.digest_length z_len = len - str.bytesize - 2 * mdlen - 2 if z_len < 0 raise OpenSSL::PKey::RSAError, 'data too large for key size' end if len < 2 * mdlen + 1 raise OpenSSL::PKey::RSAError, 'key size too small' end l_hash = md.digest(label) db = l_hash + ([0] * z_len + [1]).pack('C*') + [str].pack('a*') seed = SecureRandom.random_bytes(mdlen) masked_db = mgf1_xor(db, seed, mgf1md) masked_seed = mgf1_xor(seed, masked_db, mgf1md) [0, masked_seed, masked_db].pack('Ca*a*') end
check_oaep_mgf1(str, label = '', md = nil, mgf1md = nil)
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# File lib/openssl/oaep.rb, line 48 def check_oaep_mgf1(str, label = '', md = nil, mgf1md = nil) md ||= OpenSSL::Digest::SHA1 mgf1md ||= md mdlen = md.new.digest_length em = str.bytes if em.size < 2 * mdlen + 2 raise OpenSSL::PKey::RSAError end # Keep constant calculation even if the text is invaid in order to avoid attacks. good = secure_byte_is_zero(em[0]) masked_seed = em[1...1+mdlen].pack('C*') masked_db = em[1+mdlen...em.size].pack('C*') seed = mgf1_xor(masked_seed, masked_db, mgf1md) db = mgf1_xor(masked_db, seed, mgf1md) db_bytes = db.bytes l_hash = md.digest(label) good &= secure_hash_eq(l_hash.bytes, db_bytes[0...mdlen]) one_index = 0 found_one_byte = 0 (mdlen...db_bytes.size).each do |i| equals1 = secure_byte_eq(db_bytes[i], 1) equals0 = secure_byte_is_zero(db_bytes[i]) one_index = secure_select(~found_one_byte & equals1, i, one_index) found_one_byte |= equals1 good &= (found_one_byte | equals0) end good &= found_one_byte if good.zero? raise OpenSSL::PKey::RSAError end db_bytes[one_index+1...db_bytes.size].pack('C*') end
mgf1_xor(out, seed, md)
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# File lib/openssl/oaep.rb, line 91 def mgf1_xor(out, seed, md) counter = 0 out_bytes = out.bytes mask_bytes = [] while mask_bytes.size < out_bytes.size mask_bytes += md.digest([seed, counter].pack('a*N')).bytes counter += 1 end out_bytes.size.times do |i| out_bytes[i] ^= mask_bytes[i] end out_bytes.pack('C*') end
secure_byte_eq(v1, v2)
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# File lib/openssl/oaep.rb, line 112 def secure_byte_eq(v1, v2) secure_byte_is_zero(v1 ^ v2) end
secure_byte_is_zero(v)
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Constant time comparistion utilities.
# File lib/openssl/oaep.rb, line 108 def secure_byte_is_zero(v) v-1 >> 8 end
secure_hash_eq(vs1, vs2)
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# File lib/openssl/oaep.rb, line 120 def secure_hash_eq(vs1, vs2) # Assumes the given hash values have the same size. # This check is not constant time, but should not depends on the texts. return 0 unless vs1.size == vs2.size res = secure_byte_is_zero(0) (0...vs1.size).each do |i| res &= secure_byte_eq(vs1[i], vs2[i]) end res end
secure_select(mask, eq, ne)
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# File lib/openssl/oaep.rb, line 116 def secure_select(mask, eq, ne) (mask & eq) | (~mask & ne) end
Private Instance Methods
add_oaep_mgf1(str, len, label = '', md = nil, mgf1md = nil)
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# File lib/openssl/oaep.rb, line 23 def add_oaep_mgf1(str, len, label = '', md = nil, mgf1md = nil) md ||= OpenSSL::Digest::SHA1 mgf1md ||= md mdlen = md.new.digest_length z_len = len - str.bytesize - 2 * mdlen - 2 if z_len < 0 raise OpenSSL::PKey::RSAError, 'data too large for key size' end if len < 2 * mdlen + 1 raise OpenSSL::PKey::RSAError, 'key size too small' end l_hash = md.digest(label) db = l_hash + ([0] * z_len + [1]).pack('C*') + [str].pack('a*') seed = SecureRandom.random_bytes(mdlen) masked_db = mgf1_xor(db, seed, mgf1md) masked_seed = mgf1_xor(seed, masked_db, mgf1md) [0, masked_seed, masked_db].pack('Ca*a*') end
check_oaep_mgf1(str, label = '', md = nil, mgf1md = nil)
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# File lib/openssl/oaep.rb, line 48 def check_oaep_mgf1(str, label = '', md = nil, mgf1md = nil) md ||= OpenSSL::Digest::SHA1 mgf1md ||= md mdlen = md.new.digest_length em = str.bytes if em.size < 2 * mdlen + 2 raise OpenSSL::PKey::RSAError end # Keep constant calculation even if the text is invaid in order to avoid attacks. good = secure_byte_is_zero(em[0]) masked_seed = em[1...1+mdlen].pack('C*') masked_db = em[1+mdlen...em.size].pack('C*') seed = mgf1_xor(masked_seed, masked_db, mgf1md) db = mgf1_xor(masked_db, seed, mgf1md) db_bytes = db.bytes l_hash = md.digest(label) good &= secure_hash_eq(l_hash.bytes, db_bytes[0...mdlen]) one_index = 0 found_one_byte = 0 (mdlen...db_bytes.size).each do |i| equals1 = secure_byte_eq(db_bytes[i], 1) equals0 = secure_byte_is_zero(db_bytes[i]) one_index = secure_select(~found_one_byte & equals1, i, one_index) found_one_byte |= equals1 good &= (found_one_byte | equals0) end good &= found_one_byte if good.zero? raise OpenSSL::PKey::RSAError end db_bytes[one_index+1...db_bytes.size].pack('C*') end
mgf1_xor(out, seed, md)
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# File lib/openssl/oaep.rb, line 91 def mgf1_xor(out, seed, md) counter = 0 out_bytes = out.bytes mask_bytes = [] while mask_bytes.size < out_bytes.size mask_bytes += md.digest([seed, counter].pack('a*N')).bytes counter += 1 end out_bytes.size.times do |i| out_bytes[i] ^= mask_bytes[i] end out_bytes.pack('C*') end
secure_byte_eq(v1, v2)
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# File lib/openssl/oaep.rb, line 112 def secure_byte_eq(v1, v2) secure_byte_is_zero(v1 ^ v2) end
secure_byte_is_zero(v)
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Constant time comparistion utilities.
# File lib/openssl/oaep.rb, line 108 def secure_byte_is_zero(v) v-1 >> 8 end
secure_hash_eq(vs1, vs2)
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# File lib/openssl/oaep.rb, line 120 def secure_hash_eq(vs1, vs2) # Assumes the given hash values have the same size. # This check is not constant time, but should not depends on the texts. return 0 unless vs1.size == vs2.size res = secure_byte_is_zero(0) (0...vs1.size).each do |i| res &= secure_byte_eq(vs1[i], vs2[i]) end res end
secure_select(mask, eq, ne)
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# File lib/openssl/oaep.rb, line 116 def secure_select(mask, eq, ne) (mask & eq) | (~mask & ne) end