使用pbkdf2 存储密码
关键词 salt 计算次数可控 防止timing attack
class Admin < ActiveRecord::Base
##the table admins in db must has filed username and digest
##http://ruby-doc.org/stdlib-2.0.0/libdoc/openssl/rdoc/OpenSSL/PKCS5.html
def digest=(password)
##strict_encode64 [a-zA-Z0-9+/ pad = ]http://www.rfc-base.org/txt/rfc-3548.txt
salt = Base64.strict_encode64(OpenSSL::Random.random_bytes(16))
iter = 20000
key_len = 16
dg = Base64.strict_encode64(OpenSSL::PKCS5.pbkdf2_hmac_sha1(password, salt, iter, key_len))
super("#{dg}|#{salt}")
end
def check_password(password)
right_digest, salt = self.digest.split('|')
iter = 20000
key_len = 16
dg = Base64.strict_encode64(OpenSSL::PKCS5.pbkdf2_hmac_sha1(password, salt, iter, key_len))
eql_time_cmp(right_digest, dg)
end
#avoid timing attacks
def eql_time_cmp(a, b)
unless a.length == b.length
return false
end
cmp = b.bytes.to_a
result = 0
a.bytes.each_with_index {|c,i| #只要任一表达式的一位为 1，则结果的该位为 1。否则，结果的该位为 0。
result |= c ^ cmp[i] #当且仅当只有一个表达式的某位上为 1 时，结果的该位才为 1。否则结果的该位为 0。
}
result == 0
end
class << self
def create_administrator(username, password)
admin = Admin.new(username: username)
admin.digest = password
admin.save
end
def check_administrator(username, password)
admin = Admin.find_by(username:username)
admin && admin.check_password(password)
end
end
end
timing attack
http://ruby-doc.org/stdlib-2.0.0/libdoc/openssl/rdoc/OpenSSL/PKCS5.html
在这里看到的
知乎上对 timing attack 的一些观点https://www.zhihu.com/question/20156213
