Spring Security PasswordEncoder

Spring Security使用單向密碼轉(zhuǎn)換存儲(chǔ)密碼,也就是加密后的用戶密碼無法恢復(fù)成明文,只能用作密碼比較。另外隨著計(jì)算機(jī)性能的提升,傳統(tǒng)的SHA-256哈希加密方式不再安全。Spring Security采用了自適應(yīng)單向加密方式,它通過刻意消耗計(jì)算機(jī)計(jì)算能力來加強(qiáng)密碼被破解的難度,比如一個(gè)密碼加密一次需要100毫秒,可能破解整個(gè)系統(tǒng)的密碼只需要幾小時(shí),如果一個(gè)密碼加密一次需要1秒那么破解整個(gè)系統(tǒng)的密碼就需要幾天。以BCryptPasswordEncoder為例,它內(nèi)部有一個(gè)叫strength的工作因素,其值范圍是4~31,值越大其循環(huán)加密的次數(shù)就越多。

    public String encode(CharSequence rawPassword) {
        if (rawPassword == null) {
            throw new IllegalArgumentException("rawPassword cannot be null");
        }

        String salt;
        if (random != null) {
            salt = BCrypt.gensalt(version.getVersion(), strength, random);
        } else {
            salt = BCrypt.gensalt(version.getVersion(), strength);
        }
        return BCrypt.hashpw(rawPassword.toString(), salt);
    }

當(dāng)通過BCryptPasswordEncoder.encode進(jìn)行加密的時(shí)候,strength這個(gè)參數(shù)會(huì)被附加到salt中,BCrypt.hashpw通過salt獲取strength,然后通過BCrypt.crypt_raw來使用。

private byte[] crypt_raw(byte password[], byte salt[], int log_rounds,
                            boolean sign_ext_bug, int safety) {
        int rounds, i, j;
        int cdata[] =  bf_crypt_ciphertext.clone();
        int clen = cdata.length;
        byte ret[];

        if (log_rounds < 4 || log_rounds > 31)
            throw new IllegalArgumentException ("Bad number of rounds");
        rounds = 1 << log_rounds;
        if (salt.length != BCRYPT_SALT_LEN)
            throw new IllegalArgumentException ("Bad salt length");

        init_key();
        ekskey(salt, password, sign_ext_bug, safety);
        for (i = 0; i < rounds; i++) {
            key(password, sign_ext_bug, safety);
            key(salt, false, safety);
        }

        for (i = 0; i < 64; i++) {
            for (j = 0; j < (clen >> 1); j++)
                encipher(cdata, j << 1);
        }

        ret = new byte[clen * 4];
        for (i = 0, j = 0; i < clen; i++) {
            ret[j++] = (byte) ((cdata[i] >> 24) & 0xff);
            ret[j++] = (byte) ((cdata[i] >> 16) & 0xff);
            ret[j++] = (byte) ((cdata[i] >> 8) & 0xff);
            ret[j++] = (byte) (cdata[i] & 0xff);
        }
        return ret;
    }

BCrypt.crypt_raw中的入?yún)?code>log_rounds就是之前提到的strength,它通過rounds = 1 << log_rounds;左移獲得一個(gè)循環(huán)數(shù),最終通過該循環(huán)數(shù)提高整個(gè)加密過程的計(jì)算能力消耗。

for (i = 0; i < rounds; i++) {
    key(password, sign_ext_bug, safety);
    key(salt, false, safety);
}

PasswordEncoder接口

String encode(CharSequence rawPassword);
boolean matches(CharSequence rawPassword, String encodedPassword);

PasswordEncoder接口是Spring Security提供的統(tǒng)一密碼接口,主要為整個(gè)安全框架提供一個(gè)統(tǒng)一的加密過程。其主要的實(shí)現(xiàn)類如下:

  • DelegatingPasswordEncoder
  • BCryptPasswordEncoder
  • Argon2PasswordEncoder
  • Pbkdf2PasswordEncoder
  • SCryptPasswordEncoder
  • Other PasswordEncoders
    除了其它加密算法,以上所列的加密算法都是Spring Security所推薦的,而其它算法主要是為了系統(tǒng)兼容性而存在,但是不再推薦使用。

DelegatingPasswordEncoder

DelegatingPasswordEncoder是Spring Security默認(rèn)使用的加密算法。我們從它的名稱其實(shí)可以猜測(cè)出來它本身并不是一個(gè)具體的算法實(shí)現(xiàn)類,而是一個(gè)算法代理類。這個(gè)類主要目的是兼容老舊系統(tǒng),方便老舊系統(tǒng)的升級(jí)改造。

PasswordEncoder passwordEncoder =
    PasswordEncoderFactories.createDelegatingPasswordEncoder();

DelegatingPasswordEncoder可以通PasswordEncoderFactories.createDelegatingPasswordEncoder()來創(chuàng)建一個(gè)默認(rèn)的實(shí)現(xiàn)方式。

public static PasswordEncoder createDelegatingPasswordEncoder() {
        String encodingId = "bcrypt";
        Map<String, PasswordEncoder> encoders = new HashMap<>();
        encoders.put(encodingId, new BCryptPasswordEncoder());
        encoders.put("ldap", new org.springframework.security.crypto.password.LdapShaPasswordEncoder());
        encoders.put("MD4", new org.springframework.security.crypto.password.Md4PasswordEncoder());
        encoders.put("MD5", new org.springframework.security.crypto.password.MessageDigestPasswordEncoder("MD5"));
        encoders.put("noop", org.springframework.security.crypto.password.NoOpPasswordEncoder.getInstance());
        encoders.put("pbkdf2", new Pbkdf2PasswordEncoder());
        encoders.put("scrypt", new SCryptPasswordEncoder());
        encoders.put("SHA-1", new org.springframework.security.crypto.password.MessageDigestPasswordEncoder("SHA-1"));
        encoders.put("SHA-256", new org.springframework.security.crypto.password.MessageDigestPasswordEncoder("SHA-256"));
        encoders.put("sha256", new org.springframework.security.crypto.password.StandardPasswordEncoder());
        encoders.put("argon2", new Argon2PasswordEncoder());

        return new DelegatingPasswordEncoder(encodingId, encoders);
    }

PasswordEncoderFactories.createDelegatingPasswordEncoder()會(huì)首先創(chuàng)建一個(gè)Map,然后將各種PasswordEncoder的具體算法對(duì)象存入Map中。那么如何使用DelegatingPasswordEncoder呢?

{bcrypt}$2a$10$dXJ3SW6G7P50lGmMkkmwe.20cQQubK3.HZWzG3YB1tlRy.fqvM/BG 
{noop}password 
{pbkdf2}5d923b44a6d129f3ddf3e3c8d29412723dcbde72445e8ef6bf3b508fbf17fa4ed4d6b99ca763d8dc 
{scrypt}$e0801$8bWJaSu2IKSn9Z9kM+TPXfOc/9bdYSrN1oD9qfVThWEwdRTnO7re7Ei+fUZRJ68k9lTyuTeUp4of4g24hHnazw==$OAOec05+bXxvuu/1qZ6NUR+xQYvYv7BeL1QxwRpY5Pc=  
{sha256}97cde38028ad898ebc02e690819fa220e88c62e0699403e94fff291cfffaf8410849f27605abcbc0

以上就是DelegatingPasswordEncoder所存儲(chǔ)的密碼例子,其具體格式如下

{id}encodedPassword

其中{id}就是所使用的加密算法,encodedPassword就是{id}所對(duì)應(yīng)的具體加密算法加密后的值。

{bcrypt}$2a$10$dXJ3SW6G7P50lGmMkkmwe.20cQQubK3.HZWzG3YB1tlRy.fqvM/BG

{bcrypt}為例,DelegatingPasswordEncoder會(huì)首先解析出{bcrypt},然后在Map中查找具體的實(shí)現(xiàn)算法,最終由BCryptPasswordEncoder來完成加密或匹配過程。

參考資源

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