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;
}
在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
以{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。