Question

我已经开始使用JJWT来处理我的服务器应用程序上的JWT。

我的JWT密码将存储在resources文件夹中，我将使用Properties类加载密码。

JJWT提供了三种签署JWT的方法，一种使用byte[]，另一种使用String，另一种使用Key：

JwtBuilder signWith(SignatureAlgorithm var1, byte[] var2);

JwtBuilder signWith(SignatureAlgorithm var1, String var2);

JwtBuilder signWith(SignatureAlgorithm var1, Key var2);

问题：关于安全性，字符集和其他问题，我应该使用哪些建议？

有一段时间，我支持String，因为Properties会返回String。

Answer 1

由于原始字符串与Base64编码字符串之间存在混淆，因此JJWT＆gt; = 0.10.0，signWith(SignatureAlgorithm var1, String var2)已被弃用：

/**
 * Signs the constructed JWT using the specified algorithm with the specified key, producing a JWS.
 *
 * <p>This is a convenience method: the string argument is first BASE64-decoded to a byte array and this resulting
 * byte array is used to invoke {@link #signWith(SignatureAlgorithm, byte[])}.</p>
 *
 * <h4>Deprecation Notice: Deprecated as of 0.10.0, will be removed in the 1.0 release.</h4>
 *
 * <p>This method has been deprecated because the {@code key} argument for this method can be confusing: keys for
 * cryptographic operations are always binary (byte arrays), and many people were confused as to how bytes were
 * obtained from the String argument.</p>
 *
 * <p>This method always expected a String argument that was effectively the same as the result of the following
 * (pseudocode):</p>
 *
 * <p>{@code String base64EncodedSecretKey = base64Encode(secretKeyBytes);}</p>
 *
 * <p>However, a non-trivial number of JJWT users were confused by the method signature and attempted to
 * use raw password strings as the key argument - for example {@code signWith(HS256, myPassword)} - which is
 * almost always incorrect for cryptographic hashes and can produce erroneous or insecure results.</p>
 *
 * <p>See this
 * <a href="https://stackoverflow.com/questions/40252903/static-secret-as-byte-key-or-string/40274325#40274325">
 * StackOverflow answer</a> explaining why raw (non-base64-encoded) strings are almost always incorrect for
 * signature operations.</p>
 *
 * <p>To perform the correct logic with base64EncodedSecretKey strings with JJWT >= 0.10.0, you may do this:
 * <pre><code>
 * byte[] keyBytes = {@link Decoders Decoders}.{@link Decoders#BASE64 BASE64}.{@link Decoder#decode(Object) decode(base64EncodedSecretKey)};
 * Key key = {@link Keys Keys}.{@link Keys#hmacShaKeyFor(byte[]) hmacShaKeyFor(keyBytes)};
 * jwtBuilder.signWith(key); //or {@link #signWith(Key, SignatureAlgorithm)}
 * </code></pre>
 * </p>
 *
 * <p>This method will be removed in the 1.0 release.</p>
 *
 * @param alg                    the JWS algorithm to use to digitally sign the JWT, thereby producing a JWS.
 * @param base64EncodedSecretKey the BASE64-encoded algorithm-specific signing key to use to digitally sign the
 *                               JWT.
 * @return the builder for method chaining.
 * @throws InvalidKeyException if the Key is insufficient or explicitly disallowed by the JWT specification as
 *                             described by {@link SignatureAlgorithm#forSigningKey(Key)}.
 * @deprecated as of 0.10.0: use {@link #signWith(Key)} or {@link #signWith(Key, SignatureAlgorithm)} instead.  This
 * method will be removed in the 1.0 release.
 */
JwtBuilder signWith(SignatureAlgorithm alg, String base64EncodedSecretKey);

此方法要求字符串参数为Base64编码的密钥字节数组。它不假设一般字符串，例如用户密码，作为签名密钥。 JJWT采用Base64编码，因为如果您指定不 Base64编码的字符串密码，您可能使用格式不良或弱密钥。

JWT JWA规范REQUIRES，HMAC签名密钥的长度等于或大于签名字节数组长度。

这意味着：

| If you're signing with: | your key (byte array) length MUST be: |
| ----------------------- | ------------------------------------- |
| HMAC SHA 256            | >= 256 bits (32 bytes)                |
| HMAC SHA 384            | >= 384 bits (48 bytes)                |
| HMAC SHA 512            | >= 512 bits (64 bytes)                |

许多在线JWT网站和工具只是弄错了 - 它们允许您认为您可以输入或使用任何旧字符串并且您很好。有些人甚至用密钥secret预先填充密钥（显然是一个坏主意，甚至不符合规范，因为它太短了！）。

为了帮助您简化操作，JJWT提供了一个实用程序，可帮助您通过io.jsonwebtoken.security.Keys类secretKeyFor方法生成适合符合规范的签名的足够安全随机密钥。例如：

//creates a spec-compliant secure-random key:
SecretKey key = Keys.secretKeyFor(SignatureAlgorithm.HS256); //or HS384 or HS512

如果您想将生成的密钥存储为字符串，您可能会对其进行Base64编码：

String base64Key = Encoders.BASE64.encode(key.getEncoded());

但请注意：生成的base64Key字符串不被认为是安全的，无法向任何人展示。 Base64编码不是加密 - 值仍然需要保密。你如何做到这一点取决于你（加密等）。

现在，当创建JWS时，可以传递base64Key值，JJWT知道base64首先解码它以获取实际字节，然后是用于计算签名：

Jwts.builder()
    //...
    .signWith(SignatureAlgorithm.HS512, base64Key)
    .compact();

虽然您可以这样做，但由于原始字符串和base64编码字符串之间存在歧义，因此不建议根据JavaDoc中的上述弃用通知。

因此，建议使用JWT构建器的signWith(Key)或signWith(Key, SignatureAlgorithm)方法来保证类型安全的Key参数。例如：

  Jwts.builder()
    //...
    .signWith(key) // or signWith(key, preferredSignatureAlgorithm)
    .compact();

建议

signWith(Key)让JJWT根据您提供的密钥的强度找出最强的算法。 signWith(Key,SignatureAlgorithm)允许您指定所需的算法，如果您不想要最强的算法。

这两种方法都会拒绝任何不符合最低RFC要求的Key。

静态密钥为byte []，Key还是String？

1 个答案: