Scala使用RS256生成JWT遇签名错误及密码短语传递问题

问题重现 #

Scala报错代码 #

val jwtPayload = s"""|{
                     |    "exp": $time,
                     |    "iss": "$orgId",
                     |    "sub": "$technicalAccountId",
                     |    "aud": "${imsExp}/c/${clientId}",
                     |    "${imsExp}/s/${metaScope}": true
                     |}""".stripMargin
println(jwtPayload)
val token = Jwts.builder()
  .setPayload(jwtPayload)
  .signWith(SignatureAlgorithm.RS256,privateKey.getBytes("UTF-8"))

报错信息 #

传递字节数组时的错误：

Key bytes may only be specified for HMAC signatures.  If using RSA or Elliptic Curve, use the signWith(SignatureAlgorithm, Key) method instead.
    at io.jsonwebtoken.lang.Assert.isTrue(Assert.java:38)

移除.getBytes("UTF-8")后的错误：

Exception in thread "main" java.lang.IllegalArgumentException: Base64-encoded key bytes may only be specified for HMAC signatures.  If using RSA or Elliptic Curve, use the signWith(SignatureAlgorithm, Key) method instead.

可正常运行的JavaScript代码 #

const jwtPayload = {
        exp: Math.round(300 + Date.now() / 1000),
        iss: secrets.org,
        sub: secrets.id,
        aud: `${secrets.imsEndpoint}/c/${secrets.technicalAccount.clientId}`,
        [`${secrets.imsEndpoint}/s/${secrets.metascopes}`]: true
    };

let token;
try {
    token = jwt.sign(
        jwtPayload,
        { key: secrets.privateKey},
        { algorithm: 'RS256' }
    );
    console.log(token);
} catch (tokenError) {
    return Promise.reject(tokenError);
}

疑问解答 #

1. 解决签名错误 #

报错核心原因：JJWT库对RSA/ECC这类非对称加密算法，要求传入**java.security.Key类型对象**，而非字符串或字节数组。需将PEM格式的私钥字符串解析为PrivateKey实例。

解析PKCS#8格式私钥（无密码）

如果私钥是PKCS#8格式（头尾为-----BEGIN PRIVATE KEY-----/-----END PRIVATE KEY-----）：

import java.security.spec.PKCS8EncodedKeySpec
import java.security.{KeyFactory, PrivateKey}
import java.util.Base64

// 清理PEM格式的冗余内容
val cleanedPrivateKey = privateKey
  .replace("-----BEGIN PRIVATE KEY-----", "")
  .replace("-----END PRIVATE KEY-----", "")
  .replaceAll("\\s+", "")

// Base64解码并生成PrivateKey
val keyBytes = Base64.getDecoder.decode(cleanedPrivateKey)
val keySpec = new PKCS8EncodedKeySpec(keyBytes)
val keyFactory = KeyFactory.getInstance("RSA")
val rsaPrivateKey: PrivateKey = keyFactory.generatePrivate(keySpec)

// 正确生成JWT
val token = Jwts.builder()
  .setPayload(jwtPayload)
  .signWith(SignatureAlgorithm.RS256, rsaPrivateKey)
  .compact() // 必须调用compact()生成最终token字符串

解析PKCS#1格式私钥（无密码）

如果私钥是PKCS#1格式（头尾为-----BEGIN RSA PRIVATE KEY-----/-----END RSA PRIVATE KEY-----），需借助BouncyCastle库解析：

import org.bouncycastle.asn1.pkcs.PrivateKeyInfo
import org.bouncycastle.openssl.PEMParser
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter
import java.io.StringReader

val pemParser = new PEMParser(new StringReader(privateKey))
val keyInfo = pemParser.readObject().asInstanceOf[PrivateKeyInfo]
val converter = new JcaPEMKeyConverter()
val rsaPrivateKey: PrivateKey = converter.getPrivateKey(keyInfo)

2. 传递密码短语（加密私钥） #

如果私钥带密码保护（头尾为-----BEGIN ENCRYPTED PRIVATE KEY-----），解析时需传入密码：

import org.bouncycastle.openssl.PEMDecryptorProvider
import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter
import java.io.StringReader

val password = "你的私钥密码".toCharArray()
val pemParser = new PEMParser(new StringReader(privateKey))
val encryptedKeyPair = pemParser.readObject()
val decryptorProvider = new JcePEMDecryptorProviderBuilder().build(password)
val converter = new JcaPEMKeyConverter()
val rsaPrivateKey: PrivateKey = converter.getPrivateKey(
  encryptedKeyPair.asInstanceOf[org.bouncycastle.openssl.PEMEncryptedKeyPair]
    .decryptKeyPair(decryptorProvider)
)

依赖说明：使用BouncyCastle需添加依赖，以sbt为例：

libraryDependencies += "org.bouncycastle" % "bcprov-jdk15on" % "1.70"

内容的提问来源于stack exchange，提问作者Shivam Sahil