How to load PEM encoded Elliptic Curve public keys

问题:

I have a PEM encoded Elliptic Curve public key that I'm trying to load into Bouncy Castle and everything I tried so far is failing. This is an example of the key I'm trying to load:

-----BEGIN PUBLIC KEY-----
MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBhsFCcWY2GaiN1BjPEd1v+ESKO6/0
D0sUR4y1amHnOr3FZx6TdqdoSBqxownQrnAKGCwagGxUb7BWwPFgHqKQJHgBq+J7
F+6m5SKAEL1wS5pqya91N7oudF3yFW8oZRE4RQRdSLl3fV2aVXKwGDXciwhUhw8k
x5OS4iZpMAY+LI4WVGU=
-----END PUBLIC KEY-----

It is generated by NodeJS Crypto module and the curve name is secp521r1. It's later on encoded into PEM by the npm package key-encoder. I already used it in JavaScript (ClojureScript actually) to verify a signature and now I need to verify the signature on the server with Java (Clojure actually).

I tried removing the guards from the key, coverting to a byte[] and creating a X509EncodedKeySpec. That didn't work. It crashed with:

InvalidKeySpecException encoded key spec not recognised  org.bouncycastle.jcajce.provider.asymmetric.util.BaseKeyFactorySpi.engineGeneratePublic (:-1)

The code to I'm using to load the key:

KeyFactory.
  getInstance("ECDSA", "BC").
  generatePublic(new X509EncodedKeySpec(publicKey.getBytes()))

Just in case, this is my Clojure code:

(-> (KeyFactory/getInstance "ECDSA")
    (.generatePublic (X509EncodedKeySpec. (.getBytes public-key)))) 

I also tried PKCS8EncodedKeySpec but I got the error:

InvalidKeySpecException key spec not recognised  org.bouncycastle.jcajce.provider.asymmetric.util.BaseKeyFactorySpi.engineGeneratePublic (:-1)

I also tried this method here: https://gist.github.com/wuyongzheng/0e2ed6d8a075153efcd3#file-ecdh_bc-java-L47-L50 but when running decodePoint I get the error:

IllegalArgumentException Invalid point encoding 0x4d  org.bouncycastle.math.ec.ECCurve.decodePoint (:-1)

when I removed the guards and:

IllegalArgumentException Invalid point encoding 0x2d  org.bouncycastle.math.ec.ECCurve.decodePoint (:-1)

with the guards on.

Any ideas what I'm doing wrong or how to fix it?

Also, in case it helps, this is the private key:

-----BEGIN EC PRIVATE KEY-----
MIHbAgEBBEEjNeo52qeffbIQvSxRcWAPlyJjeEOov2JNxxwWKCtlowi07HsYNNyE
jFDdSn8tSYAGx0rROrgpGuuJoG0zarPKz6AHBgUrgQQAI6GBiQOBhgAEAYbBQnFm
NhmojdQYzxHdb/hEijuv9A9LFEeMtWph5zq9xWcek3anaEgasaMJ0K5wChgsGoBs
VG+wVsDxYB6ikCR4AaviexfupuUigBC9cEuaasmvdTe6LnRd8hVvKGUROEUEXUi5
d31dmlVysBg13IsIVIcPJMeTkuImaTAGPiyOFlRl
-----END EC PRIVATE KEY-----

and everything seems to be valid:

$ openssl ec -in private.pem  -pubout
read EC key
writing EC key
-----BEGIN PUBLIC KEY-----
MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBhsFCcWY2GaiN1BjPEd1v+ESKO6/0
D0sUR4y1amHnOr3FZx6TdqdoSBqxownQrnAKGCwagGxUb7BWwPFgHqKQJHgBq+J7
F+6m5SKAEL1wS5pqya91N7oudF3yFW8oZRE4RQRdSLl3fV2aVXKwGDXciwhUhw8k
x5OS4iZpMAY+LI4WVGU=
-----END PUBLIC KEY-----

回答1:

Doing a bit of massaging I finally managed to load it:

(require '[clojure.string :as s])
(import '[java.security KeyFactory]
        '[java.security.spec X509EncodedKeySpec]
        '[java.util Base64])

(def public-key "-----BEGIN PUBLIC KEY-----
MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBhsFCcWY2GaiN1BjPEd1v+ESKO6/0
D0sUR4y1amHnOr3FZx6TdqdoSBqxownQrnAKGCwagGxUb7BWwPFgHqKQJHgBq+J7
F+6m5SKAEL1wS5pqya91N7oudF3yFW8oZRE4RQRdSLl3fV2aVXKwGDXciwhUhw8k
x5OS4iZpMAY+LI4WVGU=
-----END PUBLIC KEY-----")

(as-> public-key key
      (s/replace key "-----BEGIN PUBLIC KEY-----" "")
      (s/replace key "-----END PUBLIC KEY-----" "")
      (s/replace key #"\s" "")
      (.decode (Base64/getDecoder) key)
      (X509EncodedKeySpec. key)
      (.generatePublic (KeyFactory/getInstance "ECDSA" "BC") key))

回答2:

Since you have BC, it can dePEMify instead of doing it 'by hand' (I only do plain Java):

Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
Reader rdr = new StringReader("-----BEGIN PUBLIC KEY-----\n"
        +"MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBhsFCcWY2GaiN1BjPEd1v+ESKO6/0\n"
        +"D0sUR4y1amHnOr3FZx6TdqdoSBqxownQrnAKGCwagGxUb7BWwPFgHqKQJHgBq+J7\n"
        +"F+6m5SKAEL1wS5pqya91N7oudF3yFW8oZRE4RQRdSLl3fV2aVXKwGDXciwhUhw8k\n"
        +"x5OS4iZpMAY+LI4WVGU=\n" +"-----END PUBLIC KEY-----\n"); // or from file etc.

org.bouncycastle.util.io.pem.PemObject spki = new org.bouncycastle.util.io.pem.PemReader(rdr).readPemObject();
PublicKey key = KeyFactory.getInstance("EC","BC").generatePublic(new X509EncodedKeySpec(spki.getContent()));

System.out.println (key.getAlgorithm() + " " + ((ECPublicKey)key).getW().toString());

Example output:
EC java.security.spec.ECPoint@47244700

FYI, PKCS8 encoding is only for private keys; see javadoc for java.security.Key.getFormat()