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I have a kafka message that was encrypted on java with the following code:

    private String decryptedMessage(String key, String encryptedMessage) throws NoSuchAlgorithmException, InvalidKeySpecException, ParseException, JOSEException {

        PrivateKey privateKey = <some way to generate a private key from key>;

        JWEDecrypter decrypter = new RSADecrypter(privateKey);
        JWEObject decryptedJweObj = JWEObject.parse(encryptedMessage);
        decryptedJweObj.decrypt(decrypter);
        return decryptedJweObj.getPayload().toJSONObject().toJSONString();
    }

Now I'm trying to decode it using python on a decoded message where I already know the private key. I tried using jwcrypto (since I'm using python3 and jeso is only for 2.x) using this code like in their documents, but it didn't work:

enc = '<encrypted message>'
private = '<private key>'
jwetoken = jwe.JWE()
jwetoken.deserialize(enc, key=private_key)
payload = jwetoken.payload

And I get this error code: jwcrypto.jwe.InvalidJWEData: No recipient matched the provided key["Failed: [ValueError('key is not a JWK object',)]"] I tried looking for a way to make the private key a JWK object but couldn't find one.

I know my message is JWE since it's split by 4 dots and when I base64 decode the first part I get this json: b'{"alg":"RSA-OAEP-256","enc":"A256GCM","kid":"<some key id>"}'

So I'm kind of stuck on how to decode my message.

Decrypted string: {"value":"Object Encryption"}

Encrypted string:

eyJhbGciOiJSU0EtT0FFUC0yNTYiLCJlbmMiOiJBMjU2R0NNIiwia2lkIjoiYjFhOWVmNzAtYjQ4Yy00YzdiLWI0ZTQtODU2YzQyNGIyYzZlIn0.XzLgQTzESD7mg-DtiwFaOQQIfJjQOox5Efbq3Cn8n4H0OZUNvNFWuLr2gPH4WqhWZFYvYh6Mx3--bKiYA_kGplPaJUdPfuYx3OgOug9fuYMrZesE-9stJFd4TnQOJcrTfehJkI_QKPqfWgbEgh1Zn8r7DuIBbABmNK4OHa0edwUA0Lu4mUxzRW6UPaNdWtfEGL9ZVR4lzUx6QX6nweKdbi8tkDnQrSNcQ4eZKIn8mVl5rL3s-qa2VC1Zvo4R-eA4jTKs6WQrkPChJkfoECcYcLx7SIHdxP6VB9DAhW-TwRizr5OZUVLLLH3UEOF77Rtc6MLL4Al5mo29sE-E1faywQ.R1QE-zY29Ed7yfqX.-soXsfltkJL0AXk_q5tPn9hagCBG_1c03VKdh2A.-oteTYv0SHzE4yBmZlterg

Decryption key (need to decode with base64):

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
Ema Il
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  • I can' t reproduce this. Encrypted tokens that can be decrypted with the Java code (which, by the way, does not encrypt) can also be decrypted with the Python code. I guess it's your data. Please post complete test data: Private and public test key and encrypted token. – Topaco Apr 19 '22 at 19:23
  • @Topaco I added what you requested – Ema Il Apr 20 '22 at 10:40

1 Answers1

2

The posted encrypted token can be decrypted with the posted RSA key and the Python library JWCrypto. Maybe it doesn't work for you because of a key import bug.

The posted RSA key is a DER encoded PKCS#8 key (Base64 encoded). JWCrypto does not support this encoding directly, but only the PEM encoding, which is not too bad, because the conversion from DER to PEM is trivial: The Base64 string must be formatted (line break after every 64 characters) and the header (-----BEGIN PRIVATE KEY-----) and footer (-----END PRIVATE KEY-----) must be added each in a separate line.

Alternatively, the key can be converted to a JWK and imported in this format.

The following Python code shows these two variants based on the posted data. For this the JWK was derived with online tools from the posted PKCS#8 key:

pkcs8pem = b'''-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----'''

jwkey = {"p":"0zkaJztRayAKNlZ7EEtC6uhHcUc8z_avZh7bSTSSuXhFz-7DUnUw67nZOLaa98717SuG_uEogg64gOVUyR4XRhd8MKoUe-l094C6F2SxmJcfuEbzG7iBQxpFHnvt_U9v_zM7RGYLd0zNy3ARRI00VfIM6RSbI_MHmtxOAfJThGU","kty":"RSA","q":"xBZH3YCATbv98B_s9rquNJGJZDEW-MEKvAo5sF2MRrtVkd0mJ9szUE7GUegbYhxc8f9-1tu_XTvO7vawGzbmOVfVWECo8WQ9pYnWEP9MNO5DtT4TbiEi6ap9gG4i3M5S5bl_HR6S6W-VBviVpaooeVQQgxZLZlVJTFbXhz2ttVc","d":"E3IcJtrMYmK0WdfiKI_RFSAd7-ruBV7SV9NPELJtLNE9ykNA9RtWhrKYBwXQFFYH6TR5CO0l86HmZiVOWFXOFquAxY9t8a1NX9jOjNLAag9gpZQr48xayfmilQkLkoo4Rfq6vs_OkSzE4zyr0zpRoyOe3g0ZbC58W9OCu9r7wVTDV-KKE8ChU39Ae8HLfMEQXWSIUqxbrpw-mLeFX1qh5ILNBDA9M6vD-JuoiuIZltW4djnlU4hxYPVwTyuPBCQ3AwJsRGcddfxWTI-kIm2_6k8HzhdpB1ajBrZX_XVeXAp7VlvyHzBZ5ri1NDpr_Cyh6o2ysdB8qGCnlDcsNHLl-Q","e":"AQAB","kid":"79635991-092f-4576-a23a-4cbab618e8a8","qi":"neqj96k7vECzpWGn7ydrRO_3cmLaQK8DXiI4T4_TyxqV2ykHg0RWK0ZqG6-tPHwIoPIvU8MflfUxNpu8j8tjDqT-CfM6FJfcxM_eox6k0SrUDlyG8wkeExLvb-0A8ohe7H4CAORK-rz4bTYMVYOkX1twGgg0v_z3A5RwR85C3LQ","dp":"KSkQeqKpjAmTU-FoW9V-tc4L1fw-0nvM1EahDtPq36-bUxjBATmLDfSKau3SpwWykMQRq2tu_GEn_R4zdnmhqWv8LHOISFlHDNAN828Q2J5idQOGbll2_v-Ihpc52kn3ljCClSKZi2bxF3rAMq6diz3-3BDC5q9-ROQ3Y1O4iK0","dq":"m7Q1jKWlPBSzKCGxwJmsCwIl3vE8FHr1Uyurc2hVIzVOVW0OB0gADxz-TbvJQrbS9zayOVp1Mktznj00yedmGNKuDk4J2OSILxKscQLIOJ-aFCketKyLVJCU546NEFilatVJIo5MiiCYbdimu83KJc2i7vSdGr1OXtf2fOV1MjE","n":"ocoaOeFcThmA8azdqYzPP6QPeJHKpTDWdDUiKEh4WrAJu9l-ulzfRiNiGqUBE8u_oDQSgVrM1p-CbDbgGyyzaec3k5Zsx6dPXnuC_oPLPzSCjMAOTIMfcBrth4tH6IdKRKwDCkFegiwSVHweSVLvT19jBA-2dlxhtEWApUjBDvC-4h15taKAq_N61P1OcV8Kbk66eC_Z2A_XgehKbQoDlhIvfJauaHkFzcln7Yt_4HJGrYVIvFiDZSPuf3z7-2VnfWetFVwFX2-bvOtf3qyIRCCUZKmw13P1CwELAHhClWMx6UrTPSJ99JkHaehHWOPIpmYh49RjYD72PjA98D5nUw"}

enc = 'eyJhbGciOiJSU0EtT0FFUC0yNTYiLCJlbmMiOiJBMjU2R0NNIiwia2lkIjoiYjFhOWVmNzAtYjQ4Yy00YzdiLWI0ZTQtODU2YzQyNGIyYzZlIn0.XzLgQTzESD7mg-DtiwFaOQQIfJjQOox5Efbq3Cn8n4H0OZUNvNFWuLr2gPH4WqhWZFYvYh6Mx3--bKiYA_kGplPaJUdPfuYx3OgOug9fuYMrZesE-9stJFd4TnQOJcrTfehJkI_QKPqfWgbEgh1Zn8r7DuIBbABmNK4OHa0edwUA0Lu4mUxzRW6UPaNdWtfEGL9ZVR4lzUx6QX6nweKdbi8tkDnQrSNcQ4eZKIn8mVl5rL3s-qa2VC1Zvo4R-eA4jTKs6WQrkPChJkfoECcYcLx7SIHdxP6VB9DAhW-TwRizr5OZUVLLLH3UEOF77Rtc6MLL4Al5mo29sE-E1faywQ.R1QE-zY29Ed7yfqX.-soXsfltkJL0AXk_q5tPn9hagCBG_1c03VKdh2A.-oteTYv0SHzE4yBmZlterg'

from jwcrypto import jwk, jwe

# Import of a PEM encoded PKCS#8 key
private_key = jwk.JWK.from_pem(pkcs8pem)
jwetoken = jwe.JWE()
jwetoken.deserialize(enc, key=private_key)
payload = jwetoken.payload
print(payload.decode('utf-8'))

# Import of a JWK
private_key = jwk.JWK(**jwkey)
jwetoken = jwe.JWE()
jwetoken.deserialize(enc, key=private_key)
payload = jwetoken.payload
print(payload.decode('utf-8'))

with the output:

{"value":"Object Encryption"}
{"value":"Object Encryption"}
Topaco
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  • Thanks you very much! I don't think I could've got to it by myself. Can you please explain how you got to the jwkey json from the decryption key? when I decoded it with base64 that's not what I got. – Ema Il Apr 20 '22 at 13:54
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    There are many ways, e.g.: 1. the `export()` method: `print(private_key.export())`. 2. online tools, e.g. [here](https://8gwifi.org/jwkconvertfunctions.jsp). However, this site only handles PKCS#1 keys, so the PKCS#8 key must be converted first, e.g. [here](https://8gwifi.org/pemconvert.jsp). 3. explicit creation according to [RFC 7515](https://datatracker.ietf.org/doc/html/rfc7517#page-26), where the key values have to be determined from the PKCS#8 key using an ASN.1 parser, e.g. [here](https://lapo.it/asn1js/). Etc. – Topaco Apr 20 '22 at 14:39
  • Thanks! I that for what I need adding the header and footer is easier to work with. I really appreciate the help. – Ema Il Apr 20 '22 at 15:08