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https://issues.apache.org/jira/browse/WSS-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12469016
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Werner Dittmann commented on WSS-72:
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The change you propose would work. Depending on the underlying
JCE implementation (IAIK) and the strength of the the RSA it may
happen that the JCE implementation throws an exception because
of a small RSA key.
The main topic for this check was to prevent these JCE dependent
exceptions.
Regards,
Werner
> WSSecEncryptedKey rejects a conformant cipher when its getBlockSize() returns > 0
> -------------------------------------------------------------------------------
>
> Key: WSS-72
> URL: https://issues.apache.org/jira/browse/WSS-72
> Project: WSS4J
> Issue Type: Bug
> Environment: Windows XP
> Axis 1.4
> WSS4J 1.5.0
> Reporter: Akitoshi Yoshida
> Assigned To: Davanum Srinivas
>
> Method prepareInternal of WSSecEncrptedKey has the following code fragment:
> Cipher cipher = WSSecurityUtil.getCipherInstance(keyEncAlgo);
> try {
> cipher.init(Cipher.ENCRYPT_MODE, remoteCert);
> } catch (InvalidKeyException e) {
> throw new WSSecurityException(WSSecurityException.FAILED_ENC_DEC,
> null, null, e);
> }
> if (doDebug) {
> log.debug("cipher blksize: " + cipher.getBlockSize()
> + ", symm key length: " + keyBytes.length);
> }
> if (cipher.getBlockSize() < keyBytes.length) {
> throw new WSSecurityException(WSSecurityException.FAILURE,
> "unsupportedKeyTransp",
> new Object[] { "public key algorithm too weak to encrypt "
> + "symmetric key" });
> }
> The getCipherInstance(keyEncAlgo) instantiates a cipher using
> Cipher.getInstance("RSA/NONE/PKCS1PADDING").
> When the cipher is an RSA cipher, as in this case, some securiy providers may
> return 0 for its getBlockSize() method because RSA is not a block cipher. In
> particular, we found out that the IAIK 3.12 has this behavior of returing 0
> for this method.
> This causes the above code to throws the WSSecurityException.
> The documentation at
> http://java.sun.com/j2se/1.4.2/docs/api/javax/crypto/Cipher.html#getBlockSize()
> states that this method should return 0 for non-block ciphers.
> Therefore, we consider this problem to be a bug in WSSecEncrptedKey and
> request that the above if block to be commented out as:
> // RSA is not a block cipher and cipher.getBlockSize() may return 0
> // if (cipher.getBlockSize() < keyBytes.length) {
> // throw new WSSecurityException(WSSecurityException.FAILURE,
> // "unsupportedKeyTransp",
> // new Object[] { "public key algorithm too weak to
> encrypt "
> // + "symmetric key" });
> // }
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