有两个通常引用的解决方案。不幸的是,这些都不是完全令人满意的:
private static void removeCryptographyRestrictions() {
if (!isRestrictedCryptography()) {
logger.fine("Cryptography restrictions removal not needed");
return;
}
try {
/*
* Do the following, but with reflection to bypass access checks:
*
* JceS@R_301_1360@.isRestricted = false;
* JceS@R_301_1360@.defaultPolicy.perms.clear();
* JceS@R_301_1360@.defaultPolicy.add(CryptoAllPermission.INSTANCE);
*/
final Class<?> jceS@R_301_1360@ = Class.forName("javax.crypto.JceS@R_301_1360@");
final Class<?> cryptoPermissions = Class.forName("javax.crypto.CryptoPermissions");
final Class<?> cryptoAllPermission = Class.forName("javax.crypto.CryptoAllPermission");
final Field isRestrictedField = jceS@R_301_1360@.getDeclaredField("isRestricted");
isRestrictedField.setAccessible(true);
final Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(isRestrictedField, isRestrictedField.getModifiers() & ~Modifier.FINAL);
isRestrictedField.set(null, false);
final Field defaultPolicyField = jceS@R_301_1360@.getDeclaredField("defaultPolicy");
defaultPolicyField.setAccessible(true);
final PermissionCollection defaultPolicy = (PermissionCollection) defaultPolicyField.get(null);
final Field perms = cryptoPermissions.getDeclaredField("perms");
perms.setAccessible(true);
((Map<?, ?>) perms.get(defaultPolicy)).clear();
final Field instance = cryptoAllPermission.getDeclaredField("INSTANCE");
instance.setAccessible(true);
defaultPolicy.add((Permission) instance.get(null));
logger.fine("Successfully removed cryptography restrictions");
} catch (final Exception e) {
logger.log(Level.WARNING, "Failed to remove cryptography restrictions", e);
}
}
private static boolean isRestrictedCryptography() {
// This matches Oracle Java 7 and 8, but not Java 9 or OpenJDK.
final String name = System.getProperty("java.runtime.name");
final String ver = System.getProperty("java.version");
return name != null && name.equals("Java(TM) SE Runtime Environment")
&& ver != null && (ver.startsWith("1.7") || ver.startsWith("1.8"));
}
removeCryptographyRestrictions()
在执行任何加密操作之前,只需从静态初始化程序等调用即可。
这JceS@R_301_1360@.isRestricted = false
就是直接使用256位密码所需的全部内容。但是,如果没有其他两项操作,Cipher.getMaxAllowedKeyLength()
仍将继续报告128个,而256位TLS密码套件将不起作用。
该代码可在Oracle Java 7和8上运行,并在不需要的Java 9和OpenJDK上自动跳过该过程。毕竟是一个丑陋的黑客,它可能无法在其他供应商的VM上运行。
它在Oracle Java 6上也不起作用,因为私有JCE类在那里被混淆了。但是,各个版本之间的混淆并不会改变,因此从技术上讲,仍然可以支持Java 6。
分享改善这个答案