RFE Review : JDK-5016517 - Replace plaintext passwords by hashed passwords for out-of-the-box JMX Agent

Daniel Fuchs daniel.fuchs at oracle.com
Wed Oct 11 09:00:45 UTC 2017 

Hi Harsha,

Your changes look good. However I have still a nagging doubt:

What happens if two Java process share the same password file,
and it needs hashing? Are there any protection in place
to prevent the two processes from writing to the same
file concurrently?

best regards,

-- daniel

On 09/10/2017 06:34, Harsha Wardhana B wrote:
> Hi Daniel,
> 
> Below is the webrev addressing the review comments.
> 
> http://cr.openjdk.java.net/~hb/5016517/webrev.04/
> 
> On Friday 06 October 2017 03:38 PM, Daniel Fuchs wrote:
>> Hi Harsha,
>>
>> Good work!
>>
>> > http://cr.openjdk.java.net/~hb/5016517/webrev.03/
>>
>> long standing typo in management.properties at line 90:
>>
>>   measureRole => monitorRole
> Done.
>>
>> HashedPasswordManager.java: loadPasswords()
>>
>> It seems this function will add the header to the file even
>> if it already contains the header.
>>
>> So every time a user/administrator wants to change/add a password,
>> the header will be inserted again.
>>
> Yes. It is fixed in the new webrev.
>>
>> HashedPasswordFileTest should probably have a test for this
>> scenario as well:
>>
>> generate password file with clear text password
>> load it, then verify passwords have been hashed (properly)
>> add some new user/name password to the same file
>> load it again, verify all passwords are hashed
>> (do this a number of times - to make sure it doesn't
>>  break the second or third time)
>> and finally verify the header is only present once ;-)
>>
> Done. Added a testcase for the same.
>> I'm surprised no other tests had to be modified.
>> Is password hash disabled by default in the default agent?
>>
> Password hashing is enabled by default. But it is only the 
> implementation that is changed. The pluggable JAAS mechanism isolates 
> interfaces from implementation. So in theory, all tests should pass.
>> If not then you should try (locally) running jtreg
>> more than once over the default agent tests.
>> Just make sure running the same test twice doesn't
>> make the legacy tests that use password files failing the
>> second time when they discover that passwords have been
>> hashed under their feet (the client part of the test
>> might be reading the password file too to see which
>> password it should send to the agent).
>>
>> Otherwise I think it looks good to me - provided all
>> tests are passing!
>>
> Done. Had a few test failures but nothing related to this enhancement.
>> best regards,
>>
>> -- daniel
> Thanks
> Harsha
>>
>> On 06/10/2017 06:25, Harsha Wardhana B wrote:
>>> Hi All,
>>>
>>> Previously, for default agent, hashing of the passwords was done 
>>> during the agent boot-up (ConnectorBootstrap.java). That was an error 
>>> since login configuration could be different and is determined only 
>>> when a login attempt is made. It would be then pointless to hash the 
>>> password file. The fix for above and some off-list comments are 
>>> incorporated in webrev below.
>>>
>>> http://cr.openjdk.java.net/~hb/5016517/webrev.03/
>>>
>>> -Harsha
>>>
>>>
>>> On Wednesday 04 October 2017 01:53 PM, Harsha Wardhana B wrote:
>>>> Hi Roger,
>>>>
>>>> Below is the webrev incorporating changes suggested by you.
>>>>
>>>> http://cr.openjdk.java.net/~hb/5016517/webrev.02/
>>>>
>>>> -Harsha
>>>>
>>>> On Wednesday 04 October 2017 12:54 AM, Roger Riggs wrote:
>>>>> Hi Harsha,
>>>>>
>>>>> FileLoginModule.java:  104:  Add a period at the end of the the 
>>>>> sentence.
>>>>>
>>>>> JMXPluggableAuthenticator.java: line 306:  Is the difference 
>>>>> between singular and plural significant?
>>>>>   It would be less confusing if both were plural (hashPasswords).
>>>> Ok.
>>>>> ConnectorBootstrap:
>>>>> 134: ...password.file.hash" and HashedPasswordManager disagree on 
>>>>> the exact string.
>>>>> I would propose 'hashpasswords' as the suffix in all places to be 
>>>>> consistent
>>>>> in ConnectorBootstrap.java, HashedPasswordManager (except for 
>>>>> capitalization),
>>>>> jmxremote.password.template, and management.properties
>>>> Do you want to rename HashedPasswordManager class?
>>>>>
>>>>> As is you have a mix of "...password.hash", 
>>>>> "...password.file.hash", "...hashpassword";
>>>>> that's not good for knowing there is only one semantic.
>>>>>
>>>>> line 482:  " ," -> ", "  space after comma, not before
>>>>>
>>>> Will incorporate above comments.
>>>>> line: 771: is it intentional to discard the reference to the new 
>>>>> HashedPasswordManager?
>>>>> If the intention is only to use the side effect of loadPasswords, 
>>>>> then please
>>>>> create a static method in HashedPasswordManager for that purpose.
>>>>> (Even if just does the same code; it would be clear that's the 
>>>>> purpose).
>>>>> (It probably also implies that the password file will be read a 
>>>>> second time somewhere else in the initialization).
>>>> Static methods just to hash passwords can be created but 
>>>> HashedPasswordManager class will have to be re-factored since almost 
>>>> all methods are using instance variables. Not sure if we want 
>>>> instance methods and look-alike static methods side-by-side. 
>>>> Wouldn't that be more confusing than current implementation?
>>>>>
>>>>> line:770:  the string constant would be nicer as a final static 
>>>>> string somewhere.
>>>>>   "jmx.remote.x.password.file.hashpassword"
>>>> All of "jmx.remote.x.*" don't have static strings. They are used 'as 
>>>> is' all over the code to maintain isolation between pluggable login 
>>>> authenticator and JDK code.
>>>>>
>>>>> Roger
>>>>>
>>>>>
>>>> Harsha
>>>>>
>>>>> On 10/3/2017 3:47 PM, Harsha Wardhana B wrote:
>>>>>>
>>>>>> Hi Roger,>>> Thanks for the detailed review. Below is the webrev 
>>>>>> addressing all the review comments.
>>>>>>
>>>>>> http://cr.openjdk.java.net/~hb/5016517/webrev.01/
>>>>>>
>>>>>> -Harsha
>>>>>>
>>>>>>
>>>>>> On Tuesday 25 April 2017 10:56 PM, Roger Riggs wrote:
>>>>>>> Hi Harsha,
>>>>>>>
>>>>>>> Thanks for this important improvement. Comments:
>>>>>>>
>>>>>>>
>>>>>>> * jmxremote.password.template:
>>>>>>>   "Passwords will be hashed by server if they are in clear." 
>>>>>>> Perhaps should be more explicit:
>>>>>>>
>>>>>>>    "The jmxremote.passwords file will be re-written by the server 
>>>>>>> to replace all plain text passwords with hashed passwords when 
>>>>>>> the file is read by the server."
>>>>>>>
>>>>>>> line 35: "Base64 encoded hash"  -> drop the "Base64" in this line 
>>>>>>> isn't needed and
>>>>>>> make it seems like it should appear as 1 field instead of 2 or 3.
>>>>>>>
>>>>>>> 37+: The syntax of the file may be clearer if it includes the 
>>>>>>> complete syntax in (line 39) not
>>>>>>> just the password/hash fragment.
>>>>>>>
>>>>>>> Line 41:  "W = spaces"; above "tabs" are allowed as a delimiter; 
>>>>>>> it would be good to be consistent
>>>>>>> and include the usualy white-space characters in the set, be as 
>>>>>>> specific as possible.
>>>>>>> Is this the same set of whitespace used by Regex '\\s'.
>>>>>> Only spaces and tabs are allowed. '\s' matches newline as well 
>>>>>> hence not allowed.
>>>>>>>
>>>>>>> 45: "java platform""  ->   "MD5, SDA-1, SHA-256 are supported 
>>>>>>> algorithms."
>>>>>>>
>>>>>>> 49: be more specific about 'hashing is requested'  how? Refer to 
>>>>>>> the management.properties
>>>>>>>   com.sun.management.jmxremote.password.hash value.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> 51:  "replace hashed" -> "replace *the *hashed"
>>>>>>> 52: "with clear text or new" -> "with the clear text or the new"
>>>>>>> 52: "If new password" -> "If the new password"
>>>>>>> 53: "when new login" -> "when a new login"
>>>>>>>
>>>>>>> 60: "User generated" -> "A User generated"
>>>>>>>
>>>>>>> 67: Will the file be ignored if it has the wrong permissions. 
>>>>>>> (With a logged message)
>>>>>> Addressed all the above review comments.
>>>>>>>
>>>>>>> * management.properties
>>>>>>>
>>>>>>> 306: "(Case for true/false ignored)"  - what does this mean; I 
>>>>>>> think it can be removed.
>>>>>>>
>>>>>>> 307: missing period at the end of the sentence.
>>>>>>> 309: "in password file" -> "in the password file"
>>>>>>>
>>>>>> Done.
>>>>>>>
>>>>>>> * FileLoginModule.java
>>>>>>>
>>>>>>> 102: can this match better the similar name in the 
>>>>>>> management.properties if it has the same function:
>>>>>>>     com.sun.management.jmxremote.password.hash
>>>>>> Are you suggesting that 'hashPassword' be renamed to something 
>>>>>> similar to com.sun.management.jmxremote.password.hash? Variable 
>>>>>> names cannot be similar to property names since property names are 
>>>>>> long and provide complete context which local variables need not 
>>>>>> have to do.
>>>>> the suffix should be the same in all places since it is a single 
>>>>> semantic.
>>>> Done.
>>>>>>> 103: "replaces clear text passwords" -> "replaces each clear text 
>>>>>>> password"
>>>>>>> 104: indent to match previous <dd> enteries.
>>>>>>>
>>>>>>> * JMXPluggableAuthenticator.java
>>>>>>>
>>>>>>> 119: There is no need to copy the password to a new local
>>>>>> It is required since variables accessed from inner class must be 
>>>>>> final or effectively final.
>>>>> right
>>>>>>>
>>>>>>> 128: add a space after ","
>>>>>>>
>>>>>>> 256 private static final String HASH_PASSWORDS =
>>>>>>> 257 "jmx.remote.x.password.file.hash";
>>>>>>>
>>>>>>> The name ".hash" part does not clearly communicate that passwords 
>>>>>>> are to be hashed.
>>>>>>> "hashPasswords" might be more self explanatory.
>>>>>> Changed it to "jmx.remote.x.password.file.hashpassword".
>>>>> drop the "file."
>>>> Done.
>>>>>>> Also, can this be NOT duplicated here and in 
>>>>>>> ConnectorBootStrap.java?
>>>>>> The property names used in ConnectorBootStrap follows the 
>>>>>> convention used in management.properties file - 
>>>>>> 'com.sun.management.*'. For environment variables for a 
>>>>>> JMXConnector "jmx.remote.x.*" convention is used . Hence they 
>>>>>> cannot be duplicated.
>>>>> The differing prefix'es are fine as is; no change except to make 
>>>>> the new keys consistent.
>>>>>
>>>>>>>
>>>>>>>
>>>>>>> * ConnectorBootStrap.java:
>>>>>>>  482: Add space after ","s; no spaces before.
>>>>>>>
>>>>>>> 770: use the same name for the option/property if possible to 
>>>>>>> avoid confusion.
>>>>>> Not possible as explained above.
>>>>>>>
>>>>>>> 770:  if the HASH_PASSWORDS static is appropriate use it instead 
>>>>>>> of literal "true".
>>>>>> DefaultValues.HASH_PASSWORDS static is set to 'true' and can be 
>>>>>> used. However using literal "true" is more readable than using the 
>>>>>> static.
>>>>>>>
>>>>>>> * HashedPasswordManager
>>>>>>>
>>>>>>> 80-83: The fields can be final and use the constructor to 
>>>>>>> initialize in all cases and make the class final
>>>>>>> to avoid unintentional subclassing.
>>>>>>>
>>>>>>>
>>>>>>> 113: canWriteToFile:   It should be made clear in the template 
>>>>>>> that *both* the Security policy
>>>>>>>    and the file access value are used to check that the file can 
>>>>>>> be updated.
>>>>>> Made it explicit in template as well as code comments.
>>>>>>>
>>>>>>> 200: loadPasswords() - should this confirm the access to the file 
>>>>>>> is allowed and it has
>>>>>>> the correct file access before reading?
>>>>>> Not really required. Appropriate exceptions are thrown if file 
>>>>>> cannot be accessed.
>>>>>>>
>>>>>>> Is the re-writing of the passwords intended to be done by a 
>>>>>>> 'priveleged' system.
>>>>>>> Does this need doPrivileged?
>>>>>> I am not sure. Maybe it will be covered in the security review.
>>>>>>>
>>>>>>> * HashedPasswordFileTest:
>>>>>>>
>>>>>>> 88: should use the TestLibrary Utils.getRandomInstance so it logs 
>>>>>>> the seed and can be replayed if necessary.
>>>>>>>
>>>>>>>
>>>>>> Done
>>>>>>> Thanks, Roger
>>>>>>>
>>>>>> Thanks
>>>>>> Harsha
>>>>>>>
>>>>>>> On 4/23/2017 6:20 AM, Harsha Wardhana B wrote:
>>>>>>>>
>>>>>>>> Hi All,
>>>>>>>>
>>>>>>>> Please review this enhancement to replace plain-text password 
>>>>>>>> for JMX agent with SHA-256 hash.
>>>>>>>>
>>>>>>>> Issue: https://bugs.openjdk.java.net/browse/JDK-5016517
>>>>>>>> <https://bugs.openjdk.java.net/browse/JDK-5016517>
>>>>>>>>
>>>>>>>> webrev: http://cr.openjdk.java.net/~hb/5016517/webrev.00/
>>>>>>>>
>>>>>>>> Overview of implementation:
>>>>>>>>
>>>>>>>> Currently, the JMX agent password file used to authenticate 
>>>>>>>> user, stores user name and password as clear text. Though system 
>>>>>>>> level restrictions are recommended for jmx password file, 
>>>>>>>> passwords are vulnerable since they are stored in clear. The 
>>>>>>>> current RFE proposes to store passwords as SHA256 hash instead 
>>>>>>>> of clear text.
>>>>>>>>
>>>>>>>> In current implementation, if password file is writable, and if 
>>>>>>>> passwords are in clear, they will be replaced by SHA256 hash 
>>>>>>>> upon agent boot-up or when login attempt is made.
>>>>>>>>
>>>>>>>> The file, 
>>>>>>>> src/jdk.management.agent/share/conf/jmxremote.password.template 
>>>>>>>> contains more details about the implementation.
>>>>>>>>
>>>>>>>> - Harsha
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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