[Proposal] Add code signing on Windows to the JDK build system

[Magnus Ihse Bursie]

On 2025-03-11 20:29, Frederic Thevenet wrote:

> Hi Magnus,
>
> As mentioned before, the core idea here is really just providing a 
> hook for a script to be invoked after the native linker has been called.
> So while thinking about making this more generic and not Windows 
> specific, it struck me that it might in fact be desirable to also drop 
> the "signing" notion from this altogether and instead consider it a 
> way to extend to the build system by plugging in custom scripts? And 
> maybe extend it with other strategically placed hooks?
>
> Do you think this is a direction worth exploring further? Or that the 
> original, more focused scope is preferable?

Hm, that is definitely an interesting take. I'm a big fan of 
"right-sizing" generalization; I think both too much and too little 
generalization is detrimental. My gut feeling right now is that we 
should keep this focused on what it is, a way to allow signing. It will 
make the functionality discoverable by other parties that would like to 
add their own signing script; a general "hook" system might not. But 
it's good to keep in mind in case any future, non-signing needs arise.

I was more thinking along the lines that the current macOS signing could 
be considered/rewritten in terms of a "signing hook", with the exception 
that we also ship a default implementation alongside in the build 
system. If we do that right, we could probably retrofit Oracle's 
internal macOS signing logic into the same framework, which would be 
nice. But then again, that is definitely feature creep wrt to your 
original request. So maybe we can come back and revisit that thought later.

/Magnus

>
> Thanks,
> Frederic
>
>
> On 07/03/2025 16:49, Magnus Ihse Bursie wrote:
>> Hi Frederic,
>>
>> I think your proposal makes sense, and as Erik says, the patch is 
>> very unobtrusive.
>>
>> I'm not at all sure if it is even possible, but if the signing logic 
>> for macOS and Windows can be sort of unified and made more abstract, 
>> that would certainly be a win.
>>
>> /Magnus
>>
>>
>> On 2025-02-26 20:46, Erik Joelsson wrote:
>>> On 2/26/25 10:40 AM, Frederic Thevenet wrote:
>>>> Hi Erik,
>>>>
>>>> Thanks for your comments.
>>>>
>>>> As a matter of fact, we at Red Hat also face similar constraints 
>>>> that prevent us from being able to sign the files on the machine 
>>>> that build them (and I suspect this is quite common-place).
>>>>
>>>> My initial idea to accommodate that is to have the jdk build invoke 
>>>> a user supplied script (via a --with configure argument) rather 
>>>> than having it call signtool directly, so as to provide a way for 
>>>> everyone to easily plug their specific configuration and logic (in 
>>>> our case, the script uploads the file to sign to the signing 
>>>> machine and download it once it is done, in a synchronous fashion).
>>>>
>>>> In effect, it's just a hook that is invoked after the native linker 
>>>> has been called.
>>>>
>>>> I have created a PR[1] where you can see what I've done in details.
>>>
>>> That's a small and unintrusive solution. Our solution is a lot more 
>>> involved as I figured I wanted to expose a set of top level "phase" 
>>> targets for signing for each module, so that building libs or 
>>> launchers can be done independently from signing (e.g. 
>>> java.base-libs, java.base-launchers and java.base-sign). This 
>>> necessitates a separate set of output directories for signed libs 
>>> and signed launchers, where we first build like normal to the 
>>> regular output dirs and then the sign target copies and signs 
>>> binaries into the *-signed outputdirs, and when building jmods, we 
>>> need to pick up the files from those *-signed directories. It's 
>>> quite messy, so I've kept it all in our internal makefile 
>>> extensions. I'm also questioning the usefulness of this flexibility 
>>> given how much complexity it adds, so your proposal is probably 
>>> preferred.
>>>
>>> That said, I'm wondering if we could make it a bit more generic and 
>>> not define it as "windows" specific? Then perhaps bake in the macos 
>>> signing logic into this as well. The default implementation could be 
>>> using the native OS tools while there is a configure option to 
>>> completely replace it.
>>>
>>> /Erik
>>>
>>>>
>>>> Thanks,
>>>> Frederic
>>>>
>>>> [1] https://github.com/openjdk/jdk/pull/23807
>>>>
>>>> On 26/02/2025 15:29, Erik Joelsson wrote:
>>>>> Hello,
>>>>>
>>>>> I think this is a reasonable idea and you are welcome to implement 
>>>>> it. At Oracle we have been solving this using custom extension 
>>>>> makefiles. That will unfortunately not change with this proposal 
>>>>> as our signing process does not involve direct access to the 
>>>>> native tools of the OS. Perhaps this implementation could be made 
>>>>> plug-able enough so that we could leverage it, I'm not sure. What 
>>>>> I'm trying to say is that we are not against this, but we are also 
>>>>> not inclined to invest resources into it.
>>>>>
>>>>> /Erik
>>>>>
>>>>> On 2/26/25 12:52 AM, Frederic Thevenet wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I would like to start a discussion about adding built-in support 
>>>>>> for code signing native executable file and dynamic library on 
>>>>>> Windows directly as part of the JDK build, in a similar fashion 
>>>>>> to what already exists for macOS.
>>>>>>
>>>>>> Most, if not all vendors already ensure that every native 
>>>>>> executable files and dynamic libraries that are part of the 
>>>>>> binary builds of OpenJDK that they distribute to their customers 
>>>>>> for the Windows platform are digitally signed using a set of 
>>>>>> Microsoft APIs and tools called Authenticode[1].
>>>>>>
>>>>>> Since this is not a part of the existing JDK build system, 
>>>>>> however, this means that each vendor has had to come up with 
>>>>>> their own way to integrate the code signing step into their build 
>>>>>> pipeline.
>>>>>> As the shape of the JDK binary deliverable evolved to accommodate 
>>>>>> features like modules, signing binaries as an after-the-fact 
>>>>>> process has gradually become more complicated and error prone.
>>>>>>
>>>>>> For instance, with the introduction of JEP 493 (Linking Run-Time 
>>>>>> Images without JMODs)[2], adding a digital signature to files 
>>>>>> after jlink runs as part of the build to create the JDK image 
>>>>>> when the new '--generate-linkable-runtime' feature is enabled 
>>>>>> will cause any subsequent uses of jlink from this image to fail 
>>>>>> with a "Error:<xxxx> has been modified" error.
>>>>>>
>>>>>> The solution to that particular problem is to ensure that the 
>>>>>> signature is applied before jlink generates the checksums it will 
>>>>>> later use to detect , and I believe the best way to achieve that 
>>>>>> is to integrate code signing as an option in the jdk build process.
>>>>>>
>>>>>> This would also offer vendors who decide to opt into using this 
>>>>>> new feature to potentially simplify their overall build process.
>>>>>> For instance, this could get rid of extra steps such as filtering 
>>>>>> out dlls that are part of the bundle but were not built as part 
>>>>>> of the jdk (e.g. the Microsoft C and C++ runtime 
>>>>>> redistributables), or making sure that 'exe' and 'dll' files 
>>>>>> packaged in the .jmod files are also signed.
>>>>>>
>>>>>> As a stated before a very similar option already exists for code 
>>>>>> signing on the macOS platform, which further reinforce my 
>>>>>> thinking that such a feature would make sense for Windows as well.
>>>>>>
>>>>>> I have drafted a prototype for this and would be happy to create 
>>>>>> JBS issue and submit a PR to move this forward, provided there is 
>>>>>> interest.
>>>>>>
>>>>>> Thanks,
>>>>>> Frederic Thevenet (fthevenet)
>>>>>>
>>>>>> [1] 
>>>>>> https://learn.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/ms537359(v=vs.85)
>>>>>> [2] https://openjdk.org/jeps/493
>>>>>>
>>>>>
>>>>
>>
>