winExtDLL not loading

[janclod]

Last time writing down my problem lead me to a solution, so I will describe my new problem here and hope it will also get me closer to a solution :)

Goal: run NetSNMP agent v3 on Win10

Requirement 1: v3 with both authentication and encryption (e.g., SHA/AES)

Requirement 2: need to load extension of Windows agent written years ago by someone else

V5-9-patches scenario
I am able to fulfil requirements 1 by running my own build of the V5-9-patches branch. Using the V5-9-patches build I am not able to load the winExtDLL, this is the debug information:

registered debug token winExtDLL, 1
init_winExtDLL started.
winExtDLL: read_extension_dlls_from_registry called
init_winExtDLL: found 0 extension DLLs in the registry.
init_winExtDLL: registered 0 OID ranges.
init_winExtDLL finished.

Build information
Architecture: x86
OpenSSL: v3 32bit

v5.5.0 binary scenario
I am able to fulfil requirement 2 by running the binaries downloadable from sourceforge (v5.5.0 64-bit), but not requirements 1. As far as I understand it is not possible to install NetSNMP with encryption support from binary, please correct if I am wrong. So the first scenario is where I am looking for a solution.

Bug trace

init_winExtDLL started.
winExtDLL: read_extension_dlls_from_registry called
registry key SOFTWARE\mysoftware\CurrentVersion: DLL C:\Windows\System32\mysnmp.dll.
registry key Software\mysoftware\CurrentVersion: DLL C:\Windows\System32\mysnmp.dll.
init_winExtDLL: found 2 extension DLLs in the registry.
loading DLL C:\Windows\System32\mysnmp.dll.
loading DLL C:\Windows\System32\mysnmp.dll.
registering handler for DLL C:\Windows\System32\mysnmp.dll and OID prefix .1.3.6.1.4.1.XXXXX
registering handler for DLL C:\Windows\System32\mysnmp.dll and OID prefix .1.3.6.1.4.1.XXXXX
registering handler for DLL C:\Windows\System32\mysnmp.dll and OID prefix .1.3.6.1.4.1.XXXXXX
OID range .1.3.6.1.4.1.96788: replacing handler C:\Windows\System32\mysnmp.dll by C:\Windows\System32\mysnmp.dll.
init_winExtDLL: registered 4 OID ranges.
init_winExtDLL finished.

This is how my registry looks like:

Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\ExtensionAgents
Default REG_SZ                (value not set)
0           REG_SZ                Software\mysoftware\CurrentVersion
1           REG_SZ                SOFTWARE\mysoftware\CurrentVersion

Can you provide some guidance for scenario V5-9-patches? Should I try building from a different branch? Is this a bug (unlikely)?

[bvanassche]

winExtDLL can only load Windows SNMP DLLs after these have been installed. Is SNMP still supported by Windows 10? The following appears if I try to install SNMP in a Windows 10 VM:

$ Enable-WindowsOptionalFeature -online -FeatureName SNMP
Enable-WindowsOptionalFeature : Feature name SNMP is unknown.
At line:1 char:1
+ Enable-WindowsOptionalFeature -online -FeatureName SNMP
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Enable-WindowsOptionalFeature], COMException
    + FullyQualifiedErrorId : Microsoft.Dism.Commands.EnableWindowsOptionalFeatureCommand

[janclod]

Thank you Bart for your contribution :)

Windows 10 still offers the SNMP service, it is simply extra hidden. I did install the SNMP Win service following this strategy and the customized winExtDLL is registered.

I also dare to claim that the winExtDLL SNMP works based:

• on the output posted above, see v5.5.0 binary scenario
• on the fact that I am able to query the custom SNMP loaded from winExtDLLs

Based on some extra debugging, I found out that NetSNMP fails to open the Win registry (where the winExtDLL path is stored): SOFTWARE\mysoftware\CurrentVersion

EDIT: I made some progress, it seems that software (e.g., NetSNMP) is built using x86 environment. As far as I can understand x86 software can not access registry written by x64 software (e.g., my own software, SNMP Win service). I am now busy building the NetSNMP using x64 env and see if the issue is solved.

[janclod]

In my specific case, the mysnmp.dll was a 64-bit version. In the V5-9-patches scenario I was trying to load the 64-bit library (DLL) into a 32-bit process. This is not allowed.
https://docs.microsoft.com/en-us/windows/win32/winprog64/process-interoperability

SOLUTION: build NetSNMP agent using x64 environment

Specifications
NetSNMP: branch V5-9-patches
OpenSSL: Win64OpenSSL-3_0_0.exe
Build env: x64
winExtDLL: mysnmp.dll (64-bit version)