Here you'll find solutions for common problems during OpenSSL build.

Symptom:

fatal error C1083: Cannot open include file: 'stdlib.h': No such file or directory

Cause: Windows SDK not installed or not in PATH.

Solution:

# Option 1: Install Windows SDK
winget install Microsoft.WindowsSDK.10.0.22621
 
# Option 2: In Visual Studio Installer
# → "Individual Components" → select "Windows 10 SDK"

Then: Reload Visual Studio environment:

call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"

Symptom:

'perl' is not recognized as an internal or external command

Cause: Perl not installed or not in PATH.

Solution:

# Install Perl
winget install StrawberryPerl.StrawberryPerl
 
# Set PATH manually (if still not found after restart)
set PATH=C:\Strawberry\perl\bin;%PATH%

Symptom:

NASM not found - please read INSTALL.md

Cause: NASM not installed or not in PATH.

Solution A: Install NASM (recommended)

winget install NASM.NASM
 
# Set PATH (path may vary!)
set PATH=%LOCALAPPDATA%\bin\NASM;%PATH%
 
# Verify
nasm -v

Solution B: Build without NASM (slower)

perl Configure VC-WIN64A no-asm --prefix=D:\Projects\openssl-3.6.0\bin

Symptom:

'cl' is not recognized as an internal or external command

Cause: Visual Studio environment not loaded.

Solution:

call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"

Symptom: nmake clean doesn't respond or exits with error.

Cause: Known issue with previous failed builds.

Solution:

# Delete makefile manually
del makefile
 
# Reconfigure
perl Configure VC-WIN64A --prefix=D:\Projects\openssl-3.6.0\bin
 
# Rebuild
nmake

Symptom:

LINK : fatal error LNK1181: cannot open input file 'crypto\aes\aes-x86_64.obj'

Cause: Previous build failed, object files missing.

Solution:

# Delete everything and restart
del makefile
nmake clean 2>nul
perl Configure VC-WIN64A --prefix=D:\Projects\openssl-3.6.0\bin
nmake

Symptom: PowerShell script aborts even though cl.exe works.

Cause: cl.exe writes version info to stderr, which is interpreted as error with $ErrorActionPreference = „Stop“.

Solution in script:

# Handle cl.exe output correctly
try {
    $clOutput = & cl 2>&1 | Out-String
    Write-Host "cl.exe found"
} catch {
    Write-Host "cl.exe found (stderr ignored)"
}

Symptom:

File D:\...\build_openssl.ps1 cannot be loaded because running scripts is disabled

Solution:

# Option 1: Allow for this session
Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass
 
# Option 2: Bypass when calling
powershell.exe -ExecutionPolicy Bypass -File "build_openssl.ps1"

Symptom:

The program can't start because libcrypto-3-x64.dll is missing

Solution:

1. Copy DLLs to application folder:

copy D:\Projects\openssl-3.6.0\bin\bin\libcrypto-3-x64.dll .\
copy D:\Projects\openssl-3.6.0\bin\bin\libssl-3-x64.dll .\

2. Or copy automatically in .csproj:

<ItemGroup>
  <None Update="libcrypto-3-x64.dll">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </None>
  <None Update="libssl-3-x64.dll">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </None>
</ItemGroup>

Symptom:

openssl list -signature-algorithms | findstr mldsa
# No output

Possible causes:

1. Wrong OpenSSL version - Requires 3.6.0 or newer

openssl version
# Must be: OpenSSL 3.6.0 or higher

2. Provider not loaded

openssl list -providers
# Should show "default" and possibly "oqsprovider"

Symptom:

openssl list -providers
# Shows no "fips"

Solution:

1. Was it built with enable-fips?

perl Configure VC-WIN64A enable-fips --prefix=...
nmake
nmake install_sw install_fips

2. Is openssl.cnf correctly configured?

# In openssl.cnf:
[openssl_init]
providers = provider_sect
 
[provider_sect]
fips = fips_sect
base = base_sect
 
[fips_sect]
activate = 1
 
[base_sect]
activate = 1

Symptom: Timeout or connection error during git clone.

Solution for corporate proxy:

# Configure proxy
git config --global http.proxy http://proxy.company.com:8080
git config --global https.proxy http://proxy.company.com:8080

Solution for SSL certificate errors:

# Temporarily disable SSL verification (only for download!)
git config --global http.sslVerify false
 
# Re-enable after download
git config --global http.sslVerify true

If your problem is not listed here:

• OpenSSL Windows Notes
• OpenSSL GitHub Issues
• StackOverflow OpenSSL

Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional