osslsigncode is a small tool that implements part of the functionality of Microsoft's signtool.exe --- more specifically, Authenticode signing and timestamping. But osslsigncode is based on OpenSSL and cURL, and thus should be able to compile and run on most platforms where these exist. osslsigncode supports:

• Signing and timestamp PE (EXE/SYS/DLL/etc), CAB, CAT, and MSI files
• Adding a valid signature to a CAB file containing Java file
• Getting the timestamp through a proxy
• Signature verification, removal, and extraction