[WebGPU Plugin EP] implements signing verification

[prathikr]

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Project	Deployment	Actions	Updated (UTC)
foundry-local	Ready	Preview, Comment	Jun 17, 2026 8:31pm

[Copilot]

Pull request overview

This PR adds RSA-SHA256 signature verification for the WebGPU plugin EP manifest. Before using a fetched manifest to determine which WebGPU EP package to download, the code now fetches a corresponding .sig file from the CDN, decodes the base64 signature, and verifies it against a hardcoded RSA-4096 public key using OpenSSL. This prevents tampering with the manifest in transit or on the CDN.

Changes:

• Added VerifyRsaSha256Signature utility function in ep_utils.cc/h using OpenSSL's EVP_DigestVerify* API to verify RSA-SHA256-PKCS1v15 detached signatures.
• Integrated manifest signature verification into FetchManifest in webgpu_ep_bootstrapper.cc, embedding the RSA-4096 public key and fetching the .sig file alongside the manifest.
• Added OpenSSL as a build dependency (find_package + target_link_libraries) in CMakeLists.txt.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
sdk_v2/cpp/src/ep_detection/webgpu_ep_bootstrapper.cc	Adds public key constant, fetches .sig file, and calls signature verification before parsing the manifest. Currently points to dev URL (must be changed to prod).
sdk_v2/cpp/src/ep_detection/ep_utils.h	Declares VerifyRsaSha256Signature with documentation.
sdk_v2/cpp/src/ep_detection/ep_utils.cc	Implements RSA-SHA256 signature verification using OpenSSL BIO/EVP APIs.
sdk_v2/cpp/CMakeLists.txt	Adds find_package(OpenSSL CONFIG REQUIRED) and links OpenSSL::Crypto.