Add Go Bindings for TPM 2.0 Reference Implementation

[josephlr]

Depends on #1, so we temporarily use backports as the base branch (to make the changes easier to see). Will switch back to main once #1 is merged.

This PR adds Go bindings to the C code, replacing the terrible hacks in https://github.com/google/go-tpm-tools/tree/main/simulator/internal.

As with the old solution, we compile the entire TPM reference code using Go's CGO build system. To maintain an explicit list of source files without copying their contents, we use wrapper C files that #include the original C files in the repository. This avoids issues with symlinks not being handled correctly by fetched Go modules.

The platform interface required by the TPM reference code is implemented in Go, providing flexibility via callbacks and interfaces (rather than using https://github.com/google/go-tpm-tools/tree/main/simulator/ms-tpm-20-ref/Samples/Google). For example, the Storage struct uses a fixed array of size C.NV_MEMORY_SIZE and supports optional callbacks for OnEnable, OnReady, and OnCommit.

The entire repository is now the Go module (github.com/google/TPM), which ensures that the C source files in TPMCmd are included when the module is fetched by GOPROXY.

Commit Breakdown

1. Add scaffolding for Go bindings

   • ./bindings/c/1build.go: to handle CGO compilation flags and define C wrapper functions.
   • ./bindings/README.md: instructions on building, testing, and publishing.
   • ./bindings/regenerate_c.py: automate the creation of wrapper C files.
   • ./go.mod: Must be at the repository root.

2. Run ./bindings/regenerate_c.py

   • Contains the 200+ wrapper C files that include the source files needed for the build, located in ./bindings/c/ and pointing directly to the files in ./TPMCmd.

3. Platform and Entrypoints code

   • ./bindings/go/platform/: implements the Go platform callbacks (storage, timer, system, act).
   • ./bindings/go/entrypoints/ : provides entrypoints for Manufacture, Init, and ExecuteCommand. Note that Manufacture takes no arguments and always forces manufacturing.

Verification

Build and run everything in this module from the repository root:

go build ./bindings/go/...
go test ./bindings/go/entrypoints/...

The bindings were verified by integrating them into go-tpm and running the full tpm2/test suite. All tests passed.