wolftpm

Safe Rust bindings to wolfTPM, a portable TPM 2.0 library from wolfSSL.

Why

A Trusted Platform Module (TPM 2.0) is a hardware security chip present in most modern PCs, servers, and embedded systems. wolfTPM is a compact, portable C implementation of the TPM 2.0 client stack that works with hardware TPMs (Linux kernel driver or SPI), the swtpm software TPM, the IBM TPM2 simulator, and bare-metal microcontrollers.

• Hardware-bound keys — RSA and ECC keys that never leave the chip
• Attestation — cryptographic proof of platform state via PCR quotes
• Sealing — encrypting data to a specific measured boot state
• Random number generation — hardware entropy source
• NV storage — small amounts of tamper-evident persistent storage
• Small footprint — wolfTPM depends only on wolfSSL for crypto and is much lighter than the tpm2-tss reference stack (no DBUS, JSON, or OpenSSL dependencies); suitable for embedded and bare-metal targets
• Idiomatic Rust — RAII cleanup of WOLFTPM2_DEV, transient-key lifetimes expressed in the type system, typed Error variants for TPM return codes, and explicit Send analysis

Usage

[dependencies]
wolftpm = "0.2"

use wolftpm::Device;

let mut dev = Device::open()?;                // /dev/tpm0 or /dev/tpmrm0

// Hardware random bytes
let random = dev.get_random(32)?;

// Read a PCR (SHA-256 bank, index 0)
let pcr: [u8; 32] = dev.pcr_read(0)?;

// Transient ECC P-256 signing key — flushed when the closure returns
dev.with_ecc_key(|key| {
    let sig = key.sign(&message_hash)?;       // SHA-256 digest in
    key.verify(&message_hash, &sig)?;
    Ok(())
})?;

Device::open() is always available. Device::open_swtpm(host, port) requires the swtpm feature. Build prerequisites (wolfTPM source and wolfSSL headers) are documented in wolftpm-src.

How it works

wolftpm-src     Compiles wolfTPM C source via the cc crate; generates
│               wolftpm/options.h; emits DEP_WOLFTPM_SRC_{INCLUDE,LIB}
│
wolftpm-sys     bindgen-generated FFI bindings; links libwolftpm.a and
│               libwolfssl
│
wolftpm         Safe high-level Rust API  ← this crate

Device wraps a heap-allocated WOLFTPM2_DEV and runs wolfTPM2_Cleanup on drop. EccKey<'dev> borrows the device for the lifetime of a transient P-256 signing key and unloads both the signing key and its storage root key when dropped — even on panic. TPM return codes are mapped to typed [Error] variants; TpmRc decodes the standard TPM2 result-code layers.

Transport selection happens in wolftpm-src at compile time. On Linux with no feature selected, WOLFTPM_LINUX_DEV is the default so that Device::open() works out of the box.

The wolfSSL key-import/export helpers (wolfTPM2_RsaKey_To_Device etc.) are compiled out for now (-DWOLFTPM2_NO_WOLFCRYPT). Advanced wolfTPM features (NV storage, attestation, HMAC sessions) are not yet wrapped; the wolftpm-sys raw bindings cover the full C API.

References

• wolftpm-sys — raw FFI bindings (use these for APIs not yet wrapped here)
• wolftpm-src — vendored wolfTPM source build
• wolftpm-tss — wolfTPM as a backend for the tpm-rs TSS ecosystem
• wolfTPM repository
• wolfTPM documentation
• wolfTPM API reference
• TCG TPM2 Library Specification
• workspace README

Copyright

Copyright (C) 2006-2026 wolfSSL Inc.

wolfTPM is copyright wolfSSL Inc. and its contributors.

License

GPL-3.0-only OR LicenseRef-wolfSSL-commercial.

The underlying wolfTPM C library is licensed under GPL-3.0-or-later with a commercial option available from wolfSSL Inc.