feat(tdx-attest): Rewrite TDX attestation in pure Rust

Replace the C-based tdx-attest-sys with a pure Rust implementation:

- Implement TDX ioctl commands directly using libc
- Support ConfigFS quote generation (Linux 6.7+)
- Handle both glibc and musl ioctl request types
- Remove dependency on vendored Linux kernel headers
- Simplify API: get_quote now returns Result<Vec<u8>>

This eliminates all C code from tdx-attest, making it easier to build
for different libc targets (glibc, musl) without header compatibility
issues.

The implementation supports:
- get_quote() via ConfigFS TSM interface
- get_report() via /dev/tdx_guest ioctl
- extend_rtmr() via /dev/tdx_guest ioctl
- get_supported_att_key_ids() returns Intel TDQE UUID

Note: VSock and TDVMCALL quote methods are not implemented as ConfigFS
is the recommended approach for Linux 6.7+. They can be added later if
needed for older kernel support.

Author: kvinwang

Cargo.lock

@@ -13,7 +13,6 @@ license.workspace = true
 [dependencies]
 anyhow.workspace = true
 hex.workspace = true
-num_enum.workspace = true
 scale.workspace = true
 serde.workspace = true
 serde-human-bytes.workspace = true
@@ -23,9 +22,9 @@ fs-err.workspace = true
 serde_json = { workspace = true, features = ["alloc"] }
 sha2.workspace = true
 
-# Linux x86_64 with glibc or musl
+# Linux x86_64 - pure Rust implementation using libc for syscalls
 [target.'cfg(all(target_os = "linux", target_arch = "x86_64"))'.dependencies]
-tdx-attest-sys.workspace = true
+libc.workspace = true
 
 [dev-dependencies]
 insta.workspace = true

tdx-attest-sys/csrc/linux/ioctl.h

@@ -2,18 +2,17 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
-use cc_eventlog::TdxEventLog;
-use num_enum::FromPrimitive;
-use thiserror::Error;
+//! Dummy implementation for non-Linux/non-x86_64 platforms.
+//!
+//! All functions return `NotSupported` error.
 
-use crate::{TdxReport, TdxReportData, TdxUuid};
+use thiserror::Error;
 
-type Result<T> = std::result::Result<T, TdxAttestError>;
+use crate::{Result, TdxReport, TdxReportData, TdxUuid};
 
-#[repr(u32)]
-#[derive(Debug, Clone, Copy, PartialEq, Eq, FromPrimitive, Error)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Error)]
 pub enum TdxAttestError {
-    #[error("unexpected")]
+    #[error("unexpected error")]
     Unexpected,
     #[error("invalid parameter")]
     InvalidParameter,
@@ -29,32 +28,28 @@ pub enum TdxAttestError {
     NotSupported,
     #[error("quote failure")]
     QuoteFailure,
-    #[error("busy")]
+    #[error("device busy")]
     Busy,
     #[error("device failure")]
     DeviceFailure,
-    #[error("invalid rtmr index")]
+    #[error("invalid RTMR index")]
     InvalidRtmrIndex,
-    #[error("unsupported att key id")]
+    #[error("unsupported attestation key ID")]
     UnsupportedAttKeyId,
-    #[num_enum(catch_all)]
-    #[error("unknown error ({0})")]
-    UnknownError(u32),
 }
 
-pub fn extend_rtmr(_index: u32, _event_type: u32, _digest: [u8; 48]) -> Result<()> {
+pub fn get_quote(_report_data: &TdxReportData) -> Result<Vec<u8>> {
     Err(TdxAttestError::NotSupported)
 }
+
 pub fn get_report(_report_data: &TdxReportData) -> Result<TdxReport> {
     Err(TdxAttestError::NotSupported)
 }
-pub fn get_quote(
-    _report_data: &TdxReportData,
-    _att_key_id_list: Option<&[TdxUuid]>,
-) -> Result<(TdxUuid, Vec<u8>)> {
-    let _ = _report_data;
+
+pub fn extend_rtmr(_index: u32, _event_type: u32, _digest: [u8; 48]) -> Result<()> {
     Err(TdxAttestError::NotSupported)
 }
+
 pub fn get_supported_att_key_ids() -> Result<Vec<TdxUuid>> {
     Err(TdxAttestError::NotSupported)
 }