protocols: Implement attestation protocol [WIP]

Implement the entire body of the attestation protocol with its two
calls, according to the SVSM spec.

This is still WIP because it still misses:
1. Call to openssl SHA-512 routine to build the report data
2. Actual call to hypervisor to get the attestation report

Signed-off-by: Dov Murik <[email protected]>

src/protocols/attestation.rs

@@ -0,0 +1,304 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright (C) 2023 IBM Corporation
+ *
+ * Authors: Dov Murik <[email protected]>
+ */
+
+use alloc::vec::Vec;
+use core::mem::size_of;
+use uuid::Uuid;
+use x86_64::structures::paging::mapper::MapToError;
+use x86_64::structures::paging::{PhysFrame, Size4KiB};
+use x86_64::PhysAddr;
+
+use crate::cpu::vmsa::Vmsa;
+use crate::mem::is_in_calling_area;
+use crate::mem::MapGuard;
+use crate::protocols::error_codes::*;
+use crate::PAGE_SIZE;
+
+use super::SERVICES;
+
+/// 0
+const SVSM_ATTEST_SERVICES: u32 = 0;
+/// 1
+const SVSM_ATTEST_SINGLE_SERVICE: u32 = 1;
+
+/// 0x8000_1000
+const SVSM_FAIL_SNP_ATTESTATION: u64 = 0x8000_1000;
+
+#[derive(Default, Debug)]
+struct AttestationResult {
+    code: u64,
+    services_manifest_size: u64,
+    certs_size: u64,
+    report_size: u64,
+}
+
+impl AttestationResult {
+    pub fn from_code(code: u64) -> Self {
+        Self {
+            code,
+            ..Default::default()
+        }
+    }
+}
+
+/// SVSM Spec Chapter 7 (Attestation): Table 11: Attest Services operation
+#[derive(Clone, Copy, Debug)]
+#[repr(C, packed)]
+struct AttestServicesRequest {
+    report_gpa: u64,
+    report_size: u32,
+    _reserved1: [u8; 4],
+    nonce_gpa: u64,
+    nonce_size: u16,
+    _reserved2: [u8; 6],
+    services_manifest_gpa: u64,
+    services_manifest_size: u32,
+    _reserved3: [u8; 4],
+    certs_gpa: u64,
+    certs_size: u32,
+    _reserved4: [u8; 4],
+}
+
+/// SVSM Spec Chapter 7 (Attestation): Table 13: Attest Single Service operation
+#[derive(Clone, Copy, Debug)]
+#[repr(C, packed)]
+struct AttestSingleServiceRequest {
+    base: AttestServicesRequest,
+    service_guid: [u8; 16],
+    manifest_version: u32,
+    _reserved5: [u8; 4],
+}
+
+fn add_nonce_to_buffer(
+    nonce_gpa: u64,
+    nonce_size: u16,
+    buf: &mut Vec<u8>,
+) -> Result<(), AttestationResult> {
+    let nonce_gpa: PhysAddr = PhysAddr::new(nonce_gpa);
+    verify_fits_in_one_page(nonce_gpa, nonce_size as usize)?;
+    let map: MapGuard = MapGuard::new_private(nonce_gpa, nonce_size as u64)
+        .map_err(|_| AttestationResult::from_code(SVSM_ERR_INVALID_PARAMETER))?;
+    let nonce: &[u8] = map.as_bytes();
+    buf.extend_from_slice(nonce);
+    Ok(())
+}
+
+fn fits_in_one_page(start_gpa: PhysAddr, size: usize) -> bool {
+    if size == 0 {
+        return false;
+    }
+    let end_gpa: PhysAddr = start_gpa + size - 1usize;
+    let start_frame: PhysFrame<Size4KiB> = PhysFrame::containing_address(start_gpa);
+    let end_frame: PhysFrame<Size4KiB> = PhysFrame::containing_address(end_gpa);
+    start_frame == end_frame
+}
+
+fn verify_fits_in_one_page(start_gpa: PhysAddr, size: usize) -> Result<(), AttestationResult> {
+    if fits_in_one_page(start_gpa, size) {
+        Ok(())
+    } else {
+        Err(AttestationResult::from_code(SVSM_ERR_INVALID_PARAMETER))
+    }
+}
+
+fn verify_aligned(gpa: PhysAddr, align: u64) -> Result<(), AttestationResult> {
+    if gpa.is_aligned(align) {
+        Ok(())
+    } else {
+        Err(AttestationResult::from_code(SVSM_ERR_INVALID_PARAMETER))
+    }
+}
+
+fn verify_page_aligned(gpa: PhysAddr) -> Result<(), AttestationResult> {
+    if gpa.is_aligned(PAGE_SIZE) {
+        Ok(())
+    } else {
+        Err(AttestationResult::from_code(SVSM_ERR_INVALID_ADDRESS))
+    }
+}
+
+/// Map `dest_len` bytes starting at `dest_gpa` and copy the entire
+/// content of `src` into that memory area. `dest_len` must be equal or
+/// greater than `src.len()`
+fn copy_to_caller(src: &[u8], dest_gpa: PhysAddr, dest_len: u32) -> Result<(), AttestationResult> {
+    assert!(dest_len as usize >= src.len());
+    let mut map: MapGuard = MapGuard::new_private(dest_gpa, dest_len as u64)
+        .map_err(|_| AttestationResult::from_code(SVSM_ERR_INVALID_PARAMETER))?;
+    let dest_buf: &mut [u8] = map.as_bytes_mut();
+    dest_buf[..src.len()].copy_from_slice(src);
+    Ok(())
+}
+
+fn get_snp_attestation_report(
+    report_data: &[u8; 64],
+) -> Result<(Vec<u8>, Vec<u8>), AttestationResult> {
+    // Dummy function until we have PSP support
+    let mut attestation_report: Vec<u8> = [0xddu8; 2000].to_vec();
+    // Simulate possible PSP error condition
+    if report_data[0] == 0xee {
+        return Err(AttestationResult::from_code(SVSM_FAIL_SNP_ATTESTATION));
+    }
+    attestation_report.extend_from_slice(report_data);
+    let certs: Vec<u8> = [0xccu8; 6000].to_vec();
+    Ok((attestation_report, certs))
+}
+
+fn build_services_manifest(service_guid: Option<Uuid>, manifest_version: Option<u32>) -> Vec<u8> {
+    SERVICES.lock().get_manifest(service_guid, manifest_version)
+}
+
+fn todo_sha_512(input: &[u8]) -> [u8; 64] {
+    // Hook this to OpenSSL sha512 digest
+    [input[0]; 64]
+}
+
+fn attest_services(
+    request: &AttestServicesRequest,
+    service_guid: Option<Uuid>,
+    manifest_version: Option<u32>,
+) -> Result<AttestationResult, AttestationResult> {
+    let report_gpa: PhysAddr = PhysAddr::new(request.report_gpa);
+    verify_page_aligned(report_gpa)?;
+
+    let services_manifest_gpa: PhysAddr = PhysAddr::new(request.services_manifest_gpa);
+    verify_page_aligned(services_manifest_gpa)?;
+
+    let certs_gpa: PhysAddr = PhysAddr::new(request.certs_gpa);
+    if request.certs_size > 0 {
+        verify_page_aligned(certs_gpa)?;
+    }
+
+    let services_manifest: Vec<u8> = build_services_manifest(service_guid, manifest_version);
+    let services_manifest_size: u64 = services_manifest.len() as u64;
+    if services_manifest.len() > request.services_manifest_size as usize {
+        return Err(AttestationResult {
+            code: SVSM_ERR_INVALID_PARAMETER,
+            services_manifest_size,
+            certs_size: 0,
+            report_size: 0,
+        });
+    }
+
+    let mut buffer_to_hash: Vec<u8> = Vec::new();
+    add_nonce_to_buffer(request.nonce_gpa, request.nonce_size, &mut buffer_to_hash)?;
+    buffer_to_hash.extend_from_slice(&services_manifest);
+    let report_data: [u8; 64] = todo_sha_512(&buffer_to_hash);
+
+    let (attestation_report, certs) = get_snp_attestation_report(&report_data)?;
+    let report_size: u64 = attestation_report.len() as u64;
+    let certs_size: u64 = certs.len() as u64;
+
+    if attestation_report.len() > request.report_size as usize {
+        return Err(AttestationResult {
+            code: SVSM_ERR_INVALID_PARAMETER,
+            services_manifest_size,
+            certs_size,
+            report_size,
+        });
+    }
+
+    copy_to_caller(&attestation_report, report_gpa, request.report_size)?;
+    copy_to_caller(
+        &services_manifest,
+        services_manifest_gpa,
+        request.services_manifest_size,
+    )?;
+
+    if request.certs_size > 0 {
+        if certs_size > request.certs_size as u64 {
+            return Err(AttestationResult {
+                code: SVSM_ERR_INVALID_PARAMETER,
+                services_manifest_size,
+                certs_size,
+                report_size,
+            });
+        }
+
+        copy_to_caller(&certs, certs_gpa, request.certs_size)?;
+    }
+
+    Ok(AttestationResult {
+        code: SVSM_SUCCESS,
+        services_manifest_size,
+        certs_size,
+        report_size,
+    })
+}
+
+fn map_request_area(
+    request_gpa: PhysAddr,
+    request_size: usize,
+) -> Result<MapGuard, AttestationResult> {
+    verify_aligned(request_gpa, 8)?;
+    verify_fits_in_one_page(request_gpa, request_size)?;
+
+    let map_res: Result<MapGuard, MapToError<_>>;
+    if is_in_calling_area(request_gpa) {
+        map_res = MapGuard::new_private_persistent(request_gpa, request_size as u64);
+    } else {
+        map_res = MapGuard::new_private(request_gpa, request_size as u64);
+    }
+    let request_map: MapGuard =
+        map_res.map_err(|_| AttestationResult::from_code(SVSM_ERR_INVALID_PARAMETER))?;
+    Ok(request_map)
+}
+
+fn handle_attest_services_request_inner(
+    request_gpa: PhysAddr,
+) -> Result<AttestationResult, AttestationResult> {
+    let request_map: MapGuard = map_request_area(request_gpa, size_of::<AttestServicesRequest>())?;
+    let request: &AttestServicesRequest = request_map.as_object();
+    attest_services(request, None, None)
+}
+
+unsafe fn handle_attest_services_request(vmsa: *mut Vmsa) {
+    let request_gpa: PhysAddr = PhysAddr::new((*vmsa).rcx());
+    let r: AttestationResult = match handle_attest_services_request_inner(request_gpa) {
+        Ok(r) => r,
+        Err(r) => r,
+    };
+    (*vmsa).set_rax(r.code);
+    (*vmsa).set_rcx(r.services_manifest_size);
+    (*vmsa).set_rdx(r.certs_size);
+    (*vmsa).set_r8(r.report_size);
+}
+
+fn handle_attest_single_services_request_inner(
+    request_gpa: PhysAddr,
+) -> Result<AttestationResult, AttestationResult> {
+    let request_map: MapGuard =
+        map_request_area(request_gpa, size_of::<AttestSingleServiceRequest>())?;
+    let request: &AttestSingleServiceRequest = request_map.as_object();
+    let base_request: &AttestServicesRequest = &request.base;
+    let service_guid: Uuid = Uuid::from_bytes_le(request.service_guid);
+    attest_services(
+        base_request,
+        Some(service_guid),
+        Some(request.manifest_version),
+    )
+}
+
+unsafe fn handle_attest_single_service_request(vmsa: *mut Vmsa) {
+    let request_gpa: PhysAddr = PhysAddr::new((*vmsa).rcx());
+    let r: AttestationResult = match handle_attest_single_services_request_inner(request_gpa) {
+        Ok(r) => r,
+        Err(r) => r,
+    };
+    (*vmsa).set_rax(r.code);
+    (*vmsa).set_rcx(r.services_manifest_size);
+    (*vmsa).set_rdx(r.certs_size);
+    (*vmsa).set_r8(r.report_size);
+}
+
+pub unsafe fn attestation_handle_request(callid: u32, vmsa: *mut Vmsa) {
+    match callid {
+        SVSM_ATTEST_SERVICES => handle_attest_services_request(vmsa),
+        SVSM_ATTEST_SINGLE_SERVICE => handle_attest_single_service_request(vmsa),
+
+        _ => (*vmsa).set_rax(SVSM_ERR_UNSUPPORTED_CALLID),
+    };
+}

src/protocols/mod.rs

@@ -5,13 +5,16 @@
  * Authors: Dov Murik <[email protected]>
  */
 
+/// Implementation of the attestation protocol (1)
+pub mod attestation;
 /// Implementation of the core protocol (0)
 pub mod core;
 /// Error codes returned from the SVSM calls
 pub mod error_codes;
 /// Services manifest table
 pub mod services_manifest;
 
+pub use crate::protocols::attestation::*;
 pub use crate::protocols::core::*;
 pub use crate::protocols::services_manifest::*;