Add support for setting up platform root key for LVBS

dev_tests/src/ratchet.rs

@@ -37,7 +37,7 @@ fn ratchet_globals() -> Result<()> {
             ("litebox/", 9),
             ("litebox_platform_linux_kernel/", 6),
             ("litebox_platform_linux_userland/", 5),
-            ("litebox_platform_lvbs/", 23),
+            ("litebox_platform_lvbs/", 24),
             ("litebox_platform_multiplex/", 1),
             ("litebox_platform_windows_userland/", 8),
             ("litebox_runner_linux_userland/", 1),

litebox_platform_lvbs/src/host/lvbs_impl.rs

@@ -114,6 +114,27 @@ impl litebox::platform::CrngProvider for LvbsLinuxKernel {
     }
 }
 
+/// Length of the Platform Root Key in bytes.
+pub const PRK_LEN: usize = 32;
+
+static PRK_ONCE: spin::Once<[u8; PRK_LEN]> = spin::Once::new();
+
+/// Sets the Platform Root Key (PRK) for this platform.
+///
+/// This should be called once during platform initialization with a key derived
+/// from hardware or a boot nonce.
+///
+/// # Panics
+/// Panics if `key` length does not match `PRK_LEN`.
+pub fn set_platform_root_key(key: &[u8]) {
+    assert_eq!(key.len(), PRK_LEN, "Platform Root Key length mismatch");
+    PRK_ONCE.call_once(|| {
+        let mut prk = [0u8; PRK_LEN];
+        prk.copy_from_slice(key);
+        prk
+    });
+}
+
 pub struct HostLvbsInterface;
 
 impl HostLvbsInterface {}

litebox_platform_lvbs/src/host/mod.rs

@@ -8,6 +8,7 @@ pub mod lvbs_impl;
 pub mod per_cpu_variables;
 
 pub use lvbs_impl::LvbsLinuxKernel;
+pub use lvbs_impl::{PRK_LEN, set_platform_root_key};
 
 #[cfg(test)]
 pub mod mock;

litebox_platform_lvbs/src/mshv/error.rs

@@ -106,7 +106,7 @@ pub enum VsmError {
     OperationNotSupported(&'static str),
 
     // VTL0 Memory Copy Errors
-    #[error("failed to copy data to VTL0")]
+    #[error("failed to copy data from/to VTL0")]
     Vtl0CopyFailed,
 
     // Hypercall Errors
@@ -152,6 +152,9 @@ pub enum VsmError {
 
     #[error("symbol name contains invalid UTF-8")]
     SymbolNameInvalidUtf8,
+
+    #[error("root key is invalid")]
+    PlatformRootKeyInvalid,
 }
 
 impl From<VerificationError> for VsmError {
@@ -217,7 +220,8 @@ impl From<VsmError> for Errno {
             | VsmError::SymbolNameInvalidUtf8
             | VsmError::SymbolNameNoTerminator
             | VsmError::CertificateDerLengthInvalid { .. }
-            | VsmError::CertificateParseFailed => Errno::EINVAL,
+            | VsmError::CertificateParseFailed
+            | VsmError::PlatformRootKeyInvalid => Errno::EINVAL,
 
             // Signature verification failures delegate to VerificationError's Errno mapping
             VsmError::SignatureVerificationFailed(e) => Errno::from(e),

litebox_platform_lvbs/src/mshv/mod.rs

@@ -130,6 +130,9 @@ pub const VSM_VTL_CALL_FUNC_ID_KEXEC_VALIDATE: u32 = 0x1_ffea;
 pub const VSM_VTL_CALL_FUNC_ID_PATCH_TEXT: u32 = 0x1_ffeb;
 pub const VSM_VTL_CALL_FUNC_ID_ALLOCATE_RINGBUFFER_MEMORY: u32 = 0x1_ffec;
 
+// This VSM function ID for setting the platform root key is subject to change
+pub const VSM_VTL_CALL_FUNC_ID_SET_PLATFORM_ROOT_KEY: u32 = 0x1_ffed;
+
 // This VSM function ID for OP-TEE messages is subject to change
 pub const VSM_VTL_CALL_FUNC_ID_OPTEE_MESSAGE: u32 = 0x1_fff0;
 
@@ -152,6 +155,7 @@ pub enum VsmFunction {
     PatchText = VSM_VTL_CALL_FUNC_ID_PATCH_TEXT,
     OpteeMessage = VSM_VTL_CALL_FUNC_ID_OPTEE_MESSAGE,
     AllocateRingbufferMemory = VSM_VTL_CALL_FUNC_ID_ALLOCATE_RINGBUFFER_MEMORY,
+    SetPlatformRootKey = VSM_VTL_CALL_FUNC_ID_SET_PLATFORM_ROOT_KEY,
 }
 
 pub const MSR_EFER: u32 = 0xc000_0080;

litebox_platform_lvbs/src/mshv/vsm.rs

@@ -9,9 +9,11 @@ use crate::mshv::ringbuffer::set_ringbuffer;
 use crate::{
     debug_serial_println,
     host::{
+        PRK_LEN,
         bootparam::get_vtl1_memory_info,
         linux::{CpuMask, KEXEC_SEGMENT_MAX, Kimage},
         per_cpu_variables::with_per_cpu_variables,
+        set_platform_root_key,
     },
     mshv::{
         HV_REGISTER_CR_INTERCEPT_CONTROL, HV_REGISTER_CR_INTERCEPT_CR0_MASK,
@@ -916,6 +918,28 @@ fn mshv_vsm_allocate_ringbuffer_memory(phys_addr: u64, size: usize) -> Result<i6
     Ok(0)
 }
 
+/// This function sets the platform root key by copying key data from VTL0.
+///
+/// - `key_pa`: Physical address (VTL0) that the platform root key is stored at.
+///
+/// This function assumes that the caller stores key bytes in a single or
+/// contiguous physical memory page(s), whose length is equal to `PRK_LEN`.
+fn mshv_vsm_set_platform_root_key(key_pa: u64) -> Result<i64, VsmError> {
+    if crate::platform_low().vtl0_kernel_info.check_end_of_boot() {
+        return Err(VsmError::OperationAfterEndOfBoot("set platform root key"));
+    }
+
+    let key_pa = PhysAddr::try_new(key_pa).map_err(|_| VsmError::InvalidPhysicalAddress)?;
+
+    let mut keybuf = [0u8; PRK_LEN];
+    if unsafe { crate::platform_low().copy_slice_from_vtl0_phys(key_pa, &mut keybuf) } {
+        set_platform_root_key(&keybuf);
+        Ok(0)
+    } else {
+        Err(VsmError::Vtl0CopyFailed)
+    }
+}
+
 /// VSM function dispatcher
 pub fn vsm_dispatch(func_id: VsmFunction, params: &[u64]) -> i64 {
     let result: Result<i64, VsmError> = match func_id {
@@ -939,6 +963,7 @@ pub fn vsm_dispatch(func_id: VsmFunction, params: &[u64]) -> i64 {
             let size: usize = params[1].truncate();
             mshv_vsm_allocate_ringbuffer_memory(params[0], size)
         }
+        VsmFunction::SetPlatformRootKey => mshv_vsm_set_platform_root_key(params[0]),
         VsmFunction::OpteeMessage => Err(VsmError::OperationNotSupported("OP-TEE communication")),
     };
     match result {

litebox_shim_optee/src/syscalls/pta.rs

@@ -115,8 +115,6 @@ impl Task {
                     let output_addr: usize = output.0.truncate();
                     let output_ptr = UserMutPtr::<u8>::from_usize(output_addr);
 
-                    // TODO: checks whether output is within the secure memory
-
                     // TODO: derive a TA unique key using the hardware unique key (HUK), TA's UUID, and `extra_data`
                     litebox::log_println!(
                         self.global.platform,