Verify TAs by athvu · Pull Request #1399 · microsoft/litebox

Angelina Vu (athvu) · 2026-09-21T17:12:57Z

Allow for TA signature verification. A verification key can be embedded through the LITEBOX_TA_VERIFY_KEY build variable.
Built-in TAs can either be unsigned .elf or signed .ta files. Dynamic TAs must be signed.

Praveen K Paladugu (praveen-pk) · 2026-09-23T20:47:52Z

Why make this a compile time feature: signed-ta-rsa? Why not determine the binary type dynamically, by checking the MAGIC value and take appropriate steps?

Praveen K Paladugu (praveen-pk) · 2026-09-23T21:04:50Z

        } else {
            let ta_bin = Self::rpc_get_ta_bin(ta_uuid)?;
-            if !self.store_ta_bin(ta_uuid, &ta_bin) {
+            if !self.store_ta_bin(ta_uuid, &ta_bin, TaSource::Dynamic) {


fyi, the place to store_ta_bin changed with the open Dynamic TA Support PR (#1213).

So, this should be revisited later

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Dynamic TAs must be signed and verified. Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

… is not given. Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

github-actions · 2026-09-30T07:01:48Z

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

Click for details

--- failure method_parameter_count_changed: pub method parameter count changed ---

Description:
A publicly-visible method now takes a different number of parameters, not counting the receiver (self) parameter.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#fn-change-arity
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/method_parameter_count_changed.ron

Failed in:
  litebox_shim_optee::OpteeShim::store_ta_bin takes 2 parameters in /home/runner/work/litebox/litebox/target/semver-checks/git-main/76da2f2c93619305727f9255644e6e055b5c1c7d/litebox_shim_optee/src/lib.rs:423, but now takes 3 parameters in /home/runner/work/litebox/litebox/litebox_shim_optee/src/lib.rs:476

Sangho Lee (sangho2)

Two things should be considered:

this PR is not yet wired with ta_signing_cert, ta_svn, ta_digest, and ta_dynamic. ta_dynamic is still debatable because it is related to not only this PR but also #1213. However, the former three should be wired here.
It doesn't have an end-to-end test. We can implement one using litebox_runner_optee_on_linux_userland, which sign_encrypt.py one of the example TAs using a randomly generated RSA key pair and checks whether the userland runner can verify/run it.

Sangho Lee (sangho2) · 2026-09-30T15:33:41Z

+const SHDR_VERSION_LEN: usize = 4;
+
+/// An RSA public key used to verify signed `.ta` files
+pub struct TaVerifyKey(rsa::RsaPublicKey);


All these implementations (TaVerifyKey, parse_and_verify_ta, ...) should be moved to litebox_shim_optee. We are trying to avoid having actual implementation in common crates. This would also allow us to revert the changes in ci.yml and Cargo.toml.

Sangho Lee (sangho2) · 2026-09-30T15:43:18Z

+pub fn parse_and_verify_ta<'a>(
+    ta_data: &'a [u8],
+    verify_key: &TaVerifyKey,
+) -> Result<(TaHead, &'a [u8]), &'static str> {


nits: using thiserror should be better. returning error strings is a bit fragile.

Sangho Lee (sangho2) · 2026-09-30T15:49:18Z

+    signed_message.extend_from_slice(uuid_and_version);
+    signed_message.extend_from_slice(img);
+    verify_shdr_signature(&signed_message, sig, shdr.algo, &verify_key.0)?;
+    let ta_head = parse_ta_head(img).ok_or("Invalid TA ELF binary")?;


We should check whether UUIDs in uuid_and_version and ta_head are equal.

Sangho Lee (sangho2) · 2026-09-30T15:51:01Z

+    verify_shdr_signature(&signed_message, sig, shdr.algo, &verify_key.0)?;
+    let ta_head = parse_ta_head(img).ok_or("Invalid TA ELF binary")?;
+
+    Ok((ta_head, img))


We should return version as well because a raw TA image doesn't contain version info. assign it to ta_svn.

Sangho Lee (sangho2) · 2026-09-30T15:54:27Z

+    }
+    let hash_size = shdr.hash_size as usize;


nits: Better to check whether other fields (e.g., img_type) is valid and whether hash_size is correct (SHA256).

Sangho Lee (sangho2) · 2026-09-30T16:11:02Z

    /// UUID (from `.ta_head` section) doesn't match the provided UUID or parsing failed.
-    pub(crate) fn store_ta_bin(&self, ta_uuid: &TeeUuid, ta_bin: &[u8]) -> bool {
-        self.ta_uuid_map.insert(*ta_uuid, ta_bin.into())
+    pub(crate) fn store_ta_bin(&self, ta_uuid: &TeeUuid, ta_bin: &[u8], source: TaSource) -> bool {


nits: Rather than relying on the source argument, we could check ta_bin itself to identify whether it is signed or not.

Sangho Lee (sangho2) · 2026-09-30T16:17:10Z

    ta_signing_cert: &'static [u8],
+    ta_verify_key: &'static [u8],


These two are the same one.

Sangho Lee (sangho2) · 2026-09-30T16:19:05Z

+/// and from `optee_os/core/include/tee_api_types.h`
+/// ```c
+/// typedef struct {
+///     uint32_t timeLow;
+///     uint16_t timeMid;
+///     uint16_t timeHiAndVersion;
+///     uint8_t clockSeqAndNode[8];
+/// } TEE_UUID;


not needed. this UUID thing is already in the same file.

Sangho Lee (sangho2) · 2026-09-30T16:21:48Z

+    signature: &[u8],
+    algo: u32,
+    rsa_pub_key: &rsa::RsaPublicKey,
+) -> Result<(), &'static str> {


same. thiserror is preferred.

Sangho Lee (sangho2) · 2026-09-30T16:29:48Z

+    /// How the TA binary was loaded
+    source: TaSource,


take a look at ta_dynamic.

Sangho Lee (sangho2) · 2026-09-30T16:54:32Z

+    let end = img_offset
+        .checked_add(img_size)
+        .ok_or("Invalid signed TA file")?;
+    if end > ta_data.len() {


why not end != ta_data.len()? do we need to accept trailing bytes?

Angelina Vu (athvu) marked this pull request as draft September 21, 2026 17:43

Praveen K Paladugu (praveen-pk) assigned Praveen K Paladugu (praveen-pk) and unassigned Praveen K Paladugu (praveen-pk) Sep 23, 2026

Praveen K Paladugu (praveen-pk) reviewed Sep 23, 2026

View reviewed changes

Angelina Vu (athvu) force-pushed the avu/verify_ta branch from 06bc0ae to 27170aa Compare September 27, 2026 00:48

Angelina Vu added 3 commits September 29, 2026 16:10

Verify OP-TEE TA.

093b11e

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Embed key

5e8a20a

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Distinguish between built-in and dynamic TAs.

3d2fc6c

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Angelina Vu (athvu) force-pushed the avu/verify_ta branch 2 times, most recently from b259c1e to 96b466b Compare September 29, 2026 17:04

Angelina Vu (athvu) marked this pull request as ready for review September 29, 2026 17:15

Angelina Vu added 4 commits September 30, 2026 06:05

Allow built-in TAs to be either raw .elf or signed .ta binaries.

33e4187

Dynamic TAs must be signed and verified. Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Remove signed-ta-rsa feature. Set a TA verify key placeholder, if one…

1103589

… is not given. Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Move TA_VERIFY_KEY_DER to litebox_runner_lvbs.

082ff29

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Fix cargo clippy and doc.

79c73cd

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Angelina Vu (athvu) force-pushed the avu/verify_ta branch from 96b466b to 1c4ac88 Compare September 30, 2026 06:49

Consolidate store_embedded_ta and store_ta_bin into one function.

01e58f5

Signed-off-by: Angelina Vu <angelinavu@microsoft.com>

Angelina Vu (athvu) force-pushed the avu/verify_ta branch from 1c4ac88 to 01e58f5 Compare September 30, 2026 06:50

Sangho Lee (sangho2) reviewed Sep 30, 2026

View reviewed changes

		ta_signing_cert: &'static [u8],
		ta_verify_key: &'static [u8],

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Angelina Vu (athvu) commented Sep 21, 2026 •

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