From 9842f4bd25cc291c7b871a2b6342b8aeee4b13ca Mon Sep 17 00:00:00 2001
From: Esko Dijk <EskoDijk@users.noreply.github.com>
Date: Mon, 10 Nov 2025 17:54:19 -0500
Subject: [PATCH] [tcat] surface hash calculation internal errors to TCAT
 Commissioner (#12136)

Small change to surface any internal errors in the hash calculations
to the TCAT Commissioner as general error. If not done, such errors
are silently ignored and hard to diagnose in products.
---
 src/core/meshcop/tcat_agent.cpp | 19 ++++++++++---------
 src/core/meshcop/tcat_agent.hpp |  2 +-
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/core/meshcop/tcat_agent.cpp b/src/core/meshcop/tcat_agent.cpp
index bcc184530..3064d8b2c 100644
--- a/src/core/meshcop/tcat_agent.cpp
+++ b/src/core/meshcop/tcat_agent.cpp
@@ -907,8 +907,8 @@ Error TcatAgent::HandleRequestPskdHash(const Message &aIncomingMessage,
 
     SuccessOrExit(error = aIncomingMessage.Read(aOffset, &providedChallenge, aLength));
 
-    CalculateHash(providedChallenge, mVendorInfo->mPskdString, StringLength(mVendorInfo->mPskdString, kMaxPskdLength),
-                  hash);
+    SuccessOrExit(error = CalculateHash(providedChallenge, mVendorInfo->mPskdString,
+                                        StringLength(mVendorInfo->mPskdString, kMaxPskdLength), hash));
 
     SuccessOrExit(error = Tlv::AppendTlv(aOutgoingMessage, kTlvResponseWithPayload, hash.GetBytes(),
                                          Crypto::HmacSha256::Hash::kSize));
@@ -930,7 +930,7 @@ Error TcatAgent::VerifyHash(const Message &aIncomingMessage,
     VerifyOrExit(aLength == Crypto::HmacSha256::Hash::kSize, error = kErrorSecurity);
     VerifyOrExit(mRandomChallenge != 0, error = kErrorSecurity);
 
-    CalculateHash(mRandomChallenge, reinterpret_cast<const char *>(aBuf), aBufLen, hash);
+    SuccessOrExit(error = CalculateHash(mRandomChallenge, reinterpret_cast<const char *>(aBuf), aBufLen, hash));
     DumpDebg("Hash", &hash, sizeof(hash));
 
     VerifyOrExit(aIncomingMessage.Compare(aOffset, hash), error = kErrorSecurity);
@@ -939,18 +939,19 @@ exit:
     return error;
 }
 
-void TcatAgent::CalculateHash(uint64_t aChallenge, const char *aBuf, size_t aBufLen, Crypto::HmacSha256::Hash &aHash)
+Error TcatAgent::CalculateHash(uint64_t aChallenge, const char *aBuf, size_t aBufLen, Crypto::HmacSha256::Hash &aHash)
 {
     const mbedtls_asn1_buf &rawKey = Get<Ble::BleSecure>().GetOwnPublicKey();
     Crypto::Key             cryptoKey;
     Crypto::HmacSha256      hmac;
+    Error                   error = kErrorNone;
 
 #if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
     Crypto::Storage::KeyRef keyRef;
-    SuccessOrExit(Crypto::Storage::ImportKey(keyRef, Crypto::Storage::kKeyTypeHmac,
-                                             Crypto::Storage::kKeyAlgorithmHmacSha256, Crypto::Storage::kUsageSignHash,
-                                             Crypto::Storage::kTypeVolatile, reinterpret_cast<const uint8_t *>(aBuf),
-                                             aBufLen));
+    SuccessOrExit(error = Crypto::Storage::ImportKey(keyRef, Crypto::Storage::kKeyTypeHmac,
+                                                     Crypto::Storage::kKeyAlgorithmHmacSha256,
+                                                     Crypto::Storage::kUsageSignHash, Crypto::Storage::kTypeVolatile,
+                                                     reinterpret_cast<const uint8_t *>(aBuf), aBufLen));
     cryptoKey.SetAsKeyRef(keyRef);
 #else
     cryptoKey.Set(reinterpret_cast<const uint8_t *>(aBuf), static_cast<uint16_t>(aBufLen));
@@ -965,7 +966,7 @@ void TcatAgent::CalculateHash(uint64_t aChallenge, const char *aBuf, size_t aBuf
     Crypto::Storage::DestroyKey(keyRef);
 exit:
 #endif
-    return;
+    return error;
 }
 
 Error TcatAgent::HandleGetApplicationLayers(Message &aOutgoingMessage, bool &aResponse)
diff --git a/src/core/meshcop/tcat_agent.hpp b/src/core/meshcop/tcat_agent.hpp
index 4533f57f3..9734ef625 100644
--- a/src/core/meshcop/tcat_agent.hpp
+++ b/src/core/meshcop/tcat_agent.hpp
@@ -465,7 +465,7 @@ private:
                      uint16_t       aLength,
                      const void    *aBuf,
                      size_t         aBufLen);
-    void  CalculateHash(uint64_t aChallenge, const char *aBuf, size_t aBufLen, Crypto::HmacSha256::Hash &aHash);
+    Error CalculateHash(uint64_t aChallenge, const char *aBuf, size_t aBufLen, Crypto::HmacSha256::Hash &aHash);
 
     bool    CheckCommandClassAuthorizationFlags(CommandClassFlags aCommissionerCommandClassFlags,
                                                 CommandClassFlags aDeviceCommandClassFlags,