Migrate from deprecated OpenSSL SHA256_* APIs to EVP APIs (project-chip#36386)

* Migrate from deprecated OpenSSL SHA256_* APIs to EVP APIs

* Integrating comments

Author: Alami-Amine

src/crypto/CHIPCryptoPAL.h

@@ -942,6 +942,9 @@ class Hash_SHA256_stream
 
 private:
     HashSHA256OpaqueContext mContext;
+#if CHIP_CRYPTO_BORINGSSL || CHIP_CRYPTO_OPENSSL
+    bool mInitialized = false;
+#endif
 };
 
 class HKDF_sha

src/crypto/CHIPCryptoPALOpenSSL.cpp

@@ -433,71 +433,115 @@ CHIP_ERROR Hash_SHA1(const uint8_t * data, const size_t data_length, uint8_t * o
     return CHIP_NO_ERROR;
 }
 
-Hash_SHA256_stream::Hash_SHA256_stream() {}
+// For OpenSSL, we store a pointer to the digest context (EVP_MD_CTX) since EVP_MD_CTX is Opaque.
+static_assert(kMAX_Hash_SHA256_Context_Size >= sizeof(void *),
+              "kMAX_Hash_SHA256_Context_Size needs to at least be able to store a pointer");
 
-Hash_SHA256_stream::~Hash_SHA256_stream()
+// Storing a pointer to EVP_MD_CTX in HashSHA256OpaqueContext instead of the actual EVP_MD_CTX structure, as EVP_MD_CTX was made
+// opaque by OpenSSL and is dynamically allocated.
+static inline void set_inner_hash_evp_md_ctx(HashSHA256OpaqueContext * context, EVP_MD_CTX * evp_ctx)
 {
-    Clear();
+    *SafePointerCast<EVP_MD_CTX **>(context) = evp_ctx;
 }
 
-static_assert(kMAX_Hash_SHA256_Context_Size >= sizeof(SHA256_CTX),
-              "kMAX_Hash_SHA256_Context_Size is too small for the size of underlying SHA256_CTX");
+static inline EVP_MD_CTX * to_inner_hash_evp_md_ctx(HashSHA256OpaqueContext * context)
+{
+    return *SafePointerCast<EVP_MD_CTX **>(context);
+}
 
-static inline SHA256_CTX * to_inner_hash_sha256_context(HashSHA256OpaqueContext * context)
+Hash_SHA256_stream::Hash_SHA256_stream() : mInitialized(false)
 {
-    return SafePointerCast<SHA256_CTX *>(context);
+    set_inner_hash_evp_md_ctx(&mContext, nullptr);
+}
+
+Hash_SHA256_stream::~Hash_SHA256_stream()
+{
+    Clear();
 }
 
 CHIP_ERROR Hash_SHA256_stream::Begin()
 {
-    SHA256_CTX * const context = to_inner_hash_sha256_context(&mContext);
 
-    const int result = SHA256_Init(context);
+    EVP_MD_CTX * mdctx = EVP_MD_CTX_new();
+    VerifyOrReturnError(mdctx != nullptr, CHIP_ERROR_INTERNAL);
+
+    set_inner_hash_evp_md_ctx(&mContext, mdctx);
+
+    const int result = EVP_DigestInit_ex(mdctx, _digestForType(DigestType::SHA256), nullptr);
+
     VerifyOrReturnError(result == 1, CHIP_ERROR_INTERNAL);
+    mInitialized = true;
 
     return CHIP_NO_ERROR;
 }
 
 CHIP_ERROR Hash_SHA256_stream::AddData(const ByteSpan data)
 {
-    SHA256_CTX * const context = to_inner_hash_sha256_context(&mContext);
+    VerifyOrReturnError(mInitialized, CHIP_ERROR_UNINITIALIZED);
+
+    EVP_MD_CTX * mdctx = to_inner_hash_evp_md_ctx(&mContext);
+    VerifyOrReturnError(mdctx != nullptr, CHIP_ERROR_INTERNAL);
+
+    const int result = EVP_DigestUpdate(mdctx, data.data(), data.size());
 
-    const int result = SHA256_Update(context, Uint8::to_const_uchar(data.data()), data.size());
     VerifyOrReturnError(result == 1, CHIP_ERROR_INTERNAL);
 
     return CHIP_NO_ERROR;
 }
 
 CHIP_ERROR Hash_SHA256_stream::GetDigest(MutableByteSpan & out_buffer)
 {
-    SHA256_CTX * context = to_inner_hash_sha256_context(&mContext);
 
-    // Back-up context as we are about to finalize the hash to extract digest.
-    SHA256_CTX previous_ctx = *context;
+    VerifyOrReturnError(mInitialized, CHIP_ERROR_UNINITIALIZED);
+
+    EVP_MD_CTX * mdctx = to_inner_hash_evp_md_ctx(&mContext);
+
+    // Back-up the context as we are about to finalize the hash to extract digest.
+    EVP_MD_CTX * previous_mdctx = EVP_MD_CTX_new();
+    VerifyOrReturnError(previous_mdctx != nullptr, CHIP_ERROR_INTERNAL);
+    const int copy_result = EVP_MD_CTX_copy_ex(previous_mdctx, mdctx);
+    VerifyOrReturnError(copy_result == 1, CHIP_ERROR_INTERNAL);
 
     // Pad + compute digest, then finalize context. It is restored next line to continue.
     CHIP_ERROR result = Finish(out_buffer);
 
-    // Restore context prior to finalization.
-    *context = previous_ctx;
+    // free the finalized context.
+    EVP_MD_CTX_free(mdctx);
+
+    // Restore the backed up context, to be able to get intermediate digest again if needed
+    set_inner_hash_evp_md_ctx(&mContext, previous_mdctx);
 
     return result;
 }
 
 CHIP_ERROR Hash_SHA256_stream::Finish(MutableByteSpan & out_buffer)
 {
+    unsigned int size;
+
     VerifyOrReturnError(out_buffer.size() >= kSHA256_Hash_Length, CHIP_ERROR_BUFFER_TOO_SMALL);
+    VerifyOrReturnError(mInitialized, CHIP_ERROR_UNINITIALIZED);
+
+    EVP_MD_CTX * mdctx = to_inner_hash_evp_md_ctx(&mContext);
+
+    const int result = EVP_DigestFinal_ex(mdctx, out_buffer.data(), &size);
 
-    SHA256_CTX * const context = to_inner_hash_sha256_context(&mContext);
-    const int result           = SHA256_Final(Uint8::to_uchar(out_buffer.data()), context);
     VerifyOrReturnError(result == 1, CHIP_ERROR_INTERNAL);
+    VerifyOrReturnError(size == kSHA256_Hash_Length, CHIP_ERROR_INTERNAL);
+
     out_buffer = out_buffer.SubSpan(0, kSHA256_Hash_Length);
 
     return CHIP_NO_ERROR;
 }
 
 void Hash_SHA256_stream::Clear()
 {
+    EVP_MD_CTX * mdctx = to_inner_hash_evp_md_ctx(&mContext);
+
+    // EVP_MD_CTX_free does nothing if a nullptr is passed to it
+    EVP_MD_CTX_free(mdctx);
+    set_inner_hash_evp_md_ctx(&mContext, nullptr);
+
+    mInitialized = false;
     OPENSSL_cleanse(this, sizeof(*this));
 }
 
@@ -1405,6 +1449,8 @@ void Spake2p_P256_SHA256_HKDF_HMAC::Clear()
         BN_CTX_free(context->bn_ctx);
     }
 
+    sha256_hash_ctx.Clear();
+
     free_point(M);
     free_point(N);
     free_point(X);