From 110115209af05babb068cc8b87970681582f9fa0 Mon Sep 17 00:00:00 2001
From: Vivien Nicolas <vnicolas@apple.com>
Date: Wed, 7 Dec 2022 17:02:17 +0100
Subject: [PATCH] [jsontlv] Add a prefix for octet strings encoded as base64
 (#23889)

---
 src/lib/support/jsontlv/TlvJson.cpp     | 12 ++++++++++--
 src/lib/support/tests/TestTlvToJson.cpp |  8 ++++----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/lib/support/jsontlv/TlvJson.cpp b/src/lib/support/jsontlv/TlvJson.cpp
index e7044da118f0b0..9b9bc3c25cdb55 100644
--- a/src/lib/support/jsontlv/TlvJson.cpp
+++ b/src/lib/support/jsontlv/TlvJson.cpp
@@ -67,6 +67,9 @@ struct KeyContext
 //
 static constexpr uint16_t kMaxStringLen = 1280;
 
+constexpr const char kBase64Header[] = "base64:";
+constexpr size_t kBase64HeaderLen    = ArraySize(kBase64Header) - 1;
+
 namespace chip {
 
 /*
@@ -152,10 +155,15 @@ CHIP_ERROR TlvToJson(TLV::TLVReader & reader, KeyContext context, Json::Value &
         VerifyOrReturnError(span.size() < kMaxStringLen, CHIP_ERROR_INVALID_TLV_ELEMENT);
 
         Platform::ScopedMemoryBuffer<char> byteString;
-        byteString.Alloc(BASE64_ENCODED_LEN(span.size()) + 1);
+        byteString.Alloc(kBase64HeaderLen + BASE64_ENCODED_LEN(span.size()) + 1);
         VerifyOrReturnError(byteString.Get() != nullptr, CHIP_ERROR_NO_MEMORY);
 
-        auto encodedLen              = Base64Encode(span.data(), span.size(), byteString.Get());
+        auto encodedLen = Base64Encode(span.data(), span.size(), byteString.Get() + kBase64HeaderLen);
+        if (encodedLen)
+        {
+            memcpy(byteString.Get(), kBase64Header, kBase64HeaderLen);
+            encodedLen += kBase64HeaderLen;
+        }
         byteString.Get()[encodedLen] = '\0';
 
         InsertKeyValue(parent, context, byteString.Get());
diff --git a/src/lib/support/tests/TestTlvToJson.cpp b/src/lib/support/tests/TestTlvToJson.cpp
index 07e06ca108782b..f2a777a7258716 100644
--- a/src/lib/support/tests/TestTlvToJson.cpp
+++ b/src/lib/support/tests/TestTlvToJson.cpp
@@ -147,7 +147,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
     ByteSpan byteSpan(byteBuf);
     EncodeAndValidate(byteSpan,
                       "{\n"
-                      "   \"value\" : \"AQIDBP/+mYjdzQ==\"\n"
+                      "   \"value\" : \"base64:AQIDBP/+mYjdzQ==\"\n"
                       "}\n");
 
     DataModel::Nullable<uint8_t> nullValue;
@@ -170,7 +170,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
                       "      \"0\" : 20,\n"
                       "      \"1\" : true,\n"
                       "      \"2\" : 0,\n"
-                      "      \"3\" : \"AQIDBP/+mYjdzQ==\",\n"
+                      "      \"3\" : \"base64:AQIDBP/+mYjdzQ==\",\n"
                       "      \"4\" : \"hello\",\n"
                       "      \"5\" : 0,\n"
                       "      \"6\" : 1.0,\n"
@@ -200,7 +200,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
                       "         \"0\" : 20,\n"
                       "         \"1\" : true,\n"
                       "         \"2\" : 0,\n"
-                      "         \"3\" : \"AQIDBP/+mYjdzQ==\",\n"
+                      "         \"3\" : \"base64:AQIDBP/+mYjdzQ==\",\n"
                       "         \"4\" : \"hello\",\n"
                       "         \"5\" : 0,\n"
                       "         \"6\" : 1.0,\n"
@@ -210,7 +210,7 @@ void TestConverter(nlTestSuite * inSuite, void * inContext)
                       "         \"0\" : 20,\n"
                       "         \"1\" : true,\n"
                       "         \"2\" : 0,\n"
-                      "         \"3\" : \"AQIDBP/+mYjdzQ==\",\n"
+                      "         \"3\" : \"base64:AQIDBP/+mYjdzQ==\",\n"
                       "         \"4\" : \"hello\",\n"
                       "         \"5\" : 0,\n"
                       "         \"6\" : 1.0,\n"