SQL Output Binding to Binary column fails when "/" character is in the BASE64 String

[timbrownai]

• Azure Functions SQL Extension or Extension Bundle Version:
  Azure Functions Core Tools
  Core Tools Version: 4.0.7030 Commit hash: N/A +bb4c949899cd5659d6bfe8b92cc923453a2e8f88 (64-bit)
  Function Runtime Version: 4.1037.0.23568
• Is this a deployed or local function: Local and Deployed
• What type of Database are you using? Microsoft SQL Azure (RTM) - 12.0.2000.8 Apr 9 2025 07:13:50 Copyright (C) 2024 Microsoft Corporation 5

Steps to Reproduce:

1. CREATE TABLE BinaryData (BinaryColumn binary(8))
2. Attempt to send the following JSON string to the output binding for the above table: '{"BinaryColumn":"//////////8="}'
3. This should result in the binary value 0xFFFFFFFFFFFFFFFF being inserted into the table. Instead an error is returned:

Base64 encoded string cannot be converted to binary value. Binary data would be truncated.

This only occurs when a "/" character exists in the BASE64 string. This is because the output binding framework tries to run the following command, escaping "/" characters in the whole JSON object.

SELECT * FROM OPENJSON(REPLACE(@rowData, N'/', N'\/')) WITH ([BinaryColumn] binary(8))

Manually running the above SQL, but doubling the length to binary(16) avoids the error.

[MaddyDev]

@timbrownai Decoding the '{"BinaryColumn":"//////////8="}' to binary returns 12 bytes => which is why Sql is returning the error:
Base64 encoded string cannot be converted to binary value. Binary data would be truncated. Could you please provide me the data you're trying to insert to repro. Thanks!

[timbrownai]

@MaddyDev we are expecting to insert value 0xFFFFFFFFFFFFFFFF - an 8 byte binary. That encodes to //////////8= in BASE64.

I believe the issue is at SqlAsyncCollector.cs#L416, where the REPLACE function is adding characters to the JSON.

I can force the error solely in SQL Server:

DECLARE @rowData nvarchar(50) =  N'{"BinaryColumn":"//////////8="}'
SELECT * FROM OPENJSON(@rowData) WITH ([BinaryColumn] binary(8))

succeeds, while

DECLARE @rowData nvarchar(50) =  N'{"BinaryColumn":"//////////8="}
SELECT * FROM OPENJSON(REPLACE(@rowData, N'/', N'\/')) WITH ([BinaryColumn] binary(8))`

fails.

There probably needs to be more context-sensitive escaping of the JSON string.