Protobuf

How to decode your HTTP/HTTPS Request/Response Protobuf with Proxyman

1. Protobuf

• Proxyman macOS can decode your HTTP/HTTPS Request/Response Protobuf Body with a given Protobuf Desc file

• Decode Protobuf binary and show as plain text

• Support Single or Multiple Delimited Messages in a single Protobuf Binary

• Import a desc file and read all Message Type -> Useful to decode protobuf binary

• Decode Protobuf from Websocket

Parse protobuf request with File Descriptor

2. Protobuf File Descriptor (*.desc)

Proxyman requires a File Descriptor (*.desc) to properly parse the Protobuf Data.

There are various ways to get the File Descriptor:

1. Ask your colleagues.

If your company is using Protobuf, it's a high chance that your colleagues have already had this file, especially the Backend and Frontend teams.

It might be one or multiple descriptor files.

2. Generate from *.proto file

If you have a bunch of *.proto files, you can simply generate 1 single *.desc file by using the following command line.

# Install protobuf cli if need
brew install protobuf

# Create `input` folder on the Desktop
# Copy all proto files to the `input` folder

# Generate 1 descriptor file with multiple proto files
protoc --descriptor_set_out=output.desc --include_imports -I=/Users/<your_name>/Desktop/input /Users/<your_name>/Desktop/input/*.proto

# Done
# output.desc

Once you have the Descriptor File, you can import them to Proxyman:

• Proxyman -> Tools Menu -> Protobuf Schema

• Click on the + button and select the output.desc file

Proxyman 3.6.0+ only accepts File Descriptor (*.desc) for better Protobuf parsing.

If you have *.proto files, you can convert them to *.desc. Please check out the next section.

Proxyman automatically imports all common types from Google Protobuf, such as Timestamp, Struct, Value, Enum, Method, etc.

Proxyman supports both proto2 and proto3 syntax. Read more

3. Protobuf Config

Before using Protobuf, you have to configure which Message Type should be used to parse the Protobuf data.

The following table describes which configurations are:

Name	Description
Schema	Add .desc file if need
Message Type	The Class name of the root object in Protobuf binary. Must include Package name
Payload Type: Auto	Auto detect if the Protobuf Binary is encoding as a Single Message or Delimited Message
Payload Type: Single Message	Single Mesage in a Protobuf Binary
Payload Type: Delimited Message	Multiple Messages in a Protobuf Binary (Length-Prefix)

Decode Protobuf HTTPS Resposne with Proxyman

4. How to use?

There are two ways to parse Protobuf properly with qualified name fields:

• Define Protobuf Rules

• Read from Content-Type Header

4.1 Define Protobuf Rule

1. Your Protobuf Request should have a Content-Type header, which is Content-Type: application/x-protobuf or Content-Type: application/protobuf

2. Proxyman detects that it's a Protobuf Payload -> A Warning that Proxyman couldn't parse properly due to the absence of the message type. Click Add to open Protobuf Settings.

Alternatively, you can right-click on your Request -> Tools -> Protobuf

Missing Message Type

3. In the Protobuf Rule Window -> Select which Message Type for this request (Add Desc file if needed) for this Request/Response

If you have a different Protobuf Message Type for the Request and Response. Select the `Use different Message Type for Request/Response` checkbox

4. Click Add and see the JSON Format

4.2 Read from Content-Type Header

You can dynamically provide the Protobuf Config from Content-Type

For example: Your Content-Type in the Request or Response might look like:

Content-Type: application/x-protobuf; messageType="tutorial.Address"; delimited=true

Content-Type: application/x-protobuf; messageType="com.proxyman.User"; delimited=false

To specify that the Protobuf Body this MessageType and the payload encoding.

5. ✅ Protobuf With Websocket (from macOS 6.5.0 or later)

• Decode a single binary web socket frame: Read at WebSocket

• You can create a Protobuf Rule for websocket. Use Request Message Type for the client message, and Response Message Type for the server message

6. Troubleshooting

5.1 Some name fields are missing

There is a situation where some field names are absent because the field name definition is not included in your Protobuf File Descriptor. It might be that your descriptor is out of date.

Solution:

• Remove the old Protobuf Schema and add the latest descriptor file from your server.

• If you're using Proxyman 3.5.2 or older, please update to Proxyman 3.6.0 or later. Then, use File Descriptor (*.desc) for better results.