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gRPC Web Pentest Suite
gRPC-Pentest-Suite is set of tools for pentesting / hacking gRPC Web applications.
Available Content Types:
- application/grpc-web-text
- application/grpc-web+proto (See blackboxprotobuf Repo)
New Features:
- Automatically Encode/Decode by New Decoded Protobuf Tab (you can directly view the decoded protobuf in the Burp tool (Repeater, Proxy, Intruder...) AND automatically encode it back if we changed anything.)
-
Scanner Insertion Points (now if you right-click on an application/grpc-web-text HTTP request / host -> Scan -> Active Scan, Burp will manage to recognize the format, decode it, insert payloads in any field, and encode it back.)
1: { 9: 0 10: 0 19: {"test"} 25: { "#{\"\".getClass().forName(\"java.net.URL\").getConstructors()[2].newInstance(\"http:/" "/xxxx.oastify.com.\").hashCode()}" } } 10: {2: 20}
gRPC-Pentest-Suite contains these 2 tools:
- grpc-scan scanning the gRPC-web javascript webpacked files to detect grpc endpoints, services, messages and field types
- grpc-coder encoding and decoding gRPC-web payloads for pentesting (manipulating payloads)
- burp_grpc_extension_main.py extension for burp suite to easily using gRPC-Coder tool
- big-string-chunker this tool chunks a big string into pieces of 80 characters, so that gRPC-coder can encode it (also reverse)
Hacking into gRPC-Web Article & YouTube Video
This article includes the methodology for pentesting gRPC-Web and a methodology for finding hidden servies and endpoints. Read Hacking into gRPC-Web article and for application/grpc-web+proto see this article Hacking into gRPC-Web : Part 2.
This video includes using both gRPC Scan tool and gRPC Coder Burp Suite Extension: How to manipulate gRPC-Web payloads and analyse the JavaScript webpacked files to find hidden endpoints, services and messages. Watch
Requirements
pip3 install -r requirements.txt
for grpc-coder.py you need to install protoscope in system gloablly.
go install github.com/protocolbuffers/protoscope/cmd/protoscope...@latest
for gRPC Coder Burp Extension you need to have these requirements:
- download the whole repository (because the script needs grpc.coder.py)
- jython must be installed and configured in burp
- protoscope must be installed globally on system (because the extension runs a protoscope command)
- python3 must be installed to run the grpc-coder.py script (because the gRPC-Coder is written in python3)
- in windows python 3 binary name is python and in linux and mac the binary name is python3
the extension runs two safe commands to work with grpc-coder.py and protoscope tools.
gRPC Coder Extension Usage
after installing the extension it adds to menu items into extensions menu item:
- gRPC Coder Decode
- gRPC Coder Encode
Steps:
- select the gRPC-Web base64 payload in burp interceptor or repeater and click on Decode item for decoding to human-readable format
- edit the text and select the new edited text and click on Encode item for encoding to gRPC-Web base64 format
Watch the Extension Usage Video on YouTube
gRPC Coder Extension Installation
- Download the Whole Repository (the extension needs some files in this repo)
- add burp_grpc_extension_main.py in Burp Extensions.
Note: protoscope and python3 must be system globally installed.
gRPC-Coder Usage
GRPC-Coder.py has two options:
python3 grpc-coder.py --help
echo payload | python3 grpc-coder.py [--encode OR --decode]
General Arguments:
--encode encode protoscope binary output to application/grpc-web-text
--decode decode application/grpc-web-text base64 encoded payload to protoscope format
--type content-type of payload [default: grpc-web-text] available types: [grpc-web-text, grpc-web+proto]
Input Arguments:
Default Input is Standard Input
--file to get input from a file
Help:
--help print help message
Decoding
In Burp Suite when you intercept the request, get the gRPC-Web base64 encoded payload and give it to the script as standard input:
echo "AAAAABYSC0FtaW4gTmFzaXJpGDY6BVhlbm9u" | python3 grpc-coder.py --decode --type grpc-web-text | protoscope > out.txt
cat out.txt
content of out.txt:
2: {"Amin Nasiri"}
3: 54
7: {"Xenon"}
vim out.txt
... edit the file
content of edited out.txt:
cat out.txt
2: {"Amin Nasiri Xenon GRPC"}
3: 54
7: {"<script>alert(origin)</script>"}
now you have to encode the new payload: Encode
Encoding
after editing decoded payload you have to encode it:
protoscope -s out.txt | python3 grpc-coder.py --encode --type grpc-web-text
Output:
AAAAADoSFkFtaW4gTmFzaXJpIFhlbm9uIEdSUEMYNjoePHNjcmlwdD5hbGVydChvcmlnaW4pPC9zY3JpcHQ+
Then you put the new base64 payload into Burp Suite intercepted request.
Big String Chunker Tool
When you have a big string that you want to put it into a value in protobuf fields, you have to make that string into some pieces of characters using big-string-chunker.py.
For Example:
This String is big:
"T2dnUwACAAAAAAAAAABzFQAAAAAAAAAJCzcBE09wdXNIZWFkAQE4AYC7AAAAAABPZ2dTAAAAAAAAAAAAAHMVAAABAAAAo2rOoQE3T3B1c1RhZ3MPAAAAbGlib3B1cyB1bmtub3duAQAAABQAAABFTkNPREVSPU1vemlsbGExMjQuME9nZ1MAAMAwAAAAAAAAcxUAAAIAAAD1DNygG//T/yb/KP//CP8h/yT/JP8k/yX/JP8l/yj/Kfh4/5AiWRn+hxCNu1lGW1E1RpFlgncP1g3KdvtuuhDanwxtyvMzTX/X3ain7fAXGnRupDzl9oir"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"
the tool converts it to this:
1: {
"T2dnUwACAAAAAAAAAABzFQAAAAAAAAAJCzcBE09wdXNIZWFkAQE4AYC7AAAAAABPZ2dTAAAAAAAAAAAA"
"AHMVAAABAAAAo2rOoQE3T3B1c1RhZ3MPAAAAbGlib3B1cyB1bmtub3duAQAAABQAAABFTkNPREVSPU1v"
"emlsbGExMjQuME9nZ1MAAMAwAAAAAAAAcxUAAAIAAAD1DNygG//T/yb/KP//CP8h/yT/JP8k/yX/JP8l"
"/yj/Kfh4/5AiWRn+hxCNu1lGW1E1RpFlgncP1g3KdvtuuhDanwxtyvMzTX/X3ain7fAXGnRupDzl9oir"
"jHtN7BZBGZZW9Vkyv2oBhgfnGhJPxrf7RJ9D4e2AABS0iAuHWWWzs0UZpgwlqMwOZ+w4PIymRYPzCB5q"
"9C9JFVUjdihmqLbP8WICC+0eSFmUO+lM4PYiVprOWgfbwTcNqaYdZSKT3fp2pjNuTJzyvEO/t2Dg1TnC"
"wjoq0veEM1YcRx4polaFw/au+FdceT13SuK8ehmSEHPyLB1H2lUAAAAAAAAAAaBfGjYa5md8lEWEol5m"
"ykby0OgcohE0KzMpefR9SiVHFG7sL0r7JrAeot6SRV1x1iWWVBejRscEDQA0gyXKQnrH1P+/cIqNOLFZ"
.
.
.
"zHVfcTfCbDASrlauLF5i9eLUEFv289im/BQqPPGkld7iwBlOA5zZz4ysnRYDv8VytH9F9vLqNgpiWqNO"
"0pgr+4Dl9i4vtxgCYAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEEH5ttS9etaTCa18br69R/R"
"M6tCIKjxjEULqgaJJQkCBwJxDR9kAsol/Xymr7cFKgJ+0crArSf9IqQ/WgqEAgEtYmTqgwA0BkOTT4q2"
"YhAygIak+pZZu654kaBYG+9Hag=="
}
- Note: Do not forget to change the field number. The tool uses field number 1 by default.
Big String Chunker in gRPC Coder Burp Extension [Chunk]
- Big String
- Result
Big String Chunker CLI Usage [Chunk]
cat bigString.txt | python3 big-string-chunker.py --stdin --chunk
python3 big-string-chunker.py --file bigString.txt --chunk
Big String Chunker in gRPC Coder Burp Extension [Un-Chunk]
- Big String
- Result:
Big String Chunker CLI Usage [Un-Chunk]
cat chunkedString.txt | python3 big-string-chunker.py --stdin --un-chunk
python3 chunkedString.py --file bigString.txt --un-chunk
gRPC-Scan Usage
python3 grpc-scan.py --file main.js
OR
cat main.js | python3 grpc-scan.py --stdin
gRPC-Scan Javascript Files Note
For saving javascript files, you have to open them in browser and save the file or download it directly.
Do not copy and paste the javascript content.
ProtoBuf Version Support:
- Version 3 [OK]
- Version 2 [Some Features do not work]
gRPC-Scan Help
python3 grpc-scan.py --help
python3 grpc-scan.py [INPUT]
Input Arguments:
--file file name of js file
--stdin get input from standard input
Help:
--help print help message
gRPC-Scan Output Example
python3 grpc-scan.py --file main.js
Found Endpoints:
/grpc.gateway.testing.EchoService/Echo
/grpc.gateway.testing.EchoService/EchoAbort
/grpc.gateway.testing.EchoService/NoOp
/grpc.gateway.testing.EchoService/ServerStreamingEcho
/grpc.gateway.testing.EchoService/ServerStreamingEchoAbort
Found Messages:
grpc.gateway.testing.EchoRequest:
+------------+--------------------+--------------+
| Field Name | Field Type | Field Number |
+============+====================+==============+
| Message | Proto3StringField | 1 |
+------------+--------------------+--------------+
| Name | Proto3StringField | 2 |
+------------+--------------------+--------------+
| Age | Proto3IntField | 3 |
+------------+--------------------+--------------+
| IsAdmin | Proto3BooleanField | 4 |
+------------+--------------------+--------------+
| Weight | Proto3FloatField | 5 |
+------------+--------------------+--------------+
| Test | Proto3StringField | 6 |
+------------+--------------------+--------------+
| Test2 | Proto3StringField | 7 |
+------------+--------------------+--------------+
| Test3 | Proto3StringField | 16 |
+------------+--------------------+--------------+
| Test4 | Proto3StringField | 20 |
+------------+--------------------+--------------+
grpc.gateway.testing.EchoResponse:
+--------------+--------------------+--------------+
| Field Name | Field Type | Field Number |
+==============+====================+==============+
| Message | Proto3StringField | 1 |
+--------------+--------------------+--------------+
| Name | Proto3StringField | 2 |
+--------------+--------------------+--------------+
| Age | Proto3IntField | 3 |
+--------------+--------------------+--------------+
| IsAdmin | Proto3BooleanField | 4 |
+--------------+--------------------+--------------+
| Weight | Proto3FloatField | 5 |
+--------------+--------------------+--------------+
| Test | Proto3StringField | 6 |
+--------------+--------------------+--------------+
| Test2 | Proto3StringField | 7 |
+--------------+--------------------+--------------+
| Test3 | Proto3StringField | 16 |
+--------------+--------------------+--------------+
| Test4 | Proto3StringField | 20 |
+--------------+--------------------+--------------+
| MessageCount | Proto3IntField | 8 |
+--------------+--------------------+--------------+
grpc.gateway.testing.ServerStreamingEchoRequest:
+-----------------+-------------------+--------------+
| Field Name | Field Type | Field Number |
+=================+===================+==============+
| Message | Proto3StringField | 1 |
+-----------------+-------------------+--------------+
| MessageCount | Proto3IntField | 2 |
+-----------------+-------------------+--------------+
| MessageInterval | Proto3IntField | 3 |
+-----------------+-------------------+--------------+
grpc.gateway.testing.ServerStreamingEchoResponse:
+------------+-------------------+--------------+
| Field Name | Field Type | Field Number |
+============+===================+==============+
| Message | Proto3StringField | 1 |
+------------+-------------------+--------------+
grpc.gateway.testing.ClientStreamingEchoRequest:
+------------+-------------------+--------------+
| Field Name | Field Type | Field Number |
+============+===================+==============+
| Message | Proto3StringField | 1 |
+------------+-------------------+--------------+
grpc.gateway.testing.ClientStreamingEchoResponse:
+--------------+----------------+--------------+
| Field Name | Field Type | Field Number |
+==============+================+==============+
| MessageCount | Proto3IntField | 1 |
+--------------+----------------+--------------+
gRPC Lab
For testing this tool and getting familiar with gRPC-Web, I made a lab for gRPC & gRPC-Web.