Padding Oracle Attacker : CLI Tool & Library To Execute Padding Oracle Attacks Easily

CLI tool and library to execute padding oracle attacks easily, with support for concurrent network requests and an elegant UI.


Make sure Node.js is installed, then run

$ npm install –global padding-oracle-attacker
$ yarn global add padding-oracle-attacker

CLI Usage

  $ padding-oracle-attacker decrypt <url> hex:<ciphertext_hex> <block_size> <error> [options]
  $ padding-oracle-attacker decrypt <url> b64:<ciphertext_b64> <block_size> <error> [options]

  $ padding-oracle-attacker encrypt <url> <plaintext>          <block_size> <error> [options]
  $ padding-oracle-attacker encrypt <url> hex:<plaintext_hex>  <block_size> <error> [options]

  $ padding-oracle-attacker analyze <url> [<block_size>] [options]

  decrypt                  Finds the plaintext (foobar) for given ciphertext (hex:0123abcd)
  encrypt                  Finds the ciphertext (hex:abcd1234) for given plaintext (foo=bar)
  analyze                  Helps find out if the URL is vulnerable or not, and
                           how the response differs when a decryption error occurs
                           (for the <error> argument)

  <url>                    URL to attack. Payload will be inserted at the end by default. To specify
                           a custom injection point, include {POPAYLOAD} in a header (-H),
                           request body (-d) or the URL
  <block_size>             Block size used by the encryption algorithm on the server
  <error>                  The string present in response when decryption fails on the server.
                           Specify a string present in the HTTP response body (like PaddingException)
                           or status code of the HTTP response (like 400)

  -c, --concurrency        Requests to be sent concurrently                      [default: 128]
      --disable-cache      Disable network cache. Saved to                       [default: false]
                           poattack-cache.json.gz.txt by default
  -X, --method             HTTP method to use while making request               [default: GET]
  -H, --header             Headers to be sent with request.
                             -H 'Cookie: cookie1' -H 'User-Agent: Googlebot/2.1'
  -d, --data               Request body
                             JSON string: {"id": 101, "foo": "bar"}
                             URL encoded: id=101&foo=bar
                           Make sure to specify the Content-Type header.

  -e, --payload-encoding   Ciphertext payload encoding for {POPAYLOAD}           [default: hex]
                             base64          FooBar+/=
                             base64-urlsafe  FooBar-_
                             hex             deadbeef
                             hex-uppercase   DEADBEEF
                             base64(xyz)     Custom base64 ('xyz' represent characters for '+/=')

  --dont-urlencode-payload Don't URL encode {POPAYLOAD}                          [default: false]

  --start-from-1st-block   Start processing from the first block instead         [default: false]
                           of the last (only works with decrypt mode)

  $ poattack decrypt http://localhost:2020/decrypt?ciphertext=
      16 400
  $ poattack encrypt http://localhost:2020/decrypt?ciphertext= "foo bar 🦄" 16 400
  $ poattack encrypt http://localhost:2020/decrypt?ciphertext= hex:666f6f2062617220f09fa684 16 400
  $ poattack analyze http://localhost:2020/decrypt?ciphertext=


Library API

const { decrypt, encrypt } = require(‘padding-oracle-attacker’)
// or
import { decrypt, encrypt } from ‘padding-oracle-attacker’

const { blockCount, totalSize, foundBytes, interBytes } = await decrypt(options)

const { blockCount, totalSize, foundBytes, interBytes, finalRequest } = await encrypt(options)

decrypt(options: Object): Promise
encrypt(options: Object): Promise

  • Required Options

url: string

URL to attack. Payload will be appended at the end by default. To specify a custom injection point, include {POPAYLOAD} in the URL, a header (requestOptions.headers) or the request body (

blockSize: number

Block size used by the encryption algorithm on the server.

isDecryptionSuccess: ({ statusCode, headers, body }) => boolean

Function that returns true if the server response indicates decryption was successful.

ciphertext: Buffer (decrypt only)

Ciphertext to decrypt.

plaintext: Buffer (encrypt only)

Plaintext to encrypt. Padding will be added automatically. Example: Buffer.from(‘foo bar’, ‘utf8’)

  • Optional options

concurrency: number = 128

Network requests to be sent concurrently.

isCacheEnabled: boolean = true

Responses are cached by default and saved to poattack-cache.json.gz.txt. Set to false to disable caching.

requestOptions: { method, headers, data }
requestOptions.method: string

HTTP method to use while making the request. GET by default. POST, PUT, DELETE are some valid options.

requestOptions.headers: { string: string }

Headers to be sent with request. Example: { ‘Content-Type’: ‘application/x-www-form-urlencoded’ }

requestOptions.body: string

Request body. Can be a JSON string, URL encoded params etc. Content-Type header has to be set manually.

logMode: ‘full’|’minimal’|’none’ = ‘full’

Full: Log everything to console (default)
Minimal: Log only after start and completion to console
None: Log nothing to console

transformPayload: (ciphertext: Buffer) => string

Function to convert the ciphertext into a string when making a request. By default, ciphertext is encoded in hex and inserted at the injection point (URL end unless {POPAYLOAD} is present).

  • Optional options (decrypt only)

alreadyFound: Buffer

Plaintext bytes already known/found that can be skipped (from the end). If you provide a Buffer of ten bytes, the last ten bytes will be skipped.

initFirstPayloadBlockWithOrigBytes: boolean = false

Initialize first payload block with original ciphertext bytes instead of zeroes.
Example: abcdef12345678ff 1111111111111111 instead of 00000000000000ff 1111111111111111

startFromFirstBlock: boolean = false

Start processing from the first block instead of the last.

makeInitialRequest: boolean = true

Make an initial request with the original ciphertext provided and log server response to console to allow the user to make sure network requests are being sent correctly.

  • Optional options (encrypt only)

makeFinalRequest: boolean = true

After finding the ciphertext bytes for the new plaintext, make a final request with the found bytes and log the server response to console.

lastCiphertextBlock: Buffer

Custom ciphertext for the last block. Last block is just zeroes by default (000000000000000).


padding-oracle-attacker is written in TypeScript. If you’d like to modify the source files and run them, you can either compile the files into JS first and run them using node, or use ts-node.
Example: yarn build then node dist/cli … or simply ts-node src/cli …

yarn build or npm run build

Builds the TypeScript files inside the src directory to JS files and outputs them to the dist directory.

yarn clean or npm run clean

Deletes the dist directory.

yarn lint or npm run lint

Lints the files using eslint.

yarn test or npm run test

Lints and runs the tests using ava.

node test/helpers/vulnerable-server.js

Runs the test server which is vulnerable to padding oracle attacks at http://localhost:2020